Experimental Study Of Macrophages And Smooth Muscle Cells In The Distribution Of Atherosclerotic Plaque

Atherosclerotic plaque rupture is the main reason of acute cardiovascular and cerebrovascular incident, so identify vulnerable plaque is significance to prevent the occurrence of acute cardiovascular and cerebrovascular incident. With the development of medical imaging technology, the use of non-invasive imaging methods to diagnose atherosclerotic plaque has been achieved. However, how to early predict acute cardiovascular and cerebrovascular incident in atherosclerosis patients has been the needed to resolve problem of current. Atherosclerotic molecular imaging research is the important content of the prevention and treatment of cardiovascular and cerebrovascular disease. To establish the ApoE-/-carotid atherosclerosis mice model by high fat diet were fed and silastic collars were placed around the left carotid artery and to visualize the atherosclerotic plaque by7.0T MR scanner, and to detect the distribution of macrophage and vascular smooth muscle cells in atherosclerotic plaque by pathological methods for further molecular imaging research. The experiment is divided into the following three parts:Part I Atherosclerotic plaque characteristics and magnetic resonance imaging of E-/-mice modelsObjective To establish the ApoE-/-carotid atherosclerosis mice model and to visualize the atherosclerotic plaque by7.0T MR scanner.Materials and Methods High fat diet were fed and silastic collars were placed around the left carotid artery of ApoE-/-mice and wild type C57mice to establish carotid atherosclerosis model (n=6). The atherosclerotic plaque formation in the left carotid were observed by MRI after eight weeks, and blood samples were taken to measure serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL) and low-density lipoprotein (LDL) and the left carotid artery specimens were taken to stain with HE to observe the pathological changes, and the plaques were taken to stain with Oil Red O to observe the fat.Results The vessel wall of the left carotid showed hyperintensity and the lumen were irregularly narrowed on MRI in experimental group after8weeks. And the histopathological examination showed atherosclerotic plaque in the vessel wall of the left carotid and the lumens were irregularly narrow. In the control group, only two cases showed hyperintensity in the vessel wall of the left carotid and irregularly narrow lumens by MRI, and the histopathological examination showed thickened arterial wall with no atherosclerotic plaque formation in the lumen of carotid. TC and LDL levels of experimental group were significantly higher than those of control group (t=9.99and9.12, respectively, P<0.01), and the TG and HDL values showed no significant between-group difference (t=-1.71and-1.05, P>0.05).Conclusion Carotid artery atherosclerosis of E-/-mice can be quickly established through high fat diet and placing carotid collar, and7.0T MRI can successfully evaluate the carotid atherosclerotic plaque. Part Ⅱ USPIO-MR imaging of atherosclerotic plaque in ApoE"" mice modelsObjective To explore the feasibility of detecting atherosclerotic plaque by USPIO ehanced MRI in ApoE-/-mice model.Method and Methods High fat diet were fed and silastic collars were placed around the left carotid artery of ApoE-/-mice and wild type C57mice to establish carotid atherosclerosis model (n=6). After8weeks, MRI was performed before and48h after intravenously administration of USPIO (0.25mmolFe/kg). When MRI scan is completed, take the left carotid artery were stained with Prussian blue staining and immunofluorescence of CD68and α-SMA.Results In ApoE-/-mice, in vivo48h post-USPIO T2WI images revealed focal signal loss in the carotid than that of pre-USPIO, with relative signal intensity1.00±0.24and0.73±0.21, respectively, and the percent of signal reduced was (28.01±9.20)%(t=7.78, P<0.01). Histopathological examination confirmed the depositions of iron particles in the plaque lesions in agreement with the distribution of macrophage. In C57mice, with relative signal intensity1.12±0.18and1.09±0.24, respectively, and the percent of signal reduced was (-6.58±23.19)%(t=0.71, P>0.05). Histopathological examination showed without iron particles deposition in the thickening blood vessel wall of only2cases.Conclusion The USPIO can be targeted to macrophages in atherosclerotic plaques. Part Ⅲ:The distribution of macrophage and vascular smooth muscle cells in atherosclerotic plaques in ApoE-/-mice modelObjective To detect the dynamic variation of macrophage and vascular smooth muscle cells in atherosclerotic plaques in ApoE-/-mice model.Materials and Methods12male ApoE-/-mice were randomly divided into3groups (n=4) which received high fat diet and placed silastic collars around the left carotid artery to establish carotid atherosclerosis model. The every group was executed after2,4and6weeks, the left carotid artery specimens were taken to stain with immunohistochemistry to observe the dynamic variation of macrophage and vascular smooth muscle cells in atherosclerotic plaques.Results After2weeks, the carotid intima of mice damaged. After4and6weeks, the different degree atherosclerotic plaques emerged. Macrophage was limited in the plaque with dispersive distribution, and the expression of macrophage turns to be more significant along the development of atherosclerotic plaques. Vascular smooth muscle cells were mainly limited in surface of plaque and the expression of vascular smooth muscle cells turn to be no obvious change long the development of atherosclerotic plaques,Conclusion The expression of macrophage turns to be more significant along the development of atherosclerotic plaques and the expression of vascular smooth muscle cells turn to be no obvious change along the development of atherosclerotic plaques, which can be used as potential target cells in atherosclerotic plaque formation in vivo detection of molecular imaging.