Effects of colony-stimulating factors on proliferation and activation of synovial cells

Joint synovium of patients with rheumatoid arthritis plays an important role in initiation and progress of joint diseases. Proliferation and activation of synovial cells, including macrophages, are modulated by various cytokines and arachidoic acid metabolites. Two kinds of cytokines; granulocyte/macrophage colony-stimulating factors (GM-CSF), and monocyte/macrophage colony-stimulating factor (M-CSF) induce the proliferation or activation of monocyte/macrophages, and their progenitor cells or other stromal cells in bone marrow. We investigated the effects of GM-CSF and M-CSF on synovial cells. GM-CSF stimulated the proliferation of synovial cells and its effect was enhanced by the presence of indomethacin, like that of a potent stimulator of synovial cells, interleukin-1 beta (IL-1 beta). But GM-CSF did not induce the production of IL-1 beta. M-CSF neither stimulated the proliferation of synovial cells nor induced production of IL-1 beta by synovial cells. It was suggested that GM-CSF played some role in the proliferation of synovial cells of the joints.