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ObjectiveTo investigate the method of establishing C57BL/6J mouse abdominal aortic aneurysm (AAA) model by porcine pancreatic elastase (PPE, 1.5 U/mL in PBS) perfusion and evaluating its histological characteristics.MethodsThirty male mice were divided into two groups, the model group (n=20) and solvent control group (n=10). After opening the abdominal cavity in all mice, the infrarenal abdominal aorta to the iliac artery segment was isolated and perfused with PPE solution at a dose of 1.5 U/mL for 5 minutes. After the operation, the abdomen was closed and sutured. The aorta segment of the control group was perfused with PBS. The diameters of the abdominal aorta were measured before and after 14 days of the operation, and perfusion aorta segments were collected 14 days after operation for following histological analysis. The histological characteristics of the aneurysms were analyzed and graded by histological and immunohistochemical methods.ResultsCompared with the preoperative or PBS solvent control mice, the abdominal aortic diameters were significantly increased in the PPE perfused group on day 14 after operation (0.53±0.03 mm, 0.78±0.06 mm vs 1.20±0.12 mm, respectively). Histological analysis revealed that the PPE-infused AAA segments had elastic fiber breakage, smooth muscle cell depletion, and increased inflammation response, which resembles the typical pathological features of AAA, suggesting the mice model of AAA was successfully induced by PPE infusion. According to the histological characteristics of the AAA lesions, we graded the aneurysms and established a revised practical method for evaluating the aneurysm lesions in the experimental AAA mouse model.ConclusionA methodological system for establishment and histopathological evaluation of PPE-induced AAA in mice has been successfully established.

Aim: Compared with the C57BL/6N substrain, the C57BL/6J substrain is more susceptible to the angiotensin II (Ang II)-induced development of dissected abdominal aortic aneurysms (AAAs). The aim of this study was to elucidate whether the widely used C57BL/6N mouse substrain is as susceptible as the C57BL/6J mouse substrain to porcine pancreatic elastase (PPE) infusion-induced experimental nondissected AAA development., Methods: Experimental nondissected AAAs were induced in C57BL/6J and C57BL/6N mice via transient aortic luminal infusion of PPE. On Day 0 (baseline) and Day 14 after PPE infusion, the abdominal aortic diameter was directly measured. Aortic aneurysmal segment samples were collected, and histopathological analysis was performed., Results: On Day 14 after PPE infusion, aortic diameters were significantly increased in both mouse substrains (from approximately 0.51 to 1.24 mm in C57BL/6J mice and from 0.51 to 1.18 mm in C57BL/6N mice). The increase in diameter of all the mice exceeded 50% and met the criteria for AAA model establishment (143% and 135% in C57BL/6J mice and C57BL/6N mice, respectively). PPE infusion also induced obvious local aortic wall macrophage and T -cell infiltration, elastin degradation, smooth muscle cell depletion and high metallopeptidase (MMP)-2 and MMP-9 expression levels in C57BL/6N mice, but these differences were not significant compared with those in C57BL/6J mice. However, PPE infusion led to the recruitment of more B cells and the sprouting of more neovessels at the aneurysmal lesion site in C57BL/6J mice than in C57BL/6N mice., Conclusion: The C57BL/6N mouse substrain is suitable for establishing a model of AAA via elastase infusion., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (© 2024 Wei, Li, Li, Liu, Xia, Chen, Zhao and Li.)