elastin and Marfan-Syndrome

1. Arterial stiffness, which has independent predictive value for cardiovascular events, seems to have a genetic component, largely independent of the influence of blood pressure and other cardiovascular risk factors. 2. In animal models of essential hypertension (stroke-prone spontaneously hypertensive rats and spontaneously hypertensive rats), structural modifications of the arterial wall include an increase in the number of elastin-smooth muscle cell connections and smaller fenestrations of the internal elastic lamina, possibility leading to redistribution of the mechanical load towards elastic materials. These modifications may give rise to mechanisms explaining why changes in arterial wall material accompanying wall hypertrophy in these animals are not associated with an increase in arterial stiffness. 3. In monogenic connective tissue diseases (Marfan, Williams and Ehlers-Danlos syndromes) and the corresponding animal models, precise characterization of the arterial phenotype makes it possible to determine the influence of abnormal, genetically determined, wall components on arterial stiffness. 4. Such studies have highlighted the role of extracellular matrix signalling in the vascular wall and have shown that elastin and collagen not only display elasticity or rigidity, but are also involved in the control of smooth muscle cell function. 5. These data provide strong evidence that arterial stiffness is affected by the amount and density of stiff wall material and the spatial organization of that material.

Topics: Animals; Arteries; Cardiovascular Diseases; Collagen; Compliance; Disease Models, Animal; Ehlers-Danlos Syndrome; Elastin; Extracellular Matrix; Gene Expression Profiling; Genetic Predisposition to Disease; Humans; Hypertension; Marfan Syndrome; Oligonucleotide Array Sequence Analysis; Polymorphism, Genetic; Risk Factors; Tunica Intima; Tunica Media; Williams Syndrome

Sleep apnea syndrome (SAS) is a disease characterized by recurrent complete or partial upper airway obstructions during sleep. The majority of patients with SAS demonstrate this obstruction either at the nasopharynx or the oropharynx. Risk factors for SAS include obesity, male gender, upper airway abnormalities, alcohol use, snoring, and neck girth of more than 17 in. in men or 16 in. in women. Reported ophthalmic findings in patients with SAS include floppy eyelid syndrome (FES), glaucoma, and non-arteritic anterior ischemic optic neuropathy (NAION).

Topics: Anti-Bacterial Agents; Continuous Positive Airway Pressure; Elastin; Erythromycin; Eye; Eyelid Diseases; Glaucoma; Humans; Marfan Syndrome; Optic Nerve; Optic Neuropathy, Ischemic; Sleep Apnea, Obstructive

Elastic fibres are a major class of extracellular matrix fibres that are abundant in dynamic connective tissues such as arteries, lungs, skin and ligaments. Their structural role is to endow tissues with elastic recoil and resilience. They also act as an important adhesion template for cells, and they regulate growth factor availability. Mutations in major structural components of elastic fibres, especially elastin, fibrillins and fibulin-5, cause severe, often life-threatening, heritable connective tissue diseases such as Marfan syndrome, supravalvular aortic stenosis and cutis laxa. Elastic-fibre function is also frequently compromised in damaged or aged elastic tissues. The ability to regenerate or engineer elastic fibres and tissues remains a significant challenge, requiring improved understanding of the molecular and cellular basis of elastic-fibre biology and pathology, and ability to regulate the spatiotemporal expression and assembly of its molecular components.

Topics: Animals; Aortic Stenosis, Supravalvular; Connective Tissue; Connective Tissue Diseases; Elastic Tissue; Elastin; Extracellular Matrix; Extracellular Matrix Proteins; Fibrillins; Humans; Marfan Syndrome; Mice; Microfilament Proteins; Models, Biological; Recombinant Proteins; Time Factors; Tissue Distribution

Every day, the emerging fields of genomics and proteomics provide new information about both normal and pathological processes, among which, the extracellular matrix appears to play a significant role. Over the past decade, the classic fibrillar components of the matrix, collagen and elastin, have been the subject of extensive research leading to a wealth of information which is far form being fully interpreted. Although the basic composition and structure of the matrix components has been well established, today more than twenty five different varieties of collagen have been described, and elastic fibers are currently described as polymeric complexes, composed of at least 19 different proteins in their microfibrillar and amorphic portions. Mutations in three of the genes coding for some of the most abundant proteins in the elastic fibers give rise to a wide range of elastic tissue phenotypes, from skeletal or dermal anomalies to vascular or ocular defects. In this review, our aim was to gain insight into the fibrillar component of the extracellular matrix in an attempt to improve our understanding of certain ocular disorders.

Topics: Collagen; Connective Tissue; Elastic Tissue; Elastin; Extracellular Matrix; Eye; Humans; Marfan Syndrome

Supravalvular aortic stenosis (SVAS), Marfan syndrome (MFS) and Ehlers-Danlos syndrome type IV (EDS IV) are three clinical entities characterized by vascular abnormalities that result from mutations of structural components of the extracellular matrix (ECM). Analyses of naturally occurring human mutations and of artificially generated deficiencies in the mouse have provided insights into the pathogenesis of these heritable disorders of the connective tissue. SVAS is associated with haploinsufficiency of elastin, one of the two major components of the elastic fibers. SVAS is characterized by narrowing of the arterial lumen due to the failure of regulation of cellular proliferation and matrix deposition. Mutations in fibrillin 1 are the cause of dissecting aneurysm leading to rupture of the ascending aorta. Fibrillin-1 is the building block of the microfibrils that span the entire thickness of the aortic wall and are a major component of the elastic fibers that reside in the medial layer. The vascular hallmark of EDS IV is rupture of large vessels. The phenotype is caused by mutations in type III collagen. The mutations ultimately affect the overall architecture of the collagenous network and the biomechanical properties of the adventitial layer of the vessel wall. Altogether, these genotype-phenotype correlations document the diversified contributions of distinct extracellular macroaggregates to the assembly and function of the vascular matrix.

Topics: Animals; Aortic Stenosis, Supravalvular; Blood Vessels; Collagen; Ehlers-Danlos Syndrome; Elastin; Extracellular Matrix; Extracellular Matrix Proteins; Fibrillin-1; Fibrillins; Humans; Marfan Syndrome; Mice; Microfibrils; Microfilament Proteins; Mutation; Vascular Diseases

Over the last decade, a considerable amount of new information has emerged describing the protein components of elastic fibers. It is now evident that elastic fibers are complex extracellular matrix polymers, composed of at least 19 different proteins that comprise both the microfibrillar and the amorphous components of elastic fibers. Mutations in three of the genes encoding the most abundant of these elastic fiber proteins result in a broad spectrum of elastic tissue phenotypes, ranging from skeletal and skin abnormalities to vascular and ocular defects. The following disorders will be discussed in this review: supravalvular aortic stenosis; Williams-Beuren syndrome; cutis laxa; Marfan syndrome; ectopia lentis; familial thoracic aortic aneurysms and dissections; MASS syndrome; isolated skeletal features of Marfan syndrome; Shprintzen-Goldberg syndrome; and congenital contractural arachnodactyly.

Topics: Aortic Stenosis, Supravalvular; Connective Tissue Diseases; Cutis Laxa; Elastic Tissue; Elastin; Extracellular Matrix Proteins; Fibrillins; Humans; Marfan Syndrome; Microfilament Proteins; Mutation; Phenotype

The inability to study appropriate human tissues at various stages of development has precluded the elaboration of a thorough understanding of the pathogenic mechanisms leading to diseases linked to mutations in genes for elastic fiber proteins. Recently, new insights have been gained by studying mice harboring targeted mutations in the genes that encode fibrillin-1 and elastin. These genes have been linked to Marfan syndrome (MFS) and supravalvular aortic stenosis (SVAS), respectively. For fibrillin-1, mouse models have revealed that phenotype is determined by the degree of functional impairment. The haploinsufficiency state or the expression of low levels of a product with dominant-negative potential from one allele is associated with mild phenotypes with a predominance of skeletal features. Exuberant expression of a dominant-negative-acting protein leads to the more severe MFS phenotype. Mice harboring targeted deletion of the elastin gene (ELN) show many of the features of SVAS in humans, including abnormalities in the vascular wall and altered hemodynamics associated with changes in wall compliance. The genetically altered mice suggest that SVAS is predominantly a disease of haploinsufficiency. These studies have underscored the prominent role of the elastic matrix in the morphogenesis and homeostasis of the vessel wall.

Topics: Animals; Aortic Stenosis, Supravalvular; Connective Tissue Diseases; Disease Models, Animal; Elastin; Extracellular Matrix Proteins; Fibrillin-1; Fibrillins; Humans; Marfan Syndrome; Mice; Microfilament Proteins; Models, Genetic; Mutation

Topics: Actin Cytoskeleton; Amino Acid Sequence; Connective Tissue; Connective Tissue Diseases; Elastin; Extracellular Matrix Proteins; Fibrillins; Humans; Marfan Syndrome; Microfilament Proteins; Molecular Sequence Data; Sequence Homology, Amino Acid

The Marfan syndrome (MFS) is a heritable connective tissue disorder manifested by defects in the skeletal, ocular, and cardiovascular systems. It is inherited as an autosomal dominant trait, with an incidence of nearly one per 10,000 population without gender or ethnic predilection. About 30% of MFS cases are sporadic, representing new dominant mutations. Although diagnostic criteria may be met, intra- and inter-familial variability in syndromic expression can be quite marked. Life expectancy is significantly reduced, and more than 85% of patients die of cardiovascular complications. Elastin-associated microfibrils are classically identified by a 10-12 nm cross-sectional diameter and close association with amorphous elastin. Characteristically, these microfibrils are seen as a fringe surrounding elastin cores. Despite their name, these fibrils are frequently localized in tissues not associated with elastin. One of the major and best characterized microfibrillar proteins is the glycoprotein, fibrillin. Fibrillin is rich in cysteine residues and thus, extensively intrachain disulfide bonded. Defects in fibrillin are now known to cause the variable and pleiotropic manifestations of MFS. Immunofluorescence studies of skin sections and dermal fibroblast cultures were the first to show this association. The cloning and sequencing of the entire fibrillin coding region has enabled the identification of the myriad of mutations that cause MFS. Identification of the molecular lesions covering the gamut of MFS clinical variability should allow the construction of genotype/phenotype correlations. It is hoped that once available, they may become of prognostic value in the clinical management of MFS.

Topics: Actin Cytoskeleton; Elastin; Extracellular Matrix Proteins; Fibrillins; Fluorescent Antibody Technique; Genes; Humans; Marfan Syndrome; Microfilament Proteins; Skin

Several inherited syndromes characterized by abnormal elastic fibers decreased in number and size could be collected under the heading of inherited elastolysis. This morphological concept does not prejudge the causal mechanisms of the elastolysis involving dermis and/or other organs. The elastic fibers anomalies result mainly from elastin crosslinking defects, developmental disturbances or excessive proteolysis.

Topics: alpha 1-Antitrypsin Deficiency; Ehlers-Danlos Syndrome; Elastin; Homocystinuria; Humans; Marfan Syndrome; Menkes Kinky Hair Syndrome; Skin; Skin Diseases

The elastic properties of many tissues such as the lung, dermis, and large blood vessels are due to the presence of elastic fibers in the extracellular space. These fibers have been shown by biochemical and ultrastructural analysis to be comprised of two distinct components, a more abundant amorphous component and the microfibrillar component. The microfibrillar component is found in 10- to 12-nm fibrils which are located primarily around the periphery of the amorphous component but, to some extent, interspersed within it. The protein, elastin, makes up the highly insoluble amorphous component and is responsible for the elastic properties. Elastin is found throughout the vertebrate kingdom except for very primitive fish and possesses an unusual chemical composition consonant with its characteristic physical properties. Elastin is composed largely of glycine, proline, and other hydrophobic residues and contains multiple lysine-derived cross-links, such as the desmosines, which link the individual polypeptide chains into a rubber-like network. The intervening, hydrophobic regions of the polypeptide chains between the cross-links are highly mobile, and the elastic properties of the fibers can be described in terms of the theory of rubber elasticity. Recent application of recombinant DNA techniques has led to further understanding of the structure of elastin. Analyses of the bovine and human elastin genes have demonstrated that the hydrophobic and cross-linking domains are encoded in separate exons. These exons tend to be small, varying from 27 to 114 base pairs, and are separated by large intervening sequences. Furthermore, DNA sequence analysis has demonstrated that the elastin molecule contains two cysteine residues which were not previously identified near the carboxy terminus and which may be important in the interaction of elastin with other extracellular matrix proteins. Further DNA sequencing should determine the complete amino acid sequence of elastin. Biosynthetic studies and in vitro translation of elastin mRNA have demonstrated that a 72,000-dalton polypeptide, designated tropoelastin, is the initial translation product. Analysis of several developing systems has demonstrated that elastin synthesis is controlled by the level of elastin mRNA. After packaging into membrane-bound vesicles in the Golgi apparatus, tropoelastin is secreted by exocytosis into the extracellular space where it is cross-linked by a copper-requiring extracellular enzyme, lys

Topics: Amino Acid Sequence; Amino Acids; Animals; Aorta; Base Sequence; Biological Evolution; Bone Diseases; Chemical Phenomena; Chemistry; Cutis Laxa; DNA; Elastin; Genes; Genetic Diseases, Inborn; Humans; Lung Diseases, Obstructive; Macromolecular Substances; Marfan Syndrome; Microscopy, Electron; Protein-Lysine 6-Oxidase; Pseudoxanthoma Elasticum; RNA, Messenger; Species Specificity; Syndrome; Tropoelastin; Vascular Diseases

Topics: Collagen; Connective Tissue Diseases; Cutis Laxa; Ehlers-Danlos Syndrome; Elastin; Fibronectins; Humans; Marfan Syndrome; Metabolism, Inborn Errors; Osteogenesis Imperfecta; Prenatal Diagnosis; Proteoglycans; Skin

The elastic fibers present in various connective tissues of the body are responsible for physiologic elasticity of the organs. These fibers consist of 2 distinct components, elastin and the elastic fiber microfibrils. Controlled synthesis and balanced interaction of these 2 components are essential for normal fibrillogenesis. The intracellular biosynthesis of elastin by connective tissue cells, such as smooth muscle cells, involves assembly of the polypeptide chains on the membrane-bound ribosomes, hydroxylation of some prolyl residues to hydroxyproline, and secretion of the polypeptides packaged in Golgi vacuoles. In the extracellular space the elastin molecules assemble into fiber structures which are stabilized by the synthesis of complex covalent cross-links, desmosines. Recently, aberrations in the structure or metabolism of elastin have been detected in a variety of heritable and acquired diseases affecting skin and other connective tissues. These conditions include pseudoxanthoma elasticum, cutis laxa, and elastosis perforans serpiginosa, as well as arteriosclerosis and other degenerative changes of the vascular connective tissues.

Topics: Amino Acids; Arteriosclerosis; Chemical Phenomena; Chemistry; Collagen Diseases; Connective Tissue; Contractile Proteins; Cutis Laxa; Desmosine; Ehlers-Danlos Syndrome; Elastic Tissue; Elastin; Female; Glycoproteins; Humans; Hydroxyproline; Marfan Syndrome; Menkes Kinky Hair Syndrome; Muscle Proteins; Pancreatic Elastase; Peptide Biosynthesis; Protein Precursors; Pseudoxanthoma Elasticum; X Chromosome

It is apparent that significant progress has been made in our understanding of the biosynthesis, modifications, and maturation of collagen and elastin. We now recognize and partially understand special reactions involved in hydroxylations within the cell and complex cross-linking processes occurring outside the cell. Recent experiments (191) have shown that in human diploid fibroblast cultures of limited doubling potential (191) the hydroxylation of collagen prolyl residues appears to be "age" or passage-level dependent. With increasing passage level of these cultures, both the ascorbate requirements and the extent of collagen hydroxylation decrease. "Young" cell cultures have a strong requirement for complete hydroxylation and without ascorbate there is only about 50% of the normal level. "Middle-aged" cultures show higher hydroxylation without and full hydroxylation with ascorbate, whereas "old" (or cultures close to "senescence") are incapable of full hydroxylation with or without ascorbic acid. Although the overall system may show some deterioration with increasing passage levels, it appears that with increasing passage levels other components in the cell replace the ascorbate dependence of the hydroxylase system to a greater exten. In some ways, aging WI-38 cultures begin to resemble some transformed cells in their biochemical reactions, although they continue to remain diploid and eventually lose the ability to replicate. It is not yet known whether old animals can produce collagen, which may now be underhydroxylated, perhaps contributing to certain senescent changes. Careful examination of the hydroxylation index of collagen produced in organoid cultures of tissue biopsies as a function of donor age might be informative, particularly if one looks at the quality of collagen by employing collagenase and other proteolytic digests with collagen (191). One could comare the levels of frequent and characteristic peptide triplet sequences such as Gly-Pro-Hyp to Gly-Pro-Pro, Gly-Ala-Hyp to Gly-Ala-Pro, or Gly-Pro-Hyl to Gly-Pro-Lys and others for evaluation of hydroxylation throughout the entire molecule or at selected sequences.

Topics: Amino Acid Sequence; Animals; Antibody Specificity; Ascorbic Acid; Collagen; Connective Tissue; Copper; Ehlers-Danlos Syndrome; Elastin; Epitopes; Homocystinuria; Humans; Hydralazine; Lathyrism; Marfan Syndrome; Molecular Conformation; Platelet Aggregation; Procollagen-Proline Dioxygenase; Skin Diseases; Syndrome

Topics: Animals; Basement Membrane; Cattle; Collagen; Connective Tissue; Ehlers-Danlos Syndrome; Elastin; Epidermolysis Bullosa; Fibroblasts; Glycopeptides; Humans; Keloid; Lysine; Marfan Syndrome; Metabolism, Inborn Errors; Microbial Collagenase; Mixed Function Oxygenases; Progeria; Protein Biosynthesis; Pseudoxanthoma Elasticum; Wound Healing

Topics: Aging; Amino Acids; Aneurysm; Animals; Arteriosclerosis; Brain Diseases; Copper; Deficiency Diseases; Elastic Tissue; Elastin; Endocardial Fibroelastosis; Growth Disorders; Hair; Humans; Inflammation; Lathyrism; Marfan Syndrome; Metabolic Diseases; Respiratory Tract Diseases; Skin Diseases

Marfan syndrome (MFS) is associated with TGF (transforming growth factor) β-stimulated ERK (extracellular signal-regulated kinase) activity in vascular smooth muscle cells (VSMCs), which adopt a mixed synthetic/contractile phenotype. In VSMCs, TGFβ induces IL (interleukin) 11) that stimulates ERK-dependent secretion of collagens and MMPs (matrix metalloproteinases). Here, we examined the role of IL11 in the MFS aorta.. We used echocardiography, histology, immunostaining, and biochemical methods to study aortic anatomy, physiology, and molecular endophenotypes in. In MFS, IL11 is upregulated in aortic VSMCs to cause ERK-related thoracic aortic dilatation, inflammation, and fibrosis. Therapeutic inhibition of IL11, imminent in clinical trials, might be considered as a new approach in MFS.

Topics: Animals; Antibodies, Neutralizing; Aorta; Aortic Diseases; Disease Models, Animal; Elastin; Fibrosis; Immunoglobulin G; Inflammation; Interleukin-11; Interleukin-11 Receptor alpha Subunit; Marfan Syndrome; Matrix Metalloproteinase 2; Mice; Muscle, Smooth, Vascular; Receptors, Interleukin-11; Transforming Growth Factor beta

The leading cause of mortality in patients with Marfan syndrome (MFS) is thoracic aortic aneurysm and dissection. Notch signaling is essential for vessel morphogenesis and function. However, the role of Notch signaling in aortic pathology and aortic smooth muscle cell (SMC) differentiation in Marfan syndrome (MFS) is not completely understood.. RNA-sequencing on ascending aortic tissue from a mouse model of MFS,. The murine RNA-sequencing data were validated with mouse and human MFS aortic tissue, demonstrating elevated Notch3 activation in MFS. Data further revealed that upregulation and activation of Notch3 were concomitant with increased expression of SMC contractile markers. Inhibiting Notch3 activation with DAPT attenuated aortic enlargement and improved survival of. Our data demonstrated that matrix abnormalities in the aorta of MFS are associated with increased Notch3 activation. Enhanced Notch3 activation in MFS contributed to aortic aneurysm formation in MFS. This might be mediated by inducing a contractile phenotypic change of SMC. Our results suggest that inhibiting Notch3 activation may provide a strategy to prevent and treat aortic aneurysms in MFS.

Topics: Animals; Aorta; Aortic Aneurysm; Diamines; Disease Models, Animal; Elastin; Fibrillin-1; Humans; Marfan Syndrome; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Molecular Targeted Therapy; Myocytes, Smooth Muscle; Receptor, Notch3; Thiazoles

Fragile X syndrome (FXS) is an inherited genetic condition that is the leading known cause of inherited intellectual developmental disability. Phenotypically, individuals with FXS also present with distinct physical features including, elongated face, prominent ears, pectus excavatum, macroorchidism, and joint laxity, which suggests connective tissue dysplasia. In addition to mitral valve prolapse, aortic dilatation has been identified within individuals with FXS. Abnormal elastin fiber networks have been found in the skin, valves, and aorta in individual cases. Aortic dilatation has been described in other connective tissue disorders, particularly Marfan syndrome. However, while aortic aneurysms are characteristic of Marfan syndrome, no similar cases have been reported in FXS patients to date. This case report details the presentation of two patients with FXS and aortic aneurysm. Our two cases highlight the risks of aortic pathology in FXS, and the need for monitoring in asymptomatic patients with significant aortic dilatation.

Topics: Aortic Aneurysm; Connective Tissue Diseases; Elastin; Fragile X Syndrome; Humans; Marfan Syndrome; Mitral Valve Prolapse

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the Fibrillin-1 gene. It is associated with formation of thoracic aortic aneurysms that can potentially be a life-threatening condition due to aortic rupture or dissection. Excessive non-canonical transforming growth factor beta signalling, mediated by activation of extracellular signal-regulated kinases 1/2 (ERK1/2), as well as inducible nitric oxide synthase (NOS2)-dependent nitric oxide production, have been identified to drive aortic pathology in MFS through induction of elastin fragmentation and smooth muscle cell apoptosis. Despite promising results in animal studies, specific pharmacological interventions approved for clinical use in patients with MFS-related aortic disease are rare. Nitro-oleic acid (NO2-OA) is an endogenously generated signalling modulator, which is available as an oral compound and has been shown to inhibit ERK1/2 activation and NOS2 expression in different disease models, thereby exerting promising therapeutic effects. In this study, we investigated whether NO2-OA decreases aortic dilation in MFS.. Eight-week-old MFS (Fbn1C1041G/+) mice were treated with NO2-OA or vehicle for 4 weeks via subcutaneously implanted osmotic minipumps. Echocardiography indicated progressive ascending aortic dilation and wall stiffening in MFS mice, which was significantly attenuated by NO2-OA treatment. This protective effect was mediated by inhibition of aortic ERK1/2, Smad2 as well as nuclear factor kappa B overactivation and consequent attenuation of elastin fragmentation by matrix metalloproteinase 2, apoptosis, and collagen deposition. Critically, the therapeutic efficacy of NO2-OA in MFS was further emphasized by demonstrating its capability to reduce lethal aortic complications in Fbn1C1041G/+ mice challenged with Angiotensin II.. NO2-OA distinctly attenuates progression of aortic dilation in MFS via modulation of well-established disease-mediating pathways, thereby meriting further investigation into its application as a therapeutic agent for the treatment of this condition.

Topics: Animals; Aortic Aneurysm; Aortic Aneurysm, Thoracic; Aortic Diseases; Disease Models, Animal; Elastin; Fibrillin-1; Marfan Syndrome; Matrix Metalloproteinase 2; Mice; Nitro Compounds; Oleic Acids

Marfan syndrome is one of the most common inherited disorders of connective tissue caused by fibrillin-1 mutations, characterized by enhanced transcription factor AP-1 DNA binding activity and subsequently abnormally increased expression and activity of matrix-metalloproteinases (MMPs). We aimed to establish a novel adeno-associated virus (AAV)-based strategy for long-term expression of an AP-1 neutralizing RNA hairpin (hp) decoy oligonucleotide (dON) in the aorta to prevent aortic elastolysis in a murine model of Marfan syndrome.. Using fibrillin-1 hypomorphic mice (mgR/mgR), aortic grafts from young (9 weeks old) donor mgR/mgR mice were transduced ex vivo with AAV vectors and implanted as infrarenal aortic interposition grafts in mgR/mgR mice. Grafts were explanted after 30 days. For in vitro studies, isolated primary aortic smooth muscle cells (SMCs) from mgR/mgR mice were used. Elastica-van-Giesson staining visualized elastolysis, reactive oxygen species (ROS) production was assessed using dihydroethidine staining. RNA F.I.S.H. verified AP-1 hp dON generation in the ex vivo transduced aortic tissue. MMP expression and activity were assessed by western blotting and immunoprecipitation combined with zymography.Transduction resulted in stable therapeutic dON expression in endothelial and SMCs. MMP expression and activity, ROS formation as well as expression of monocyte chemoattractant protein-1 were significantly reduced. Monocyte graft infiltration declined and the integrity of the elastin architecture was maintained. RNAseq analysis confirmed the beneficial effect of AP-1 neutralization on the pro-inflammatory environment in SMCs.. This novel approach protects from deterioration of aortic stability by sustained delivery of nucleic acids-based therapeutics and further elucidated how to interfere with the mechanism of elastolysis.

Topics: Animals; Aorta; Aortic Aneurysm; Cells, Cultured; Dependovirus; Dilatation, Pathologic; Disease Models, Animal; Elastin; Female; Fibrillin-1; Genetic Therapy; Genetic Vectors; Humans; Marfan Syndrome; Matrix Metalloproteinases; Mice, Transgenic; Oligonucleotides; Reactive Oxygen Species; Transcription Factor AP-1; Transduction, Genetic; Vascular Remodeling

Topics: Elastin; Extracellular Matrix; Fibrillin-1; Genetic Predisposition to Disease; Humans; Latent TGF-beta Binding Proteins; Marfan Syndrome; Models, Genetic; Mutation; Receptor, Transforming Growth Factor-beta Type II; Signal Transduction

Ascending aorta aneurysms (AsAA) are associated with a degeneration of the aortic wall tissue, which leads to changes in tissue mechanical properties. Risk factors for the development of the AsAA disease are recognized in patient age and gender, valve type, hypertension, diabetes mellitus, smoking history, and a prior diagnosis of Marfan syndrome. The present study aims to assess how such clinico-pathological factors can affect the mechanical properties of human dilated ascending aorta. Specimens of AsAA are excised from 68 patients who underwent elective AsAA surgical repair and stretched until rupture during the execution of uniaxial tensile tests. Experimental stress-stretch curves are used to determine tissue mechanical properties (stress and stretch at failure point and at transition point, low and high elastic modulus). Data are divided into groups according to region (anterior vs posterior), direction (circumferential vs longitudinal), and then according to age (young vs old), gender (male vs female), valve type (tricuspid aortic valve, TAV, vs bicuspid aortic valve, BAV), and presence of hypertension, diabetes mellitus, and/or Marfan syndrome (yes/no). Moreover, data are grouped according to the critical value of body mass index (BMI), maximum AsAA diameter, and aortic stiffness index (ASI), respectively. Finally, a non-parametric statistical analysis is performed to find possible significant differences and correlations between mechanical properties and clinico-pathological data. Our results confirm the anisotropy and heterogeneity of the AsAA tissue and highlight that ageing and hypertension make the AsAA tissue weaker and less extensible, whereas the valve type affects the tissue strength with higher values in BAV than in TAV patients. No effects of gender, critical BMI, critical maximum AsAA diameter, critical ASI, smoking status, and presence of diabetes mellitus, and Marfan syndrome are evidenced.

Topics: Aged; Anisotropy; Aorta; Aortic Aneurysm, Thoracic; Aortic Valve; Bicuspid Aortic Valve Disease; Biomechanical Phenomena; Body Mass Index; Body Weight; Collagen; Diabetes Mellitus; Elastin; Female; Heart Valve Diseases; Humans; Hypertension; Male; Marfan Syndrome; Middle Aged; Models, Statistical; Risk Factors; Stress, Mechanical; Tensile Strength; Vascular Stiffness

Regular low-impact physical activity is generally allowed in patients with Marfan syndrome, a connective tissue disorder caused by heterozygous mutations in the fibrillin-1 gene. However, being above average in height encourages young adults with this syndrome to engage in high-intensity contact sports, which unfortunately increases the risk for aortic aneurysm and rupture, the leading cause of death in Marfan syndrome. In this study, we investigated the effects of voluntary (cage-wheel) or forced (treadmill) aerobic exercise at different intensities on aortic function and structure in a mouse model of Marfan syndrome. Four-week-old Marfan and wild-type mice were subjected to voluntary and forced exercise regimens or sedentary lifestyle for 5 mo. Thoracic aortic tissue was isolated and subjected to structural and functional studies. Our data showed that exercise improved aortic wall structure and function in Marfan mice and that the beneficial effect was biphasic, with an optimum at low intensity exercise (55-65% V̇o

Topics: Animals; Aorta, Thoracic; Aortic Aneurysm, Thoracic; Dilatation, Pathologic; Disease Models, Animal; Elasticity; Elastin; Male; Marfan Syndrome; Matrix Metalloproteinase 2; Mice; Mice, Inbred C57BL; Mice, Transgenic; Physical Conditioning, Animal

Aortic root aneurysm formation and subsequent dissection and/or rupture remain the leading cause of death in patients with Marfan syndrome. Our laboratory has reported that miR-29b participates in aortic root/ascending aorta extracellular matrix remodeling during early aneurysm formation in

Topics: Animals; Aortic Aneurysm; Disease Models, Animal; Disease Progression; Echocardiography; Elastin; Extracellular Matrix; Female; Fetal Therapies; Genetic Therapy; Male; Marfan Syndrome; Matrix Metalloproteinases; Mice, Inbred C57BL; Mice, Mutant Strains; MicroRNAs; Molecular Targeted Therapy; Prenatal Care

Topics: Animals; Aorta; Aortic Aneurysm; Calcinosis; Elastin; Extracellular Signal-Regulated MAP Kinases; Humans; Marfan Syndrome; Mice; Mitogen-Activated Protein Kinase Kinases; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle

Marfan syndrome (MFS) is a multi-system connective tissue disorder that results from mutations to the gene that codes the elastin-associated glycoprotein fibrillin-1. Although elastic fibers are compromised throughout the arterial tree, the most severe phenotype manifests in the ascending aorta. By comparing biaxial mechanics of the ascending and descending thoracic aorta in a mouse model of MFS, we show that aneurysmal propensity correlates well with both a marked increase in circumferential material stiffness and an increase in intramural shear stress despite a near maintenance of circumferential stress. This finding is corroborated via a comparison of the present results with previously reported findings for both the carotid artery from the same mouse model of MFS and for the thoracic aorta from another model of elastin-associated glycoprotein deficiency that does not predispose to thoracic aortic aneurysms. We submit that the unique biaxial loading of the ascending thoracic aorta conspires with fibrillin-1 deficiency to render this aortic segment vulnerable to aneurysm and rupture.

Topics: Animals; Aorta, Thoracic; Aortic Aneurysm, Thoracic; Disease Models, Animal; Elastic Tissue; Elastin; Fibrillin-1; Humans; Male; Marfan Syndrome; Mechanical Phenomena; Mice; Stress, Mechanical; Weight-Bearing

Marfan syndrome is an autosomal dominant inherited disorder of connective tissue. The vascular complications of Marfan syndrome have the biggest impact on life expectancy. The aorta of Marfan patients reveals degradation of elastin layers caused by increased proteolytic activity of matrix metalloproteinases (MMPs). In this study we performed adenoviral gene transfer of human tissue inhibitor of matrix metalloproteinases-1 (hTIMP-1) in aortic grafts of fibrillin-1 deficient Marfan mice (mgR/mgR) in order to reduce elastolysis.. We performed heterotopic infrarenal transplantation of the thoracic aorta in female mice (n = 7 per group). Before implantation, mgR/mgR and wild-type aortas (WT, C57BL/6) were transduced ex vivo with an adenoviral vector coding for human TIMP-1 (Ad.hTIMP-1) or β-galactosidase (Ad.β-Gal). As control mgR/mgR and wild-type aortas received no gene therapy. Thirty days after surgery, overexpression of the transgene was assessed by immunohistochemistry (IHC) and collagen in situ zymography. Histologic staining was performed to investigate inflammation, the neointimal index (NI), and elastin breaks. Endothelial barrier function of native not virus-exposed aortas was evaluated by perfusion of fluorescent albumin and examinations of virus-exposed tissue were performed by transmission electron microscopy (TEM).. IHC and ISZ revealed sufficient expression of the transgene. Severe cellular inflammation and intima hyperplasia were seen only in adenovirus treated mgR/mgR aortas (Ad.β-Gal, Ad.hTIMP-1 NI: 0.23; 0.43), but not in native and Ad.hTIMP-1 treated WT (NI: 0.01; 0.00). Compared to native mgR/mgR and Ad.hTIMP-1 treated WT aorta, the NI is highly significant greater in Ad.hTIMP-1 transduced mgR/mgR aorta (p = 0.001; p = 0.001). As expected, untreated Marfan grafts showed significant more elastolysis compared to WT (p = 0.001). However, elastolysis in Marfan aortas was not reduced by adenoviral overexpression of hTIMP-1 (compared to untreated Marfan aorta: Ad.hTIMP-1 p = 0.902; control Ad.β-Gal. p = 0.165). The virus-untreated and not transplanted mgR/mgR aorta revealed a significant increase of albumin diffusion through the endothelial barrier (p = 0.037). TEM analysis of adenovirus-exposed mgR/mgR aortas displayed disruption of the basement membrane and basolateral space.. Murine Marfan aortic grafts developed severe inflammation after adenoviral contact. We demonstrated that fibrillin-1 deficiency is associated with relevant dysfunction of the endothelial barrier that enables adenovirus to induce vessel-harming inflammation. Endothelial dysfunction may play a pivotal role in the development of the vascular phenotype of Marfan syndrome.

Topics: Adenoviridae; Animals; Aorta; beta-Galactosidase; Cells, Cultured; Elastin; Endothelium, Vascular; Female; Fibrillin-1; Fibrillins; Genetic Therapy; Inflammation; Marfan Syndrome; Mice; Mice, Inbred C57BL; Microfilament Proteins; Neointima; Tight Junctions; Tissue Inhibitor of Metalloproteinase-1

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the fibrillin-1 gene. Patients with MFS are at risk of aortic aneurysm formation and dissection. Usually, blood pressure-lowering drugs are used to reduce aortic events; however, this is not sufficient for most patients. In the aorta of smooth muscle cell-specific sirtuin-1-deficient mice, spontaneous aneurysm formation and senescence are observed. Resveratrol is known to enhance sirtuin-1 activity and to reduce senescence, which prompted us to investigate the effectiveness of resveratrol in inhibition of aortic dilatation in the Fbn1(C1039G/+) MFS mouse model.. Aortic senescence strongly correlates with aortic root dilatation rate in MFS mice. However, although resveratrol inhibits aortic dilatation, it only shows a trend toward reduced aortic senescence. Resveratrol enhances nuclear localization of sirtuin-1 in the vessel wall and, in contrast to losartan, does not affect leukocyte infiltration nor activation of SMAD2 and extracellular signal-regulated kinases 1/2 (ERK1/2). Interestingly, specific sirtuin-1 activation (SRT1720) or inhibition (sirtinol) in MFS mice does not affect aortic root dilatation rate, although senescence is changed. Resveratrol reduces aortic elastin breaks and decreases micro-RNA-29b expression coinciding with enhanced antiapoptotic Bcl-2 expression and decreased number of terminal apoptotic cells. In cultured smooth muscle cells, the resveratrol effect on micro-RNA-29b downregulation is endothelial cell and nuclear factor κB-dependent.. Resveratrol inhibits aortic root dilatation in MFS mice by promoting elastin integrity and smooth muscle cell survival, involving downregulation of the aneurysm-related micro-RNA-29b in the aorta. On the basis of these data, resveratrol holds promise as a novel intervention strategy for patients with MFS.

Topics: Active Transport, Cell Nucleus; Animals; Aorta; Aortic Aneurysm; Apoptosis; Cells, Cultured; Cellular Senescence; Dilatation, Pathologic; Disease Models, Animal; Elastin; Female; Fibrillin-1; Genetic Predisposition to Disease; Human Umbilical Vein Endothelial Cells; Humans; Male; Marfan Syndrome; Mice, Inbred C57BL; Mice, Mutant Strains; MicroRNAs; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phenotype; Proto-Oncogene Proteins c-bcl-2; Resveratrol; Sirtuin 1; Stilbenes

Rupture and dissection of aortic root aneurysms remain the leading causes of death in patients with the Marfan syndrome, a hereditary connective tissue disorder that affects 1 in 5000 individuals worldwide. In the present study, we use a Marfan mouse model (Fbn1(C1039G/+)) to investigate the biological importance of apoptosis during aneurysm development in Marfan syndrome.. Using in vivo single-photon emission computed tomographic-imaging and ex vivo autoradiography for Tc99m-annexin, we discovered increased apoptosis in the Fbn1(C1039G/+) ascending aorta during early aneurysm development peaking at 4 weeks. Immunofluorescence colocalization studies identified smooth muscle cells (SMCs) as the apoptotic cell population. As biological proof of concept that early aortic wall apoptosis plays a role in aneurysm development in Marfan syndrome, Fbn1(C1039G/+) mice were treated daily from 2 to 6 weeks with either (1) a pan-caspase inhibitor, Q-VD-OPh (20 mg/kg), or (2) vehicle control intraperitoneally. Q-VD-OPh treatment led to a significant reduction in aneurysm size and decreased extracellular matrix degradation in the aortic wall compared with control mice. In vitro studies using Fbn1(C1039G/+) ascending SMCs showed that apoptotic SMCs have increased elastolytic potential compared with viable cells, mostly because of caspase activity. Moreover, in vitro (1) cell membrane isolation, (2) immunofluorescence staining, and (3) scanning electron microscopy studies illustrate that caspases are expressed on the exterior cell surface of apoptotic SMCs.. Caspase inhibition attenuates aneurysm development in an Fbn1(C1039G/+) Marfan mouse model. Mechanistically, during apoptosis, caspases are expressed on the cell surface of SMCs and likely contribute to elastin degradation and aneurysm development in Marfan syndrome.

Topics: Animals; Aorta; Aortic Aneurysm; Apoptosis; Autoradiography; Caspase Inhibitors; Caspases; Cell Membrane; Cells, Cultured; Disease Models, Animal; Disease Progression; Elastin; Female; Fibrillin-1; Fibrillins; Fluorescent Antibody Technique; Male; Marfan Syndrome; Mice, Inbred C57BL; Mice, Mutant Strains; Microfilament Proteins; Microscopy, Electron, Scanning; Muscle, Smooth, Vascular; Mutation; Myocytes, Smooth Muscle; Time Factors; Tomography, Emission-Computed, Single-Photon; Vascular Remodeling

Development of thoracic aortic aneurysms is the most significant clinical phenotype in patients with Marfan syndrome. An inflammatory response has been described in advanced stages of the disease. Because the hallmark of vascular inflammation is local interleukin-6 (IL-6) secretion, we explored the role of this proinflammatory cytokine in the formation of aortic aneurysms and rupture in hypomorphic fibrillin-deficient mice (mgR/mgR).. MgR/mgR mice developed ascending aortic aneurysms with significant dilation of the ascending aorta by 12 weeks (2.7 ± 0.1 and 1.3 ± 0.1 for mgR/mgR versus wild-type mice, respectively; P<0.001). IL-6 signaling was increased in mgR/mgR aortas measured by increases in IL-6 and SOCS3 mRNA transcripts (P<0.05) and in cytokine secretion of IL-6, MCP-1, and GM-CSF (P<0.05). To investigate the role of IL-6 signaling, we generated mgR homozygous mice with IL-6 deficiency (DKO). The extracellular matrix of mgR/mgR mice showed significant disruption of elastin and the presence of dysregulated collagen deposition in the medial-adventitial border by second harmonic generation multiphoton autofluorescence microscopy. DKO mice exhibited less elastin and collagen degeneration than mgR/mgR mice, which was associated with decreased activity of matrix metalloproteinase-9 and had significantly reduced aortic dilation (1.0 ± 0.1 versus 1.6 ± 0.2 mm change from baseline, DKO versus mgR/mgR, P<0.05) that did not affect rupture and survival.. Activation of IL-6-STAT3 signaling contributes to aneurysmal dilation in mgR/mgR mice through increased MMP-9 activity, aggravating extracellular matrix degradation.

Topics: Animals; Aorta; Aortic Aneurysm, Thoracic; Aortic Rupture; Chemokine CCL2; Collagen; Dilatation, Pathologic; Disease Models, Animal; Elastin; Extracellular Matrix; Fibrillin-1; Fibrillins; Granulocyte-Macrophage Colony-Stimulating Factor; Interleukin-6; Marfan Syndrome; Matrix Metalloproteinase 9; Mice; Mice, Inbred C57BL; Mice, Knockout; Microfilament Proteins; RNA, Messenger; Severity of Illness Index; Signal Transduction; STAT3 Transcription Factor; Suppressor of Cytokine Signaling 3 Protein; Suppressor of Cytokine Signaling Proteins; Time Factors; Up-Regulation

Ascending aortic dissection and rupture remain a life-threatening complication in patients with Marfan syndrome. The extracellular matrix provides strength and elastic recoil to the aortic wall, thereby preventing radial expansion. We have previously shown that ascending aortic aneurysm formation in Marfan mice (Fbn1(C1039G/+)) is associated with decreased aortic wall elastogenesis and increased elastin breakdown. In this study, we test the feasibility of quantifying aortic wall elastin content using MRI with a gadolinium-based elastin-specific magnetic resonance contrast agent in Fbn1(C1039G/+) mice.. Ascending aorta elastin content was measured in 32-week-old Fbn1(C1039G/+) mice and wild-type (n=9 and n=10, respectively) using 7-T MRI with a T1 mapping sequence. Significantly lower enhancement (ie, lower R1 values, where R1=1/T1) was detected post-elastin-specific magnetic resonance contrast agent in Fbn1(C1039G/+) compared with wild-type ascending aortas (1.15±0.07 versus 1.36±0.05; P<0.05). Post-elastin-specific magnetic resonance contrast agent R1 values correlated with ascending aortic wall gadolinium content directly measured by inductively coupled mass spectroscopy (P=0.006).. Herein, we demonstrate that MRI with elastin-specific magnetic resonance contrast agent accurately measures elastin bound gadolinium within the aortic wall and detects a decrease in aortic wall elastin in Marfan mice compared with wild-type controls. This approach has translational potential for noninvasively assessing aneurysm tissue changes and risk, as well as monitoring elastin content in response to therapeutic interventions.

Topics: Animals; Aorta, Thoracic; Aortic Aneurysm, Thoracic; Aortic Dissection; Chelating Agents; Contrast Media; Disease Models, Animal; Elastin; Feasibility Studies; Heterocyclic Compounds, 1-Ring; Magnetic Resonance Imaging; Male; Marfan Syndrome; Mice; Mice, Inbred C57BL; Reproducibility of Results

In a mouse model of Marfan syndrome, conventional Verhoeff-Van Gieson staining displays severe fragmentation, disorganization and loss of the aortic elastic fiber integrity. However, this method involves chemical fixatives and staining, which may alter the native morphology of elastin and collagen. Thus far, quantitative analysis of fiber damage in aorta and skin in Marfan syndrome has not yet been explored. In this study, we have used an advanced noninvasive and label-free imaging technique, multiphoton microscopy to quantify fiber fragmentation, disorganization, and total volumetric density of aortic and cutaneous elastin and collagen in a mouse model of Marfan syndrome. Aorta and skin samples were harvested from Marfan and control mice aged 3-, 6- and 9-month. Elastin and collagen were identified based on two-photon excitation fluorescence and second-harmonic-generation signals, respectively, without exogenous label. Measurement of fiber length indicated significant fragmentation in Marfan vs. control. Fast Fourier transform algorithm analysis demonstrated markedly lower fiber organization in Marfan mice. Significantly reduced volumetric density of elastin and collagen and thinner skin dermis were observed in Marfan mice. Cutaneous content of elastic fibers and thickness of dermis in 3-month Marfan resembled those in the oldest control mice. Our findings of early signs of fiber degradation and thinning of skin dermis support the potential development of a novel non-invasive approach for early diagnosis of Marfan syndrome.

Topics: Age Factors; Animals; Aorta; Collagen; Elastin; Humans; Marfan Syndrome; Mice, Inbred C57BL; Mice, Transgenic; Microscopy, Fluorescence, Multiphoton; Models, Molecular; Skin

Marfan syndrome (MFS) is an inherited disorder of connective tissue caused by mutations in the gene for fibrillin-1 (FBN1). The complex pathogenesis of MFS involves changes in transforming growth factor beta (TGF-β) signaling and increased matrix metalloproteinase (MMP) expression. Fibrillin-1 and elastin have repeated Gly-x-x- Pro-Gly (GxxPG) motifs that can induce a number of effects including macrophage chemotaxis and increased MMP activity by induction of signaling through the elastin-binding protein (EBP). In this work, we test the hypothesis that antagonism of GxxPG fragments can suppress disease progression in the Marfan aorta. Fibrillin-1 underexpressing mgR/mgR Marfan mice were treated with weekly intraperitoneal (i.p.) injections of an antibody directed against GxxPG fragments. The treatment was started at 3 weeks of age and continued for 8 weeks. The treatment significantly reduced MMP-2, MMP-9 and pSmad2 activity, as well as fragmentation and macrophage infiltration in the aorta of the mgR/mgR mice. Additionally, airspace enlargement and increased pSmad2 activity in the lungs of mgR/mgR animals were prevented by the treatment. Our findings demonstrate the important role of secondary cellular events caused by GxxPG-containing fragments and matrix-induced inflammatory activity in the pathogenesis of thoracic aortic aneurysm (TAA) in mgR/mgR mice. Moreover, the results of the current study suggest that antagonism of the effects of GxxPG fragments may be a fruitful therapeutic strategy in MFS.

Topics: Amino Acid Motifs; Animals; Antibodies, Monoclonal; Aortic Aneurysm, Thoracic; Aortic Diseases; Blotting, Western; Disease Models, Animal; Elastin; Enzyme-Linked Immunosorbent Assay; Fibrillin-1; Fibrillins; Immunohistochemistry; Latent TGF-beta Binding Proteins; Macrophages; Marfan Syndrome; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Mice; Microfilament Proteins; Mutation; Peptides; Signal Transduction; Smad2 Protein; Transforming Growth Factor beta; Up-Regulation

Marfan syndrome (MFS) is a systemic connective tissue disorder notable for the development of aortic root aneurysms and the subsequent life-threatening complications of aortic dissection and rupture. Underlying fibrillin-1 gene mutations cause increased transforming growth factor-β (TGF-β) signaling. Although TGF-β blockade prevents aneurysms in MFS mouse models, the mechanisms through which excessive TGF-β causes aneurysms remain ill-defined.. We investigated the role of microRNA-29b (miR-29b) in aneurysm formation in MFS.. Using quantitative polymerase chain reaction, we discovered that miR-29b, a microRNA regulating apoptosis and extracellular matrix synthesis/deposition genes, is increased in the ascending aorta of Marfan (Fbn1(C1039G/+)) mice. Increased apoptosis, assessed by increased cleaved caspase-3 and caspase-9, enhanced caspase-3 activity, and decreased levels of the antiapoptotic proteins, Mcl-1 and Bcl-2, were found in the Fbn1(C1039G/+) aorta. Histological evidence of decreased and fragmented elastin was observed exclusively in the Fbn1(C1039G/+) ascending aorta in association with repressed elastin mRNA and increased matrix metalloproteinase-2 expression and activity, both targets of miR-29b. Evidence of decreased activation of nuclear factor κB, a repressor of miR-29b, and a factor suppressed by TGF-β, was also observed in Fbn1(C1039G/+) aorta. Furthermore, administration of a nuclear factor κB inhibitor increased miR-29b levels, whereas TGF-β blockade or losartan effectively decreased miR-29b levels in Fbn1(C1039G/+) mice. Finally, miR-29b blockade by locked nucleic acid antisense oligonucleotides prevented early aneurysm development, aortic wall apoptosis, and extracellular matrix deficiencies.. We identify increased miR-29b expression as key to the pathogenesis of early aneurysm development in MFS by regulating aortic wall apoptosis and extracellular matrix abnormalities.

Topics: Age Factors; Angiotensin II Type 1 Receptor Blockers; Animals; Aorta; Aortic Aneurysm; Apoptosis; Apoptosis Regulatory Proteins; Cells, Cultured; Disease Models, Animal; Elastin; Female; Fibrillin-1; Fibrillins; Genetic Therapy; Losartan; Male; Marfan Syndrome; Matrix Metalloproteinase 2; Mice; Mice, Inbred C57BL; Mice, Transgenic; Microfilament Proteins; MicroRNAs; NF-kappa B; Oligonucleotides, Antisense; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Transforming Growth Factor beta; Up-Regulation

Mitral valve degeneration is a key component of the pathophysiology of Marfan syndrome. The biomechanical consequences of aging and genetic mutation in mitral valves are poorly understood because of limited tools to study this in mouse models. Our aim was to determine the global biomechanical and local cell-matrix deformation relationships in the aging and Marfan related Fbn1 mutated murine mitral valve. To conduct this investigation, a novel stretching apparatus and gripping method was implemented to directly quantify both global tissue biomechanics and local cellular deformation and matrix fiber realignment in murine mitral valves. Excised mitral valve leaflets from wild-type and Fbn1 mutant mice from 2 weeks to 10 months in age were tested in circumferential orientation under continuous laser optical imaging. Mouse mitral valves stiffen with age, correlating with increases in collagen fraction and matrix fiber alignment. Fbn1 mutation resulted in significantly more compliant valves (modulus 1.34 ± 0.12 vs. 2.51 ± 0.31 MPa, respectively, P<.01) at 4 months, corresponding with an increase in proportion of GAGs and decrease in elastin fraction. Local cellular deformation and fiber alignment change linearly with global tissue stretch, and these slopes become more extreme with aging. In comparison, Fbn1 mutated valves have decoupled cellular deformation and fiber alignment with tissue stretch. Taken together, quantitative understanding of multi-scale murine planar tissue biomechanics is essential for establishing consequences of aging and genetic mutations. Decoupling of local cell-matrix deformation kinematics with global tissue stretch may be an important mechanism of normal and pathological biomechanical remodeling in valves.

Topics: Aging; Animals; Biomechanical Phenomena; Elastin; Extracellular Matrix; Fibrillin-1; Fibrillins; Marfan Syndrome; Mice; Mice, Inbred C57BL; Microfilament Proteins; Microscopy, Confocal; Mitral Valve; Mitral Valve Insufficiency; Mutation; Tensile Strength

Marfan syndrome is an autosomal dominantly inherited disorder of connective tissue with prominent skeletal, ocular, and cardiovascular manifestations. Aortic aneurysm and dissection are the major determinants of premature death in untreated patients. In previous work, we showed that extracts of aortic tissues from the mgR mouse model of Marfan syndrome showed increased chemotactic stimulatory activity related to the elastin-binding protein. Aortic samples were collected from 6 patients with Marfan syndrome and 8 with isolated aneurysms of the ascending aorta. Control samples were obtained from 11 organ donors without known vascular or connective tissue diseases. Soluble proteins extracted from the aortic samples of the two patient groups were compared against buffer controls and against the aortic samples from controls with respect to the ability to induce macrophage chemotaxis as measured using a modified Boyden chamber, as well as the reactivity to a monoclonal antibody BA4 against bioactive elastin peptides using ELISA. Samples from Marfan patients displayed a statistically significant increase in chemotactic inductive activity compared to control samples. Additionally, reactivity to BA4 was significantly increased. Similar statistically significant increases were identified for the samples from patients with idiopathic thoracic aortic aneurysm. There was a significant correlation between the chemotactic index and BA4 reactivity, and the increases in chemotactic activity of extracts from Marfan patients could be inhibited by pretreatment with lactose, VGVAPG peptides, or BA4, which indicates the involvement of EBP in mediating the effects. Our results demonstrate that aortic extracts of patients with Marfan syndrome can elicit macrophage chemotaxis, similar to our previous study on aortic extracts of the mgR mouse model of Marfan syndrome (Guo et al., Circulation 2006; 114:1855-62).

Topics: Adult; Aged; Animals; Antibodies, Monoclonal; Aorta; Aortic Aneurysm, Thoracic; Cattle; Chemotaxis; Elastin; Enzyme-Linked Immunosorbent Assay; Female; Humans; Macrophages; Male; Marfan Syndrome; Mice; Middle Aged; Tissue Extracts; Young Adult

Elastin is the primary component of elastic fibres in arteries, which contribute significantly to the structural integrity of the wall. Fibrillin-1 is a microfibrillar glycoprotein that appears to stabilize elastic fibres mechanically and thereby to delay a fatigue-induced loss of function due to long-term repetitive loading. Whereas prior studies have addressed some aspects of ageing-related changes in the overall mechanical properties of arteries in mouse models of Marfan syndrome, we sought to assess for the first time the load-carrying capability of the elastic fibres early in maturity, prior to the development of ageing-related effects, dilatation, or dissection.. We used elastase to degrade elastin in common carotid arteries excised, at 7-9 weeks of age, from a mouse model (mgR/mgR) of Marfan syndrome that expresses fibrillin-1 at 15-25% of normal levels. In vitro biaxial mechanical tests performed before and after exposure to elastase suggested that the elastic fibres exhibited a nearly normal load-bearing capability. Observations from nonlinear optical microscopy suggested further that competent elastic fibres not only contribute to load-bearing, they also increase the undulation of collagen fibres, which endows the normal arterial wall with a more compliant response to pressurization.. These findings support the hypothesis that it is an accelerated fatigue-induced damage to or protease-related degradation of initially competent elastic fibres that render arteries in Marfan syndrome increasingly susceptible to dilatation, dissection, and rupture.

Topics: Age Factors; Animals; Biomechanical Phenomena; Carotid Artery, Common; Disease Models, Animal; Disease Progression; Elastic Tissue; Elastin; Fibrillin-1; Fibrillins; Male; Marfan Syndrome; Mice; Mice, Knockout; Microfilament Proteins; Pancreatic Elastase

The sequelae of aortic root dilation are the lethal consequences of Marfan syndrome. The root dilation is attributable to an imbalance between deposition of matrix elements and metalloproteinases in the aortic medial layer as a result of excessive transforming growth factor-beta signaling. This study examined the efficacy and mechanism of statins in attenuating aortic root dilation in Marfan syndrome and compared effects to the other main proposed preventative agent, losartan.. Marfan mice heterozygous for a mutant allele encoding a cysteine substitution in fibrillin-1 (C1039G) were treated daily from 6 weeks old with pravastatin 0.5 g/L or losartan 0.6 g/L. The end points of aortic root diameter (n=25), aortic thickness, and architecture (n=10), elastin volume (n=5), dp/dtmax (maximal rate of change of pressure) (cardiac catheter; n=20), and ultrastructural analysis with stereology (electron microscopy; n=5) were examined. The aortic root diameters of untreated Marfan mice were significantly increased in comparison to normal mice (0.161 ± 0.001 cm vs 0.252 ± 0.004 cm; P<0.01). Pravastatin (0.22 ± 0.003 cm; P<0.01) and losartan (0.221 ± 0.004 cm; P<0.01) produced a significant reduction in aortic root dilation. Both drugs also preserved elastin volume within the medial layer (pravastatin 0.23 ± 0.02 and losartan 0.29 ± 0.03 vs untreated Marfan 0.19 ± 0.02; P=0.01; normal mice 0.27 ± 0.02). Ultrastructural analysis showed a reduction of rough endoplasmic reticulum in smooth muscle cells with pravastatin (0.022 ± 0.004) and losartan (0.013 ± 0.001) compared to untreated Marfan mice (0.035 ± 0.004; P<0.01).. Statins are similar to losartan in attenuating aortic root dilation in a mouse model of Marfan syndrome. They appear to act through reducing the excessive protein manufacture by vascular smooth muscle cells, which occurs in the Marfan aorta. As a drug that is relatively well-tolerated for long-term use, it may be useful clinically.

Topics: Angiotensin II Type 1 Receptor Blockers; Animals; Aorta; Aortic Diseases; Dilatation, Pathologic; Disease Models, Animal; Elastin; Endoplasmic Reticulum; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Losartan; Male; Marfan Syndrome; Mice; Mice, Mutant Strains; Muscle, Smooth, Vascular; Pravastatin; Treatment Outcome; Tunica Media

The structural protein elastin endows large arteries with unique biological functionality and mechanical integrity, hence its disorganization, fragmentation, or degradation can have important consequences on the progression and treatment of vascular diseases. There is, therefore, a need in arterial mechanics to move from materially uniform, phenomenological, constitutive relations for the wall to those that account for separate contributions of the primary structural constituents: elastin, fibrillar collagens, smooth muscle, and amorphous matrix. In this paper, we employ a recently proposed constrained mixture model of the arterial wall and show that prestretched elastin contributes significantly to both the retraction of arteries that is observed upon transection and the opening angle that follows the introduction of a radial cut in an unloaded segment. We also show that the transmural distributions of elastin and collagen, compressive stiffness of collagen, and smooth muscle tone play complementary roles. Axial prestresses and residual stresses in arteries contribute to the homeostatic state of stress in vivo as well as adaptations to perturbed loads, disease, or injury. Understanding better the development of and changes in wall stress due to individual extracellular matrix constituents thus promises to provide considerable clinically important insight into arterial health and disease.

Topics: Aging; Algorithms; Aneurysm; Animals; Arteries; Biomechanical Phenomena; Collagen; Computer Simulation; Elastin; Humans; Hypertension; Marfan Syndrome; Models, Biological; Models, Theoretical; Stress, Mechanical

Even though elastin and fibrillin-1 are the major structural components of elastic fibers, mutations in elastin and fibrillin-1 lead to narrowing of large arteries in supravalvular aortic stenosis and dilation of the ascending aorta in Marfan syndrome, respectively. A genetic approach was therefore used here to distinguish the differential contributions of elastin and fibrillin-1 to arterial development and compliance.. Key parameters of cardiovascular function were compared among adult mice haploinsufficient for elastin (Eln(+/-)), fibrillin-1 (Fbn1(+/-)), or both proteins (dHet). Physiological and morphological comparisons correlate elastin haploinsufficiency with increased blood pressure and vessel length and tortuosity in dHet mice, and fibrillin-1 haploinsufficiency with increased aortic diameter in the same mutant animals. Mechanical tests confirm that elastin and fibrillin-1 impart elastic recoil and tensile strength to the aortic wall, respectively. Additional ex vivo analyses demonstrate additive and overlapping contributions of elastin and fibrillin-1 to the material properties of vascular tissues. Lastly, light and electron microscopy evidence implicates fibrillin-1 in the hypertension-promoted remodeling of the elastin-deficient aorta.. These results demonstrate that elastin and fibrillin-1 have both differential and complementary roles in arterial wall formation and function, and advance our knowledge of the structural determinants of vascular physiology and disease.

Topics: Animals; Aortic Stenosis, Supravalvular; Arteries; Biomechanical Phenomena; Compliance; Disease Models, Animal; Elastic Tissue; Elastin; Extracellular Matrix; Fibrillin-1; Fibrillins; Humans; Marfan Syndrome; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Microfilament Proteins; Phenotype

Ascending aortic aneurysms (AA) are a common, though poorly understood medical condition.. To document the histological changes in a large series of human ascending AA, and to correlate these changes with clinical variables.. 111 ascending AA were excised at surgery over a 3 year period. Each aneurysm was received as a continuous ring of tissue. Sections were taken from the anterior, posterior, greater and lesser curvature of the aorta and graded in a semi-quantitative fashion for the degree of elastin fragmentation, elastin loss, smooth muscle cell (SMC) loss, intimal changes and inflammation.. Mean patient age at surgery was 58.7 (15.6) years; there were 70 men and 41 women. 12 patients had Marfan syndrome, 34 (30.6%) had a bicuspid aortic valve (BAV), while 71 (64.0%) had a tricuspid aortic valve (TAV). Inflammatory cells were present in 28 cases (25.2%) and were confined to the adventitia. No particular region of the aortic circumference was more severely affected, however a BAV was associated with significantly less intimal change, and less fragmentation and loss of elastic tissue compared with patients with a TAV. Advanced age (>65 years), female gender and Marfan syndrome were all associated with more severe elastin degeneration and smooth muscle cell loss (p<0.05 for all).. Results indicate a wide variation in the histological appearance in ascending AA, depending on patient characteristics. They suggest that the underlying aneurysm pathogenesis may also be highly variable; this warrants further investigation.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Aortic Aneurysm; Aortic Valve; Elastic Tissue; Elastin; Female; Humans; Male; Marfan Syndrome; Middle Aged; Muscle, Smooth, Vascular; Sex Factors; Tunica Intima

The primary cause of early death in untreated Marfan syndrome (MFS) patients is aortic dilatation and dissection.. We investigated whether ascending aortic samples from the fibrillin-1-underexpressing mgR mouse model for MFS or a recombinant fibrillin-1 fragment containing an elastin-binding protein (EBP) recognition sequence can act as chemotactic stimuli for macrophages. Both the aortic extracts from the mgR/mgR mice and the fibrillin-1 fragment significantly increased macrophage chemotaxis compared with extracts from wild-type mice or buffer controls. The chemotactic response was significantly diminished by pretreatment of macrophages with lactose or with the elastin-derived peptide VGVAPG and by pretreatment of samples with a monoclonal antibody directed against an EBP recognition sequence. Mutation of the EBP recognition sequence in the fibrillin-1 fragment also abolished the chemotactic response. These results indicate the involvement of EBP in mediating the effects. Additionally, investigation of macrophages in aortic specimens of MFS patients demonstrated macrophage infiltration in the tunica media.. Our findings demonstrate that aortic extracts from mgR/mgR mice can stimulate macrophage chemotaxis by interaction with EBP and show that a fibrillin-1 fragment possesses chemotactic stimulatory activity similar to that of elastin degradation peptides. They provide a plausible molecular mechanism for the inflammatory infiltrates observed in the mgR mouse model and suggest that inflammation may represent a component of the complex pathogenesis of MFS.

Topics: Animals; Aorta; Cattle; Chemotactic Factors; Chemotaxis; Disease Models, Animal; Elastin; Fibrillin-1; Fibrillins; Macrophages; Marfan Syndrome; Mice; Mice, Mutant Strains; Microfilament Proteins; Peptide Fragments; Recombinant Fusion Proteins; Tissue Extracts

Patients with Marfan syndrome show a hereditary abnormality of elastin metabolism that may cause aortic enlargement and dissection. We have hypothesized that abnormal elastin may alter peripheral vascular structure and function.. Forearm blood flow (FBF) (in milliliters per minute per 100 mL) response to the endothelium-dependent dilator acetylcholine (0.75 to 4.5 microg/min per 100 mL), the endothelium-independent dilator sodium nitroprusside (0.05 to 0.3 microg/min per 100 mL), and structure-related maximum dilator response (10-minute occlusion-induced reactive hyperemia) were measured by plethysmograph in 10 patients with Marfan syndrome (mean age 44 years) and 10 healthy age- and sex-matched controls. Patients with the complications of hypercholesterolemia, diabetes mellitus, or heart failure were excluded from the study.. Basal FBF (mean +/- SE) did not differ between the 2 groups (2.7 +/- 0.3 vs 2.3 +/- 0.4). Maximum FBF response to acetylcholine in patients with Marfan syndrome was significantly lower than that of healthy controls (8.5 +/- 2.1 vs 15.4 +/- 1.7 mL/min per 100 mL; P <.05). Reactive hyperemia was also lower in patients with Marfan syndrome (at peak 23.0 +/- 2.5 vs 29.5 +/- 2.3 mL/min per 100 mL; P <.05), but sodium nitroprusside-induced FBF changes did not differ between the 2 groups (10.3 +/- 1.1 vs 10.2 +/- 1.5 mL/min per 100 mL; P = not significant).. These observations suggest that endothelium-dependent dilation and maximum dilator reserve capacity are both abnormal in peripheral resistance vessels of patients with Marfan syndrome. These peripheral vasomotion abnormalities may have a detrimental impact on the cardiovascular system in this disorder.

Topics: Adult; Blood Flow Velocity; Elastin; Female; Forearm; Humans; Hyperemia; Male; Marfan Syndrome; Middle Aged; Muscle, Smooth, Vascular; Nitroprusside; Plethysmography; Regional Blood Flow; Vascular Resistance; Vasodilator Agents

Aneurysmal dilation of the aorta with subsequent rupture or dissection occurs frequently in patients with Marfan syndrome and is the primary cause of morbidity. These complications are related to the altered composition and disorganized structure of the aortic media. Our goal was to use high-frequency ultrasonic tissue characterization to identify these structural changes in abnormal aorta from patients with Marfan syndrome. We measured integrated backscatter and anisotropy of backscatter of ultrasound from specimens of aorta from patients with Marfan syndrome undergoing aortic root replacement and compared these values with those from aortic specimens of patients without clinical aortic pathology.. Aortic tissue was obtained at the time of surgery from 11 patients with Marfan syndrome undergoing repair of an aortic aneurysm or dissection. Normal tissue was obtained at the time of autopsy from 8 patients without evidence of aortic disease. Acoustic microscopy at 50 MHz was performed to measure integrated backscatter from each specimen. The magnitude of ultrasonic anisotropy of backscatter for each tissue type was determined as an index of the three-dimensional (3D) organization of the vessel matrix. The collagen content of each specimen was determined with a hydroxyproline assay. Marfan aortas exhibited less backscatter than did normal aortas (-40.9 +/- 2.9 versus -32.6 +/- 2.2 dB for patients with Marfan syndrome and healthy subjects, respectively, P < .0001). No significant difference in collagen concentrations was observed between normal and Marfan aorta (262.7 +/- 52.7 versus 282.4 +/- 41.8 mg/g tissue for normal and Marfan aortas, respectively, P = .42), despite the large difference in backscatter. Histological analysis revealed striking differences in both the amount and organization of the elastin in the aortic aneurysm segments from patients with Marfan syndrome compared with normal aorta. Normal aorta was characterized by well-formed elastin fibers arranged in a lamellar pattern. The media from aneurysms in Marfan aorta exhibited a profound decrease in elastin content that was associated with loss of the highly aligned and ordered lamellar arrangement. The directional dependence of scattering, or ultrasonic anisotropy, also differed dramatically between the two tissue types. Backscatter from normal aorta decreased substantially when the media was insonified parallel compared with perpendicular to the principal axis of the elastin fibers. Marfan aorta exhibited a much smaller directional dependence of scattering. Normal aortas manifested a 14-fold greater ultrasonic anisotropy than did Marfan aortas (24.1 +/- 3.7 versus 12.4 +/- 3.3 dB for normal and Marfan aortas, P < .0001), which is indicative of the profound extent of matrix disorganization in Marfan syndrome.. These data show that high-frequency ultrasonic tissue characterization sensitively detects changes in vessel wall composition and organization that occur in the aorta of patients with Marfan syndrome. Aortic segments from these patients manifested a significant decrease in integrated backscatter compared with normal aorta (approximately 8 dB, or greater than a 6-fold decrease in scattering). A 15-fold reduction in the ultrasonic anisotropy of Marfan tissue was observed, which suggests a marked disorganization of the 3D architecture of these aortas. These data support the hypothesis that high-frequency ultrasonic tissue characterization may be useful for identifying abnormalities of vessel wall composition, architecture, and material properties.

Topics: Adult; Anisotropy; Aorta; Aortic Aneurysm; Aortic Dissection; Collagen; Elastin; Female; Humans; Male; Marfan Syndrome; Tunica Media; Ultrasonography

Topics: Aorta; Aortic Aneurysm; Aortic Dissection; Collagen; Elastin; Extracellular Matrix Proteins; Fibrillins; Humans; Marfan Syndrome; Microfilament Proteins; Ultrasonography

Topics: Adrenergic beta-Antagonists; Aortic Aneurysm; Aortic Dissection; Aortic Valve Insufficiency; Elastin; Fibrillins; Genetic Counseling; Humans; Marfan Syndrome; Microfilament Proteins; Mitral Valve Insufficiency; Myofibrils; Patient Care Team; Phenotype

Samples from the ascending aortae from two calves affected by bovine Marfan syndrome were subjected to biochemical analyses of the connective tissue and were compared to age-matched controls. Elastin was extracted from the aortic samples with 5 M guanidine-HCl, bacterial collagenase digestion, and dithiothreitol reduction. Amino acid analysis revealed that desmosine and isodesmosine levels were the same in Marfan calves as in control animals. Gravimetric measurements of elastin, amino acid composition, soluble protein, and uronic acid values also showed no significant difference between Marfan and control tissue. In contrast to elastin, collagen in aortae of Marfan calves was significantly higher than the mean of several controls. These findings, along with other observations of this animal model, support the conclusion that the microscopic and biochemical lesions of aortic elastin in bovine Marfan syndrome likely result from defective microfibrillar metabolism. Absence of cystic medial necrosis in bovine Marfan aortae may explain normal elastin content in the animal model.

Topics: Animals; Aorta; Cattle; Collagen; Elastin; Fibrillins; Marfan Syndrome; Microfilament Proteins

Marfan syndrome represents a heterogeneous connective tissue disease, the symptoms arising in several tissues and organs. The defective gene(s) behind this autosomal dominant condition has not been found despite considerable research. The main targets of the research have been the genes coding for connective tissue components. Several of the candidate genes suspected to be defective in Marfan syndrome are located on the long arm of chromosome 2. These genes include a cluster of two genes coding for fibrillar collagens COL3A1 and COL5A2, and a third member of the collagen gene family: COL6A3. Furthermore, genes for elastin (ELN) and fibronectin (FN) are also located in this area of chromosome 2. We studied this chromosomal area using restriction fragment length polymorphism (RFLP) linkage analysis in five Finnish Marfan families with affected members in three generations. In two point linkage analyses, Lod scores of -3.192 (theta = 0.1) to COL3A1, -1.683 (theta = 0) to COL6A3 and -2.664 (theta = 0.01) to FN were obtained, whereas the linkage analysis between elastin and the disease was non-informative (Lod score 0.444, theta = 0). With the multipoint linkage analysis that permits simultaneous examination of several loci and more efficient use of family data, we obtained an exclusion of all these loci as the site of the mutation leading to Marfan syndrome in these families.

Topics: Chromosomes, Human, Pair 2; Collagen; DNA; Elastin; Fibronectins; Genetic Linkage; Genetic Markers; Humans; Marfan Syndrome; Polymorphism, Restriction Fragment Length

The Marfan syndrome is a serious heritable connective-tissue disorder characterized primarily by ocular, cardiovascular, and musculoskeletal abnormalities but also involving multiple other tissues and organs of the body. Inherited as an autosomal dominant disorder, the etiology and pathogenesis of the Marfan syndrome are presently unknown. We have documented consistent apparent deficient content of elastin-associated microfibrillar fibers by indirect immunofluorescent (IF) studies of Marfan skin, as well as deficient accumulation of related fibrous materials in cultures of Marfan fibroblasts as compared with normal controls and patients with other heritable disorders of connective tissue. These data have suggested that abnormalities in the microfibrillar component of elastic-fiber systems may have a role in the etiology and pathogenesis of the Marfan syndrome. In the present study, we have analyzed the IF staining patterns of skin and fibroblast cultures from Marfan syndrome patients and normal first-degree relatives in nine Marfan kindreds. Three of these families had at least one affected individual in each of 2 generations, permitting intergenerational comparison of IF patterns. Six kindreds had one or more affected individuals in a single generation, making comparisons between siblings and/or parent-child possible. In all cases, IF abnormalities cosegregated with the Marfan phenotype and all nonaffected family members were normal. Within family groups containing more than one affected individual, the IF staining patterns were similar between affected patients. These data provide further confirmation of consistent and relatively specific deficiency of microfibrillar fibers in Marfan syndrome.

Topics: Adolescent; Adult; Aged; Cells, Cultured; Child; Child, Preschool; Elastin; Female; Fluorescent Antibody Technique; Humans; Male; Marfan Syndrome; Middle Aged; Pedigree; Phenotype; Skin

Elastin of the ascending aortic media of 10 cases with type A dissecting aneurysm, 14 hypertensive cases, and 30 control cases were prepared by the treatment of aortas with hot formic acid, and three-dimensional architecture was observed by scanning electron microscopy. In the control cases, elastin showed framework-like continuous structure consisting of elastic laminae, and interlaminar fibers that interconnected the laminae. In 6 of 10 cases of dissecting aneurysm, the interlaminar fibers were apparently irregular in arrangement and shape, and decreased in number, especially in the outer media. This architectural alteration resulted in a rarefaction of interconnection between the elastic laminae in the media, and possibly resulted in the local weakness against the dissecting force of the laminae. This medial weakness may be related to the mechanism of initiation and progression of dissecting aneurysm. The cystic medial necrosis (CMN) was found in 3 cases, but only 1 of them was accompanied by a mild decrease of the interlaminar fibers in the area outside of CMN, suggesting that the initiation of CMN did not directly relate to the decrease of the interlaminar fibers. The aortic media of hypertensives generally showed an increase of interlaminar fibers, but their focal decrease was encountered in the outer media of 3 cases. These findings suggest that the decrease of the interlaminar fibers of medial elastin seen in dissecting aneurysms were related to hypertension.

Topics: Adult; Aged; Aged, 80 and over; Aorta; Aortic Aneurysm; Aortic Dissection; Elastin; Female; Humans; Hypertension; Male; Marfan Syndrome; Microscopy, Electron, Scanning; Middle Aged

In diseases of major arteries there is an increased turnover of connective tissue components. This implies a greater excretion of fragments of collagen and elastin. The changes for each of these may be useful in further delineating the nature of the disease. In a preliminary study, the urine of 10 Marfan's syndrome patients was analyzed. The hydroxyproline (collagen) concentration was up to eight times higher than that of control subjects. The desmosine (elastin) crosslink concentration was either normal or slightly reduced in these patients. The mean of the ratio of hydroxyproline to desmosine was nearly seven times higher in the patients.

Topics: Arteries; Collagen; Desmosine; Elastin; Humans; Hydroxyproline; Marfan Syndrome; Solubility; Vascular Diseases

Electron microscopic examinations were performed on systemic muscle-type arteries from two teen-age girls with Marfan's syndrome. In the peripheral organ arteries, the internal elastic lamella revealed a feature tentatively termed "osmiophilic elastolysis". The lytic changes appeared segmentally in the form of electron-dense fragments, and were partly absorbed. Regenerated elastin had a normal structure and surrounded the elastolytic lesions. The same changes were observed in the newly formed small areas of elastin in the thickened intima. The remaining elastic lamella in the affected region contained numerous fine electron-dense granules. Intercellular substances, including collagen fibrils and proteoglycan, other than elastic fibers, were increased secondarily in the elastolytic lesions without any evidence of ultrastructural abnormality. Medical smooth muscle cells making contact with the elastolytic lesions were necrosed and absorbed, and smooth muscle cells in a state of synthesis were increased in the adjacent areas. Abnormal elastogenesis, which showed no remarkable changes macroscopically or light microscopically, was systemic but segmental in the peripheral organ arteries, and regeneration of the structurally normal elastin was concurrent with elastolysis. These events were diagnostic for Marfan's syndrome, and cannot be explained by the conventional theory of elastogenetic enzymic deficiency.

Topics: Adolescent; Arteries; Elastin; Female; Humans; Marfan Syndrome; Microscopy, Electron

Elastin and collagen concentrations were determined in intimal-medial samples of ascending aortas from healthy controls of different ages and from 20 patients with annuloaortic ectasia (AAE). Five patients had the Marfan syndrome. In controls the highest elastin concentrations (estimated from desmosine concentrations or insoluble residues after hot-alkali extraction) were found in children. During aging until 60 years, elastin concentration decreased when determined by the hot-alkali extraction method while desmosine concentration changed less. Aorta samples from the Marfan-syndrome patients showed a great variation of elastin concentration from total lack to normal values. Samples from the other AAE patients could be divided into two groups. One contained clearly less elastin and more collagen than the controls whereas in the other group this difference was less marked. Histological examination of the aortic wall of the first group also showed marked fibrosis accompanied by severe elastin fragmentation and acellularity. From the 15 non-Marfan patients 14 were men. By means of clinical examination these patients could also be divided into "familial" and "nonfamilial" groups, because increased diameter of the aortic root was found in relatives of almost half of the patients. However, there were no differences in elastin and collagen concentrations between the familial and nonfamilial cases. As well, no correlation was found between biochemical findings and diameters of the aortic roots. These results point to altered elastin and/or collagen metabolism in the aortic wall of AAE patients.

Topics: Adolescent; Adult; Aged; Amino Acids; Aorta; Aortic Diseases; Child; Collagen; Desmosine; Elastin; Female; Humans; Male; Marfan Syndrome; Middle Aged

An intrinsic defect in the aortic media in six patients with Marfan's syndrome, who died of cardiovascular complications of the disease at an average age of 32 years, has been delineated by correlated morphologic, biochemical, and mechanical studies. The findings in the Marfan aortas have been compared with those in age- and sex-matched controls, who died of unrelated diseases without significant aortic lesions, and in three patients with dissecting aneurysms of non-Marfan origin. The results showed that there was a significant reduction in the tensile strength of the aorta in Marfan's syndrome. This finding was correlated by scanning electron microscopy with structural alterations of the medial elastic fibers, including enlarged interlaminar spaces and loss of interlaminar elastic fibrils. No structural alterations were identified in collagen fibers. Biochemical analyses of the aortic media revealed a substantial reduction in aortic elastin content. Furthermore, the desmosine content of the isolated elastin was reduced by approximately 50%. No changes were detected in the composition or solubility of the medial collagen. In contrast to Marfan aortas, the elastin and collagen contents of the dissecting aneurysms of non-Marfan origin were similar to those of the controls. These findings suggest that the vascular complications in Marfan's syndrome may be based on a genetic abnormality affecting elastin fibrillogenesis.

Topics: Adult; Aorta; Aortic Aneurysm; Aortic Dissection; Collagen; Elastin; Glycosaminoglycans; Humans; Hydroxyproline; Marfan Syndrome; Microscopy, Electron, Scanning; Tensile Strength

Human aortic elastin reduced with [3H]borohydride was analysed by ion-exchange chromatography after alkali or acid hydrolysis. Alkali hydrolysates of elastins contained a radioactive peak that was eluted between proline and leucine. This peak was not present in foetal elastin, but its proportion increased steadily during aging. Aortic samples from patients with annulo-aortic ectasia (aneurysm of the ascending aorta), including one with classical Marfan syndrome, contained less elastin (CNBr-insoluble material) than did the age-matched controls. The proportion of radioactivity in the new peak of all these aortas was low when compared with age-matched controls. Gas-chromatographic/mass-spectrometric analysis suggested that it contained a cyclic derivative of a hydrated aldol-condensation product. The concentration of the cross-link precursors, lysine aldehyde and aldol-condensation product (estimated from the acid-hydrolysis product 6-chloronorleucine and the acid-degradation product of reduced aldol-condensation product) was high in very young aortas but remained quite stable after childhood. No differences were observed in cross-link profiles of acid hydrolysates between pathological and control aortas. A low proportion of radioactivity in the new peak may indicate the presence of young or immature elastin in the pathological aortas.

Topics: Adult; Age Factors; Amino Acids; Aorta; Aortic Diseases; Borohydrides; Child; Chromatography, Ion Exchange; Dilatation, Pathologic; Elastin; Female; Gas Chromatography-Mass Spectrometry; Humans; Hydrolysis; Male; Marfan Syndrome; Middle Aged

Previous morphologic observations have suggested abnormalities in the elastic fibers in a number of both inherited and acquired diseases. Recent progress made in understanding of the normal biology of elastin has allowed us to examine these diseases by biochemical means. In this review we are discussing the current status of the research on the elastin diseases with particular emphasis on clinical conditions affecting skin, as for example, cutis laxa, pseudoxanthoma elasticum, and the Buschke-Ollendorff syndrome. In addition, we present new data which appears to be the first demonstration of an elastin abnormality in the Marfan syndrome.

Topics: Connective Tissue Diseases; Cutis Laxa; Elastin; Humans; Marfan Syndrome; Menkes Kinky Hair Syndrome; Pseudoxanthoma Elasticum; Skin; Skin Diseases

Amino acid chromatography was used for determination of the elastin-specific amino acids desmosine and isodesmosine in acid hydrolyzates of intima-medial samples taken intraoperatively from aneurysms of human ascending aorta. Elastin concentration of the specimens was also estimated by hot alkali extraction followed by nitrogen determination of the extracted material and the insoluble residue. All patients studied had annulo-aortic ectasia i.e., dilatation of the aortic annulus and the ascending aorta. Two patients with the Marfan syndrome had low aortic elastin concentration determined by both methods. A third Marfan syndrome patient, youngest of the three, also had a slightly reduced concentration of elastin in the aorta. Aortic samples were studied from five patients who did not have the classical Marfan syndrome. Two patients of those five had decreased aortic elastin concentration. The change in elastin concentration was accompanied by high hydroxyproline/proline or hydroxylysine/lysine ratios which indicates that the proteins of the aneurysmatic aortic wall contained more collagen than the proteins of the control aortic wall. These findings point to a change in the structure or metabolism of elastin in the aortic wall in the Marfan syndrome and at least in some other patients with annulo-aortic ectasia.

Topics: Adolescent; Adult; Amino Acids; Aorta, Thoracic; Aortic Aneurysm; Child; Desmosine; Elastin; Female; Humans; Male; Marfan Syndrome; Middle Aged

Aortae from three patients with classic presentation of Marfan syndrome, who died of vascular complications, were subjected to biochemical analyses of the connective tissue; for comparison, aortae from eight age-matched controls, without evidence of connective tissue abnormalities, were examined. Elastin was prepared from the aortae by two techniques. First, the tissues were extracted with 5 M guanidine-HCl, bacterial collagenase digestion and reduction with dithiothreitol (elastin I preparation). Secondly, this material was further purified by extraction with 0.1 M NaOH at 99 degrees C (elastin II preparation). Amino acid analyses of both elastin preparations indicated that the values for desmosine and isodesmosine were reduced in Marfan cases to approximately one-half of the control values. A corresponding increase in lysyl residues was noted in elastin II preparations. Also, the concentration of elastin per milligram dry weight of tissue was reduced in Marfan cases. The hydroxyproline content of elastin was increased in two cases with the Marfan syndrome. Recoveries indicated that the alkali treatment solubilized 46.2% of the elastin I preparations in Marfan aortae compared with 23.7% in controls. In contrast to elastin, the concentration and solubility of collagen were unchanged; the amino acid composition and the genetic types of insoluble collagen isolated by limited pepsin proteolysis were the same in both Marfan and control aortae. The results of our study demonstrate that the cross-linking of aortic elastin is reduced in the three patients with Marfan syndrome. Thus, a defect in elastin could explain the vascular fragility observed clinically in these patients.

Topics: Adult; Amino Acids; Aorta; Collagen; Elastin; Humans; Male; Marfan Syndrome

Insoluble elastins were isolated from control and aneurytic aortas by a sequential extraction procedure involving the use of purified collagenase. Marked differences in amino acid analyses and susceptibilities to pancreatic elastase were observed between normal and pathological samples. The incorporation of either 14C-lysine or 14C-glucosamine into proteins of the vessel wall was also studied. In addition, high amounts of elastase-type activity was extractable from pathological aorta specimens which may contribute significantly to the loss of elastic tissue evidenced by ultra-structural studies and confirmed by the biochemical technics. We propose therefore that increased elastase-type protease activity in these pathological aortas does significantly contribute to the weakening of the aortic wall and also may well be the main cause of the rupture of aneurysms observed occasionally.

Topics: Adult; Aged; Aorta; Aortic Aneurysm; Aortic Dissection; Elastic Tissue; Elastin; Female; Humans; Hydrolysis; Male; Marfan Syndrome; Middle Aged; Muscle, Smooth, Vascular; Organ Culture Techniques; Pancreatic Elastase

Topics: Collagen; Collagen Diseases; Connective Tissue; Culture Techniques; Elastic Tissue; Elastin; Fibroblasts; Humans; Marfan Syndrome; Microscopy, Electron; Penicillamine; Scleroderma, Systemic; Skin Manifestations; Vitamin K

Topics: Amino Acid Oxidoreductases; Aminopropionitrile; Animals; Carbon Isotopes; Cartilage; Cells, Cultured; Chickens; Collagen; Culture Media; Ehlers-Danlos Syndrome; Elastin; Fibroblasts; Humans; Lysine; Marfan Syndrome; Procollagen-Proline Dioxygenase; Proline; Skin; Tritium

Topics: Adolescent; Angiocardiography; Blood Flow Velocity; Blood Pressure; Cardiac Catheterization; Child; Cineangiography; Dilatation; Elastin; Female; Heart Auscultation; Heart Septal Defects, Atrial; Humans; Male; Marfan Syndrome; Pulmonary Artery; Pulmonary Circulation; Pulmonary Valve Stenosis; Vascular Resistance