The Role Of Autophagy In The Pathogenesis Of Autologous Arteriovenous Fistula Stenosis

Objective: A well functional vascular acess(VA)can ensure the quality of dialysis and the life of dialysis patients.It is essential for maintenance hemodialysis(MHD)patients.VA complications have become the main cause of hospitalization in MHD patients.However,it is known that many newly formed fistulae do not mature and have a higher restenosis rate to provide qualitative hemodialysis.The histology of intimal hyperplasia is a primary cause of AVF immaturation and failure,and characterized by an abundance of vasculer smooth muscle cells.Platelet derived growth factor(PDGF)can promote the cells proliferation and migration and regulate vascular smooth muscle cell phenotype transformation.Although appropriative autophagy seems to be critical to the cell survival,excessive autophagy cause the disease to occur.Little known about the relationship between autophagy and AVF intima hyperplasia.To investigate the role of autophagy in the pathogenesis of autologous arteriovenous fistula stenosis,providing the prevention and treatment of AVF stenosis in the future.Methods: Venous vascular tissues were collected during the surgery of AVF angioplasty or reconstruction for MHD patients in the Third Hospital of Hebei Medical University from November 2016 to November 2017.The samples were divided into experimental group A,experimental group B and control group.We resected the stenosis and the adjacent stenosis part of the venous in AVF reconstruction operation and setted into the experimental group A(n=10)and the experimental group B(n=10).The control group(n=10)venous tissues were discarded in AVF angioplasty operation.Histological changes were examined and the thickness of intima was measured after H-E staining of the venous tissues.Immunohistochemistry was used to examine the leval of Beclin-1,LC3 II and PDGF-bb expression in the intima of venous tissues.Then we analyze the relation between the thickness of intima and growth factors expression.All data was analyzed by statistical analysis software SPSS 21.0 and expressed as mean ± SE((?)±s).Probability values less than 0.05 were required for statistical significance.Results: To analyszed the age and sex,there was no statistical difference between the two groups(P <0.01).1 HE stainingThe thickness of intima and media in the vein were various degrees of thickened,and the thickness of intima was more obvious.The intima of the experimental group A which protrude lumen increased more than the experimental group B under light microscope.The hyperplasia intima was composed of a large number of disordered smooth muscle cells under high magnification.We measured the mean ratio of intima/media thickness in the each group.There was related significant difference in each grops(p<0.01).2 immunohistochemical staining 2.1 Beclin-1 is mainly expressed in the cytoplasm of VSMCs.The Beclin-1 strongly positive expressed in intima of the experimental group A,medium positive in media of the experimental group A.The medium positive expression was found in the intima and media of experimental group B.The expression of the intima and middle in the control group was weakly positive.The expression level of Beclin-1 in the experimental group A was higher than that of the experimental group B,with remained significance(P <0.01).2.2 LC3 II is mainly expressed in the cytoplasm of VSMCs.The protein of LC3 II strongly positive expressed in intima of the experimental group A,medium positive in media of the experimental group A.The medium positive expression was founded in the intima and media of experimental group B.The expression of the intima and middle in the control group was weakly positive.The expression level of LC3 II in the experimental group A was higher than that of the experimental group B,with remained significance(P <0.01).2.3 PDGF-bb is mainly expressed in the cytoplasm of VSMCs.The protein of PDGF-bb strongly positive expressed in intima of the experimental group A,and the medium positive expression was found in the experimental group B.The expression of the intima and middle membrane in the control group was weakly positive.Compared of the expression of each groups,and there was statistical significance(P <0.01).2.4Negative control for immunochemistry stainingNo positive staining expression was founded in both intima and media.3 Correlation AnalysisThere was a positive correlation between PDGF-bb and Beclin-1 expression in each group(r=0.883,P=0.001;r=0.919,P=0.000;r=0.947,P=0.000).And the expression of Beclin-1 in each group was positively correlated with LC3 II(r=0.859,P=0.001;r=0.896,P=0.000;r=0.997,P=0.000).Conclusions:1.Autophagy participates in the process of vascular remodeling and stenosis after AVF establishment.Autophagy not only contributes to fistula maturation,but also autophagy induces intimal hyperproliferation.2.PDGF-bb mediated autophagy regulates vascular smooth muscle cell phenotype,which could be a new target for the treatment and prevention of AVF stenosis in the future.