MiR-146a levels in rheumatoid arthritis and their correlation with disease activity: a meta-analysis

Objective: To evaluate the relationship between miR-146a levels and rheumatoid arthritis (RA), and the correlation with RA activity. Methods: For the meta-analysis, we searched the PubMed, MEDLINE, EMBASE and Cochrane databases, comparing miR-146a levels in patients with RA and controls, and correlation coefficients between miR-146a levels and Disease Activity Score for 28 joints (DAS28) and erythrocyte sedimentation rate (ESR) in patients with RA. Results: Fourteen studies, totaling 683 patients with RA and 477 controls, were available. miR-146a levels were significantly higher in the RA group than in the control group (standardized mean difference [SMD] = 0.546, 95% CI = 0.033–1.059, P = 0.037). Stratification by adjustment for age and/or sex revealed significantly higher miR-146a levels in the adjusted, but not in the non-adjusted group (SMD = 0.747, 95% CI = 0.094–1.400, P = 0.025; SMD = 0.431, 95% CI = −0.430–1.291, P = 0.326, respectively). Stratification by sample size showed significantly higher miR-146a levels in RA groups of large sample sizes (N ≥ 50), but not in those of small size. miR-146a levels in synovial tissue/fluid were significantly higher in the RA group than in the OA group (SMD = 1.305, 95% CI = 1010–1.639, P < 0.001). A significant positive correlation was found between miR-146a levels and ESR (correlation coefficient = 0.534, 95% CI = 0.029–0.822, P = 0.039). Conclusions: Circulating and synovial tissue/fluid miR-146a levels are high in patients with RA, and circulating miR-146a levels positively correlate with ESR.