Local Proliferation of Fibroblast‐Like Synoviocytes Contributes to Synovial Hyperplasia

Objective. To test the hypothesis that local proliferation contributes significantly to the hyperplasia of rheumatoid synovium. Methods. Immunohistologic and chemical staining was used to identify 3 markers of cell proliferation: proliferating cell nuclear antigen, c‐myc proto‐oncogene, and nucleolar organizer regions. Synovium from 21 patients with rheumatoid arthritis, 34 with degenerative joint disease, and 7 with joint trauma was examined. Results. All 3 markers indicated substantial, active proliferation of synovial lining cells in synovium with hyperplasia. Proliferating cells showed type I procollagen immunoreactivity but were negative for CD68, a monocyte/macrophage marker. Proliferation was greater in rheumatoid arthritis than in the other conditions evaluated. Conclusion. In situ proliferation of fibroblast‐like synoviocytes in the synovium lining contributes considerably to the increase in cell numbers in rheumatoid synovium.