Defective autophagy in vascular smooth muscle cells enhances the healing of abdominal aortic aneurysm.

Autophagy is an evolutionarily conserved cellular catabolic process essential for cell homeostasis, and thus its failure is associated with several diseases. While autophagy has been reported to play a role in vascular smooth muscle cells (SMCs) in vascular disorders, its precise role in the pathogenesis of abdominal aortic aneurysm (AAA) has not yet been elucidated. In this study, we investigated the role of SMC autophagy in AAA formation. As a mouse model of AAA, we used control apolipoprotein E-deficient (apoeKO) mice and Atg7cKO (SMC-specific Atg7-deficient mice):apoeKO mice administered angiotensin II for 4 weeks. Intriguingly, Kaplan-Meier curves showed that the survival rates of Atg7cKO:apoeKO mice were significantly higher than those of apoeKO mice. The hematoma area in AAA of Atg7cKO:apoeKO mice was smaller than in apoeKO mice despite the lack of a significant difference in AAA incidence between the two groups. Furthermore, the amount of granulomatous tissues was significantly larger and the collagen-positive area within AAA was significantly larger in Atg7cKO:apoeKO mice than in apoeKO mice. In accordance with these findings, SMCs cultured from Atg7cKO mice showed increased expression of collagens, independent of angiotensin II action. Taken together, our data suggest that defective autophagy in SMCs elicits AAA healing that may underlie the better survival rate under dyslipidemia and angiotensin II infusion.