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

在许多患者中，通过自体血管移植进行的小直径血管置换受限于合适的移植组织的低可用性。以前尝试的组织工程血管移植物的小直径血管几乎没有临床影响，失败的机械稳定性或生物性能。这些失败与以下事实密切相关：关于人内皮细胞（EC）对移植材料特性的反应的基础知识不足。该项目的重点是详细和系统地研究基于聚氨酯的改进型血管假体的材料性能和生物学要求，该假体支持快速内皮化并具有足够的机械性能以替换体内受损血管。我们的项目的主要假设是，有效的定植与EC的聚合物支架取决于材料的特定结构特性，并可以通过其修改控制。第二个假设是，通过使用细胞吸引涂层，有可能提高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）系统研究聚合物支架性能（结构（纤维与多孔），纤维尺寸，孔径，孔隙率，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)用生物活性涂层（包括聚多巴胺、聚酪氨酸、聚苯丙氨酸和多乙基苯胺，以及涉及肽REDV、YIGSR、IKVAV、CAG的双重涂层）进行表面改性，并详细研究它们对血管细胞在支架上定植的影响。(3)管状移植物的功能评价，包括（a）静态和动态条件下的血液相容性和血栓形成分析;（B）三种内皮化前方法的评价：移植物管腔表面上的磁性内皮细胞（EC）接种、静态细胞接种和灌注接种;以及（c）流动条件下内皮对炎症刺激的反应分析。(4)在体内绵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的改善。表面-细胞相互作用的分析，以及涂层对内皮化过程的影响，将产生材料工程领域新知识的大型详细数据库。由于确定了用血管细胞有效地定殖材料所需的要求和程序，该项目还将有助于改进未来生产血管替代品的技术，从而也可以预测和转化为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.