Lining cell and intimal smooth muscle cell response and Evans blue staining in abdominal aorta of young swine after denudation by balloon catheter

Young male Yorkshire swine underwent denudation of the abdominal aorta by transfemoral intraarterial ballooning followed by the intravenous injection of Evans blue dye at intervals up to 28 days after ballooning. A small number of swine were also sacrificed 30 min after ballooning. Approximately half the swine were fed a hypercholesterolemic diet, while the others received a mash diet. Quantitation by light microscopy showed that ballooning had removed 99% of the endothelial cells and approximately 50% of the native intimal smooth muscle cells. Three hours after ballooning, the entire luminal surface of the abdominal aorta was stained with Evans blue. By 3 days, a continuous cellular lining had been reformed over at least one-fifth of the denuded surface and the area stained with Evans blue had sharply decreased. The number of intimal smooth muscle cells had returned to nearly normal values, and continued to increase steadily from that day onward. By 8 days, the continuous lining cells had further increased in number and most could be identified as endothelial cells by electron microscopy. Proliferation of the intimal smooth muscle cells and endothelial cells appeared independent, and not influenced by each other. From 8 to 28 days, the percentage of reendothelialized aortic surface increased and Evans blue staining decreased so that by 28 days, values for both were close to those in nonballooned controls. The rate of return of endothelial cells with consequent decrease in Evans blue staining did not appear to be influenced by the hypercholesterolemic diet in any consistent manner. However, at Day 28, the number of intimal smooth muscle cells was approximately four times greater in the hypercholesterolemic group than in the mash-fed and ballooned group. Thirty minutes postballooning, layers of platelets covering most of the surface were adherent to the denuded abdominal aorta. By 3 hr, they were found only as scattered clumps and became even scarcer at later times. If adherent platelets were a factor in the intimal smooth muscle cell proliferation, they appear to have been operative only in the immediate postballooing period.