Metabolic Engineering for Improved Liver Function

描述(申请人提供)：原位肝移植(OLT)是治疗急性和慢性肝功能衰竭的一种非常成功的治疗方法，但供体肝脏的稀缺严重限制了这种治疗。在脑死亡后捐献的肝脏中，术后肝功能衰竭的最常见的单一易感因素是脂肪变性；因此，脂肪肝通常被认为是“不可接受的”或“略可接受的”移植。根据尸检和供体肝活检，肝脏脂肪变性的发生率为10%至25%。显然，挽救因严重脂肪变性而被遗弃的捐赠者的方法可以显著减少患者死亡人数，并有助于缩小肝移植的供需缺口。总体假设是，废弃的供体肝脏，更具体地说是脂肪变性的肝脏(在心脏死亡后的长期供体)，可以在良好控制的条件下，在生理温度下通过人工溶液灌流来挽救，以促进脱脂和细胞修复，结果是能够承受手术，并将术后肝功能障碍的风险降低到与正常肝脏相似的水平。在这里提出的研究中，我们的目标是将这种方法应用于脂肪肝，并最终应用于更复杂的缺血性肝脏病例(即心脏死亡后的供体)。我们的具体目标是：(1)优化常温或亚低温灌流过程中脂肪变性肝脏的代谢；(2)研究热休克和温灌流对脂肪变性肝脏微血管功能和可移植性的联合影响；(3)建立恢复热缺血肝脏线粒体功能和ATP储存的常温灌流方案。在短期内，拟议的研究可以(A)为扩大供体池规模提供理论基础；(B)改善接受边缘供体肝脏的患者的预后；(C)延长脂肪变性、脱脂和热缺血肝脏的有效保存时间。从长远来看，这些研究将导致(A)增加捐赠者池的规模和(B)增加器官储存时间，超过目前冷藏技术的限制。这些结果将显著缓解供体短缺，并引领供体银行的道路，有可能彻底改变供体肝脏的分配。与公共卫生的相关性：拟议的研究将提供基本的科学信息和新技术，使原本被捐赠者池拒绝的捐赠者肝脏得以恢复。从长远来看，这些研究将导致(A)增加捐赠者池的规模和(B)增加器官储存时间，超过目前冷藏技术的限制。这些结果将显著缓解供体短缺，并引领供体银行的道路，有可能彻底改变供体肝脏的分配。

DESCRIPTION (provided by applicant): Orthotopic liver transplantation (OLT) is a highly successful therapeutic modality for the treatment of both acute and chronic liver failure which is severely limited by the scarcity of donor livers. Among the livers donated after brain death, the most common single predisposing risk factor for postoperative liver failure is steatosis; thus, fatty livers are often considered to be "unacceptable" or "marginally acceptable" for transplantation. The incidence of hepatic steatosis is 10 to 25% based on autopsy studies and donor liver biopsies. It is clear that methods that would salvage discarded donors because of severe steatosis could significantly reduce the number of patient deaths, and help close the gap between supply and demand in liver transplantation. The overall hypothesis is that discarded donor livers, and more specifically steatotic livers (and in the long run donors after cardiac death), can be salvaged by perfusion with artificial solutions under well-controlled conditions and at physiological temperatures in order to promote defatting and cellular repair, and as a result made capable to withstand surgical procedures and reduce the risk of postoperative liver dysfunction to a level similar to that observed in normal livers. In the studies proposed herein, our objective is to apply this approach to fatty livers, and eventually to the more complex case of ischemic livers (i.e. from donors after cardiac death). Our specific aims are: (1) To optimize metabolism for defatting steatotic livers during normothermic or mild hypothermic perfusion; (2) To investigate the combined effects of heat shock and warm perfusion on microvascular function and transplantability in steatotic livers; (3) To develop a normothermic perfusion protocol that restores mitochondrial function and ATP stores in warm ischemic livers. In the short-term, the proposed studies could (a) provide the rationale basis for increasing the donor pool size; (b) improve the outcome of patients which receive marginal donor livers; (c) prolong the useful preservation time of steatotic, defatted, as well as warm ischemic livers. In the long-term, these studies will lead to (a) increased donor pool size and (b) increased organ storage time beyond the limits of current cold storage techniques. These outcomes will significantly alleviate donor shortage and lead the way to donor banking, with the potential to revolutionize donor liver allocation. PUBLIC HEALTH RELEVANCE: The proposed studies will provide basic scientific information and new technologies that will enable the recovery of donor livers that are otherwise rejected from the donor pool. In the long-term, these studies will lead to (a) increased donor pool size and (b) increased organ storage time beyond the limits of current cold storage techniques. These outcomes will significantly alleviate donor shortage and lead the way to donor banking, with the potential to revolutionize donor liver allocation.