Effects Of Fibrin, Fibrinogen And Fibrin(-Ogen) Degradation Products On The Growth Of Aortic Smooth Muscle Cells In Culture

Abstract

Importance of smooth muscle cell proliferation has been emphasized as a key event in atherogenesis. A number of factors have been shown to stimulate cell proliferation in vitro. These include platelet, lipoprotein, insulin and so on. We studied the effects of fibrin, fibrinogen and fibrinogen degradation products on the growth of aortic smooth muscle cells in culture. Smooth muscle cells in the 7th-15th subculture were grown from the explants of the media of rabbit thoracic aortas.Growth behavior of the cultured smooth muscle cells in response to fibrin clot was observed with phase-contrast microscope. Fibrin clot stimulated the cell proliferation during the period of 24 hours cultivation.Effects of fibrin,fibrinogen and fibrinogen degradation products on the incorporation of [3H] thymidine by the cultured smooth muscle cells were studied in replicate culture method. Both fibrin and fibrinogen stimulated the incorporation of [3H] thymidine during the period of 24 hours cultivation. But they inhibited the incorporation after 48 hours, and smooth muscle cells were degenerated and detached from the tissue culture dish. Fibrinogen degradation products inhibited the incorporation of [3H] thymidine by smooth muscle cells.The cultured smooth muscle cells showed fibrinolytic activity by Todd’s fibrinolysis autography.These results suggest that both fibrin and fibrinogen have the stimulatory effect, while fibrinogen degradation products have the inhibitory effect on the proliferation of smooth muscle cells, and that fibrinolytic activity of arterial wall might play a role in smooth muscle cell proliferation that leads to the development of atherosclerotic lesions.