Osteoarthritis Susceptibility Research Articles

Powerful detection of osteoarthritis susceptibility loci by comprehensive examination of clinically important endophenotypes

1 PI3K Akt signaling pathway 337 21 2.96E-08 -5.30E+01 1.20E-02 8.09E-09 7.93E-07 7.93E-07 Inhibited 2 Circadian rhythm 30 7 2.04E-07 -7.24E+00 5.00E-02 1.98E-07 9.70E-06 1.94E-05 Inhibited 3 HIF-1-alpha transcription factor network 63 10 2.50E-08 1.55E+00 6.68E-01 3.16E-07 3.59E-05 4.49E-05 Activated 4 Validated transcriptional targets of AP1 family members Fra1 and Fra2 37 7 9.46E-07 6.56E+00 2.90E-02 5.05E-07 3.59E-05 7.17E-05 Activated

Vitamin D receptor gene polymorphisms and risk of osteoarthritis: A meta-analysis

The vitamin D receptor (VDR) gene polymorphisms have been reported to be involved in the development of many musculoskeletal disorders, including osteoarthritis (OA). However, results were inconsistent and there is no definite conclusion regarding the association between any VDR polymorphism and the risk of OA. In this study, we conducted a meta-analysis to determine whether BsmI, TaqI, and ApaI polymorphisms in the VDR gene are associated with OA susceptibility. Literature research was performed using PubMed and EMBASE databases. Studies illustrating the association between the three VDR polymorphisms and OA were included, and their qualities were assessed using Newcastle-Ottawa scale. Eight eligible studies, recruiting 1626 cases and 2024 controls were identified. Their methodological qualities were generally good, with scores ranging from 6 to 8 points. However, throughout all summary analyses, which were performed for multiple categories and on four contrasts (allele contrast, contrast of homozygotes, recessive and dominant models), none of the VDR BsmI, TaqI, and ApaI gene polymorphisms were found to be significantly associated with the risk of OA. On the other hand, there was no significant publication bias. Results from this meta-analysis suggested that the VDR BsmI, TaqI, and ApaI gene polymorphisms might not be important predictors of OA. More studies further investigating these associations, especially taking into account of gene-gene, gene-environment interactions, and other confounding factors are warranted.

Identification and analysis of a SMAD3 cis-acting eQTL operating in primary osteoarthritis and in the aneurysms and osteoarthritis syndrome

SummaryObjectiveThe TGF-β pathway plays a central role in joint development with polymorphism in TGF-β pathway genes implicated in osteoarthritis susceptibility. One association is to rs12901499, within intron 1 of SMAD3. Since rs12901499 is not in linkage disequilibrium with a non-synonymous polymorphism, it is likely the association is operating by influencing expression of SMAD3.DesignUsing tissues from the joints of primary osteoarthritis patients who had undergone joint replacement we measured the overall expression of SMAD3 by quantitative real-time PCR. We also measured allelic expression of SMAD3 using these tissues and vascular smooth muscle cells from patients with aneurysms and osteoarthritis syndrome, a rare condition featuring early-onset osteoarthritis. We tested the functional effect of SNPs in vitro using luciferase assays and assessed association with osteoarthritis using a large osteoarthritis case–control dataset.ResultsWe observed that genotype at rs12901499 did not correlate with overall SMAD3 expression or allelic expression. However, genotype at a 3′UTR SNP, rs8031440, did correlate with SMAD3 expression in cartilage (P = 0.005) which was supported by allelic expression data showing that the G allele correlated with decreased SMAD3 expression in joint tissues and vascular smooth muscle cells. This G allele was underrepresented in osteoarthritis cases vs controls (P = 0.027, odds ratio = 0.921). rs8031440 is in perfect linkage disequilibrium with five other SMAD3 3′UTR SNPs and our luciferase analysis identified rs3743342 and rs12595334 as being functional.ConclusionSMAD3 is subject to cis-acting regulatory polymorphism in the tissues of relevance to both primary osteoarthritis and the aneurysms-osteoarthritis syndrome.

Association between single nucleotide polymorphisms of sterol regulatory element binding protein-2 gene and risk of knee osteoarthritis in a Chinese Han population

To investigate associations between single nucleotide polymorphisms (SNPs) rs2228314 and rs2267443 in the sterol regulatory element binding protein-2 gene (SREBP-2) and knee osteoarthritis (OA) susceptibility in a Chinese Han population. SREBP-2 rs2228314 and rs2267443 polymorphisms were genotyped in patients with knee OA and age- and sex-matched OA-free controls from a Chinese Han population. A total of 402 patients with knee OA and 410 controls were enrolled in the study. GC and CC genotypes of rs2228314, and variant C, were associated with a significantly increased risk of knee OA. On stratification analysis, the association between the risk of OA and rs2228314 GC heterozygotes compared with GG homozygotes was stronger in females and those aged >65 years. In contrast, the GA and AA genotypes of rs2267443 were not significantly associated with the risk of knee OA, even after further stratification analysis according to age or sex. SREBP-2 rs2228314 G to C change and variant C genotype may contribute to knee OA risk in a Chinese Han population.

Human Chondrocytes Respond Discordantly to the Protein Encoded by the Osteoarthritis Susceptibility Gene GDF5

A genetic deficit mediated by SNP rs143383 that leads to reduced expression of GDF5 is strongly associated with large-joint osteoarthritis. We speculated that this deficit could be attenuated by the application of exogenous GDF5 protein and as a first step we have assessed what effect such application has on primary osteoarthritis chondrocyte gene expression. Chondrocytes harvested from cartilage of osteoarthritic patients who had undergone joint replacement were cultured with wildtype recombinant mouse and human GDF5 protein. We also studied variants of GDF5, one that has a higher affinity for the receptor BMPR-IA and one that is insensitive to the GDF5 antagonist noggin. As a positive control, chondrocytes were treated with TGF-β1. Chondrocytes were cultured in monolayer and micromass and the expression of genes coding for catabolic and anabolic proteins of cartilage were measured by quantitative PCR. The expression of the GDF5 receptor genes and the presence of their protein products was confirmed and the ability of GDF5 signal to translocate to the nucleus was demonstrated by the activation of a luciferase reporter construct. The capacity of GDF5 to elicit an intracellular signal in chondrocytes was demonstrated by the phosphorylation of intracellular Smads. Chondrocytes cultured with TGF-β1 demonstrated a consistent down regulation of MMP1, MMP13 and a consistent upregulation of TIMP1 and COL2A1 with both culture techniques. In contrast, chondrocytes cultured with wildtype GDF5, or its variants, did not show any consistent response, irrespective of the culture technique used. Our results show that osteoarthritis chondrocytes do not respond in a predictable manner to culture with exogenous GDF5. This may be a cause or a consequence of the osteoarthritis disease process and will need to be surmounted if treatment with exogenous GDF5 is to be advanced as a potential means to overcome the genetic deficit conferring osteoarthritis susceptibility at this gene.

Genetic, clinical and radiographic signs in knee osteoarthritis susceptibility

IntroductionOsteoarthritis (OA) is considered to be a multifactorial and polygenic disease and diagnosis is mainly clinical and radiological. Correlation between radiographic data and clinical status has been reported. However, very few studies, especially in Caucasian people, describe the association between the Kellgren and Lawrence OA grading scale (KL) and genetic alterations to better understand OA etiopathogenesis and susceptibility. In order to update the knee OA grading, in this study we assessed the associations between KL grade, clinical features such as American Knee Society Score (AKSS), age, and polymorphisms in the principal osteoarthritis susceptibility (OS) genes in Sicilian individuals.MethodsIn 66 Sicilian individuals affected by primary knee OA, the clinical and radiographic evaluation was performed using 2 sub-scores of AKSS (knee score (KS) and function score (FS)) and KL. The patients were also classified according to age. Online Mendelian Inheritance in Man (OMIM) and Database of Single Nucleotide Polymorphisms (dbSNP) Short Genetic Variations databases were used to select gene regions containing the following polymorphisms to analyze: FRZB rs288326 and rs7775, MATN3 rs77245812, ASPN D14 repeats, PTHR2 rs76758470, GDF5 rs143383 and DVWA rs11718863. Patient genotypes were obtained using Sanger DNA sequencing analysis.ResultsIn our cohort of patients a statistical association between the variables analyzed was reported in all associations tested (KL versus KS, FS and age). We observed that a mild to severe OA radiographic grade is related to severe clinical conditions and loss of articular function and that the severity of symptoms increases with age. Concerning the genotyping analysis, our results revealed a significant statistical association between KL grading and GDF5 rs143383 and DVWA rs11718863 genetic alterations. The latter was also associated with a more severe radiographic grade, displaying its predictive role as OA marker progression. Statistically significant association between clinical, radiographic and genetic signs observed, suggests extending the actual grading of knee OA based mainly on X-ray features.ConclusionsThis work represents a multidisciplinary and translational medicine approach to study OA where clinical, radiological, and OS5 and OS6 SNPs evaluation could contribute to better define grading and progression of OA and to the development of new therapies.

Association of HLA-DQB1 with the development of osteoarthritis

Osteoarthritis (OA) is a degenerative disease characterized by chronic inflammation of different joints in the body, which may lead to joint destruction and life disability. It is a complex disease of multifactorial etiology like genetic variation. Genetics is believed to be important in determining the susceptibility of OA. It was proven to be associated with histocompatibility locus antigen region. The aim of this study was to analyze of the frequencies of HLA-DQB1 alleles in OA Iraqi Arab Muslims. A cross–sectional case control comparative study included twenty six Iraqi Arab Muslims patients who had knee OA and admitted in the Orthopedic Department at Al-Kindy Teaching Hospital between September – 2012 to June – 2013, and compared to control ethnically matched group. HLA–DRQ1 genotyping was done by polymerase chain reaction-sequence-specific oligonucleotide probes (PCR-SSOP) method. There was an increased frequencies of HLA-DQB1*03:01:01 in patients with OA compared with healthy controls (P=0.0171, odds ratio=7.4118, 95% CI=1.4285-38.4564); also there were an increase in the HLA-DQB1* 02:01:01, HLA-DQB1* 0305 and *04 in patients with OA compared with the control group, but the differences were not statistically significant. Our results suggest a role of the HLA DQB1*03:01:01 system in the etiopathogenesis of OA.

A meta-analysis of the relationship between aspartic acid (D)-repeat polymorphisms in asporin and osteoarthritis susceptibility

Our aim was to determine whether asporin (ASPN) D-repeat polymorphisms are associated with susceptibility to osteoarthritis (OA). A meta-analysis was conducted to examine the association between the ASPN D14, D13, and D15 alleles and OA of the knee and hip in each ethnic group. In total, 9 studies from eight articles involving 4,417 OA patients and 3,403 controls were considered in the meta-analysis. Meta-analysis showed no association between OA and the ASPN allele coding for 14 D-repeats (D14) in the overall population (OR 1.161, 95 % CI 0.934-1.444, p = 0.178). Stratification by ethnicity identified no association between the ASPN D14 allele and OA in Europeans or Asians (OR 1.035, 95 % CI 0.914-1.173, p = 0.589; OR 1.537, 95 % CI 0.899-2.626, p = 0.116), respectively. However, high heterogeneity was found in Asians (I (2) = 81.2, p = 0.001). Meta-analysis of OA by site showed no association between knee and hip OA and the ASPN D14 allele (OR 1.240, 95 % CI 0.946-1.627, p = 0.119; OR 1.130, 95 % CI 0.767-1.665, p = 0.537). Meta-analysis of D14 versus D13 allele showed the same pattern of OA association as the D14 allele. No association was found between the ASPN D13 and D15 alleles and risk of developing OA by meta-analysis (OR 0.942, 95 % CI 0.840-1.056, p = 0.304; OR 1.050, 95 % CI 0.956-1.154, p = 0.306), respectively. This meta-analysis shows that the ASPN D14, D13, and D15 alleles are not associated with the development of OA in Europeans and Asians. Thus, further study of this relationship is required in homogenous populations because of the heterogeneity of the ASPN D14 allele observed in Asians.

Molecular Insight into the Association Between Cartilage Regeneration and Ear Wound Healing in Genetic Mouse Models: Targeting New Genes in Regeneration

Tissue regeneration is a complex trait with few genetic models available. Mouse strains LG/J and MRL are exceptional healers. Using recombinant inbred strains from a large (LG/J, healer) and small (SM/J, nonhealer) intercross, we have previously shown a positive genetic correlation between ear wound healing, knee cartilage regeneration, and protection from osteoarthritis. We hypothesize that a common set of genes operates in tissue healing and articular cartilage regeneration. Taking advantage of archived histological sections from recombinant inbred strains, we analyzed expression of candidate genes through branched-chain DNA technology directly from tissue lysates. We determined broad-sense heritability of candidates, Pearson correlation of candidates with healing phenotypes, and Ward minimum variance cluster analysis for strains. A bioinformatic assessment of allelic polymorphisms within and near candidate genes was also performed. The expression of several candidates was significantly heritable among strains. Although several genes correlated with both ear wound healing and cartilage healing at a marginal level, the expression of four genes representing DNA repair (Xrcc2, Pcna) and Wnt signaling (Axin2, Wnt16) pathways was significantly positively correlated with both phenotypes. Cluster analysis accurately classified healers and nonhealers for seven out of eight strains based on gene expression. Specific sequence differences between LG/J and SM/J were identified as potential causal polymorphisms. Our study suggests a common genetic basis between tissue healing and osteoarthritis susceptibility. Mapping genetic variations causing differences in diverse healing responses in multiple tissues may reveal generic healing processes in pursuit of new therapeutic targets designed to induce or enhance regeneration and, potentially, protection from osteoarthritis.

Association of IL-17A and IL-17F single nucleotide polymorphisms with susceptibility to osteoarthritis in a Korean population

The damage incurred in osteoarthritis (OA) is mediated by a variety of cytokines, growth factors and inflammatory mediators. The importance of the interleukin-17 (IL-17) family in inflammatory and autoimmune disease is becoming increasingly apparent. Microsatellite association mapping reveals a primary osteoarthritis susceptibility locus on chromosome 6p12.3-q13. IL-17A and IL-17F genes that resided on chromosome 6p12.3-q13 are believed to play an important role in the primary OA susceptibility. We investigated the allele and genotype of IL-17A G-197A and IL-17F T7488C in 302 OA patients and 300 healthy subjects as controls. We employed a PCR-SSCP assay to identify the genotypes IL-17A G-197A and IL-17F T7488C. For IL-17A G-197A, there were significant differences in frequencies of genotype and allele of IL-17A G-197A between OA patients and controls (both p<0.0001). For IL-17F T7488C, there were no significant differences in the allele frequency and genotype distribution for IL-17F T7488C between OA patients and controls (p=0.938 and p=0.1735, respectively). In conclusion, current study showed that polymorphism of IL-17A G-197A may be closely associated with susceptibility to the development of OA in the Korean population. However, there was no relationship between IL-17F T7488C polymorphism and OA susceptibility.

The D-repeat polymorphism in the ASPN gene and primary knee osteoarthritis in a Mexican mestizo population: a case–control study

BackgroundA genetic association between osteoarthritis (OA) and a polymorphism in the aspartic acid (D) repeat of the asporin (ASPN) gene has been reported in Japanese, Han Chinese, Greek and UK Caucasian populations of patients having knee and hip OA. Such an association has not been previously described among the Mexican mestizo population. The aim of this study was to analyze the association of the ASPN gene D-repeat polymorphism in a Mexican mestizo population with primary knee OA as well as in healthy controls. Materials and methodsA case–control study was conducted on a Mexican mestizo population of northern Mexico. The repeat polymorphism was genotyped in 440 subjects (218 cases and 222 healthy controls). Primary knee OA was diagnosed according to American College of Rheumatology and Kellgren-Lawrence criteria, and allelic association was examined adjusting for other risk variables. ResultsAfter adjusting for some covariates, menopause and the D16 allele showed a trend toward being risk factors for knee OA in a Mexican mestizo population. Also, the D12 allele could be considered as a protective factor. ConclusionsThese findings suggest that polymorphisms within the ASPN gene could influence knee OA susceptibility, but these associations must be confirmed by independent studies in larger samples and different ethnic groups to support the role of the D-repeat polymorphism in the ASPN gene as risk or protection factors for knee OA in a Mexican population.

Insights from human genetic studies into the pathways involved in osteoarthritis

Genetic studies have revealed that most loci associated with osteoarthritis (OA) show ethnic stratification, with limited overlap between Asian and European populations. Consequently, such studies have often focused on particular ethnic groups, with those performed in European cohorts yielding the most replicated associations. As for other common diseases, the OA susceptibility loci mapped to date account for only a fraction of disease heritability. Nevertheless, analysis of these loci could identify biological pathways related to OA pathogenesis. Such an approach is taken in this Review and provides valuable insights into OA aetiology. For example, several of the loci associated with OA contain genes encoding key regulators of skeletogenesis and endochondral ossification. Furthermore, direct and indirect regulation of gene transcription is highlighted as an important factor in this disease. Interestingly, genes encoding structural proteins of the cartilage extracellular matrix do not seem to be a repository for OA susceptibility. Therefore, susceptibility might operate at a regulatory rather than a structural level, which is a potentially promising finding, as the activities of regulators are amenable to therapeutic modulation. Greater clarity will emerge as more association signals are identified; nonetheless, patterns of aetiology are clearly discernible, from a molecular perspective, even with the relatively small number currently available.

Association of NADPH oxidase p22phox gene C242T, A640G and −930A/G polymorphisms with primary knee osteoarthritis in the Greek population

Osteoarthritis (OA) is the most common form of arthritis with still unknown pathogenic etiology and considerable contribution of genetic factors. Recently, a new emerging role of oxidative stress in the pathology of OA has been reported, lacking however elucidation of the underlying mechanism. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase being a complex enzyme produced by chondrocytes, presents the major source of reactive oxygen species and main contributor of increased oxidative stress. The present study aims to evaluate the association of NADPH oxidase p22phox gene C242T, A640G and -A930G polymorphisms with primary knee OA in the Greek population. One hundred fifty five patients with primary symptomatic knee OA participated in the study along with 139 matched controls. Genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism technique. Allelic and genotypic frequencies were compared between both study groups. NADPH p22phox -A930G polymorphism was significantly associated with knee OA in the crude analysis (P=0.018). No significant difference was detected for C242T and A640G polymorphisms (P>0.05). The association between -A930G polymorphism and knee OA disappeared when the results were adjusted for obesity (P=0.078, odds ratio 0.54, 95% CI 0.272-1.071). The interaction between all three polymorphisms was not significant. The present study shows that NADPH oxidase p22phox gene C242T, A640G and -A930G polymorphisms are not risk factors for knee OA susceptibility in the Greek population. Further studies are needed to give a global view of the importance of this polymorphism in the pathogenesis of OA.

The Identification of Trans-acting Factors That Regulate the Expression of GDF5 via the Osteoarthritis Susceptibility SNP rs143383

rs143383 is a C to T transition SNP located in the 5′untranslated region (5′UTR) of the growth differentiation factor 5 gene GDF5. The T allele of the SNP is associated with increased risk of osteoarthritis (OA) in Europeans and in Asians. This susceptibility is mediated by the T allele producing less GDF5 transcript relative to the C allele, a phenomenon known as differential allelic expression (DAE). The aim of this study was to identify trans-acting factors that bind to rs143383 and which regulate this GDF5 DAE. Protein binding to the gene was investigated by two experimental approaches: 1) competition and supershift electrophoretic mobility shift assays (EMSAs) and 2) an oligonucleotide pull down assay followed by quantitative mass spectrometry. Binding was then confirmed in vivo by chromatin immunoprecipitation (ChIP), and the functional effects of candidate proteins investigated by RNA interference (RNAi) and over expression. Using these approaches the trans-acting factors Sp1, Sp3, P15, and DEAF-1 were identified as interacting with the GDF5 5′UTR. Knockdown and over expression of the factors demonstrated that Sp1, Sp3, and DEAF-1 are repressors of GDF5 expression. Depletion of DEAF-1 modulated the DAE of GDF5 and this differential allelic effect was confirmed following over expression, with the rs143383 T allele being repressed to a significantly greater extent than the rs143383 C allele. In combination, Sp1 and DEAF-1 had the greatest repressive activity. In conclusion, we have identified four trans-acting factors that are binding to GDF5, three of which are modulating GDF5 expression via the OA susceptibility locus rs143383.

Analysis of the cartilage proteome from three different mouse models of genetic skeletal diseases reveals common and discrete disease signatures

SummaryPseudoachondroplasia and multiple epiphyseal dysplasia are genetic skeletal diseases resulting from mutations in cartilage structural proteins. Electron microscopy and immunohistochemistry previously showed that the appearance of the cartilage extracellular matrix (ECM) in targeted mouse models of these diseases is disrupted; however, the precise changes in ECM organization and the pathological consequences remain unknown. Our aim was to determine the effects of matrilin-3 and COMP mutations on the composition and extractability of ECM components to inform how these detrimental changes might influence cartilage organization and degeneration.Cartilage was sequentially extracted using increasing denaturants and the extraction profiles of specific proteins determined using SDS-PAGE/Western blotting. Furthermore, the relative composition of protein pools was determined using mass spectrometry for a non-biased semi-quantitative analysis.Western blotting revealed changes in the extraction of matrilins, COMP and collagen IX in mutant cartilage. Mass spectrometry confirmed quantitative changes in the extraction of structural and non-structural ECM proteins, including proteins with roles in cellular processes such as protein folding and trafficking. In particular, genotype-specific differences in the extraction of collagens XII and XIV and tenascins C and X were identified; interestingly, increased expression of several of these genes has recently been implicated in susceptibility and/or progression of murine osteoarthritis.We demonstrated that mutation of matrilin-3 and COMP caused changes in the extractability of other cartilage proteins and that proteomic analyses of Matn3 V194D, Comp T585M and Comp DelD469 mouse models revealed both common and discrete disease signatures that provide novel insight into skeletal disease mechanisms and cartilage degradation.

AB0001 Genetic polymorphism in GDF-5 gene as risk factor for development and progression of osteoarthritis

BackgroundThe etiological factors of osteoarthritis are not fully characterized though the pathology of osteoarthritis is well defined. Genome sequencing resulted in identification of several susceptibility loci confirming the genetic association...

OP0034 The association between radiographic hand osteoarthritis and meniscal damage on MRI in the general population

BackgroundMeniscal damage is a potent risk factor for the development and progression of knee osteoarthritis (OA). However, studies addressing the possible cause(s) of meniscus lesions are sparse.ObjectivesTo gain new insights...

SP0044 Joint development and disease: The chicken limb model and the importance of GDF5

The chicken embryo is a widely used model for studying vertebrate limb development because of its ease of access and genetic and pharmacologic manipulation. During the formation of limbs the...

FRZB is a critical modulator of canonical WNT signalling in cartilage biology

Purpose: Polymorphisms in Frizzled-related protein (FRZB), a WNT antagonist, have been associated with osteoarthritis (OA). However, a recent meta-analysis failed to find a consistent effect of FRZB genetic variants on OA susceptibility. Our transcriptomics analysis in Frzb-/- mice provided evidence for a tight regulation of WNT signalling and highlighted the complex role for FRZB in joint homeostasis. We previously demonstrated that Frzb-/- mice have increased damage when dramatically challenged by papain, collagenase or severe inflammation. As these models are acute and short-term, we aimed to further investigate the effect of Frzb loss in a true translational model of OA and to study molecular interactions in the ATDC5 micromass in vitro model using RT-PCR and Western blot analysis. Methods: Surgical destabilization of the medial meniscus (DMM) was performed on the right knee of eight-week-old male Frzb-/- and wild-type mice. Eight weeks after surgery, mice were sacrificed and histological scores were determined for the femoral and tibial articular surfaces following the OARSI histopathology initiative guidelines. Results: Overexpression of Frzb in ATDC5 micro-masses boosted chondrogenesis with up-regulation of Col2a1 and Aggrecan transcription, whereas downregulation of Frzb lead to a decreased expression of Col2a1 and Aggrecan. These results corresponded with a reduction or increase in the activation of canonical WNT signalling pathway, respectively. Fluctuating levels of Frzb did not influence the Wnt/CamKII signalling pathway. The semi-quantitative OARSI score showed a significant increase in cartilage erosion in DMM-operated Frzb-/- mice compared to wild-type. Conclusions: Our data show that, in addition to the higher susceptibility to OA in acute induced models, Frzb-/- mice are more prone to OA in a full translational model of the disease characterized by slowly progressive joint damage. Overexpression of Frzb stimulates chondrogenesis by its inhibitory role on WNT/β-catenin signalling.

Inhibition of COG5, a gene from the C7q22 osteoarthritis susceptibility locus, induces glycosylation defects and affects chondrogenesis and osteogenesis by disturbing Wnt signaling

Purpose: Osteoarthritis (OA) is a highly disabling pathology of the bone-cartilage unit, to which both patient-dependent (weight excess, trauma⋯) and genetic factors contribute. Recently, a locus at chromosome 7q22 was linked to knee and hand OA by genome wide association study. In this locus, the Conserved oligomeric Golgi complex subunit (COG) 5 gene encodes a component of Golgi apparatus. Mutations in humans are associated with mild congenital glycosylation disorders, and COG5 expression is higher in 3D than in monolayer cultures of articular chondrocytes. Here we investigated on the role of COG5 during chondrogenesis and osteogenesis. Methods: We used three independent stable clonal colonies of each, controls (non-sliencing vector) and COG5 knocked-down cells (COG5-), established in the chondrogenic ATDC5 and osteogenic MC3T3-E1 cell lines. ATDC5 were cultured as high density micromasses (2x105 cells/10 μl) to mimic the condensation step of developing cartilage. Chondrogenesis was induced by culturing cells for 14 days (D) in DMEM/F12 + 5%FBS, supplemented with ITS (insulin, transferrin, sodium selenite). On D14, cells were switched to mineralization medium (αMEM + 5%FBS, supplemented with ITS, β-glycerophosphate (BGP) and ascorbic acid (AA)) to investigate the mineralization phase of late chondrogenesis. Monolayers of MC3T3-E1 were cultured for 21D in αMEM + 10%FBS, supplemented with BGP and AA. mRNA expression of typical chondrogenesis markers (Aggrecan (Agg), type II (Col2a1) and X (Col10a1)) collagens and osteogenic markers (Osterix (Osx), Osteocalcin (Ocn) and Osteopontin (Opn)) were assessed by quantitative RT-PCR. We also assessed mRNA expression of Wnts (-4, -5a, -5b, -11) and BMPs (-2, -4, -6, -7). Quantification of Alcian Blue, Safranin O, Sirius red and Alizarin red staining were used to evaluate proteoglycans, collagens and mineralized content respectively. Alkaline phosphatase (ALP) activity allowed to monitor osteogenesis. SDS-PAGE was used to assess the global glycosylation status. Western blot allowed to check canonical (β-catenin) and non-canonical (Calmodulin-Kinase II) Wnt signaling, as well as BMP signaling (Smad and MAPK). Results: During early proliferation (D1-7) and late proliferation/pre-hypertrophy phases (D7-14) of chondrogenesis, Col2a1 and Agg mRNA strongly increased, but to a lesser extent in COG5-. Proteoglycan staining intensity was lower in COG5-. BMP-4 levels progressively increased and were significantly higher in COG5-. This was consistent with increased phosphorylation of Smad 1/5/8. Wnt-4, -5a and -5b mRNA were evenly increased in both controls and COG5-. BMP-6 and Col10a1 mRNA were increased at D14, but were significantly lower in COG5-. Wnt-11 mRNA increased in controls, but not in COG5-. In mineralization phase (D14 to D21), Col10a1 mRNA and mineralization were strongly increased, but to a lesser extent in COG5-. During osteogenesis, Opn, Osx and Ocn mRNA were significantly higher in controls, alike Alizarin red staining and ALP activity. Protein analysis suggested differences in global glycosylation status, in particular of Wnt ligands. Conclusions: COG5 defect reduces chondrogenesis and osteogenesis. COG5 particularly affected glycosylation and Wnt signaling, underlining its critical role in the fate of cells from the articular chondrocyte-bone unit in the course of OA.