A mini-review: microRNA in arthritis.

MicroRNA (miRNA) is a class of noncoding RNA that exhibits tissue- or developmental stage-specific expression patterns and negatively regulates gene expression. MiRNAs play an important role in human diseases, including osteoarthritis (OA) and rheumatoid arthritis (RA). OA is characterized by the progressive destruction of articular cartilage, and several miRNAs exhibit altered expression, playing a role in regulating gene expression in OA pathogenesis, especially in catabolic factors such as matrix metalloproteinases (MMP) and aggrecanases. RA is an autoimmune disease that is characterized by irreversible joint destruction due to chronic synovial inflammation. MiRNAs play an important role in inflammatory response, synovial cell proliferation, and production of MMPs in RA synovial tissues. The expression level of several miRNAs in peripheral blood mononuclear cells correlates with RA disease activity. Recently, therapeutic trials aimed at targeting miRNA in vivo have been conducted. Targeting miRNA will enable a new advanced strategy toward arthritis treatment.