Whole heart suspended animation: leveraging the zebrafish to solve the organ shortage

目前，美国有超过12.3万名等待器官移植的患者，这个数字远远超过 现有器官的供应，而且这一数字每年持续增长约5%。在加拿大，每十分钟 有人被添加到等待名单中，每天有大约22人在等待移植时死亡。一个主要原因是 我们目前器官保存和处理做法的局限性，这严重限制了保存 持续时间长，不允许移植受轻微损伤的器官。该项目旨在制定一项协议 将心脏储存数周以实现全球器官匹配并克服缺血耐受性的限制 以增加捐赠者的心脏储备。 我建议解决目前心脏移植障碍的策略，包括体外保存和 边缘器官的恢复，应该从大自然中寻找灵感。更具体地说，能够降级为 “暂停生命”状态，其特征是生命进程减慢和压力耐受性提高； 信守诺言。我将系统地利用两种暂停动画的方法：1)耐冻，2) 高温冬眠。利用大自然中耐寒的林蛙的灵感，我试图开发出一种 用于全心保存的协议，将在存在的情况下实现较高的零下保存温度 细胞外的冰，以及几周到几个月的保存期。此外，我将确定哪些药理药物 是否会战略性地降低代谢需求，以匹配氧气/营养的供应，并增加热缺血 从几分钟到几个小时的忍耐力，利用自然界冬眠的灵长类动物的灵感。 为了实现这一目标，我建议引入斑马鱼作为一种新的低温生物学和 器官移植。虽然斑马鱼已经成为研究人类疾病的热门研究动物，但它 从未被用作开发器官处理和保存的创新方法或 了解器官移植的基本生物学。斑马鱼等经典模式生物 提供多种优势，包括强大的遗传/生化工具、易于实时成像、与 高通量研究，而且价格便宜，易于维护。得到了纵向扩展实验和 在包括大鼠在内的哺乳动物模型系统中的验证，本建议将弥补 研究领域。

There are currently over 123,000 patients on the organ transplant waiting list in the US, a number that far exceeds the supply of available organs, and that continues to grow ~5% each year. In Canada, every ten minutes someone is added to the waitlist and ~22 people die each day while waiting for a transplant. A major reason is the limitations of our current organ preservation and handling practices, which severely restricts preservation duration and disallows the transplantation of marginally injured organs. This project aims to develop a protocol to bank hearts for several weeks to enable global organ matching and overcome limitations of ischemia tolerance to increase the donor pool of hearts. I propose that strategies to solve current barriers in heart transplantation, including ex vivo preservation and recovery of marginal organs, should look to nature for inspiration. More specifically, the ability to descend into a state of “suspended animation”, characterized by the slowing of life processes and improved stress tolerance, holds promise. I will systematically leverage two methods of suspended animation; 1) freeze-tolerance, and 2) high-temperature hibernation. Using inspiration from freeze-tolerant wood frogs in nature, I seek to develop a protocol for whole heart preservation which will achieve high subzero storage temperatures in the presence of extracellular ice, and storage durations of weeks to months. Further, I will identify pharmacological agents which will strategically lower metabolic demands to match oxygen/nutrient availability, and increase warm ischemia tolerance from minutes to hours, using inspiration from hibernating primates in nature. To accomplish this goal, I propose to introduce the zebrafish as a novel model system for cryobiology and organ transplantation. While zebrafish has become a favored research animal for studying human disease, it has never been used as a tool to develop innovative approaches for organ handling and preservation or to understand the underlying biology of organ transplantation. Classical model organisms such as the zebrafish offer many advantages including robust genetic/biochemical tools, ease of real-time imaging, compatibility with high-throughput studies, and are cheap and easy to maintain. Complimented by scale-up experiments and validation in mammalian model systems, including rats, the present proposal will mend a critical gap in the research field.