Effect of vascular freezing on the histopathology of dissected small vessels in the rat: Vascular freezing does induce intimal hyperplasia in arteries and veins

Intimal hyperplasia is the primary response of a vessel wall after injury. It may be the single most significant factor affecting long-term patency, T he purpose of this study was to find out whether freeze injury, inflicted o n rat microvessels, would be followed by intimal hyperplasia, Toward this a im, we exposed the superficial femoral vessels in the rat. On one side they were frozen using liquid nitrogen spray. The other side was dissected as t he control. Vessel segments, harvested immediately and after 1, 2, 3, and 5 months, were studied light microscopically for the occurrence and content of intimal hyperplasia. In the arteries a considerable intimal hyperplasia was found within a LF-week interval, persisting for at least 5 months, as a result of the freeze injury. In the veins, the intimal hyperplasia was muc h less marked but was nevertheless demonstrable. These findings are not in agreement with earlier studies, in which freezing of injured rat microarter ies with liquid nitrogen spray was followed by complete regeneration of the vessel wall, without intimal hyperplasia taking place. The factors contrib uting to these differences are discussed. It is concluded that freezing of a vessel wall is followed by intimal hyperplasia, which is part of the norm al healing process. (C) 2000 Wiley-Liss, Inc.