Re-evaluating the Impact of Biological Sex on Atherosclerosis in Apoe-/- and Ldlr-/- mice

BACKGROUNDThe progression of cardiovascular disease shows significant sexual dimorphism: although females generally develop the disease later in life, they exhibit a higher age-related incidence than males. Despite this clinical pattern, preclinical studies often overlook both sexes in their design, and existing research on sex-specific atherosclerosis in mice remains inconsistent. This study was designed to assess the influence of sex on atherosclerosis using two widely used atherosusceptible mouse models--Apoe-/- and Ldlr-/- mice. METHODSTo investigate the influence of sex on atherogenesis, we conducted a 20-week study using both male and female Apoe-/- and Ldlr-/- mice. The mice were fed an atherogenic ALMN diet (40% trans-fat, 2% cholesterol, 22% fructose) to promote plaque development. We performed comprehensive analyses of: (1) systemic metabolic parameters (lipid profile, glucose metabolism); (2) atherosclerotic burden (en face and aortic sinus plaque area); and (3) plaque composition (necrotic core size, collagen content, macrophage infiltration). RESULTSIn both models, male mice showed higher lipid levels, worse glucose tolerance, and reduced insulin sensitivity compared to females. Apoe-/- mice showed minimal sex differences in atherosclerosis with a trend toward increased plaque size in females. Plaque stability markers-- including collagen content, necrotic core size, and macrophage infiltration--did not differ significantly between sexes. In contrast, Ldlr-/- males exhibited greater en face plaque burden than females, yet plaque stability remained similar across sexes. CONCLUSIONComparative analysis of two widely used murine atherosclerosis models revealed genotype-dependent sexual dimorphism. Female Apoe-/- mice showed a non-significant trend toward larger plaque areas than males, whereas male Ldlr-/- mice developed significantly larger en face atherosclerotic plaques than females. By evaluating plaque area and composition across these models, our findings underscore the importance of including both sexes in atherosclerosis studies, in accordance with guidelines from the National Institutes of Health and the American Heart Association.