APOE and atherosclerosis: Quantification of atherosclerosis in aortic preparations stained with Oil red O revealed a significant 71% decrease in atherosclerotic plaque surface in 2K1C AT1aR−/− → ApoE−/− mice compared to control ones (0.29 ± 0.04% versus 1.01 ± 0.21%; Figure 2A,B).