FSTL1 and rheumatoid arthritis: The authors also reported that FSTL1 directly increases the expression of pro‐inflammatory cytokines, such as interleukin (IL)‐6 and MCP‐1.10 A recent study revealed that human recombinant FSTL1 increased the expression of MMP1, MMP3 and MMP1 via the NF‐κB and mitogen‐activated protein kinase (MAPK) signalling pathway in fibroblast‐like synoviocytes.14 Taken together, these results suggest that FSTL1 accelerates RA progression by stimulating inflammation and catabolism.