| Objective: It was found that saccular aneurysms accounted for 66-98% of intracranial aneurysms from the clinical and autopsy studies. However, the mechanism of the development, growth and rupture of saccular aneurysm is still not clear, so further clinical and experimental studies should be done. Hypertention is one of the controversial factors that influence the evolution of aneurysm. Early clinical studies revealed that there's no definitive relationship between hypertention and aneurysm. But recently, several studies indicated that hypertention play a important role in the evolution of aneurysms. However, its mechanism remained unclear in those studies. Probabally there were no ideal animal models for it, or the role of hypertention was underestimated. In this study, the experimental aneurysm was induced by corrosion of arterial wall with elastase, imitating clinical intracranial aneurysms patho-morhologically, and it will also serve as a foundation for further research on aneurysm. The effect of blood pressure elevation on the growth of saccular aneurysms and its mechanism were studied by this animal model.Methods: Forty-eight SD rats were divided into 3 groups randomly(A, B and C, each with 16 rats). The saccular aneurysms of carotid artery were induced by corrosion of initial segment of the external carotid artery (1mm long) with elastase. In group A, the posterior branches of both renal arteries were ligated in order to get blood pressure elevation severely. In group B, only one side was ligated, the bloodpressure increased moderately. Group C without any elevation of blood pressure served as the control group. After 2 and Sweeks, the animal blood pressure, the velocity of flow in parent arteries and aneurysms, and the size of the aneurysms were measured. Then the aneurysms were fixed by intraarterial perfusion of formalin and were resected. The pathological characteristics and expression of cell growing factors in aneurismal wall were evaluated by the methods of hematoxylin-eosin, van Gieson and immunohistochemical analysis.Results: ?The pathological features of the experimental aneurysms showed that the tunica intima was not continuous, the elastic and muscular layers were disrupted or disappear , and the proliferative collagen fiber could also be seen, which were similar to the natural aneurysms.(2)Before operation, the blood pressure was 104 ? mmHg ; after 2W, the blood pressure elevated moderately in group A (131 ±14 mmHg) , elevated slightly in group B (119±12 mmHg) ; after 8W, the blood pressure elevated severely in group A (178±16 mmHg) , elevated moderately in group B ( 144±12 mmHg) ; it was stable in group C. The velocity of parent arteries increased while the blood pressure elevated.(3) The size of aneurysms: after 2w, there is no difference among the 3 groups. But after 8W, the significant difference was found between A and the other two groups. (4) The higher the blood pressure elevate, the faster the aneurysms grow(r=0.875), and the larger the size of aneurysms, the slower the blood stream in aneurysms (r=-0.883). (5) The endothelial injury in large aneurysms were more severe than that in small ones; The elastin is mostly lost and the structure of the wall is more disturbed in large aneurysms. (6)After 2W, bFGFand VEGF expressed slightly in the 3 groups. But after 8W, their expression in group A was stronger than that in group B and C. The expression of bFGF mainly occurred in intracelluar plasm and extracelluar matrix of fibrocytes and smooth muscle cells in media. In some large aneurysms, the bFGF expressin could be found in all layers of the wall. The expression of VEGF mainly locateded in tunica intima, adventitia, severely disrupted struture and around some small vessels of the adventitia and media of aneurysms.Conclusion: (T) This experimental aneurysm was similar to natural aneurysm patho-morhologically and provided an ideal model for experimental studies on the aneurysm. ?The growth of aneurysm is related to the distruction of elastic fibers.?The eleva...
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