Human rheumatoid synovial cells (HRSC) in culture express TGF-beta receptors and are growth stimulated by the factor.

TGF-beta (5 ng/ml) increased the proliferation rate of HRSC by 30% after 96 h of treatment. One type of TGF-beta binding system, with apparent Kd of 953 pM and a number of 29,400 receptors/cell, was detected by Scatchard analysis of [125I]-TGF-beta binding. However, crosslinking experiments and SDS-PAGE separation showed five TGF-beta binding proteins: 50, 70, 110, 140 and 400 kDa. We may suggest that the affinities of these receptors are too close to be revealed by Scatchard plot. All together, the data suggest that TGF-beta plays a role in the hyperplasia of RA synovial tissue.