Tissue factor regulation in vascular smooth muscle: a summary of studies performed using in vivo and in vitro models

In response to vascular injury, such as occurs in acute or chronic atherosclerosis, vascular smooth muscle cells (VSMCs) proliferate and migrate, ultimately contributing to vessel narrowing. Several growth agonists, including platelet-derived growth factor and fibroblast growth factor, are known to cause VSMCs to proliferate and are believed to be present at sites of vessel injury. Targets for inhibiting VSMC growth or migration in the presence of multiple growth agonists include genes that are induced in common by VSMC growth factors. This article summarizes the in vivo and in vitro findings of experiments designed to investigate the regulation of tissue factor in VSMCs in 2 animal models. The findings demonstrate that tissue factor is rapidly induced by growth factors in VSMC culture and by balloon injury in aortic media, and they suggest that VSMCs may play a major role in mediating the early thrombotic response. Strategies designed to inhibit the response of VSMCs to growth agonists may therefore have important implications for the treatment of intravascular thrombosis.