Hirulog-1 reduces expression of platelet-derived growth factor in neointima of rat carotid artery induced by balloon catheter injury

Vascular restenosis is one of the major concerns for the treatment of atherosclerotic cardiovascular diseases using therapeutic vascular procedures. Hirulog-1, a synthetic thrombin inhibitor, effectively reduced ischemic events in coronary heart disease patients and caused less hemorrhagic complications compared to heparin. Thrombin stimulated the expression of platelet-derived growth factor (PDGF) in vascular cells. PDGF receptor blockers reduced angioplasty-induced restenosis in the swine model. The present study examined the effects of hirulog-1 on vascular stenosis, platelet deposition and the expression of PDGF in rat carotid arteries injured by balloon catheter. Multiple intravenous infusions of hirulog-1 (1 mg/kg/h for 4 h for 6 times), but not bolus injection or 1-2 times of infusion, reduced neointima/media ratio by 50% in balloon-injured carotid arteries compared to injured animals receiving saline alone. Activated partial thromboplastin time in hirulog-1-treated rats was significantly prolonged compared to saline controls but shorter than that in animals receiving heparin (50 U/kg/h). One of heparin-treated rat, but none of hirulog-1-treated, died from bleeding complication. Hirulog-1 injection transiently reduced platelet deposition on denuded intima visualized by scanning electron microscopy. Abundance of PDGF in neointima of injured carotid arteries detected by immunohistochemistry was significantly decreased following infusions of hirulog-1. The results suggest that balloon catheter injury induced neointima formation and the overexpression of PDGF in the neointima of rat carotid artery may be effectively suppressed by infusions with hirulog-1, a thrombin-specific inhibitor.