There is some experimental evidence that patients with rheumatoid arthritis (RA) have a defect in the control of cellular proliferation. To examine this further, synovial cells from patients with RA and osteoarthritis controls (OA) were studied for phenotypic characteristics of transformation and proliferation.
Synovial cells grown in vitro were studied to determine the extent of proliferation, anchorage-independent growth, growth under reduced serum conditions, fibronectin secretion, and the presence of cell proliferation antigens.
RA synovial cell proliferation was less than that recorded for normal skin fibroblasts and was not increased compared to OA synovial cells. Studies of growth in soft agarose showed no colony formation by RA or OA synovial cells after 28 days, indicating that anchorage-independent growth does not occur. At low serum concentrations RA and OA synovial cells showed similar growth. Fibronectin was constant for each cell line studied, irrespective of the cell number or diagnosis. RA cells did not show an increased rate of fibronectin secretion. RA cells did not show an increased expression of proliferating cell antigens.
These studies do not support the concept that defective proliferation of synovial cells is a major factor in the pathogenesis of RA.