Endothelial function in thrombosis and thrombolysis

The localization of tissue factor (TF) in atherosclerotic plaques of human aortas was immunohistochemically examined using rabbit anti-IgG against recombinant TF, which was expressed in E. coli. TF, the initiator of the extrinsic coagulation pathway, was ubiquitously present in atherosclerotic intima, and was expressed mainly by macrophages, but not by endothelial cells. It has been suggested that some macrophages in atherosclerotic intima co-express both molecules of TF and platelet-derived growth factor-B chain. We have developed a morphometrically quantitative in vitro assay for angiogenesis, using endothelial cultures on collagen gel incorporating plasminogen. With this method, we have obtained findings suggesting that plasminogen and plasminogen activators (PAs), especially urokinase-type PA (uPA) derived from endothelial cells, enhance angiogenic activity, probably by increasing endothelial migration. uPA was immunohistochemically observed to be primarily cell-associated on the focal contract areas, probably via its receptors on endothelial cells. These findings may support the hypothesis that the activation and regulation of the pericellular fibrinolysis system is closely related to angiogenesis.