Comparative study of the synovial histology in rheumatoid arthritis, spondyloarthropathy, and osteoarthritis: influence of disease duration and activity

Objectives-To compare the macroscopic and microscopic characteristics of sy novial tissue in rheumatoid arthritis (RA), spondyloarthropathy (SpA), and osteoarthritis (OA) after exclusion of possible biases induced by disease d uration or activity, or both. Methods-Synovial biopsy specimens were obtained by needle arthroscopy in pa tients with early RA (n=16), late RA (n=14), early SpA (n=23), and OA (n=12 ). Macroscopic and microscopic features were scored on a four point scale a nd analysed as a function of disease duration (early versus late RA), local and systemic disease activity, and diagnosis. Results-Except for the maximal synovial lining thickness, no significant di fferences were seen between early and late RA. For disease activity, synovi al histology was only weakly correlated with C reactive protein in RA, but seemed to be strongly dependent on effusion of the biopsied joint in all di sease groups. After stratification for local disease activity, no disease r elated differences were found in patients without joint effusion. In contra st, important differences were found between patients with RA. and SpA with active joint effusion. Synovial vascularity was macroscopically increased in SpA versus RA (p=0.017). A straight vessel pattern was only seen in RA, while tortuous vessels were preferentially seen in SpA. Vascularity was als o microscopically increased in SpA compared with RA (p=0.031), and correlat ed with the macroscopic vascularity (r(s)=0.36, p=0.036). CD3+ (p=0.008), C D4+ (p=0.008), and CD20+ (p=0.024) lymphocytes were overrepresented in RA c ompared with SpA. The integrin expression in RA. was characterised by a dec rease of alphaV beta3 in the synovial lining (p=0.006) and an increase of a lphaV beta5 in the sublining (p<0.001). Conclusions-The immune architecture of the synovial membrane is more depend ent on local disease activity than on disease duration. Synovium obtained f rom clinically affected joints shows important histological differences bet ween RA and SpA.