COMP and infection: Next, we overexpressed COMP in the suprarenal aortas of ApoE–/– mice to determine whether aorta-resident COMP was sufficient to prevent AAA formation, since previous reports indicated that 4–5-month-old ApoE–/– mice exhibited a higher incidence of AAA (50%–70%) than C57BL/6 mice (10%).38,39 COMP was overexpressed in 4-month-old male ApoE–/– mice via the periadventitial infection of an adenovirus encoding COMP (Ad-COMP) (Supplementary information, Fig. S4a, b).