Biomechanical Optimization of TE Heart Valves

描述(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)，将其接种于脱细胞猪髂骨血管上。EPC种子移植物作为绵羊颈动脉间置移植物保持开放130天(非种子移植物在15天内闭塞)，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。销售等。已证明内皮祖细胞具有同时提供瓣膜间质和内皮细胞功能的潜力，显示了内皮祖细胞作为TEPV的单一自体细胞来源的潜力。除了确定临床上可行的细胞来源外，TEPV等工程化软组织还需要具有各向异性机械性能的支架，这些支架具有大变形(目前的PGA/PLLA无纺布不可能)，并具有可控的生物降解性和细胞粘附性。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-氨酯)尿素(PEUU)，包括以不同比例与I型胶原结合，以增强细胞附着和提高生物降解率。电纺PEUU支架的双向力学性能与天然的肺瓣膜非常相似，包括能够承受较大的生理应变和明显的机械各向异性。此外，开发了一种新的细胞微集成技术，允许在制造时成功地将细胞直接整合到支架中，消除了细胞渗透问题。这些令人鼓舞的结果表明，与EPC微整合的ES-PEUU支架可以作为成功的TEPV支架。我们假设，与心脏瓣膜相关的单个机械因素的战略性组合--循环弯曲、应变和流量--可以确定优化EPC种子TEPV的ECM合成、组织和机械性能。此外，我们假设，通过允许大应变和高度可控的机械各向异性，新型弹性支架的使用可以增加TEPV设计的临界自由度。这些假设将通过以下具体目标来解决：具体目标1-优化EPC种子TEPV小叶应用的ES-PEUU支架的力学各向异性、层和孔结构以及细胞集成。特定目标2-使用特定目标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。具体目标3-使用单叶模型评估EPC种植的ES-PEUU支架在体内的能力。

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.