Experimental methods of abdominal aortic aneurysm creation in swine as a large animal model

Animal models of abdominal aortic aneurysms (AAA) enable preclinical studies on new therapeutic approaches and help to understand pathophysiology of the disease. The aim of this study was to demonstrate the effectiveness of selected methods of experimental induction of abdominal aortic aneurysm in swine and to adapt the EMG examination (electromyography) to record the vessel wall changes. The animals were divided into 3 groups comprising 4 individuals in whom AAA was surgically induced. In the first group the AAA was induced by mechanical stretching of the aortic wall and injection of 500 IU elastase under pressure. The second group received elastase and 6000 IU of collagenase. In the third group 0.5 M CaCl2 solution was introduced additionally. Enlargement of abdominal aorta was monitored for 4 weeks. The first group did not show any aorta dilatation. In the second group the aortic lumen was dilated on average by 71±3.5% (P≤0.001) as shown at autopsy and by 76.6±9.3% as measured by the ultrasound method. In the third group aorta was dilatated by 104.2±11.3% as obtained by ultrasound and 72±3% at post-mortem examination. Myoelectric activity of VSMC (vascular smooth muscle cell) was demonstrated and it was characterized by the presence of three types of waves closely related to the pressure changes in the vessel lumen. We conclude that collagen fibers damage plays a significant role in the AAA development in swine. The inflammatory process in the vessel's wall also contributes to AAA development. However, myoelectrical activity of VSMC does not significantly change despite histologically confirmed loss of muscular layer.