Kunming mouse strain is less susceptible to elastase-induced abdominal aortic aneurysms

Background:Porcine pancreatic elastase(PPE)is successfully used to induce abdominal aortic aneurysm(AAA)in mice.However,differences between mouse strains in susceptibility to PPE induction have been reported.Kunming mouse is one of the most frequently used strains in China but whether it is suitable for induction of AAA by PPE application remains unclear.Methods:PPE infusion(1.5 units/ml)in temporary controlled aorta was performed to induce AAAs in both C57BL/6J and Kunming mice.Phosphatebuffered saline(PBS)application was used as vehicle control.The aorta diameters of all mice were measured at days 0 and 14 after surgery to evaluate the AAA formation.Results:After 14 days of PPE or PBS infusion,all mice were sacrificed and aorta tissues were collected for histological staining analysis.At the 14th day after infusion,PPE successfully induced aortic dilation in Kunming mice and typical AAA in C57BL/6J mice.The aorta diameter increased by 0.23 mm in Kunming mice after PPE infusion,while it was 0.72 mm in the C57BL/6J strain.PPE induced mild elastin degradation,smooth muscle cell(SMC)depletion and mural leucocyte infiltration in Kunming mice,but in PPE-sensitive C57BL/6J mice,it induced total loss of SMCs,elastin disappearance and diffused infiltrated leucocytes in aortic aneurysmal segments.The effects of PPE in inducing angiogenesis and upregulating matrix metalloproteinase 2 and 9 expression in Kunming mice were also weaker than that in C57BL/6J mice.Conclusion:At the reported dose of PPE,Kunming mouse is not as susceptible to AAA formation as C57BL/6J mice.The failure of PPE to induce AAA formation in Kunming mice may be associated to its inability to boost a strong inflammatory response.

The incidence rate and histological characteristics of intimal hyperplasia in elastase-induced experimental abdominal aortic aneurysms in mice

Intimal hyperplasia(IH)is a negative vascular remodeling after arterial injury.IH occasionally occurs in elastase-induced abdominal aortic aneurysm(AAA)mouse models.This study aims to clarify the incidence and histological characteristics of IH in aneurysmal mice.A retrospective study was conducted by including 42 male elastaseinduced mouse AAA models.The IH incidence,aortic diameters with or without IH,and hyperplasia lesional features of mice were analyzed.Among 42 elastase-induced AAA mouse models,10 mice developed mild IH(24%)and severe IH was found in only 2 mice(5%).The outer diameters of the AAA segments in mice with and without IH did not show significant difference.Both mild and severe IH lesions show strong smooth muscle cell positive staining,but endothelial cells were occasionally observed in severe IH lesions.There was obvious macrophage infiltration in the IH lesions of the AAA mouse models,especially in mice with severe IH.However,only a lower numbers of T cells and B cells were found in the IH lesion.Local cell-secreted matrix metalloproteinases(MMP)2 was highly expressed in all IH lesions,but MMP9 was only overexpressed in severe lesions.In conclusion,this study is the first to demonstrate the occurrence of aneurysmal IH and its histological characteristics in an elastaseinduced mouse AAA model.This will help researchers better understand this model,and optimize it for use in AAA-related research.