CD34 and rheumatoid arthritis: A similar analysis of synovial tissue from RA and OA patients by single-cell technologies identified four fibroblast subpopulations: CD34+ sublining fibroblasts (termed SC-F1), human leukocyte antigen (HLA)-DRAhi sublining fibroblasts (SC-F2), Dickkopf WNT signalling pathway inhibitor 3 (DKK3+) sublining fibroblasts (SC-F3) and CD55+ lining fibroblasts (SC-F4) [19].