Kinetics of cellular proliferation after arterial injury. III. Endothelial and smooth muscle growth in chronically denuded vessels.

The healing of injured rat carotid chronically denuded of endothelium was studied at late times after balloon injury. One year after injury the endothelial layer was not fully regenerated and had ceased proliferating. The denuded areas of these vessels were covered with luminal smooth muscle cells which strongly resembled endothelium but did not stain with factor VIII.R.Ag antibody. These cells were actively proliferating and formed a surface which was weakly thrombogenic. Indium-111 platelet studies showed that over 24 hours there was a slight but significant adherence of platelets to the denuded surface. Luminal smooth muscle cell proliferation was matched by cell loss and did not produce further intimal thickening or an increase in total cell number. These results demonstrate that damaged conduit arteries can exist in a stable state without endothelium and do not develop thrombosis even after prolonged periods of time.