Vascular smooth muscle–specific YAP/TAZ deletion triggers aneurysm development in mouse aorta
Marycarmen Arévalo Martínez, Olivia Ritsvall, Joakim Armstrong Bastrup, Selvi Celik, Gabriel Jakobsson, Fatima Daoud, Christopher Winqvist, Anders Aspberg, Catarina Rippe, Lars Maegdefessel, Alexandru Schiopu, Thomas A. Jepps, Johan Holmberg, Karl Swärd, Sebastian Albinsson
Marycarmen Arévalo Martínez, Olivia Ritsvall, Joakim Armstrong Bastrup, Selvi Celik, Gabriel Jakobsson, Fatima Daoud, Christopher Winqvist, Anders Aspberg, Catarina Rippe, Lars Maegdefessel, Alexandru Schiopu, Thomas A. Jepps, Johan Holmberg, Karl Swärd, Sebastian Albinsson
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Research Article Cell biology Vascular biology

Vascular smooth muscle–specific YAP/TAZ deletion triggers aneurysm development in mouse aorta

Abstract

Inadequate adaption to mechanical forces, including blood pressure, contributes to development of arterial aneurysms. Recent studies have pointed to a mechanoprotective role of YAP and TAZ in vascular smooth muscle cells (SMCs). Here, we identified reduced expression of YAP1 in human aortic aneurysms. Vascular SMC–specific knockouts (KOs) of YAP/TAZ were thus generated using the integrin α8–Cre (Itga8-Cre) mouse model (i8-YT-KO). i8-YT-KO mice spontaneously developed aneurysms in the abdominal aorta within 2 weeks of KO induction and in smaller arteries at later times. The vascular specificity of Itga8-Cre circumvented gastrointestinal effects. Aortic aneurysms were characterized by elastin disarray, SMC apoptosis, and accumulation of proteoglycans and immune cell populations. RNA sequencing, proteomics, and myography demonstrated decreased contractile differentiation of SMCs and impaired vascular contractility. This associated with partial loss of myocardin expression, reduced blood pressure, and edema. Mediators in the inflammatory cGAS/STING pathway were increased. A sizeable increase in SOX9, along with several direct target genes, including aggrecan (Acan), contributed to proteoglycan accumulation. This was the earliest detectable change, occurring 3 days after KO induction and before the proinflammatory transition. In conclusion, Itga8-Cre deletion of YAP and TAZ represents a rapid and spontaneous aneurysm model that recapitulates features of human abdominal aortic aneurysms.

Authors

Marycarmen Arévalo Martínez, Olivia Ritsvall, Joakim Armstrong Bastrup, Selvi Celik, Gabriel Jakobsson, Fatima Daoud, Christopher Winqvist, Anders Aspberg, Catarina Rippe, Lars Maegdefessel, Alexandru Schiopu, Thomas A. Jepps, Johan Holmberg, Karl Swärd, Sebastian Albinsson

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Figure 10

Aortic inflammation in i8-YT-KO mice involves cGAS genes.

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Aortic inflammation in i8-YT-KO mice involves cGAS genes. (A) We used Ly...
(A) We used Ly6 immunofluorescence to localize monocytes in aneurysms and found them predominantly in the adventitia. Arrow depicts rare monocytes infiltrating the media. Dashed lines represent the internal and external elastic lamina and the blue line demarcates neointima border. NI, neointima; L, lumen; A, adventitia. (B) To approach possible underlying mechanisms of inflammation and immune cell infiltration, we interrogated our transcriptomic data sets with a panel of cGAS/STING target genes. This panel was significantly increased at both time points (2 and 8 weeks), with the largest relative changes seen for Il6, Cxcl3, Il1b, and Mmp12. FC, fold change. (C) mT/mG mice were used to stain for STING (grayscale), which was high in the neointima and in the adventitia. However, smooth muscle cells (SMCs) in media also showed clear evidence of STING induction. Boxed areas are highlighted in magnified images (third and fourth rows). Some STING-positive cells were GFP positive (green, bottom row), suggesting that they are of SMC origin. Dashed lines represent the internal and external elastic lamina. (D) We next assayed the level of total (t)-STING by Western blotting (n = 6) and found it to be increased. Also shown are the Western blot data for p-TBK1 and t-TBK1 in Ctrl and i8-YT-KO aortae (n = 6). t-STING, p-TBK1, and t-TBK1 were blotted for on the same membrane. The membrane was stripped of anti–p-TBK1 before being blotted and analyzed for t-TBK1. DAPI (blue) was used as nuclear stain. **P < 0.01; ***P < 0.001 by Wilcoxon’s signed-rank test (B), Mann-Whitney test (D, left graph), or 2-tailed Student’s t test (D, right graph).