APOE and aneurysm: The results of Masson staining, EVG staining and immunohistochemical staining showed that the macrophage-positive area and the area of aneurysms in the ApoE-KO/Notch-1MAC-KO group significantly decreased compared with the ApoE-KO/Notch-1WT group (P < 0.01), while the SMC-positive area was not significantly different between the two groups (P > 0.05, P = 0.8394), indicating that macrophages play a major role in the regulation of AAA (Figure 2).