A Novel VEGF Gene-coated Stent To Improve Re-endothelialization And Prevent In-stent Restenosis

BACKGROUND:Vascular stenosis caused by atherosclerosis leading to poor circulation,angina,hypoxia,stroke and myocardial infarction,has become one of the most threatening diseases in humans.Endovascular stenting is a good measure to effectively improve and treat intravascular stenosis.However,in-stent restenosis(ISR)is a common problem in clinical practice of stents,which seriously affects the prognosis of patients with stent implantation.Studies have shown that promoting stent re-endothelialization is one of the options for the prevention and treatment of ISR.Therefore,we aimed to use a novel cationic polymer gene vector SKP to carry the VEGF gene,and transfect the VEGF gene into the injured blood vessel through stent implantation for promoting re-endothelialization of damaged blood vessels and inhibiting the formation of ISR.METHOD:1.Preparation of SKP/pVEGF gene-eluting stent:Firstly,a layer of polydopamine(PDA)is coated on the surface of the bare metal stent to form a negative charge on the surface of the stent,which is beneficial to the adhesion of the positively charged cationic polymer.The premixed reduction-responsive branched poly lysine(SKP)and VEGF plasmid(pVEGF)solutions were then applied to the surface of the PDA-eluting stent by electrostatic adsorption to form a SKP/pVEGF stent.Previous trials have confirmed that SKP is a novel gene vector with good biocompatibility and ability to promote gene transfection.SKP and blank plasmid(NC)were also made into SKP/pNC stents as negative controls.2.Animal experiments:30 Japanese white rabbits weighing about 2.5 kg were randomly divided into 3 groups,SKP/pVEGF coated stent(SKP/pVEGF)group,SKP/pNC coated stent(SKP/pNC)Group and bare metal stent(BMS)groups.Stents were implanted into a suitable position of the rabbit abdominal aorta by angiography.Five rabbits were sacrificed in each group at 1 week and 4 weeks after operation,and the arteries contain stents were taken for subsequent detection.Expression of pVEGF was detected by Western Blot(WB)and VEGF immunohistochemistry.Re-endothelialization of the stent was confirmed by scanning electron microscope(SEM)and CD31 immunohistochemistry.The arterial tissue containing the metal stent was embedded in methyl methacrylate for hard tissue section.After H&E staining,the area of the neointimal in the stent was measured under a light microscope to evaluate the degree of restenosis.RESULTS:All rabbits successfully underwent stent implantation.One week after stent implantation,WB and VEGF immunohistochemistry confirmed the presence of VEGF protein overexpression in SKP/pVEGF tissues,indicating that pVEGF was successfully transfected into surrounding tissues and expressed the VEGF protein through SKP/pVEGF stent in vivo.VEGF immunohistochemistry at 4 weeks suggested that this overexpression effect has gradually disappeared.SEM observation showed that the SKP/pVEGF stent surface almost completely covered at 1 week,while the other two groups were not.At 4 weeks,the surface of the three groups of stents were all covered,but the SKP/pVEGF group was more regular and smoother than the other groups.CD31 immunohistochemistry also showed same results in the SKP/pVEGF group at 1 week and 4 weeks.The morphological analysis of the three groups of neointimal area showed no significant difference at one week.The data measured at 4 weeks were 0.353±0.070 mm2 for SKP/pVEGF,0.706±0.137 mm2 for SKP/pNC,0.615±0.078 mm2 for BMS,P<0.05.The results showed that the neointimal hyperplasia was more obvious in the negative and blank control group,and it was easier to develop ISR.CONCLUSION:SKP/pVEGF coated stent has the effect of improving the reendothelialization of stent and inhibiting the ISR formation,which has high research and clinical application prospects.