THY1 and rheumatoid arthritis: Further research shows that, FAPα+THY1+ fibroblasts mediate synovial inflammation by secreting cytokines and chemokines, while FAPα+THY1− plays a role in bone destruction by expressing osteoclast activity inducers consisting of matrix metalloproteinases, suggesting that synovial fibroblasts at different anatomical positions play different roles in the pathogenesis of RA.