Endothelial injury in human atherosclerosis

A light and electron microscopic investigation (scanning and transmission electron microscopy) was performed on 51 human atherosclerotic carotid lesions. The purpose of this study was to establish whether features of endothelial injury such as those described in animals occur in man and whether these features can be related to specific stages of human atherosclerosis. Irrespective of their histological appearance the atherosclerotic lesions were covered with endothelium which showed non-specific changes in cell shape and size. However, all complicated lesions appeared denuded. Moreover, a peculiar interaction of endothelium with monocytes and lymphocytes as well as blood components (e.g., fibrin and lipoproteins) was observed in intimal thickenings, fatty streaks and uncomplicated plaques. The surface exposure of macrophage-derived foam cells was seen on florid fatty lesions. Large areas of the arterial surface lacking any endothelial coverage were characteristic of complicated plaques. They appeared to be a consequence of the arterial wall degeneration with an associated failure in endothelial repair.