A novel simple technique for en face endothelial observations using water-soluble media -'thinned-wall' preparations.

A new, easily applicable technique providing en face preparations for light microscopy observations of the rat aorta and human thin wall arteries is described here. The major steps of the technique include attachment of the fixed and flattened vessel with the endothelium face down on a glass slide, covered with a water-soluble adhesive medium; drying and softening the vessel wall with another water-soluble medium; removal of the adventitia and most of the media; detaching the layer by placing the glass slide in water; and final attachment of the layer with the endothelium upwards. On such 'thinned-wall' preparations, 40-50 microm in thickness, the stained endothelial cells are clearly visible. Because of the preparation thickness and the use of water-soluble media during the preparation, some subendothelial lipid accumulations, characteristic of the early stages of atherosclerosis process, are well preserved.