ABSTRACT
【Objective】 To compare the histological characteristics of porcine pancreatic elastase （PPE） induced abdominal aortic aneurysms （AAA） and angiotensin Ⅱ （AngⅡ） induced AAA in mice. 【Methods】 In the PPE group， the mouse abdominal aorta segment from the infrarenal abdominal aorta to the iliac artery was isolated and its branch arteries were ligated to avoid leakage during PPE perfusion. We perfused the isolated aorta segment with a PPE solution at a concentration of 1.5 U/mL for 5 min and then closed the abdominal cavity. The diameter of the abdominal aorta was measured before and 14 days after the surgery， and the perfusion segment of the arteries was collected at day 14 after the surgery. The histological characteristics of the aneurysm were analyzed and graded by histological and immunohistochemical methods. In the AngⅡ group， ten apolipoprotein E knockout mice were prepared， and AngⅡ [1 000 ng/(kg·min)] was infused with osmotic pumps for 28 days. The aorta was separated and the aneurysm aorta segment was analyzed. The wild type mice were used as normal health controls. 【Results】 In the PPE group， the diameter of the PPE perfused aorta segments increased and was significantly larger than the basal diameter ［（0.52±0.02） mm vs. （1.23±0.11） mm］ at day 14 after surgery. All the ten mice developed AAA after PPE application. The histological results showed typical pathological features of AAA in PPE perfused mice， such as elastic fiber breakage， smooth muscle exhaustion， and increased inflammation. Six of the ten mice developed aneurysms after AngⅡ infusion （6/10）. The aneurysms/dilatations were mostly in the suprarenal abdominal aorta， but also in the thoracic aorta and aortic arch. The histology analysis showed that the formation of arterial dissection was common after AngⅡ infusion， and the typical vascular “false lumen” was found. The breakage of elastic fibers， the exhaustion of smooth muscle damage， and the inflammatory response were not as typical as the PPE model in AngⅡ perfused animals. 【Conclusion】 The histological characteristics of PPE induced AAA are very typical and well present the inflammatory process in the development of aneurysm. The AngⅡ model is suitable for the study of aneurysms combined with aortic dissection. Both models have their own advantages and can complement each other.