Endothelial regeneration. VII. Lack of intimal proliferation after defined injury to rat aorta.

Rat aortas were denuded of endothelium by the use of catheters, which removed either a zone 10-15 cells wide or a zone 90-120 cells wide. Each animal received 3H-thymidine at 1, 16, and 24 hours before death, and groups of 3 animals were killed at 2, 3, 4, and 7 days after the small injury or 4, 5, 7, 14, and 42 days after the large injury. Scanning electron microscopy showed that the smaller injury was rehealed with endothelium by approximately 72 hours, and the large injury was repopulated by endothelium after 7-8 days. In aortas subjected to the 10-15-cell-wide injury, no intimal thickening nor intimal smooth-muscle proliferation was observed. After the larger injury, no obvious intimal thickening was present, although a few intimal cells were observed at sites where the internal elastic lamella was discontinuous. No significant increase in smooth-muscle-cell replication was detected in these aortas at any time after injury.