Insulin-like growth factor-1 protects from vascular stenosis and accelerates re-endothelialization in a rat model of carotid artery injury

Background:  IGF-1 is a potent mitogen for vascular smooth muscle cells, but exerts protective effects on endothelial cells that may trigger antiatherogenic mechanisms. Objectives:  This study was designed to test the hypothesis that an IGF-1 excess following arterial injury prevents neointima formation and vascular stenosis. Methods:  Rats were subjected to carotid balloon injury and treated with IGF-1 (1.2 mg kg⁻¹ per die) or saline for 10 days. Results:  In IGF-1 treated animals, high tissue levels of eNOS, Akt and its phosphorylated form were found, confirming activation of IGF-1-dependent signaling pathways. IGF-1 markedly reduced neointima formation and post-injury arterial stenosis. IGF-1 exerted proliferative and anti-apoptotic effects in the media of injured carotids, but inhibited mitotic activity and induced apoptosis in the neointima. Furthermore, IGF-1 stimulated mobilization of progenitor endothelial cells and re-endothelialization of the injured arteries. L-NAME administration inhibited IGF-1 vasculoprotective effects. Conclusions:  IGF-1 attenuates post-injury carotid stenosis by exerting differential effects in the neointima and tunica media with regard to the key components of the response to injury. The data point to a novel role of IGF-1 as a potent vasculoprotective factor.