Biological Vascular Grafts

描述（由申请人提供）：数十年来一直在寻找可在小直径下发挥作用的生物基动脉移植物，在此期间克服了多个障碍。近年来，一些研究者已经克服了先前机械强度不足的限制，但是自体动脉培养的延长时间限制了广泛的适应或实验。Niklason在2003年报道了去细胞化工程化动脉的可行性，我们在之前的授权期间表明，组织工程化和去细胞化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并且可以在没有自体内皮细胞层的情况下抵抗血栓形成的组织移植物。该提案的总体目标是开发非细胞为基础的手段，抑制凝血和血小板活化的脱细胞工程动脉，使功能动脉移植物可能是“现成的”。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反应和血小板粘附。通过将高密度的共价结合肝素结合到移植物表面，我们应该抑制凝血因子XIIa、Xa和IIa，从而减少凝块形成和血小板粘附和聚集。通过用无凝血酶敏感蛋白2基质涂覆移植物管腔，应减少血小板粘附，这与肝素的凝血酶抑制相结合应抑制凝块形成。血小板反应蛋白2-空基质也可能比含有血小板反应蛋白2的天然胶原基质更支持内皮粘附和生长，从而实现更好的宿主内皮化。这些新的抗凝策略将进行比较，使用一套全面的体外试验以及大型动物体内研究，自体内皮细胞的能力，以抑制血栓的脱细胞，工程动脉移植。

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.