APOE and triple-A syndrome: Two mouse AAA models were used to examine the role of CD34+ cells in AAA development: 1) adventitial application of calcium chloride (CaCl2) to the infrarenal aorta of Cd34‐CreERT2; Rosa26‐tdT mice and 2) subcutaneous implantation of an Ang II osmotic pump in Cd34‐CreERT2; Rosa26‐tdT; Apoe−/− mice to induce AAA, typically in the suprarenal aorta (Figure 2A).