Establishment Of A Novel Mouse Model Angiotensin?-induced Abdominal Aortic Aneurysm And Characterization Of Its Microcirculatory Reactivity

Abdominal aortic aneurysm?AAA?is a common disease in an aging society.In general,there is no obvious clinical manifestation,and most cases of Rupture Abdominal Aorta Aneurysm?RAAA?are found.And the overall mortality associated with RAAA is about 80%.Hyperlipidemia and hypertension are two of the main modifiable risk factors for AAA.The release of Angiotensin II into ApoE KO mice by surgically implanted osmotic pumps has been widely used in AAA studies.This study aimed to construct a new aneurysm model to explore its pathogenesis.Part I:Controllable AngII expression induces aortic aneurysm in a novel hyperlipidemia miceA(ApoE^SA/SA mice)containing high-density lipoprotein receptor SR-BI knockout,Doxycycline?DOX?-induced AngII expression and lipoprotein ApoE gene deficiency was constructed using CRISPR-Case9 gene editing technology.The plasma lipid concentration was measured and the blood pressure was monitored by the tail;an experimental mice abdominal aortic aneurysm model was established by high-fat diet combined with Doxycycline?DOX?in ApoE^SA/SAA/SA mice.H&E staining,Elastin staining and immunofluorescence were used to detect aneurysmal tissue in mice.ApoE^SA/SA mice in which a Scavenger Receptor Class B Type I?SRBI?and PDZK1 knock-down cassette was inserted downstream of the endogenous apoE promoter?thus abolishing apoE expression?,followed by DOX inducible Angiotensin?Ang?II expression cassette.The ApoE^SA/SA mice are hyperlipidemic and DOX treatment via drinking water increased blood pressure from 90 mmHg to platau,ie 150mmHg,in 5 zz Days,and,after DOX removal,bp decreased to normal level in 6 zzz days.Four weeks DOX treatment of ApoE^SA/SA male mice on HFD lead to a survival rate of 71.24%.Necropsy showed that mice that displayed rupture of abdominal aorta and/or ascending aorta,myocardial infarction,coronary atherosclerosis and abdominal aortic aneurysm.Among the survived mice,71.4%males and 40%females developed AAA.Morphological staining results showed that the model group AAA was visible compared to normal blood vessels.Arterial wall structure is disordered,there is anti-inflammatory cell infiltration;elastic fiber breaks and degrades;collagen cells migrate to the cell wall and common smooth muscle cell proliferation;thrombus formation and a small amount of new endothelial cells.Part II:Antihypertensive,lipid-lowering,anti-platelet,and the therapeutic effect of Forskolin on the cardiovascular phenotype of ApoE^SA/SA miceApoE^SA/SAA/SA mice were treated with high-fat diet and DOX-containing water.By administering an AT1 inhibitor?losartan?,a statin?atorvastatin?,and a platelet inhibitor?aspirin?to evaluate whether drug therapy works in the new model.Forskolin?FSK?was an agonist of cAMP.High-fat diet combined with DOX drinking water,FSK was intraperitoneally injected into mice,and the mice were randomly divided into control group and FSK group.The effects of FSK on AAA hypertension and atherosclerosis in ApoE^SA/SA mice were evaluated by measuring blood pressure,plaque quantification,and measurement of abdominal aorta diameter.Losartan can inhibit ApoE^SA/SA mice AAA formation,atorvastatin has no significant effect on the formation of AAA in ApoE^SA/SA mice,and aspirin can slow the formation of AAA in ApoE^SA/SA mice.In the mice with dysregulation of lipid metabolism and hypertension,the administration of FSK reduced the areas of atherosclerotic plaques developed in the thoracic aortas and the aorta roots.FSK failed to significantly decrease the high blood pressure and the incidence rates of abdominal aortic aneurysm.This study reveals an important role for FSK in inhibiting the development of atherosclerosis by improving endothelial repair.Part III:Identification of microcirculation and tissue damage in ischemia and reperfusion of lower limbsThe optimal ischemic conditions were determined by studying different ischemic patterns and ischemic time in the lower limb ischemia-reperfusion injury of C57BL/6mice;Eight weeks old ApoE^SA/SA mice were treated with the HFD,and with normal or Dox-containing water.to detect changes in the microcirculation of ischemia and reperfusion of the lower limbs and blood flow of the heart.By studying the ischemic microcirculation of lower limbs of C57BL/6 mice in different ways and ischemia time,the optimal ischemic pattern was established as arteriovenous ligation,and the ligation time was 10 min.Microcirculation tests showed that DOX-induced AngII in ApoE^SA/SAA/SA mice significantly reduced blood flow in the lower limbs and heart,but had no significant effect on the microcirculation of lower limb ischemia-reperfusion.ConclusionWe have successfully established a novel hyperlipidemia mice model that induces AngII expression,which can be used to induced abdominal aortic aneurysms.This new mice model is useful for understanding the pathological mechanism of human abdominal aortic aneurysm and evaluating drug treatment.This study also found that Forskolin has a good effect on the treatment of atherosclerosis-related diseases.