Studies of hypercholesterolemia in the nonhuman primate. II. Fatty streak conversion to fibrous plaque.

Abstract

This report presents the second portion of the morphologic studies on chronic, diet-induced hypercholesterolemia in nonhuman primates (Macaca nemestrina) examined sequentially between 5 and 13 months. A direct relationship was observed between the rate of cholesterol increase, the level and duration of hypercholesterolemia, and the changes in the artery wall that led to the formation of fatty streaks and their conversion to fibrous plaques. A loss of endothelial continuity was first observed in the iliac arteries between 3 and 4 months of atherogenic diet and appears to be a critical step in the conversion of many fatty streaks to fibrous plaques. With breaks in endothelial junctions and exposure of some of the macrophages in a fatty streak, many of the lipid-filled macrophages appeared to detach and enter the circulation. The number of circulating foam cells increased precipitously between 3 and 4 months, the time when increased sites of endothelial dysjunction and macrophage egress were observed. Exposu...