Study For The Association Between Hypertension And Abdominal Aortic Aneurysm Development

Abdominal aortic aneurysm(AAA) remains to be an extremely morbid vascular disease, with the increasing incidence rate year by year. The aetiology of AAA is still not fully understood. The association between the expansion rate (ER) of AAA and some of common cardiovascular risk factors, such as hypertension, is controversial. In this study, we focused on the effect of hypertension in the process of AAA expansion through modeling AAA on hypertensive and normotensive rats, respectively. We compared the expansion rates and pathological changes with each other and attempted to provide some experimental references for a more clear understanding about the pathogenesis of AAA.ObjectivesTo approach the association between AAA expansion and hypertension through the measurements of AAA diameters on rats and observation of pathological changes in the vessel wall.Methods1. AAA was produced by elastase perfusion of the abdominal aorta in hypertensive(SHR) rats and normotensive(Wistar) rats. Diameters were measured 3d before and 1w,2w after perfusion by ultrasonography. The expansion rates of AAA were calculated and statistical analysis was performed through the CHISS statistieal soft ware.2. AAA samples were collected 2w after perfusion. HE and immuno-histochemisty(IHC) analysis were performed to observe changes of the artery wall and the expression of matrix metalloproteinase (MMP)-2,-9. ResultsAAA were successfully modeled on both the hypertensive and normotensive rats. Diameters increased significantly 1 or 2 weeks after operation. Expansion was most apparent in 1w. And the size of AAA decreased slightly when observing at 2w point. There was no significant differences in expansion rates between the two groups 1 of 2w after operations. HE analysis showed phlogocyte infiltration in the adventitia of artery, degeneration in the media, absence of intima and thrombus occurred in AAA samples in both groups. Immunohistochemisty analysis showed that the expression of MMP-2 and MMP-9 in the adventitia and lateral media were more concentrated.ConclusionsAAA could be successfully induced in SHR rats. It provides a new animal models for the etiological study of AAA. There was no significant relationship between high blood pressure levels and expansion rates of the initial development of AAA. Degenerative changes of the artery wall due to MMP-2, MMP-9 should be considered as the main factor contributing to AAA expansion immediately. The high expression of MMP-2, MMP-9 in the adventitia and lateral media indicated a important location which maintains the abdominal aorta's structure and appearance.