Prevention of neointimal formation by a serine protease inhibitor, FUT- 175, after carotid balloon injury in rats

Background and Purpose - In vivo and vitro studies revealed the activation of thrombin and the complement system in vascular lesion formation during the process of atherosclerosis, along with pathological proliferation of smooth muscle cells. We examined the effect of the synthetic serine protease inhibitor FUT-175 (developed as a potent inhibitor of thrombin and the complement system) on vascular lesions using balloon dilatation-induced neointimal formation in the carotid artery of rats. Methods - Sprague-Dawley (SD) rats underwent balloon dilatation injury of the left carotid artery to induce neointimal formation. Three groups of these rats (n = 8, each) were treated with daily intraperitoneal injections of 1 of the following doses of FUT-175: 0.5, 1.0, or 2.0 mg/d in 1 mL of saline for 7 consecutive days. The control group (n=8) was similarly treated with 1 mL of saline for 7 days. The injections were started immediately after balloon injury. Two weeks after the injury, the left carotid arteries were perfusion-fixed, and the areas of the neointimal and medial layer were analyzed under a microscope. Results - A morphometric analysis revealed that there were significant differences in the intima-media ratio between the 4 groups treated with vehicle (saline) or a low, medium, or high dose of FUT-175 (1.45±0.11, 1.08±0.06, 0.71±0.04, or 0.32±0.04, respectively). This suppression was achieved in a dose-dependent manner by the administration of FUT-175 after balloon injury. In the histological study, it was demonstrated that FUT-175 suppresses the production of platelet-derived growth factor (PDGF)-BB in the neointima and the medial smooth muscle cell layer. Conclusions - After balloon injury activated proteases that were inhibited by FUT-175 were demonstrated to have an essential role in the development of the pathological thickening of the arterial wall.