Studies have proven that HDAC1 participates in producing pro-inflammatory factors, and the elimination of HDAC1 in T cells has a protective function on mice with collagen arthritis.298 HDAC inhibitors can inhibit the activation of FLS, and the HDAC1 and HDAC2 expression in RA synovial fibroblasts (RA-SF) is higher than that in OA synovial fibroblasts (OASF).299. This evidence concerns the gene HDAC9 and rheumatoid arthritis.