Clinical description and genetic analysis of a novel familial skeletal dysplasia characterized by high bone mass and lucent bone lesions.

High bone mass (HBM) disorders are a clinically and genetically heterogeneous subgroup of rare skeletal dysplasias. Here we present a case of a previously unreported familial skeletal dysplasia characterized by HBM and lucent bone lesions that we aimed to clinically characterize and genetically investigate. For phenotyping, we reviewed past clinical records and imaging tests, and performed physical examination (PE), bone densitometry, and mineral panels in affected individuals, including a male proband, his son and daughter, in addition to unaffected controls, including the proband's wife and brother. Affected individuals also underwent impact microindentation (IMI). In an effort to elucidate the disorder's molecular etiology, whole exome sequencing (WES) was performed in all individuals to filter for rare variants present only in affected ones. The cases displayed a unique skeletal phenotype with a mix of sclerotic features and lucent bone lesions, and high IMI values. Bone mineral density was very elevated in the proband and his daughter. The proband's daughter also exhibited idiopathic scoliosis (IS), in addition to mild thrombocytopenia and mild structural thyroid abnormalities, which were the only extra-skeletal abnormalities identified. WES analysis yielded 5 rare putative pathogenic variants in affected members in genes that are associated with bone metabolism including: SEM4AD, TBX18, PTCH1, PTK7, and ADGRE5. The PTK7 variant appeared as possibly implicated in the development of IS while the TBX18 and SEMA4D variants stood out as the strongest candidates for the lucent bone lesions and HBM, respectively, given their high predicted pathogenicity and putative role in bone biology. Variant functionality should be addressed in the future to assess their implication in skeletal metabolism as it is the first time that mutations in TBX18 and SEMA4D have been associated to bone developmental lesions and mineral metabolism in a clinical setting.

A Roadmap to Gene Discoveries and Novel Therapies in Monogenic Low and High Bone Mass Disorders.

Genetic disorders of the skeleton encompass a diverse group of bone diseases differing in clinical characteristics, severity, incidence and molecular etiology. Of particular interest are the monogenic rare bone mass disorders, with the underlying genetic defect contributing to either low or high bone mass phenotype. Extensive, deep phenotyping coupled with high-throughput, cost-effective genotyping is crucial in the characterization and diagnosis of affected individuals. Massive parallel sequencing efforts have been instrumental in the discovery of novel causal genes that merit functional validation using in vitro and ex vivo cell-based techniques, and in vivo models, mainly mice and zebrafish. These translational models also serve as an excellent platform for therapeutic discovery, bridging the gap between basic science research and the clinic. Altogether, genetic studies of monogenic rare bone mass disorders have broadened our knowledge on molecular signaling pathways coordinating bone development and metabolism, disease inheritance patterns, development of new and improved bone biomarkers, and identification of novel drug targets. In this comprehensive review we describe approaches to further enhance the innovative processes taking discoveries from clinic to bench, and then back to clinic in rare bone mass disorders. We highlight the importance of cross laboratory collaboration to perform functional validation in multiple model systems after identification of a novel disease gene. We describe the monogenic forms of rare low and high rare bone mass disorders known to date, provide a roadmap to unravel the genetic determinants of monogenic rare bone mass disorders using proper phenotyping and genotyping methods, and describe different genetic validation approaches paving the way for future treatments.

Functional Analyses of Four CYP1A1 Missense Mutations Present in Patients with Atypical Femoral Fractures.

Osteoporosis is the most common metabolic bone disorder and nitrogen-containing bisphosphonates (BP) are a first line treatment for it. Yet, atypical femoral fractures (AFF), a rare adverse effect, may appear after prolonged BP administration. Given the low incidence of AFF, an underlying genetic cause that increases the susceptibility to these fractures is suspected. Previous studies uncovered rare CYP1A1 mutations in osteoporosis patients who suffered AFF after long-term BP treatment. CYP1A1 is involved in drug metabolism and steroid catabolism, making it an interesting candidate. However, a functional validation for the AFF-associated CYP1A1 mutations was lacking. Here we tested the enzymatic activity of four such CYP1A1 variants, by transfecting them into Saos-2 cells. We also tested the effect of commonly used BPs on the enzymatic activity of the CYP1A1 forms. We demonstrated that the p.Arg98Trp and p.Arg136His CYP1A1 variants have a significant negative effect on enzymatic activity. Moreover, all the BP treatments decreased CYP1A1 activity, although no specific interaction with CYP1A1 variants was found. Our results provide functional support to the hypothesis that an additive effect between CYP1A1 heterozygous mutations p.Arg98Trp and p.Arg136His, other rare mutations and long-term BP exposure might generate susceptibility to AFF.

Thromboembolic, cardiovascular and overall mortality risks of aromatase inhibitors, compared with tamoxifen treatment: an outpatient-register-based retrospective cohort study.

BACKGROUND: Tamoxifen (TAM) and aromatase inhibitor (AI) therapies have been associated with increased risk of thromboembolic and cardiovascular events, respectively, in addition to other side effects. This study analysed the risk of these events and the overall survival (OS) benefit in breast cancer patients treated with AI, compared with TAM-treated patients, in a large population-based cohort. METHODS: This observational cohort study included women diagnosed with breast cancer and treated with TAM or AI. Data were extracted from primary care records in a population database (SIDIAP, System for the Development of Research in Primary Care). Incidence rates of study outcomes are reported. Survival analyses included Kaplan-Meier estimation and Cox proportional hazards models. Sensitivity analysis was carried out, using Fine and Gray models to account for competing risk of death. Confounding was minimized using propensity score adjustment and inverse probability weighting (IPW) adjustment. RESULTS: Data from 3082 postmenopausal women treated with TAM, and 18,455 treated with AI, were available. Adjusted hazard ratios (HRs) [95% confidence interval (CI)] for AI users, compared with TAM group, were 0.93 (95%CI 0.69-1.26) for thromboembolic events (TEEs); 1.13 (95%CI 0.79-1.63) for cardiovascular events, and 0.76 (95%CI 0.70-0.82) for mortality. Additional analyses using competing risk analysis had similar results, while IPW adjustment showed a potential risk of pulmonary embolism (PE) [2.26 (95%CI 1.02-4.97)] in AI-treated patients. CONCLUSIONS: AI users had >20% lower all-cause mortality compared with TAM users, without increasing risk to experience cardiovascular and TEEs. This would locate AI therapy on the first line in clinical practice. Thus, AI might be the most preferable option in adjuvant hormonal therapy choice.

Bone tissue quality in patients with monoclonal gammopathy of uncertain significance.

INTRODUCTION: Monoclonal gammopathy of uncertain significance (MGUS) is highly prevalent in older adults and affects bone structure, with osteoporosis and increased risk of fractures in up to 14% of affected patients. Dual-energy X-ray absorptiometry (DXA), the standard technique for diagnosing osteoporosis, is ineffective to reveal microstructure and bone quality in this disease. MATERIALS AND METHODS: We conducted a cross-sectional study of patients with MGUS, recruited consecutively from the Hematology and Internal Medicine Departments of Hospital del Mar, Barcelona, between January 2011 and January 2018. Medical records, clinical results and spinal X-ray images were collected. Bone mineral density (BMD) at hip and spine was measured by DXA and Bone Material Strength index (BMSi) by impact microindentation on the tibial mid-shaft. RESULTS: Thirty-nine patients with MGUS and 65 age-matched controls without previous fractures were included. In the MGUS group, 11 (28.2%) patients had prevalent fractures, nearly half of them vertebral (n = 5, 45.45%). Compared to controls, MGUS patients had significantly lower BMSi, a mean (SD) of 70.72 (9.70) vs. 78.29 (8.70), p = 0.001, and lower spinal BMD values (0.900 [0.159] vs. 1.003 [0.168], respectively, p = 0.012), but no significant differences at femoral neck and total hip. No association was observed between BMSi and DXA. Bone remodeling markers (procollagen type-1 N propeptide, bone-alkaline phosphatase and C-terminal telopeptide of type I collagen) did not differ between the two groups. CONCLUSIONS: Spinal BMD and mechanical properties of bone tissue, as measured by impact microindentation, were impaired in patients with MGUS. These changes in bone tissue mechanical resistance were independent of DXA levels.

Increased Fracture Risk in Women Treated With Aromatase Inhibitors Versus Tamoxifen: Beneficial Effect of Bisphosphonates.

Aromatase inhibitors have been associated with accelerated bone loss and an increased risk of osteoporotic fractures. Currently, bisphosphonates are recommended to reduce fracture risk in these patients. The aim of this study is to evaluate the fracture risk in breast cancer patients receiving aromatase inhibitors, compared to tamoxifen users, and to assess the effectiveness of oral bisphosphonates in reducing fracture risk. We performed an observational cohort study up to 10 years of follow-up. Data were extracted from primary care records in a population database. Women diagnosed with breast cancer between 2006 and 2015 and treated with tamoxifen or aromatase inhibitors (n = 36,472) were stratified according to low (without osteoporosis diagnosis nor bisphosphonates exposure) or high (with osteoporosis and/or treated with bisphosphonates) fracture risk. Cox models were used to calculate hazard ratios (HR [95% CI]) of fracture from the propensity score-matched patients. Sensitivity analyses account for competing risk of death were performed (subdistribution hazard ratio [SHR] [95% CI]). In postmenopausal women, fracture risk in aromatase inhibitor users showed an HR 1.40 [95% CI,1.05 to 1.87] and SHR 1.48 [95% CI, 1.11 to 1.98], compared to tamoxifen. Observing aromatase inhibitors patients at high risk of fracture, bisphosphonate-treated patients had an HR 0.73 [95% CI, 0.51 to 1.04] and SHR 0.69 [95% CI, 0.48 to 0.98] compared to nontreated. In conclusion, fracture risk in postmenopausal women during aromatase inhibitor treatment, in real-life conditions, was >40% compared to tamoxifen, corroborating previous randomized controlled trials results. In high-risk patients, bisphosphonate users had lower significant fracture incidence during aromatase inhibitor therapy than nonbisphosphonate users. Monitoring fracture risk and related risk factors in aromatase inhibitor patients is advisable. © 2019 American Society for Bone and Mineral Research.

Assessment of early therapy discontinuation and health-related quality of life in breast cancer patients treated with aromatase inhibitors: B-ABLE cohort study.

PURPOSE: The most frequent adverse effects of aromatase inhibitors (AI) are arthralgia and bone loss induction. These reduce the quality of life of patients and their adherence to the treatment. This study evaluates the early AI cessation caused by AI intolerance, and the evolution of joint pain and health-related quality of life (HRQoL) during AI treatment until 1-year after AI completion. METHODS: Data of 910 women diagnosed with early breast cancer and candidates for AI were recruited in B-ABLE cohort. AI discontinuation was analyzed by survival analysis, including Kaplan-Meier estimation and Cox regression. Patients were distributed in three groups of the study according to previous tamoxifen (TAM) exposure and length of AI treatment: TAM-2yAI, TAM-3yAI, and 5yAI. Evolution of joint pain and HRQoL in osteoporosis was evaluated using Visual Analog Scale (VAS) and ECOS-16 tests, respectively, from baseline to 1-year after AI completion through repeated-measures ANOVA. RESULTS: Risk of AI discontinuation was increased in patients previously exposed to tamoxifen compared to non-exposed (adjusted HR 5.30 [95% CI 2.23 to 12.57]). VAS and ECOS-16 scores of TAM-2yAI and TAM-3yAI groups increased during AI treatment, mainly during the first 3-12 months. After 1-year from AI completion, values tend to decrease to baseline levels. In 5yAI group, VAS and ECOS-16 levels increased at three months, and VAS remained significantly higher at 1-year post-treatment. CONCLUSIONS: AI therapy increased joint pain and reduced HRQoL, mainly during the first year of treatment. Patients previously treated with tamoxifen experienced greater pain when they switched to AI therapy and had an excess risk of discontinuation during the first 12 months. TRIAL REGISTRATION: ClinicalTrials.gov: NCT03811509. Registered 28 January 2018-Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03811509 .

Functional characterization of the C7ORF76 genomic region, a prominent GWAS signal for osteoporosis in 7q21.3.

Genome-wide association studies (GWAS) have repeatedly identified genetic variants associated with bone mineral density (BMD) and osteoporotic fracture in non-coding regions of C7ORF76, a poorly studied gene of unknown function. The aim of the present study was to elucidate the causality and molecular mechanisms underlying the association. We re-sequenced the genomic region in two extreme BMD groups from the BARCOS cohort of postmenopausal women to search for functionally relevant variants. Eight selected variants were tested for association in the complete cohort and 2 of them (rs4342521 and rs10085588) were found significantly associated with lumbar spine BMD and nominally associated with osteoporotic fracture. cis-eQTL analyses of these 2 SNPs, together with SNP rs4727338 (GWAS lead SNP in Estrada et al., Nat Genet. 44:491-501, 2012), performed in human primary osteoblasts, disclosed a statistically significant influence on the expression of the proximal neighbouring gene SLC25A13 and a tendency on the distal SHFM1. We then studied the functionality of a putative upstream regulatory element (UPE), containing rs10085588. Luciferase reporter assays showed transactivation capability with a strong allele-dependent effect. Finally, 4C-seq experiments in osteoblastic cell lines showed that the UPE interacted with different tissue-specific enhancers and a lncRNA (LOC100506136) in the region. In summary, this study is the first one to analyse in depth the functionality of C7ORF76 genomic region. We provide functional regulatory evidence for the rs10085588, which may be a causal SNP within the 7q21.3 GWAS signal for osteoporosis.

Vitamin D levels in Mediterranean breast cancer patients compared with those in healthy women.

OBJECTIVES: To evaluate the vitamin D status of postmenopausal women with early estrogen-receptor-positive breast cancer and to compare it with that of healthy postmenopausal women from the same Mediterranean region. STUDY DESIGN AND OUTCOME MEASURES: Data from 691 breast cancer (BC) patients in the B-ABLE cohort were analyzed after recent cancer intervention (recent-BC) or after a minimum of two years since this intervention (long-term-BC). Patients were also stratified by previous chemotherapy exposure (ChT+ and ChT-). Plasma levels of 25-hydroxyvitamin D [25(OH)D] (25(OH)D) were compared with data from 294 healthy women (non-BC) by linear regression to estimate ß-coefficients using non-BC participants as the reference group. Age, body mass index and season of blood extraction were selected as potential confounders. RESULTS: Of the recent-BC patients, 23.7% had 25(OH)D deficiency, compared with 17.7% of the long-term-BC group, and just 1.4% of the non-BC participants. Most of the women were located in the insufficient 25(OH)D category regardless of study group. BC patients had significantly lower 25(OH)D levels than non-BC participants (adjusted ß-coefficients: -4.84 [95%CI -6.56 to -3.12] in recent-BC, and -2.05 [95%CI -4.96 to -0.14] in long-term-BC). Among BC patients, the lowest 25(OH)D levels were found in the recent-BC (ChT+) group (p < 0.001). No differences were found between the long-term-BC (ChT-), long-term-BC (ChT+) and recent-BC (ChT-) groups. Among the BC ChT+ patients, the recent-BC group had significantly lower 25(OH)D levels than the long-term-BC group (p < 0.001). CONCLUSION: Severely reduced 25(OH)D levels were detected in patients with breast cancer, particularly after recent chemotherapy. These 25(OH)D levels had partially recovered over the long term, but still remained much lower than in the healthy population.

Bone health evaluation one year after aromatase inhibitors completion.

INTRODUCTION: Breast cancer patients treated with aromatase inhibitors (AIs) experience increased bone loss during their treatment. However, there is little information about bone mineral density (BMD) after completing AI-treatment. The present study aimed to assess BMD changes one year after AI-therapy completion. METHODS: Data were collected from 864 postmenopausal women treated with AI during 5 years (5y-AI group), or during 2-3 years after taking tamoxifen therapy (pTAM-AI group). Participants with osteoporosis were treated with oral bisphosphonates (BP). BMD changes in lumbar spine (LS), femoral neck (FN) and total hip (TH) between baseline, end of treatment, and at one year post-treatment were assessed using repeated-measures ANOVA. RESULTS: At the end of AI-treatment, 382 patients had available BMD values and 316 also had post-treatment BMD values. As expected, BMD levels were decreased at AI-completion in non-BP treated patients. After one year, LS BMD increased in both groups (5y-AI: +2.11% [95%CI: 1.55 to 2.68], p < 0.001; pTAM-AI: +1.00% [95%CI: 0.49 to 1.51], p < 0.001) compared with the end of AI-therapy, while values at FN and TH remained stable. On the other hand, BMD values of BP-treated patients were increased or maintained at the end of AI-treatment and also at post-treatment. CONCLUSIONS: At one year after AI-completion, FN and TH BMD remained reduced in non-BP treated women, while LS BMD was recovered in the 5y-AI group and partially recovered in the pTAM-AI group. BP treatment increased or maintained BMD values at the end of therapy and at one year post-treatment.

Functional Characterization of a GGPPS Variant Identified in Atypical Femoral Fracture Patients and Delineation of the Role of GGPPS in Bone-Relevant Cell Types.

Atypical femoral fractures (AFFs) are a rare but potentially devastating event, often but not always linked to bisphosphonate (BP) therapy. The pathogenic mechanisms underlying AFFs remain obscure, and there are no tests available that might assist in identifying those at high risk of AFF. We previously used exome sequencing to explore the genetic background of three sisters with AFFs and three additional unrelated AFF cases, all previously treated with BPs. We detected 37 rare mutations (in 34 genes) shared by the three sisters. Notably, we found a p.Asp188Tyr mutation in the enzyme geranylgeranyl pyrophosphate synthase, a component of the mevalonate pathway, which is critical to osteoclast function and is inhibited by N-BPs. In addition, the CYP1A1 gene, responsible for the hydroxylation of 17ß-estradiol, estrone, and vitamin D, was also mutated in all three sisters and one unrelated patient. Here we present a detailed list of the variants found and report functional analyses of the GGPS1 p.Asp188Tyr mutation, which showed a severe reduction in enzyme activity together with oligomerization defects. Unlike BP treatment, this genetic mutation will affect all cells in the carriers. RNAi knockdown of GGPS1 in osteoblasts produced a strong mineralization reduction and a reduced expression of osteocalcin, osterix, and RANKL, whereas in osteoclasts, it led to a lower resorption activity. Taken together, the impact of the mutated GGPPS and the relevance of the downstream effects in bone cells make it a strong candidate for AFF susceptibility. We speculate that other genes such as CYP1A1 might be involved in AFF pathogenesis, which remains to be functionally proved. The identification of the genetic background for AFFs provides new insights for future development of novel risk assessment tools. © 2018 American Society for Bone and Mineral Research.

Common and rare variants of WNT16, DKK1 and SOST and their relationship with bone mineral density.

Numerous GWAS and candidate gene studies have highlighted the role of the Wnt pathway in bone biology. Our objective has been to study in detail the allelic architecture of three Wnt pathway genes: WNT16, DKK1 and SOST, in the context of osteoporosis. We have resequenced the coding and some regulatory regions of these three genes in two groups with extreme bone mineral density (BMD) (n = ∼50, each) from the BARCOS cohort. No interesting novel variants were identified. Thirteen predicted functional variants have been genotyped in the full cohort (n = 1490), and for ten of them (with MAF > 0.01), the association with BMD has been studied. We have found six variants nominally associated with BMD, of which 2 WNT16 variants predicted to be eQTLs for FAM3C (rs55710688, in the Kozak sequence and rs142005327, within a putative enhancer) withstood multiple-testing correction. In addition, two rare variants in functional regions (rs190011371 in WNT16b 3'UTR and rs570754792 in the SOST TATA box) were found only present in three women each, all with BMD below the mean of the cohort. Our results reinforce the higher importance of regulatory versus coding variants in these Wnt pathway genes and open new ways for functional studies of the relevant variants.

AI-related BMD variation in actual practice conditions: A prospective cohort study.

The aim of the study was to evaluate the progression of bone mineral density (BMD) during 3 years of aromatase inhibitors (AI) therapy in actual practice conditions. This prospective, clinical cohort study of Barcelona-Aromatase induced Bone Loss in Early breast cancer (B-ABLE) assessed BMD changes during 3 years of AI treatment in women with breast cancer. Patients with osteoporosis (T score < -2.5 or T score ≤ -2.0) and a major risk factor and/or prevalent fragility fractures were treated with oral bisphosphonates (BPs). Of 685 women recruited, 179 (26.1%) received BP treatment. By the third year of AI therapy, this group exhibited increased BMD in the lumbar spine (LS; 2.59%) and femoral neck (FN; 2.50%), although the increase was significant only within the first year (LS: 1.99% and FN: 2.04%). Despite BP therapy, however, approximately 15% of these patients lost more than 3% of their baseline bone mass. At 3 years, patients without BP experienced BMD decreases in the LS (-3.10%) and FN (-2.79%). In this group, BMD changes occurred during the first (LS: -1.33% and FN: -1.25%), second (LS: -1.19% and FN: -0.82%), and third (LS: -0.57% and FN: -0.65%) years of AI treatment. Increased BMD (>3%) was observed in just 7.6% and 10.8% of these patients at the LS and FN, respectively. Our data confirm a clinically relevant bone loss associated with AI therapy amongst nonusers of preventative BPs. We further report on the importance of BMD monitoring as well as calcium and 25-hydroxy vitamin D supplementation in these patients.

Skeletal adverse effects with aromatase inhibitors in early breast cancer: evidence to date and clinical guidance.

Aromatase inhibitors (AIs) are routinely used in the adjuvant treatment of women with hormone receptor-positive early breast cancer. Patients who receive AIs have an increased risk of bone loss and arthralgia compared with those treated with tamoxifen. In addition to the effects of AIs, the population of women with early breast cancer has a high prevalence of 25-hydroxyvitamin D (25(OH)D) insufficiency. In our experience 88% of patients had concentrations lower than 30 ng/ml. Vitamin D supplementation should be adapted to the baseline concentration. Another relevant finding in our research program was the close relationship between 25(OH)D levels and intensity of AI-related arthralgia (AIrA). A target concentration of 40 ng/ml 25(OH)D may prevent development of AIrA. We also demonstrate that AIrA is genetically determined: single nucleotide polymorphisms located in genes encoding key factors for the metabolism of estrogens and vitamin D (CYP17A1, VDR, and CYP27B1) are associated with self-reported arthralgia during AI therapy. We recommend establishing an individualized protocol of bone-health surveillance based on baseline and evolutionary clinical variables.

Genetic determinants of aromatase inhibitor-related arthralgia: the B-ABLE cohort study.

A major side effect of aromatase inhibitor (AI) therapy is AI-related arthralgia (AIA), which often leads to therapy discontinuation. We aimed to identify genetic variants associated with AIA and therapy discontinuation in the first year of AI treatment. Our prospective cohort study included 343 postmenopausal women with early breast cancer starting AI therapy. Single nucleotide polymorphisms (SNPs) in candidate genes involved in estrogen and vitamin D signaling were selected. Univariate and multivariate linear/logistic regressions were fitted in order to asses the association between studied SNPs and AIA intensity (visual analogic scale score) at 3 and 12 months of follow-up, worsening pain, and therapy discontinuation. We also tested for a priori-defined interactions by introducing multiplicative terms in the regression equations. SNPs in CYP17A1 and VDR genes appeared significantly associated with AIA (P = 0.003, P = 0.012, respectively). One SNP in CYP27B1 gene was related to therapy discontinuation [P = 0.02; OR 0.29 (0.09-0.99)]. We revealed interactions between CYP27B1 and both CYP17A1 (P = 0.01) and VDR SNPs (P = 0.06). Furthermore, an additive effect on pain intensity was shown for unfavorable alleles, with two points higher mean absolute pain increase and up to 5.3-fold higher risk of worsening pain compared to favorable genotypes. SNPs in CYP17A1, VDR, and CYP27B1 genes predict the risk of AIA. Their determination would be useful to trigger the monitoring strategies in women at risk of therapy discontinuation.

Analyses of RANK and RANKL in the post-GWAS context: functional evidence of vitamin D stimulation through a RANKL distal region.

Over the past decade, many genome-wide association studies (GWAs) and meta-analyses have identified genes and regions involved in osteoporotic phenotypes. Nevertheless, the large majority of these results were not tested at any functional level. GWA-associated single-nucleotide polymorphisms (SNPs) near candidate genes such as RANK and RANKL suggest that these SNPs and/or other variants nearby may be involved in bone phenotype determination. This study focuses on SNPs along these two genes, which encode proteins with a well-established role in the bone remodeling equilibrium. Thirty-three SNPs, chosen for their location in evolutionary conserved regions or replicated from previous studies, were genotyped in the BARCOS cohort of 1061 postmenopausal women and tested for association with osteoporotic phenotypes. SNP rs9594738, which lies 184 kb upstream of the RANKL gene, was the only SNP found to be associated with a bone phenotype (dominant model: beta coefficient = -0.034, p = 1.5 × 10(-4) , for lumbar spine bone mineral density). Functional experiments exploring a distal region (DR) of 831 bp that harbors this SNP in a centered position (nt 470) demonstrated its capacity to inhibit the RANKL promoter in reporter gene assays. Remarkably, this DR inhibition was significantly reduced in the presence of vitamin D. In conclusion, the GWA-associated SNP rs9594738 lies in a region involved in transcription regulation through which vitamin D could be regulating RANKL expression and bone mineral density.

Host serum is not indispensable in collagen performance in viable meniscal transplantation at 4-week incubation.

PURPOSE: Viable meniscal transplantation has been criticized as an expensive and logistically demanding technique. The purpose was to compare the standard culture medium with another culture medium that is more widely available and easier to work with and to assess the collagen net ultrastructure architecture and the capacity of the preserved cells to produce proteins. METHODS: Ten fresh lateral menisci were harvested. Each meniscus was divided into three parts; control group, fetal-bovinum-serum group and Insulin-Transferrin-Selenium group during 4 weeks. Cell metabolism was assessed with the gene expression of type I collagen, type II collagen and aggrecan. Collagen ultrastructure was assessed with transmission electron microscopy. The Collagen Meniscal Architecture scoring system was used to evaluate the degree of meniscal disarray. RESULTS: Type I collagen was expressed more in the fetal-bovinum-serum group than in the ITS group (P = 0.036). No differences were found between cultured samples and control groups. Type II collagen showed decreased expression in both cultured groups compared with the control group. No differences were observed in the gene expression of aggrecan in either group. No differences were observed when the Collagen Meniscal Architecture scoring system was applied. CONCLUSIONS: Insulin-Transferrin-Selenium-supplemented medium is at least as effective as the fetal-bovinum-serum-supplemented medium to preserve the net architecture of the meniscal tissue. Gene expression of the studied proteins was similar in the Insulin-Transferrin-Selenium group to that observed in the control group at 4 weeks. Insulin-Transferrin-Selenium might be a better alternative and might be used instead of fetal-bovinum-serum or an autologous host serum in order to preserve meniscal tissue, which precludes the necessity of obtaining host serum previously. Thus, viable meniscal transplantation would logistically be less complicated to perform.

Functional relevance of the BMD-associated polymorphism rs312009: novel involvement of RUNX2 in LRP5 transcriptional regulation.

LRP5 is an osteoporosis susceptibility gene. Association analyses reveal that individual single-nucleotide polymorphisms (SNPs) determine variation in bone mineral density (BMD) among individuals as well as fracture risk. In a previous study, we identified a lumbar spine BMD-associated SNP, rs312009, located in the LRP5 5' region. A RUNX2 binding site was identified in this region by gel-shift experiments. Here we test the functionality of this SNP and examine whether RUNX2 is indeed a regulator of LRP5 expression. Gene reporter assays were used to test rs312009 functionality. Bioinformatic predictive tools and gel-shift and gene reporter assays were used to identify and characterize additional RUNX2 binding elements in the 3.3-kb region upstream of LRP5. Allelic differences in the transcriptional activity of rs312009 were observed in two osteoblastic cell lines, the T allele being a better transcriber than the C allele. RUNX2 cotransfection in HeLa cells revealed that the LRP5 5' region responded to RUNX2 in a dose-dependent manner and that the previously identified RUNX2 binding site participated in this response. Also, RUNX2 inhibition by RNAi led to nearly 60% reduction of endogenous LRP5 mRNA in U-2 OS cells. Four other RUNX2 binding sites were identified in the 5' region of LRP5. Luciferase experiments revealed the involvement of each of them in the RUNX2 response. The allelic differences observed point to the involvement of rs312009 as a functional SNP in the observed association. To our knowledge, this is the first time that the direct action of RUNX2 on LRP5 has been described. This adds evidence to previously described links between two important bone-regulating systems: the RUNX2 transcription-factor cascade and the Wnt signaling pathway.

Effect of IL-1beta, PGE(2), and TGF-beta1 on the expression of OPG and RANKL in normal and osteoporotic primary human osteoblasts.

The RANKL/RANK/OPG pathway is essential for bone remodeling regulation. Many hormones and cytokines are involved in regulating gene expression in most of the pathway components. Moreover, any deregulation of this pathway can alter bone metabolism, resulting in loss or gain of bone mass. Whether osteoblasts from osteoporotic and nonosteoporotic patients respond differently to cytokines is unknown. The aim of this study was to compare the effect of interleukin (IL)-1beta, proftaglandin E(2) (PGE(2)), and transforming growth factor-beta1 (TGF-beta1) treatments on OPG and RANKL gene expression in normal (n = 11) and osteoporotic (n = 8) primary osteoblasts. OPG and RANKL mRNA levels of primary human osteoblastic (hOB) cell cultures were assessed by real-time PCR. In all cultures, OPG mRNA increased significantly in response to IL-1beta treatment and decreased in response to TGF-beta1 whereas PGE(2) treatment had no effect. RANKL mRNA levels were significantly increased by all treatments. Differences in OPG and RANKL responses were observed between osteoporotic and nonosteoporotic hOB: in osteoporotic hOB, the OPG response to IL-1beta treatment was up to three times lower (P = 0.009), whereas that of RANKL response to TGF-beta1 was five times higher (P = 0.002) after 8 h of treatment, as compared with those in nonosteoporotic hOBs. In conclusion, osteoporotic hOB cells showed an anomalous response under cytokine stimulation, consistent with an enhanced osteoclastogenesis resulting in high levels of bone resorption.

Cryopreservation does not alter the ultrastructure of the meniscus.

Fresh frozen menisci have recently been shown to have an altered meniscal ultrastructure. The cause might be a deterioration of its permeability due to collagen net disarray. The purpose of this study was to evaluate the cryopreserved meniscus in terms of ultrastructure and cellularity. Ten fresh human lateral menisci were harvested. Collagen architecture was evaluated with transmission electron microscopy. The Collagen Meniscal Architecture scoring system was used to assess the degree of meniscal disarray. Cell population, was also evaluated. The fibril collagen diameters of those menisci which had been previously cryopreserved showed an average size in the longitudinal section of 12.6 +/- 1.3 nm, whereas it was 13.4 +/- 2.2 nm in the menisci used as controls (n.s.). In the transverse section, the cryopreserved menisci averaged 15.5 +/- 2.4 and 16.7 +/- 3.5 nm in the controls (n.s.). The study group scored 4.8 points +/- 1.7, whereas the control group did so at 4.1 +/- 1.3 (n.s.). The percentage of cell survival after the cryopreservation ranged from 4 to 54. The fibril diameters and degree of disarray showed a similar distribution in both groups. The results suggest that meniscal cryopreservation does not alter the meniscal ultrastructure. Therefore, an allograft stored in that way would not alter its biomechanical properties, although its cellular viability is highly unpredictable.