KINETICS OF CELLULAR PROLIFERATION AFTER ARTERIAL INJURY .1. SMOOTH-MUSCLE GROWTH IN THE ABSENCE OF ENDOTHELIUM

Abstract

Intimal smooth muscle (SMC) proliferation was examined in the rat left carotid in regions lacking endothelium for prolonged periods of time. Arteries of animals injected with 3H thymidine and Evans blue were examined at intervals between 0 and 12 wk. The endothelial layers was regenerated from the ends of the denuded segment but failed to cover the central 3rd of the artery by 12 wk. Autoradiography on samples from this central region (stained blue) and the endothelialized ends (white) showed that SMC proliferation reached a maximum at 48 h in the media (46%) and at 96 h in the intima (73%). Subsequently, the thymidine index declined to baseline (0.06%) by 4 wk throughout the media and by 8 wk in the intima covered by endothelium. SMC proliferation persisted at a high level (3.8%) at the surface of the intima lacking endothelium even at 12 wk. Despite continued proliferation of luminal SMC, total arterial SMC number was the same at 2 and 12 wk. Intimal SMC proliferation after arterial injury apparently is an acute event related to the initial injury process. Persistent proliferation of luminal SMC does not result in an increase in intimal cell number.