Large-scale analysis of association between GDF5 and FRZB variants and osteoarthritis of the hip, knee, and hand

Correlation of growth differentiation factor-5 + 104T>C polymorphism with the risk of knee, hand, and hip osteoarthritis: a case-control study and meta-analysis based on 47 case-control studies

Osteoarthritis (OA) arises from a intricate interplay of genetic and environmental factors. Numerous studies have explored the link between the growth differentiation factor 5 (GDF-5) +104T>C polymorphism and OA risk, but the findings have been inconclusive. We carried out a case-control study with 704 OA cases and 418 healthy controls. Furthermore, we conducted a meta-analysis by thoroughly searching the literature for relevant studies published until 1 September, 2023. The combined odds ratio and 95% confidence intervals were used to assess the correlation's strength. A total of 47 independent case-control studies, including 17,602 OA cases and 30,947 controls, were analyzed. Of these, 31 studies (11,176 cases, 16,724 controls) focused on knee OA, 8 studies (3,973 cases, 8,055 controls) examined hip OA, and 6 studies (2244 cases, 5965 controls) investigated hand OA. Overall, our findings suggest that the GDF-5 + 104T>C polymorphism has a protectibe role in development of OA in global scale. Subgroup analyses by ethnicity indicated that this genetic variation provides protection against OA in Caucasian, Asian, and African populations. Further subgroup analysis based on the type of OA showed a decreased risk of knee and hand OA associated with this variation, but not for hip OA. Our combined data indicates that the GDF-5 + 104T>C polymorphism offers protection against the development of OA in general, as well as knee and hand OA. Nevertheless, there was no correlation found between this polymorphism and the development of hip OA.

Phenotypes of osteoarthritis-related knee pain and their transition over time: data from the osteoarthritis initiative

BACKGROUND

Identification of knee osteoarthritis (OA) pain phenotypes, their transition patterns, and risk factors for worse phenotypes, may guide prognosis and targeted treatment; however, few studies have described them. We aimed to investigate different pain phenotypes, their transition patterns, and potential risk factors for worse pain phenotypes.

METHODS

Utilizing data from the Osteoarthritis Initiative (OAI), pain severity was assessed using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale. We identified the activity-related pain phenotypes and estimated the transition probabilities of pain phenotypes from baseline to the 24-month using latent transition analysis. We examined the risk factors at baseline with the 24-month pain phenotypes and the transition of pain phenotypes.

RESULTS

In 4796 participants, we identified four distinct knee pain phenotypes at both baseline and 24-month follow-up: no pain, mild pain during activity (Mild P-A), mild pain during both rest and activity (Mild P-R-A), and moderate pain during both rest and activity (Mod P-R-A). 82.9% knees with no pain at baseline stayed the same at 24-month follow-up, 17.1% progressed to worse pain phenotypes. Among "Mild P-A" at baseline, 32.0% converted to no-pain, 12.8% progressed to "Mild P-R-A", and 53.2% remained. Approximately 46.1% of "Mild P-R-A" and 54.5% of "Mod P-R-A" at baseline experienced remission by 24-month. Female, non-whites, participants with higher depression score, higher body mass index (BMI), higher Kellgren and Lawrence (KL) grade, and knee injury history were more likely to be in the worse pain phenotypes, while participants aged 65 years or older and with higher education were less likely to be in worse pain phenotypes at 24-month follow-up visit. Risk factors for greater transition probability to worse pain phenotypes at 24-month included being female, non-whites, participants with higher depression score, higher BMI, and higher KL grade.

CONCLUSIONS

We identified four distinct knee pain phenotypes. While the pain phenotypes remained stable in the majority of knees over 24 months period, substantial proportion of knees switched to different pain phenotypes. Several socio-demographics as well as radiographic lesions at baseline are associated with worse pain phenotypes at 24-month follow-up visit and transition of pain phenotypes.

Mechanical stress and inflammation have opposite effects on Wnt signaling in human chondrocytes

Dysregulation of Wingless and Int-1 (Wnt) signaling has been strongly associated with development and progression of osteoarthritis (OA). Here, we set out to investigate the independent effects of either mechanical stress (MS) or inflammation on Wnt signaling in human neocartilage pellets, and to relate this Wnt signaling to OA pathophysiology. OA synovium-conditioned media (OAS-CM) was collected after incubating synovium from human end-stage OA joints for 24 h in medium. Cytokine levels in the OAS-CM were determined with a multiplex immunoassay (Luminex). Human neocartilage pellets were exposed to 20% MS, 2% OAS-CM or 1 ng/mL Interleukin-1β (IL-1β). Effects on expression levels of Wnt signaling members were determined by reverse transcription-quantitative polymerase chain reaction. Additionally, the expression of these members in articular cartilage from human OA joints was analyzed in association with joint space narrowing (JSN) and osteophyte scores. Protein levels of IL-1β, IL-6, IL-8, IL-10, tumor necrosis factor α, and granulocyte-macrophage colony-stimulating factor positively correlated with each other. MS increased noncanonical WNT5A and FOS expression. In contrast, these genes were downregulated upon stimulation with OAS-CM or IL-1β. Furthermore, Wnt inhibitors DKK1 and FRZB decreased in response to OAS-CM or IL-1β exposure. Finally, expression of WNT5A in OA articular cartilage was associated with increased JSN scores, but not osteophyte scores. Our results demonstrate that MS and inflammatory stimuli have opposite effects on canonical and noncanonical Wnt signaling in human neocartilage. Considering the extent to which MS and inflammation contribute to OA in individual patients, we hypothesize that targeting specific Wnt pathways offers a more effective, individualized approach.

Serum Metabolome Analysis Identified Amino-Acid Metabolism Associated With Pain in People With Symptomatic Knee Osteoarthritis - A Cross-Sectional Study

Osteoarthritis (OA) is the most common arthritis affecting synovial joints such as knees and hips of millions of people globally. Usage-related joint pain and reduced function are the most common symptoms experienced by people with OA. To improve pain management, there is a need to identify validated biomarkers predicting therapeutic responses in targeted clinical trials. Our study aimed to identify the metabolic biomarkers for pain and pressure pain detection thresholds (PPTs) in participants with knee pain and symptomatic OA using metabolic phenotyping. Metabolite and cytokine measurements were done on serum samples using LC-MS/MS (liquid gas chromatography integrated magnetic resonance mass spectrometry) and Human Proinflammatory panel 1 kit respectively. Regression analysis was done in a test (n = 75) and replication study (n = 79) to investigate the metabolites associated with current knee pain scores and pressure pain detection thresholds (PPTs). Meta-analysis and correlation were done estimating precision of associated metabolites and identifying relationship between significant metabolites and cytokines respectively. Acyl ornithine, carnosine, cortisol, cortisone, cystine, DOPA, glycolithocholic acid sulphate (GLCAS), phenylethylamine (PEA) and succinic acid were found to be significantly (FDR <.1) associated with pain scores in meta-analysis of both studies. IL-10, IL-13, IL-1β, IL2, IL8 and TNF-α were also found to be associated with the significant metabolites. Significant associations of these metabolites and inflammatory markers with knee pain suggests that targeting relevant pathways of amino acid and cholesterol metabolism may modulate cytokines and these could be targeted as novel therapeutics development to improve knee pain and OA management. PERSPECTIVE: Foreseeing the global burden of knee pain in Osteoarthritis (OA) and adverse effects of current pharmacological therapies, this study is envisaged to investigate serum metabolites and molecular pathways involved in knee pain. The replicated metabolites in this study suggests targeting amino-acid pathways for better management of OA knee pain.

Comparative in vitro treatment of mesenchymal stromal cells with GDF-5 and R57A induces chondrogenic differentiation while limiting chondrogenic hypertrophy

PURPOSE

Hypertrophic cartilage is an important characteristic of osteoarthritis and can often be found in patients suffering from osteoarthritis. Although the exact pathomechanism remains poorly understood, hypertrophic de-differentiation of chondrocytes also poses a major challenge in the cell-based repair of hyaline cartilage using mesenchymal stromal cells (MSCs). While different members of the transforming growth factor beta (TGF-β) family have been shown to promote chondrogenesis in MSCs, the transition into a hypertrophic phenotype remains a problem. To further examine this topic we compared the effects of the transcription growth and differentiation factor 5 (GDF-5) and the mutant R57A on in vitro chondrogenesis in MSCs.

METHODS

Bone marrow-derived MSCs (BMSCs) were placed in pellet culture and in-cubated in chondrogenic differentiation medium containing R57A, GDF-5 and TGF-ß1 for 21 days. Chondrogenesis was examined histologically, immunohistochemically, through biochemical assays and by RT-qPCR regarding the expression of chondrogenic marker genes.

RESULTS

Treatment of BMSCs with R57A led to a dose dependent induction of chondrogenesis in BMSCs. Biochemical assays also showed an elevated glycosaminoglycan (GAG) content and expression of chondrogenic marker genes in corresponding pellets. While treatment with R57A led to superior chondrogenic differentiation compared to treatment with the GDF-5 wild type and similar levels compared to incubation with TGF-ß1, levels of chondrogenic hypertrophy were lower after induction with R57A and the GDF-5 wild type.

CONCLUSIONS

R57A is a stronger inducer of chondrogenesis in BMSCs than the GDF-5 wild type while leading to lower levels of chondrogenic hypertrophy in comparison with TGF-ß1.

Dual functions of microRNA-17 in maintaining cartilage homeostasis and protection against osteoarthritis

Damaged hyaline cartilage has no capacity for self-healing, making osteoarthritis (OA) "difficult-to-treat". Cartilage destruction is central to OA patho-etiology and is mediated by matrix degrading enzymes. Here we report decreased expression of miR-17 in osteoarthritic chondrocytes and its deficiency contributes to OA progression. Supplementation of exogenous miR-17 or its endogenous induction by growth differentiation factor 5, effectively prevented OA by simultaneously targeting pathological catabolic factors including matrix metallopeptidase-3/13 (MMP3/13), aggrecanase-2 (ADAMTS5), and nitric oxide synthase-2 (NOS2). Single-cell RNA sequencing of hyaline cartilage revealed two distinct superficial chondrocyte populations (C1/C2). C1 expressed physiological catabolic factors including MMP2, and C2 carries synovial features, together with C3 in the middle zone. MiR-17 is highly expressed in both superficial and middle chondrocytes under physiological conditions, and maintains the physiological catabolic and anabolic balance potentially by restricting HIF-1α signaling. Together, this study identified dual functions of miR-17 in maintaining cartilage homeostasis and prevention of OA.

Age-dependent changes in protein incorporation into collagen-rich tissues of mice by in vivo pulsed SILAC labelling

Collagen-rich tissues have poor reparative capacity that predisposes to common age-related disorders such as osteoporosis and osteoarthritis. We used in vivo pulsed SILAC labelling to quantify new protein incorporation into cartilage, bone, and skin of mice across the healthy life course. We report dynamic turnover of the matrisome, the proteins of the extracellular matrix, in bone and cartilage during skeletal maturation, which was markedly reduced after skeletal maturity. Comparing young adult with older adult mice, new protein incorporation was reduced in all tissues. STRING clustering revealed changes in epigenetic modulators across all tissues, a decline in chondroprotective growth factors such as FGF2 and TGFβ in cartilage, and clusters indicating mitochondrial dysregulation and reduced collagen synthesis in bone. Several pathways were implicated in age-related disease. Fewer changes were observed for skin. This methodology provides dynamic protein data at a tissue level, uncovering age-related molecular changes that may predispose to disease.

Frequency of Growth Differentiation Factor 5 rs143383 and asporin D-repeat polymorphisms in patients with hand and knee osteoarthritis in Kurdistan province, Iran

AIM

Osteoarthritis (OA) is the most common chronic joint disorder, resulting from the breakdown of joint cartilage. It occurs in the knees, hands, and hips, leading to pain, stiffness, inflammation, and swelling.

METHODS

In this study, 100 hand and knee OA patients, meeting the American College of Rheumatology criteria were included in the case group, and 100 healthy individuals were allocated to the control group. Blood samples were collected from the participants. After DNA extraction, genotyping was carried out for GDF5 rs143383 C/T polymorphism by allele-specific polymerase chain reaction (ASPCR) and for D-repeat alleles of asporin (ASPN) by conventional PCR assay.

RESULTS

The results showed that the frequency of the D14 allele of ASPN was significantly higher than other alleles in the case group (P = .0001). Also, the frequency of the D14 allele among women was significantly higher than in men (P = .004). Moreover, the frequency of the TT allele in GDF5 rs143383 C/T polymorphism was significantly higher than the CC and CT alleles in the case group, compared with the control group (P = .001). A significant difference was found between the TT allele and other alleles in female and male patients compared with the control group (P = .02).

CONCLUSIONS

The D14 allele of the ASPN gene and TT allele of the GDF5 gene (rs143383 + 104T/C) are associated with hand and knee OA in the Kurdish population, indicating that these alleles could be risk factors for OA, at least in our populations.

Secreted frizzled-related protein 3 was genetically and functionally associated with developmental dysplasia of the hip

Background: Developmental dysplasia of the hip (DDH) is the most common joint disease in child orthopedics. Secreted Frizzled-Related Protein 3 (FRZB) plays an important role in joint development. however, no direct association between FRZB and DDH has been demonstrated.

Methods: Analysis of genotype distribution and allele frequency for detected single nucleotide polymorphisms (SNP) of FRZB was performed. FRZB expression was assayed in DDH joint tissues. Further experiments to identify the chondrogenic properties of FRZB were conducted. Potential upstream miRNAs for FRZB were assayed in DDH.

Results: Significant difference in genotype distribution for rs3768842 (OR=1.46, P=0.0081) and rs2242040 (OR=0.65, P=0.0067) was found. DDH joint tissues showed significantly higher FRZB expression. FRZB demonstrated chondrogenic and anti-hypertrophic properties in vitro. FRZB modulated cell adhesion pathway and cell spreading by regulating integrins expressions. Upstream miRNAs regulating FRZB expression were identified in DDH synovial fluid. Experiments indicated that downregulated miRNA-454 caused FRZB upregulation in DDH joint.

Conclusion: Dysregulated FRZB and its loci were associated with DDH. As a Wnt antagonist with chondrogenic properties, FRZB modulated cell adhesion pathway and cell spreading by regulating integrins expressions. FRZB in multiple DDH joint tissues might be mediated by the dysregulated miRNA expression profiles in the joint synovial fluid.

The Decisive Case-Control Study Elaborates the Null Association between ESR1 XbaI and Osteoarthritis in Asians: A Case-Control Study and Meta-Analysis

(1) Background: The prevalence of knee osteoarthritis (OA) in women is significantly higher than in men. The estrogen receptor α (ERα) has been considered to play a key role due to a large gender difference in its expression. ERα is encoded by the gene estrogen receptor 1 (ESR1), which is widely studied to explore the gender difference in knee OA. Several polymorphisms in ESR1 [PvuII (rs2234693) and BtgI (rs2228480)] were confirmed as the risk factors of OA. However, the evidence of the last widely investigated polymorphism, ESR1 Xbal (rs9340799), is still insufficient for concluding its effect on knee OA. (2) Objective: This study proposed a case-control study to investigate the association between ESR1 Xbal and knee OA. Moreover, a meta-analysis and trial sequential analysis (TSA) were conducted to enlarge the sample size for obtaining a conclusive evidence. (3) Methods: In total, 497 knee OA cases and 473 healthy controls were recruited between March 2015 and July 2018. The Kellgren-Lawrence grading system was used to identify the knee OA cases. To improve the evidence level of our study, we conducted a meta-analysis including the related studies published up until December 2018 from PubMed, Embase, and previous meta-analysis. The results are expressed as odds ratios (ORs) with corresponding 95% confidence intervals (CI) for evaluating the effect of this polymorphism on knee OA risk. TSA was used to estimate the sample sizes required in this issue. (4) Results: We found non-significant association between the G allele and knee OA [Crude-OR: 0.97 (95% CI: 0.78-1.20) and adjusted-OR: 0.90 (95% CI: 0.71-1.15) in allele model] in the present case-control study, and the analysis of other genetic models showed a similar trend. After including six published studies and our case-control studies, the current evidence with 3174 Asians showed the conclusively null association between ESR1 XbaI and knee OA [OR: 0.78 (95% CI: 0.59-1.04)] with a high heterogeneity (I²: 78%). The result of Caucasians also concluded the null association [OR: 1.05 (95% CI: 0.56-1.95), I²: 87%]. (5) Conclusions: The association between ESR1 XbaI and knee OA was not similar with other polymorphisms in ESR1, which is not a causal relationship. This study integrated all current evidence to elaborate this conclusion for suggesting no necessity of future studies.

Growth differentiation factor 5 in cartilage and osteoarthritis: A possible therapeutic candidate

Growth differentiation factor 5 (GDF-5) is essential for cartilage development and homeostasis. The expression and function of GDF-5 are highly associated with the pathogenesis of osteoarthritis (OA). OA, characterized by progressive degeneration of joint, particularly in cartilage, causes severe social burden. However, there is no effective approach to reverse the progression of this disease. Over the past decades, extensive studies have demonstrated the protective effects of GDF-5 against cartilage degeneration and defects. Here, we summarize the current literature describing the role of GDF-5 in development of cartilage and joints, and the association between the GDF-5 gene polymorphisms and OA susceptibility. We also shed light on the protective effects of GDF-5 against OA in terms of direct GDF-5 supplementation and modulation of the GDF-5-related signalling. Finally, we discuss the current limitations in the application of GDF-5 for the clinical treatment of OA. This review provides a comprehensive insight into the role of GDF-5 in cartilage and emphasizes GDF-5 as a potential therapeutic candidate in OA.

Constitutional morphological features and risk of hip osteoarthritis: a case-control study using standard radiographs

OBJECTIVES

To evaluate the risk of association with hip osteoarthritis (OA) of 14 morphological features measured on standard antero-posterior pelvis radiographs.

METHODS

A case-control study of 566 symptomatic unilateral hip OA cases and 1108 controls without hip OA, using the Genetics of OA and Lifestyle database. Unaffected hips of cases were assumed to reflect pre-OA morphology of the contralateral affected hip. ORs with 95% CI adjusted for confounding factors were calculated using logistic regression. Hierarchical clustering on principal component method was used to identify clusters of morphological features. Proportional risk contribution (PRC) of these morphological features in the context of other risk factors of hip OA was estimated using receiver operating characteristic analysis.

RESULTS

All morphological features showed right-left symmetry in controls. Each feature was associated with hip OA after adjusting for age, gender and body mass index. Increased sourcil angle had the strongest association (OR: 6.93, 95% CI 5.16 to 9.32). Three clusters were identified. The PRC varied between individual features, as well as between clusters. It was 35% (95% CI 31% to 40%) for all 14 morphological features, compared to 21% (95% CI 19% to 24%) for all other well-established risk factors.

CONCLUSIONS

Constitutional morphological variation strongly associates with hip OA development and may explain much of its heritability. Relevant morphological measures can be assessed readily on standard radiographs to help predict risk of hip OA. Prospective studies are required to provide further support for causality.

Genetics in Cartilage Lesions: Basic Science and Therapy Approaches

Cartilage lesions have a multifactorial nature, and genetic factors are their strongest determinants. As biochemical and genetic studies have dramatically progressed over the past decade, the molecular basis of cartilage pathologies has become clearer. Several homeostasis abnormalities within cartilaginous tissue have been found, including various structural changes, differential gene expression patterns, as well as altered epigenetic regulation. However, the efficient treatment of cartilage pathologies represents a substantial challenge. Understanding the complex genetic background pertaining to cartilage pathologies is useful primarily in the context of seeking new pathways leading to disease progression as well as in developing new targeted therapies. A technology utilizing gene transfer to deliver therapeutic genes to the site of injury is quickly becoming an emerging approach in cartilage renewal. The goal of this work is to provide an overview of the genetic basis of chondral lesions and the different approaches of the most recent systems exploiting therapeutic gene transfer in cartilage repair. The integration of tissue engineering with viral gene vectors is a novel and active area of research. However, despite promising preclinical data, this therapeutic concept needs to be supported by the growing body of clinical trials.

Analysis of genetically independent phenotypes identifies shared genetic factors associated with chronic musculoskeletal pain conditions

Chronic musculoskeletal pain affects all aspects of human life. However, mechanisms of its genetic control remain poorly understood. Genetic studies of pain are complicated by the high complexity and heterogeneity of pain phenotypes. Here, we apply principal component analysis to reduce phenotype heterogeneity of chronic musculoskeletal pain at four locations: the back, neck/shoulder, hip, and knee. Using matrices of genetic covariances, we constructed four genetically independent phenotypes (GIPs) with the leading GIP (GIP1) explaining 78.4% of the genetic variance of the analyzed conditions, and GIP2–4 explain progressively less. We identified and replicated five GIP1-associated loci and one GIP2-associated locus and prioritized the most likely causal genes. For GIP1, we showed enrichment with multiple nervous system-related terms and genetic correlations with anthropometric, sociodemographic, psychiatric/personality traits and osteoarthritis. We suggest that GIP1 represents a biopsychological component of chronic musculoskeletal pain, related to physiological and psychological aspects and reflecting pain perception and processing.

Yakov Tsepilov, Maxim Freidin et al. find that chronic musculoskeletal pain conditions at four distinct anatomical sites share a common genetic background. The authors constructed genetically independent phenotypes (GIP) from principal components analysis of the different pain phenotypes and used the GIPs to perform genome-wide association studies to identify underlying genetic factors.

Genetics of developmental dysplasia of the hip

In the last decade, the advances in the molecular analyses and sequencing techniques allowed researchers to study developmental dysplasia of the hip (DDH) more thoroughly. Certain chromosomes, genes, loci and polymorphisms are being associated with variable severity of this disorder. The wide range of signs and symptoms is dependent either on isolated or systemic manifestation. Phenotypes of isolated cases range from only a mild ligamental laxity, through subluxation, to a complete dislocation of the femoral head. Systemic manifestation is connected to various forms of skeletal dysplasia and other malformations characterized by significant genetic aberrations. To reveal the background of DDH heredity, multiple studies focused on large sample sizes with an emphasis on the correlation between genotype, phenotype and continuous clinical examination. Etiological risk factors that have been observed and documented in patients include genetic, environmental, and mechanical factors, which significantly contribute to the familial or nonfamilial occurrence and phenotypic variability of this disorder. Still, the multifactorial etiology and pathogenesis of DDH are not yet sufficiently clarified, explained, or understood. Formation of connective tissue, osteogenesis, chondrogenesis, and all other affected pathways and variations in the function of their individual elements contribute to the creation of the pathology in a developing human body. This review article presents an up-to-date list of known DDH associated genes, their products, and functional characteristics.

Developmental Dysplasia of the Hip: A Review of Etiopathogenesis, Risk Factors, and Genetic Aspects

As one of the most frequent skeletal anomalies, developmental dysplasia of the hip (DDH) is characterized by a considerable range of pathology, from minor laxity of ligaments in the hip joint to complete luxation. Multifactorial etiology, of which the candidate genes have been studied the most, poses a challenge in understanding this disorder. Candidate gene association studies (CGASs) along with genome-wide association studies (GWASs) and genome-wide linkage analyses (GWLAs) have found numerous genes and loci with susceptible DDH association. Studies put major importance on candidate genes associated with the formation of connective tissue (COL1A1), osteogenesis (PAPPA2, GDF5), chondrogenesis (UQCC1, ASPN) and cell growth, proliferation and differentiation (TGFB1). Recent studies show that epigenetic factors, such as DNA methylation affect gene expression and therefore could play an important role in DDH pathogenesis. This paper reviews all existing risk factors affecting DDH incidence, along with candidate genes associated with genetic or epigenetic etiology of DDH in various studies.

Generation and characterization of human induced pluripotent stem cells (iPSCs) from hand osteoarthritis patient-derived fibroblasts

Knowledge and research results about hand osteoarthritis (hOA) are limited due to the lack of samples and animal models of the disease. Here, we report the generation of two induced pluripotent stem cell (iPSC)-lines from patients with radiographic hOA. Furthermore, we wondered whether these iPSC-lines carried single nucleotide polymorphisms (SNPs) within genes that have been associated with hOA. Finally, we performed chondrogenic differentiation of the iPSCs in order to prove their usefulness as cellular models of the disease. We performed a non-integrative reprogramming of dermal fibroblasts obtained from two patients with radiographic rhizarthrosis and non-erosive hOA by introducing the transcriptional factors Oct4, Sox2, Klf4 and c-Myc using Sendai virus. After reprogramming, embryonic stem cell-like colonies emerged in culture, which fulfilled all the criteria to be considered iPSCs. Both iPSC-lines carried variants associated with hOA in the four studied genes and showed differences in their chondrogenic capacity when compared with a healthy control iPSC-line. To our knowledge this is the first time that the generation of iPSC-lines from patients with rhizarthrosis and non-erosive hOA is reported. The obtained iPSC-lines might enable us to model the disease in vitro, and to deeper study both the molecular and cellular mechanisms underlying hOA.

INHIBITION OF WINGLESS-RELATED INTEGRATION SITE (WNT) SIGNALLING MAY TREAT OSTEOARTHRITIS OF THE KNEE

Osteoarthritis (OA) of the knee is the leading cause of disability in individuals over 60 years of age. Currently, treatments have been limited to analgesic and anti-inflammatory medications that reduce pain and improve function for short periods of time, until a joint replacement is required. Recently, inhibition of the Wnt/beta-catenin signaling pathway with lorecivivint (LOR; SMO496) was found to prevent the deterioration of the cartilage in preclinical models of posttraumatic OA. LOR appears to reduce both STAT signaling and Wnt signaling in the chondrocyte, allowing for both a reduction in pain and the production of enzymes associated with cartilage destruction. LOR has been tested in both Phase I and Phase 2 trials, and a dose of 0.07ug/kg administered through intra-articular injection reduced pain and preserved the articular joint space as assessed by radiograph. Therefore, reduction in Wnt signaling in the knee joint may reduce signs and symptoms and alter the course of osteoarthritis.

Defective WNT signaling may protect from articular cartilage deterioration - a quantitative MRI study on subjects with a heterozygous WNT1 mutation

OBJECTIVE

WNT signaling is of key importance in chondrogenesis and defective WNT signaling may contribute to the pathogenesis of osteoarthritis and other cartilage diseases. Biochemical composition of articular cartilage in patients with aberrant WNT signaling has not been studied. Our objective was to assess the knee articular cartilage in WNT1 mutation-positive individuals using a 3.0T MRI unit to measure cartilage thickness, relaxation times, and texture features.

DESIGN

Cohort comprised mutation-positive (N = 13; age 17-76 years) and mutation-negative (N = 13; 16-77 years) subjects from two Finnish families with autosomal dominant WNT1 osteoporosis due to a heterozygous missense mutation c.652T>G (p.C218G) in WNT1. All subjects were imaged with a 3.0T MRI unit and assessed for cartilage thickness, T2 and T1ρ relaxation times, and T2 texture features contrast, dissimilarity and homogeneity of T2 relaxation time maps in six regions of interest (ROIs) in the tibiofemoral cartilage.

RESULTS

All three texture features showed opposing trends with age between the groups in the medial tibiofemoral cartilage (P = 0.020-0.085 for the difference of the regression coefficients), the mutation-positive individuals showing signs of cartilage preservation. No significant differences were observed in the lateral tibiofemoral cartilage. Cartilage thickness and means of T2 relaxation time did not differ between groups. Means of T1ρ relaxation time were significantly different in one ROI but the regression analysis displayed no differences.

CONCLUSIONS

Our results show less age-related cartilage deterioration in the WNT1 mutation-positive than the mutation-negative subjects. This suggests, that the WNT1 mutation may alter cartilage turnover and even have a potential cartilage-preserving effect.

Association of IL-17A-197G/A and IL-17F-7488T/C polymorphisms and osteoarthritis susceptibility: A meta-analysis

AIM

This meta-analysis was conducted with the aim of collecting and synthesizing the existing evidence on the association of interleukin-17A (IL-17A)-197G/A and IL-17F-7488T/C gene polymorphisms and osteoarthritis (OA) susceptibility.

METHODS

Six electronic databases including PubMed, EMBASE, Web of Science, Cochrane Library, CNKI, and Wanfang were systematically searched for potentially relevant studies previous to June 2019. The strengths of association were estimated by summary odds ratios (ORs) and 95% confidence intervals (95%CIs) in a model-free approach. Heterogeneity test and sensitivity analysis were also conducted to guarantee the reliability of this study.

RESULTS

Six eligible case-control studies comprising 1989 OA patients and 2116 healthy controls were obtained for the meta-analysis. Dominant model was confirmed to be the optimal genetic model (MM + Mm vs mm). The pooled estimate supported that IL-17A-197G/A and IL-17F-7488T/C polymorphisms were significantly associated with OA susceptibility in the overall population (IL-17A-197G/A: GG + GA vs AA, OR = 0.69, 95%CI 0.57-0.80; P < .001; IL-17F-7488T/C, TT + TC vs CC, OR = 0.46, 95%CI 0.29-0.71, P < .001). However, subgroup analyses suggested the association only existed in Asians and knee OA.

CONCLUSION

The findings of the present study indicate that IL-17A-197G/A and IL-17F-7488T/C polymorphisms are positively associated to reduced risk of knee OA, especially in Asian populations.

Genome Engineering for Osteoarthritis: From Designer Cells to Disease-Modifying Drugs

BACKGROUND

Osteoarthritis (OA) is a highly prevalent degenerative joint disease involving joint cartilage and its surrounding tissues. OA is the leading cause of pain and disability worldwide. At present, there are no disease-modifying OA drugs, and the primary therapies include exercise and nonsteroidal anti-inflammatory drugs until total joint replacement at the end-stage of the disease.

METHODS

In this review, we summarized the current state of knowledge in genetic and epigenetic associations and risk factors for OA and their potential diagnostic and therapeutic applications.

RESULTS

Genome-wide association studies and analysis of epigenetic modifications (such as miRNA expression, DNA methylation and histone modifications) conducted across various populations support the notion that there is a genetic basis for certain subsets of OA pathogenesis.

CONCLUSION

With recent advances in the development of genome editing technologies such as the CRISPR-Cas9 system, these genetic and epigenetic alternations in OA can be used as platforms from which potential biomarkers for the diagnosis, prognosis, drug response, and development of potential personalized therapeutic targets for OA can be approached. Furthermore, genome editing has allowed the development of "designer" cells, whereby the receptors, gene regulatory networks, or transgenes can be modified as a basis for new cell-based therapies.

Association between ACE gene I/D polymorphism and knee osteoarthritis in a Chinese population

Osteoarthritis (OA) is a degenerative joint disease characterized by joint destruction with cartilage loss and occasional gross derangement of joint integrity. In recent years, several studies have reported the association between angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and knee OA. However, the results were conflicting. To determine the association between ACE gene I/D polymorphism and knee OA, we conducted a hospital-based case–control study with 282 knee OA cases and 316 controls to investigate the association between ACE gene I/D polymorphism and knee OA susceptibility in a Chinese Han population. The present study found that DD genotype or D allele carriers of ACE gene I/D polymorphism increased the risk of knee OA. Stratification analyses of sex, age, and body mass index (BMI) showed significant associations amongst the groups of females, ≥55 years, and abnormal BMI. In addition, the present study made analysis between ACE I/D polymorphism and some clinical features of OA, and found DD genotype of I/D polymorphism was associated with arthralgia. Furthermore, we undertook a meta-analysis together with the present study between this single nucleotide polymorphism (SNP) and knee OA risk. This meta-analysis found that ACE gene I/D polymorphism was associated with increased risk for OA. Stratification analysis of ethnicity in this meta-analysis indicated that I/D polymorphism increased the risk of knee OA amongst the Asians and Caucasians. In conclusion, this case–control study and meta-analysis suggest that ACE gene I/D polymorphism is associated with increased risk for knee OA.

A genome-wide association study identifies new genes associated with developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is one of the most common congenital malformations and covers a spectrum of hip disorders from mild dysplasia to irreducible dislocation. The pathological mechanisms of DDH are poorly understood, which hampers the development of diagnostic tools and treatments. To gain insight into its disease mechanism, we explored the potential biological processes that underlie DDH by integrating pathway analysis tools and performing a genome-wide association study (GWAS). A total of 406 DDH-associated genes (P < 0.001) were identified by our GWAS using a Chinese Han cohort consisting of 386 DDH cases and 500 healthy controls (Set A). We verified the significant loci (P < 10^-5 ) in another Chinese Han cohort consisting of 574 DDH patients and 569 healthy controls (Set B). An intronic Single Nucleotide Polymorphism (SNP) (rs61930502) showed significant association in Set A and Set B (P = 2.65 × 10^-7 and 2.0 × 10^-4 , respectively). The minor allele, rs61930502-A, which tended to prevent DDH showed a dominant effect. Heat shock 70 kDa protein 8 (HSPA8) showed the most direct interactions with other proteins which were coded by DDH-associated genes in the protein-protein interaction analysis. Interestingly, Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested a relation between DDH and the genes involved in type II diabetes mellitus pathway (P = 0.0067). Our genetic and protein interaction evidence could open avenues for future studies of DDH.

Lin28a overexpression reveals the role of Erk signaling in articular cartilage development

Adult articular cartilage shows limited tissue turnover, and therefore development of the proper structure of articular cartilage is crucial for life-long joint function. However, the mechanism by which the articular cartilage structure is developmentally regulated is poorly understood. In this study, we show evidence that activation of extracellular signal-regulated kinases (Erk1/2) in articular chondrocyte progenitors during developmental stages control articular cartilage thickness. We found that overexpression of Lin28a, an RNA-binding protein that regulates organismal growth and metabolism, in articular chondrocyte progenitor cells upregulated Erk signaling and increased articular cartilage thickness. Overexpression of a constitutively active Kras mimicked Lin28a overexpression, and inhibition of Erk signaling during embryonic stages normalized the cartilage phenotype of both Kras- and Lin28a-overexpressing mice. These results suggest that articular cartilage thickness is mainly determined during the process of embryonic synovial joint development, which is positively regulated by Erk signaling.

The Involvement of MicroRNAs in Osteoarthritis and Recent Developments: A Narrative Review

Background:

Osteoarthritis (OA) is the most common chronic joint disease and it may progressively cause disability and compromise quality of life. Lately, the role of miRNAs in the pathogenesis of OA has drawn a lot of attention. miRNAs are small, single-stranded, non-coding molecules of RNA which regulate gene expression at post-transcriptional level. The dysregulation of the expression of several miRNAs affects pathways involved in OA pathogenesis.

Objective:

The purpose of this article is to review the literature on the involvement of miRNAs in the pathogenesis of OA and the implications on its diagnosis and treatment.

Materials and Methods:

An extensive electronic literature search was conducted by two researchers from January 2008 to August 2017. Titles and abstracts of papers were screened by the authors for further inclusion in the present work. Finally, full texts of the selected articles were retrieved.

Results:

Abnormally expressed miRNAs enhance the production of cartilage degrading enzymes, inhibit the expression of cartilage matrix components, increase the production of proinflammatory cytokines, facilitate chondrocyte apoptosis, suppress autophagy in chondrocytes and are involved in pain-related pathways. miRNAs are also incorporated in extra-cellular membranous vesicles such as exosomes and participate in the intercellular communication in osteoarthritic joints.

Conclusion:

Ongoing research on miRNAs has potential implications in the diagnosis and treatment of OA. Their different levels in peripheral blood and synovial fluid between OA patients and healthy population makes them candidates for being used as biomarkers of the disease, while targeting miRNAs may be a novel therapeutic strategy in OA.

FRZB1 rs2242070 polymorphisms is associated with brick tea type skeletal fluorosis in Kazakhs, but not in Tibetans, China

Skeletal fluorosis is a metabolic bone and joint disease caused by excessive accumulation of fluoride in the bones. Compared with Kazakhs, Tibetans are more likely to develop moderate and severe brick tea type skeletal fluorosis, although they have similar fluoride exposure. Single nucleotide polymorphisms (SNPs) in frizzled-related protein (FRZB) have been associated with osteoarthritis, but their association with the risk of skeletal fluorosis has not been reported. In this paper, we investigated the association of three SNPs (rs7775, rs2242070 and rs9288087) in FRZB1with brick tea type skeletal fluorosis risk in a cross-sectional case-control study conducted in Sinkiang and Qinghai, China. A total of 598 individuals, including 308 Tibetans and 290 Kazakhs, were enrolled in this study, in which cases and controls were 221 and 377, respectively. The skeletal fluorosis was diagnosed according to the Chinese diagnostic criteria of endemic skeletal fluorosis (WS192-2008). The fluoride content in tea water or urine was detected using the fluoride ion electrode. SNPs were assessed using the Sequenom MassARRAY system. Binary logistic regressions found evidence of association with rs2242070 AA genotype in only Kazakh participants [odds ratio (OR) 0.417, 95% CI 0.216-0.807, p = 0.009], but not in Tibetans. When stratified by age, this protective effect of AA genotype in rs2242070 was pronounced in Kazakh participants aged 46-65 (OR 0.321, 95% CI 0.135-0.764, p = 0.010). This protective association with AA genotype in rs2242070 in Kazakhs also appeared to be stronger with tea fluoride intake > 3.5 mg/day (OR 0.396, 95% CI 0.182-0.864, p = 0.020). Our data suggest there might be differential genetic influence on skeletal fluorosis risk in Kazakh and Tibetan participants and that this difference might be modified by tea fluoride intake.

Association between EN1 rs4144782 and susceptibility of knee osteoarthritis: A case-control study

Osteoarthritis (OA) is a complex disease that affects the whole joint, resulting from the combined influence of biomechanical factors and genetic factors. The heritable component for primary OA accounts for about 60% of variation in population liability to the disease. So far, genome-wide association studies (GWAS) and candidate gene studies have established many OA-related loci. However, these findings account for only a rather small fraction of the genetic component. To further reveal the genetic architecture of OA, we conducted this case-control study to explore the association of locus EN1 rs4144782 and knee OA susceptibility in a Chinese population. EN1 rs4144782 was significantly associated with increased risk of knee OA (OR=1.26; 95% CI: 1.05-1.50, P value=0.012). In dominant model, compared with carriers of GG genotype, those with AG or AA genotype have an 1.44-fold increased risk of OA (OR: 1.44; 95% CI: 1.10-1.88; P value=0.008). Subgroup analyses didn't change the results materially. This should be the first association study of EN1 locus on risk of OA, and our finding suggested that the EN1 rs4144782 might contribute to the susceptibility of knee OA.

Can Genetics Predict Sports Injury? The Association of the Genes GDF5, AMPD1, COL5A1 and IGF2 on Soccer Player Injury Occurrence

Genetics plays an integral role in athletic performance and is increasingly becoming recognised as an important risk factor for injury. Ankle and knee injuries are the most common injuries sustained by soccer players. Often these injuries result in players missing training and matches, which can incur significant costs to clubs. This study aimed to identify genotypes associated with ankle and knee injuries in soccer players and how these impacted the number of matches played. 289 soccer players, including 46 professional, 98 semi-professional and 145 amateur players, were genetically tested. Ankle and knee injuries and the number of matches played were recorded during the 2014/15 season. Four genes were assessed in relation to injury. Genotypes found to be associated with injury included the TT (nucleobase) genotype of the GDF5 gene, TT and CT (nucleobase) genotypes of AMPD1 gene, TT genotype of COL5A1 and GG (nucleobase) genotype of IGF2 gene. These genes were also associated with a decrease in the number of matches played.

Candidate gene investigation of spinal degenerative osteoarthritis in Greek population

BACKGROUND CONTEXT

Few data exist concerning the natural history of degenerative osteoarthritis (OA) of the spine and its associated gene investigation. Degenerative spinal OA demonstrates an international prevalence of 15% in the general population.

PURPOSE

The aim of this Greek case-control study is to examine gene polymorphisms that have been previously shown or hypothesized to be correlated to degenerative OA. Gene polymorphisms, especially for OA, have never been previously studied in the Greek population.

STUDY DESIGN/SETTING

The study was conducted from May 2009 to December 2012. Eligible subjects who agreed to take part in the study were Greek adults from all of Greece, referred for consultation to the Palliative Care and Pain Relief Unit of Aretaieion University Hospital, in Athens, Greece.

PATIENT SAMPLE

A total of 601 matched pairs (cases and controls) participated in the study, 258 patients (188 women and 70 men) with clinically and radiologically confirmed degenerative OA and 243 control subjects (138 women and 105 men).

OUTCOME MEASURES

All patients presented with chronic pain at the spine (cervical, thoracic or lumbar) caused by sympomatic osteophytes or disc narrowing, whereas clinical diagnosis of OA was based on the presence of both joint symptoms and evidence of structural changes seen on plain conventional X-rays.

METHODS

We investigated genetic variation across candidate OA gene GDF5, CDMP1, CDMP2, Asporin, SMAD3, and chromosomal region 7q22, in a sample of 258 patients with clinically and radiologically confirmed degenerative OA, and 243 control subjects from the Greek population. All subjects (patients and controls) were subsequently matched for the epidemiologic, demographic, and clinical risk factors, to prevent selection biases. A tagging single nucleotide polymorphism (SNP) approach was pursued to cover variation across all targeted loci. Single marker tests as well as haplotypic tests of association were performed. There is no conflict of interest, and also, there are no study funding sources.

RESULTS

We found significant association of spine OA with SNPs and haplotypes along the 7q22 chromosomal region and the SMAD3 gene. At 7q22, single marker association tests showed SNPs rs3801954 and rs2023685 to be associated with the disorder (p-value .0312 and .0041, respectively), but only SNP rs2023685 retained a significant p-value (.046) after performing 1,000 permutation tests. At the SMAD3 gene, SNP rs422342 was also found to be statistically associated (p-value .0282) to intervertebral disc degeneration (permutation p-value .042).

CONCLUSIONS

This is the first study to investigate genetic variation in relation to spine OA in the Greek population. Our results indicate that the genetic basis of the disease may differ in the Greek population in relation to populations of Asian origin, although larger sample sizes are required to underpin the full extent of the involvement of analyzed loci.

Cushioning the cartilage: a canonical Wnt restricting matter

Wnt signalling pathways have key roles in joint development, homeostasis and disease, particularly in osteoarthritis. New data is starting to reveal the importance of tightly regulating canonical Wnt signalling pathway activation to maintain homeostasis and health in articular cartilage. In addition to the presence of different Wnt antagonists that limit pathway activation in articular cartilage, the reciprocal crosstalk between the canonical and non-canonical cascades and competitive antagonism between different Wnt ligands seem to be critical in restraining excessive Wnt pathway activation. Changes in transcriptional complex assembly upon Wnt pathway activation, epigenetic modulation of target gene transcription, in particular through histone modifications, and complex interactions between the Wnt signalling pathway and other signalling pathways, are also instrumental in adjusting Wnt signalling. In this Review, the cellular and molecular mechanisms involved in fine-tuning canonical Wnt signalling in the joint are updated, with a focus on the articular cartilage. The interventions for preventing or treating osteoarthritis are also discussed, which should aim to limit disease-associated excessive canonical Wnt activity to avoid joint damage.

Association of BMP-14 rs143383 ploymorphism with its susceptibility to osteoarthritis: A meta-analysis and systematic review according to PRISMA guideline

BACKGROUND

Osteoarthritis (OA) is a complex disease which can be caused by both environmental and genetic factors. A functional locus rs143383 of bone morphogenetic protein-14 (BMP-14) has been pointed out to be associated with OA etiology, but conflicting conclusions have been reached. To provide a more comprehensive conclusion about this issue, we performed this meta-analysis.

METHODS

Relevant studies were searched from electronic databases including PubMed, Chinese National Knowledge Infrastructure, Embase, and Wanfang. The strength of correlations was examined with pooled odds ratios (ORs) and 95% confidence intervals (95% CIs). Subgroup analyses stratified by ethnicity and source of control were carried out. All statistical analyses were performed with STATA software (version 12.0).

RESULTS

Overall, BMP-14 rs143383 polymorphism was negatively correlated with the susceptibility to knee OA and hand OA under genetic contrasts of CC versus TT, CC + TC versus TT, CC versus TT + TC, C versus T, TC versus TT (OR = 0.71, 95% CI = 0.65-0.79; OR = 0.81, 95% CI = 0.73-0.89; OR = 0.79, 95% CI = 0.71-0.86; OR = 0.85, 95% CI = 0.81-0.90; OR = 0.84, 95% CI = 0.75-0.93), and TC versus TT, CC versus TT + TC, C versus T (OR = 0.76, 95% CI = 0.65-0.89; OR = 0.79, 95% CI = 0.68-0.92; OR = 0.90, 95% CI = 0.85-0.95), respectively; similar results were observed in subgroups after stratification analyses. Additionally, the polymorphism also reduced hip OA risk in Asian group after stratified analysis by ethnicity.

CONCLUSION

BMP-14 rs143383 polymorphism may be a protective factor against OA occurrence.

Radiographic endophenotyping in hip osteoarthritis improves the precision of genetic association analysis

OBJECTIVE

Osteoarthritis (OA) has a strong genetic component but the success of previous genome-wide association studies (GWAS) has been restricted due to insufficient sample sizes and phenotype heterogeneity. Our aim was to examine the effect of clinically relevant endophenotyping according to site of maximal joint space narrowing (maxJSN) and bone remodelling response on GWAS signal detection in hip OA.

METHODS

A stratified GWAS meta-analysis was conducted in 2118 radiographically defined hip OA cases and 6500 population-based controls. Signals were followed up by analysing differential expression of proximal genes for bone remodelling endophenotypes in 33 pairs of macroscopically intact and OA-affected cartilage.

RESULTS

We report suggestive evidence (p<5×10-6) of association at 6 variants with OA endophenotypes that would have been missed by using presence of hip OA as the disease end point. For example, in the analysis of hip OA cases with superior maxJSN versus cases with non-superior maxJSN we detected association with a variant in the LRCH1 gene (rs754106, p=1.49×10-7, OR (95% CIs) 0.70 (0.61 to 0.80)). In the comparison of hypertrophic with non-hypertrophic OA the most significant variant was located between STT3B and GADL1 (rs6766414, p=3.13×10-6, OR (95% CIs) 1.45 (1.24 to 1.69)). Both of these associations were fully attenuated in non-stratified analyses of all hip OA cases versus population controls (p>0.05). STT3B was significantly upregulated in OA-affected versus intact cartilage, particularly in the analysis of hypertrophic and normotrophic compared with atrophic bone remodelling pattern (p=4.2×10-4).

CONCLUSIONS

Our findings demonstrate that stratification of OA cases into more homogeneous endophenotypes can identify genes of potential functional importance otherwise obscured by disease heterogeneity.

Why location matters - site-specific factors in rheumatic diseases

Rheumatic diseases follow a characteristic anatomical pattern of joint and organ involvement. This Review explores three interconnected mechanisms that might be involved in the predilection of specific joints for developing specific forms of arthritis: site-specific local cell types that drive disease; systemic triggers that affect local cell types; and site-specific exogenous factors, such as focal mechanical stress, that activate cells locally. The embryonic development of limbs and joints is also relevant to the propensity of certain joints to develop arthritis. Additionally, location-specific homeostasis and disease occurs in skin and blood vessels, thereby extending the concept of site-specificity in human diseases beyond rheumatology. Acknowledging the importance of site-specific parameters increases the complexity of current disease paradigms and brings us closer to understanding why particular disease processes manifest at a particular location.

Osteoarthritis year in review 2016: genetics, genomics and epigenetics

The purpose of this narrative review is to provide an overview of last year's publications in the field of genetics, genomics and epigenetics in the osteoarthritis (OA) field. Major themes arising from a Pubmed search on (epi)genetics in OA were identified. In addition, general developments in the fast evolving field of (epi)genetics are reviewed and relevance for the OA field is summarized. In the last 5 years, a number of genome-wide association studies have identified a modest number of genetic loci associated to OA. Continued functional research into these DNA variants is showing putative biological mechanisms underlying these associations. Over the last year, no additional large genome-wide association studies were published, but there clearly remains much to be discovered in the OA genetic field. A lot of research has been done into the epigenetics of OA over the last year. Several genome-wide screens examining the methylome of osteoarthritic cartilage were done. Pathway analysis confirmed deregulation of developmental and extracellular pathways in OA cartilage. Over the last year many microRNAs (miRNAs) have been identified that potentially play important roles in cartilage homeostasis and/or OA process. Continued research will learn whether these identified miRNAs are truly causal and can be used in clinical applications. Many of the epigenetic findings need further confirmation, but they highlight potential novel pathways involved in cartilage biology and OA.

TIMP-2 SNPs rs7342880 and rs4789936 are linked to risk of knee osteoarthritis in the Chinese Han Population

This study aimed to investigate whether functional polymorphisms in the tissue inhibitors of metalloproteinase-2 (TIMP-2) gene are associated with susceptibility to knee osteoarthritis (OA) in the Chinese Han population. Six TIMP-2 single nucleotide polymorphisms (SNPs) were assayed using MassARRAY in 300 patients clinically and radiographically diagnosed with knee OA and in 428 controls. Allelic and genotypic frequencies were compared between groups. Logistic regression adjusting for age and gender was used to estimate risk associations between specific genotypes and knee OA by computing odds ratios (ORs) and 95% confidence intervals (95% CIs). We found that allele "A" in rs7342880 was significantly associated with increased risk of knee OA (OR = 1.44, 95%CI = 1.09-1.91, p = 0.035). In addition, in the over-dominant model, rs4789936 correlated with reduced risk of knee OA, adjusting for age and gender (OR = 0.69, 95%CI = 0.49-0.98, p = 0.036). Finally, rs7342880 correlated with increased risk of knee OA in females. This study provides evidence that TIMP-2 is a knee OA susceptibility gene in the Chinese population and a potential diagnostic and preventive marker for the disease.

Heads, Shoulders, Elbows, Knees, and Toes: Modular Gdf5 Enhancers Control Different Joints in the Vertebrate Skeleton

Synovial joints are crucial for support and locomotion in vertebrates, and are the frequent site of serious skeletal defects and degenerative diseases in humans. Growth and differentiation factor 5 (Gdf5) is one of the earliest markers of joint formation, is required for normal joint development in both mice and humans, and has been genetically linked to risk of common osteoarthritis in Eurasian populations. Here, we systematically survey the mouse Gdf5 gene for regulatory elements controlling expression in synovial joints. We identify separate regions of the locus that control expression in axial tissues, in proximal versus distal joints in the limbs, and in remarkably specific sub-sets of composite joints like the elbow. Predicted transcription factor binding sites within Gdf5 regulatory enhancers are required for expression in particular joints. The multiple enhancers that control Gdf5 expression in different joints are distributed over a hundred kilobases of DNA, including regions both upstream and downstream of Gdf5 coding exons. Functional rescue tests in mice confirm that the large flanking regions are required to restore normal joint formation and patterning. Orthologs of these enhancers are located throughout the large genomic region previously associated with common osteoarthritis risk in humans. The large array of modular enhancers for Gdf5 provide a new foundation for studying the spatial specificity of joint patterning in vertebrates, as well as new candidates for regulatory regions that may also influence osteoarthritis risk in human populations.

Joints, such as the hip and knee, are crucial for support and locomotion in animals, and are the frequent sites of serious human diseases such as arthritis. The Growth and differentiation factor 5 (Gdf5) gene is required for normal joint formation, and has been linked to risk of common arthritis in Eurasians. Here, we surveyed the mouse gene for the regulatory information that controls Gdf5's expression pattern in stripes at sites of joint formation. The gene does not have a single regulatory sequence that drives expression in all joints. Instead, Gdf5 has multiple different control sequences that show striking specificity for joints in the head, vertebral column, shoulder, elbow, wrist, hip, knee, and digits. Rescue experiments show that multiple control sequences are required to restore normal joint formation in Gdf5 mutants. The joint control sequences originally found in mice are also present in humans, where they are marked as active regions during fetal development and post-natal life, and map to a large region associated with arthritis risk in human populations. Regulatory variants in the human GDF5 control sequences can now be studied for their potential role in altering joint development or disease risk at particular locations in the skeleton.

Association between GDF5 +104T/C polymorphism and knee osteoarthritis in Caucasian and Asian populations: a meta-analysis based on case-control studies

Background

Osteoarthritis (OA) is a degenerative joint disease with a complex genetic background. Variants in growth differentiation factor 5 (GDF5) have been reported to be associated with rheumatoid arthritis (RA) in several ethnic populations. The present study aimed to assess the association between the GDF5 +104T/C polymorphism and the susceptibility of the knee to OA through a meta-analysis of available case-control studies.

Methods

The PubMed and Science Direct citation databases were used to search electronic literature in order to identify studies published between January 2007 and July 2016 that evaluated the association between the GDF5 +104T/C polymorphism and the susceptibility of the knee to OA. Different genetic models were used to assess the pooled and stratified data.

Results

A positive association was found in all pooled studies (OR = 0.808, 95 % CI = 0.754–0.866, p < 0.001). Regarding genotypes, significant associations were found using a dominant model (OR = 0.777, 95 % CI = 0.708–0.852, p < 0.001), a recessive model (OR = 0.723, 95%CI = 0.623–0.839, p < 0.001), and an additive model (CC vs TT OR = 0.648, 95 % CI = 0.552–0.760, p < 0.001; CC vs CT OR = 0.801, 95 % CI = 0.685–0.936, p = 0.005). Meta-analysis data were stratified by ethnicity, and the GDF5 C allele was found to be positively associated with OA of the knee in both Caucasians and Asians, as were the GDF5 TC and CC genotypes. In addition, using an additive model, the CC genotype was found to be significantly associated with OA of the knee in both Caucasians and Asians when comparing CC vs TT genotypes, but not in Caucasians when comparing TT vs CT genotypes.

Conclusions

Meta-analysis results indicated that the GDF5 +104T/C polymorphism is a protective factor for OA among Caucasian and Asian populations.

Angiotensin-Converting Enzyme Insertion/Deletion Polymorphism and Susceptibility to Osteoarthritis of the Knee: A Case-Control Study and Meta-Analysis

Background

Studies of angiotensin-converting enzyme insertion/deletion (ACE I/D) polymorphisms and the risks of knee osteoarthritis (OA) have yielded conflicting results.

Objective

To determine the association between ACE I/D and knee OA, we conducted a combined case-control study and meta-analysis.

Methods

For the case-control study, 447 knee OA cases and 423 healthy controls were recruited between March 2010 and July 2011. Knee OA cases were defined using the Kellgren-Lawrence grading system, and the ACE I/D genotype was determined using a standard polymerase chain reaction. The association between ACE I/D and knee OA was detected using allele, genotype, dominant, and recessive models. For the meta-analysis, PubMed and Embase databases were systematically searched for prospective observational studies published up until August 2015. Studies of ACE I/D and knee OA with sufficient data were selected. Pooled results were expressed as odds ratios (ORs) with corresponding 95% confidence intervals (CI) for the D versus I allele with regard to knee OA risk.

Results

We found no significant association between the D allele and knee OA [OR: 1.09 (95% CI: 0.76–1.89)] in the present case-control study, and the results of other genetic models were also nonsignificant. Five current studies were included, and there were a total of six study populations after including our case-control study (1165 cases and 1029 controls). In the meta-analysis, the allele model also yielded nonsignificant results [OR: 1.37 (95% CI: 0.95–1.99)] and a high heterogeneity (I²: 87.2%).

Conclusions

The association between ACE I/D and knee OA tended to yield negative results. High heterogeneity suggests a complex, multifactorial mechanism, and an epistasis analysis of ACE I/D and knee OA should therefore be conducted.

Genetic Contribution to the Development of Radiographic Knee Osteoarthritis in a Population Presenting with Nonacute Knee Symptoms a Decade Earlier

This study examined the contribution of the osteoarthritis (OA) susceptibility genes ASPN, GDF5, DIO2, and the 7q22 region to the development of radiographic knee OA in patients with a mean age of 40.6 ± 7.9 years (standard deviation) and who suffered from nonacute knee complaints a decade earlier. Dose–response associations of four single nucleotide polymorphisms(SNPs) in the susceptibility genes were determined by comparing 36 patients who showed the development of OA on radiographs (Kellgren and Lawrence score ≥1) with 88 patients having normal cartilage with no development of OA on radiographs. Multivariate logistic regression analysis including the variables such as age, gender, body mass index, and reported knee trauma was performed. A dose–response association of DIO2 SNP rs225014: odds ratio (OR) 2.3, 95% confidence interval (CI) 1.1–4.5 (P = 0.019) and GDF5 SNP rs143383: OR 2.0, 95% CI 1.1–3.8 (P = 0.031) was observed with knee OA development. The ASPN and 7q22 SNPs were not associated with OA development.

Matrilin-3 Role in Cartilage Development and Osteoarthritis

The extracellular matrix (ECM) of cartilage performs essential functions in differentiation and chondroprogenitor cell maintenance during development and regeneration. Here, we discuss the vital role of matrilin-3, an ECM protein involved in cartilage development and potential osteoarthritis pathomechanisms. As an adaptor protein, matrilin-3 binds to collagen IX to form a filamentous network around cells. Matrilin-3 is an essential component during cartilage development and ossification. In addition, it interacts directly or indirectly with transforming growth factor β (TGF-β), and bone morphogenetic protein 2 (BMP2) eventually regulates chondrocyte proliferation and hypertrophic differentiation. Interestingly, matrilin-3 increases interleukin receptor antagonists (IL-Ra) in chondrocytes, suggesting its role in the suppression of IL-1β-mediated inflammatory action. Matrilin-3 downregulates the expression of matrix-degrading enzymes, such as a disintegrin metalloproteinase with thrombospondin motifs 4 (ADAMTS4) and ADAMTS5, matrix metalloproteinase 13 (MMP13), and collagen X, a hypertrophy marker during development and inflammatory conditions. Matrilin-3 essentially enhances collagen II and aggrecan expression, which are required to maintain the tensile strength and elasticity of cartilage, respectively. Interestingly, despite these attributes, matrilin-3 induces osteoarthritis-associated markers in chondrocytes in a concentration-dependent manner. Existing data provide insights into the critical role of matrilin-3 in inflammation, matrix degradation, and matrix formation in cartilage development and osteoarthritis.

Targeted re-sequencing of linkage region on 2q21 identifies a novel functional variant for hip and knee osteoarthritis

OBJECTIVE

The aim of the study was to identify genetic variants predisposing to primary hip and knee osteoarthritis (OA) in a sample of Finnish families.

METHODS

Genome wide analysis was performed using 15 independent families (279 individuals) originating from Central Finland identified as having multiple individuals with primary hip and/or knee OA. Targeted re-sequencing was performed for three samples from one 33-member, four-generation family contributing most significantly to the LOD score. In addition, exome sequencing was performed in three family members from the same family.

RESULTS

Genome wide linkage analysis identified a susceptibility locus on chromosome 2q21 with a multipoint LOD score of 3.91. Targeted re-sequencing and subsequent linkage analysis revealed a susceptibility insertion variant rs11446594. It locates in a predicted strong enhancer element region with maximum LOD score 3.42 under dominant model of inheritance. Insertion creates a recognition sequence for ELF3 and HMGA1 transcription factors. Their DNA-binding affinity is highly increased in the presence of A-allele compared to wild type null allele.

CONCLUSION

A potentially novel functional OA susceptibility variant was identified by targeted re-sequencing. This variant locates in a predicted regulatory site and creates a recognition sequence for ELF3 and HMGA1 transcription factors that are predicted to play a significant role in articular cartilage homeostasis.

Subchondral bone and osteoarthritis

PURPOSE OF REVIEW

Increasing evidence show that bone is a key factor in the development of osteoarthritis. This article reviews the latest results of basic and clinical research on the role of the subchondral bone in osteoarthritis.

RECENT FINDINGS

Early changes in the subchondral bone can predict subsequent symptoms or disease structural progression. New tools may help clinicians to stratify different osteoarthritis phenotypes with regards to bone remodeling status.

SUMMARY

The involvement of bone in osteoarthritis has long been thought to be secondary to cartilage damage as an adaptation of the joint. Recent clinical studies with MRI have demonstrated that bone changes could be observed in early stages of the disease, even preceding cartilage lesions. Moreover, there is clear evidence of an association between subchondral bone mineral density and osteoarthritis. The level of bone remodeling plays a critical role under mechanical loading conditions as demonstrated by consistent experimental studies. Yet new clinical biomarkers are being developed to assess the bone phenotype of osteoarthritic patients. This stratification strategy is likely to better identify groups of patients who would benefit from bone-acting drugs to decrease disease progression and improve pain and disability.

Wnt signaling in cartilage development and diseases: lessons from animal studies

Cartilage not only plays essential roles in skeletal development and growth during pre- and postnatal stages but also serves to provide smooth movement of skeletons throughout life. Thus, dysfunction of cartilage causes a variety of skeletal disorders. Results from animal studies reveal that β-catenin-dependent canonical and independent non-canonical Wnt signaling pathways have multiple roles in regulation of cartilage development, growth, and maintenance. β-Catenin-dependent signaling is required for progression of endochondral ossification and growth of axial and appendicular skeletons, while excessive activation of this signaling can cause severe inhibition of initial cartilage formation and growth plate organization and function in mice. In contrast, non-canonical Wnt signaling is important in columnar organization of growth plate chondrocytes. Manipulation of Wnt signaling causes or ameliorates articular cartilage degeneration in rodent osteoarthritis models. Human genetic studies indicate that Wnt/β-catenin signaling is a risk factor for osteoarthritis. Accumulative findings from analysis of expression of Wnt signaling molecules and in vivo and in vitro functional experiments suggest that Wnt signaling is a therapeutic target for osteoarthritis. The target tissues of Wnt signaling may be not only articular cartilage but also synovium and subchondral bone.