Quantitation of atherosclerosis in murine models: correlation between lesions in the aortic origin and in the entire aorta, and differences in the extent of lesions between sexes in LDL receptor-deficient and apolipoprotein E-deficient mice.

Murine strains susceptible to atherosclerosis provide valuable models to study factors involved in atherogenesis. In some murine models, limited hypercholesterolemia can be achieved and lesions develop primarily in the aortic origin, in the vicinity of the aortic valve. In other models such as LDL receptor-deficient and apoE-deficient mice, diet-induced or spontaneous hypercholesterolemia and atherogenesis are much greater. To determine whether lesion formation in the aortic origin, where particular pathogenic conditions may exist, correlates with lesion formation throughout the entire aorta, we measured the extent of atherosclerosis in both areas in 8 apoE- and 11 LDL receptor-deficient mice fed cholesterol-rich diets for 3-6 months, as well as in 9 C57BL/6 mice fed an atherogenic diet for a year, using two different morphometric methods. Both apoE-deficient and LDL receptor-deficient mice developed extensive lesions throughout the aorta, and in these models a significant correlation was observed between the extent of lesions in the entire aorta (measured as percent of surface area) and that at the aortic origin (measured as averaged lesion area per cross-section) (r = 0.77, P < 0.0001). In contrast, the plasma cholesterol levels achieved in C57BL/6 mice were much lower, and atherosclerotic lesions were found almost exclusively in the aortic origin. These results demonstrate that in murine models developing extensive aortic lesions, both morphometric methods provide valid and complementary information on the degree and distribution of atherosclerosis, and suggest that under severe atherogenic conditions lesion formation throughout the aorta is determined by the same pathological factors, in each model. Comparison of the extent of atherosclerosis in the entire aorta between genders also showed that male LDL receptor-deficient mice had significantly more lesions than females (29.2 vs. 14.8%, P < 0.005, n = 16). A similar trend was also seen in apoE-deficient mice.