Elevated serum levels of Interleukin-37 are associated with inflammatory cytokines and disease activity in rheumatoid arthritis.

Interleukin-37 (IL-37) is closely associated with several inflammatory diseases. However, the role of IL-37 in the pathogenesis of rheumatoid arthritis (RA) remains unclear. The aim of this study was to assess the associations between serum levels of IL-37 and disease activity, inflammatory cytokines, and bone loss in patients with RA. Serum cytokines levels were examined by Enzyme-linked immunosorbent assay (ELISA). Radiographic bone erosion was assessed using the van der Heijde-modified Sharp score and bone mineral density (BMD) was measured using DXA. Serum IL-37 levels in RA patients were significantly higher than those in HCs (p < 0.001), and were significantly positively correlated with clinical parameters of disease activity and serum levels of IL-17 and IL-23. In addition, serum IL-37 levels were significantly higher in patients with stage IV of radiographic bone erosion than those with stage III and stage I-II, and they were significantly higher in those with osteopenia and osteoporosis than in those with normal BMD. Our results suggest that serum IL-37 levels were increased in patients with RA and were positively associated with disease activity, IL-17/IL-23 and bone loss in RA, suggesting that IL-37 may play a critical role in the pathogenesis of RA.