Establishment of Experimental Abdominal Aortic Aneurysm Model in Rats

Objective To establish a new reliable experimental abdominal aortic aneurysm (AAA) rat model that simulates human aneurysms and has high survival rate. Methods Twenty-four SD rats were randomly divided equally into two groups (male∶female=1∶1). Intraluminal saline infusion was given to rats in group A. Rats in group B were given intraluminal elastase infusion and extraluminal calcium chloride application. The diameter of abdominal aorta was measured and eventually harvested at 4 weeks. Successful AAA formation was defined as a dilation ratio >50%. HE stain was applied to evaluate the histology changes of aorta. Results Group A had a survival rate, technical success rate and AAA formation rate of 83.3%, 91.67%, and 0% respectively, compared with 91.67%, 100%, and 90.91% in group B. The AAA formation rate in group B was significantly higher than that in group A (P<0.05). The dilation ratio during infusion was 50.82%±4.11% in group A and 48.19%±3.89% in group B. The dilation ratio after infusion was 29.55%±4.69% in group A and 27.89%±4.28% in group B. The difference of dilation ratio between the two groups was not significant. The post-surgery (28 d) dilation ratio was 27.89%±4.28% in group A and 88.98%±42.33% in group B (P<0.05). Fusiform aneurysms, local adhesion and calcification were found in group B. Rats in group B also had thickening intimal, degenerated matrix in media, loss of elastin fiber, apoptosis of vascular smooth muscle cells and transmural inflammation, none of which was observed in group A. Conclusion With improved operative procedure, intraluminal elastase infusion and extraluminal calcium chloride application can create reliable AAA rat model.