Positive expression of pluripotency marker on osteoarthritis and rheumatoid arthritis induced pluripotent stem cells. (A) The expression of stemness genes in osteoarthritis (OA) induced pluripotent stem cells (iPSCs) and rheumatoid arthritis (RA) iPSCs was analyzed by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis. Total RNA of fibroblast, OA fibroblast-like synoviocytes (FLSs), RA FLSs, H7, OA iPSCs and RA iPSCs was isolated and analyzed for endogenous pluripotent genes by RT-PCR analysis. The expression of endogenous Nanog, Oct4, Sox2 and Rex is upregulated in OA iPSCs and RA iPSCs. OA FLS and RA FLS already expressed Klf4 before reprogramming process started. (B) Immunofluorescence staining against Nanog, Oct4, Sox2, Tra-1-80, Tra-1-60, and SSEA-4 in RA iPSCs. RA iPSCs expressed a high level of these markers. (C) Immunofluorescence staining against Nanog, Oct4, Sox2, Tra-1-80, Tra-1-60, and SSEA-4 in OA iPSCs. OA iPSCs were positive for the pluripotency genes such as Nanog, Oct4, Sox2, Tra-1-80, Tra-1-60, and SSEA-4.