生物活性人工血管体内降解及血管再生调控

Electrospun PCL vascular graft was well known for its good biocompatibility, but one of its drawbacks is that the inherently small pore size and slow degradation rate would most likely lead to calcification in the late phase of implantation. Nerve fibers, which can effectively maintain the physiological function of vascular smooth muscle and inhibit pathological smooth muscle cell proliferation and calcification, play an important role in blood vessel regeneration. While electrospun PCL vascular graft can't effectively promote reconstruction of nerve fibers, because it has no bioactivity. Based on the issue above, our study mainly focus on the bioactivity modification and degradation manipulation for vascular grafts with the structure desigin. Regarding the bioactivity modification，the inner layer was prepared through co-electrospinning PCL and silk fibroin nanoparticles A loaded with VEGF to accelerate endothelialization；the middle layer was modified to guide oriented regeneration of smooth muscle cells via co-electrospinning PCL and silk fibroin nanoparticles B loaded with PDGF-BB, electrospraying PEO microparticles were utilized to increase porosity of the middle layer, and an high-speed rotation collector was use to align the nanofiber；the outer layer was prepared via electrospinning PLGA and co-electrospinning PCL and silk fibroin nanoparticles C loaded with Netrin-1 to improve nerve fibers growth，which can inhinbit pathological smooth muscle cell proliferation and calcification and also provide mechanical support at the same time. Furthermore, given the fact that γ radiation can induce PCL main chain scission reactions and crosslinking, we used it to adjust the degradation rate of PCL so that it matches the speed of tissue regeneration. The effect of the bioactivity and degeration of the vascular grafts for vascular regeneration was investigated through rabbit carotid artery implantation.

静电纺丝制备的PCL血管材料具有良好的生物相容性，但其较小的纤维孔径和较慢的降解速度易导致植入后期发生平滑肌钙化。血管神经能够有效维持平滑肌的正常生理功能、防止其发生病理增生与钙化，但单纯电纺PCL材料没有生物活性，不能有效促进血管神经纤维重建。基于上述问题，我们在血管材料孔结构设计的基础上，对其进行活性修饰和降解调控，以达到改善和促进血管再生的目的。在活性修饰方面，我们拟通过混纺PCL与负载生物活性因子的丝素蛋白纳米颗粒，使内层缓释VEGF，加速内皮化；中层缓释PDGF-BB，同时配以大孔和纤维取向结构，促进和诱导平滑肌取向再生；外层缓释Netrin-1，促进血管神经纤维重建。在材料降解方面，基于γ射线对PCL分子链的断链与交联作用，我们在安全剂量范围内通过γ射线调控材料体内降解，使之与血管再生速度相匹配。通过兔颈动脉血管移植研究血管材料的生物活性与降解对血管再生的调控作用。

临床对于小口径人工血管（< 6 mm）需求巨大，但是尚无理想的产品可以使用，因此，需要研发性能优良的小口径人工血管以满足临床需求。本项目着重对小口径血管材料的孔结构设计、功能修饰和降解性三个方面加以研究，以期为构建理想的小口径人工血管材料奠定基础。在结构设计方面，我们以电喷聚乙二醇（PEO）微球作为致孔剂，制备了中层致孔的三层结构的静电纺丝聚己内酯（PCL）血管材料，植入兔颈动脉后，大量的巨噬细胞快速地迁移进了致孔层，释放了单核细胞趋化因子-1（MCP-1）和血管内皮细胞生长因子（VEGF），有效地促进了血管内皮和平滑肌的再生。在功能修饰方面，我们利用基因融合技术构建了融合蛋白VEGF-HGFI，该蛋白能够在电纺PCL材料表面通过疏水的相互作用形成VEGF蛋白涂层，该涂层改善了PCL血管材料的亲水性和血液相容性，植入大鼠腹主动脉后能够显著促进支架材料的内皮化和组织再生；在降解调控方面，我们通过对纺技术将PCL与可快速降解的（聚对二氧环己酮）PDO复合，制备了PCL/PDO复合纤维血管材料，体内、外降解实验证实PDO纤维的复合加速了支架材料的降解速度，该复合材料植入大鼠腹主动脉后，显示了良好的通畅性，PDO纤维的降解没有引起动脉瘤的发生，但PDO纤维降解产生了额外的空间促进了平滑肌细胞在血管壁中的再生。本项目所取得的研究成果为新一代小口径人工血管的构建提供了重要的参考价值。