Evaluation of Hypothermic Oxygenated Perfusion Ex-Vivo Heart Perfusion to Expand the Donor Pool and Improve Transplant Outcomes

心脏移植是选定的严重心力衰竭患者的最佳治疗选择。由于捐献心脏的数量有限，英国每年接受这种治疗的患者不到200人，但我们知道大约有2000名年龄在65岁以下的患者死于心力衰竭。另一方面，许多由脑死亡捐赠者(DBD)善意捐赠的心脏没有被移植，因为担心它们在体外储存后可能会有多好的效果，以及移植手术的困难。来自年长捐赠者和心肌增厚的心脏不会被使用，因为它们在储存过程中变质太多。传统的将心脏储存在人体外的方法--冰盒--会使心脏失去氧气。当受体体内的心脏血流恢复时，突然向能量和营养耗尽的心脏供应氧气会造成损伤，称为缺血再灌注(IR)损伤。这会显著降低心脏的功能，是移植后最常见的死亡原因，所以我们只选择最好的心脏，并允许它们在冰盒中保存最多4小时。非心脏跳动捐赠，或循环死亡后捐赠(DCD)，这是英国引领世界的一个领域，有可能使心脏移植数量增加30%。然而，由于这些DCD心脏在从捐赠者体内移除后不久就必须补充氧气，它们依赖于一台机器在动脉周围泵血来储存和运输。唯一可用的机器将供者心脏保持在温暖的温度(34摄氏度)下跳动状态。然而，它的成本，每次使用32K GB，太昂贵了，无法广泛采用。低温氧合灌流(HOP)是一种在低温(8摄氏度)下用氧气泵入血液以保存体外心脏的新方法。我们认为它比冰盒更好，因为里面的供者心脏在储存过程中获得了营养和氧气。在实验室里，这给出了很好的结果，但还没有在人类心脏上得到证实，特别是对于一些我们目前拒绝使用的心脏。我们想要证明对心肌细胞的损伤更少，这会导致心脏跳动更强劲。我们还想表明，存储时间可以延长到12小时。我们计划保存10个拒绝临床移植但捐赠用于研究的DBD和10个DCD人心脏，使用HOP保存4-12小时；另一组10个DBD心脏使用冰盒4小时。在这段时间的储存后，他们将被放入检测电路，并提供基于血液的营养丰富的溶液，这种溶液模拟移植到接受者体内，但在实验室里，再持续4个小时。我们将采集循环中的心脏肌肉和溶液的样本，并记录心脏收缩的强度。首先，我们想测试不能用于临床移植的DBD和DCD心脏在HOP保存长达12小时后是否具有良好的功能。其次，将对样本进行实验，以比较有多少心肌细胞死亡或受损，以及这是否与心脏收缩的强度有关。此外，我们将寻找能够方便、快速地测量并反映供者心脏质量的标记物。在临床心脏移植过程中也将采集类似的样本。我们将测试我们发现的标志物是否也能预测患者移植后的心功能。随着对HOP如何保护心脏质量有了更好的了解，我们希望使用这种方法来增加移植心脏的数量，延长保存期，并改善心脏移植的结果。总体而言，我们希望研究这种新的心脏保存方法是否会使更多等待名单上的患者受益于心脏移植。

Heart transplantation is the best treatment option for selected patients with severe heart failure. As the number of donor hearts is limited, every year, fewer than 200 patients in the UK receive this treatment, but we know approximately 2000 patients younger than 65 years die of heart failure. On the other hand, many hearts kindly donated by the brain death donors (DBD) are not being transplanted due to the concerns about how well they may work following storage outside the body and the difficult transplant operation. Hearts from older donors and those with thickened heart muscles are not used because they deteriorate too much during storage. The traditional method to store heart outside human body, an ice box, deprives heart of oxygen. When blood flow to the heart is resumed in a recipient's body, the sudden supply of oxygen to the energy- and nutrient-depleted heart causes damage, called ischaemia reperfusion (IR) injury. This markedly reduces the function of the heart and is the commonest cause of death after transplant, so we only select the best hearts and allow them to be stored in the ice box for a maximum of 4 hours. Donation from non-heart beating, or donation after circulatory death (DCD), a field in which the UK leads the world, has the potential to increase number of heart transplants by 30%. However, as these DCD hearts have to be supplied with oxygen soon after being removed from donor bodies, they rely on a machine pumping blood around the arteries for storage and transportation. The only available machine maintains donor hearts in beating state at a warm temperature (34 degree Celsius). However, its cost, £32k per usage, is too expensive for it to be widely adopted. A new method Hypothermic Oxygenated Perfusion (HOP), which pumps blood with oxygen at low temperature (8 degree Celsius) to store heart outside human body has been developed. We believe it is better than the ice box, because donor hearts inside it receive nutrient and oxygen during storage. In the laboratory this gives good results, but has yet to be proven for the human heart, and particularly for some of the hearts we currently turn down for use. We want to show that there is less damage to the heart muscle cells, and this results in a stronger beating heart. We also want to show that the storage time can be extended for up to 12 hours. We plan to store 10 DBD and 10 DCD human hearts, that are declined for clinical transplantation but donated for research, using HOP for 4-12 hours; and another group of 10 DBD hearts using the ice box for 4 hours. After this period of storage, they will be put onto a testing circuit and provided with blood-based nutrient-rich solution, which mimics the transplant into a recipient, but in the laboratory, for another 4 hours. We will take samples of the heart muscles and solution in the circuit, and record the strength of the heart contractions. First, we would like to test whether the DBD and DCD hearts, that are not accepted for clinical transplant, have good function after being stored by HOP for up to 12 hours. Second, experiments on the samples will be performed to compare how many heart muscles cells are dead or damaged and whether this correlates with the strength of the heart contractions. In addition, we will look for markers which can be easily and quickly measured and reflect the donor heart quality. Similar samples will be taken during clinical heart transplantation. We will test whether the markers that we found also predict heart function after transplantation in patients. With a better understanding of how HOP works to protect heart quality, we hope to use this method to increase the number of hearts being transplanted, lengthen the storage period, and improve the heart transplant outcomes. Overall, we would like to study whether this new heart storage method will make more patients on the waiting list benefit from heart transplantation.