AGT and dissection: We previously reported that the loss of MAPK14 in VSMCs markedly prevented aortic dissection and AAA formation in an Ang II-induced mouse AAA model.19 To determine the precise mechanism underlying the protection exerted by MAPK14 loss in VSMCs, we isolated AAs from Mapk14 KO (Sm22-Cre/Mapk14f/f/Apoe-/-, hereafter referred to as KO) and WT littermate (Mapk14f/f/Apoe-/-, hereafter referred to as WT) mice on day 7 after Ang II infusion, an early stage of AAA development.