Big data boost for osteoarthritis genetics

LncRNA GAS5 upregulates Smad4 to suppress the apoptosis of chondrocytes induced by lipopolysaccharide

BACKGROUND

Osteoarthritis (OA) is closely correlated with inflammation. It has been reported that lncRNA GAS5 plays an important role in inflammation, indicating the potential involvement of GAS5 in OA. This study was carried out to investigate the function of GAS5 in OA.

METHODS

Expression levels of GAS5 in synovial fluid from 45 OA patients and 45 healthy controls were measured by RT-qPCR. Cell transfections were performed to explore the potential interactions among GAS5, miR-146a, and Smad4 in chondrocytes. Lipopolysaccharide (LPS)-induced cell apoptosis after overexpression of GAS5, miR-146a, and Smad4 was analyzed by cell apoptosis assay.

RESULTS

GAS5 was downregulated in OA. Moreover, LPS treatment downregulated GAS5 in chondrocytes. Interaction between GAS5 could with miR-146a was predicted by bioinformatics analysis and further confirmed by RNA-RNA pulldown assay. However, overexpression of GAS5 and miR-146a did not affect the expression of each other. GAS5 overexpression increased Smad4 expression in chondrocytes. In contrast, miR-146a overexpression downregulated Smad4 in chondrocytes. Moreover, GAS5 and Smad4 overexpression inhibited LPS- induced chondrocytes apoptosis, while miR-146a overexpression played an opposite role and attenuated the effects of GAS5 and Smad4 overexpression on cell apoptosis.

CONCLUSION

GAS5 might sponge miR-146a to upregulate Smad4, thereby suppressing LPS- induced chondrocytes apoptosis.

Association study of the functional variants of the GLIS3 gene with risk of knee osteoarthritis

INTRODUCTION/OBJECTIVES

Osteoarthritis (OA) ranks the most common joint disorder and the leading cause of disability. Growing evidence has revealed that OA has a strong genetic background, except for aging and obesity. The aim of this study is to determine the associations between potential functional variants of the GLIS3 and GLIS3-AS1 gene and risk of knee OA among a Chinese population.

METHODS

In this case-control study with 810 knee OA cases and 900 healthy controls, seven selected functional SNPs of the GLIS3 and GLIS3-AS1 gene were evaluated.

RESULTS

We found minor alleles of rs10116772 (OR: 0.80, 95% CI: 0.69-0.92, P = 0.002), rs7045410 (OR: 0.74, 95% CI: 0.61-0.92, P = 0.005), and rs7032713 (OR: 0.76, 95% CI: 0.63-0.93, P = 0.006) were significantly associated with decreased risk of knee OA. Results of the dominant and recessive model, stratified analyses using Kellgren-Lawrence (KL) grading presented that the significant associations were not materially changed. Haplotype analysis indicated that haplotype CGT (OR: 0.66, 95% CI: 0.46-0.96, P = 0.031) and ATT (OR: 0.76, 95% CI: 0.6-0.95, P = 0.017) were significantly associated with decreased risk of knee OA. Further, they were also significantly associated with lower expression level of GLIS3, as well as higher expression level of GLIS3-AS1 in the articular cartilage specimens. Genotype-tissue expression (GTEX) data also validated that minor alleles of rs7045410 and rs7032713 were significantly associated with higher expression level of GLIS3-AS1 in thyroid and pituitary tissues (P < 0.001).

CONCLUSIONS

These findings revealed the essential role of genetic variants of the GLIS3 and GLIS3-AS1 gene in the occurrence of knee OA together. Key Point • Functional variants of the GLIS3 and GLIS3-AS1 gene were significantly associated with decreased risk of knee OA.

Interleukin 1 receptor antagonist (IL1RN) gene variants predict radiographic severity of knee osteoarthritis and risk of incident disease

OBJECTIVE

In these studies, we examined the association of single nucleotide polymorphisms (SNPs) of the IL1RN gene with radiographic severity of symptomatic knee osteoarthritis (SKOA) and the risk of incident OA. We also explored these genetic polymorphisms in patients with new onset rheumatoid arthritis (RA).

METHODS

Over 1000 subjects who met American College of Rheumatology criteria for tibiofemoral OA were selected from three independent, National Institute of Health (NIH)-funded cohorts. CTA and TTG haplotypes formed from three SNPs of the IL1RN gene (rs419598, rs315952, rs9005) were assessed for association with radiographic severity, and risk for incident radiographic OA (rOA) in a nested case-control cohort. These IL1RN haplotypes were also assessed for association with disease activity (DAS28) and plasma inflammatory markers in patients with RA.

RESULTS

Carriage of the IL1RN TTG haplotype was associated with increased odds of more severe rOA compared with age-matched, sex-matched and body mass index-matched individuals. Examination of the osteoarthritis initiative Incidence Subcohort demonstrated that carriage of the TTG haplotype was associated with 4.1-fold (p=0.001) increased odds of incident rOA. Plasma IL-1Ra levels were lower in TTG carriers, while chondrocytes from TTG carriers exhibited decreased secretion of IL-1Ra. In patients with RA, the TTG haplotype was associated with increased DAS28, decreased plasma IL-1Ra and elevations of plasma inflammatory markers (hsCRP, interleukin 6 (IL-6)).

CONCLUSION

Carriage of the IL1RN TTG haplotype is associated with more severe rOA, increased risk for incident OA, and increased evidence of inflammation in RA. These data suggest that the IL1RN TTG risk haplotype, associated with decreased IL-1Ra plasma levels, impairs endogenous 'anti-inflammatory' mechanisms.

LncRNA LUADT1 regulates miR-34a/SIRT1 to participate in chondrocyte apoptosis

It is known that miR-34a can promote the apoptosis of chondrocytes, which directly contribute to osteoarthritis (OA). Through bioinformatics analysis, we found that long noncoding RNA LUADT1 may interact with miR-34a. We, therefore, further investigate the interactions between them in osteoarthritis. We found that LUADT1 was downregulated, while miR-34a was upregulated in OA synovial fluid. Correlation analysis revealed no significant correlation between them. Overexpression experiment also revealed no significant effects of LUADT1 and miR-34a on the expression of each other. However, the dual-luciferase assay showed that LUADT1 and miR-34a can directly interact with each other. Moreover, LUADT1 overexpression led to the upregulation of SIRT1, which is a downstream target of miR-34a. Cell apoptosis showed that LUADT1 and SIRT1 overexpression led to decreased, while miR-34a led to increased apoptotic rates of chondrocytes. Therefore, LUADT1 regulates miR-34a/SIRT1 to participate in chondrocyte apoptosis.

Update on the epidemiology, risk factors and disease outcomes of osteoarthritis

Osteoarthritis (OA) is the most frequent form of arthritis and a leading cause of pain and disability worldwide. OA can affect any synovial joint, although the hip, knee, hand, foot and spine are the most commonly affected sites. Knowledge about the occurrence and risk factors for OA is important to define the clinical and public health burden of the disease to understand mechanisms of disease occurrence and may also help to inform the development of population-wide prevention strategies. In this article, we review the occurrence and risk factors for OA and also consider patient-reported outcome measures that have been used for the assessment of the disease.