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出内皮祖细胞（EPC），并将其接种到脱细胞猪髂血管中。EPC接种移植物作为绵羊颈动脉间置移植物保持通畅130天（非接种移植物在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舒张。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。除了鉴定临床上可行的细胞来源外，工程化软组织如TEPV需要具有各向异性机械性能的支架，其经历大的变形（用当前的PGA/PLLA非织造物不可能），并具有可控的生物降解和细胞粘附特性。作为满足这些设计标准的下一步，瓦格纳实验室最近合成了一系列聚（酯-氨基甲酸酯）脲（PEUU），包括以各种比例与I型胶原结合，以增强细胞附着并提高生物降解速率。静电纺丝PEUU支架也已产生具有与天然肺动脉瓣显著相似的双轴机械性质，包括经受大的生理应变和显著的机械各向异性的能力。此外，已经开发了一种新的细胞微整合技术，该技术允许在制造时将细胞直接成功整合到支架中，消除了细胞渗透问题。这些令人鼓舞的结果表明，ES-PEUU支架微集成与EPCs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单个机械因素的策略组合-周期性弯曲、应变和流动，以优化EPC接种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机械各向异性来为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支架的机械各向异性、层和孔结构以及EPC接种的TEPV瓣叶应用的细胞整合。具体目标2 -使用具体目标1的优化PEUU支架，在模拟生理条件下在完整TEPV中进行关键的体外“放大”研究。具体目标3 -使用单个瓣叶模型评价EPC接种的ES-PEUU支架的体内性能。

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.