To elucidate the role of macrophage‐derived NINJ1 in AAA formation and progression, Ninj1flox/flox mice were crossed with mice transgenically expressing Cre from the myeloid cell‐specific gene encoding LysM (Lyz2‐Cre) on an ApoE knockout background to generate macrophage NINJ1‐deficient ApoE−/− mice (ApoE−/−Ninj1flox/floxLyz2‐Cre), hereafter referred to as Ninj1ΔMΦ mice (Figure S2A–C, Supporting Information). The gene discussed is APOE; the disease is triple-A syndrome.