新型非载药型涂层修饰可降解镁基血管支架的构建及其对血管重塑的作用机制研究

Magnesium Alloys is emerging as a class of ideal biomaterials for biodegradable vascular stents application. However, recent clinical trials revealed the late negative vascular remodeling problem of the present drug-eluting magnesium alloy stents, which has posed the foremost obstacle towards its clinical application. In consideration of the drawbacks of the current vascular scaffolds and the drug-eluting coating approach, the applicant proposed an innovative “three-in-one” functional surface modification strategy for magnesium alloy stent, namely, a combination of great biocompatibility, controlled degradation and adaptive function .Through the engineering of surface micro-/nano-scale morphology and subsequently the incorporation of bioactive molecule, this novel non-drug-eluting coating is expected to control magnesium degradation while at the same time promoting early re-endothelialization, in order to take full advantages of magnesium alloys as stent platform as well as the therapeutic effect of magnesium ions. Furthermore, this research project will focus on a systematic investigation of the effect of this novel non-drug-eluting magnesium alloy stent on the vascular remodeling process and the underlying cellular and molecular mechanism. Meanwhile, through in vitro and in vivo experiments, we will study and elucidate the correlation between the vascular remodeling and the dynamic process of scaffolds degradation, re-endothelialization and the function of endothelial cells, as well as the influence and mechanism of the vascular compliance recovery on the positive vascular remodeling process. This study is aimed to promote the development and clinical application of next-generation biodegradable vascular stents.

医用镁合金是构建生物可降解血管支架的理想材料之一，但目前镁基药物洗脱支架预临床实验的结果显示存在植入后远期血管负性重构这一阻碍其用于临床的主要问题。基于现存支架及载药涂层的缺陷和不足，申请者创新性地提出了“生物相容性、降解可控性、功能适配性”三位一体的镁合金支架表面功能化改性设计思路，拟通过镁合金表面适宜的微纳形貌调控复合生物活性分子修饰的策略，构建可调控镁降解兼具促进早期再内皮化功能、生物相容性优异的非载药型涂层，从而最大化地发挥镁金属作为支架基体的优势和镁离子的临床疗效。同时，对于制备的非载药型功能涂层修饰的镁合金支架，本课题将着重于其对血管重塑的影响及相关细胞和分子层面的机制研究，通过体内外实验阐明支架降解动态进程、再内皮化进程与血管重塑之间的关系及其内在机制、以及血管顺应性的恢复对血管正性重塑的影响机制。课题成果有望促进和推动新一代可降解血管支架的开发和临床应用。

本课题针对传统药物洗脱支架的释药涂层导致内皮化修复延迟继而引发中远期再狭窄等临床问题，提出可降解镁基血管支架的“生物相容性、降解可控性、功能适配性”的三位一体的新型非载药涂层新策略，设计合成并表征了短肽REDV接枝的手性水凝胶高分子，构筑了表面适宜微纳形貌复合生物活性分子修饰的仿生功能涂层，并分别研究了HUVEC和SMC在上述仿生复合纳米层表面的粘附、铺展及增殖行为。REDV引入凝胶纤维后，细胞膜上具有特异性识别REDV受体的血管内皮细胞可在混合了D-R的凝胶薄膜上粘附和增殖，实现了对内皮细胞的选择性粘附作用。本项目还系统研究了镁合金表面仿生微纳形貌在降解环境下的内皮细胞和血管平滑肌细胞的应答行为，完成了镁合金JDBM表面亚微米/微米范围粗糙形貌的制备和表征，揭示了Mg2+和表面粗糙形貌对血管细胞的双重影响机制，优选出促进内皮细胞增殖，抑制平滑肌细胞增殖的粗糙度范围，研究显示粗糙度Sa≥1.0μm的镁合金样品可促进内皮细胞的增殖及一氧化氮释放等功能，同时抑制了平滑肌细胞的增殖，为镁合金支架表面实现快速内皮化提供了一种解决方案。本项目进一步研究了镁合金表面铜掺杂PDA纳米涂层对镁基底降解行为、血管内皮细胞和平滑肌细胞应答行为的影响，完成镁合金JDBM表面聚多巴胺负载铜功能涂层的制备、表征及其细胞相容性的研究，并进行了聚多巴胺负载铜修饰的JDBM心血管支架的动物实验，将支架分别植入动物体内 1、2、4月，取出后以X射线显微镜对支架形貌进行三维重构，通过DSA、 IVUS和OCT检测显示支架内通畅，未发现血栓形成。上述研究结果有力证明了该非载药型仿生功能涂层设计和构筑的科学性和有效性，为实现支架降解及生物功能与血管正性重构相匹配提供了新思路，同时阐明了新型功能涂层对血管相关细胞应答的作用及其对内皮功能及血管重构的影响，并探索了其可能的内皮化规律和分子调控机制。