Endothelial regeneration. VIII. Interaction of smooth muscle cells with endothelial regrowth.

This study examined the ability of arterial endothelial cells to repopulate arterial grafts which were devoid of luminal smooth muscle cells and in arterial grafts which had an established pseudoendothelium comprised of smooth muscle cells. These studies were designed to explore the hypothesis that smooth muscle cells when forming a pseudoendothelium can retard endothelial cell regrowth. Segments of denuded glutaraldehyde-fixed carotid arteries and of viable autologous carotid arteries with a pseudoendothelium of smooth muscle cells were implanted end to end into the rabbit carotid arteries and left for 6 or 12 weeks. Endothelial outgrowth onto these arterial grafts was extremely limited (approximately 3 mm) regardless of the preparation and was equal to that observed in a carotid artery denuded of endothelium with a balloon catheter. Endothelial cell replication was significantly elevated in these implanted carotid segments at all times studied with the majority of the replicating cells not located at the leading edge of endothelium. The location of these cells suggests this replication was not associated with regrowth. Finally, the ability of denuded arteries to support endothelial cell adherence was tested in vitro by plating [3H]thymidine bovine endothelial cells on segments of excised arteries which had been denuded of endothelium for 2 and 12 weeks. No difference in plating efficiency was observed. These studies suggest that the presence of smooth muscle cells on the luminal surface of denuded arteries was not responsible for the cessation of endothelial regrowth.