Identification of sequence polymorphisms of the COMP (cartilage oligomeric matrix protein) gene and association study in osteoarthrosis of the knee and hip joints

Identifying the role of ASPN and COMP genes in knee osteoarthritis development

Background

Osteoarthritis (OA) is a common cause of musculoskeletal disability among elders and is characterized by late-onset degeneration of articular cartilage. OA affects various joints, commonly hand, knee, and hip, with clinical features that are unique to each joint. This study was initiated to identify and evaluate the role of the ASPN and COMP genes in the development of knee OA.

Methods

A case–control study was carried out involving 500 cases with knee OA (diagnosed by the American College of Rheumatology) and an equal number of healthy controls. Blood was drawn for genomic DNA isolation. PCR-RFLP and TaqMan assay methods were used to identify the SNPs. mRNA and protein expression of genes were carried out in peripheral blood lymphocytes (PBLs) by RT-PCR and Western immunoblotting. The data obtained were analyzed for the statistical significance between control and case groups.

Results

The variant genotype of ASPN and COMP genes was found to be present at a relatively higher frequency in cases than controls. RT-PCR and immunochemical studies revealed increased mRNA and protein expression of such gene in PBLs isolated from cases of knee OA as compared to healthy control.

Conclusion

The allelic alteration in ASPN and COMP genes in knee OA cases points to the role of these genes in the development of knee OA. Further, increased mRNA and protein expression of ASPN and COMP in peripheral blood samples of patients with the disease suggest that expression profile of candidate gene could be used as a biomarker for predicting the development and progression of knee OA.

The genetics behind osteoarthritis: Asian focus

Osteoarthritis (OA), a degenerative joint disease, is the most common form of arthritis in the elderly. Problems arising from the condition are not only health, physical, and psychological, but also economical and social. OA is a complex disease causes by environmental factors (obesity, female gender, advancing age) and genetics. A strong genetic contribution to primary OA has been observed in several studies. Asian population is undoubtedly genetically different from European, whom most studies have been performed. This review systematically compares results of molecules involved with OA from studies performed on Asian and Caucasian populations. The clear differences between Asian and Caucasian populations may be from the sex- and ethnic-specific nature of the disease, as well as from the inclusion criteria of the studies. Global collaboration is highly significant in understanding genetic underlying OA. Knowledge gained from genetic study is important to the development of prevention and therapeutic intervention, and to identify individuals at risk of developing severe or progressive OA.

Evaluating the clinical relevance of codon 594 (g>a) polymorphism of estrogen receptor alpha in knee osteoarthritis

It has been reported that oestrogen receptor alpha (ER-α) polymorphisms are associated with knee osteoarthritis (OA). In this study, we assessed whether there was any association between the codon 594 (G>A) polymorphism in ER-α and radiographic features of OA or patient function. Radiographs, WOMAC score and patient reported time of symptom onset were assessed in 194 patients presenting for total knee replacement at Ramathibodi hospital over a one year period. ESR-1 genotyping was assessed. There were 107 (55.15%) patients with common homozygote (GG), 78 (40.20%) patients with heterozygote (GA) and nine (4.65%) patients with rare homozygote (AA). There was poor correlation (r = <0.2) between group difference in the radiographic parameters, time of onset of symptom , or in WOMAC scores. This polymorphism is not associated with the clinical features of knee osteoarthritis. The role of this polymorphism is unlikely then to be used as a biological marker predicting the progression of knee OA.

Rs143383 in the growth differentiation factor 5 (GDF5) gene significantly associated with osteoarthritis (OA)-a comprehensive meta-analysis

Family, twin, adoption studies show osteoarthritis (OA) has a substantial genetic component. Several studies have shown an association between OA and Growth Differentiation Factor 5 (GDF5), some others have not. Thus, the status of the OA-GDF5 association is uncertain. This meta-analysis was applied to case-control studies of the association between OA and GDF5 to assess the joint evidence for the association, the influence of individual studies, and evidence for publication bias. Relevant studies were identified from the following electronic databases: MEDLINE and current contents before Feb. 2012. For the case-control studies, the authors found 1) support for the association between OA and GDF5. The rs143383 polymorphism was significantly associated with OA [fixed: OR and 95% CI: 1.193 (1.139-1.249), p < 0.001; random: OR and 95% CI: 1.204 (1.135-1.276), p < 0.001], 2) no evidence that this association was accounted for by any one study, and 3) no evidence for publication bias. Although the effect size of the association between OA and GDF5 is small, there is suggestive evidence for an association. Further studies are needed to clarify what variant of GDF5 (or some nearby gene) accounts for this association.

A genetic association study between growth differentiation factor 5 (GDF 5) polymorphism and knee osteoarthritis in Thai population

Objective

Osteoarthritis (OA) is a multi-factorial disease and genetic factor is one of the important etiologic risk factors. Various genetic polymorphisms have been elucidated that they might be associated with OA. Recently, several studies have shown an association between Growth Differentiation Factor 5(GDF5) polymorphism and knee OA. However, the role of genetic predisposing factor in each ethnic group cannot be replicated to all, with conflicting data in the literatures. Therefore, the aim of this study was to investigate the association between GDF5 polymorphism and knee OA in Thai population.

Materials and Methods

One hundred and ninety three patients aged 54-88 years who attended Ramathibodi Hospital were enrolled. Ninety cases with knee OA according to American College of Rheumatology criteria and one hundred and three cases in control group gave informed consent. Blood sample (5 ml) were collected for identification of GDF5 (rs143383) single nucleotide polymorphism by PCR/RFLP according to a standard protocol. This study protocol was approved by the Ethics Committee on human experimentation of Ramathibodi Hospital Faculty of Medicine, Mahidol University. Odds ratios (OR) and 95% confidence intervals were calculated for the risk of knee OA by genotype (TT, TC and CC) and allele (T/C) analyses.

Results

The baseline characteristics between two groups including job, smoking and activity were not different, except age and BMI. The entire cases and controls were in Hardy-Weinberg equilibrium (p > 0.05). The OA knee group (n = 90) had genotypic figure which has shown by TT 42.2% (n = 38), TC 45.6% (n = 41) and CC 12% (n = 11), whereas the control group (n = 103) revealed TT 32% (n = 33), TC 45.6% (n = 47), and CC 22.3% (n = 23), respectively. Genotypic TT increased risk of knee OA as compared to CC [OR = 2.41 (P = 0.04, 95%CI = 1.02-5.67)]. In the allele analysis, the T allele was found to be significantly associated with knee OA [OR = 1.53 (P = 0.043, 95%CI = 1.01-2.30)].

Conclusion

These data suggested that GDF5 polymorphism has an association with knee OA in Thai ethnic. This finding also supports the hypothesis that OA has an important genetic component in its etiology, and GDF5 protein might play important role in the pathophysiology of the disease.

Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative disorder characterized by cartilage loss. Its prevalence is high, and it is a major cause of disability. The cause of OA is not known; however, current evidence indicates that it is multifactorial. Major risk factors for osteoarthritis are age, female sex, obesity, geographic factors, occupational knee-bending, physical labour, genetic factors and race, joint trauma, vitamin D deficiency, and chondrocalcinosis. Osteoarthritis causes joint pain, stiffness, and limitation of joint function. Knee involvement is the commonest presentation of this disease all over the world. Given the absence of a curative treatment, it is important to treat osteoarthritis as effectively as possible using a multidisciplinary approach tailored to the patient's needs. This article reviews current thinking on the epidemiology, clinical presentation, lifestyle, genetic epidemiology, and management of osteoarthritis in developing countries.

[Progress of molecular genetic research on pseudoachon-droplasia and multiple epiphyseal dysplasia]

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) belong to the family of bone dysplasia disorders, which are both genetically and phenotypically heterogeneous. Both disorders are caused by mutations in the cartilage oligomeric matrix protein (COMP). COMP is a member of the thrombospondin (TSP) family, which plays an important role in skeletal development. In this paper, we mainly review the latest advances on the structure, function of COMP. We also discuss the types of COMP mutations, the detection methods and the relationship between the COMP gene and these two diseases.

A functional polymorphism in the 5′ UTR of GDF5 is associated with susceptibility to osteoarthritis

Osteoarthritis (MIM 165720), characterized by degeneration of articular cartilage, is the most common form of human arthritis and a major concern for aging societies worldwide. Epidemiological and genetic studies have shown that osteoarthritis is a polygenic disease. Here, we report that the gene encoding growth differentiation factor 5 (GDF5) is associated with osteoarthritis in Asian populations. A SNP in the 5' UTR of GDF5 (+104T/C; rs143383) showed significant association (P = 1.8 x 10(-13)) with hip osteoarthritis in two independent Japanese populations. This association was replicated for knee osteoarthritis in Japanese (P = 0.0021) and Han Chinese (P = 0.00028) populations. This SNP, located in the GDF5 core promoter, exerts allelic differences on transcriptional activity in chondrogenic cells, with the susceptibility allele showing reduced activity. Our findings implicate GDF5 as a susceptibility gene for osteoarthritis and suggest that decreased GDF5 expression is involved in the pathogenesis of osteoarthritis.

Genetic analysis of skeletal dysplasia: recent advances and perspectives in the post-genome-sequence era

Skeletal dysplasia is a group of disorders of the skeleton that result from derangement of growth, development and/or differentiation of the skeleton. Nearly 300 disorders are included; most of them are monogenic diseases. Responsible genes for skeletal dysplasia have been identified in more than 150 diseases mainly through positional cloning. Identification of disease genes would improve patient care through genetic diagnosis as well as improving our understanding of the diseases and molecular mechanism of skeletal tissue formation. Studies of skeletal dysplasia would also help identify disease genes for common diseases affecting bones and joints. In this study, the author reviews recent advances and the current status of the genetic analysis of skeletal dysplasia and its impacts on research into skeletal biology.

The heritable determinants of cartilage oligomeric matrix protein

OBJECTIVE

Cartilage oligomeric matrix protein (COMP) is a cartilage matrix macromolecule. The protein is detectable in serum and has been investigated as a biomarker of osteoarthritis (OA). An association between COMP and OA has been shown, yet the precise factors governing serum levels of COMP remain unclear. The aim of this study was to determine whether genetic factors influence serum levels of COMP.

METHODS

A classic twin study was conducted using COMP levels in serum obtained from healthy female twin volunteers. COMP levels were determined by an inhibition enzyme-linked immunosorbent assay method. The heritability of COMP was determined by comparing correlation among 160 monozygotic and 349 dizygotic twin pairs. Data on potential confounding factors, including age, body mass index, and the presence of OA as assessed by hand, hip, and knee radiographs, were included in the analysis.

RESULTS

Serum levels of COMP showed a correlation of 0.72 (95% confidence interval [95% CI] 0.65-0.80) among monozygotic twin pairs and 0.47 (95% CI 0.39-0.55) in dizygotic pairs. This equated to an estimated heritability for COMP of 40% (95% CI 20-60%). Although age and body mass index were found to be significantly associated with COMP in regression analysis, taking the effects of these factors into account did not influence the estimate of heritability.

CONCLUSION

This study showed that heritable factors influence serum levels of the cartilage matrix biomarker COMP. Together with other published data, the results suggest that genetic factors operate at an early stage in the etiologic pathways that influence the development of radiographically discernible OA.

Sex and ethnic differences in the association ofASPN,CALM1,COL2A1,COMP, andFRZB with genetic susceptibility to osteoarthritis of the knee

OBJECTIVE

To assess whether the association of genetic polymorphisms with osteoarthritis (OA) in other populations could be replicated in a large, multicenter, mixed-sex, case-control study of clinical knee OA.

METHODS

Genetic polymorphisms in OA candidate genes were genotyped in 298 men and 305 women, ages 50-86 years, all of whom had a diagnosis of knee OA as assessed clinically and radiographically, and in 300 male and 299 female control subjects matched for age and ethnicity. Allele and haplotype frequencies for 5 genes (ASPN, CALM1, COL2A1, COMP, and FRZB) previously tested for association with hip and/or knee OA in other populations were compared between patients and control subjects, analyzing men and women separately.

RESULTS

The same FRZB 2-marker single-nucleotide polymorphism (SNP) haplotype associated with hip OA in other populations of Caucasian women was shown to increase the risk of knee OA among the women (but not the men) in the current study (odds ratio [OR] 2.87, P < 0.04). The CALM1 SNP, which affects the risk of hip OA in Japanese individuals, was not shown to be associated with susceptibility to OA in men or women. COL2A1 haplotypes were demonstrated to be associated with a decreased risk of knee OA in men (OR 0.68, P < 0.005) but not in women. COMP haplotypes that were associated with susceptibility to knee OA were different in men and women (P < 0.014 and P < 0.032, respectively). A meta-analysis of these data and those from previously published reports indicated a strong association between the FRZB G324 allele (P < 0.0003) and suggested that an ASPN allele is protective against the risk of knee OA in Caucasians (P < 0.02).

CONCLUSION

Our results indicate that genetic polymorphisms affecting knee OA vary between populations (Japanese versus Caucasian) and sexes and indicate a role for ASPN, COMP, FRZB, and COL2A1 in Caucasians.

An aspartic acid repeat polymorphism in asporin inhibits chondrogenesis and increases susceptibility to osteoarthritis

Osteoarthritis is the most common form of human arthritis. We investigated the potential role of asporin, an extracellular matrix component expressed abundantly in the articular cartilage of individuals with osteoarthritis, in the pathogenesis of osteoarthritis. Here we report a significant association between a polymorphism in the aspartic acid (D) repeat of the gene encoding asporin (ASPN) and osteoarthritis. In two independent populations of individuals with knee osteoarthritis, the D14 allele of ASPN is over-represented relative to the common D13 allele, and its frequency increases with disease severity. The D14 allele is also over-represented in individuals with hip osteoarthritis. Asporin suppresses TGF-beta-mediated expression of the genes aggrecan (AGC1) and type II collagen (COL2A1) and reduced proteoglycan accumulation in an in vitro model of chondrogenesis. The effect on TGF-beta activity is allele-specific, with the D14 allele resulting in greater inhibition than other alleles. In vitro binding assays showed a direct interaction between asporin and TGF-beta. Taken together, these findings provide another functional link between extracellular matrix proteins, TGF-beta activity and disease, suggesting new therapeutic strategies for osteoarthritis.

Mutations in the known genes are not the major cause of MED; distinctive phenotypic entities among patients with no identified mutations

Multiple epiphyseal dysplasia (MED) is a clinically and genetically heterogeneous chondrodysplasia. Mutations in six genes (COMP, COL9A1, COL9A2, COL9A3, MATN3 and DTDST) have been reported, but the genotype-phenotype correlations and the proportions of cases due to mutations in these genes are still not well characterized. We performed a clinical, radiological and molecular analysis of known MED genes on 29 consecutive MED patients. The mutation analysis resulted in identification of the DTDST mutation in four patients (14%), the COMP mutation in three (10%) and the MATN3 mutation in three (10%). Thus, a disease-causing mutation was identified in 10 patients altogether (34%). The phenotypic features observed in the patients with mutations were in accordance with previously described phenotypes, but two new distinct phenotypic entities were identified in patients in whom no mutation was found. One of them was characterized by severe, early-onset dysplasia of the proximal femurs with almost complete absence of the secondary ossification centres and abnormal development of the femoral necks. The other phenotype was characterized by 'mini-epiphyses', resulting in severe dysplasia of the proximal femoral heads. The findings suggest that mutations in the known genes are not the major cause of MED and are responsible for less than half of the cases. The existence of additional MED loci is supported by the exclusion of known loci by mutation analysis and finding of specific subgroups among these patients.

Measurement of structural progression in osteoarthritis of the hip: the Barcelona consensus group

OBJECTIVE

To outline the best available method of measurement for detecting progression of osteoarthritis (OA) of the hip especially in therapeutic trials.

METHOD

A Medline search of articles related to progression of hip OA was performed. A group of experts met over a 1.5-day session to review available literature and new research. Specific questions were addressed in order to reach a consensus on measuring progression of OA of the hip.

RESULTS

Of the available surrogate measures, a single yearly standing or reclined antero-posterior plain radiograph of the pelvis with feet internally rotated 15-20 degrees, can be evaluated with the use of an atlas for joint space width (JSW, interbone distance). There should be a minimum JSW upon baseline screening that may be 1 or 2 mm. Digitization of films offers a slight reduction in variability of measurements. Progression of OA can be calculated by measurement of the JSW on paired and blinded films. A reduction of > or = 0.5 mm is greater than the 'minimum perceptible difference' as well as the variation of most imaging techniques, and represents a clinically relevant and significant reduction in the JSW. Narrowing of the superomedial or superolateral JSW may tend to progress more rapidly than other changes. In clinical trials, patients who discontinue the study treatment need to be followed after discontinuation, and an imputation strategy which provides unbiased estimates of both the treatment effect and its variance is an appropriate technique for intent-to-treat analysis.

CONCLUSION

For the development of new agents intended to prevent, retard, stabilize or reverse the progress of OA of the hip, the radiographic methodology presently available is adequate to detect changes in hip JSW of OA.