Pathological Observation And Therepy Of Atherosclerotic Plaques In ApoE Knock Out Mice

Objective(1) To observe pathological characteristics of atherosclerotic plaques in aortic sinus and brachiocephalic artery in apoE knock-out mice fed with western-diet;(2) To observe pathological characteristics of atherosclerotic plaques in brachiocephalic artery in old apoE knock-out mice (≥48weeks) fed with western-diet;(3) To investigate the effect of simvastatin on regression of atherosclerotic plaques in old apoE knock-out mice (≥60weeks) .Methods96 male apoE knock-out mice were fed with a western diet when they were 6 weeks old.(1) Six apoE knock-out mice were sacrificed at random when they were14,30,42,54,66 and 78 weeks old respectively for serum lipids, and then aortic sinus and brachiocephalic artery were isolated for pathological determination.(2) Ten apoE knock-out mice were sacificed at random when they were 54, 66 and 78 weeks old respectively for serum lipids and brachiocephalic artery were isolated for pathological determination.(3) Simvastatin was administered to 60-week-old apoE knock-out mice exhibiting advanced atherosclerotic plaques. 30 apoE knock-out mice were randomly divided into three groups: model group, high-dose simvastatin-treated group, and regular simvastatin-treated group, which were administered with Sodium Chloride, simvastatin (20 mg/kg per day), and simvastatin (2.5 mg/kg per day) for 8 weeks respectively. The apoE knock-out mice were sacrificed for serum lipids and aortic sinuses were isolated for pathological determination.Frozen slides of aortic sinus and brachiocephalic artery were stained with hematoxylin and eosin; oil red O, OPN,α-actin and von kossa. Analysis was performed with a computerized image analysis program (Image Pro Plus). Results (1) The aortic sinus is relatively straightforward to locate for histological processing, and in consequence standardization across studies and laboratories is easy. The lesions that eventually develop at this site in apoE knock-out mice are large and lipid-rich, meaning that a simple lipid stain such as oil red O can be used to aid morphometric analysis. The brachiocephalic artery is a site where ruptured plaques have been reported to occur in the apoE knock-out mouse.Lesions develop rapidly at this site, especially under conditions of high-fat-feeding. Intraplaque hemorrhage is a frequent finding. On the negative side, this vessel is very small and consequently difficult to process for histology.(2) Advanced atherosclerotic plaques were observed in all mice. More plaques area, calcification area, instable plaque, ratio of spontaneous plaques rupture was observed in 60 weeks old mice.(3) Serum cholesterol levels were significantly decressed in the simvastatin-treated mice relative to control mice(P<0.05). Histological analysis of sections of aorta stained with HE, OPN and von Kossa stains demonstrated a significant reduction in cross-sectional area of atherosclerotic lesions(P<0.05) and the frequency of calcification in atherosclerotic plaques(P<0.01).Conclusions(1) ApoE knock-out mice with weatern diet for a long time are good animal models for advanced atherosclerotic plaques research. The brachiocephalic artery is a site where ruptured plaques occur. The aortic sinus is a nonvulnerable comparator site for other parts of the murine arterial tree where ruptures do occur.(2) ApoE knock-out mice with weatern diet for a long time are good animal models for advanced atherosclerotic plaques research.(3) These data suggest that serum cholesterol levels were significantly decreased in the simvastatin-treated mice relative to control mice. Andsimvastatin has regression effects on advanced atherosclerotic lesions...