MULTILAYER VASCULAR GRAFTS BASED ON COLLAGEN-MIMETIC HYDROGELS

描述(申请人提供)：开发现成的小口径血管移植物的一个主要障碍是实现支架的快速内皮化，同时将血栓形成、内膜增生和机械故障的风险降至最低。由于血小板聚集和平滑肌细胞增殖可能是通过控制内皮细胞的生长和表型来调节的，因此开发能够指导适当的内皮细胞行为的材料将对小血管的修复和替换产生重大影响。然而，促进移植物内皮化的基质特性可能与那些适合维持成人血管相关负荷的特性不一致。为了解决这一局限性，我们建议制造多层水凝胶-电纺网状支架，其中水凝胶层提供诱导快速内皮化的局部环境，而电纺网状套管提供整体强度、顺应性匹配和缝合保持。因此，每个组件都可以单独调整，以在不损害其他设计目标的情况下实现更好的结果。我们建议通过使用胶原模拟蛋白Scl2.28(Scl2)来产生新型生物活性水凝胶，从而绕过与天然生物聚合物凝胶相关的限制。Scl2是一种新近发现的蛋白质，它具有天然胶原蛋白的三螺旋结构特征，但缺乏胶原蛋白的细胞黏附、细胞因子结合和酶裂解位点。在目前的工作中，我们将1？1和？2？1黏附位点引入到“亲本”Scl2中，以提供一种EC相互作用的机制，同时保持与Scl2相关的低血小板聚集。基于Cl2的水凝胶配方可以诱导所需的细胞行为，将被用于制造用不可降解的电纺网状“袖子”加固的多层血管移植物，其设计具有与天然冠状动脉相似的机械性能。目的1.鉴定能促进血管移植物快速内皮化(黏附、迁移、静止表型)的PEGDA-Scl2组合物，同时保持Scl2蛋白的非血栓形成性质。目的2.通过电纺聚氨基甲酸乙二醇酯(PU)套管增强水凝胶，制备具有临床相关力学性能(破裂压力、缝合保持强度、顺应性)的多层血管移植物。目的3.评价复合移植物各成分的生物相容性和生物稳定性。目的4.在尤卡坦小型猪模型中评价植入后的多层移植物作为颈动脉移植物的作用。在5年期结束时，我们将在临床前动物研究中评估这些新管道，并展示它们作为现成、小口径血管移植物的潜在用途。从根本上讲，这一系列杂化材料将提供工具来阐明内皮化过程，这对许多心血管设备的临床成功至关重要。此外，PEGDA-SCL2凝胶对生物活性和模数的控制，再加上通过将不同的整合素结合基序整合到SCL2中来靶向一系列不同类型细胞的能力，将形成一个强大的平台，为广泛的生物医学应用创造新的生物活性材料。

DESCRIPTION (provided by applicant): A major roadblock in the development of off-the-shelf, small-caliber vascular grafts is achieving rapid endothelialization of the scaffold while minimizin the risk of thrombosis, intimal hyperplasia, and mechanical failure. Given that platelet aggregation and smooth muscle cell proliferation may be mediated by controlling endothelial cell (EC) growth and phenotype, the development of materials that direct appropriate EC behavior would have a significant impact on small vessel repair and replacement. However, matrix properties which promote graft endothelialization may not be consistent with those appropriate to sustain the loads associated with adult vasculature. To address this limitation, we propose to fabricate multilayered hydrogel-electrospun mesh scaffolds in which a hydrogel layer provides a local environment inductive of rapid endothelialization and an electrospun mesh sleeve provides bulk strength, compliance matching, and suture retention. Thus, each component can be individually tuned to achieve improved outcomes without detriment to other design goals. We propose to circumvent the limitations associated with native biopolymer gels by generating novel bioactive hydrogels using the collagen-mimetic protein Scl2.28 (Scl2). Scl2 is a recently discovered protein which has the triple helical structure characteristic of native collagen but lacks collagen's array of cell adhesion, cytokine binding, and enzyme-cleavage sites. For the present work, we have introduced ¿1¿1 and ¿2¿1 adhesion sites into the "parent" Scl2 to provide a mechanism for EC interactions while maintaining the low platelet aggregation associated with Scl2. Scl2-based hydrogel formulations that induce desired cell behaviors will be utilized in the fabrication of the multilayer vascular graft reinforced with non-degradable electrospun mesh "sleeves" designed to have mechanical properties similar to native coronary arteries. Aim 1. Identify PEGDA-Scl2 compositions that promote rapid endothelialization of the vascular graft (adhesion, migration, quiescent phenotype) while maintaining the non-thrombogenic nature of Scl2 proteins. Aim 2. Fabricate a multilayer vascular graft with clinically-relevant mechanical properties (burst pressure, suture retention strength, compliance) by reinforcing hydrogels with electrospun polyurethane sleeves. Aim 3. Assess biocompatibility and biostability of each component of the composite graft. Aim 4. Evaluate multilayer grafts in vivo after implantation as carotid grafts in a Yucatan miniature pig model. At the end of the 5 year period, we will have evaluated these new conduits in preclinical animal studies and demonstrated their potential utility as off-the-shelf, small-caliber vascular grafts. From a fundamental perspective, this family of hybrid materials will provide the tools to elucidate endothelialization processes critical to the clinical success of numerous cardiovascular devices. Furthermore, the control over both bioactivity and modulus afforded by PEGDA-Scl2 gels, combined with the ability to target a range of different cell types by incorporating different integrin binding motifs into Scl2, will form a powerful platform in the creation of new bioactive materials for a wide range of biomedical applications.