osteoprotegerin and Fractures--Bone

In the beginning, that is from the 1960's, when a link between menopause and osteoporosis was first identified; estrogen treatment was the standard for preventing bone loss, however there was no fracture data, even though it was thought to be effective. This continued until the Women's Health Initiative (WHI) study in 2001 that published data on 6 years of treatment with hormone therapy that showed an increase in heart attacks and breast cancer. Even though the risks were small, 1 per 1500 users annually, patients were worried and there was a large drop off in estrogen use. In later analyses the WHI study showed that estrogen reduced fractures and actually prevented heart attacks in the 50-60 year age group. Estrogen alone appeared to be safer to use than estrogen+the progestin medroxyprogesterone acetate and actually reduced breast cancer. At the same time other drugs were being developed for bone that belong to the bisphosphonate group and the first generation of compounds showed moderate potency on bone resorption. The second and third generation compounds were much more potent and in a series of large trials were shown to reduce fractures. For the last 15 years the treatment of osteoporosis belonged to the bisphosphonate compounds, most of which reduce fracture rates by 50 percent. With the exception of gastrointestinal irritation the drugs are well tolerated and highly effective. The sophistication of the delivery systems now allow treatment that can be given daily, weekly, monthly and annually either orally or intravenously. Bone remodeling is a dynamic process that repairs microfractures and replaces old bone with new bone. In the last 10 years there has been a remarkable understanding of bone biology so that new therapies can be specifically designed on a biological basis. The realization that RANKL was the final cytokine involved in the resorption process and that marrow cells produced a natural antagonist called Osteoprotegerin (OPG) quickly led to two lines of therapy. First OPG was used as a therapy to block RANKL was initially successful but later antibodies against OPG developed and this line of treatment had to be discontinued. The next step was to develop a monoclonal antibody against RANKL and this proved to be highly effective in blocking bone resorption. It led to development of a drug Denosumab that successfully reduces fractures and is now one of the therapeutic options for osteoporosis treatment. On the anabolic side bone biology res

Topics: Aged; Aged, 80 and over; Alendronate; Antibodies, Monoclonal, Humanized; Bone Density; Bone Remodeling; Calcitonin; Denosumab; Diphosphonates; Estrogen Replacement Therapy; Female; Fractures, Bone; Humans; Middle Aged; Osteoporosis, Postmenopausal; Osteoprotegerin; RANK Ligand; Risk Factors; Selective Estrogen Receptor Modulators; Teriparatide

An imbalance of the remodeling process for bone resorption leads to a loss of tissue with consequent microarchitectural damage, evident in conditions such as osteoporosis and related fragility fractures. Currently, pharmacological therapies are able to prevent or slow down bone resorption by inhibiting osteoclast activity. An innovative and targeted anti-resorptive approach is represented by the inhibition of RANK ligand (RANK-L), essential for the proliferation and activity of osteoclastic cells. The human monoclonal antibody against RANK-L (denosumab) has been approved for the treatment of osteoporosis. In clinical trials of patients with osteoporosis, inhibition of RANK-L has reduced bone loss and damage to the microarchitecture and was associated with an increase in mass and resistance at different skeletal sites, with most significant effects than those demonstrated by any other antiresorptive drugs. In addition, after 3 years of treatment, it showed a reduction in vertebral and non-vertebral fracture risk. Denosumab treatment also has not revealed any alteration in the physiological processes of fracture repair, showing no increase in the onset of complications 3 years after the fracture. The data show that denosumab offers an effective alternative therapeutic approach for the treatment of severe osteoporosis, with positive effects on BMD and reduction of fragility fractures risk. So, promising results in terms of therapeutic efficacy and reliability make desirable the wide clinical use of denosumab for the treatment of osteoporotic fractures in the near future.

Topics: Animals; Antibodies, Monoclonal, Humanized; Bone and Bones; Bone Density; Bone Density Conservation Agents; Bone Resorption; Cell Proliferation; Denosumab; Female; Fracture Healing; Fractures, Bone; Humans; Male; Mice; Osteoclasts; Osteoporosis; Osteoporosis, Postmenopausal; Osteoprotegerin; Postmenopause; Randomized Controlled Trials as Topic; RANK Ligand; Treatment Outcome

Osteoporosis is the most common systemic skeletal disease characterized by low bone mass, increased bone turnover, and subsequent increased susceptibility to fracture. The aim of this paper was to present a molecular basis of bone remodeling, pathogenesis and different types of osteoporosis. Diagnostic studies, including bone densitometry and laboratory analysis were also reviewed.

Topics: Alkaline Phosphatase; Biomarkers; Bone and Bones; Bone Density; Bone Remodeling; Calcium; Collagen Type I; Female; Fractures, Bone; Humans; Hydroxyproline; Male; Osteoporosis; Osteoprotegerin; Parathyroid Hormone; Risk Factors; Vitamin D

The pathway of the receptor activator of the nuclear factor kappaB ligand (RANKL), RANK and osteoprotegerin (OPG) plays a central role in coupling bone formation and resorption during normal bone turnover and in a wide spectrum of diseases characterized by disturbed bone remodeling, increased bone resorption and bone destruction (osteoporosis, Paget's disease of bone, rheumatoid arthritis [RA], metastatic bone disease). Clinical trials indicate that denosumab, a RANKL-specific recombinant humanized monoclonal antibody, is effective in suppressing bone resorption, resulting in increase in bone mineral density (BMD) in post-menopausal women with low BMD, and has the potential to prevent progression of erosions in RA and of skeletal-related events in metastatic bone disease. The effects on fracture reduction in postmenopausal osteoporosis are awaited from the recently finished FREEDOM study. In clinical trials with denosumab, overall adverse events were similar to placebo or comparators, indicating a favorable safety profile in these diseases, which until now have been available up to 4 years, but data on long-term safety will be needed.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Arthritis, Rheumatoid; Bone Density; Bone Remodeling; Bone Resorption; Denosumab; Female; Fractures, Bone; Humans; Middle Aged; Osteoporosis, Postmenopausal; Osteoprotegerin; RANK Ligand

Parathyroid hormone (PTH) has been applied to postmenopausal women and several studies revealed that intermittent PTH treatment significantly increases lumbar bone mineral density and reduces fracture risk. However, the mechanism of PTH anabolic function on bone is not fully understood yet. PTH receptors (PPR) are expressed in osteoblasts and PPR stimulates multiple intracellular signal pathways, including those mediated by cAMP-PKA signaling pathway and PLC-PKC signaling pathway. Several studies demonstrate that the PKA signaling through G-proteins in osteoblasts play important roles in regulating gene expression and osteogenesis by PTH.

Topics: Animals; Bone Density; Bone Resorption; Cyclic AMP-Dependent Protein Kinases; Female; Fractures, Bone; GTP-Binding Proteins; Humans; Osteoblasts; Osteogenesis; Osteoprotegerin; Parathyroid Hormone; RANK Ligand; Receptor, Parathyroid Hormone, Type 1; Signal Transduction; Stimulation, Chemical

Thyroid hormone stimulates osteoclastic bone resorption, through increased expression of receptor activator of nuclear factor kappa B ligand (RANKL) in osteoblasts as well as via non-RANKL-mediated pathway. Therefore, in hyperthyroid patients with Graves' disease, bone resorption (urinary excretion of calcium, phosphate, deoxypyridinoline, N-terminal telopeptide of collagen type I) is increased. Due to accelerated bone remodeling, bone formation is also increased. However, the amount of bone formation is less than that of bone resorption, leading to a gradual decrease in bone mineral density (BMD). In young patients, the decreased BMD is reversible, but not in post-menopausal women. Therefore, in these patients with rapid bone looser, bisphosphonates may be beneficial treatment for prevention of osteoporosis and will prevent bone fractures in senile period.

Topics: Alkaline Phosphatase; Bone and Bones; Bone Density; Bone Remodeling; Bone Resorption; Diphosphonates; Female; Fractures, Bone; Graves Disease; Humans; Osteoblasts; Osteogenesis; Osteoporosis; Osteoprotegerin; RANK Ligand; Receptors, Thyroid Hormone

Drug treatment of osteoporosis is based on the knowledge of mechanisms of bone turnover and the manipulation of the cellular components of bone turnover in terms of recruitment, activation and apoptosis of the cells involved. Based on their mechanisms of action, drugs used in the treatment of osteoporosis can be divided into those that inhibit bone turnover (bisphosphonates, SERMs, calcitonin), those that stimulate bone turnover (parathyroid hormone), and those with mixed effects (strontium ranelate). In this chapter we discuss the anti-fracture effects of some newer drugs together with innovative aspects of intake (monthly oral intake for ibandronate) or mechanisms of action (parathyroid hormone and strontium ranelate). Some new drugs that are being studied for their potential anti-fracture effects are listed.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Bone Density; Bone Density Conservation Agents; Calcitonin; Denosumab; Diphosphonates; Fractures, Bone; Glycoproteins; Humans; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Ibandronic Acid; Imidazoles; Organometallic Compounds; Osteoporosis; Osteoprotegerin; Parathyroid Hormone; RANK Ligand; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Thiophenes; Zoledronic Acid

Osteoporosis is a disorder in which loss of bone strength leads to fragility fractures. This review examines the fundamental pathogenetic mechanisms underlying this disorder, which include: (a) failure to achieve a skeleton of optimal strength during growth and development; (b) excessive bone resorption resulting in loss of bone mass and disruption of architecture; and (c) failure to replace lost bone due to defects in bone formation. Estrogen deficiency is known to play a critical role in the development of osteoporosis, while calcium and vitamin D deficiencies and secondary hyperparathyroidism also contribute. There are multiple mechanisms underlying the regulation of bone remodeling, and these involve not only the osteoblastic and osteoclastic cell lineages but also other marrow cells, in addition to the interaction of systemic hormones, local cytokines, growth factors, and transcription factors. Polymorphisms of a large number of genes have been associated with differences in bone mass and fragility. It is now possible to diagnose osteoporosis, assess fracture risk, and reduce that risk with antiresorptive or other available therapies. However, new and more effective approaches are likely to emerge from a better understanding of the regulators of bone cell function.

Topics: Animals; Bone and Bones; Bone Density; Bone Remodeling; Calcium; Cell Differentiation; Collagen; Estrogens; Fractures, Bone; Glycoproteins; Hematopoietic Stem Cells; Hormones; Humans; Leptin; Ligands; Mice; Models, Biological; Neurons; NF-kappa B; Nitric Oxide; Osteoblasts; Osteoporosis; Osteoporosis, Postmenopausal; Osteoprotegerin; Parathyroid Hormone; Prostaglandins; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Vitamin D; Vitamin D Deficiency

To observe the clinical effect of estrogenic drugs (Bazedoxifene) on bone targeting in the treatment of osteoporosis and explore its mechanism.. 112 patients with postmenopausal osteoporosis who received Bazedoxifene drugs in our hospital from January to December 2018 were collected as a study group, and 56 patients treated with calcium alone were collected as a control group. the risk of adverse events such as bone mineral density, osteoprotegerin (OPG), insulin-like growth factor (IGF), tumor necrosis factor (TNF-α), and fracture after treatment were analyzed before and after treatment.. There was no significant difference in the mean lumbar positive position (L2-4) and right femoral neck bone density and OPG, IGF, TNF-α level between the two groups before treatment (P>0.05). The total effective rate of clinical treatment in the study group was 88.39%, the control group was 23.21%, the difference between the two groups was statistically significant (P˂0.05). After treatment, the mean lumbar positive position (L2-4) and the right femoral neck bone density and OPG, IGF in the study group were higher than those in the control group, lower than those in the control group (P<0.05). the occurrence of adverse events such as fracture, spinal deformation and fatigue in the study group after 12 months of treatment was significantly lower than that in the control group (P<0.05), but there was no significant difference in the occurrence of hot flashes and venous thromboembolism between the two groups (P>0.05).. Bazedoxifene is an effective drug for the treatment of postmenopausal osteoporosis. It can not only prevent the rapid loss of bone mass, effectively relieve the symptoms of menopause, but also improve bone density and reduce the risk of fracture.

Topics: Aged; Bone Density; Female; Fractures, Bone; Humans; Indoles; Insulin-Like Growth Factor I; Lumbar Vertebrae; Middle Aged; Orthotic Devices; Osteoprotegerin; Tumor Necrosis Factor-alpha

Using adult identified bone mineral density (BMD) loci, we calculated genetic risk scores (GRS) to determine if they were associated with changes in BMD during childhood. Longitudinal data from the Bone Mineral Density in Childhood Study were analyzed (N = 798, 54% female, all European ancestry). Participants had up to 6 annual dual energy X-ray scans, from which areal BMD (aBMD) Z-scores for the spine, total hip, and femoral neck were estimated, as well as total body less head bone mineral content (TBLH-BMC) Z-scores. Sixty-three single-nucleotide polymorphisms (SNPs) were genotyped, and the percentage of BMD-lowering alleles carried was calculated (overall adult GRS). Subtype GRS that include SNPs associated with fracture risk, pediatric BMD, WNT signaling, RANK-RANKL-OPG, and mesenchymal stem cell differentiation were also calculated. Linear mixed effects models were used to test associations between each GRS and bone Z-scores, and if any association differed by sex and/or chronological age. The overall adult, fracture, and WNT signaling GRS were associated with lower Z-scores (eg, spine aBMD Z-score: βadult  = -0.04, p = 3.4 × 10(-7) ; βfracture = -0.02, p = 8.9 × 10(-6) ; βWNT  = -0.01, p = 3.9 × 10(-4) ). The overall adult GRS was more strongly associated with lower Z-scores in females (p-interaction ≤ 0.05 for all sites). The fracture GRS was more strongly associated with lower Z-scores with increasing age (p-interaction ≤ 0.05 for all sites). The WNT GRS associations remained consistent for both sexes and all ages (p-interaction > 0.05 for all sites). The RANK-RANKL-OPG GRS was more strongly associated in females with increasing age (p-interaction < 0.05 for all sites). The mesenchymal stem cell GRS was associated with lower total hip and femoral neck Z-scores, in both boys and girls, across all ages. No associations were observed between the pediatric GRS and bone Z-scores. In conclusion, adult identified BMD loci associated with BMD and BMC in the pediatric setting, especially in females and in loci involved in fracture risk and WNT signaling.

Topics: Adolescent; Adult; Alleles; Bone Density; Cell Differentiation; Child; Female; Follow-Up Studies; Fractures, Bone; Humans; Male; Mesenchymal Stem Cells; Osteoprotegerin; RANK Ligand; Receptor Activator of Nuclear Factor-kappa B; Risk Assessment; Risk Factors; Sex Factors

The aim of this study is to identify the dependence of the result of surgical treatment of patients of elderly and senile age with fractures of the proximal femur on the characteristics of the response cytokine-mediated regulatory response to trauma and surgery.. Materials and methods: In 74 patients after hip arthroplasty, serum levels of bone metabolism markers were determined using enzyme-linked immunosorbent assay. Patients were divided into 2 groups depending on the results of treatment.. Results: It was found that compared with group 2 (treatment outcome is worse) in group 1 (treatment outcome is better) there was a greater number of correlations. In group 1, correlations were found between OPG and RANKL (r = 0.88; p = 0.000), OPG and OPG/RANKL (r = 0.44; p = 0.006), TGF-β1 and OPG/RANKL (r = 0.66; p = 0.000) , IL-6 and OPG (r = 0.67; p = 0.000), IL-6 and RANKL (r = 0.53; p = 0.001), IL-6 and OPG/RANKL (r = 0.39; p = 0.016). In group 2, only between OPG and OPG/RANKL (r = 0.72; p = 0.000), RANKL and OPG/RANKL (r = -0.53; p = 0.0007). In patients of group 2, there was a decrease in the level of OPG relative to the control and a less significant increase in TGF-β1 and IL-6 relative to group 1.. Conclusion: The prognosis of the results of treatment of patients with proximal femur fractures is largely determined by the nature of the adaptive response to injury and theimplant, the synchronism of the mechanism of stress remodeling of the bone. A less favorable prognosis after arthroplasty is associated with exacerbation of the initial metabolic disorders in the bone tissue due to severe cytokine-mediated dysfunction of the regulatory pathways.

Topics: Aged; Arthroplasty, Replacement, Hip; Bone Remodeling; Femur; Fractures, Bone; Humans; Osteoprotegerin; RANK Ligand

BACKGROUND Osteoporotic fractures are common in postmenopausal women and associated with complications. Numerous studies have demonstrated that icariin can be used to treat fractures and osteoporosis. Herein, we evaluated the efficacy of gavage-administered icariin to promote fracture healing in postmenopausal osteoporotic fracture (POF) rats. MATERIAL AND METHODS In this study, ovariectomy-induced POF rats were treated with 600 mg/kg icariin. Micro-computed tomography (micro-CT) was used to assess fracture healing; besides, serum APK, TRACP-5b, and E₂ expression levels were detected by commercial kits, and the uterine index was calculated. In addition, the expression of osteogenesis-related proteins (Runx 2 and COL1A2) in the callus was measured by western blot, whereas the expression of OPG/RANKL pathway proteins was measured by western blot and immunohistochemical analysis. RESULTS Our data revealed that icariin promoted the expression level of Runx 2 and COL1A2 and suppressed the expression level of serum bone turn over biomarkers via the OPG/RANKL pathway. Besides, a more mature callus was observed in the POF rats receiving icariin than in the untreated POF rats, while serum E₂ and uterine index were unaffected by icariin treatment. CONCLUSIONS These results revealed that icariin could promote fracture healing in ovariectomized rats via OPG/RANKL signaling, and that serum E₂ and uterine index were not affected by icariin treatment.

Topics: Animals; Bone and Bones; Bone Density; China; Female; Flavonoids; Fracture Healing; Fractures, Bone; Osteoporosis; Osteoporotic Fractures; Osteoprotegerin; Ovariectomy; RANK Ligand; Rats; Rats, Sprague-Dawley; X-Ray Microtomography

Fracture and hemorrhagic shock often lead to impaired fracture healing. To elucidate underlying pathogenesis, this study aimed to analyze histological properties during fracture healing after hemorrhagic shock and involved signaling pathways in mice.. Male C57BL/6NCrl mice were assigned into five groups. Control group underwent no interventions. Sham group had a catheter and external fixator but neither blood loss nor osteotomy. Trauma-hemorrhage (TH) group received a pressure-controlled hemorrhagic shock; osteotomy (Fx) group, an osteotomy and fixator; and combined trauma (THFx) group, both hemorrhagic shock and externally fixed osteotomy. After 1, 2, 3, and 4 weeks, the animals were killed. Undecalcified bones were analyzed histologically and signaling pathways relevant for fracture healing by polymerase chain reaction and Western blot. Statistical significance was set at 0.05 or less. Comparisons were performed using the Mann-Whitney U or Kruskal-Wallis test.. In the THFx group, a decreased bone formation after 3 weeks, a reduction of both bone and cartilage after 2 weeks, and an enhanced activation of the RANKL/OPG and IL6 signaling pathway after 1 week were shown in comparison to Fx.. Hemorrhagic shock has a retarding effect on fracture healing in the early phase of fracture healing and leads to activation of the IL6 and RANKL/OPG signaling pathways.

Topics: Animals; Bony Callus; Disease Models, Animal; Fracture Healing; Fractures, Bone; Interleukin-6; Male; Mice; Mice, Inbred C57BL; Osteoprotegerin; RANK Ligand; Shock, Hemorrhagic; Signal Transduction; Survival Rate

Fragility fractures and cardiovascular diseases often coincide. However, data on shared risk factors and markers are scarce. Our aim was to assess the independent associations of serum osteoprotegerin (OPG) levels with the risk of fracture and cardiovascular outcomes (acute coronary syndrome, cardiac death) in older men. A cohort of 819 home-dwelling men aged 60 to 87 years was followed prospectively for 8 years. Serum OPG was measured at baseline by ELISA. Bone mineral density (BMD) at femoral neck and Trabecular Bone Score (TBS) were assessed by DXA. Clinical risk factors and Fracture Risk Assessment Tool (FRAX) were assessed. The incident events (self-reported peripheral fractures and acute coronary syndrome, cardiac death reported by a proxy) confirmed by a health professional were retained for the statistical analysis. Incident vertebral fractures were assessed on lateral DXA scans after 4 and 8 years. Hazard risk (HR) was assessed using the Cox model. After adjustment for FRAX corrected for femoral neck BMD and TBS, diabetes mellitus, ischemic heart disease, and prior falls, the risk of fracture was twofold higher in the highest versus the lowest OPG quartile (HR 2.35; 95% CI, 1.35 to 4.10). The risk of vertebral and nonvertebral fracture was higher in the highest versus the lowest OPG quartile (OR 2.76 [95% CI, 1.08 to 7.05] and HR 2.46 [95% CI, 1.23 to 4.92]). The risk of major osteoporotic fracture was higher in the fourth versus the first OPG quartile (HR 2.43; 95% CI, 1.16 to 5.10). The risk of cardiovascular outcome (adjusted for confounders) was higher in the highest versus the lowest OPG quartile (HR 3.93; 95% CI, 1.54 to 10.04). The risk of fracture and cardiovascular outcome was higher in the highest OPG quartile versus the lower quartiles combined (HR 2.06 [95% CI, 1.35 to 3.14] and HR 2.98 [95% CI, 1.60 to 5.54], respectively). In conclusion, in older men, higher serum OPG levels represent an independent risk factor for cardiovascular and fracture risk. © 2017 American Society for Bone and Mineral Research.

Topics: Aged; Aged, 80 and over; Cardiovascular Diseases; Disease-Free Survival; Fractures, Bone; Humans; Male; Osteoprotegerin; Prospective Studies; Risk Factors

Splenectomy is sometimes required in bone fracture patients. The present study aims to investigate the effect of splenectomy on fracture healing in rats.. Rats underwent osteotomy were subjected to splenectomy. The effects of splenectomy were evaluated at day 0, 3, 15 and 30 post-fracture. Double immunofluorescence staining was used to examine the expression of macrophages marker F4/80 and CD11b. H&E staining was used to examine the histological changes in fracture sites. Western blotting was used to detect protein expression of osteoprotegerin (OPG), the ligand for receptor activator of NF-κB (RANKL) and collagens in the fracture site. Activity of alkaline phosphatase (ALP) in the serum was determined using a biochemical kit. Serum levels of osteocalcin and inflammatory cytokines were determined using ELISA kits. Real-time PCR was used to detect mRNA expression of ALP and osteocalcin in the fracture site.. Results showed that the recruitment of macrophages and the production of inflammatory cytokines were inhibited in the fracture rats underwent splenectomy. Importantly, histological examination showed that fracture healing was delayed in splenectomized rats. In addition, the protein expression of OPG and RANKL in the fracture site was diminished, the activity of ALP and the level of osteocalcin in the serum and their mRNA expression in the fracture site were reduced, and the protein expression of type I collage a1 and type II collage a1 was inhibited in fracture rats underwent splenectomy compared with that in rats without splenectomy.. Our findings indicate that splenectomy delays fracture healing.

Topics: Alkaline Phosphatase; Animals; Fracture Healing; Fractures, Bone; Gene Expression Regulation; Macrophages; Male; Osteoprotegerin; RANK Ligand; Rats; Rats, Sprague-Dawley; Splenectomy

Osteoporosis is a common disease that is characterized by low bone mineral density (BMD), deterioration in bone microarchitecture, and increased fracture risk. Due to its important role in bone biology, the TNFRSF11B gene, coding for OPG, has been considered as a candidate gene for osteoporosis. In this study, single nucleotide polymorphisms (SNPs) A163G, T245G, and G1181C (rs3102735, rs3134069, and rs2073618, respectively) within the TNFRSF11B gene were studied for association with BMD and fracture incidence in a cohort of 327 postmenopausal Slovak women. Genomic DNA was extracted and purified from peripheral blood leukocytes by the commercial kit JetQuick (Genomed GmbH, Germany) using a standard protocol. Genotyping was performed using the Custom TaqMan® SNP Genotyping Assays. The lumbar L1-L4 spine BMD (g/cm(2)) and T-score in the subgroup of Slovak postmenopausal women with osteoporotic fractures were significantly lower than those in the subgroup of women without fracture (p = 0.0025; p = 0.0009). We identified the T245G (rs3134069) polymorphism in the TNFRSF11B gene associated with osteoporotic fractures (vertebral fractures: p = 0.0320; non-vertebral fractures: p = 0.0005; all fractures: 0.0000). The polymorphism T245G (rs3134069) in the TNFRSF11B gene could be used together with other genetic markers to identify individuals at high risk of osteoporotic fractures. The results from the present study provided more evidence to reveal the role of TNFRSF11B gene polymorphisms in BMD and the risk of osteoporotic fractures.

Topics: Adult; Aged; Aged, 80 and over; Bone Density; Fractures, Bone; Gene Frequency; Genetic Association Studies; Genotype; Humans; Middle Aged; Osteoporosis, Postmenopausal; Osteoprotegerin; Polymorphism, Single Nucleotide; Postmenopause; Slovakia

Osteoprotegerin (OPG) plays an important role in the osteoclast differentiation as an effective inhibitor of osteoclast maturation and activation. We examined a potential effect of A163G single nucleotide polymorphism in the promoter region of the OPG gene on femoral neck (FN-BMD) and lumbar spine BMD (LS-BMD), as well as circulating alkaline phosphatase, osteocalcin (ALP, OC; formation markers), beta-CrossLaps (CTx; resorption marker) in Slovak postmenopausal women. In addition, fractures of spine, radius and femur were examined.Altogether 284 women (62.28 ± 8.40 years) were selected according to strict inclusion criteria. The polymorphism was detected by PCR-RFLP method. Genotype frequencies were tested using the chi-square test. The differences of quantitative variables between the genotypes were analyzed by covariance analysis (GLM procedure) after correction of the measurements for age and BMI. Fracture incidence in association with OPG genotype was evaluated by Binary Logistic Regression with the genotype, age, and BMI as covariates. The frequencies of genotypes were 76.8 %, 21.1 %, and 2.1 % for AA, AG, and GG, respectively. Statistically significant associations of OPG genotypes with FN-BMD (p < 0.01) and LS-BMD (p < 0.05) were observed. The GG genotype was associated with higher BMD values likewise decreased CTx concentration (p < 0.05) in compared with the other genotypes, which indicates that the allele G has a protective effect on bone. These associations were not followed by the effect of OPG on fracture incidence. Our results suggest that OPG/A163G polymorphism could contribute to the genetic regulation of BMD or bone turnover markers in Slovak population and thus could increase or decreased osteoporosis risk.

Topics: Aged; Anthropology, Medical; Body Mass Index; Cohort Studies; Female; Fractures, Bone; Humans; Middle Aged; Osteoporosis; Osteoprotegerin; Polymorphism, Single Nucleotide; Postmenopause; Slovakia

Fractures are common in men and women with chronic kidney disease (CKD) but the best tool to identify those at high risk is unknown. Increased circulating osteoprotegerin(OPG) is associated with fractures in postmenopausal women. We determined if serum OPG was associated with prevalent fractures (self-reported low trauma fractures since 40 years of age and/or prevalent vertebral fractures identified by radiographs) in men (n = 97) and women (n = 67) with stage 3–5 CKD. Analyses were performed unadjusted and adjusted for stage of CKD. Results are expressed as mean ± standard deviation(SD), and as odds ratio (OR) per SD increase in OPG with 95 % confidence intervals (CI). The mean age was 62.7 ± 16.3 years, and mean weight was 78.9 ± 18.7 kg. Compared to those without fractures, those with fractures(n = 55) were older (p < 0.01). Serum OPG increased as kidney function decreased, and OPG was higher in those with fractures compared to those without (9.42 ± 4.08 vs 8.06 ± 3.11 pmol/L, p = 0.02). After adjusting for stage of CKD, increased OPG was associated with an increased fracture risk (OR 1.13, 95 % CI 1.02–1.25); however, OPG did not discriminate fracture status well (area under the receiver operating characteristic curve 0.61, 95 % CI 0.52–0.70). OPG is associated with fractures in men and women with stage 3–5 CKD; however, the ability of OPG to discriminate fracture status is poor and cannot be used in isolation to assess fracture risk. Further studies should examine the ability of OPG in combination with other risk factors to better discriminate fracture status in men and women with CKD.

Topics: Aged; Calcium; Female; Fractures, Bone; Humans; Male; Middle Aged; Osteoprotegerin; Parathyroid Hormone; Phosphates; Renal Insufficiency, Chronic

Fracture healing is a regenerative process in which bone is restored without scar tissue formation. The healing cascade initiates with a cycle of inflammation, cell migration, proliferation and differentiation. Immune cells invade the fracture site immediately upon bone damage and contribute to the initial phase of the healing process by recruiting accessory cells to the injury site. However, little is known about the role of the immune system in the later stages of fracture repair, in particular, whether lymphocytes participate in soft and hard callus formation. In order to answer this question, we analyzed femoral fracture healing in mice by confocal microscopy. Surprisingly, after the initial inflammatory phase, when soft callus developed, T and B cells withdrew from the fracture site and were detectable predominantly at the femoral neck and knee. Thereafter lymphocytes massively infiltrated the callus region (around day 14 after injury), during callus mineralization. Interestingly, lymphocytes were not found within cartilaginous areas of the callus but only nearby the newly forming bone. During healing B cell numbers seemed to exceed those of T cells and B cells progressively underwent effector maturation. Both, osteoblasts and osteoclasts were found to have direct cell-cell contact with lymphocytes, strongly suggesting a regulatory role of the immune cells specifically in the later stages of fracture healing.

Topics: Animals; B-Lymphocytes; Base Sequence; Bony Callus; DNA Primers; Flow Cytometry; Fracture Healing; Fractures, Bone; Mice; Mice, Inbred C57BL; Osteoprotegerin; Polymerase Chain Reaction; RANK Ligand; T-Lymphocytes

The WNT16 locus is a major determinant of cortical bone thickness and nonvertebral fracture risk in humans. The disability, mortality and costs caused by osteoporosis-induced nonvertebral fractures are enormous. We demonstrate here that Wnt16-deficient mice develop spontaneous fractures as a result of low cortical thickness and high cortical porosity. In contrast, trabecular bone volume is not altered in these mice. Mechanistic studies revealed that WNT16 is osteoblast derived and inhibits human and mouse osteoclastogenesis both directly by acting on osteoclast progenitors and indirectly by increasing expression of osteoprotegerin (Opg) in osteoblasts. The signaling pathway activated by WNT16 in osteoclast progenitors is noncanonical, whereas the pathway activated in osteoblasts is both canonical and noncanonical. Conditional Wnt16 inactivation revealed that osteoblast-lineage cells are the principal source of WNT16, and its targeted deletion in osteoblasts increases fracture susceptibility. Thus, osteoblast-derived WNT16 is a previously unreported key regulator of osteoclastogenesis and fracture susceptibility. These findings open new avenues for the specific prevention or treatment of nonvertebral fractures, a substantial unmet medical need.

Topics: Aging; Animals; Cell Differentiation; Cell Line; Cell Lineage; Cells, Cultured; Disease Susceptibility; Fractures, Bone; Gene Deletion; Gene Expression Regulation; Humans; Mice, Inbred C57BL; Organ Size; Osteoblasts; Osteoclasts; Osteocytes; Osteogenesis; Osteoprotegerin; RANK Ligand; RNA, Messenger; Signal Transduction; Skull; Wnt Proteins

Topics: Adrenal Cortex Hormones; Adult; Aged; Arthritis, Psoriatic; Bone Density; Case-Control Studies; Cross-Sectional Studies; Densitometry; Female; Fractures, Bone; Humans; Immunosuppressive Agents; Male; Middle Aged; Osteoporosis; Osteoprotegerin; Postmenopause; Premenopause; Prevalence; RANK Ligand; Tumor Necrosis Factor-alpha

The first objective was to investigate new bone formation in a critical-size metaphyseal defect in the femur of ovariectomized rats filled with a strontium modified calcium phosphate cement (SrCPC) compared to calcium phosphate cement (CPC) and empty defects. Second, detection of strontium release from the materials as well as calcium and collagen mass distribution in the fracture defect should be targeted by time of flight secondary ion mass spectrometry (TOF-SIMS). 45 female Sprague-Dawley rats were randomly assigned to three different treatment groups: (1) SrCPC (n = 15), (2) CPC (n = 15), and (3) empty defect (n = 15). Bilateral ovariectomy was performed and three months after multi-deficient diet, the left femur of all animals underwent a 4 mm wedge-shaped metaphyseal osteotomy that was internally fixed with a T-shaped plate. The defect was then either filled with SrCPC or CPC or was left empty. After 6 weeks, histomorphometric analysis showed a statistically significant increase in bone formation of SrCPC compared to CPC (p = 0.005) and the empty defect (p = 0.002) in the former fracture defect zone. Furthermore, there was a statistically significant higher bone formation at the tissue-implant interface in the SrCPC group compared to the CPC group (p < 0.0001). These data were confirmed by immunohistochemistry revealing an increase in bone-morphogenic protein 2, osteocalcin and osteoprotegerin expression and a statistically significant higher gene expression of alkaline phosphatase, collagen10a1 and osteocalcin in the SrCPC group compared to CPC. TOF-SIMS analysis showed a high release of Sr from the SrCPC into the interface region in this area compared to CPC suggesting that improved bone formation is attributable to the released Sr from the SrCPC.

Topics: Alkaline Phosphatase; Animals; Biocompatible Materials; Bone Cements; Bone Morphogenetic Protein Receptors, Type II; Calcium Phosphates; Endpoint Determination; Female; Femur; Fractures, Bone; Immunohistochemistry; Osteocalcin; Osteogenesis; Osteoprotegerin; Ovariectomy; Rats; Rats, Sprague-Dawley; Strontium

Low bone mass and increased fracture risk are recognized complications of cystic fibrosis (CF). CF-related bone disease (CFBD) is characterized by uncoupled bone turnover--impaired osteoblastic bone formation and enhanced osteoclastic bone resorption. Intestinal malabsorption, vitamin D deficiency and inflammatory cytokines contribute to CFBD. However, epidemiological investigations and animal models also support a direct causal link between inactivation of skeletal cystic fibrosis transmembrane regulator (CFTR), the gene that when mutated causes CF, and CFBD. The objective of this study was to examine the direct actions of CFTR on bone. Expression analyses revealed that CFTR mRNA and protein were expressed in murine osteoblasts, but not in osteoclasts. Functional studies were then performed to investigate the direct actions of CFTR on osteoblasts using a CFTR knockout (Cftr-/-) mouse model. In the murine calvarial organ culture assay, Cftr-/- calvariae displayed significantly less bone formation and osteoblast numbers than calvariae harvested from wildtype (Cftr+/+) littermates. CFTR inactivation also reduced alkaline phosphatase expression in cultured murine calvarial osteoblasts. Although CFTR was not expressed in murine osteoclasts, significantly more osteoclasts formed in Cftr-/- compared to Cftr+/+ bone marrow cultures. Indirect regulation of osteoclastogenesis by the osteoblast through RANK/RANKL/OPG signaling was next examined. Although no difference in receptor activator of NF-κB ligand (Rankl) mRNA was detected, significantly less osteoprotegerin (Opg) was expressed in Cftr-/- compared to Cftr+/+ osteoblasts. Together, the Rankl:Opg ratio was significantly higher in Cftr-/- murine calvarial osteoblasts contributing to a higher osteoclastogenesis potential. The combined findings of reduced osteoblast differentiation and lower Opg expression suggested a possible defect in canonical Wnt signaling. In fact, Wnt3a and PTH-stimulated canonical Wnt signaling was defective in Cftr-/- murine calvarial osteoblasts. These results support that genetic inactivation of CFTR in osteoblasts contributes to low bone mass and that targeting osteoblasts may represent an effective strategy to treat CFBD.

Topics: Animals; Bone Diseases; Bone Resorption; Cell Differentiation; Cystic Fibrosis; Cystic Fibrosis Transmembrane Conductance Regulator; Disease Models, Animal; Female; Fractures, Bone; Gene Expression; Mice; Mice, Knockout; Osteoblasts; Osteoclasts; Osteogenesis; Osteoprotegerin; Parathyroid Hormone; Wnt Signaling Pathway

Connexin 43 (Cx43) is the most abundant gap junction protein in bone and is required for osteoblastic differentiation and bone homeostasis. During fracture healing, Cx43 is abundantly expressed in osteoblasts and osteocytes, while Cx43 deficiency impairs bone formation and healing. In the present study we selectively deleted Cx43 in the osteoblastic lineage from immature osteoblasts through osteocytes and tested the hypothesis that Cx43 deficiency results in delayed osteoblastic differentiation and impaired restoration of biomechanical properties due to attenuated β-catenin expression relative to wild type littermates. Here we show that Cx43 deficiency results in alterations in the mineralization and remodeling phases of healing. In Cx43 deficient fractures the mineralization phase is marked by delayed expression of osteogenic genes. Additionally, the decrease in the RankL/Opg ratio, osteoclast number and osteoclast size suggest decreased osteoclast bone resorption and remodeling. These changes in healing result in functional deficits as shown by a decrease in ultimate torque at failure. Consistent with these impairments in healing, β-catenin expression is attenuated in Cx43 deficient fractures at 14 and 21 days, while Sclerostin (Sost) expression, a negative regulator of bone formation is increased in Cx43cKO fractures at 21 days, as is GSK-3β, a key component of the β-catenin proteasomal degradation complex. Furthermore, we show that alterations in healing in Cx43 deficient fractures can be rescued by inhibiting GSK-3β activity using Lithium Chloride (LiCl). Treatment of Cx43 deficient mice with LiCl restores both normal bone formation and mechanical properties relative to LiCl treated WT fractures. This study suggests that Cx43 is a potential therapeutic target to enhance fracture healing and identifies a previously unknown role for Cx43 in regulating β-catenin expression and thus bone formation during fracture repair.

Topics: Adaptor Proteins, Signal Transducing; Animals; beta Catenin; Biomechanical Phenomena; Bony Callus; Calcification, Physiologic; Connexin 43; Female; Femur; Fracture Healing; Fractures, Bone; Gene Expression Regulation; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Glycoproteins; Intercellular Signaling Peptides and Proteins; Lithium Chloride; Mice; Mice, Knockout; Osteoblasts; Osteocytes; Osteoprotegerin; RANK Ligand; Signal Transduction; Torque

Proton pump inhibitors (PPIs) are widely used against gastroesophageal reflux disease. Recent epidemiological studies suggest that PPI users have an increased risk of fractures, but a causal relationship has been questioned. We have therefore investigated the skeletal phenotype in H(+) /K(+) ATPase beta-subunit knockout (KO) female mice. Skeletal parameters were determined in 6- and 20-month-old KO mice and in wild-type controls (WT). Whole body bone mineral density (BMD) and bone mineral content (BMC) were measured by dual energy X-ray absorptiometry (DXA). Femurs were examined with µCT analyses and break force were examined by a three-point bending test. Plasma levels of gastrin, RANKL, OPG, osteocalcin, leptin, and PTH were analyzed. KO mice had lower whole body BMC at 6 months (0.53 vs. 0.59 g, P = 0.035) and at 20 months (0.49 vs. 0.74 g, P < 0.01) compared to WT as well as lower BMD at 6 months (0.068 vs. 0.072 g/cm(2) , P = 0.026) and 20 months (0.067 vs. 0.077 g/cm(2) , P < 0.01). Mechanical strength was lower in KO mice at the age of 20 months (6.7 vs. 17.9 N, P < 0.01). Cortical thickness at 20 months and trabecular bone volume% at 6 months were significantly reduced in KO mice. Plasma OPG/RANKL ratio and PTH was increased in KO mice compared to controls. H(+) /K(+) ATPase beta subunit KO mice had decreased BMC and BMD, reduced cortical thickness and inferior mechanical bone strength. Whereas the mechanism is uncertain, these findings suggest a causal relationship between long-term PPI use and an increased risk of fractures.

Topics: Absorptiometry, Photon; Animals; Bone and Bones; Bone Density; Female; Fractures, Bone; Gastrins; Leptin; Mice; Mice, Inbred BALB C; Mice, Knockout; Mitochondrial Proton-Translocating ATPases; Osteocalcin; Osteoprotegerin; Parathyroid Hormone; Protein Subunits; Proton Pump Inhibitors; RANK Ligand; Risk

Osteoblasts are specialized cells that form new bone and also indirectly influence bone resorption by producing factors that modulate osteoclast differentiation. Although the methylation of CpG islands plays an important role in the regulation of gene expression, there is still scanty information about its role in human bone. The aim of this study was to investigate the influence of CpG methylation on the transcriptional levels of two osteoblast-derived critical factors in the regulation of osteoclastogenesis: the receptor activator of nuclear factor NF-κB ligand (RANKL) and its soluble decoy receptor osteoprotegerin (OPG). Quantitative methylation specific PCR (qMSP) and pyrosequencing analysis in various cell types showed that the methylation of regulatory regions of these genes, in the vicinity of the transcription start sites, repressed gene transcription, whereas an active transcription was associated with low levels of methylation. In addition, treatment with the DNA demethylating agent 5-azadeoxycitidine promoted a 170-fold induction of RANKL and a 20-fold induction of OPG mRNA expression in HEK-293 cells, which showed hypermethylation of the CpG islands and barely expressed RANKL and OPG transcripts at baseline. Transcriptional levels of both genes were also explored in bone tissue samples from patients with hip fractures and hip osteoarthritis. Although RANKL transcript abundance and the RANKL:OPG transcript ratio were significantly higher in patients with fractures than in those with osteoarthritis (RANKL: 0.76 ± 0.23 vs. 0.24 ± 0.08, p = 0.012; RANKL/OPG: 7.66 ± 2.49 vs. 0.92 ± 0.21, p = 0.002), there was no evidence for differential methylation across patient groups. In conclusion, the association between DNA methylation and the repression of RANKL and OPG expression strongly suggests that methylation-dependent mechanisms influence the transcription of these genes, which play a critical role in osteoclastogenesis. However, other mechanisms appear to be involved in the increased RANKL/OPG ratio of patients with osteoporotic fractures.

Topics: Aged; Aged, 80 and over; Cell Line; CpG Islands; DNA Methylation; Female; Fractures, Bone; Gene Expression Regulation; Humans; Male; Osteoporosis; Osteoprotegerin; RANK Ligand

Primary hyperparathyroidism (PHPT) affects mainly cortical bone. It is thought that parathyroid hormone (PTH) indirectly regulates the activity of osteoclasts by means of the osteoprotegerin/ligand of the receptor activator of nuclear factor-κβ (OPG/RANKL) system. Several studies have confirmed that OPG (osteoprotegerin) and RANKL (ligand of the receptor activator of nuclear factor-κβ) loci are determinants of bone mineral density (BMD) in the general population. The aim of this study is to analyze the relationship between fractures and BMD and the rs3102735 (163 A/G), rs3134070 (245 T/G) and rs2073618 (1181 G/C) SNPs of the OPG and the rs2277438 SNP of the RANKL, in patients with sporadic PHPT.. We enrolled 298 Caucasian patients with PHPT and 328 healthy volunteers in a cross-sectional study. We analyzed anthropometric data, history of fractures or renal lithiasis, biochemical determinants including markers for bone remodelling, BMD measurements in the lumbar spine, total hip, femoral neck and distal radius, and genotyping for the SNPs to be studied.. Regarding the age of diagnosis, BMI, menopause status, frequency of fractures or renal lithiasis, we found no differences between genotypes in any of the SNPs studied in the PHPT group. Significant lower BMD in the distal radius with similar PTH levels was found in the minor allele homozygotes (GG) compared to heterozygotes and major allele homozygotes in both OPG rs3102735 (163 A/G) and OPG rs3134070 (245 T/G) SNPs in those with PHPT compared to control subjects. We found no differences between genotypes of the OPG rs2073618 (1181 G/C) SNP with regard to BMD in the PHPT subjects. In the evaluation of rs2277438 SNP of the RANKL in PHPT patients, we found a non significant trend towards lower BMD in the 1/3 distal radius and at total hip in the minor allele homocygotes (GG) genotype group versus heterocygotes and major allele homocygotes (AA).. Our study provides the first evaluation of the relationship between SNPs of the OPG/RANK system and sporadic PHPT. Subjects with PHPT and minor homocygote genotype (GG) for the OPG rs3102735 (163 A/G) and OPG rs3134070 (245 T/G) SNPs have lower BMD in the distal radius, and this association does not appear to be mediated by differences in PTH serum levels.

Topics: Adult; Aged; Alleles; Bone Density; Cross-Sectional Studies; Female; Fractures, Bone; Genotype; Homozygote; Humans; Hyperparathyroidism, Primary; Lithiasis; Male; Middle Aged; Odds Ratio; Osteoprotegerin; Parathyroid Hormone; Polymorphism, Single Nucleotide; RANK Ligand

Receptor activator of nuclear factor-kappaB ligand/osteoprotegerin (RANKL/OPG) signaling system plays a crucial role in the regulation of bone resorption. Polymorphic variations in the genes may have an influence on gene expression and bone metabolism. In the present study, we aimed to investigate the influence of RANKL/OPG allelic variations on the in vivo human gene expression of five genes, bone mineral density (BMD), and fracture incidence in Hungarian postmenopausal women.. Three hundred and sixty postmenopausal women (61.6+/-7.9 years) were genotyped. All together, five single nucleotide polymorphisms (SNPs) in the two genes have been investigated. In addition, bone samples from 17 examined subjects were acquired for gene expression studies. Bone densities and fracture data have also been collected.. All two SNPs in OPG gene and three SNPs in RANKL gene showed correlation with BMD. Haplotype analysis of these genes gave similar results. The 'CCT' haplotype of RANKL promoter region, which was associated with decreased BMD, exhibited a significantly upregulated expression of RANKL mRNA, while the other haplotypes of RANKL or OPG 15 genes did not. No correlation between genetic variations and fracture data was found.. We have demonstrated associations between RANKL and OPG haplotypes and BMD as well as between RANKL haplotypes and in vivo RANKL expression in a Hungarian postmenopausal population. Moreover, we have found a new RANKL haplotype associating with reduced BMD and increased in vivo RANKL expression in human bone tissue.

Topics: Aged; Alleles; Bone Density; Female; Fractures, Bone; Gene Expression; Genetic Variation; Haplotypes; Humans; Incidence; Middle Aged; Osteoprotegerin; Polymorphism, Single Nucleotide; Postmenopause; RANK Ligand; Signal Transduction

Increased osteoprotegerin (OPG) with elevated bone turnover is supposed to be a homeostatic mechanism limiting bone loss.. Whether osteoprotegerin relates to low-energy fracture in elderly women was investigated by analyzing the relationship between OPG and bone turnover. Sixty-nine women with a first fragility hip fracture participated. The reference group consisted of 23 age-matched women. Serum calcium, 25-OHD3, parathormone, osteocalcin (OC), cross-linked C-terminal telopeptides (CTX-I), tartrate-resistant acid phosphatase (TRAP5b), and osteoprotegerin were assayed immediately post-fracture.. In both groups, median vitamin D and calcium concentrations were in the low reference range, CTX-I were moderately elevated, and TRAP5b activity and parathormone were within the reference range. Significantly lower osteocalcin, a trend to higher OPG, and an inverse correlation between OPG and osteocalcin was found in the fracture group. The distribution of fracture was related to osteocalcin and OPG concentrations: the lower the OC level, the higher the number of women with fracture at increasing OPG concentrations. A relative imbalance between bone formation and resorption was found in the fracture group. The lowest osteocalcin level (Q1) was observed only and vitamin 25-OHD3 insufficiency predominantly in the fracture group and higher OPG, TRAP5b, and elevated CTX-I concentrations (Q3) were found more often or predominantly in this group.. The data demonstrate a relative imbalance between bone formation and resorption associated with fragility fracture in elderly women with low vitamin D status. The authors suggest that compensatory elevation of serum OPG, particularly with reduced bone formation, is insufficient to limit bone loss leading to fracture.

Topics: Aged; Aged, 80 and over; Female; Fractures, Bone; Humans; Middle Aged; Osteocalcin; Osteoprotegerin; Vitamin D

During bone remodeling, bone-resorbing osteoclasts and bone-forming osteoblasts are organized in bone multicellular units (BMUs), which travel at a rate of 20-40 mum/d for 6-12 mo, maintaining a cylindrical structure. However, the interplay of local BMU geometry with biochemical regulation is poorly understood. We developed a mathematical model of BMU describing changes in time and space of the concentrations of proresorptive cytokine RANKL and its inhibitor osteoprotegerin (OPG), in osteoclast and osteoblast numbers, and in bone mass. We assumed that osteocytes surrounding a microfracture produce RANKL, which attracted osteoclasts. OPG and RANKL were produced by osteoblasts and diffused through bone, RANKL was eliminated by binding to OPG and RANK. Osteoblasts were coupled to osteoclasts through paracrine factors. The evolution of the BMU arising from this model was studied using numerical simulations. Our model recapitulated the spatio-temporal dynamics observed in vivo in a cross-section of bone. In response to a RANKL field, osteoclasts moved as a well-confined cutting cone. The coupling of osteoclasts to osteoblasts allowed for sufficient recruitment of osteoblasts to the resorbed surfaces. The RANKL field was the highest at the microfracture in front of the BMU, whereas the OPG field peaked at the back of the BMU, resulting in the formation of a RANKL/OPG gradient, which strongly affected the rate of BMU progression and its size. Thus, the spatial organization of a BMU provides important constraints on the roles of RANKL and OPG as well as possibly other regulators in determining the outcome of remodeling in the BMU.

Topics: Bone and Bones; Computer Simulation; Fractures, Bone; Models, Biological; Osteoblasts; Osteoprotegerin; RANK Ligand; Solubility; Time Factors

The high incidence of bone disease and the increasing evidence of Crohn's disease (CD) bone decline in corticosteroid users and nonusers suggest that bone metabolism is affected by inflammatory process. The aim of the study was to compare serum levels of proinflammatory cytokines, markers of bone turnover and regulatory molecules of osteoclast biogenesis, receptor activator of nuclear factor kappaB-ligand (RANKL) and osteoprotegerin (OPG), between naïve and long-standing CD patients.. The study included 95 CD patients, 15 of them with newly diagnosed and previously untreated CD. The spine and hip bone mineral density was measured by dual-energy X-ray absorptiometry. Biochemical markers were determined by immunoassay.. Osteopenia was recorded at diagnosis in 53% of naïve patients and osteoporosis was found in 26% of long-standing CD patients. The newly diagnosed patients showed correlation between TNF-alpha and soluble RANKL (sRANKL) (r=0.5; P=0.04), and this positive relationship characterized the study population as a whole (r=0.3; P=0.003). Analysis of the OPG and sRANKL relationship showed absence of correlation in patients with healthy skeleton, whereas an inverse correlation was found in those with osteopenia (r=-0.31; P=0.033) and osteoporosis (r=-0.48; P=0.028). In naïve patients with reduced T score, the correlation between sRANKL and OPG was highly inverse (r=-0.8; P=0.02) and these patients were characterized by lower BMI, significantly higher level of proinflammatory cytokines, elevated C-reactive protein, and increased activity of free sRANKL and OPG.. Bone disease that accompanies CD at diagnosis suggests that bone metabolism is affected by the underlying inflammatory process per se, as probably confirmed by our finding of the central proinflammatory cytokine TNF-alpha being strongly associated with the osteoclastogenic mediator RANKL, and inversely with bone density.

Topics: Adolescent; Adult; Biomarkers; Bone Density; Bone Diseases, Metabolic; Bone Remodeling; Collagen Type I; Crohn Disease; Cytokines; Female; Fractures, Bone; Glucocorticoids; Humans; Inflammation Mediators; Male; Osteocalcin; Osteoporosis; Osteoprotegerin; Peptide Fragments; Peptides; Procollagen; RANK Ligand; Young Adult

Receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG), a decoy receptor of RANKL, maintain bone mass by regulating the differentiation of osteoclasts, which are bone-resorbing cells. Endochondral bone ossification and bone fracture healing involve cartilage resorption, a less well-understood process that is needed for replacement of cartilage by bone. Here we describe the role of OPG produced by chondrocytes in chondroclastogenesis. Fracture healing in OPG(-/-) mice showed faster union of the fractured bone, faster resorption of the cartilaginous callus, and an increased number of chondroclasts at the chondroosseous junctions compared with that in wild-type littermates. When a cultured pellet of OPG(-/-) chondrocytes was transplanted beneath the kidney capsule, the pellet recruited many chondroclasts. The pellet showed the ability to induce tartrate-resistant acid phosphatase-positive multinucleated cells from RAW 264.7 cells in vitro. Finally, OPG(-/-) chondrocytes (but not wild-type chondrocytes) cultured with spleen cells induced many tartrate-resistant acid phosphatase-positive multinucleated cells. The expression of RANKL and OPG in chondrocytes was regulated by several osteotropic factors including 1,25-dihydroxyvitamin D(3), PTHrP, IL-1alpha, and TNF-alpha. Thus, local OPG produced by chondrocytes probably controls cartilage resorption as a negative regulator for chondrocyte-dependent chondroclastogenesis.

Topics: Animals; Cartilage; Cell Line; Cells, Cultured; Chondrocytes; Female; Fracture Healing; Fractures, Bone; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Osteoprotegerin; RANK Ligand

Several reports indicated that interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF- alpha) play important regulatory roles in bone remodeling and homeostasis. In addition, receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoprotegerin (OPG) have been shown to be important regulators of osteoclastogenesis during bone remodeling, and their expressions were examined during fracture healing in a mouse model of tibial fracture. However, studies linking RANKL, OPG, IL-6 and TNF-alpha in patients with head injury and fracture are lacking.. Within the first few hours of admission to hospital and at 4, 8, and 12 weeks after the injury, we evaluated changes in serum levels of RANKL, OPG, IL-6 and TNF-alpha in 24 male patients with a concomitant head injury and fracture and in 26 male patients with fracture only. These levels were compared with those found in 36 healthy controls.. The RANKL/OPG ratios were found to significantly lower in patients with a concomitant head injury and fracture than in the controls immediately after admission and at 4, 8, and 12 weeks after the injury. In addition, RANKL/OPG ratios were significantly lower in patients with a concomitant head injury and fracture than in those with fracture at 8 and 12 weeks after the injury. The serum IL-6 levels were significantly higher in patients with a concomitant head injury and fracture than in the controls upon admission, and at 4, 8, and 12 weeks after the injury. Moreover, the serum IL-6 levels were significantly higher in patients with a head injury and fracture than in those with just a fracture at 4, 8, and 12 weeks after the injury.. Based on these changes in the profiles of RANKL, OPG, and IL-6 and the RANKL/OPG ratio, altered repair of a fracture can occur in patients with a concomitant head injury and fracture.

Topics: Adult; Comorbidity; Craniocerebral Trauma; Femoral Fractures; Fracture Healing; Fractures, Bone; Glasgow Coma Scale; Hematoma, Subdural; Humans; Humeral Fractures; Interleukin-6; Intracranial Hemorrhage, Traumatic; Male; Middle Aged; Osteoprotegerin; RANK Ligand; Tibial Fractures; Tumor Necrosis Factor-alpha; Young Adult

Topics: Bone Density; Fractures, Bone; Humans; LDL-Receptor Related Proteins; Low Density Lipoprotein Receptor-Related Protein-5; Osteoporosis; Osteoprotegerin; Risk Factors

Bone mineral density influences the risk of osteoporosis later in life and is useful in the evaluation of the risk of fracture. We aimed to identify sequence variants associated with bone mineral density and fracture.. We performed a quantitative trait analysis of data from 5861 Icelandic subjects (the discovery set), testing for an association between 301,019 single-nucleotide polymorphisms (SNPs) and bone mineral density of the hip and lumbar spine. We then tested for an association between 74 SNPs (most of which were implicated in the discovery set) at 32 loci in replication sets of Icelandic, Danish, and Australian subjects (4165, 2269, and 1491 subjects, respectively).. Sequence variants in five genomic regions were significantly associated with bone mineral density in the discovery set and were confirmed in the replication sets (combined P values, 1.2x10(-7) to 2.0x10(-21)). Three regions are close to or within genes previously shown to be important to the biologic characteristics of bone: the receptor activator of nuclear factor-kappaB ligand gene (RANKL) (chromosomal location, 13q14), the osteoprotegerin gene (OPG) (8q24), and the estrogen receptor 1 gene (ESR1) (6q25). The two other regions are close to the zinc finger and BTB domain containing 40 gene (ZBTB40) (1p36) and the major histocompatibility complex region (6p21). The 1p36, 8q24, and 6p21 loci were also associated with osteoporotic fractures, as were loci at 18q21, close to the receptor activator of the nuclear factor-kappaB gene (RANK), and loci at 2p16 and 11p11.. We have discovered common sequence variants that are consistently associated with bone mineral density and with low-trauma fractures in three populations of European descent. Although these variants alone are not clinically useful in the prediction of risk to the individual person, they provide insight into the biochemical pathways underlying osteoporosis.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Australia; Bone Density; Denmark; Estrogen Receptor alpha; Female; Fractures, Bone; Genotype; Humans; Iceland; Linear Models; Male; Middle Aged; Osteoporosis; Osteoprotegerin; Polymorphism, Single Nucleotide; Quantitative Trait Loci; RANK Ligand

Osteoporosis is diagnosed by the measurement of bone mineral density, which is a highly heritable and multifactorial trait. We aimed to identify genetic loci that are associated with bone mineral density.. In this genome-wide association study, we identified the most promising of 314 075 single nucleotide polymorphisms (SNPs) in 2094 women in a UK study. We then tested these SNPs for replication in 6463 people from three other cohorts in western Europe. We also investigated allelic expression in lymphoblast cell lines. We tested the association between the replicated SNPs and osteoporotic fractures with data from two studies.. We identified genome-wide evidence for an association between bone mineral density and two SNPs (p<5x10(-8)). The SNPs were rs4355801, on chromosome 8, near to the TNFRSF11B (osteoprotegerin) gene, and rs3736228, on chromosome 11 in the LRP5 (lipoprotein-receptor-related protein) gene. A non-synonymous SNP in the LRP5 gene was associated with decreased bone mineral density (rs3736228, p=6.3x10(-12) for lumbar spine and p=1.9x10(-4) for femoral neck) and an increased risk of both osteoporotic fractures (odds ratio [OR] 1.3, 95% CI 1.09-1.52, p=0.002) and osteoporosis (OR 1.3, 1.08-1.63, p=0.008). Three SNPs near the TNFRSF11B gene were associated with decreased bone mineral density (top SNP, rs4355801: p=7.6x10(-10) for lumbar spine and p=3.3x10(-8) for femoral neck) and increased risk of osteoporosis (OR 1.2, 95% CI 1.01-1.42, p=0.038). For carriers of the risk allele at rs4355801, expression of TNFRSF11B in lymphoblast cell lines was halved (p=3.0x10(-6)). 1883 (22%) of 8557 people were at least heterozygous for these risk alleles, and these alleles had a cumulative association with bone mineral density (trend p=2.3x10(-17)). The presence of both risk alleles increased the risk of osteoporotic fractures (OR 1.3, 1.08-1.63, p=0.006) and this effect was independent of bone mineral density.. Two gene variants of key biological proteins increase the risk of osteoporosis and osteoporotic fracture. The combined effect of these risk alleles on fractures is similar to that of most well-replicated environmental risk factors, and they are present in more than one in five white people, suggesting a potential role in screening.

Topics: Alleles; Bone Density; Chromosomes, Human, Pair 11; Chromosomes, Human, Pair 8; Female; Fractures, Bone; Gene Expression; Genetic Markers; Genome, Human; Genotype; Humans; LDL-Receptor Related Proteins; Low Density Lipoprotein Receptor-Related Protein-5; Lumbar Vertebrae; Male; Middle Aged; Osteoporosis; Osteoprotegerin; Polymorphism, Single Nucleotide

A prospective study was carried out in 22 cirrhotic patients referred for orthotopic liver transplantation, in order to analyze serum osteoprotegerin (OPG) and RANKL levels and their relationship with metabolic bone disease.. Serum levels of OPG and RANKL were measured in all patients as well as bone markers, serum parathyroid hormone and 25-hydroxyvitamin D levels. OPG and RANKL values were compared with those obtained in 29 healthy controls. Bone mineral density (BMD) of the lumbar spine and proximal femur was measured by dual X-ray absorptiometry and spinal X-rays were obtained to assess vertebral fractures.. Serum OPG levels were higher in cirrhotic patients than in controls (6.4+/-2 vs 2.7+/-0.7 pmol/l; P=0.001) and RANKL serum levels were lower in cirrhotic patients (0.215+/-0.6 vs 1.012+/-1.2 pmol/l; P=0.002), with an increased OPG:RANKL ratio when compared with the control group (280.3+/-334.5 vs 113+/-137.6; P=0.04). Ten patients had osteoporosis (45%) and up to 45% skeletal fractures. No differences were found in OPG levels between patients with and without osteoporosis by densitometric criteria or fractures. Negative correlations were found between OPG levels and femoral neck (R-0.46; P=0.03) and total hip BMD (R-0.48; P=0.025). By contrast, OPG values were not related to markers of bone turnover.. OPG values are elevated in cirrhotic patients before liver transplantation, particularly in those with low bone mass at the proximal femur.

Topics: Biomarkers; Bone Density; Bone Diseases, Metabolic; Case-Control Studies; Fractures, Bone; Humans; Liver Cirrhosis; Liver Transplantation; Osteoporosis; Osteoprotegerin; Prospective Studies; RANK Ligand

Topics: Aorta, Abdominal; Aortic Diseases; Bone Density; Calcinosis; Cohort Studies; Female; Fractures, Bone; France; Glycoproteins; Humans; Middle Aged; Osteoporosis; Osteoprotegerin; Prevalence; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Risk Factors

Osteoprotegerin (OPG) is a naturally occurring protein, which prevents bone resorption by inhibition of osteoclastogenesis, function, and survival. Therefore, recombinant OPG may be an attractive drug in the treatment of chronic bone resorptive diseases such as osteoporosis. Gene therapy has the potential to achieve long-term treatment by delivering genes of anti-resorptive proteins to the recipient. The effects of OPG gene therapy on fracture healing have not been described previously. The influence of OPG gene therapy on callus formation, callus tissue structural strength, apparent material properties, and histology of tibia fractures in rats was investigated after 3 weeks and 8 weeks of healing. Intramuscular administration of adeno-associated virus (AAV) vector-mediated OPG resulted in increased levels of OPG in serum of approximately 100 ng/ml throughout the study period. Control animals with fractures received transduction with an AAV reporter gene construct (AAV-enhanced green fluorescent protein (eGFP)), and in this group serum OPG levels remained at baseline (<10 ng/ml). After 3 weeks of healing, AAV-OPG treatment reduced the number of osteoclasts in the callus tissue (33%, P < 0.001). However, AAV-OPG treatment did not influence callus dimensions, callus bone mineral content (BMC), fracture structural strength, or apparent callus tissue material properties. After 8 weeks of healing, AAV-OPG treatment reduced the number of osteoclasts in the callus tissue (31%, P < 0.001) compared with AAV-eGFP fractures. Furthermore, deposition of new woven bone at the fracture line of the original cortical bone was hampered (new woven bone present: in all AAV-eGFP animals, in 41% of AAV-OPG-treated animals, P < 0.001). AAV-OPG treatment also increased callus BMC (18%, P = 0.023) compared with AAV-eGFP fractures. AAV-OPG did not influence callus dimensions, structural strength of the fractures, or ultimate stress, whereas elastic modulus was reduced in the AAV-OPG groups (37%, P = 0.039). The experiment demonstrates that AAV-OPG gene therapy decreases the fracture remodeling, but this does not influence the structural strength of healing fractures.

Topics: Animals; Biomechanical Phenomena; Body Weight; Bone Remodeling; Bony Callus; Female; Fractures, Bone; Genetic Therapy; Glycoproteins; Humans; Osteoprotegerin; Radiography; Rats; Rats, Wistar; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Tibia

The purpose of this study is to investigate the association of serum osteoprotegerin (OPG) and the A163G polymorphism in the OPG promoter with peripheral measures of bone mass and with odds ratios for wrist and hip fracture in a case-control study of postmenopausal Danish women. The study included 66 women with lower forearm fracture, 41 women with hip fracture, and 206 age-matched controls. All had broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured at the heel as well as bone mineral density (BMD) measured by DXA at the distal forearm. S-OPG was measured by ELISA. The A163G genotypes were determined by PCR-RFLP analysis. S-OPG levels correlated positively with age ( r = 0.45; P << 0.0001) and negatively with distal forearm BMD ( r = -0.31; P << 0.0001), heel BUA ( r = -0.23; P << 0.0001), and heel SOS ( r = -0.22; P << 0.0001). Comparing the highest quartile of S-OPG to the lowest, the odds ratio for osteoporotic fracture was 2.5 (95% CI, 1.3-4.7; P = 0.006). The G allele of the A163G was associated with significantly lower t-scores of both lower forearm BMD, heel BUA, and heel SOS as well as being significantly more frequent in the fracture patients compared to the controls. Patients with a combination of the highest quartile of S-OPG and presence of the G allele ( n = 23) had a significantly elevated fracture odds ratio, 4.0 (95% CI, 1.7-9.9). A significant negative association between S-OPG with peripheral measures of bone mass and with increased fracture odds ratios was found. Furthermore, the A163G mutation in the OPG promoter had a significant influence on bone mass and fracture status independently of S-OPG level.

Topics: Bone and Bones; Bone Density; Case-Control Studies; Denmark; Female; Forearm; Fractures, Bone; Glycoproteins; Heel; Humans; Odds Ratio; Osteoprotegerin; Polymorphism, Genetic; Postmenopause; Promoter Regions, Genetic; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Regression Analysis; Ultrasonography

Osteoprotegerin (OPG) and its ligand are cytokines that regulate osteoclastogenesis and that may be involved in the regulation of vascular calcification. We examined whether serum OPG levels were associated with stroke, mortality, and cardiovascular risk factors, including diabetes, as well as with bone mineral density and fractures in a sample of 490 participants in a prospective cohort of white women, at least 65 yr of age. We found that OPG levels, assayed blinded from serum obtained at baseline, were about 30% greater in women with diabetes (mean +/- SD, 0.30 +/- 0.17 ng/mL) than in those without diabetes (0.23 +/- 0.10 ng/mL; P = 0.0001). OPG levels were associated with all-cause mortality [age-adjusted odds ratio, 1.4/SD (0.11 ng/mL) increase in serum OPG level; 95% confidence interval, 1.2--1.8] and cardiovascular mortality (odds ratio, 1.4; 95% confidence interval, 1.1--1.8); these effects were not confounded by diabetes. OPG levels were not associated with baseline bone mineral density or with subsequent strokes or fractures. The association of serum OPG levels with diabetes and with cardiovascular mortality raises the possibility that OPG may be a cause of or a marker for vascular calcification.

Topics: Aged; Biomarkers; Blood Pressure; Bone Density; Cardiovascular Diseases; Cause of Death; Cohort Studies; Confidence Intervals; Diabetes Mellitus; Estrogen Replacement Therapy; Female; Fractures, Bone; Glycoproteins; Humans; Mortality; Observer Variation; Odds Ratio; Osteoprotegerin; Prospective Studies; Receptors, Cytoplasmic and Nuclear; Receptors, Tumor Necrosis Factor; Risk Factors; San Francisco; Smoking; Stroke; White People