Role of endothelial injury and platelets in atherogenesis.

Endothelial cell injury is usually followed by the adherence and activation of platelets to exposed subendothelial surfaces. This is then followed by intimal smooth muscle cell proliferation and formation of connective tissue matrix by the smooth muscle cells through synthesis and secretion of collagen, elastic fiber proteins, and proteoglycans, and intracellular and extracellular lipid accumulation. Platelet activation is associated with morphological transformations which lead eventually to the "release reaction". A mitogenic factor has been recently recognized among the substances released from platelets and it may play a crucial role in promoting the intimal proliferation of smooth muscle cells which characterize atherosclerotic plaques.