Cells and Materials


Cellular reactions associated with the formation of lesions generated in the carotid artery of rabbits fed either normal or high cholesterol diets by the placement of a flexible, silastic collar around the artery, were studied by electron microscopy.

Endothelial cells remained as a monolayer throughout lesion development. The endothelial cell surface in both experimental and sham operated carotids, 4 hours and 8 hours after the initiation of the experiments, were covered with platelets and leukocytes. Neutrophils were present until 7 days in the arteries from within the collar of animals maintained on a normal diet, but only to 1 day in the cholesterol-fed animals. Neutrophils were observed within the medial layer. Few monocytes were identified. An intimal lesion had formed after 7 days in both groups of animals. Macrophage-like cells and foam cells were identified in the cholesterol-fed animals. The size of the lesion increased up to 56 days in animals maintained on a high cholesterol diet, but regression occurred after the 14-days sample in those animals on a normal diet. Concurrently a proportion of the smooth muscle cells changed from contractile to synthetic phenotype within the intimal and medial region of the collared artery of both high cholesterol and normocholesterolaemic animals. Lesions did not form in the contralateral, sham operated arteries.