Transplantation of hearts from donation after circulatory death

心脏移植（HTx）是终末期心力衰竭的最终治疗方法，但其使用受到心脏移植的限制。 捐赠心脏的可用性。结果，大量HTx候选人在等待移植时死亡。 循环死亡后献血（DCD）为HTx提供了一个有希望的额外来源。然而，它的采用是 由于死亡过程中的强制性热缺血损伤和随后的再灌注损伤而受阻， 以及运输过程中不合适的保存方式。EVHP提供常温灌注平台 用于满意地保存DCD心脏，并提供了递送改善心功能的治疗剂的可能性。 移植前DCD心脏复苏。给予干细胞衍生的旁分泌保护， 我们的目标是确定缺血后给予干细胞的潜在疗效 分泌物（条件培养基[CM]、细胞外囊泡[EV]或工程化EV）， 在移植前回收DCD心脏，从而增加可用供体心脏的数量。我们 最近的研究报道，将MSC-CM或MSC-EV添加到储存溶液中可保护心脏移植物 使用体内小鼠HTx模型和MSC-CM恢复冷缺血后6小时冷藏后的性能- 心脏转录组谱受损。这些结果表明MSC分泌物对供体的治疗潜力 心脏保存我们已发表的工作和初步数据也表明：1）使用人MSC或其 CM可改善EVHP急性缺血/再灌注（I/R）后心功能恢复; 2）MSC-CM 防止供体心脏中的线粒体因冷缺血而受损并恢复时钟基因2期（Per 2， 在线粒体代谢调节中起作用）; 3）热缺血导致线粒体异常， 在小鼠和人DCD心脏中，Per 2降低，和4）Per 2敲低恶化 线粒体损伤和废除MSC CM介导的线粒体保存在应激过程中的肌细胞。 总的来说，我们假设缺血后使用EVHP给予MSC分泌物改善了 热缺血诱导的DCD心脏功能恶化通过Per 2引起线粒体改善。 我们期望一种使用工程EV递送Per 2的新方法将促进线粒体DNA的合成。 DCD心脏的恢复和心肌复苏。我们提出两个目标：1。测试假设，离体 使用EVHP的MSC分泌物的应用通过以下途径改善热缺血诱导的心肌损伤： DCD心脏中的线粒体保存;和2.确定Per 2在改善线粒体中的作用 在DCD心脏中的性能，并证明Per 2负载的MSC-EV对 DCD心脏。还将评估MSC衍生疗法和工程EV的转化潜力 在类似人的猪DCD心脏中。本研究结果可为临床试验提供依据 因为MSC分泌物可用于改善DCD心脏恢复，并帮助我们获得关于以下方面的机械见解： 限制DCD心脏移植中的热缺血损伤的治疗目标。

Heart transplantation (HTx) is the ultimate treatment for end-stage heart failure, but its use is limited by the availability of donor hearts. As a result, a substantial number of HTx candidates die awaiting transplant. Donation after circulatory death (DCD) offers a promising additional source for HTx. However, its adoption is hindered due to obligatory warm ischemic injury during death process and subsequent reperfusion injury, as well as unsuitable preservation modality during transport. The EVHP provides normothermic perfusion platform for satisfactory preservation of DCD hearts and offers the possibility to deliver therapeutic agents that improve resuscitation of DCD hearts prior to transplantation. Given stem cell-derived paracrine protection following myocardial ischemia, our goal is to determine potential efficacy of post-ischemic administration of stem cell secretions (conditioned medium [CM], extracellular vesicles [EVs], or engineered EVs) using the EVHP on recovery of DCD hearts prior to transplantation, thereby increasing the number of available donor hearts. Our recent studies have reported that adding MSC-CM or MSC-EVs to storage solution protected heart graft performance after 6h-cold storage using an in vivo mouse HTx model and MSC-CM restored cold ischemia- impaired cardiac transcriptome profile. These results suggest therapeutic potential of MSC secretions on donor heart preservation. Our published work and preliminary data have also shown: 1) using human MSCs or their CM improved heart functional recovery in the EVHP following acute ischemia/reperfusion (I/R); 2) MSC-CM prevented mitochondrial damage in donor hearts from cold ischemia and restored clock gene period 2 (Per2, with a role in mitochondrial metabolic regulation); 3) warm ischemia resulted in abnormal mitochondrial structure in mouse and human DCD hearts, with decreased Per2, and 4) Per2 knockdown worsened mitochondrial injury and abolished MSC CM-mediated mitochondrial preservation in myocytes during stress. Collectively, we hypothesize that post-ischemic administration of MSC secretions using the EVHP ameliorates warm ischemia-induced functional deterioration of DCD hearts via Per2-elicited mitochondrial improvement. We expect that a novel approach using the engineered EVs to deliver Per2 will promote mitochondrial recovery and myocardial resuscitation in DCD hearts. We propose two aims: 1. test the hypothesis that ex vivo application of MSC secretions using the EVHP ameliorates warm ischemia-induced myocardial damage via mitochondrial preservation in DCD hearts; and 2. determine the role of Per2 in improving mitochondrial performance in DCD hearts and demonstrate beneficial effects of Per2-loaded MSC-EVs on resuscitation of DCD hearts. The translational potential of MSC-derived therapy and the engineered EVs will also be assessed in human-like porcine DCD hearts. The results from this study can provide foundation for potential clinical trials in that MSC secretions can be utilized to improve DCD heart recovery and help us gain mechanistic insights on therapeutic targets to limit warm ischemic injury in DCD hearts for transplantation.