THY1 and rheumatoid arthritis: After short-term in vitro culture, ICAM1 was found by FACS analysis to be expressed in nearly all OA and RA FLS (Fig. 2a and b), while VCAM1 expression was much higher in OA FLS (~ 60.9%) than in RA FLS (~ 52.4%) (Fig. 2a and b), which was validated by the IHC staining for CD90, ICAM1 and VCAM1 in OA and RA synovial tissues (Fig. 2c).