Atherosclerosis. Regression in nonhuman primates.

RESULTS of Anitschkow's early experiments (1927) suggesting that arterial lesions induced in rabbits by high cholesterol diets decrease in size and in fat content after cessation of cholesterol feeding have been confirmed in numerous species of animals, including rabbits, chickens, dogs, pigeons, pigs, and nonhuman primates (see references in Malinow, in press).This review deals with the studies performed in monkeys, their relevance to human atherosclerosis, and possible mechanisms of the observed arterial changes. Definition of Regression of AtherosclerosisIn this paper, regression indicates anatomical changes observed in the arteries of monkeys after a drastic redution in marked hypercholesterolemia induced by diet.At the microscopic level, regression includes (1) restored integrity of the endothelium lining the plaques; (2) arrest of intimal cell proliferation; and (3) a decrease in the number of cells, in the amount of intracellular and interstitial lipid, and in the extent of necrotic and calcific foci in the plaques (see below for references).Shrinkage of the lesions increases the lumen diameter previously narrowed by atheromatous plaques, but there is residual fibrosis in the regressed plaques, an indication of more collagen in the regressed arteries than in normal ones.Knowledge about the regression of experimental atherosclerosis needs to be expanded through studies directed at intramural hemorrhage and luminal thrombosis, since these processes are associated with ischemic episodes in