Genetically-engineered pig orthotopic (life-supporting) heart transplantation (OHTx) in baboons: establishing consistent graft survival and overcoming rapid post-Tx organ growth

基因工程猪器官移植的免疫学和组织化学研究 功能研究 项目3：基因工程猪原位（生命支持）心脏移植（Tx）， 狒狒：建立一致的异种移植物存活率并克服快速的Tx后器官生长（PI： Muhammad Mohiuddin）。 总结/摘要 异种移植领域在过去几年中取得了重大进展。然而，成功 在非人灵长类动物中进行维持生命的（原位）猪心脏移植（OHTx）目前受到两个限制 主要问题-（i）由于不太清楚的非免疫学原因（称为“免疫性”）导致的直接移植失败， 手术性心脏异种移植物功能障碍“或”PCXD“），和（ii）在Tx后的最初几年中心脏快速生长 几个月，可能导致心脏压迫和功能障碍。我们建议调查并解决 这两个问题。 (i)我们假设PCXD与线粒体功能受损有关， OHTx期间心肌保护不足和Tx后三碘甲状腺原氨酸（T3）水平低。我们将使用 一种新的保存系统（“Steen”系统），并在Tx后立即将其与T3治疗联合收割机相结合 期我们对线粒体功能的详细研究将有助于阐明PCXD的相关机制。我们 已经对Steen系统进行了初步测试，结果令人鼓舞，并已证实 T3水平在狒狒中猪OHTx后的前几周内保持明显低于正常水平。 (ii)我们假设，猪异种心脏移植物的过度生长将通过Tx 生长激素受体基因被敲除的猪的心脏。8个基因的猪 已经进行了一些操作（所有这些操作都旨在保护心脏免受灵长类动物免疫反应的影响）- 这是以前任何小组都没有得到的-将成为我们所有实验的基础，但是，此外， 生长激素受体将通过第九次基因操作被删除。 如果这两个问题能够得到解决，先天免疫反应的控制（通过基因操作 在器官源猪中）和适应性免疫应答（通过基于共刺激阻断的 免疫抑制方案）将允许对 在6个月的随访期内，猪心脏在支持狒狒循环方面的血流动力学功能 个月我们预计，这些研究的结果将使我们能够考虑启动一项临床研究， 异种心脏移植试验

GENETICALLY-ENGINEERED PIG ORGAN TRANSPLANTATION IN BABOONS: IMMUNOLOGICAL AND FUNCTIONAL STUDIES PROJECT 3: Genetically-engineered pig orthotopic (life-supporting) heart transplantation (Tx) in baboons: establishing consistent xenograft survival and overcoming rapid post-Tx organ growth (PI: Muhammad Mohiuddin). SUMMARY/ABSTRACT The field of xenotransplantation has made significant progress in the last few years. However, successful life-supporting (orthotopic) pig heart transplantation (OHTx) in nonhuman primates is currently limited by two major problems – (i) immediate graft failure from a poorly-understood, non-immunologic cause (known as `peri- operative cardiac xenograft dysfunction' or `PCXD'), and (ii) rapid growth of the heart in the first few post-Tx months, potentially resulting in cardiac compression and dysfunction. We propose investigating and resolving these two problems. (i) We hypothesize that PCXD is associated with impaired mitochondrial function that results from inadequate myocardial preservation during OHTx and low post-Tx triiodothyronine (T3) levels. We shall use a novel system of preservation (the `Steen' system) and combine this with T3 therapy in the immediate post-Tx period. Our detailed studies on mitochondrial function will throw light on the mechanisms involved in PCXD. We have already carried out preliminary testing of the Steen system, with encouraging results, and have confirmed that T3 levels remain grossly subnormal during the first few weeks after pig OHTx in baboons. (ii) We hypothesize that excessive growth of the pig cardiac xenograft will be prevented by the Tx of hearts from pigs in which the gene for growth hormone receptors has been knocked out. Pigs in which 8 genetic manipulations have been carried out (all aimed at protecting the heart from the primate immune response) – which have not been available to any group previously - will form the basis of all our experiments but, in addition, growth hormone receptors will be deleted by a ninth genetic manipulation. If these two problems can be resolved, control of the innate immune response (by the genetic manipulations in the organ-source pig) and of the adaptive immune response (by a costimulation blockade-based immunosuppressive regimen introduced by us with proven success) will allow a comprehensive investigation of the hemodynamic function of the pig heart in supporting the baboon's circulation over a follow-up period of 6 months. We anticipate that the results of these studies will enable consideration to be given to initiating a clinical trial of cardiac xenotransplantation.