Regression of early cholesterol-induced aortic lesions in rhesus monkeys.

The reversibility of early uncomplicated cholesterol-induced aortic lesions in rhesus monkeys was investigated. Three groups of Rhesus monkeys were used: the control group was fed a chow diet for 8 weeks; the progression group was fed an atherogenic diet for 8 weeks and the regression group was fed an atherogenic diet for 8 weeks and returned to the chow diet for 16 weeks. The lesions produced in the progression animals characteristically contained many lipid-laden monocytes immediately beneath the endothelium, abundant lipid droplets in intimal smooth muscle cells and moderate amounts of lipid in the extracellular spaces. Lesions in regression animals contained few lipid-laden monocytes, less lipid in smooth muscle cells and larger and more numerous lipid particles in the extracellular spaces. The results indicate that aortic lesions can be produced predictably after 8 weeks of feeding a high-cholesterol diet and that qualitative changes in the lesions occur 16 weeks after withdrawal from the diet.