CRISPR-Modified Cardiac Xenograft Transplantation

摘要：CRISPR修饰的心脏异种移植 在过去的三年里，异种心脏移植取得了两项重大突破。一是 以前难以克服的延迟性异种移植排斥反应（DXR）的障碍已经在猪到狒狒中被克服， 心脏异种模型。在这个模型中，DXR主要表现为接受者的消耗性凝血病（CC 以及移植物中的血栓性微血管病（TM）。在狒狒的异位模型中， “Mohiuddin/NIH”组使用基因修饰的GTKO.hCPRP.hTBM心脏和治疗方案 包括“诱导”T和B耗竭，MMF和类固醇-所有临床使用的药物-与实验 针对CD 40的单克隆抗体。DXR的预防时间与CD 40治疗的时间一样长。 在一种情况下，异种移植物的存活期延长到两年以上。 第二个主要进展来自慕尼黑小组，他们报告了原位移植的持续存活率。 使用我们的免疫调节方案超过180天的猪心脏异种移植受体， GTKO、hCPRP、hTBM心脏。实现原位异种心脏移植物的持续存活， 通过初始异种移植物功能障碍（IXD）来预防，这是一种难以通过多种方法协同努力的现象。 经验丰富的临床移植团队重要的是，慕尼黑研究小组发现， 这是必要的和足够的，以持续预防IXD。发现缺血最小化足以 克服IXD障碍是一个“突破性”的进步，即使是通过 局部缺血最小化还没有被很好地理解。 在这个项目中，我们假设IXD损伤GTKO、hCPRP、hTBM心脏的机制可能是 通过在Pig 2.0的一个或多个版本中表达的额外的异种聚焦遗传修饰来解决， 由我们在eGenesis的合作者使用创新的CRISPR驱动的基因编辑工具创建。小猪2.0 旨在通过12种异种- 有针对性的基因改造这个项目利用了几个定义良好的 Pig 2.0，我们在多种体外、离体和体内心脏异种模型方面的丰富经验，以及一个强大的 确定Pig 2.0是否可防止心脏IXD（伴或不伴缺血）的机制试验能力 最小化（目标1）。具体来说，我们将使用这些独特的资源来了解a）Pig 2.0的版本是否 含有凝血级联调节基因盒的受保护的受试者免于IXD; B）是否缺血 最小化对于预防易感猪2.0心脏中的IXD是必要的和/或足够的;以及c）定义 狒狒中猪2.0心脏的临床可接受的免疫抑制方案始终安全， 有效（目标2）。该项目的结果将产生可能催化其他细胞和器官进展的见解 异种移植，并告知临床心脏异种移植试验设计。

SUMMARY ABSTRACT: CRISPR-Modified Cardiac Xenograft Transplantation The past three years have witnessed two major breakthroughs in heart xenotransplantation. First, the previously intractable barrier of delayed xenograft rejection (DXR) has been overcome in the pig-to-baboon heart xeno model. In this model, DXR is manifest primarily as consumptive coagulopathy (CC) in the recipient and thrombotic microangiopathy (TM) in the graft. Working in the heterotopic model in baboons, our `Mohiuddin/NIH' group used genetically modified GTKO.hCPRP.hTBM hearts and a treatment regimen including “induction” T and B depletion, MMF, and steroids – all clinically used drugs – with an experimental monoclonal antibody directed against CD40. DXR was prevented for as long as CD40 treatment was continued, and in one instance xenograft survival was extended beyond two years. The second major advance came from the Munich group, who reported consistent survival of orthotopic pig heart xenograft recipients beyond 180 days using our immunomodulatory regimen and GTKO.hCPRP.hTBM hearts. Accomplishing consistent survival of orthotopic heart xenografts had previously been prevented by initial xenograft dysfunction (IXD), a phenomenon refractory to concerted efforts by multiple experienced clinical transplant teams. Importantly, the Munich group found that minimizing graft ischemia was necessary and sufficient to consistently prevent IXD. Discovering that ischemia minimization was sufficient to overcome the IXD barrier is a `breakthrough' advance, even as the mechanism of improved graft protection by ischemia minimization is not yet well understood. In this Project, we hypothesize that IXD mechanisms that injure GTKO.hCPRP.hTBM hearts may be addressed by the additional xeno-focused genetic modifications expressed in one or more versions of Pig 2.0, created by our collaborators at eGenesis using innovative CRISPR-driven gene editing tools. Pig 2.0 is designed to address multiple known xeno-specific injury mechanisms through a combination of 12 xeno- targeted genetic modifications. This Project takes advantage of availability of several well-defined versions of Pig 2.0, our deep experience with multiple in vitro, ex vivo, and in vivo heart xeno models, and a robust mechanistic assay capability to determine whether Pig 2.0 is protected from heart IXD, with or without ischemia minimization (Aim 1). Specifically, we will use these unique resources to learn a) whether versions of Pig 2.0 containing a coagulation cascade regulatory gene cassette are protected from IXD; b) whether ischemia minimization is necessary and/or sufficient to prevent IXD in susceptible Pig 2.0 hearts; and c) to define a clinically acceptable immunosuppression regimen for Pig 2.0 hearts in baboons that is consistently safe and effective (Aim 2). Results from this Project will yield insights likely to catalyze progress for other cell and organ xenografts, and inform clinical heart xenotransplantation trial design.