What do microRNAs mean for rheumatoid arthritis?

MicroRNAs (miRNAs) are small noncoding RNA molecules that modulate the expression of multiple protein-encoding genes at the posttranscription level. They likely participate in nearly every developmental and physiologic process. Although the function of most mammalian miRNAs has yet to be determined, it appears that their aberrant expression may play a role in the pathogenesis of several pathologic conditions, including immune-mediated inflammatory disorders. Over the past 3 years, dysregulated expression of a dozen miRNAs has been reported in patients with rheumatoid arthritis (RA), in both the circulation and inflamed synovium; however, the pathogenic role of only a few of these has been investigated in experimental mouse models. Here, we provide an overview of the current understanding of miRNA biogenesis and of the activities identified for the miRNAs shown to be dysregulated in RA. We also discuss potential benefits to patients and clinicians, including identification of novel and much-required molecular biomarkers of RA, as well as the possible development of miRNA-based biologic agents.