POU5F1 and rheumatoid arthritis: Fibroblast-like synoviocytes (FLSs) of patients with RA (n = 3) and osteoarthritis (OA) (n = 3) and dermal fibroblasts of healthy subjects (n = 3) were efficiently reprogrammed by lentiviral transduction of oct4, sox2, nanog and c-myc (Fig. 1a).