Lack of intimal hyperplasia response in an experimental model of non-endothelial vascular wall damage.

The endothelial and medial layers are generally presumed to play an important role in the appearance and development of intimal hyperplasia. We have carried out a short-, media- and long-term study of the morphological changes taking place in the common iliac artery of rats after surgical removal of the adventitial layer. Our aim has been to assess the likely role played by this layer in the development of intimal hyperplasia. Our results show recurrent periods of cellular desquamation and almost complete absence of hyperplastic response during the first two months. After three months three is a slow process of endothelialization which is completed by the 6th month and persists one year after adventitial resection. Thus, adventitial resection seems to cause instability at the subendothelial bed level, not allowing the junction and embedding of endothelial cells nor the development of intimal hyperplasia. This lack of hyperplasia might also result from the fact that the endothelial desquamation process does not involve cellular rupture, which would prevent mitogenic-factor release. After morphological repair of the endothelium, a slow morphofunctional recovery of the artery takes place.