Proliferation of synovial lining cells and fibroblasts.

After in vitro incubation with 3H-thymidine, the proliferation of synovial lining cells and fibroblasts was investigated in surgically-removed articular tissue. Under normal conditions, in nonrheumatoid arthritis and in osteoarthrosis, low proliferation rates for both cell types were observed. In rheumatoid arthritis, the rate of proliferation of both cell types was usually increased. An increased proliferation of the synovial lining cells was especially observed in cases with a hyperplastic lining cell layer and in cases with a minimal lymphocytic and plasma cellular infiltration in the synovial membrane.