Atrial wall: a 3-D scaffold with formed microvasculature

说明(申请人提供)：心脏病仍然是发达国家的头号死因，这在很大程度上是因为目前还没有替代因心肌梗死而失去的心肌细胞的治疗方法。如何最好地在宿主体内实现早期血管形成是迄今为止限制所有工程化心脏组织成功的最重要问题。心耳是几乎每个患者都可以获得的唯一可消耗性的自体心脏组织。作为一种新的心肌梗死修复细胞来源，自体心房组织的独特之处在于它不仅在三维支架中含有自体心肌细胞，而且还具有固有的和广泛的毛细血管。在这里，我们将研究是否可以像中厚皮肤移植物一样，通过吻合(形成的宿主和移植物血管之间的吻合)来快速地重新血运重建心房组织，而不需要合成新的微血管网络。尽管我们已经证明，植入到其天然支架中的心室上的心房肌细胞至少可以存活四周，但大多数心肌细胞的丢失发生在植入后的第一周。在皮下植入模型中，将探索几种旨在改善早期血运重建的补充策略。我们将把大网膜移入皮下间隙，以检查靠近更大的动脉流入来源是否会加速或增强血管形成。然后，将探索将重新血运的组织旋转到心脏，维持其血管(大网膜)动脉供应的可能性，这是一种临床适用的方案。我们将检测局部给予血管内皮生长因子-165对早期血管形成的影响，比较水凝胶输送血管内皮生长因子-165与直接将AAV基因输送到心房补片的效果。AAV基因疗法还将用于将热休克蛋白直接输送到补片上，旨在提高心肌细胞在血运重建之前对缺血的耐受性。最后，我们将研究有效策略的综合是否允许我们在皮下床上建立第二层心房心肌细胞。我们开发了一种用于心肌基因转移的新型AAV载体，并开发了一种器官培养系统，以保持心房壁存活长达2周，以促进基因的传递。其目标是制造一种活的、动态的三维心脏结构，这种结构可以在体外进行工程设计，并在体内快速重新血运重建。利用自体成人心房心肌作为活体工程组织修复心肌梗死是一种新的生物工程概念，具有潜在的临床应用前景。

DESCRIPTION (provided by applicant): Heart disease remains the number one cause of death in the developed world, in large part because there is no current therapy to replace cardiac myocytes lost to myocardial infarction. The issue of how best to achieve early vascularization in the host is the most important problem limiting the success of all engineered cardiac tissues to date. The atrial appendage is the only expendable autologous cardiac tissue that would be available in virtually every patient. As a new cell source for myocardial infarct repair, autologous atrial tissue is unique in that it has not only autologous cardiomyocytes in a three dimensional scaffold, but also an inherent and extensive capillary microvasculature. Here we will examine whether, like a split thickness skin graft, atrial tissue could be revascularized rapidly by inosculation (anastomoses between formed host and graft vessels), without requiring synthesis of a de novo microvascular network. Although we have shown that atrial myocytes implanted on the ventricle in their natural scaffold survive to at least four weeks, most myocyte loss that occurs is in the first week post implantation. Several complementary strategies designed to improve early revascularization will be explored in a subcutaneous implant model. We will mobilize omentum into the subcutaneous space to examine whether proximity to a larger arterial inflow source would accelerate or augment vascularization. Then, the potential for rotating the re-vascularized tissue to the heart, maintaining its vascular (omental) arterial supply will be explored, a clinically applicable protocol. We will examine the effect on early vascularization of providing local VEGF-165, comparing the efficacy of hydrogel delivery of VEGF-165 to direct AAV gene delivery to the atrial patch. AAV gene therapy will also be used to deliver a heat shock protein directly to the patch, designed to increase myocyte tolerance to ischemia in the period before revascularization. Finally, we will examine whether a synthesis of efficacious strategies would allow us to build a second layer of atrial cardiomyocytes in the subcutaneous bed. We have developed a new AAV vector construct for myocardial gene transfer and also an organ culture system to keep atrial wall alive for up to 2 weeks to facilitate gene delivery. The goal is to produce a living, dynamic three-dimensional cardiac structure that can be engineered in vitro and revascularized rapidly in vivo. Making use of autologous adult atrial myocardium as a living engineered tissue for myocardial infarct repair is a novel bioengineering concept that has potential for imminent clinical applicability.