Endothelialized myointimal thickening in the rat aorta as a result of extensive freeze injury.

The regeneration of rat aorta intima and medial layer was examined after extensive freeze injury that caused the death of both endothelial and smooth muscle cells. After 1 month complete re-endothelialization of the denuded area was observed. In parallel, myointimal thickening was formed by the smooth muscle cells (SMC) from the uninjured edges and its thickness increased with time. The SMC of myointimal thickening were stellate in the upper part and elongated near the internal elastic lamina. No regenerative response was seen in the medial layer, consisting only of elastic and collagen fibers, and its thickness was reduced during regeneration. These results show that the regenerative response of medial SMC to extensive freeze injury proceeds in the form of intimal thickening.