Experimental Study Of The Effect Of Coronary Stent Implantation On Mechano Growth Factor And Ultrastructure In Vascular Smooth Muscle Cells

ObjectiveTo study the effect of stretch-mediated mechano growth factor overexpression on the in-stent restenosis,and to explore the related mechanisms to provide a theoretical basis for the clinical treatment of in-stent restenosis.MethodsMale Beagle dogs were randomly divided into 2 groups(n=7): stent implantation group and percutaneous transluminal coronary angioplasty group.Coronary angiography was performed immediately after 3.0*16mm stent implantation on 2 group,and the coronary stenting was evaluated in stent implantation group.At the same time,the histopathological sections were used to detect hyperplasia of coronary artery intima,proliferation and migration of vascular smooth muscle cells,thrombosis and inflammatory cell infiltration in 1 month after stent implantation.The ultrastructure of organelle of target vascular smooth muscle cells was detected by electron microscopy.The mechano growth factor m RNA expression was evaluated by in situ hybridization in target vascular smooth muscle cells.Western blot was used to detect the expression of MGF protein in target vascular smooth muscle cells.Serum samples were collected in before and 1 month after surgery.The serum levels of mechano growth factor were measured with ELISA kit.The data were analyzed using SPSS statistical package(version 17.0).Data were presented as mean ± standard deviation.Statistical comparisons were performed by t test.ResultsCoronary artery angiography was performed immediately after coronary stent implantation.The results showed that no vascular stenosis was found in the two groups and the stent was successfully implanted.The pathological analysis of coronary artery at 1 month after stent implantation suggested that stent implantation group were detected thickening of the intima,proliferation and migration of coronary artery smooth muscle cells,significant infiltration of inflammatory cells and thrombosis,leading to stenosis.However,no significant change was found in the percutaneous transluminal coronary angioplasty group.The result of electron microscopy showed that the number and volume of organelles in smooth muscle cells increased,suggesting that smooth muscle Cells had changed from contractile to synthetic type.In situ hybridization and Western blot analysis suggested that target vessel smooth muscle cells highly expressed mechano growth factor in 1 month after stent implantation.The statistic analysis revealed that there was significant difference between the two groups(P<0.01);however,there was no significant difference in serum mechano growth factor levels between the two groups before and after stent implanation.ConclusionsMechano growth factor is stretch sensitive.Scaffold expansion on the vascular wall promote inflammation of coronary artery,which causes highly expression of mechano growth factor in local coronary artery smooth muscle cells.Moreover,the proliferation,migration and phenotypic changes of vascular smooth muscle cells increase,finally leading to in-stent restenosis.Therefore,Mechano growth factor as a repair factor,proper inhibition of mechano growth factor of coronary artery smooth muscle cells may be effective in reducing the appearance of in-stent restenosis.