MicroRNAs (miRNAs) are small, single-stranded, non-coding RNA molecules of 20∼22 nucleotides, which are involved in many biologic functions such as development, cell proliferation, differentiation, and apoptosis. In addition to these biologic functions, recent reports have demonstrated that miRNAs play important roles in the development of the immune system and the regulation of immune responses. Dysregulation of miRNAs might be involved in the pathogenesis of autoimmune diseases such as rheumatoid arthritis (RA). Recent studies have shown that miR-146a, miR-155, and miR-203 are overexpressed in RA and that miR-124a is under expressed in RA. miR-146 downregulates the expression of IL-1 receptor associated kinase 1 and TNF receptor-associated factor 6 involved in IL-1Ղ signaling, and miR-155 suppresses the expression of matrix metalloproteinases 1 and 3, suggesting that these miRNAs act as negative feedback regulators of inflammation and tissue damage in RA. In this report, we review the current knowledge about miRNAs and summarize the involvement of miRNAs in RA.

Keywords: microRNA, Rheumatoid arthritis, Immune response