Abstract MP23: Knockout Of Pgc1α In Endothelial Cells Augments Abdominal Aortic Aneurysm Formation

Abstract

Introduction: It is well described that changes in the aortic media are crucial in the development of Abdominal Aortic Aneurysms (AAA), however the involvement of the endothelium is not as clear. The endothelium is the first vascular layer exposed to blood flow and aneurysms preferentially form in areas of disturbed flow. The regulatory mechanisms as to why aneurysms form at these sites remains unclear. Here we propose that the transcription coactivator peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) plays a pivotal role in the endothelium’s response to AAA formation in a shear responsive manner. Methods: 10-12 week old male mice deficient in endothelial specific PGC1α (KO) and their corresponding wild type background mice (WT) were treated with 0.75 mg/kg/day of Ang II. Our primary endpoints were measurement of the maximal width of the suprarenal aortas, frequency, and complexity based on the Daugherty classification. To determine the effects of shear, HAECs exposed to steady flow (15 dyn/cm 2 ) and disturbed flow (0±6 dyn/cm 2 at 1 Hz) for 12 hours were compared to determine if mRNA expression were different for PGC1α and SIRT1. Results: AAA incidence and severity were increased in ANG II-infused KO compared to the WT mice (100% vs. 20%, respectively). Measurements of excised aortas showed that KO mice exhibited larger AAA fold-increase compared to WT (2.00 ± 0.11 fold increase vs. 0.43 ± 0.19 fold increase, p-value 0.0002). The KO male mice also exhibited a more complex phenotype. HAECs that underwent disturbed flow had a significant decrease in expression of SIRT1 (p = 0.02) and trended towards a decrease in expression of PGC1α (p = 0.06). Conclusions: Our data strongly suggests that knockout of endothelial specific PGC1α leads to more frequent, complex and larger AAAs primarily in the suprarenal aorta, which is an area of disturbed flow. Interestingly, the addition of ANG II alone was able to induce AAA formation in our model. Additionally, we show that PGC1α and SIRT1 are regulated in a shear responsive manner. Taken together, endothelial PGC1α likely plays a regulatory role in AAA formation through shear-related mechanisms.