Biological Vascular Grafts

描述（由申请人提供）：寻找能够在小直径范围内发挥作用的基于生物学的动脉移植物已经进行了几十年，并且在此期间已经克服了多个障碍。近年来，一些研究者已经克服了先前机械强度不足的限制，但自体动脉培养时间的延长限制了广泛的适应或实验。Niklason在2003年报道了脱细胞工程动脉的可行性，我们在之前的授权期中表明，组织工程和脱细胞的移植物可以在体内长期发挥作用，从而将所需的培养时间缩短到4周的自体内皮细胞培养。因此，血管组织工程的最后一个重大障碍是生产不需要培养时间的组织为基础的移植物，并且可以在没有自体内皮细胞层的情况下抵抗血栓形成。该提案的总体目标是开发非细胞基础的方法来抑制去细胞化工程动脉的凝血和血小板活化，从而使功能性动脉移植物可以“现成”获得。在这个修订后的竞争性更新中，我们的方法是通过多点干预来抑制凝血级联和血小板粘附。通过在移植物表面加入高密度的共价结合的肝素，我们可以抑制凝血因子XIIa、Xa和IIa，从而减少血块的形成和血小板的粘附和聚集。通过在移植物腔内涂覆血小板反应蛋白2-零基质，可以减少血小板粘附，并结合肝素抑制凝血酶，可以抑制血栓的形成。血小板spondin2-零基质也可能比含有血小板spondin2的天然胶原基质更能支持内皮粘附和生长，从而更好地实现宿主内皮化。这些新的抗凝策略将通过一套全面的体外试验和大型动物体内研究，与自体内皮细胞抑制脱细胞工程动脉移植物血栓形成的能力进行比较。

DESCRIPTION (provided by applicant): The search for a biologically based arterial graft that could function at small diameters has gone on for several decades, and multiple hurdles have been overcome during that time. In recent years, the previous limitation of inadequate mechanical strength has been overcome by several investigators, but extended times for autologous artery culture have limited widespread adaption or experimentation. Niklason reported in 2003 the feasibility of decellularizing engineered arteries, and we showed in the previous granting period that tissue engineered and decellularized grafts can function long-term in vivo, thereby shortening the required culture time to 4 weeks of autologous endothelial cell culture. Hence, one of the last significant hurdles in vascular tissue engineering is to produce tissue-based grafts that require no culture time, and that can resist thrombosis without having an autologous endothelial cell layer. The overall goal of this proposal is to develop non-cell-based means of inhibiting coagulation and platelet activation on decellularized engineered arteries, so that functional arterial grafts may be available "off the shelf". In this revised, competitive renewal, our approach is to inhibit both the coagulation cascade and platelet adhesion by intervening at multiple points. By incorporating a high density of covalently bound heparin onto the graft surface, we should inhibit coagulation factors XIIa, Xa, and IIa, and thereby reduce clot formation and platelet adhesion and aggregation. By coating the graft lumen with thrombospondin2- null matrix, platelet adhesion should be reduced, which in combination with thrombin inhibition by heparin should inhibit clot formation. Thrombospondin2-null matrix may also support endothelial adhesion and growth more than native collagen matrix that contains thrombospondin2, enabling better host endothelialization. These novel anti-coagulation strategies will be compared, using a comprehensive set of in vitro assays as well as large animal in vivo studies, with autologous endothelium for their ability to inhibit thrombosis of decellularized, engineered arterial grafts. PUBLIC HEALTH RELEVANCE: Development of engineered arteries has advanced substantially over the past several decades, but progress has stopped short of a fully functional, off-the-shelf arterial conduit. Work in this application will build upon our progress in the last granting period, wherein we developed acellular tissue engineered matrices for use as vascular grafts. In this application, we will study the efficacy of several non-cellular modifications of the graft surface to reduce thrombogenicity, with the aim of creating a completely off-the-shelf vascular graft.