pyrophosphate and Calcinosis

Pathologic soft tissue calcification can occur in both genetic and acquired clinical conditions, causing significant morbidity and mortality. Although the pathomechanisms of pathologic calcification are poorly understood, major progress has been made in recent years in defining the underlying genetic defects in Mendelian disorders of ectopic calcification. This review presents an overview of the pathophysiology of five monogenic disorders of pathologic calcification: pseudoxanthoma elasticum, generalized arterial calcification of infancy, arterial calcification due to deficiency of CD73, ankylosis, and progeria. These hereditary disorders, caused by mutations in genes encoding ATP binding cassette subfamily C member 6, ectonucleotide pyrophosphatase/phosphodiesterase 1, CD73, progressive ankylosis protein, and lamin A/C proteins, respectively, are inorganic pyrophosphate (PPi) deficiency syndromes with reduced circulating levels of PPi, the principal physiologic inhibitor of calcium hydroxyapatite deposition in soft connective tissues. In addition to genetic diseases, PPi deficiency has been encountered in acquired clinical conditions accompanied by pathologic calcification. Because specific and effective treatments are lacking for pathologic calcification, the unifying finding of PPi deficiency suggests that PPi-targeted therapies may be beneficial to counteract pathologic soft tissue calcification in both genetic and acquired diseases.

Topics: Ankylosis; Calcinosis; Choristoma; Diphosphates; Humans; Pseudoxanthoma Elasticum; Syndrome; Vascular Calcification

The aim of this study was to provide updated information on the prevalence, pathogenesis, diagnostics and therapeutics of calcinosis cutis associated with systemic sclerosis (SSc).. Observational studies show ethnic and geographical differences in the prevalence of calcinosis. In addition to clinical and serological associations, biochemical studies and in-vivo models have attempted to explain theories behind its pathogenesis, including prolonged state of inflammation, mechanical stress, hypoxia and dysregulation in bone and phosphate metabolism. Long-term use of proton pump inhibitors may increase the risk for calcinosis in SSc. Few single-centre observational studies have shown mild benefit with minocycline and topical sodium thiosulfate.. Calcinosis cutis is the deposition of insoluble calcium in the skin and subcutaneous tissues. It affects up to 40% of SSc patients and causes significant morbidity. Long disease duration, features of vascular dysfunction and osteoporosis have been associated with calcinosis. Altered levels of inorganic pyrophosphate and fibroblast growth factor-23 have been implicated in dysregulated phosphate metabolism that may lead to calcinosis in SSc. Plain radiography can help with diagnosis and quantifying the calcinosis burden. Surgical treatment remains the most effective therapy when feasible. At present, no medical therapies have proven efficacy in large randomized controlled trials.

Topics: Calcinosis; Calcium; Diphosphates; Humans; Minocycline; Proton Pump Inhibitors; Scleroderma, Systemic

Pathological (ectopic) mineralization of soft tissues occurs during aging, in several common conditions such as diabetes, hypercholesterolemia, and renal failure and in certain genetic disorders. Pseudoxanthoma elasticum (PXE), a multi-organ disease affecting dermal, ocular, and cardiovascular tissues, is a model for ectopic mineralization disorders. ABCC6 dysfunction is the primary cause of PXE, but also some cases of generalized arterial calcification of infancy (GACI). ABCC6 deficiency in mice underlies an inducible dystrophic cardiac calcification phenotype (DCC). These calcification diseases are part of a spectrum of mineralization disorders that also includes Calcification of Joints and Arteries (CALJA). Since the identification of ABCC6 as the "PXE gene" and the development of several animal models (mice, rat, and zebrafish), there has been significant progress in our understanding of the molecular genetics, the clinical phenotypes, and pathogenesis of these diseases, which share similarities with more common conditions with abnormal calcification. ABCC6 facilitates the cellular efflux of ATP, which is rapidly converted into inorganic pyrophosphate (PPi) and adenosine by the ectonucleotidases NPP1 and CD73 (NT5E). PPi is a potent endogenous inhibitor of calcification, whereas adenosine indirectly contributes to calcification inhibition by suppressing the synthesis of tissue non-specific alkaline phosphatase (TNAP). At present, therapies only exist to alleviate symptoms for both PXE and GACI; however, extensive studies have resulted in several novel approaches to treating PXE and GACI. This review seeks to summarize the role of ABCC6 in ectopic calcification in PXE and other calcification disorders, and discuss therapeutic strategies targeting various proteins in the pathway (ABCC6, NPP1, and TNAP) and direct inhibition of calcification via supplementation by various compounds.

Topics: 5'-Nucleotidase; Animals; ATP-Binding Cassette Transporters; Calcification, Physiologic; Calcinosis; Diphosphates; GPI-Linked Proteins; Humans; Joint Diseases; Mice; Multidrug Resistance-Associated Proteins; Phosphoric Diester Hydrolases; Pseudoxanthoma Elasticum; Pyrophosphatases; Rats; Vascular Calcification; Vascular Diseases

This review summarizes current understanding of generalized arterial calcification of infancy (GACI), emphasizing pathophysiology, clinical presentation, and approaches and controversies in management.. Identification of causative ENPP1 mutations revealed that GACI arises from deficiencies in inorganic pyrophosphate (leading to calcifications) and adenosine monophosphate (leading to intimal proliferation). Identification of genotypic and phenotypic overlap with pseudoxanthoma elasticum and autosomal recessive hypophosphatemic rickets further advanced understanding of GACI as a complex, multisystemic disease. Clinical data is limited to small, retrospective samples; it is therefore unknown whether commonly used medications, such as bisphosphonates and hypophosphatemia treatment, are therapeutic or potentially harmful. ENPP1-Fc replacement represents a promising approach warranting further study. Knowledge gaps in natural history place clinicians at high risk of assigning causality to interventions that are correlated with changes in clinical status. There is thus a critical need for improved natural history studies to develop and test targeted therapies.

Topics: Adenosine Monophosphate; Bone Density Conservation Agents; Calcinosis; Cardiovascular Agents; Chelating Agents; Diphosphates; Diphosphonates; Familial Hypophosphatemic Rickets; Genotype; Hearing Loss; Humans; Multidrug Resistance-Associated Proteins; Phenotype; Phosphoric Diester Hydrolases; Pseudoxanthoma Elasticum; Pyrophosphatases; Thiosulfates; Tooth Diseases; Vascular Calcification; Vitamin D

In the progression of osteoarthritis, pathological calcification in the affected joint is an important feature. The role of these crystallites in the pathogenesis and progression of osteoarthritis is controversial; it remains unclear whether they act as a disease initiator or are present as a result of joint damage. Recent studies reported that the molecular mechanisms regulating physiological calcification of skeletal tissues are similar to those regulating pathological or ectopic calcification of soft tissues. Pathological calcification takes place when the equilibrium is disrupted. Calcium phosphate crystallites are identified in most affected joints and the presence of these crystallites is closely correlated with the extent of joint destruction. These observations suggest that pathological calcification is most likely to be a disease initiator instead of an outcome of osteoarthritis progression. Inhibiting pathological crystallite deposition within joint tissues therefore represents a potential therapeutic target in the management of osteoarthritis.

Topics: Apoptosis; Bursa, Synovial; Calcinosis; Calcium; Cartilage; Chondrocytes; Collagen; Diphosphates; Extracellular Matrix; Extracellular Vesicles; Humans; Meniscus; Mitochondria; Osteoarthritis; Phosphates; Proteoglycans; Pyrophosphatases; Severity of Illness Index

We give an update on the etiology and potential treatment options of rare inherited monogenic disorders associated with arterial calcification and calcific cardiac valve disease.. Genetic studies of rare inherited syndromes have identified key regulators of ectopic calcification. Based on the pathogenic principles causing the diseases, these can be classified into three groups: (1) disorders of an increased extracellular inorganic phosphate/inorganic pyrophosphate ratio (generalized arterial calcification of infancy, pseudoxanthoma elasticum, arterial calcification and distal joint calcification, progeria, idiopathic basal ganglia calcification, and hyperphosphatemic familial tumoral calcinosis; (2) interferonopathies (Singleton-Merten syndrome); and (3) others, including Keutel syndrome and Gaucher disease type IIIC. Although some of the identified causative mechanisms are not easy to target for treatment, it has become clear that a disturbed serum phosphate/pyrophosphate ratio is a major force triggering arterial and cardiac valve calcification. Further studies will focus on targeting the phosphate/pyrophosphate ratio to effectively prevent and treat these calcific disease phenotypes.

Topics: Abnormalities, Multiple; Aortic Diseases; Basal Ganglia Diseases; Calcinosis; Cartilage Diseases; Dental Enamel Hypoplasia; Diphosphates; Enzyme Replacement Therapy; Gaucher Disease; Hand Deformities, Congenital; Humans; Hyperostosis, Cortical, Congenital; Hyperphosphatemia; Interferons; Metacarpus; Muscular Diseases; Odontodysplasia; Osteoporosis; Phosphates; Progeria; Pseudoxanthoma Elasticum; Pulmonary Valve Stenosis; Vascular Calcification

Inorganic pyrophosphate has long been known as a by-product of many intracellular biosynthetic reactions, and was first identified as a key endogenous inhibitor of biomineralisation in the 1960s. The major source of pyrophosphate appears to be extracellular ATP, which is released from cells in a controlled manner. Once released, ATP can be rapidly hydrolysed by ecto-nucleotide pyrophosphatase/phosphodiesterases to produce pyrophosphate. The main action of pyrophosphate is to directly inhibit hydroxyapatite formation thereby acting as a physiological 'water-softener'. Evidence suggests pyrophosphate may also act as a signalling molecule to influence gene expression and regulate its own production and breakdown. This review will summarise our current understanding of pyrophosphate metabolism and how it regulates bone mineralisation and prevents harmful soft tissue calcification.

Topics: Adenosine Triphosphate; Animals; Calcification, Physiologic; Calcinosis; Diphosphates; Gene Expression Regulation; Humans; Phosphoric Diester Hydrolases; Pyrophosphatases; Signal Transduction

Vascular calcification is an independent risk factor for the development of cardiovascular disease and is classified into two types based on the site of calcification : intimal atherosclerotic calcification and Mönckeberg's medial calcification. Matrix vesicles released from macrophages and vascular smooth muscle cells (VSMC) during apoptosis play a pivotal role in formation of fine granular calcification, while osteogenic differentiation of VSMC contributes to progression of advanced calcification. Recent noninvasive imaging studies of atherosclerotic calcification provide robust evidence that inflammation precedes active calcification, leading to establish the inflammation-dependent calcification paradigm. On the other hand, elastin degradation by increased elastolytic activities and disturbance of regulatory systems of extracellular pyrophosphate metabolism play an important role in development of Mönckeberg's medial calcification.

Topics: Animals; Apoptosis; Calcinosis; Cardiovascular Diseases; Cellular Senescence; Diphosphates; Elastin; Extracellular Matrix; Humans; Macrophages; Mice; Muscle, Smooth, Vascular; Osteogenesis; Risk Factors; Vascular Calcification

Pyrophosphate (PPi) is well known as a regulator of calcification, and the ANKH (ANK in mouse) protein has a role in the membrane transport of PPi. Earlier work concentrated on bones and joints, but ANKH is also likely to have important roles in the kidney, with newer studies focusing on vascular calcification in renal failure. Renal calcification can occur due to a naturally occurring ANK mouse mutation, yet other ANK mutations do not cause a renal phenotype. Despite evidence over 10 years of ANKH's involvement in PPi transport, efflux of PPi via ANKH has never been demonstrated. Rather than physically moving PPi, the ANKH protein may assist its membrane transport in other ways such as by hydrolysis and compartmentalisation. Protein complexes may account for effects of ANKH that are specific to particular tissues. In the kidney, recent localisation data may be helpful in suggesting physiological roles for ANKH, such as its co-localisation with aquaporin-2 and cilial proteins. Such diverse functions would reflect the ubiquitous nature of ANKH in tissues and its profound evolutionary conservation.

Topics: Animals; Aquaporin 2; Calcinosis; Cilia; Diphosphates; Humans; Kidney; Membrane Transport Proteins; Mice; Mutation; Nephrocalcinosis; Organ Specificity; Phosphate Transport Proteins; Renal Insufficiency

ttw (tiptoe walking), a known model mouse of OPLL (ossification of the posterior longitudinal ligament of the spine) is reviewed. ttw is a natural mutant which shows generalized ectopic calcification followed by ossification in the Achiles tendon, ear and spinal ligaments, etc. The trait is caused by a homozygous nonsense mutation in the gene for NPPS (nucleotide pyrophosphatase) , a cell-membrane enzyme that produces pyrophosphate. Its pathomechanism is the decrease of extracellular pyrophosphate due to insufficiency of NPPS. ttw is a excellent model for ectopic calcification and ossification. Several interesting genes related to ectopic calicification have been identified by studies using this mouse.

Topics: Animals; Calcinosis; Codon, Nonsense; Diphosphates; Disease Models, Animal; Genes, Recessive; Mice; Mice, Mutant Strains; Ossification of Posterior Longitudinal Ligament; Pyrophosphatases

Mineralization imparts important biomechanical and other functional properties to bones and teeth. Ectopic pathologic mineralization, however, occurring in soft tissues such as blood vessels, kidneys, articular cartilage and also in body fluids, including urine and synovial fluid, is generally debilitating, often painful and typically is destructive of compromised tissue. Here we review new findings on direct molecular determinants of mineralization operating locally at the level of the extracellular matrix, with a focus on bone and blood vessels.. Accumulating evidence indicates important key roles for secreted noncollagenous proteins in regulating mineralization, wherein they also contribute structurally to the scaffolding properties of the extracellular matrix. Mineral-binding proteins contain conserved acidic peptide domains (often highly phosphorylated), which bind strongly to calcium within the apatitic mineral phase of bone and calcified blood vessels to regulate crystal growth. Other recent work has underscored the importance of the small-molecule mineralization inhibitor pyrophosphate in inhibiting tissue mineralization - an inhibition released through its enzymatic cleavage by tissue-nonspecific alkaline phosphatase. Recent findings on mechanisms involved in matrix vesicle-mediated mineralization are also discussed.. Mechanistic details are emerging that describe a scenario wherein the combined actions of mineral-binding noncollagenous matrix peptides/proteins within a scaffolding of collagen (and also elastin in blood vessels), phosphatases and matrix vesicles all contribute importantly to promoting or limiting mineralization.

Topics: Animals; Blood Vessels; Calcification, Physiologic; Calcinosis; Diphosphates; Extracellular Matrix; Extracellular Matrix Proteins; Humans; Phosphates; Vascular Diseases

Patients with chronic kidney disease have increased cardiovascular mortality from a combination of increased atherosclerotic disease, left ventricular hypertrophy and increased prevalence of vascular calcification (VC). Previously VC was thought to be a passive process which involved the deposition of calcium and phosphate into the vessel wall. However, recent studies have shown that VC is a highly regulated, cell-mediated process similar to bone formation, in that it is associated with expression of bone-related proteins, such as type I collagen and alkaline phosphatase. Animal and in vitro models of VC have shown that a multitude of factors including phosphate, matrix gla protein (MGP) and fetuin are involved in regulating VC. Certain factors induce calcification whereas others inhibit the process. Despite these insights, it is still not fully known how VC is regulated and a treatment for VC remains elusive. Ongoing research will hopefully elucidate these mechanisms and thereby produce targets for future therapeutic intervention. This review will highlight some of the scientific models of VC and how they have increased the understanding of this complex process.

Topics: Alkaline Phosphatase; alpha-Fetoproteins; Animals; Apoptosis; Atherosclerosis; Calcinosis; Calcium-Binding Proteins; Cardiovascular Diseases; Collagen Type I; Diphosphates; Disease Models, Animal; Extracellular Matrix Proteins; Humans; Hypertrophy, Left Ventricular; Inflammation; Kidney Failure, Chronic; Matrix Gla Protein; Mice; Osteopontin; Phosphorus; Prevalence; Risk Factors; Vascular Diseases; Vitamin D; Vitamins

In the last decade, the nephrology community has focused its attention on the main cause of morbidity and mortality in chronic renal failure patients: cardiovascular disease. In addition, recent studies pointed out that vascular calcification (VC) is a major cause of cardiovascular disease in the dialysis population. Interestingly, the pathogenesis of VC and soft tissue calcification in chronic kidney disease (CKD) has been extensively investigated. Nowadays we know that VC is associated not only with passive calcium phosphate deposition, but also with an active, cell-mediated process. To better understand the pathogenesis of VC in CKD, numerous regulatory proteins have been studied, because of their ability to inhibit mineral deposition in the vessels. We here examine the state of the art of those substances recognized as regulatory key factors in preventing VC in uremic conditions, such as fetuin A (alpha2-Heremans-Schmid glycoprotein), matrix gamma-carboxyglutamic acid protein, pyrophosphate, osteoprotegerin and bone morphogenetic protein. We conclude that at present it is too early to introduce these novel markers into clinical practice.

Topics: 1-Carboxyglutamic Acid; alpha-Fetoproteins; Bone Morphogenetic Protein 7; Bone Morphogenetic Proteins; Calcinosis; Diphosphates; Humans; Kidney Failure, Chronic; Models, Biological; Osteoprotegerin; Risk Factors; Transforming Growth Factor beta; Uremia; Vascular Diseases

The cardiovascular risk of patients undergoing dialysis is 20-30 times higher than that of individuals of the same age, without abnormal renal function, from the general population. Observational studies of patients with normal and abnormal renal function have shown that there is an association between bone disease, vascular calcification and cardiovascular outcome and that worsening of these conditions happens in parallel. Basic science studies are elucidating several mechanisms that could explain the interaction between bone disease, vascular calcification and cardiovascular outcome. For example, the expression of osteoprotegerin-a protein that regulates bone resorption by binding receptor activator of nuclear factor kappaB (RANK) ligand (RANKL), thus preventing interaction with the receptor RANK and the stimulation of osteoclast maturation-is regulated by several cytokines. Additionally, osteoprotegerin seems involved in the genesis of atherosclerosis. Imbalances of bone mineral metabolism, bone matrix secretion and vascular smooth-muscle-cell apoptosis seem involved in the ossification of the arterial wall in chronic kidney disease, and could explain some of the complex interactions between bone and vascular disease in renal failure. In this article we present a brief review of some of the basic mechanisms involved in vascular calcification and the clinical evidence of an association of vascular and bone disease.

Topics: Aged; alpha-2-HS-Glycoprotein; Blood Proteins; Bone and Bones; Bone Diseases; Calcinosis; Calcium; Calcium-Binding Proteins; Diphosphates; Extracellular Matrix Proteins; Female; Humans; Male; Matrix Gla Protein; Middle Aged; Osteoporosis; Phosphates; Practice Guidelines as Topic; Renal Dialysis; Renal Insufficiency, Chronic; Risk Factors; Vascular Diseases

Among the myriad of players in the calcification of cartilage, ANK is a relatively new entrant. It is a multipass transmembrane protein that regulates the transport of inorganic pyrophosphate between the cell and the extracellular space. Mutations in ANK result in two distinct calcification disorders: craniometaphyseal dysplasia and familial calcium pyrophosphate dihydrate deposition disease. The purpose of this review is to highlight recent work on the role of ANK in physiological and pathological calcification of articular and growth plate cartilage.. New information on the function of ANK suggests that the protein is part of a constellation of critical components that interact to regulate the elaboration of inorganic pyrophosphate. In addition to ANK, these components include alkaline phosphatase, the ectoenzyme PC-1, and osteopontin. ANK expression is also regulated by a variety of growth factors and cytokines that may further affect the transport of inorganic pyrophosphate and may be particularly relevant to the increased levels of expression of ANK in cartilage from chondrocalcinosis and osteoarthritis patients.. Additional studies will be required to understand the contribution of ANK in shaping the fine balance of components necessary for crystal deposition in degenerating articular cartilage. Furthermore, the precise role of inherited mutations in ANK on the elaboration of inorganic pyrophosphate, and the ultimate deposition of either basic calcium phosphate or calcium pyrophosphate dihydrate crystals, remains unclear.

Topics: Calcinosis; Calcium Phosphates; Calcium Pyrophosphate; Cartilage, Articular; Diphosphates; Genetic Predisposition to Disease; Growth Plate; Humans; Mutation; Phosphate Transport Proteins

Idiopathic infantile arterial calcification (IIAC) is a rare, but important, cause of rapidly progressive ischemic heart disease in children. In this paper, we report two recent cases of IIAC seen at tertiary referral hospitals. Both cases presented in infancy with signs of heart failure and, ultimately, died with the diagnosis of IIAC confirmed at postmortem examination. A thorough review of the literature reveals approximately 160 reported cases of IIAC. The clinical outcomes, radiographic findings and pathologic details are summarized. Proposed etiologic mechanisms are reviewed, including promising research into the role of inorganic pyrophosphate as a regulatory factor in the development of IIAC. Because of the typically fatal outcome of IIAC and the lack of proven therapies, the potential role for cardiac transplantation is discussed.

Topics: Arteries; Basement Membrane; Calcinosis; Cardiomyopathies; Coronary Vessels; Diphosphates; Disease Progression; Fatal Outcome; Female; Heart Transplantation; Humans; Infant; Myocardial Ischemia; Myocardium; Tunica Intima; Vascular Diseases

Topics: Animals; Blood Vessels; Calcinosis; Diphosphates; Humans; Muscle, Smooth, Vascular; Paracrine Communication; Phenotype

Cardiovascular disease is the leading cause of death in patients with chronic kidney disease. A growing body of data points to nontraditional risk factors, including disturbances in mineral metabolism, as important determinants of the extremely high cardiovascular morbidity and mortality rates in these patients. Disturbances in mineral metabolism, especially elevated calcium and phosphate levels, have been linked to vascular and valvular calcification, both of which are associated with poor prognosis in chronic kidney disease patients. This review highlights important recent findings regarding the etiology of vascular calcification, with special emphasis on pathways that may be particularly relevant in chronic kidney disease patients.. New studies indicate that not only vascular intimal calcification (associated with atherosclerosis) but also vascular medial calcification are correlated with decreased survival in chronic kidney disease patients. With the relatively recent recognition of vascular calcification as an actively regulated process, a growing list of inducers (calcium, phosphate, inflammatory cytokines) and inhibitors (matrix Gla protein, fetuin, pyrophosphate, osteopontin) have been discovered. Interesting recent evidence suggests that they may contribute to the prevalence of this pathology in chronic kidney disease patients.. Vascular calcification is associated with decreased survival in chronic kidney disease patients. Understanding the causes and regulatory factors controlling vascular calcification will help refine therapeutic modalities currently in use, as well as develop novel therapeutics to abate and potentially reverse this deleterious process.

Topics: alpha-2-HS-Glycoprotein; Animals; Arteriosclerosis; Blood Proteins; Calcinosis; Calcium Phosphates; Diphosphates; Humans; Osteopontin; Sialoglycoproteins; Uremia; Vascular Diseases

Recent progress in genetics and mouse genomics enables researchers to unveil the molecular basis for mouse phenotypes that express pathologic calcification in soft tissue and/or articular tissues. A newly identified multipass transmembrane protein, ANK, appears to function as an inorganic pyrophosphate (PPi) transporter or regulator of PPi transport. Abnormal extracellular PPi (ePPi) metabolism has been implicated in abnormal calcification, decreased concentrations predisposing to basic calcium phosphate (BCP) deposition, and increased concentrations promoting calcium pyrophosphate dihydrate (CPPD) crystal deposition in articular tissues. The chromosomal location of human ANK overlaps the locus identified in several kindreds affected with familial chondrocalcinosis. Deficient generation of ePPi by the ectoenzyme nucleoside triphosphate pyrophosphohydrolase also results in excessive ossification and ectopic deposition of BCP crystals in tiptoe-walking mice and PC-1 null mice. Recent studies reinforce the important regulatory role of ePPi in pathologic and physiologic calcification.

Topics: Animals; Calcinosis; Diphosphates; Disease Models, Animal; Homeostasis; Humans; Membrane Proteins; Mice; Mice, Knockout; Mice, Transgenic; Phosphate Transport Proteins; Pyrophosphatases; Transforming Growth Factor beta

Inorganic pyrophosphate (PP(i)) regulates certain intracellular functions and extracellular crystal deposition. PP(i) is produced, degraded, and transported by specialized mechanisms. Moreover, dysregulated cellular PP(i) production, degradation, and transport all have been associated with disease, and PP(i) appears to directly mediate specific disease manifestations. In addition, natural and synthetic analogs of PP(i) are in use or currently under evaluation as prophylactic agents or therapies for disease. This review summarizes recent developments in the understanding of how PP(i) is made and disposed of by cells and assesses the body of evidence for potentially significant physiological functions of intracellular PP(i) in higher organisms. Major topics addressed are recent lines of molecular evidence that directly link decreased and increased extracellular PP(i) levels with diseases in which connective tissue matrix calcification is disordered. To illustrate in depth the effects of disordered PP(i) metabolism, this review weighs the roles in matrix calcification of the transmembrane protein ANK, which regulates intracellular to extracellular movement of PP(i), and the PP(i)-generating phosphodiesterase nucleotide pyrophosphatase family isoenzyme plasma cell membrane glycoprotein-1 (PC-1).

Topics: Animals; Calcification, Physiologic; Calcinosis; Connective Tissue Cells; Diphosphates; Humans; Membrane Glycoproteins; Membrane Proteins; Molecular Structure; Phosphate Transport Proteins; Phosphoric Diester Hydrolases; Pyrophosphatases

The chemistry and molecular bonding characteristics of the CaPPi family of compounds are very complex. The unique molecular flexibility of the PPi anion and the potential variability of Ca coordination geometries have allowed for a broad spectrum of CaPPi type structures. The structure of t-CPPD has the smallest P-OB-P angle of the known CaPPi structures, both Ca atoms are 7 coordinate which is the maximum allowable contacts for Ca atoms, and the two water molecules of crystallization not only serve to fill molecular space, but they are also involved in direct contact to the PPi anions and the Ca atoms. The structure of t-CPPD appears to be very stable and the structural characteristics support the observation that the crystals are sparingly soluble in an aqueous environment. Unfortunately, the structure of m-CPPD is not known and comparisons cannot be made. The solution model studies have resulted in the observation that t-CPPD and m-CPPD crystals can be grown in an aqueous environment at conditions far less harsh than those required for the standard synthetic procedure. However, the synthetic procedure, in contrast to the solution models, yields the prismatic crystal growth morphology of t-CPPD and the rod morphology of m-CPPD observed in vivo. The solution models showed that increasing Mg or Pi retarded crystal formation. At physiologic levels of Mg and Pi, a-CaPPi formed, but neither t-CPPD nor m-CPPD would form. In all solution studies, the final Ca and PPi were not determined and therefore a correlation could not be made between the ionic concentrations and crystal type formed. The gel models using silica, polyacrylamide, and biologic grade gelatin all highlighted that the time of incubation of Ca and PPi ions was a critical parameter in determining the type of crystal formed. The biologic grade gelatin model studies that we conducted indicated that the formation of the two in vivo crystals was mediated by the formation of intermediate crystalline materials and the subsequent dissolution of those species. This formation/dissolution/reformation mechanism allows for a very localized ionic concentrating process to occur. In our model system, we measured the final Ca and PPi levels at all points of crystallization and could map the ionic concentration gradients and compare them to the crystal type formed with respect to the time of incubation. However, the crystal growth morphologies for t-CPPD and m-CPPD still did not match the morphologies observed in

Topics: Anions; Calcinosis; Calcium Pyrophosphate; Chemical Phenomena; Chemistry, Physical; Collagen; Crystallization; Crystallography; Diphosphates; Gels; Humans; Joint Diseases; Models, Biological; Models, Chemical

CPPD deposition occurs in a wide variety of clinical settings, most commonly as an age-related phenomenon in the absence of other joint abnormality. Although our knowledge of CPPD and other intra-articular particles has increased in the last decade, the role of CPPD remains unclear. The paradox of asymptomatic deposition of phlogistic crystals, the wide spectrum of clinical presentation, and the lack of disease specificity, however, have challenged recognition of pyrophosphate arthropathy (PA) as a separate, distinct disease entity and led to reappraisal of earlier concepts of crystal deposition disease. In this article, clinical aspects of PA will first be presented; the validity of PA as a discrete arthropathy will then be discussed.

Topics: Arthritis; Calcinosis; Calcium Pyrophosphate; Chondrocalcinosis; Crystallization; Diphosphates; Humans; Joint Diseases

Topics: Adsorption; Calcification, Physiologic; Calcinosis; Calcium; Crystallization; Diphosphates; Humans; Hydroxides; Hydroxyapatites; Ions

The history of diphosphonates began with studies of inorganic pyrophosphate. This compound was found to occur in many biological fluids and inhibited the precipitation of calcium phosphates. It also slowed the transformation of amorphous calcium phosphate to its crystalline form, and inhibited crystal aggregation and dissolution. These observations suggested that it might be a compound of physiological or pathophysiological significance, perhaps in hypophosphatasia and in renal lithiasis. Diphosphonates are compounds where the P-O-P bond of pyrophosphate is replaced by a P-C-P bond. Many diphosphonates have been synthesized and tested and some relationship of their structure to the spectrum of biological effects has been observed. These analogues have similar properties to pyrophosphate, but unlike pyrophosphate they are resistant to enzymic degradation. Their experimental properties have led to their clinical development as bone scanning agents and in the treatment of disorders of ectopic mineralization and increased bone resorption.

Topics: Animals; Bone Resorption; Calcification, Physiologic; Calcinosis; Calcium Phosphates; Clodronic Acid; Diphosphates; Diphosphonates; Etidronic Acid; Humans; Methylene Chloride; Polyphosphates

Topics: Animals; Bone and Bones; Brain Neoplasms; Calcification, Physiologic; Calcinosis; Calcium Phosphates; Collagen; Diphosphates; Diphosphonates; Humans; Hydroxyapatites; Mice; Microscopy, Electron; Mitochondria; Odontogenic Tumors; Phospholipids; Pinealoma

Topics: Animals; Bone and Bones; Calcinosis; Diphosphates; Humans; Lung; Phosphates; Uremia

Topics: Bone Resorption; Calcification, Physiologic; Calcinosis; Calcium; Calcium Phosphates; Chemical Precipitation; Dental Calculus; Dihydroxycholecalciferols; Diphosphates; Diphosphonates; Humans; Osteitis Deformans; Osteoporosis; Phosphates; Phosphoric Monoester Hydrolases; Radionuclide Imaging; Structure-Activity Relationship

Pyrophosphate and diphosphonates produce striking results on calcium metabolism in experimental animals and man. Compounds containing P-O-P- bonds (e.g. inorganic pyrophosphate [PP-ii1 or P-C-P bonds (diphosponates) inhibit both the formation and dissolution of calcium phosphate crystals in vitro. PP-i may have a physiological function in regulating calcification and bone turnover, and obnormalities in its metabolism may occur in some human diseases notably hypophosphatasia and pseudogout. Diphosphonates inhibit ectopic calcification, and slow down resorption and bone turnover in several experimental systems in vivo. They have helped in studies of various aspects of the regulation of calcium metabolism. The diphosphonate, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) has been shown in clinical studies to be effective against ectopic calcification particularly in myositis ossificans progressiva and in disorders of increased bone resorption such as Paget's diseases and some types of osteoporosis. -99mTechnetium complexes of EHDP, PP-i and other polyphosphates have also recently been used successfully as bone scanning agents.

Topics: Animals; Bone and Bones; Bone Resorption; Calcification, Physiologic; Calcinosis; Calcium; Calcium Metabolism Disorders; Cartilage; Chemical Phenomena; Chemistry; Culture Techniques; Depression, Chemical; Diphosphates; Etidronic Acid; Humans; Hydroxyapatites; Kidney Diseases; Methylene Chloride; Organophosphonates; Organophosphorus Compounds; Osteoporosis; Urinary Bladder Calculi; Vitamin D

Topics: Adult; Aged; Arthritis; Calcinosis; Diphosphates; Female; Gout; Humans; Joint Diseases; Male; Middle Aged; Phagocytosis; Synovial Fluid; Synovitis; Terminology as Topic; Uric Acid

Topics: Animals; Bone Diseases; Bone Resorption; Calcinosis; Calcium; Diphosphates; Homeostasis; Humans; Hydroxyapatites; Hyperparathyroidism, Secondary; Kidney Failure, Chronic; Organophosphonates; Osteogenesis; Osteomalacia; Rats; Renal Dialysis; Uremia

Topics: Arthritis; Calcinosis; Calcium; Cartilage, Articular; Chemical Phenomena; Chemistry; Chondrocalcinosis; Diagnosis, Differential; Diphosphates; Geriatrics; Gout; Humans; Joint Diseases; Radiography; X-Ray Diffraction

Inorganic pyrophosphate (PPi) is a crucial extracellular mineralization regulator. Low plasma PPi concentrations underlie the soft tissue calcification present in several rare hereditary mineralization disorders as well as in more common conditions like chronic kidney disease and diabetes. Even though deregulated plasma PPi homeostasis is known to be linked to multiple human diseases, there is currently no reliable assay for its quantification. We here describe a PPi assay that employs the enzyme ATP sulfurylase to convert PPi into ATP. Generated ATP is subsequently quantified by firefly luciferase-based bioluminescence. An internal ATP standard was used to correct for sample-specific interference by matrix compounds on firefly luciferase activity. The assay was validated and shows excellent precision (< 3.5%) and accuracy (93-106%) of PPi spiked into human plasma samples. We found that of several anticoagulants tested only EDTA effectively blocked conversion of ATP into PPi in plasma after blood collection. Moreover, filtration over a 300,000-Da molecular weight cut-off membrane reduced variability of plasma PPi and removed ATP present in a membrane-enclosed compartment, possibly platelets. Applied to plasma samples of wild-type and Abcc6

Topics: Adenosine Triphosphate; Animals; Calcinosis; Diphosphates; Humans; Luciferases, Firefly; Rats

Topics: Amyloidosis; Calcinosis; Cardiomyopathies; Diphosphates; Humans; Immunoglobulin Light-chain Amyloidosis; Prealbumin; Radiopharmaceuticals

Tissue non-specific alkaline phosphatase (TNSALP) is an enzyme that is tethered to the cell membrane by glycosylphosphatidylinositol (GPI) and converts inorganic pyrophosphate to inorganic phosphate. Inorganic phosphate combines with calcium to form hydroxyapatite, the main mineral in the skeleton. When TNSALP is defective, conversion of inorganic pyrophosphate to inorganic phosphate is impaired and the skeleton is at risk of under-mineralization. Phosphatidylinositol glycan anchor biosynthesis class N (PIGN) is one of more than 20 genes in the GPI-biosynthesis family. Pathogenic variants in PIGN have been identified in multiple congenital anomalies-hypotonia-seizures syndrome (OMIM 614080), although a metabolic bone disease or skeletal fragility phenotype has not been reported. We describe a female child with multiple congenital anomalies-hypotonia-seizures syndrome due to a compound heterozygous pathogenic variant in PIGN who sustained a low-trauma distal femur fracture at age 7.4 years. We hypothesized that the GPI synthesis defect may result in metabolic bone disease from inadequate anchoring of TNSALP in bone and initiated asfotase alfa, a human bone-targeted recombinant TNSALP-Fc-deca-aspartate peptide, as it could bypass the PIGN genetic defect that possibly caused her skeletal fragility. Asfotase alfa was begun at 8.5 years. Baseline X-rays revealed mild rachitic findings of wrists and knees, which resolved by 5 months of treatment. Bone mineral density (BMD) assessed by dual-energy X-ray absorptiometry (DXA) showed mild improvement in spine, hip and total body less head after 16 months of treatment, while radius declined. She sustained additional low trauma fractures at right tibia and left humeral neck at 11 and 15 months into treatment, which healed quickly. Calcium, phosphorus, and parathyroid hormone levels have remained within the normal range over the 18 months of treatment. For adverse effect, she experienced a rash and discomfort in the first week of treatment which resolved with ibuprofen and diphenhydramine. She also developed subcutaneous fat atrophy. Overall, in this child with a compound pathogenic variant in PIGN, off-label use of asfotase alfa has been generally well tolerated with minimal side effects and resolution of rickets, but she continues to remain skeletally fragile.

Topics: Alkaline Phosphatase; Bone and Bones; Bone Diseases, Metabolic; Calcinosis; Calcium; Calcium, Dietary; Child; Diphosphates; Female; Fracture Healing; Humans; Hypophosphatasia; Muscle Hypotonia; Osteoporotic Fractures; Seizures

Pathological mineralization of intervertebral disc is debilitating and painful and linked to disc degeneration in a subset of human patients. An adenosine triphosphate efflux transporter, progressive ankylosis (ANK) is a regulator of extracellular inorganic pyrophosphate levels and plays an important role in tissue mineralization. However, the function of ANK in intervertebral disc has not been fully explored. Herein we analyzed the spinal phenotype of Ank mutant mice (ank/ank) with attenuated ANK function. Micro-computed tomography and histological analysis showed that loss of ANK function results in the aberrant annulus fibrosus mineralization and peripheral disc fusions with cranial to caudal progression in the spine. Vertebrae in ank mice exhibit elevated cortical bone mass and increased tissue non-specific alkaline phosphatase-positive endplate chondrocytes with decreased subchondral endplate porosity. The acellular dystrophic mineral inclusions in the annulus fibrosus were localized adjacent to apoptotic cells and cells that acquired osteoblast-like phenotype. Fourier transform infrared spectral imaging showed that the apatite mineral in the outer annulus fibrosus had similar chemical composition to that of vertebral bone. Transcriptomic analysis of annulus fibrosus and nucleus pulposus tissues showed changes in several biological themes with a prominent dysregulation of BMAL1/CLOCK circadian regulation. The present study provides new insights into the role of ANK in the disc tissue compartments and highlights the importance of local inorganic pyrophosphate metabolism in inhibiting the mineralization of this important connective tissue.

Topics: Animals; Calcinosis; Diphosphates; Humans; Intervertebral Disc; Intervertebral Disc Degeneration; Loss of Function Mutation; Mice; Phenotype; X-Ray Microtomography

Pseudoxanthoma elasticum, a heritable multisystem ectopic mineralization disorder, is caused by inactivating mutations in the ABCC6 gene. The encoded protein, ABCC6, a transmembrane transporter, has a specialized efflux function in hepatocytes by contributing to plasma levels of inorganic pyrophosphate, a potent inhibitor of mineralization in soft connective tissues. Reduced plasma inorganic pyrophosphate levels underlie the ectopic mineralization in pseudoxanthoma elasticum. In this study, we characterized the pathogenicity of three human ABCC6 missense variants using an adenovirus-mediated liver-specific ABCC6 transgene expression system in an Abcc6

Topics: Adenoviridae; Animals; Calcinosis; Diphosphates; Disease Models, Animal; Humans; Mice; Multidrug Resistance-Associated Proteins; Mutation, Missense; Pseudoxanthoma Elasticum; Skin

The plasma membrane protein ankylosis homologue (ANKH, mouse ortholog: Ank) prevents pathological mineralization of joints by controlling extracellular levels of the mineralization inhibitor pyrophosphate (PPi). It was long thought that ANKH acts by transporting PPi into the joints. We recently showed that when overproduced in HEK293 cells, ANKH mediates release of large amounts of nucleoside triphosphates (NTPs), predominantly ATP, into the culture medium. ATP is converted extracellularly into PPi and AMP by the ectoenzyme ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1). We could not rule out, however, that cells also release PPi directly via ANKH. We now addressed the question of whether PPi leaves cells via ANKH using HEK293 cells that completely lack ENPP1. Introduction of ANKH in these ENPP1-deficient HEK293 cells resulted in robust cellular ATP release without the concomitant increase in extracellular PPi found in ENPP1-proficient cells. Ank activity was previously shown to be responsible for about 75% of the PPi found in mouse bones. However, bones of Enpp1

Topics: Adenosine Triphosphate; Animals; Bone and Bones; Calcification, Physiologic; Calcinosis; Diphosphates; HEK293 Cells; Humans; Mice; Phosphate Transport Proteins

The pathogenesis of calcinosis cutis, a disabling complication of SSc, is poorly understood and effective treatments are lacking. Inorganic pyrophosphate (PPi) is a key regulator of ectopic mineralization, and its deficiency has been implicated in ectopic mineralization disorders. We therefore sought to test the hypothesis that SSc may be associated with reduced circulating PPi, which might play a pathogenic role in calcinosis cutis.. Subjects with SSc and age-matched controls without SSc were recruited from the outpatient rheumatology clinics at Rutgers and Northwestern Universities (US cohort), and from the Universities of Szeged and Debrecen (Hungarian cohort). Calcinosis cutis was confirmed by direct palpation, by imaging or both. Plasma PPi levels were determined in platelet-free plasma using ATP sulfurylase to convert PPi into ATP in the presence of excess adenosine 5' phosphosulfate.. Eighty-one patients with SSc (40 diffuse cutaneous, and 41 limited cutaneous SSc) in the US cohort and 45 patients with SSc (19 diffuse cutaneous and 26 limited cutaneous SSc) in the Hungarian cohort were enrolled. Calcinosis was frequently detected (40% of US and 46% of the Hungarian cohort). Plasma PPi levels were significantly reduced in both SSc cohorts with and without calcinosis (US: P = 0.003; Hungarian: P < 0.001).. Circulating PPi are significantly reduced in SSc patients with or without calcinosis. Reduced PPi may be important in the pathophysiology of calcinosis and contribute to tissue damage with chronic SSc. Administering PPi may be a therapeutic strategy and larger clinical studies are planned to confirm our findings.

Topics: Adult; Aged; Calcinosis; Diphosphates; Female; Humans; Male; Middle Aged; Scleroderma, Systemic

To explore the lived experience of people with calcium pyrophosphate deposition (CPPD) disease and the impact of this condition on their daily lives.. Patients with CPPD and their caregivers were invited to take part in a one-to-one (patient only) or paired (patient and caregiver) semi-structured interview. Interviews covered patients' diagnosis and treatment experiences, and the impact of CPPD on their daily lives. Transcribed interviews were analysed using inductive thematic analysis.. 28 patient interviews, six of which included a caregiver, were conducted across five countries. Acute CPP crystal arthritis flares resulted in temporary but profound disability for most patients, disrupting their ability to go about day-to-day activities, and they sought immediate medical attention. CPPD+OA and chronic CPP crystal inflammatory arthritis presented patients with longer term limitations in daily lives. Patients and their caregivers described these disruptions and limitations, which included a reduced ability or inability to complete household and self-care tasks, exercise, socialise, work and drive. They also described how arthritis pain and resulting limitations adversely impacted upon patients' psychological wellbeing. Delays in referral to specialists and diagnostic uncertainty were described by many. Lack of appropriate treatment or access to treatments only upon worsening of symptoms impacted upon the length of time some patients spent in pain and with functional limitations.. This study is the first to demonstrate the wide-ranging impact of CPPD, and highlights the need for improved diagnosis, physician training, as well as greater emphasis upon finding targeted therapies to specifically treat CPPD.

Topics: Calcinosis; Calcium Pyrophosphate; Caregivers; Chondrocalcinosis; Diphosphates; Humans

Calcifications can disrupt organ function in the cardiovascular system and the kidney, and are particularly common in patients with chronic kidney disease (CKD). Fetuin-A deficient mice maintained against the genetic background DBA/2 exhibit particularly severe soft tissue calcifications, while fetuin-A deficient C57BL/6 mice remain healthy. We employed molecular genetic analysis to identify risk factors of calcification in fetuin-A deficient mice. We sought to identify pharmaceutical therapeutic targets that could be influenced by dietary of parenteral supplementation. We studied the progeny of an intercross of fetuin-A deficient DBA/2 and C57BL/6 mice to identify candidate risk genes involved in calcification. We determined that a hypomorphic mutation of the Abcc6 gene, a liver ATP transporter supplying systemic pyrophosphate, and failure to regulate the Trpm6 magnesium transporter in kidney were associated with severity of calcification. Calcification prone fetuin-A deficient mice were alternatively treated with parenteral administration of fetuin-A dietary magnesium supplementation, phosphate restriction, or by or parenteral pyrophosphate. All treatments markedly reduced soft tissue calcification, demonstrated by computed tomography, histology and tissue calcium measurement. We show that pathological ectopic calcification in fetuin-A deficient DBA/2 mice is caused by a compound deficiency of three major extracellular and systemic inhibitors of calcification, namely fetuin-A, magnesium, and pyrophosphate. All three of these are individually known to contribute to stabilize protein-mineral complexes and thus inhibit mineral precipitation from extracellular fluid. We show for the first time a compound triple deficiency that can be treated by simple dietary or parenteral supplementation. This is of special importance in patients with advanced CKD, who commonly exhibit reduced serum fetuin-A, magnesium and pyrophosphate levels.

Topics: alpha-2-HS-Glycoprotein; alpha-Fetoproteins; Animals; Calcinosis; Diphosphates; Disease Models, Animal; Female; Kidney; Liver; Magnesium; Male; Mice; Mice, Inbred C57BL; Mice, Inbred DBA; Microvessels; Minerals; Multidrug Resistance-Associated Proteins; Renal Insufficiency, Chronic; TRPM Cation Channels

The membrane protein ANKH was known to prevent pathological mineralization of joints and was thought to export pyrophosphate (PPi) from cells. This did not explain, however, the presence of ANKH in tissues, such as brain, blood vessels and muscle. We now report that in cultured cells ANKH exports ATP, rather than PPi, and, unexpectedly, also citrate as a prominent metabolite. The extracellular ATP is rapidly converted into PPi, explaining the role of ANKH in preventing ankylosis. Mice lacking functional Ank (Ankank/ank mice) had plasma citrate concentrations that were 65% lower than those detected in wild type control animals. Consequently, citrate excretion via the urine was substantially reduced in Ankank/ank mice. Citrate was even undetectable in the urine of a human patient lacking functional ANKH. The hydroxyapatite of Ankank/ank mice contained dramatically reduced levels of both, citrate and PPi and displayed diminished strength. Our results show that ANKH is a critical contributor to extracellular citrate and PPi homeostasis and profoundly affects bone matrix composition and, consequently, bone quality.

Topics: Adenosine Triphosphate; Animals; Bone and Bones; Bone Development; Calcinosis; Cell Differentiation; Cells, Cultured; Citric Acid; Diphosphates; Humans; Mechanical Phenomena; Mice; Mutation; Phosphate Transport Proteins

Pyrophosphate deficiency may explain the excessive vascular calcification found in children with Hutchinson-Gilford progeria syndrome (HGPS) and in a mouse model of this disease. The present study found that hydrolysis products of ATP resulted in a <9% yield of pyrophosphate in wild-type blood and aortas, showing that eNTPD activity (ATP → phosphate) was greater than eNPP activity (ATP → pyrophosphate). Moreover, pyrophosphate synthesis from ATP was reduced and pyrophosphate hydrolysis (via TNAP; pyrophosphate → phosphate) was increased in both aortas and blood obtained from mice with HGPS. The reduced production of pyrophosphate, together with the reduction in plasma ATP, resulted in marked reduction of plasma pyrophosphate. The combination of TNAP inhibitor levamisole and eNTPD inhibitor ARL67156 increased the synthesis and reduced the degradation of pyrophosphate in aortas and blood ex vivo, suggesting that these combined inhibitors could represent a therapeutic approach for this devastating progeroid syndrome. Treatment with ATP prevented vascular calcification in HGPS mice but did not extend longevity. By contrast, combined treatment with ATP, levamisole, and ARL67156 prevented vascular calcification and extended longevity by 12% in HGPS mice. These findings suggest a therapeutic approach for children with HGPS.

Topics: Adenosine Triphosphate; Alkaline Phosphatase; Animals; Antigens, CD; Aortic Diseases; Apyrase; Calcinosis; Diphosphates; Disease Models, Animal; Gene Knock-In Techniques; Humans; Lamin Type A; Levamisole; Longevity; Male; Mice; Mice, Transgenic; Myocytes, Smooth Muscle; Phosphoric Diester Hydrolases; Progeria; Pyrophosphatases; Real-Time Polymerase Chain Reaction; RNA Interference; RNA, Small Interfering

Cardiovascular calcification is associated with high risk of vascular disease. This involves macrophage infiltration of injured vascular tissue and osteoclast-related processes. Splenic monocytes from mice, that are predisposed (C3H) or resistant (B6) to calcification, were isolated and differentiated in vitro with M-CSF to generate macrophages, which aggregate to form multinucleated (MN) cells in the presence of RANKL. MN cell formation was significantly decreased in monocytes from resistant compared with calcifying mice. Conditioned media from C3H macrophages strongly induced calcification in vitro. However, medium from B6 macrophages inhibited calcification. An increase in ICAM-1 was detected in conditioned media from C3H macrophages compared with B6, suggesting a key role for this molecule in calcification processes. Due to natural genetic loss of Abcc6, the causal gene for cardiac calcification, C3H mice have reduced plasma levels of inorganic pyrophosphate (PPi), a potential calcification inhibitor. Supplementation of C3H mice with PPi or Etidronate prevented but did not completely reverse cardiac calcification. Our data provide strong evidence of the pathogenesis of macrophages and MNs during tissue calcification and suggest PPi or its analogue Etidronate as a potential inhibitor of MN formation and calcification. Furthermore, the adhesion molecule ICAM-1 was shown to play a key role in calcification.

Topics: Animals; Bone Density Conservation Agents; Calcinosis; Cardiovascular Diseases; Cell Aggregation; Cells, Cultured; Diphosphates; Etidronic Acid; Intercellular Adhesion Molecule-1; Macrophages; Mice, Inbred C3H; Mice, Inbred C57BL

Topics: Calcinosis; Diphosphates; Humans; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phosphates

Soft tissue calcification occurs in several common acquired pathologies, such as diabetes and hypercholesterolemia, or can result from genetic disorders. ABCC6, a transmembrane transporter primarily expressed in liver and kidneys, initiates a molecular pathway inhibiting ectopic calcification. ABCC6 facilitates the cellular efflux of ATP, which is rapidly converted into pyrophosphate (PPi), a major calcification inhibitor. Heritable mutations in ABCC6 underlie the incurable calcification disorder pseudoxanthoma elasticum and some cases of generalized arterial calcification of infancy. Herein, we determined that the administration of PPi and the bisphosphonate etidronate to Abcc6

Topics: Acute Disease; Animals; ATP-Binding Cassette Transporters; Calcinosis; Chronic Disease; Diphosphates; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Etidronic Acid; Female; Liver; Male; Mice, Inbred C57BL; Mice, Knockout; Multidrug Resistance-Associated Proteins; Phenotype; Pseudoxanthoma Elasticum; Transgenes

Extensive or persistent calcium phosphate deposition within soft tissues after severe traumatic injury or major orthopedic surgery can result in pain and loss of joint function. The pathophysiology of soft tissue calcification, including dystrophic calcification and heterotopic ossification (HO), is poorly understood; consequently, current treatments are suboptimal. Here, we show that plasmin protease activity prevents dystrophic calcification within injured skeletal muscle independent of its canonical fibrinolytic function. After muscle injury, dystrophic calcifications either can be resorbed during the process of tissue healing, persist, or become organized into mature bone (HO). Without sufficient plasmin activity, dystrophic calcifications persist after muscle injury and are sufficient to induce HO. Downregulating the primary inhibitor of plasmin (α2-antiplasmin) or treating with pyrophosphate analogues prevents dystrophic calcification and subsequent HO in vivo. Because plasmin also supports bone homeostasis and fracture repair, increasing plasmin activity represents the first pharmacologic strategy to prevent soft tissue calcification without adversely affecting systemic bone physiology or concurrent muscle and bone regeneration. © 2016 American Society for Bone and Mineral Research.

Topics: Animals; Calcinosis; Cardiotoxins; Diphosphates; Fibrinolysin; Fibrinolysis; Genetic Predisposition to Disease; Mice, Inbred C57BL; Muscle, Skeletal; Ossification, Heterotopic; Regeneration

Mammalian tissues calcify with age and injury. Analogous to bone formation, osteogenic cells are thought to be recruited to the affected tissue and induce mineralization. In the heart, calcification of cardiac muscle leads to conduction system disturbances and is one of the most common pathologies underlying heart blocks. However the cell identity and mechanisms contributing to pathological heart muscle calcification remain unknown. Using lineage tracing, murine models of heart calcification and in vivo transplantation assays, we show that cardiac fibroblasts (CFs) adopt an osteoblast cell-like fate and contribute directly to heart muscle calcification. Small-molecule inhibition of ENPP1, an enzyme that is induced upon injury and regulates bone mineralization, significantly attenuated cardiac calcification. Inhibitors of bone mineralization completely prevented ectopic cardiac calcification and improved post injury heart function. Taken together, these findings highlight the plasticity of fibroblasts in contributing to ectopic calcification and identify pharmacological targets for therapeutic development.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Biomarkers; Calcification, Physiologic; Calcinosis; Cardiomyopathies; Cell Differentiation; Cell Lineage; Cell Separation; Diphosphates; Disease Models, Animal; Female; Fibroblasts; Humans; Male; Mice, Inbred C57BL; Myocardial Infarction; Myocardium; Osteogenesis; Phosphates; Phosphoric Diester Hydrolases; Pyrophosphatases

Medial arterial calcification is accelerated in patients with CKD and strongly associated with increased arterial rigidity and cardiovascular mortality. Recently, a novel in vitro blood test that provides an overall measure of calcification propensity by monitoring the maturation time (T50) of calciprotein particles in serum was described. We used this test to measure serum T50 in a prospective cohort of 184 patients with stages 3 and 4 CKD, with a median of 5.3 years of follow-up. At baseline, the major determinants of serum calcification propensity included higher serum phosphate, ionized calcium, increased bone osteoclastic activity, and lower free fetuin-A, plasma pyrophosphate, and albumin concentrations, which accounted for 49% of the variation in this parameter. Increased serum calcification propensity at baseline independently associated with aortic pulse wave velocity in the complete cohort and progressive aortic stiffening over 30 months in a subgroup of 93 patients. After adjustment for demographic, renal, cardiovascular, and biochemical covariates, including serum phosphate, risk of death among patients in the lowest T50 tertile was more than two times the risk among patients in the highest T50 tertile (adjusted hazard ratio, 2.2; 95% confidence interval, 1.1 to 5.4; P=0.04). This effect was lost, however, after additional adjustment for aortic stiffness, suggesting a shared causal pathway. Longitudinally, serum calcification propensity measurements remained temporally stable (intraclass correlation=0.81). These results suggest that serum T50 may be helpful as a biomarker in designing methods to improve defenses against vascular calcification.

Topics: Aged; Aged, 80 and over; alpha-2-HS-Glycoprotein; Arteriosclerosis; Biomarkers; Calcinosis; Calcium Phosphates; Cardiovascular Diseases; Causality; Comorbidity; Diabetes Mellitus; Diphosphates; Disease Susceptibility; Female; Follow-Up Studies; Humans; Hypertension; Male; Middle Aged; Mortality; Osteoclasts; Phosphates; Prospective Studies; Pulse Wave Analysis; Renal Dialysis; Renal Insufficiency, Chronic; Risk; Serum Albumin; Smoking; Vascular Resistance

Pseudoxanthoma elasticum (PXE) is a genetic disorder characterized by progressive calcification of soft connective tissues. The pathogenesis is still hard to pin down. In PXE dermal fibroblasts, in addition to impaired carboxylation of the vitamin K-dependent inhibitor matrix Gla protein (MGP), we have also demonstrated an up-regulation of alkaline phosphatase activity. In the light of these data we have suggested that both calcium and phosphate metabolism might be locally altered, both pathways acting in synergy on the occurrence of matrix calcification.. This study aims to better explore if cultured PXE fibroblasts, compared to control cells, exhibit a modified inorganic pyrophosphate (PPi) metabolism and are more responsive to pro-calcifying stimuli.. Primary human dermal fibroblasts isolated from healthy individuals and from PXE patients were cultured for different time points in standard and in pro-calcifying media. The expression of ANKH/ANKH, ENPP1/PC1, ALPL/TNAP, SPP1/OPN was evaluated by qRT-PCR and Western blot, respectively. TNAP activity was measured by spectrophotometric analyses, whereas calcification was investigated by light and electron microscopy as well as by micro-analytical techniques.. In the presence of pro-calcifying stimuli, dermal fibroblasts alter their phenotype favouring matrix mineralization. In particular, ENPP1/PC1 and SPP1/OPN expression, as well as TNAP activity, was differently expressed in control and in PXE fibroblasts. Moreover, in pathologic cells the ratio between factors favouring and reducing PPi availability exhibits a more pronounced shift towards a pro-calcifying balance.. PXE fibroblasts are more susceptible to pro-calcifying stimuli and in these cells an altered PPi metabolism contributes to matrix calcification.

Topics: Adult; Alkaline Phosphatase; Calcinosis; Calcium; Calcium-Binding Proteins; Diphosphates; DNA Primers; Extracellular Matrix Proteins; Female; Fibroblasts; Humans; Matrix Gla Protein; Microscopy, Electron, Scanning; Middle Aged; Pseudoxanthoma Elasticum; Skin; Spectrometry, X-Ray Emission; Up-Regulation

Pseudoxanthoma elasticum (PXE) is a rare hereditary disorder characterized by late onset and progressive calcification of elastic fibers in skin, eyes and the cardiovascular system, exemplifying a model for conditions characterized by soft tissue calcification.. The aim of our study was to characterize cellular inorganic pyrophosphate (PPi) homeostasis in PXE.. Gene expression of PPi metabolizing enzymes was determined by quantitative real-time PCR after incubation up to 21 days with or without addition of Na2HPO4. Extracellular and cytosolic PPi concentrations were measured by enzyme-linked bioluminescence assay. ALP and ENPP1 activity was determined spectrophotometrically. We further established a human cell culture model suitable for investigating PXE and related disorders without addition of artificial calcification triggers.. Independently of the experimental conditions, PXE fibroblasts revealed a higher degree of matrix calcification. We observed that matrix calcification was associated with altered gene expression of PPi metabolizing enzymes in PXE fibroblasts. In this context, PXE fibroblasts exhibited significantly higher expression of ALP and OPN and reduced mRNA expression and activity of ENPP1. Here, for the first time cytosolic and extracellular PPi levels were shown to be strongly reduced in PXE fibroblasts. We further showed that PPi concentration in bovine and human sera additives had a strong impact on matrix calcification. In a last experimental line, we demonstrated that addition of PPi analogs reduced matrix calcification of PXE fibroblasts most likely by reducing ALP and OPN mRNA expression, restoring ENPP1 activity and subsequently elevating PPi concentrations.. The results of our study along with recent findings point to the essential role of PPi as the central regulatory metabolites preventing matrix calcification in PXE. But what remains to be determined is the underlying molecular mechanism leading to depletion of PPi in PXE. We further suggest that supplementation of PPi analogs might counteract pathological calcification in PXE and related disorders.

Topics: Alkaline Phosphatase; Calcinosis; Case-Control Studies; Cells, Cultured; Diphosphates; Elastic Tissue; Fibroblasts; Gene Expression Regulation; Humans; Multidrug Resistance-Associated Proteins; Osteopontin; Phosphoric Diester Hydrolases; Pseudoxanthoma Elasticum; Pyrophosphatases; RNA, Messenger; Signal Transduction; Time Factors; Transforming Growth Factor beta1

Pyrophosphate (PPi) is a potent inhibitor of ectopic mineralization but its role during aortic valve calcification is not known.. Anti-calcific effect of PPi was investigated by using an in vitro model of serum-driven calcification of collagen sponges and decellularized porcine aortic valve leaflets. Bovine interstitial valve cells (VIC), seeded either within the collagen matrices or in transwell chambers, were used to test cellular ability to inhibit serum-induced calcification. PPi metabolism was investigated in clonal VIC harboring different calcifying potential.. In a cell-free system, high serum levels induced a dose-dependent calcification of type I collagen matrices which was prevented by PPi and ATP supplementation. Blockade of serum-driven calcification by PPi and ATP was also observed when using decellularized porcine aortic valve leaflets. A similar anti-calcific effect was also seen for bovine VIC, either statically seeded into the collagen matrices or co-cultured by using a transwell system. However, when we performed co-culture experiments by using clonal VIC harboring different calcifying potential, we observed that the subset of cells acquiring a pro-calcific profile lost the ability to protect the collagen from serum-driven calcification. Pro-calcific differentiation of the clonal VIC was accompanied by increase in ALP along with significant reduction in NPP activity and ATP/PPi extracellular accumulation. These changes were not observed in the clonal subtype with lower propensity towards calcification.. We showed that PPi and ATP are potent inhibitors of serum-driven calcification of collagen matrix and that their extracellular accumulation is reduced in calcifying VIC.

Topics: Adenosine Triphosphate; Alkaline Phosphatase; Animals; Aorta; Aortic Valve; Aortic Valve Stenosis; Calcinosis; Calcium; Cattle; Cell Differentiation; Cell-Free System; Cloning, Molecular; Collagen; Diphosphates; Microscopy, Electron, Scanning; Nucleotides; Swine; X-Ray Diffraction

Aortic valve (AV) calcification is a major cause of morbidity and mortality, yet the molecular mechanisms involved are poorly understood. Hence, an ex vivo model of calcification in intact AVs was developed in order to test the role of orthophosphate and pyrophosphate (PPi), both of which factors are known to influence vascular calcification.. Porcine AV leaflets were cultured in serum-free medium under static conditions for eight days, over which time leaflet architecture and viability were preserved. Calcification was measured as the incorporation of 45Ca, with confirmation by Alizarin Red staining.. Calcification required both a high phosphate concentration (3.8 mM) and removal of PPi with alkaline phosphatase or inorganic pyrophosphatase. Calcification occurred predominantly on the fibrosa and was arrested by the bisphosphonate etidronate, a non-hydrolyzable analog of PPi. Leaflets released PPi into the medium, and this was enhanced by MLS38949, a specific inhibitor of tissue non-specific alkaline phosphatase (TNAP). Furthermore, leaflets synthesized PPi from extracellular ATP, which was reduced by β,γ-methylene-ATP, an inhibitor of ectonucleotide pyrophosphorylase phosphodiesterase (NPP1).. The ex vivo AV calcification model developed in the present study showed that extracellular PPi, produced by valvular tissue, is a potent inhibitor of valvular calcification. In addition to synthesis, hydrolysis by TNAP also controls PPi levels and calcification. The results suggest that a decreased synthesis or increased hydrolysis of pyrophosphate may contribute to valvular calcification, and that bisphosphonates or inhibitors of TNAP are potential preventive strategies of the process. TNAP are potential preventive strategies.

Topics: Alkaline Phosphatase; Animals; Aortic Valve; Aortic Valve Stenosis; Calcinosis; Diphosphates; Etidronic Acid; Female; Phosphates; Pyrophosphatases; Swine; Tissue Culture Techniques

Pyrophosphate, which may be deficient in advanced renal failure, is a potent inhibitor of vascular calcification. To explore its use as a potential therapeutic, we injected exogenous pyrophosphate subcutaneously or intraperitoneally in normal rats and found that their plasma pyrophosphate concentrations peaked within 15 min. There was a single exponential decay with a half-life of 33 min. The kinetics were indistinguishable between the two routes of administration or in anephric rats. The effect of daily intraperitoneal pyrophosphate injections on uremic vascular calcification was then tested in rats fed a high-phosphate diet containing adenine for 28 days to induce uremia. Although the incidence of aortic calcification varied and was not altered by pyrophosphate, the calcium content of calcified aortas was significantly reduced by 70%. Studies were repeated in uremic rats given calcitriol to produce more consistent aortic calcification and treated with sodium pyrophosphate delivered intraperitoneally in a larger volume of glucose-containing solution to prolong plasma pyrophosphate levels. This maneuver significantly reduced both the incidence and amount of calcification. Quantitative histomorphometry of bone samples after double-labeling with calcein indicated that there was no effect of pyrophosphate on the rates of bone formation or mineralization. Thus, exogenous pyrophosphate can inhibit uremic vascular calcification without producing adverse effects on bone.

Topics: Animals; Calcification, Physiologic; Calcinosis; Diphosphates; Male; Osteogenesis; Rats; Rats, Sprague-Dawley; Uremia; Vascular Diseases

Pyrophosphate, a ubiquitous small-molecule inhibitor of mineralization abundantly present in the extracellular environment, binds to calcium and mineral surfaces to inhibit crystal growth. O'Neill and colleagues show in uremic rats that systemic administration of pyrophosphate prevents or reduces uremia-related vascular calcification, without overt negative consequences for bone and without calcium pyrophosphate deposition disease. These findings prompt further research into the potential of pyrophosphate as treatment for vascular calcification in chronic kidney disease patients.

Topics: Alkaline Phosphatase; Animals; Calcinosis; Diphosphates; Humans; Osteopontin; Rats; Uremia; Vascular Diseases

Pyrophosphate (PPi) is a potent inhibitor of vascular calcification and may be deficient in renal failure. We sought to determine whether plasma PPi is affected by dialysis or the mode of dialysis and whether it correlates with vascular calcification.. PPi was measured in plasma samples stored from a recent study of vascular calcification in 54 HD patients, 23 peritoneal dialysis (PD) patients and 38 patients with stage 4 chronic kidney disease (CKD). Calcification was quantified in a standardized section of the superficial femoral artery using computed tomography, and PPi was measured by enzyme assay, at both baseline and 1 year.. Baseline plasma PPi was weakly correlated with age and serum phosphate, but not with alkaline phosphatase activity or other biochemical parameters, and did not differ between HD, PD and CKD patients. Both baseline calcification score and change in the calcification score at 1 year decreased with increasing quartiles of plasma PPi. In a multivariate analysis, plasma PPi was independently correlated with baseline calcification (P = 0.039) and the change in calcification (P = 0.029).. Plasma PPi is negatively associated with vascular calcification in end-stage renal disease (ESRD) and CKD but is not affected by dialysis, the mode of dialysis or nutritional or inflammatory status. Although these data are consistent with an inhibitory effect of PPi on vascular calcification, further studies are needed to establish a causal role.

Topics: Aged; Calcinosis; Chronic Disease; Diphosphates; Female; Femoral Artery; Humans; Kidney Diseases; Kidney Failure, Chronic; Male; Middle Aged; Multivariate Analysis; Peritoneal Dialysis; Renal Dialysis; Tomography, X-Ray Computed

Topics: Alkaline Phosphatase; Calcinosis; Carrier Proteins; Chronic Disease; Diphosphates; Diphosphonates; Disease Progression; Femoral Artery; Humans; Kidney Diseases; Phosphoric Diester Hydrolases; Pyrophosphatases

Vascular calcification is a multifaceted process involving gain of calcification inducers and loss of calcification inhibitors. One such inhibitor is inorganic pyrophosphate (PP(i)), and regulated generation and homeostasis of extracellular PP(i) is a critical determinant of soft-tissue mineralization. We recently described an autocrine mechanism of extracellular PP(i) generation in cultured rat aortic vascular smooth muscle cells (VSMC) that involves both ATP release coupled to the ectophosphodiesterase/pyrophosphatase ENPP1 and efflux of intracellular PP(i) mediated or regulated by the plasma membrane protein ANK. We now report that increased cAMP signaling and elevated extracellular inorganic phosphate (P(i)) act synergistically to induce calcification of these VSMC that is correlated with progressive reduction in ability to accumulate extracellular PP(i). Attenuated PP(i) accumulation was mediated in part by cAMP-dependent decrease in ANK expression coordinated with cAMP-dependent increase in expression of TNAP, the tissue nonselective alkaline phosphatase that degrades PP(i). Stimulation of cAMP signaling did not alter ATP release or ENPP1 expression, and the cAMP-induced changes in ANK and TNAP expression were not sufficient to induce calcification. Elevated extracellular P(i) alone elicited only minor calcification and no significant changes in ANK, TNAP, or ENPP1. In contrast, combined with a cAMP stimulus, elevated P(i) induced decreases in the ATP release pathway(s) that supports ENPP1 activity; this resulted in markedly reduced rates of PP(i) accumulation that facilitated robust calcification. Calcified VSMC were characterized by maintained expression of multiple SMC differentiation marker proteins including smooth muscle (SM) alpha-actin, SM22alpha, and calponin. Notably, addition of exogenous ATP (or PP(i) per se) rescued cAMP + phosphate-treated VSMC cultures from progression to the calcified state. These observations support a model in which extracellular PP(i) generation mediated by both ANK- and ATP release-dependent mechanisms serves as a critical regulator of VSMC calcification.

Topics: Adenosine Triphosphate; Alkaline Phosphatase; Animals; Autocrine Communication; Calcinosis; Calcium-Binding Proteins; Calponins; Cells, Cultured; Cyclic AMP; Diphosphates; Homeostasis; Hyperphosphatemia; Kinetics; Male; Membrane Proteins; Microfilament Proteins; Muscle Proteins; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phosphate Transport Proteins; Phosphoric Diester Hydrolases; Pyrophosphatases; Rats; Rats, Sprague-Dawley; RNA, Messenger

Vascular calcification is associated with increased cardiovascular risk and occurs by osteochondrogenic differentiation of vascular cells. Many of the same regulatory factors that control skeletal mineralization, including the complex metabolic pathway controlling levels of the activator, inorganic phosphate, and the potent inhibitor, pyrophosphate, also govern vascular calcification. We previously found that the cAMP/PKA signaling pathway mediates in vitro vascular cell calcification induced by inflammatory factors including tumor necrosis factor-alpha 1 and oxidized phospholipids. In this report, we tested whether this signaling pathway modulates phosphate and pyrophosphate metabolism. Treatment of primary murine aortic cells with the PKA activator, forskolin, significantly induced osteoblastic differentiation markers, including alkaline phosphatase (ALP), osteopontin, and osteocalcin as well as the pyrophosphate generator, ectonucleotide-pyrophosphatase/phosphodiesterase-1 (Enpp1) and the pyrophosphate transporter, ankylosis protein, but not the sodium/phosphate cotransporter, Pit-1. In the presence of a substrate for ALP, beta-glycerophosphate, which generates inorganic phosphate, forskolin also enhanced matrix mineralization. Inhibitors of ALP or Pit-1 abrogated forskolin-induced osteopontin expression and mineralization but not forskolin-induced osteocalcin or ALP. These results suggest that phosphate is necessary for PKA-induced calcification of vascular cells and that the extent of PKA-induced calcification is controlled by feedback induction of the inhibitor, pyrophosphate.

Topics: Alkaline Phosphatase; Animals; Aorta; Biological Transport; Calcinosis; Cell Differentiation; Cells, Cultured; Colforsin; Cyclic AMP-Dependent Protein Kinases; Diphosphates; Hyperparathyroidism; Mice; Osteoblasts; Osteocalcin; Osteopontin; Phosphates

Pyrophosphate is a potent inhibitor of medial vascular calcification where its level is controlled by hydrolysis via a tissue-nonspecific alkaline phosphatase (TNAP). We sought to determine if increased TNAP activity could explain the pyrophosphate deficiency and vascular calcification seen in renal failure. TNAP activity increased twofold in intact aortas and in aortic homogenates from rats made uremic by feeding adenine or by 5/6 nephrectomy. Immunoblotting showed an increase in protein abundance but there was no increase in TNAP mRNA assessed by quantitative polymerase chain reaction. Hydrolysis of pyrophosphate by rat aortic rings was inhibited about half by the nonspecific alkaline phosphatase inhibitor levamisole and was reduced about half in aortas from mice lacking TNAP. Hydrolysis was increased in aortic rings from uremic rats and all of this increase was inhibited by levamisole. An increase in TNAP activity and pyrophosphate hydrolysis also occurred when aortic rings from normal rats were incubated with uremic rat plasma. These results suggest that a circulating factor causes pyrophosphate deficiency by regulating TNAP activity and that vascular calcification in renal failure may result from the action of this factor. If proven by future studies, this mechanism will identify alkaline phosphatase as a potential therapeutic target.

Topics: Alkaline Phosphatase; Animals; Calcinosis; Diphosphates; Hydrolysis; Rats; Up-Regulation; Uremia; Vascular Diseases

Calcium pyrophosphate dihydrate (CPPD) crystals are commonly found in osteoarthritic joint tissues, where they predict severe disease. Unlike other types of calcium phosphate crystals, CPPD crystals form almost exclusively in the pericellular matrix of damaged articular cartilage, suggesting a key role for the extracellular matrix milieu in their development. Osteopontin is a matricellular protein found in increased quantities in the pericellular matrix of osteoarthritic cartilage. Osteopontin modulates the formation of calcium-containing crystals in many settings. We show here that osteopontin stimulates ATP-induced CPPD crystal formation by chondrocytes in vitro. This effect is augmented by osteopontin's incorporation into extracellular matrix by transglutaminase enzymes, is only modestly affected by its phosphorylation state, and is inhibited by integrin blockers. Surprisingly, osteopontin stimulates transglutaminase activity in cultured chondrocytes in a dose-responsive manner. As elevated levels of transglutaminase activity promote extracellular matrix changes that permit CPPD crystal formation, this is one possible mechanism of action. We demonstrate the presence of osteopontin in the pericellular matrix of chondrocytes adjacent to CPPD deposits and near active transglutaminases. Thus, osteopontin may play an important role in facilitating CPPD crystal formation in articular cartilage.

Topics: Adenosine Triphosphate; Animals; Cadaverine; Calcinosis; Calcium Pyrophosphate; Cartilage, Articular; Chondrocytes; Cystamine; Diphosphates; Enzyme-Linked Immunosorbent Assay; Extracellular Matrix; Immunohistochemistry; Osteopontin; Sus scrofa; Thrombin; Transglutaminases

Topics: Alkaline Phosphatase; Animals; Blood Vessels; Calcinosis; Diphosphates; Humans

We recently linked human arterial media calcification of infancy to heritable PC-1/nucleotide pyrophosphatase phosphodiesterase 1 (NPP1) deficiency. NPP1 hydrolyzes ATP to generate PP(i), a physicochemical inhibitor of hydroxyapatite crystal growth. But pathologic calcification in NPP1 deficiency states is tissue-restricted and in perispinal ligaments is endochondral differentiation-mediated rather than simply a dystrophic process. Because ectopic chondro-osseous differentiation promotes artery calcification in atherosclerosis and other disorders, we tested the hypothesis that NPP1 and PP(i) deficiencies regulate cell phenotype plasticity to promote artery calcification.. Using cultured multipotential NPP1-/- mouse bone marrow stromal cells, we demonstrated spontaneous chondrogenesis inhibitable by treatment with exogenous PP(i). We also demonstrated cartilage-specific gene expression, upregulated alkaline phosphatase, decreased expression of the physiological calcification inhibitor osteopontin, and increased calcification in NPP1-/- aortic smooth muscle cells (SMCs). Similar changes were demonstrated in aortic SMCs from ank/ank mice, which are extracellular PP(i)-depleted because of defective ANK transmembrane PP(i) transport activity. Moreover, NPP1-/- and ank/ank mice demonstrated aortic media calcification by von Kossa staining, and intra-aortic cartilage-specific collagen gene expression was demonstrated in situ in NPP1-/- mice.. NPP1 and PP(i) deficiencies modulate phenotype plasticity in artery SMCs and chondrogenesis in mesenchymal precursors, thereby stimulating artery calcification by modulating cell differentiation.

Topics: Animals; Aorta; Bone Marrow Cells; Calcinosis; Cell Differentiation; Cells, Cultured; Chondrogenesis; Diphosphates; Female; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Phenotype; Phosphate Transport Proteins; Phosphoric Diester Hydrolases; Pyrophosphatases; Stromal Cells

In idiopathic chondrocalcinosis and in osteoarthritis (OA), increased extracellular PP(i) (ecPP(i)) promotes calcification. In chromosome 5p-associated familial chondrocalcinotic degenerative arthropathy, certain mutations in the membrane protein ANK may chronically raise ecPP(i) via enhanced PP(i) channeling. Therefore, we assessed if dysregulated wild-type ANK expression could contribute to pathogenesis of idiopathic degenerative arthropathy through elevated ecPP(i).. Using cells with genetic alterations in expression of ANK and the PP(i)-generating nucleotide pyrophosphatase phosphodiestrase (NPP) PC-1, we examined how increased ANK expression elevates ecPPI, testing for codependent effects with PC-1. We also evaluated the effects of ANK expression on chondrocyte growth, matrix synthesis, and MMP-13 expression and we immunohistochemically examined ANK expression in situ in human knee OA cartilages.. Using cells expressing defective ANK, as well as PC-1 knockout cells, we demonstrated that ANK required PC-1 (and vice versa) to raise ecPP(i) and that the major ecPP(i) regulator TGFbeta required both ANK and PC-1 to elevate ecPP(i). Upregulation of wild-type ANK by transfection in normal chondrocytes not only raised ecPP(i) 5-fold to approximately 100nM but also directly stimulated matrix calcification and inhibited collagen and sulfated proteoglycans synthesis. In addition, upregulated ANK induced chondrocyte MMP-13, an effect that also was stimulated within 2h by treatment of chondrocytes with 100nM PP(i) alone. Finally, ANK expression was upregulated in situ in human knee OA cartilages.. Elevation of ecPP(i) by ANK critically requires the fraction of cellular PP(i) generated by PC-1. The upregulation of ANK expression in OA cartilage and the capacity of increased ANK expression to induce MMP-13 and to promote matrix loss suggest that increased ANK expression and ecPP(i) exert noxious effects in degenerative arthropathies beyond stimulation of calcification.

Topics: Animals; Calcinosis; Cartilage, Articular; Cells, Cultured; Chondrocytes; Collagen; Collagenases; Diphosphates; Extracellular Fluid; Humans; Immunohistochemistry; Knee Joint; Matrix Metalloproteinase 13; Mice; Mice, Inbred Strains; Osteoarthritis, Knee; Phosphoric Diester Hydrolases; Proteoglycans; Pyrophosphatases; Transfection; Transforming Growth Factor beta; Up-Regulation

Osteopontin and PP(i) both suppress hydroxyapatite deposition. Extracellular PP(i) deficiency causes spontaneous hypercalcification, yet unchallenged osteopontin knockout mice have only subtle mineralization abnormalities. We report that extracellular PP(i) deficiency promotes osteopontin deficiency and correction of osteopontin deficiency prevents hypercalcification, suggesting synergistic inhibition of hydroxyapatite deposition. Nucleotide pyrophosphatase phosphodiesterase (NPP) isozymes including PC-1 (NPP1) function partly to generate PP(i), a physiologic calcification inhibitor. PP(i) transport is modulated by the membrane channel protein ANK. Spontaneous articular cartilage calcification, increased vertebral cortical bone formation, and peripheral joint and intervertebral ossific ankylosis are associated with both PC-1 deficiency and expression of truncated ANK in ank/ank mice. To assess how PC-1, ANK, and PP(i) regulate both calcification and cell differentiation, we studied cultured PC-1 -/- and ank/ank mouse calvarial osteoblasts. PC-1 -/- osteoblasts demonstrated approximately 50% depressed NPP activity and markedly lowered extracellular PP(i) associated with hypercalcification. These abnormalities were rescued by transfection of PC-1 but not of the NPP isozyme B10/NPP3. PC-1 -/- and ank/ank cultured osteoblasts demonstrated not only comparable extracellular PP(i) depression and hypercalcification but also marked reduction in expression of osteopontin (OPN), another direct calcification inhibitor. Soluble PC-1 (which corrected extracellular PP(i) and OPN), and OPN itself (> or = 15 pg/ml), corrected hypercalcification by PC-1 -/- and ank/ank osteoblasts. Thus, linked regulatory effects on extracellular PP(i) and OPN expression mediate the ability of PC-1 and ANK to regulate calcification.

Topics: Alkaline Phosphatase; Animals; Base Sequence; Bone and Bones; Calcification, Physiologic; Calcinosis; Diphosphates; DNA Primers; DNA, Complementary; Extracellular Fluid; Membrane Proteins; Mice; Mice, Knockout; Osteoblasts; Osteopontin; Phosphate Transport Proteins; Phosphoric Diester Hydrolases; Pyrophosphatases; Recombinant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Sialoglycoproteins

Inogranic pyrophosphate (PPi) inhibits hydroxyapatite deposition, and mice deficient in the PPi-generating nucleoside triphosphate pyrophosphohydrolase (NTPPPH) Plasma cell membrane glycoprotein-1 (PC-1) develop peri-articular and arterial calcification in early life. In idiopathic infantile arterial calcification (IIAC), hydroxyapatite deposition and smooth muscle cell (SMC) proliferation occur, sometimes associated with peri-articular calcification. Thus, we assessed PC-1 expression and PPi metabolism in a 25-month-old boy with IIAC and peri-articular calcifications. Plasma PC-1 was <1 ng/ml by enzyme-linked immunosorbent assay in the proband, but 10 to 30 ng/ml in unaffected family members and controls. PC-1 functioned to raise extracellular PPi in cultured aortic SMCs. However, PC-1 was sparse in temporal artery lesion SMCs in the proband, unlike the case for SMCs in atherosclerotic carotid artery lesions of unrelated adults. Proband plasma and explant-cultured dermal fibroblast NTPPPH and PPi were markedly decreased. The proband was heterozygous at the PC-1 locus, and sizes of PC-1 mRNA and polypeptide, and the PC-1 mRNA-coding region sequence were normal in proband fibroblasts. However, immunoreactive PC-1 protein was relatively sparse in proband fibroblasts. In conclusion, deficient extracellular PPi and a deficiency of PC-1 NTPPPH activity can be associated with human infantile arterial and peri-articular calcification, and may help explain the sharing of certain phenotypic features between some IIAC patients and PC-1-deficient mice.

Topics: Arteriosclerosis; Blotting, Northern; Calcinosis; Cells, Cultured; Child; Child, Preschool; Diphosphates; DNA; Extracellular Space; Family Health; Female; Fibroblasts; Gene Expression Regulation, Enzymologic; Humans; Immunohistochemistry; Infant; Male; Membrane Glycoproteins; Microscopy, Confocal; Muscle, Smooth, Vascular; Pedigree; Phosphoric Diester Hydrolases; Pyrophosphatases; RNA; Sequence Analysis, DNA; Skin

Mutation at the mouse progressive ankylosis (ank) locus causes a generalized, progressive form of arthritis accompanied by mineral deposition, formation of bony outgrowths, and joint destruction. Here, we show that the ank locus encodes a multipass transmembrane protein (ANK) that is expressed in joints and other tissues and controls pyrophosphate levels in cultured cells. A highly conserved gene is present in humans and other vertebrates. These results identify ANK-mediated control of pyrophosphate levels as a possible mechanism regulating tissue calcification and susceptibility to arthritis in higher animals.

Topics: Animals; Arthritis; Base Sequence; Biological Transport; Calcinosis; Chromosome Mapping; Cloning, Molecular; COS Cells; Diphosphates; DNA; Durapatite; Gene Expression; Genetic Complementation Test; Humans; Membrane Proteins; Mice; Mice, Transgenic; Molecular Sequence Data; Mutation; Phenotype; Phosphate Transport Proteins; Physical Chromosome Mapping; Sequence Homology, Nucleic Acid; Tissue Distribution

Topics: Arterial Occlusive Diseases; Calcinosis; Cardiomegaly; Cardiomyopathies; Carpal Bones; Child, Preschool; Consanguinity; Developmental Disabilities; Diphosphates; Humans; Infant; Infant, Newborn; Male; Radiography; Treatment Outcome

Chondrocytes exposed to nitric oxide (NO) or antibody to Fas undergo cell death by apoptosis. This study examines structural and functional properties of chondrocyte-derived apoptotic bodies. In NO treated cartilage, the dense pericellular matrix that normally surrounds the cells is degraded and apoptotic bodies accumulate within and in the vicinity of the chondrocyte lacunae. Functional analysis shows that apoptotic bodies isolated from NO-treated chondrocytes or cartilage produce pyrophosphate. The levels of pyrophosphate produced by apoptotic bodies are increased by pretreatment of the chondrocytes with transforming growth factor beta and decreased by interleukin 1. Apoptotic bodies contain alkaline phosphatase and NTP pyrophosphohydrolase activities and can precipitate calcium. These results suggest that chondrocyte-derived apoptotic bodies express functional properties that may contribute to the pathologic cartilage calcification observed in aging and osteoarthritis.

Topics: Adult; Alkaline Phosphatase; Apoptosis; Calcinosis; Calcium; Cartilage, Articular; Cells, Cultured; Chondrocytes; Diphosphates; fas Receptor; Female; Femur; Humans; Male; Membrane Glycoproteins; Middle Aged; Nitric Oxide; Phosphoric Diester Hydrolases; Pyrophosphatases

Topics: Arteries; Calcinosis; Diphosphates; Humans; Infant; Vascular Diseases

We report a case of rupture of the extensor tendons at the wrist shown histologically to be related to calcium pyrophosphate crystal deposition disease. This cause for extensor tendon rupture has not previously been described.

Topics: Aged; Calcinosis; Calcium Pyrophosphate; Carpal Tunnel Syndrome; Crystallization; Diphosphates; Female; Fingers; Humans; Radiography; Rupture; Synovial Membrane; Synovitis; Tendon Injuries; Wrist Joint

Topics: Aged; Aged, 80 and over; Calcinosis; Calcium Pyrophosphate; Crystallization; Diphosphates; Female; Fingers; Humans; Muscular Diseases; Rupture, Spontaneous; Tendons

The kinetics of calcium pyrophosphate dihydrate (CPPD) crystal growth was studied by allowing calcium and pyrophosphate (PPi-4) ions to diffuse through a denatured collagen matrix (biological grade gelatin) in the presence of either ferric or ferrous ions. Ferric and, to some extent, ferrous ions blocked the migration of the PPi-4 diffusion gradient. This retardation in the [PPi-4] gradient led to numerous changes in the patterns of CPPD crystal formation. At the initial stages of crystal growth, the iron ions induced more crystal growth compared to control. At later incubation times, ferrous and ferric ions enhanced crystal growth at the expense of crystal nucleation. The presence of both ferrous and ferric ions resulted in the more rapid formation of the two crystals observed in vivo, triclinic CPPD and monoclinic CPPD. Further, both ferrous and ferric ions also reduced the solubility of the crystalline material in the broad diffuse band which formed when the Ca+2 and PPi-4 gradients first met. In this system, the presence of either ferrous or ferric ions increased the amount of hydroxyproline included in the crystalline precipitates. Iron was also incorporated into the crystals, particularly into the triclinic CPPD and monoclinic CPPD crystals.

Topics: Calcinosis; Calcium Pyrophosphate; Chlorides; Crystallization; Diphosphates; Ferric Compounds; Gelatin; Humans; Hydroxyproline; Kinetics; Microscopy, Electron, Scanning; Models, Biological

Using transmission electron microscopy, selected area electron diffraction, and micro x-ray diffraction techniques, we studied calcium pyrophosphate dihydrate (CPPD) deposits from 23 patients with chondrocalcinosis affecting the femoral head to delineate the cellular and matrix environment in which CPPD crystals form, to determine the sequence of crystal deposition, and to address the question of coexistent calcium apatite crystal deposition. We found 2 types of CPPD crystal deposits with few transitional forms. First, small collections of crystals were seen at the border of the territorial matrix at the articular and subarticular poles of the chondron. CPPD crystal deposits were unassociated with collagen or matrix vesicles. Second, and more frequently, large collections of randomly arranged crystals (agglomerates) were observed, the smallest replacing the chondrocyte and adjacent pericellular matrix. Chondrocytes adjacent to crystal deposits were intact. Coexistent apatite crystal deposition was demonstrated in only 2 of 23 cartilages ultrastructurally examined, providing evidence that mixed crystal deposits are possible but not common in CPPD crystal arthropathy.

Topics: Aged; Aged, 80 and over; Calcinosis; Calcium Pyrophosphate; Cartilage; Crystallization; Diphosphates; Electron Probe Microanalysis; Female; Humans; Joint Diseases; Male; Microscopy, Electron

In a series of 28 long-term dialysis patients with musculoskeletal complaints, the radiologic findings in six cases resembled those occurring in the arthropathy of idiopathic calcium pyrophosphate dihydrate deposition (CPPD) disease. These findings included osteophytes, subchondral cysts, and cartilage loss in the metacarpophalangeal joints, patellofemoral joints, wrists, and shoulders. Chondrocalcinosis was present in three of the six cases. There were no significant differences in renal function or levels of serum calcium, phosphorus, iron, ferritin, aluminum, or parathormone between these patients and a control group matched for sex and age. Long-term dialysis may be associated with a metabolic arthritis similar to the arthritis which occurs in CPPD deposition disease. The etiology may include deposition of CPPD crystals, hydroxyapatite, or other calcium-containing substances in joints, or it may be related to a number of dialysis-induced metabolic abnormalities.

Topics: Arthritis; Arthrography; Calcinosis; Calcium Pyrophosphate; Cartilage, Articular; Cysts; Diphosphates; Hemochromatosis; Humans; Hyperparathyroidism, Secondary; Iron; Kidney Failure, Chronic; Renal Dialysis

Calcium pyrophosphate dihydrate crystal deposition disease (CPDD) was recognized in 4 of 30 free-ranging rhesus macaques. By means of tissue radiography, focal radiodensities were noted in lumbar intervertebral discs, menisci, and articular cartilage. Crystal deposits were identified as calcium pyrophosphate dihydrate (Ca2P2O7 X 2H2O) by means of X-ray diffraction. The pathogenesis of calcium pyrophosphate dihydrate arthropathy in man remains elusive. However, with the recognition of this arthritis in a well defined population of aged nonhuman primates, a model now exists to facilitate the study of this disease.

Topics: Animals; Animals, Wild; Calcinosis; Calcium Pyrophosphate; Connective Tissue Diseases; Diphosphates; Macaca mulatta; Monkey Diseases; Radiography; X-Ray Diffraction

Patients with rhabdomyolysis (RBD) and acute renal failure (ARF) are hypocalcemic during the oliguric phase of ARF and over 30% develop hypercalcemia during the diuretic phase. The present study examined the factors underlying these derangements in calcium metabolism in 15 patients: 7 with RBD and ARF, 4 with RBD only, and 4 with ARF only. All patients had hypocalcemia on admission and the hypocalcemia was more pronounced in those with RBD and ARF. All patients with RBD independent of the presence or absence of ARF had calcium deposition in soft tissues as documented by technetium-99 scan. In 4 patients with RBD and ARF, hypercalcemia developed during the diuretic phase at a time when Serum PTH levels were undetectable. Only patients with RBD and ARF had a significant increase in serum levels of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D [1,25(OH)2D] during the diuretic phase and both the increments in and the levels of 1,25(OH)2D were significantly greater in those who were hypercalcemic. The data indicate that 1) hypocalcemia occurs in RBD independent of ARF and is most likely related to calcium deposition in injured tissues, and 2) elevation in serum levels of 1,25(OH)2D plays an important role in the genesis of hypercalcemia during the diuretic phase of patients with RBD and ARF. Our observations suggest that extrarenal production of 1,25(OH)2D may occur in these patients, and/or that the renal production of 1,25(OH)2D may not be so tightly controlled as it is in normal subjects.

Topics: Acute Kidney Injury; Adult; Calcinosis; Calcitriol; Diphosphates; Diuresis; Female; Humans; Hypercalcemia; Hypocalcemia; Male; Middle Aged; Parathyroid Hormone; Radionuclide Imaging; Rhabdomyolysis; Technetium; Technetium Tc 99m Pyrophosphate; Time Factors

Topics: Aged; Bursitis; Calcinosis; Calcium Pyrophosphate; Diphosphates; Female; Hip Joint; Humans; Osteoarthritis

A patient with primary hyperparathyroidism whose bone scan showed signs of extensive pulmonary and gastric calcifications is described. The patient also had renal insufficiency. A review of the literature and of data of 13 patients with primary hyperparathyroidism who were seen in the Department of Internal Medicine at the University Hospital of Maastricht, led to the conclusion that only in patients with renal insufficiency could ectopic calcifications be expected to occur. Phosphate retention, rather than the hyperphosphaturia that occurs in that particular situation, is cited as the cause.

Topics: Bone and Bones; Calcinosis; Diphosphates; Humans; Hyperparathyroidism; Lung Diseases; Male; Middle Aged; Radionuclide Imaging; Stomach Diseases; Technetium; Technetium Tc 99m Pyrophosphate

Topics: Aged; Calcinosis; Calcium Pyrophosphate; Cervical Vertebrae; Diphosphates; Female; Humans; Radiography; Spinal Diseases

Adenosine triphosphate pyrophosphohydrolase (ATPPPH) and neutral inorganic pyrophosphatase activities were assayed in synovial fluids (SF) from 37 patients with a variety of arthropathies. ATPPPH activity was detected in all fluids, but was highest in patients with chronic chondrocalcinosis; its activity in patients with osteoarthritis was higher than that in patients with rheumatoid arthritis, gout, or pseudogout. ATPPPH activity correlated positively with SF pyrophosphate concentration and negatively with SF white blood cell count. Pyrophosphatase activity did not correlate with diagnosis, pyrophosphate level, or white blood cell count.

Topics: Adenosine Triphosphatases; Adult; Aged; Calcinosis; Calcium Pyrophosphate; Chondrocalcinosis; Crystallization; Diphosphates; Female; Humans; Male; Middle Aged; Osteoarthritis; Pyrophosphatases; Synovial Fluid

Clinical features of calcium pyrophosphate dihydrate crystal deposition disease (CPPD c.d.d.) were studied and the following results were obtained. The prevalence of CPPD c.d.d. was 9.7% in 300 persons aged 50 or older, who stayed or worked at an old-age home. The most common type of CPPD c.d.d. was the asymptomatic type. Comparative studies between the patients with CPPD c.d.d. and subjects without it revealed that scoliosis of the lumbar spine, osteoarthritis-like changes of the knee, subchondral bone cyst and patella wrapped around the femur were statistically more frequent in the former. The clinical study of 50 patients with CPPD c.d.d. revealed calcification not only in the articular cartilage but also in periarticular tissues and ligamentum flavum. The histological study demonstrated frequent destructive changes of the tissues around the site of CPPD crystal deposition. Formation of CPPD crystals appeared to be initiated by degenerating chondrocytes and metaplastic chondrocytes.

Topics: Age Factors; Aged; Blood Chemical Analysis; Calcinosis; Calcium Pyrophosphate; Crystallization; Diphosphates; Female; Humans; Joint Diseases; Knee Joint; Ligaments; Lumbar Vertebrae; Male; Middle Aged; Radiography

The authors conducted a comprehensive radiographic and pathological investigation of more than 1,000 postmortem spinal specimens and documented many examples of calcium pyrophosphate dihydrate crystal deposition disease (CPPD/CDD) in a variety of vertebral structures, including not only the intervertebral disk but also the apophyseal and sacroiliac joints, posterior longitudinal ligament, interspinous and supraspinous ligaments, ligamentum flavum, interosseous sacroiliac ligament, transverse atlas ligament, and posterior median atlanto-axial joint. Such crystal accumulation supports previous reports of abnormal calcification and structural damage on radiographs of the axial skeleton in patients with CPPD/CDD and may explain not only the associated spinal symptoms and signs but also spinal stenosis, spondylolisthesis, and atlanto-axial subluxation.

Topics: Calcinosis; Calcium Pyrophosphate; Diphosphates; Humans; Intervertebral Disc; Radiography; Spinal Diseases

Calcium pyrophosphate (CPPD) and apatite crystals are associated with several types of arthritis. Using transmission electron microscopy both the tiny apatite-like crystals and larger CPPD can be seen to be associated with granular materials. With the ferritin bridge technique immunoglobulins and complement are seen in the material with the apatite but not the CPPD. Immunoprotein is seen both intracellularly and extracellularly. Further study of these coatings is needed to ascertain if they have consistent patterns on all crystals and how they affect the ability of the crystals to induce inflammation.

Topics: Calcinosis; Calcium Pyrophosphate; Crystallization; Diphosphates; Durapatite; Humans; Hydroxyapatites; Microscopy, Electron; Osteoarthritis; Proteins; Synovial Fluid

Topics: Aged; Apatites; Calcinosis; Calcium Pyrophosphate; Carpal Tunnel Syndrome; Diphosphates; Humans; Male; Radiography; Synovial Membrane; Tendons

It was shown that it is apparently impossible for any calcification to occur in a system which contains a constant, physiological concentration of inorganic pyrophosphate. These results give further support to the earlier suggestion that inhibitors of calcium phosphate crystal growth must be removed from or denied access to the site of calcification to allow for the normal formation of the mineral phase. This study also suggests that the means of assessing the relative importance of a calcification inhibitor should be altered, since it is the equilibrium concentration of an inhibitor, and not its initial concentration in an assay system, which has physiological relevance.

Topics: Calcinosis; Calcium Phosphates; Crystallization; Diphosphates

Synthetic hydroxyapatite (HA) crystals in 1% serum stimulated 3H thymidine uptake into quiescent canine synovial fibroblasts and human foreskin fibroblast cultures, as did 10% serum. The onset of stimulation and peak uptake of thymidine after crystal addition were delayed by 2-3 hours as compared with the effects produced by 10% serum. Stimulation of 3H thymidine uptake was proportional to the serum concentration used. HA crystals (50 micrograms/ml) stimulated nuclide uptake at each serum concentration used. 3H thymidine uptake was also proportional to the dose of HA or calcium pyrophosphate dihydrate crystals, although larger doses of the latter crystal were required to produce equivalent effects. Not all particulates were effective mitogenic agents. Latex beads and diamond crystals had no effect. Monosodium urate crystals modestly stimulated and calcium urate crystals markedly stimulated nuclide uptake. The more complex crystals found in a naturally occurring condition (calcinosis) were as mitogenic as the pure synthetic HA. The synovial cell hyperplasia sometimes associated with crystals might be explained in part by their mitogenic activity.

Topics: Animals; Calcinosis; Calcium Pyrophosphate; Cells, Cultured; Crystallization; Diphosphates; Dogs; Dose-Response Relationship, Drug; Durapatite; Fibroblasts; Humans; Hydroxyapatites; Mitogens; Thymidine; Uric Acid

The clinical records and hand and wrist radiographs of 51 patients with calcium pyrophosphate dihydrate crystal deposition disease have been analyzed, and symptomatology and radiologic abnormalities have been correlated. Characteristic roentgenographic features included cartilage and synovial calcification and arthropathy of the metacarpophalangeal joints and the radiocarpal compartment of the wrist, including scapholunate dissociation. Clinical-radiologic correlation revealed many asymptomatic patients with calcification and arthropathy and many symptomatic patients with normal radiographs. Thorough radiologic evaluation may reveal many patients with this disorder before the onset of clinical symptoms.

Topics: Aged; Calcinosis; Calcium Pyrophosphate; Diphosphates; Female; Hand; Humans; Male; Middle Aged; Radiography; Wrist

Topics: Bone Diseases; Calcinosis; Calcium Pyrophosphate; Diphosphates; Fingers; Humans; Male; Middle Aged; Radiography

Two cases of chronic renal failure showing very interesting technetium-99m-pyrophosphate bone scans are presented. In both cases striking uptake of activity was shown in the left ventricle of the heart, the mucosa of the stomach and in both lungs. This picture was attributed to metastatic calcification in these organs. Cases of metastatic calcification demonstrated with bone-seeking agents have been presented previously, but have mainly shown intense uptake of activity in the lungs and in a few cases, and to a lesser degree, in the stomach. However, we believe that our cases are unique in showing especially the left ventricle of the heart as well as the mucosa of th stomach with exceptional clarity.

Topics: Adult; Bone and Bones; Calcinosis; Diphosphates; Female; Heart; Humans; Kidney Failure, Chronic; Mucous Membrane; Radionuclide Imaging; Stomach; Technetium; Technetium Tc 99m Pyrophosphate

The spontaneous occurrence of perimyocardial calcification localized in the right ventricle has been reported in an inbred strain of DBA/2 mice. In this paper we examined the correlation between the myocardial uptake ratio of technetium-99m pyrophosphate (99mTc-PYP) and pathological findings in these mice ranging in age from one to 12 months and became lower with age, while calcification and fibrosis in the perimyocardium of the right ventricle became more prominent in aged mice. This may be due to an insidious onset of degeneration with calcification and fibrosis in spontaneously occurring perimyocardial lesions in these mice. Persistent abnormal uptake of 99mTc-PYP observed in the present study suggests the usefulness of such scintigrams in the diagnosis of chronic perimyocardial disease.

Topics: Animals; Calcinosis; Cardiomyopathies; Diphosphates; Heart; Mice; Mice, Inbred DBA; Myocardium; Radionuclide Imaging; Technetium; Technetium Tc 99m Pyrophosphate

Hydroxyapatite crystals are a common cause of periarticular disease, but recent studies have shown that they may also be deposited intra-articularly, either as a primary phenomenon or secondary to another disease. A continuum of abnormalities from monoarticular periarthritis to polyarticular disease and finally joint destruction may occur.

Topics: Adult; Aged; Arthritis; Calcinosis; Diphosphates; Female; Finger Joint; Humans; Hydroxyapatites; Knee Joint; Male; Middle Aged; Periarthritis; Radiography; Uric Acid

Topics: Aged; Calcinosis; Cardiomyopathies; Diphosphates; Humans; Male; Radiography; Radioisotopes; Radionuclide Imaging; Technetium; Thallium

Topics: Calcinosis; Diphosphates; Humans; Male; Middle Aged; Radionuclide Imaging; Technetium

Topics: Calcinosis; Cystadenoma; Diphosphates; Female; Humans; Middle Aged; Ovarian Neoplasms; Radionuclide Imaging; Technetium

Pyrophosphate labeled with 99Tc was evaluated as an indicator of the calcification which occurs after implantation of polymeric materials in rats. Poly(2-hydroxyethyl methacrylate), both porous and homogeneous, had been implanted. 99Tc pyrophosphate was applied intravenously to rats in intervals from 14 days to 15 months. Scintigraphy, x-ray examination, and histology were carried out. The ratio of specific activity in the capsule around the implant to specific activity in the reference tissue was determined. The cumulation of activity was parallel with the development of calcification as revealed by histology. The method can be used not only in the screening test of new polymeric materials, but also in a quantitative determination of the degree of calcification in general.

Topics: Animals; Calcinosis; Diphosphates; Polymers; Prostheses and Implants; Radionuclide Imaging; Rats; Technetium; Technetium Tc 99m Pyrophosphate

A case of tumoural calcinosis in a 61-years-old man. This is a rare condition (60 published cases), affecting above all black subjects. It takes the form of hard rounded masses which progressively increase in size and vary in their location (hips, elbows, shoulders, periscapular region). On X-rays, the tumour is rounded, consisting of a mass of several calcified small nodules. On technetium pyrophosphate isotope scanning, there is very marked and periarticular uptake. There is often hyperphosphoraemia associated with normal blood calcium levels, without any abnormality in the hormones controlling calcium and phosphate metabolism. Treatment usually consists of the excision of the tumour masses. More recently, the reduction of hyperphosphoraemia by the prescription of aluminium salts and a reduction in phosphorus intake has been suggested.

Topics: Bone Neoplasms; Calcinosis; Calcium; Diphosphates; Humans; Male; Middle Aged; Phosphorus; Radionuclide Imaging; Technetium; White People

The deposition and ultrastructure of calcium pyrophosphate (CPPD) crystals in joint tissues of pseudogout patients and cadavers were studied. Nine calcified menisci, 2 articular cartilages and 6 samples of synovial fluid were examined by scanning electron microscopy (SEM). Some of them were examined by analytical electron microscopy (EMMA). In the samples of menisci and cartilages, the findings were compared with those in the soft X-ray examinations and polarized light microscopy. The results are summarized as follows: 1) SEM observation of the cut surfaces of calcified menisci and cartilages showed a three-dimensional ultrastructure for the CPPD crystals. The crystals in the synovial fluid taken from pseudogout knees were also clearly demonstrated by this method. The EMMA analysis provided the possibility to examine the structure and content of the crystals simultaneously. 2) Crystal deposition in the meniscus varied with the depth of the tissues; it was diffuse in the collagen framework of the superficial layer, but showed accumulation in the deep layer where a clear line of demarcation between the collagen framework and crystals was seen. 3) The crystals in the meniscus were rod, granular or rectangular in shape, and 0.2-6.5 micro by 0.2-3.5 micro in size. Crystals from the articular cartilage were granular or rod-like in shape, and 0.2-3.5 micro by 0.2-1.0 micro in size. Most of the crystals found in the synovial fluid were rod-shaped. 4) X-ray microanalysis of the meniscus crystals by EMMA showed the same pattern of PK alpha, CaK alpha, and CaK beta content as that of CPPD crystals commercially available. The P/Ca ratio was about 0.7. 5) SEM and EMMA examination can be very useful for accurate identification of the form and content of the tiny crystals in joint tissues and synovial fluid. This can also be useful in proving a diagnosis of crystal-induced synovitis.

Topics: Calcinosis; Calcium Pyrophosphate; Cartilage, Articular; Chondrocalcinosis; Crystallization; Diphosphates; Humans; Menisci, Tibial; Microscopy, Electron, Scanning; Synovial Fluid

Both disodium pyrophosphate and disodium ethane-hydroxy-1, 1-diphosphate inhibit the reaction of simple calcergy induced in the mouse by lead acetate. The pyrophosphate is effective only by a direct interaction with the lead salt and the disphosphonate is effective only before the occurrence of histochemically demonstrable calcification.

Topics: Animals; Calcinosis; Diphosphates; Etidronic Acid; Lead; Male; Mice; Skin; Time Factors

A 48-year-old white man with Hodgkin's disease was referred for bone imaging. There was intense accumulation of the bone imaging agent in the stomach and in the region of the upper lobe of the right lung. Subsequent biopsy and histological examination revealed that there was amorphous calcifications in the mucosal layer of the stomach. Possible causes for this calcification are discussed.

Topics: Calcinosis; Diphosphates; Humans; Male; Middle Aged; Radionuclide Imaging; Stomach Diseases; Technetium

Technetium-99m stannous pyrophosphate scintiscanning was performed in 22 patients with radiographically detected calcification within the cardiac silhouette. All but one of these scintigrams showed a localised area of increased activity similar to that ordinarily seen in acute myocardial infarction. Scintiscans in 3 patients after removal of the calcified aortic valve reverted to negative. It was concluded that this technique for acute infarct detection may yield false positive results in the presence of cardiac calcification.

Topics: Calcinosis; Cardiomyopathies; Diphosphates; False Positive Reactions; Humans; Myocardial Infarction; Radionuclide Imaging; Technetium

Metastatic soft tissue calcification is known to occur in hypercalcemia and is usually present in the kidneys, stomach and lungs. 1--3 This case presents two unusual features: 1) ectopic parathormone production in association with poorly differentiated lymphocytic lymphoma; and and 2) uptake of 99mTc-pyrophosphate in the liver in the absence of demonstrable abnormality at autopsy. The more usual sites of metastatic calcification also showed uptake of the radionuclide. We will discuss metastatic soft tissue calcification, ectopic parathyroid hormone production, hypercalcemia in malignancy and bone scan agent localization in soft tissues.

Topics: Aged; Bone Neoplasms; Calcinosis; Diphosphates; Female; Hormones, Ectopic; Humans; Hypercalcemia; Liver; Lymphoma, Non-Hodgkin; Neoplasm Metastasis; Parathyroid Hormone; Radionuclide Imaging; Technetium

Topics: Adult; Calcinosis; Cardiomyopathies; Chronic Kidney Disease-Mineral and Bone Disorder; Diphosphates; Humans; Kidney Transplantation; Lung Diseases; Male; Parathyroid Glands; Radionuclide Imaging; Technetium; Transplantation, Homologous

Technetium-99m pyrophosphate (PPi) is currently considered the best scanning agent for the diagnosis of acute myocardial infarction. False-positive scans have been reported in association with unstable angina, alcoholic cardiomyopathy, and ventricular aneurysms. In this study, 86% of patients (12/14) with either calcific aortic or mitral valvular heart disease had positive PPi cardiac scintiscans and the location of the PPi uptake was limited to the calcific valve in all (9/9) of the patients who underwent valve replacement surgery. Six patients with valvular disease without radiologic evidence of calcium had negative PPi heart images. Three of these patients had surgical valve replacement, and in none was there increased uptake in the resected valve. Seventy-five percent of the patients with calcified aortic valves had localization of the PPi activity to the area of the aortic valve, whereas 50% of the patients with calcified mitral valves showed a diffuse pattern of uptake on the cardiac image. In vitro demonstration of increased radioactivity in surgically removed cardiac valves warrants the conclusion that Tc-99m PPi is taken up by calcified heart valves. We conclude that while PPi heart scanning is a sensitive indicator of acute myocardial infarction, false-positive scans can occur in the presence of calcific valvular disease, due to localization of PPi in the calcified portion of the valve.

Topics: Adolescent; Adult; Aged; Aortic Valve; Calcinosis; Diphosphates; False Positive Reactions; Female; Heart Valve Diseases; Humans; Male; Middle Aged; Mitral Valve; Myocardial Infarction; Radionuclide Imaging; Technetium

A case of tumoral calcinosis with tumoral deposits about the knee is reported. Radiographs demonstrate juxta-articular calcific deposits about the right second and fifth distal interphalangeal joints and the left first distal tuft, both hips, both shoulders, first distal phalanx of the left foot and right knee. Radionuclide images clearly demonstrate all areas of tumoral calcinosis.

Topics: Calcinosis; Diphosphates; Foot; Hand; Humans; Knee; Male; Middle Aged; Pelvic Bones; Radiography; Radionuclide Imaging; Shoulder; Technetium

The inorganic constituents and crystalline features of extraosseous calcium-phosphate deposits obtained from dialyzed uremic and hypercalcemic patients were studied. Visceral calcification (heart, lung, and kidney) in hypercalcemic patients exhibited either an amorphous or apatitic X-ray diffraction pattern. Uremic visceral calcification consistently gave an amorphous diffraction pattern. Although the calcium content of uremic and hypercalcemic visceral deposits was similar, other inorganic constituents were different. The mean pyrophosphate was 11 +/- 11.8 and magnesium 4.91 +/- 3.86 mg/g in the uremic group as compared to 0.92 +/- 0.24 and 1.36 +/- 1.26 mg/g in the hypercalcemic group (P less than 0.025). After incineration hypercalcemic visceral deposits having an amorphous diffraction pattern were found to generate pyrophosphate supporting the presence of brushite in these deposits. The small amount of pyrophosphate in apatitic deposits from both uremic and hypercalcemic patients actually decreased after incineration and the pyrophosphate content of uremic visceral deposits was unchanged by incineration. It is concluded that in hypercalcemic patients the initial visceral deposit is brushite which is subsequently transformed to apatite. Arterial and tumoral calcium-phosphate deposits in uremic patients were also apatite. Uremic visceral calcium-phosphate deposits are an unique mineral high in magnesium with approximately 30% of the phosphorus present as pyrophosphate. The high pyrophosphate content of these deposits could alter their crystalline structure and prevent the transformation to apatite. The infrared features, high magnesium content of the deposit, and resistance of pyrophosphate in the deposit to hydrolysis by pyrophosphatase suggests that the pyrophosphate may be deposited as the magnesium salt.

Topics: Apatites; Calcinosis; Calcium; Calcium Phosphates; Chemical Phenomena; Chemistry; Diphosphates; Humans; Hypercalcemia; Magnesium; Uremia; X-Ray Diffraction

The mean bone pyrophosphate was 0.360 +/- 0.15 mg/g in 8 controls and 1.22 +/- 1.39 mg/g bone in 27 uremic patients (P less than 0.0025). 13 of the 27 uremic patients had bone pyrophosphate levels greater than 2 SD above control values. The ash content of uremic bones with increased pyrophosphate levels (group II) was 56 +/- 9% as compared to 64 +/- 2% in control bones (P less than 0.01) and 60 +/- 7% in uremic bones having normal pyrophosphate levels (P less than 0.1) (group I). The magnesium content of bones in group II was 338 +/- 47 as compared to 211 +/- 13 (P less than 0.0005) in the controls and 294 +/- 73 mmol/kg ash (P less than 0.05) in group I. In group II, but not group I, there was a significant inverse correlation between duration of dialysis and percent bone ash (r = -0.59) (P less than 0.05). A definite relationship existed between elevated bone pyrophosphate levels and soft tissue calcification. In group II the mean pulmonary calcium content was 530 +/- 459 as compared to 32 +/- 26 mmol/kg/ash in group I (P less than 0.0025). All patients with a bone pyrophosphate level greater than 1.4 mg/g bone had extensive pulmonary calcification. It is concluded that the excess bone pyrophosphate present in some uremic patients is either deposited in the apatite crystal in the transphosphorylated form or else as the magnesium salt since the pyrophosphate is resistant to pyrophosphatase and surface adsorption of pyrophosphate is not altered by the increased bone pyrophosphate levels. The excess bone pyrophosphate could disturb bone calcification mechanisms in uremic patients. The association between increased bone pyrophosphate and soft tissue calcification suggests that the disordered pyrophosphate metabolism may be important in the pathogenesis of extraosseous calcification.

Topics: Binding Sites; Bone and Bones; Calcinosis; Calcium Phosphates; Diphosphates; Humans; Lung; Myocardium; Phosphorus; Pyrophosphatases; Uremia

Uptake of 99mTc bone-scanning agent into lungs containing metastatic calcification was demonstrated in a patient with a carcinosarcoma of the bladder. This gives further support to the hypothesis that 99mTc bone agents are associated with hydroxyapatite.

Topics: Bone Neoplasms; Calcinosis; Carcinosarcoma; Diphosphates; Humans; Lung Diseases; Male; Middle Aged; Phosphates; Radionuclide Imaging; Technetium; Urinary Bladder Neoplasms

A whole-body scan with 99mTc-pyrophosphate and 85Sr-nitrate demonstrates extension of calcinosis in one case of dermatomyositis with cutaneous, subcutaneous, and muscular calcinosis. The authors suggest the potential use of 99mTc-phosphate compounds as an auxiliary instrument in the evaluation of dermatomyositis-polymyositis syndrome.

Topics: Adult; Calcinosis; Dermatomyositis; Diphosphates; Female; Humans; Radiography; Radionuclide Imaging; Technetium

Topics: Adult; Calcinosis; Collagen; Diagnosis, Differential; Diphosphates; Gout; Hand; Humans; Knee; Male; Middle Aged; Radiography; Uric Acid

Topics: Bone and Bones; Calcinosis; Calcium; Diphosphates; Fluorides; Humans; Lung Diseases; Phosphoric Monoester Hydrolases; Pulmonary Fibrosis; Radioisotopes; Radionuclide Imaging; Strontium Radioisotopes; Technetium

Topics: Arm; Bursitis; Calcinosis; Calcium; Chondrocalcinosis; Collagen Diseases; Diphosphates; Epidermolysis Bullosa; Gout; Humans; Joint Diseases; Leg; Lipodystrophy; Periarthritis; Radiography; Rupture; Synovial Cyst; Synovial Membrane; Tendon Injuries

Topics: Aged; Arthropathy, Neurogenic; Calcinosis; Calcium Phosphates; Diphosphates; Female; Humans; Knee Joint; Male; Middle Aged; Radiography; Synovial Fluid; Syphilis, Latent; Tabes Dorsalis

Topics: Calcinosis; Diphosphates; Humans; Peritoneal Dialysis; Renal Dialysis

Topics: Calcinosis; Calcium Phosphates; Chondrocalcinosis; Diphosphates; Elbow Joint; Hip Joint; Humans; Hydroxyapatites; Intervertebral Disc; Knee Joint; Pubic Symphysis; Radiography; Shoulder Joint; Tarsal Joints; Tendinopathy; Tendons; Toe Joint; Uric Acid; Wrist Joint

Topics: Age Factors; Alkaline Phosphatase; Calcification, Physiologic; Calcinosis; Diphosphates; Hemochromatosis; Humans; Iron; Joint Diseases

Topics: Adolescent; Adult; Aged; Alkaline Phosphatase; Arthritis; Calcinosis; Calcium; Chromatography, Ion Exchange; Crystallization; Diphosphates; Electrophoresis; Female; Humans; Hydrolysis; Ion Exchange; Joint Diseases; Male; Middle Aged; Phosphates; Phosphorus Isotopes; Radioisotope Dilution Technique; Solubility; Synovial Fluid

Topics: Animals; Bone and Bones; Calcinosis; Calcium Phosphates; Diphosphates; Joint Diseases; Osteoarthritis; Rabbits; Radiography; Synovial Fluid

Topics: Aged; Alkaline Phosphatase; Calcinosis; Chromatography, Ion Exchange; Diphosphates; Female; Humans; Joint Diseases; Male; Middle Aged; Synovial Fluid

Topics: Aged; Calcinosis; Calcium Phosphates; Diagnosis, Differential; Diphosphates; Female; Gout; Humans; Joint Diseases; Knee Joint; Male; Middle Aged; Synovial Fluid; Synovitis

Topics: Calcinosis; Diphosphates; Humans; Osteoarthritis; Synovial Fluid; Synovitis

Topics: Acromegaly; Adult; Calcinosis; Calcium Phosphates; Cartilage Diseases; Diagnosis, Differential; Diphosphates; Gout; Hemochromatosis; Humans; Hyperparathyroidism; Joints; Male; Microscopy, Polarization; Middle Aged; Radiography; Terminology as Topic

Topics: Aged; Blood Sedimentation; Calcinosis; Calcium Phosphates; Diphosphates; Female; Hematocrit; Humans; Inhalation; Joint Diseases; Joints; Knee; Leukocyte Count; Male; Middle Aged; Punctures; Radiography; Synovial Fluid; Uric Acid; Wrist

Topics: Animals; Aorta; Arteries; Calcinosis; Coronary Vessels; Dihydrotachysterol; Diphosphates; Female; Glycerophosphates; Histological Techniques; Injections, Intraperitoneal; Injections, Subcutaneous; Kidney; Myocardium; Nephrocalcinosis; Phosphates; Phosphoric Monoester Hydrolases; Pulmonary Artery; Rats; Vascular Diseases

Topics: Aged; Calcinosis; Calcium; Diphosphates; Female; Humans; Joint Diseases; Male; Radiography

Two diphosphonates containing the P-C-P bond, CH(3)C(OH)(PO(3)HNa)(2) and H(2)C(PO(3)HNa)(2), inhibit the crystallization of calcium phosphate in vitro and prevent aortic calcification of rats given large amounts of vitamin D(3). The diphosphonates therefore have effects similar to those described for compounds containing the P-O-P bond but are active when administered orally.

Topics: Animals; Aortic Diseases; Calcinosis; Cholecalciferol; Crystallization; Diphosphates; Hydrogen-Ion Concentration; Organophosphonates; Phosphates; Rats; X-Ray Diffraction

Topics: Aged; Arthritis, Rheumatoid; Calcinosis; Diagnosis, Differential; Diphosphates; Female; Humans; Hyperglycemia; Joint Diseases; Knee Joint; Middle Aged; Radiography; Synovial Fluid; Wrist Joint

Topics: Adenoma; Aged; Calcinosis; Calcium; Carpal Tunnel Syndrome; Diphosphates; Gout; Humans; Hyperparathyroidism; Male; Mediastinal Neoplasms; Parathyroid Neoplasms; Photomicrography; Synovial Fluid; Tendons; Ulna; Wrist

Topics: Animals; Aorta; Calcinosis; Calcium Phosphates; Culture Techniques; Depression, Chemical; Diphosphates; Mice; Models, Biological; Nephrocalcinosis; Organophosphonates; Rats

Topics: Animals; Aorta, Thoracic; Aortic Diseases; Calcinosis; Cholecalciferol; Diphosphates; Female; Hypercalcemia; Kidney; Phosphates; Rats

Topics: Animals; Aortic Diseases; Bone Resorption; Calcinosis; Calcium Phosphates; Chemical Phenomena; Chemical Precipitation; Chemistry; Cholecalciferol; Diphosphates; Hypercalcemia; Mice; Organophosphonates; Pyrophosphatases; Rats

Topics: Calcinosis; Cartilage; Diagnosis, Differential; Diphosphates; Gout; Humans; Radiography; Technology, Radiologic

Topics: Alkaline Phosphatase; Animals; Calcinosis; Calciphylaxis; Diphosphates; Female; Male; Potassium Permanganate; Radiography; Rats; Skin Diseases

Topics: Animals; Calcinosis; Calcium; Dihydrotachysterol; Diphosphates; Female; Hypercalcemia; Parathyroid Hormone; Rats; Skin

Topics: Adenosine Triphosphate; Animals; Calcinosis; Citrates; Diphosphates; Lead; Phosphates; Polymyxins; Rats; Skin Diseases

Topics: Animals; Calcinosis; Diphosphates; Female; Metals; Rats

Topics: Arthritis; Calcinosis; Calcium; Cartilage, Articular; Chondrocalcinosis; Diagnosis, Differential; Diphosphates; Gout; Humans; Hyaline Cartilage; Joint Diseases; Knee Joint

Topics: Arthritis; Arthritis, Rheumatoid; Calcinosis; Calcium Phosphates; Cartilage; Cartilage, Articular; Chondrocalcinosis; Classification; Diagnosis, Differential; Diphosphates; Geriatrics; Gout; Humans; Joint Diseases; Knee; Lupus Erythematosus, Systemic; Pathology; Radiography; Rheumatic Diseases; Synovial Fluid

Topics: Arthritis; Calcinosis; Chondrocalcinosis; Diphosphates; Humans; Rheumatic Diseases; Synovitis

Topics: Alkaline Phosphatase; Calcification, Physiologic; Calcinosis; Chromatography; Diphosphates; Fluids and Secretions; Hypophosphatasia; Metabolism, Inborn Errors; Phosphorus Isotopes; Urine

Topics: Animals; Aortic Diseases; Calcinosis; Diphosphates; Phosphates; Rats; Vitamin D

Topics: Animals; Calcification, Physiologic; Calcinosis; Chick Embryo; Culture Media; Diphosphates; Femur; In Vitro Techniques; Pharmacology; Polyphosphates; Research

Topics: Calcification, Physiologic; Calcinosis; Diphosphates; Humans

Topics: Calcification, Physiologic; Calcinosis; Calcium; Calcium, Dietary; Diphosphates; Humans; Urine

Topics: Bone and Bones; Calcinosis; Diphosphates; Humans; Minerals; Retinal Degeneration