ABSTRACT
Objective To determine the time point when porcine pancreatic elastase(PPE)induced abdominal aortic aneurysm(AAA)reaches the regression phase in mice and observe the histological characteristics of AAA in regression phase.Methods AAAs were induced by transient intraluminal infusion of PPE in C57BL/6J mice.The diameters of the mouse abdominal aortas were measured before PPE infusion and sacrifice time,day 14 for AAA progression phase or day 56 for regression phase after PPE infusion,respectively.The histological characteristics of the aneurysm lesion site on day 14 and day 56 after surgery were compared and analyzed.Results The diameters of the abdominal aortas were significantly increased in both day 14 and day 56 after PPE infusion groups(diameter growth rate 147％and 155％,respectively)as compared to the baseline diameters.In the day 14 group,the infused aortas showed typical AAA characteristics,such as elastin break/degradation,medial smooth muscle cells depletion,and inflammatory cell diffused infiltration.In the day 56 group after PPE infusion,although the artery diameter did not change significantly as compared to the day 14 group,histology showed that elastin was partially repaired,new smooth muscle cells were added to the damaged aorta media,the infiltrated inflammatory cells were significantly subsided,and the adventitia neovascularization was reduced,showing a significant feature of the disease regression phase.Conclusion In the PPE-induced mouse AAA model,day 56 after surgery is an appropriate time point for observing aneurysm regression,and the histological characteristics of the regression are obvious.
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.