Interleukin 1: a regulator of chondrocyte proliferation

Human interleukin 1 beta (IL-1 beta), at low concentrations (0.3-1 ng/ml), decreased by 95% the efficiency of colony formation in soft agar by rabbit articular chondrocytes. Furthermore, interleukin 1 (IL-1) suppressed by 50-60% the incorporation of 3H]thymidine into DNA in high density chondrocyte cultures on plastic dishes in the presence of 10% serum or fibroblast growth factor, although it increased twofold this incorporation in 0.3% serum alone. This suggests that IL-1 directly inhibits mitogenic response of differentiated chondrocytes to growth factors. In contrast, IL-1 stimulated 3H]thymidine incorporation into DNA in rabbit fibroblasts in the presence of growth factors. The selective suppression of chondrocyte replication by IL-1 may play an important role in cartilage destruction associated with chronic inflammatory joint diseases.