Apolipoprotein B localization in coronary atherosclerotic plaques from cynomolgus monkeys

The presence of apolipoprotein B (apo B) was determined in atherosclerotic lesions of coronary arteries from cynomolgus monkeys placed on a hypercholesterolemic diet for one year. Immunofluorescence techniques were applied to sections of arteries that were fixed by perfusion with formalin and embedded in paraffin. Segments of right coronary, left anterior descending, and left circumflex arteries were observed. All segments demonstrated substantial intimal thickening, accompanied by areas of necrosis at the base of the plaque, usually located on the luminal side of the internal elastic lamina. Large clusters of foam cells could be found at the base of such plaques, between intimal smooth muscle cells in the fibromuscular cap, and frequently in the tunica media in regions of necrosis. Immunofluorescence depicting apo B was usually confined to the intima, especially in the necrotic core, but could also be seen in the media in regions in which the internal elastic lamina was missing. Apo B often filled the extracellular space between smooth muscle cells and groups of foam cells but was not identified in the cytoplasm of intact cells. Apo B-positive areas were usually also positive for alcian blue staining, suggesting LDL-sulfated glycosaminoglycan coexistence at such sites. The localization pattern of apo B in lesioned coronary arteries from cynomolgus monkeys was consistent with that found in human coronary lesions, suggesting that diet-induced hypercholesterolemia in such monkeys may be a valid model for studying the role of LDL in human atherogenesis.