Adventitial resection of small artery provokes endothelial loss and intimal hyperplasia

While adventitial resection is a part of the preparation of microvessels for operation, the procedure may provoke damage to the vessel wall. The histologic and ultrastructural endothelial lesions associated with adventitial resection, the interface of the blood vessel and the course of endothelial repair are discussed herein. The adventitia of the abdominal aorta of rats was stripped under microscopic magnification (32X) around the whole circumference of infrarenal segment of 1 centimeter in length. The rats were sequentially sacrificed. Fixation and silver staining were carried out in vivo. The specimens were collected at six, 12 and 24 hours, at seven, 15, 30 and 90 days, and at six, nine and 12 months after injury. These specimens were studied by en face light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results of en face light microscopy and SEM investigations showed: an initial severe trauma of the endothelial surface leading to complete de-endothelial areas as early as six hours after injury, the lesions were limited to the adventitial resected areas; at seven days the polygonal cells were recognized in silver stain preparation; at 30 days the endothelial surface was partially reconstituted but cells had large protoplasmic areas, TEM in the same time period confirm the absence of the endothelial cells up to 30 days; at 90 days the reconstitution of the endothelial layer was almost complete, and intimal hyperplasia was observed already at one month and appeared to have stabilized at six months postoperatively with three to four cell layers. These results suggest that: adventitial resection immediately provokes endothelial desquamation; endothelialization is a slow process when large areas are involved, and intimal hyperplasia may develop even on an autologous arterial segment, thus providing new insight to the etiopathogeny of vascular graft initial hyperplastic reactions.