The Effects of Endothelin-1 on Collagen Type I and Type III Synthesis in Cultured Porcine Coronary Artery Vascular Smooth Muscle Cells

Abstract

Restenosis is the single most important factor limiting a favorable long-term outcome following mechanical revascularization. The vascular endothelium, through the release of key regulatory compounds, may regulate vascular structure by exerting fundamental control over collagen synthesis following injury to the vessel wall. We tested the hypothesis that endothelin (ET-1), an endothelium-derived peptide previously shown to be increased in pathological states, differentially stimulates porcine coronary vascular smooth muscle cell collagen types I and III synthesis. Monocultures of porcine coronary vascular smooth muscle were exposed to varying concentrations of endothelin over a 24 –96-h time period. The medium was assayed for soluble collagen types I and III using a sensitive and specific ELISA method. Experiments were also done with the ET-1 antagonists PD 145065 and BQ123. Cell counts and viability were serially monitored. Experiments were also conducted with angiotensin II (A-II). A-II and ET-1 stimulated cell proliferation. ET-1 maximally stimulated collagen type I synthesis at 48 h at an optimal concentration of 10⁻⁸m, with no significant stimulation of collagen type III synthesis. The ET_Aspecific antagonist BQ123 significantly inhibited the stimulatory effects of ET-1. A-II also stimulated collagen type I synthesis above basal levels, but was less efficacious than endothelin (95 ±5 %, A-II,v189 ±14 % ET-1). In contrast to ET-1, A-II stimulated collagen type III synthesis (31 ±6 % above basal, compared to −4 ±5 % for ET-1). Results are also reported using smooth muscle cells from porcine aorta. The data demonstrate that ET-1 and A-II stimulate collagen synthesis by coronary artery vascular smooth muscle, and that they exert a differential effect over the two types of collagen that are present in the intima following balloon injury. Thus, the over expression of key regulatory compounds by endothelium following balloon injury could enhance collagen deposition and, consequently, play an integral role in intimal hyperplasia and restenosis.