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Background:Autophagy has been found to be involved in animal and cell models ofatherosclerosis,but to date,it lacks general observation in human atherosclerotic plaques.Here,we investigated autophagy in smooth muscle cells (SMCs),endothelial cells (ECs),and macrophages in human atherosclerotic plaques via transmission electron microscopy (TEM),west blotting,and immunohistochemistry analysis.Methods:The histopathologic morphology of these plaques was observed via hematoxylin and eosin staining.The ultrastructural morphology of the SMCs,ECs,and macrophages in these plaques was observed via TEM.The localization ofmicrotubule-associated protein 1 light chain 3 (MAP 1-LC3),a relatively special maker ofautophagy,in plaques was observed by double fluorescent immunochemistty and west blotting.Results:All of these human atherosclerotic plaques were considered advanced and unstable in histologically observation.By double fluorescent immunochemistry,the expression of LC3-Ⅱ increased in the SMCs of the fibrous cap,the macrophages,and the microvascular ECs of the plaque shoulders.The protein level of LC3-Ⅱ by west blotting significantly increased in plaques compared with normal controls.In addition,TEM observation of plaques revealed certain features of autophagy in SMCs,ECs,and macrophages including the formation of myelin figures,vacuolization,and the accumulation of inclusions in the cytosol.These results indicate that autophagy is activated in SMCs,ECs,and macrophages in human advanced atherosclerotic plaques.Conclusions:Our study is to demonstrate the existence of autophagy in human atherosclerotic plaques by different methods,which may contribute to the development of pharmacological approaches to stabilize vulnerable and rupture-prone lesions.