Biomechanical Optimization of TE Heart Valves

描述（由申请人提供）：最近，Kaushal等人从绵羊外周血中分离内皮祖细胞（EPCs），并将其植入去细胞化的猪髂血管中。epc种子移植物作为颈动脉插入移植物在绵羊中保持专利130天（非种子移植物在15天内闭塞），并表现出与天然颈动脉相似的收缩活性和一氧化氮介导的血管松弛。Sales等人已经证明EPCs具有提供瓣膜间质和内皮细胞功能的潜力，证明了EPCs作为TEPV的单一自体细胞来源的潜力。除了确定临床可行的细胞来源外，工程软组织如TEPV需要具有各向异性力学性能的支架，这些支架可以承受大的变形（目前的PGA/PLLA非织造布不可能实现），同时具有可控的生物降解和细胞粘附特性。为了实现这些设计标准，Wagner实验室最近合成了一系列聚（酯-聚氨酯）脲（PEUUs），包括以不同比例与I型胶原蛋白结合，以增强细胞附着并提高生物降解率。静电纺丝PEUU支架也被制成具有与天然肺动脉瓣非常相似的双轴力学性能，包括承受大生理应变的能力和明显的力学各向异性。此外，一种新的细胞微整合技术已经被开发出来，可以在制造时成功地将细胞直接整合到支架中，从而消除了细胞渗透问题。这些令人鼓舞的结果表明，与EPCs微集成的ES-PEUU支架可以作为成功的TEPV支架。我们假设，可以确定与心脏瓣膜相关的各个机械因素（循环挠度、应变和流量）的战略组合，以优化EPC种子TEPV的ECM合成、组织和机械性能。此外，我们假设使用新型弹性支架可以通过允许大应变和高度可控的力学各向异性来为TEPV设计增加临界自由度。这些假设将通过以下具体目标来解决：具体目标1 -优化ES-PEUU支架机械各向异性，层和孔隙结构，以及epc种子TEPV小叶应用的细胞整合。特异性靶2 -使用特异性靶1的优化PEUU支架，在模拟生理条件下对完整的TEPV进行关键的体外“放大”研究。特异性目标3 -使用单叶模型评估epc种子ES-PEUU支架在体内的功能。

DESCRIPTION (provided by applicant): Recently, Kaushal et al. isolated endothelial progenitor cells (EPCs) from the peripheral blood of sheep and seeded them onto decellularized porcine iliac vessels. EPC-seeded grafts remained patent for 130 days as a carotid interposition graft in sheep (non-seeded grafts occluded within 15 days), and exhibited contractile activity and nitric-oxide-mediated vascular relaxation similar to native carotid arteries. Sales et al. have demonstrated that EPCs have the potential to provide both valvular interstitial and endothelial cellular functions, demonstrating the potential for EPCs to serve as a single autologous cell source for TEPV. In addition to the identification of clinically feasible cell sources, engineered soft tissues such as the TEPV require scaffolds with anisotropic mechanical properties that undergo large deformations (not possible with current PGA/PLLA non-wovens) coupled with controllable biodegradative and cell-adhesive characteristics. As a next step in fulfilling these design criteria, the Wagner lab has recently synthesized a family of poly (ester-urethane) ureas (PEUUs), including combination with type I collagen at various ratios to enhance cell attachment and increase biodegradation rates. Electrospun PEUU scaffolds have also been produced with biaxial mechanical properties that are remarkably similar to the native pulmonary valve, including the ability to undergo large physiologic strains and pronounced mechanical anisotropy. Moreover, a novel cell micro-integration technique has been developed that allows for successful integration of the cells directly into the scaffolds at the time of fabrication, eliminating cellular penetration problems. These encouraging results suggest that ES-PEUU scaffolds micro-integrated with EPCs can serve as successful TEPV scaffolds. We hypothesize that strategic combinations of individual mechanical factors relevant to heart valves-cyclic flexure, strain, and flow-can be determined that optimize ECM synthesis, organization, and mechanical properties of EPC seeded TEPV. Moreover, we hypothesize that the use of novel elastomeric scaffolds can add a critical degree-of-freedom for TEPV designs by allowing for large strains and highly controllable mechanical anisotropy. These hypotheses will be addressed by the following specific aims: Specific Aim 1 - Optimize ES-PEUU scaffold mechanical anisotropy, layer and pore structures, and cellular integration for EPC-seeded TEPV leaflet applications. Specific Aim 2 - Using optimized PEUU scaffolds of specific aim 1, conduct critical in-vitro "scale-up" studies in intact TEPV under simulated physiological conditions. Specific Aim 3 - Evaluate the EPC-seeded ES-PEUU scaffold's ability to perform in-vivo using a single leaflet model.