Vascular endothelium-supporting materials: Understanding the structural and physicochemical requirements.

自体血管移植的小直径血管置换在许多患者中由于缺乏合适的移植组织而受到限制。先前对小直径血管的组织工程血管移植的尝试几乎没有临床影响，在机械稳定性和生物学性能上都失败了。这些失败与人类内皮细胞（ECs）对移植物材料性质的反应缺乏基本知识密切相关。该项目的重点是详细和系统地研究基于聚氨酯的改进血管假体的材料特性和生物学要求，这种假体支持快速内皮化，并具有足够的机械性能来替代体内受损的血管。我们项目的主要假设是聚合物支架与ec的有效定植取决于材料的特定结构特性，并且可以通过它们的修饰来控制。第二个假设是，通过使用细胞吸引涂层，有可能增强支架的内皮化支持性能。为了验证这些假设，将追求以下主要目标：(1)系统地研究聚合物支架特性（结构（纤维与多孔）、纤维大小、孔径、孔隙度、支架厚度等）对支架内皮化的影响，并在2D和3D中进行广泛的物理化学分析。(2)生物活性涂层（包括聚多巴胺、聚酪氨酸、聚苯丙氨酸和聚乙烯苯胺，以及涉及肽REDV、YIGSR、IKVAV、CAG的双重涂层）的表面修饰，并详细研究其对支架与血管细胞定殖的影响。(3)小管移植物的功能评估，包括(a)静态和动态条件下的血液相容性和血栓形成性分析；(b)评估三种预内皮化方法：磁性内皮细胞（EC）在移植物管腔表面播种，静态细胞播种和灌注播种；(c)血流条件下内皮细胞对炎症刺激的反应分析。(4)在体内羊模型中验证体外结果，以测试与原始聚氨酯对照支架相比，改性管状支架的内皮化和通畅性是否得到改善。对表面细胞相互作用的分析，以及涂层对内皮化过程的影响，将导致在材料工程领域产生一个庞大、详细的新知识数据库。由于确定了血管细胞有效定植材料所需的要求和程序，该项目也将有助于改进未来血管替代品生产的技术，允许预测和翻译其他生物相容性聚合物材料。

Small-diameter vessel replacement by autologous vessel transplantation is limited by the low availability of suitable graft tissue in many patients. Previous attempts at tissue-engineered vascular grafts for small diameter vessels had little clinical impact, failing in mechanical stability or in biological performance. These failures have been closely related to the fact that there is an insufficient basic knowledge regarding the response of human endothelial cells (ECs) to the properties of graft materials. In the focus of this project are the detailed and systematic investigations of the material properties and the biological requirements for development of improved vascular prostheses based on polyurethane, which support rapid endothelialization and possess adequate mechanical properties to replace damaged vessel in vivo. The main hypothesis of our project is that effective colonization of polymeric scaffolds with ECs depends on the specific structural properties of the material and can be controlled by their modifications. Secondary hypothesis is that by using cell-attracting coating, it is possible to enhance the endothelialization-supporting properties of scaffolds.To test these hypotheses, the following main aims will be pursued:(1) Systematic investigation of the effect of polymer scaffold properties (structure (fibrous vs porous), fiber size, pore size, porosity, scaffold thickness, among others) on the scaffold endothelialization and the extensive physicochemical analyses in 2D and 3D.(2) Surface modifications with bioactive coatings (including polydopamine, polytyrosine, polyphenylalanine and polyethylphenylamine, as well as dual coatings involving peptides REDV, YIGSR, IKVAV, CAG), and the detailed investigation of their effect on the colonization of scaffold with vascular cells.(3) Functional evaluation of the tubular grafts, including (a) analyses of hemocompatibility and thrombogenicity under static and dynamic conditions; (b) evaluation of three pre-endothelialization approaches: magnetic endothelial cell (EC) seeding on the luminal surfaces of the grafts, static cell seeding and perfusion seeding; and (c) analysis of endothelial response to inflammatory stimuli under flow conditions.(4) Validation of in vitro results in the in vivo sheep model to test for improved endothelialization and patency of modified tubular scaffolds as compared with control scaffolds of pristine polyurethane.The analysis of surface-cell interactions, and of the effect of coating on the endothelialization process will result in generating a large, detailed database of new knowledge in the field of material engineering. Thanks to determining the requirements and procedures needed to effectively colonize the material with vascular cells this project will also contribute to an improved technology for the future production of blood vessel substitutes, allowing prediction and translation also to other biocompatible polymeric materials.