Inhibition of endothelial cell regrowth. Cessation of aortic endothelial cell replication after balloon catheter denudation.

Aortas of male rabbits (2.0 to 2.5 kg body weight) were denuded of endothelium with a 4F balloon catheter and killed 7, 14, 60, 90, and 180 days later. Aortic endothelial cells regrowth was determined using Evans blue dye and scanning electron microscopy. Early endothelial outgrowth was rapid, but by 14 days the regrowth slowed markedly so that no further increase of endothelial outgrowth was detected at other time periods. Another group of animals received 3H-thymidine 1 hour before death and were killed 4, 14, and 42 days later. The endothelial cells replication in the aortas of these animals was measured from Häutchen preparations. Endothelial cells replication was observed 4 days after balloon injury but was markedly reduced by 14 and 42 days. Intimal smooth muscle cell replication, however, was observed at both these later times. These result demonstrate that in vivo endothelial cells replication stops long before the aorta is repopulated and suggest that some mechanism other than contact between endothelial cells can prevent endothelial cell replication.