Control of DNA synthesis in cultured vascular endothelial and smooth muscle cells--response to serum, platelet-deficient serum, lipid-free serum, insulin and oestrogens.

Endothelial and smooth muscle cell proliferation has an important role in the pathogenesis of atherosclerosis. To study the effect of serum and some of its putative growth factors on DNA synthesis, the incorporation of thymidine into DNA was studied in cultured human umbilical endothelial and rat aortic smooth muscle cells. DNA synthesis in endothelial cells was progressively stimulated by increasing concentrations of human serum, maximum stimulation occurring with 20% serum. Foetal calf serum had a much lesser effect on DNA synthesis in endothelial cells. Smooth muscle cells responded equally to human and foetal calf serum. Exposure to serum prepared to exclude the platelet-derived growth factor resulted in reduced DNA synthesis in smooth muscle cells. However, endothelial cells increased DNA synthesis in platelet-poor serum. Serum from which lipid had been extracted stimulated DNA synthesis less well than whole serum in both endothelial and smooth muscle cells. Insulin stimulated DNA synthesis in smooth muscle cells but not in endothelial cells, while ethinylestradiol, estrone and estriol had no effect on DNA synthesis in either type of cell. Thus cultured endothelial and smooth muscle cells differ in their requirements for human serum and in their response to platelet factor and to insulin.