The Dynamics of Circulating Monocyte Subsets and Intra-Plaque Proliferating Macrophages during the Development of Atherosclerosis in ApoE-/- Mice

Abstract

To detect the development of monocytes and proliferative macrophages in atherosclerosis of ApoE^-/- mice, we randomly assigned 84 ApoE^-/- mice fed western diet or chow diet. On weeks 2, 4, 6, 8, 10, and 12 after fed high-fat diet or normal chow diet, animals were euthanized (n = 7 for each group at each time point). Flow cytometry methods were used to analyze the proportions of circulation monocyte subsets. The macrophage and proliferative macrophage accumulation within atherosclerotic plaques was estimated by confocal florescence microscopy. Plasma levels of total cholesterol and triglyceride were measured by ELISA kit. The plaques of aortic sinus were stained with Oil Red O. The percent of Ly6C^hi circulation monocyte, the density of proliferation macrophage, the total plasma cholesterol and triglyceride levels, the lesion area of ApoE^-/- mice were consistently elevated in chow diet throughout the trial. The total plasma cholesterol and triglyceride levels, the lesion area were elevated in western diet group with age, and they were always higher than the chow diet group. The Ly6C^hi monocytes and proliferative macrophages reached a plateau at 8 weeks and 6 weeks; despite continued high-triglyceride high-cholesterol diet the percent did not significantly change. Interestingly, the density of macrophage did not change significantly over age in western and chow diet groups. Our results provide a dynamic view of Ly6C^hi monocyte subset, the density of macrophage and proliferation macrophage change during the development and progression of atherosclerosis, which is relevant for designing new treatment strategies targeting mononuclear phagocytes in this model.

Keywords: Cardiovascular disease; Hyperlipidemia; Inflammation.