Fig. 3

TRAP and cathepsin K enzyme activity in synovium from OA and RA patients. a and b. Representative synovial TRAP-positive and TRAP-negative MGCs both in inflamed OAI (a) and RA (b) cases. c. Cathepsin K-immunoreactive MGC localized to synovial pannus adjacent to bone surface in RA and OA tibial plateaux. d and e. Cathepsin K-immunoreactive mononuclear synovial lining (d) and sublining (e) cells in OAI and in RA synovium. Filled arrows indicate TRAP-positive or cathepsin K-positive cells. Open arrows indicate TRAP-negative MGCs. P = pannus and B = bone, scale bars = 50 μm