Altered Expression of MicroRNA-203 in Rheumatoid Arthritis Synovial Fibroblasts and Its Role in Fibroblast Activation

Objective. MicroRNA (miRNA) are recognized as important regulators of a variety of fundamental biologic processes. Previously, we described increased expression of miR-155 and miR-146a in rheumatoid arthritis (RA) and showed a repressive effect of miR-155 on matrix metalloproteinase (MMP) expression in RA synovial fibroblasts (RASFs). The present study was undertaken to examine alterations in expression of miR-203 in RASFs and analyze its role in fibroblast activation. Methods. Differentially expressed miRNA in RASFs versus osteoarthritis synovial fibroblasts (OASFs) were identified by real-time polymerase chain reaction (PCR)-based screening of 260 individual miRNA. Transfection of miR-203 precursor was used to analyze the function of miR-203 in RASFs. Levels of interleukin-6 (IL-6) and MMPs were measured by real-time PCR and enzyme-linked immunosorbent assay. RASFs were stimulated with IL-1 beta, tumor necrosis factor alpha (TNF alpha), lipopolysaccharide (LPS), and 5-azacytidine (5-azaC). Activity of I kappa B kinase 2 was inhibited with SC-514. Results. Expression of miR-203 was higher in RASFs than in OASFs or fibroblasts from healthy donors. Levels of miR-203 did not change upon stimulation with IL-1 beta, TNF alpha, or LPS; however, DNA demethylation with 5-azaC increased the expression of miR-203. Enforced expression of miR-203 led to significantly increased levels of MMP-1 and IL-6. Induction of IL-6 by miR-203 overexpression was inhibited by blocking of the NF-kappa B pathway. Basal expression levels of IL-6 correlated with basal expression levels of miR-203. Conclusion. The current results demonstrate methylation-dependent regulation of miR-203 expression in RASFs. Importantly, they also show that elevated levels of miR-203 lead to increased secretion of MMP-1 and IL-6 via the NF-kappa B pathway and thereby contribute to the activated phenotype of synovial fibroblasts in RA.