心血管疾病是人类常见的重大疾患之一，直径<6mm的小口径人工血管材料虽已研究多年，但移植后仍会出现再狭窄等问题，这主要与血管平滑肌细胞(SMCs)过度增殖有关。本项目拟从调控血管再生的microRNA出发，构建新型血管再生活性材料。以壳聚糖偶联选择性多肽(REDV或VAPG)为载体包载microRNA成纳米粒子，并负载于以聚乙二醇-b-聚(丙交酯-co-己内酯)等为原料、由同轴电纺等方法制备的多层超细纤维膜(管)中。使内层和中层分别定位负载miR-126和miR-145，以定时定位调控血管内皮细胞(ECs)和SMCs，促进血管再生初期快速内皮化、中期稳定性和长期维持血管通畅的能力。重点研究壳聚糖载体及多层电纺膜对miRNA的负载方法、生物力学环境下的释放行为和控制因素，以及体外和体内定位、定时调控ECs和SMCs及相互作用的影响机制。为构建新型原位诱导血管再生材料提供新思路和理论基础。

Cardiovascular diseases seriously threaten human's health and create an important demand for small-diameter (<6mm) vascular grafts. Due to the limitation of autografts and allografts, development of tissue engineering vascular grafts is a promising solution. Although many relevant studies on small-diameter vascular scaffolds have been done, it is still difficult to keep long-term patency, because restenosis usually happens after implantation. One of the most important factors causing restenosis is intimal hyperplasia by the excessive proliferation of vascular smooth muscle cells (SMCs). Besides, rapid endothelialization is also important. Therefore, it is necessary to promote endothelialization and inhibit SMC hyperproliferation during the regeneration of blood vessels. In this project, we propose a novel method to prepare bioactive small-diameter vascular grafts by loading microRNAs to regulate vascular regeneration. It was reported that angiogenic growth factors such as vascular endothelial growth factor (VEGF) modulate vascular endothelial cell (EC) proliferation, migration and adhesion. MicroRNA-126 (miR-126) could inhibit production of endogenous VEGF repressors such as Spred-1 within ECs and promote VEGF signaling. On the other hand, SMC excessive proliferation is modulated by many cytokines, and one of them is platelet-derived growth factor-bb (PDGF). It was reported that miR-145 could inhibit PDGF-induced SMC proliferation and migration through targeting KLF5. In addition, the peptide sequences Arg-Glu-Asp-Val (REDV) and Val-Ala-Pro-Gly (VAPG) are known to bind preferentially to ECs and SMCs, respectively. Thus, multi-layered (2 or 3) electrospun membranes or tubes consisted of poly(ethylene glycol)-b-poly(L-lactide-co-ε-caprolactone) and other related copolymers will be developed, while chitosan nanoparticles loading microRNAs (miR-126 and miR-145) will be encapsulated in inner and middle layers (or outer of double-layers) of the multilayered electrospun fibers, respectively for spatio-temporal control of EC and SMC growth. Also, chitosan nanoparticles, the inner and middle layers will be surface-functionalized by targeting peptides (REDV and VAPG) to promote binding to ECs and SMCs, respectively. The microRNA encapsulation and transfection efficiency will be controlled by the chitosan nanoparticle physiochemical properties and the morphology of electrospun membranes. The spatio-temporal modulating mechanism of EC and SMC growth, the encapsulation approaches of chitosan nanoparticles within electrospun membranes and the release behaviors under biomechanical stimulation will be focused on. In vivo replacement experiments in an animal model using the small-diameter vascular grafts will be carried out to evaluate the in situ regeneration of the vascular tissue. The investigation of bioactive vascular grafts based on microRNAs will provide new strategies and fundamental theories for the small-diameter vascular reconstruction.