Biological Vascular Grafts

描述(申请人提供)：寻找一种可以在小直径下起作用的基于生物的动脉移植物已经持续了几十年，在此期间已经克服了多个障碍。近年来，一些研究人员已经克服了以前机械强度不足的限制，但延长自体动脉培养的时间限制了广泛的适应或实验。Nikason在2003年报道了脱细胞工程化动脉的可行性，我们在之前的授权期证明了组织工程化和脱细胞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要障碍是制造不需要培养时间的组织移植物，并且在没有自体内皮细胞层的情况下可以抵抗血栓形成。这项提议的总体目标是开发非基于细胞的方法来抑制脱细胞工程化动脉上的凝血和血小板激活，从而使功能性动脉移植物可以“现成”使用。在这项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反应和血小板黏附。通过在移植物表面加入高密度的共价结合肝素，我们应该抑制凝血因子XIIa、Xa和IIa，从而减少血栓形成和血小板黏附和聚集。通过在移植物管腔上覆盖凝血酶敏感蛋白2缺失的基质，可以减少血小板的粘附性，再加上肝素对凝血酶的抑制作用，应该可以抑制血栓的形成。与含有凝血酶原蛋白2的天然胶原基质相比，凝血酶原蛋白2缺失的基质也可能更好地支持内皮细胞的黏附和生长，从而实现更好的宿主内皮化。这些新的抗凝策略将利用一套全面的体外测试和大型动物体内研究，与自体内皮细胞进行比较，以了解它们抑制脱细胞工程化动脉移植物血栓形成的能力。

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.