Identification of non-denuding endothelial injury by scanning electron microscopy

Endothelial injury is important in the development of arterial disease. To examine the response to endothelial injury it is necessary to recognise if endothelium has been altered and how this relates to normal function. Of the several methods available to evaluate endothelial integrity, ultrastructural examination has certain advantages. In particular, scanning electron microscopy of the endothelium will permit large areas to be examined, and changes can be related to the overall anatomy of the vessel. There is good evidence that endothelial injury does not inevitably result in endothelial cell loss and denudation of the subendothelium, but that endothelial cells can be desquamated in a process of non-denuding injury. The morphological changes described in endothelial cells stimulated by a variety of agents suggest that the response varies according to the method of investigation, that there are some common features, but that each stimulus induces certain specific changes. The endothelial response to a range of agents was therefore examined in the same animal model, using carefully controlled preparation parameters. The observations indicate that the response to stimuli which induce an inflammatory type of reaction is characterised by fibrin formation and white cell adhesion. In contrast stimuli which result in vessel collapse show protruding cells and damage at vessel orifices. Certain features are seen irrespective of the stimulus. The significance of many of the observed changes remains to be elucidated.