Programable VEGF/PTX Controlled-release Segmental Covered Stent For Endothelialization Acceleration And Lumen Stenosis Prevention

Objective:Aneurysmal subarachnoid hemorrhage causes high rates of mortality and morbidity.A covered stent is an effective endovascular treatment for complicated aneurysms.However,delayed endothelialization and in-stent restenosis due to excessive proliferation of smooth muscle cell（SMC）are the main challenges to its safety.The purpose of our study was to designed a bio-functional stent covered with VEGF/PTX controlled-release electrospun fibers to achieve programmed release of vascular endothelial growth factor（VEGF）and paclitaxel（PTX）for the early promotion of stent endothelialization and long-term inhibition of stenosis caused by smooth muscle hyperplasia.The in vitro and in vivo biological safety and effectiveness of the stents were also evaluated.Methods:The VEGF/PTX programable controlled-release segmental covered stent was constructed by encapsulating PTX-loaded mesoporous silica nanoparticles（MSNs）within electrospun polylactic acid（PLA）fibers,and then VEGF was conjugated onto the surface of electrospun fiber membrane through a polydopamine reaction.The morphology and structure of nanoparticles and electrospun were characterized by Malvern laser particle size analyzer,scanning electron microscope（SEM）and transmission electron microscope（TEM）.In vitro drug release was analyzed by ultraviolet spectrophotometer and high-performance liquid chromatography（HPLC）.We cultured human umbilical vein endothelial cell（HUVEC）and human vascular smooth muscle cell（HVSMC）,and CCK-8 assay was used to analyze the effect of the novel stent on cell proliferation.A canine model of carotid artery side wall cystic aneurysm was constructed and implanted with VEGF/PTX programable controlled-release segmental cover stent.Digital subtraction angiography（DSA）was performed at the 1^st,the 4^th,and the 12^th week after stent implantation,and the occlusion rate of aneurysm and the stenosis of parent arteries were analyzed in the immediate-and mid-term follow-up.Experimental dogs were euthanized and scaffold specimens were obtained from the body for scanning electron microscopy and histopathological analysis at the 12^thweek.Results:The VEGF/PTX programable controlled-release segmental cover stent was successfully prepared.The MSN-PTX covered by the stents possessed uniform spherical morphology with a smooth surface,and the average diameter was about 100 nm.The electrospun fibers were arranged in a uniform way with the diameter of 1.26±0.64μm,and there was no significant difference in tensile strength of the stent before and after drug loading（P=0.385）.In vitro drug release analysis showed that 87.05%of VEGF was released rapidly within 3 days,while PTX released in the first 3 days accounted for only 6.8%.Besides,99.6%of PTX was released stably within 63 days.In vitro cell experiments showed that the VEGF/PTX programable controlled-release fiber membrane immersion extract promoted HUVEC proliferation on the 6^th day compared with the blank control group（386%vs.488%,P=0.039）.After we used the 21-day extracts for 6 days of incubation,HVMSC proliferation was significantly inhibited in the VEGF/PTX programable controlled-release segmental covered stent group compared to that in the blank control group（155%vs.303%,P=0.001）.Animal studies showed that compared to bare stents,the VEGF/PTX programable controlled-release segmental covered stent improved the immediate-and mid-term complete aneurysm occlusion rates（P<0.05）.Moreover,the VEGF/PTX programable controlled-release segmental covered stents also showed earlier endothelialization promotion and better lumen restenosis than normal covered stents（P=0.29）within12 weeks.Conclusion:In this study,a VEGF/PTX programable controlled-release segmental covered stent was successful prepared for the effective treatment of cerebral aneurysm disease,and the discrete release of VEGF and PTX promoted the early endothelialization and prevented in-stent stenosis.This study provided a new way to improve the biosafety of implanted covered stents for the treatment of intracranial aneurysms.