Different Role of Macrophages and Vascular Smooth Muscle Cells in Atherosclerotic Lesions of Watanabe Heritable Hyperlipidemic (WHHL) Rabbit between Aorta and Coronary Artery

The WHHL rabbit is often used to investigate the pathogenesis of atherosclerosis. Here we elucidate differences in the pathogenesis of atherosclerosis in coronary arteries (CA) and aorta (AO) by comparing dynamic changes in the distribution of vascular smooth muscle cells (VSMCs), macrophages, collagen and extracellular deposit during atherosclerosis in WHHL rabbits. Sections of CA and AO were obtained at the early, transitional and advanced stages of atherosclerosis and stained with hematoxilin-eosin, elastica van Gieson, antibodies specific to the above components, antibody against proliferated cell nuclear antigen (PCNA) and TUNEL. The relative areas of VSMCs, macrophages, collagen fibers and lipid deposits were calculated. In the early-stage atherosclerosis, VSMCs were predominant in CA lesions, while macrophages were predominant in AO lesions. PCNA-positive VSMCs and macrophages were noted in early-stage atherosclerosis in CA and AO. Collagen type I, III-V fibers were present in early-stage lesions of the AO, while type VI increased in the deep layer during the progression of atherosclerosis. The proportion of apoptotic cells increased in CA and AO lesions with the progression in atherosclerosis. Our results showed differences in the distribution patterns of VSMCs and macrophages at various stages of atherosclerosis in CA and AO of WHHL rabbits.