| Objective:Vascular occlusive disease is the leading cause of human death.Although vascular surgeon do their best to treat patients with this disease,the incidence of long-term serious adverse events remain high,which greatly affect human life quality.Autologous vascular bypass graft is the classical and effective method for treating vascular occlusive disease.Vein graft stenosis is the main reason of operation failure.With the great development of endovascular treatment technology in recent years,endovascular technology has been gradually applied in the field of vein graft treatment.From the initial balloon dilation to the current drug-eluting stent,the treatment strategy is improving,but the metal stent stay in human body permanently brings some difficult clinical problems in the long term that can lead to serious adverse events such as stent thrombosis and restenosis.In order to solve this problem,the medical world has focused on the biodegradable scaffold,as known as the fourth revolution of endovascular technology.Biodegradable scaffolds can be divided into two categories:polymer absorbable scaffolds and metal absorbable scaffolds.Absorbable magnesium alloy stent(Biodegradable magnesium alloy stent,BMAS)in recent years is the High-profile research direction.Due to its good mechanical performance and the effect of inhibit neointimal proliferation,promote reendothelialization,it have been entered clinical trials in patient with coronary heart disease.Rapamycin is a classical anti-proliferative drug whose inhibitory effect on the proliferation of vascular smooth muscle cells has been widely confirmed.The purpose of this study is to combine rapamycin-eluting biodegradable magnesium alloy stent with traditional vascular bypass graft,simulate the clinical operation environment by carrying out arteriovenous anastomosis,and to observe the remodeling of vein graft anastomosis which is braced by rapamycin-eluting BMAS.Methods:In this study,we first improved the method of vein graft stenosis rabbit model,in order to establish a stable animal model of vein graft stenosis which can accept endovascular intervention.Beyond the traditional animal model,the vein graft donor was subjected to balloon injury in advance,in order to simulate clinical pathological conditions.Then the autogenous jugular vein was end-to-end sutured into the infrarenal abdominal aorta.We implanted a rapamycin-eluting biodegradable magnesium alloy stent in the vein graft stenosis.The experimental animals were re-anesthetized and underwent digital subtraction angiography(DSA)and color Doppler ultrasound(CDFI)in different time points after stent implantation to observation the changes of vascular bridge morphology and vascular diameter.Then evaluate the mechanism of rapamycin-eluting biodegradable magnesium alloy stent in vein graft remodeling.Blood flow velocity,blood viscosity and vessel diameter were measured at different time points,with which the shear stress was calculated according to the Poiseuille's law.The role of stent in vascular remodeling was further analyzed from the hemodynamics.Histological specimens were obtained at different time.H&E staining,elastic fiber staining,and immunohistochemical staining were used to study the inhibiton of rapamycin-eluting BMAS on vein graft stenosis.Finally,the protein expression of differentially expressed protein was analyzed by TMT-labeled relative quantification method.The possible pathway was enriched and the protein interaction network was drawn,which provided a certain direction for further research.Results:1.DSA image measurements showed that the loss of lumen diameter of graft vein anastomosis in the modified balloon injury vein graft group was greater than the control group which was without balloon injury(1 month after surgery,proximal anastomosis:0.73±0.31 mm vs.0.27±0.10 mm,p=0.005;distal anastomosis:0.67±0.31 mm vs.0.20±0.16 mm,p=0.009).The hyperplasia ratio of neointimal area(Neointima area/Internal Elastic Lamina)of balloon injury vein-graft group was significantly higher than the control group at 1 month(0.30±0.07 vs.0.17±0.13,p=0.032).2.The implantation of rapamycin-eluting BMAS can significantly reduced the lumen diameter loss of anastomosis.The lumen diameter loss of proximal anastomosis in BMAS implantation group was 0.13±0.20 mm at 1 month after surgery,while it was 0.72±0.27mm in balloon injury vein-graft group at the same time,p=0.025.3.The implantation of rapamycin-eluting BMAS can improve hemodynamics of anastomosis,reducing the shearing force of blood flow.The shear stress of proximal anastomosis and distal anastomosis in BMAS implantation group were 10.30±4.09dyn/cm~2 and 11.02±4.50 dyn/cm~2 respectively 1 month after surgery.Which were similar to the shear stress of normal abdominal aorta(9.68±4.18 dyn/cm~2).While the result in control group was different,The shear stress of proximal anastomosis(18.81±6.57 dyn/cm~2)and distal anastomosis(17.94±4.41 dyn/cm~2)were significantly higher than number of normal abdominal aorta(8.25±2.67 dyn/cm~2),there are significant differences between groups(p=0.001).4.Histological examination showed that the neointimal area in BMAS implantation group was less than that in control group without stent implantation.They are 1.47±0.47mm~2 and 2.63±0.58mm~2 at 2 month(p=0.026),1.60±0.53mm~2and2.72±0.38mm~2 at 4 month(p=0.040)respectively.The hyperplasia ratio of neointimal area(Neointima area/Internal Elastic Lamina)of control group was always higher than BMAS implantation group.The result of 4 month were 0.39±0.06 and 0.27±0.03,p=0.030.PCNA immunohistochemistry confirmed that rapamycin-eluting BMAS significantly inhibited cell proliferation compared to the control group(ratio of PCNA-positive cells in the control group and stent groups:0.34±0.03 vs.0.19±0.03,p=0.001).Evans Blue test results showed the re-endothelialization was inhibited by rapamycin-eluting BMAS at 1month,While with the release of the drug and the degradation of the scaffold,the re-endothelialization process was accelerated and there was no statistical difference between two groups.Conclusion:1.Rabbit balloon injury jugular vein-abdominal aortic graft model can reflect pathological state of vessel bypass grafting,which also can be used for stent implantation.This model could be an ideal experimental platform to evaluate enendovascular treatment for vein graft faliure.2.With the help of color doppler ultrasound,we observed that the rapamycin-eluting BMAS maintain the morphological stability of vein graft,improve venous hemodynamics,reduce local blood flow shear force,which make the vein graft in a normal blood shear force environment.3.Rapamycin-eluting BMAS can effectively brace the stenosis anastomosis of vein graft in early stage.Meanwhile,BMAS inhibited the proliferation of vascular smooth muscle cell,decreased lumen diameter loss and the hyperplasia ratio of neointimal area.4.Rap1 signaling pathway,cell adhesion molecules(CAMs)pathway,Ras signaling pathway,PI3K-Akt signaling pathway,ITGB2,MMP1,Loc10008973 may be related to the remodeling of vein graft with rapamycin-eluting BMAS,which can be used as the basis for further research. |
PDF Full Text Request