EXPRESSION OF CD44 IN NORMAL AND RHEUMATOID SYNOVIUM AND CULTURED SYNOVIAL FIBROBLASTS

Objective-To determine if expression of CD44, the principal receptor f or hyaluronan, was altered in rheumatoid (RA) synovium and cultured rh eumatoid synovial fibroblasts. Methods-Synovium was obtained from norm al adult human joints (n = 4) and from joints of patients with RA (n = 5). Specific monoclonal antibodies to CD44 were used in immunofluores cence of whole synovium and cultured synovial fibroblasts and in quant itative Western blotting and ELISA of CD44 in cultured synovial fibrob lasts. Results-CD44 was restricted to the lining layer in normal synov ium but present, in reduced concentrations, throughout rheumatoid syno vium. Cultured rheumatoid cells were 19% larger in area and showed far fewer and less extensive CD44-positive cytoplasmic extensions, togeth er with reduced staining intensity compared with normal. Quantitative Western blotting normalised for cell protein showed a 75% reduction (n ormal = 1754 (835), rheumatoid = 409 (84) mean (SD) arbitrary units) i n the amount of CD44 in rheumatoid cells compared with normal, and enz yme Linked immunosorbent assay (ELISA) of cultured cell monolayers nor malised for cell number indicated a 29% reduction (normal = 0.707 (0.1 10), rheumatoid = 0.504 (0.103), mean (SD) optical density at 405 nm). Conclusions-Rheumatoid synovial cells showed altered morphology and r educed CD44 expression compared with normal cells. CD44, by means of m odulated associations with the cytoskeleton, may be involved in cell s hape change.