Cell Death Pathways and Heart Transplant Rejection

同种异体器官移植和接受已故捐献器官的患者的长期存活率仍然很低。那里 有证据表明，移植过程中的冷缺血(CI)和随后的再灌注会导致 细胞损伤，导致诱导T细胞对供体组织和最终移植物的同种免疫 拒绝。缺血再灌注(IR)引起细胞损伤的机制，损伤的方式， 这种损伤是如何影响同种异体反应的，目前还知之甚少。为了更好地模仿已故的人类捐赠者 移植，仙童实验室开发了一种同种异体心脏移植模型，通过这种模型，捐赠者的器官是 移植前接受延长的CI，然后注射CTLA4Ig共刺激分子 封锁。接受CI的同种异体心脏被排斥，而未接受CI的同种异体心脏存活。 使用该模型的初步研究表明，受者的补体缺乏延长了 脑梗塞治疗的同种异体移植物存活与循环肿瘤坏死因子α减少相关。因为肿瘤坏死因子α是一种已知的诱导剂 坏死性下垂是一种炎性细胞死亡，其他研究表明，来自CyLD缺陷捐赠者的器官， (在坏死性下垂方面有缺陷的)比野生型器官存活的时间更长，而夏平的器官- 不足的捐赠者(加速了坏死性下垂)很快就被拒绝了。基于这些研究，我们有 提出并将检验统一的假设，即在移植过程中CI/IR后补体激活 导致肿瘤坏死因子α的诱导，继而诱导供体组织细胞的坏死性下垂。反过来，这又会导致 炎性细胞损伤激活T细胞同种免疫，导致排斥反应。这项合作研究带来了 三个实验室以高度协同的方式共同解决上述问题的独特优势 假设。(1)在目标1中，我们将研究甘露糖结合凝集素(MBL)启动的补体的作用 在我们的同种异体移植模型中，使用MBL、TNF和 TNFR基因敲除/敲打。(2)在AIM 2中，肿瘤坏死因子细胞死亡通路在CI引发的排斥反应中的作用如下 进一步利用来源于CyLD、RIPK1、RIPK3、 Caspase-8和夏平。(3)坏死性下垂释放损伤相关的分子模式(DAMP)，因此 在目标3中，我们将研究宿主抗原提呈细胞是如何感知潮湿的，以及这是如何导致 诱导T细胞同种异体反应。所有这三个目标都具有非常重要的意义，因为它们将为 在(1)启动、(2)细胞损伤和(3)移植物排斥反应效应阶段的分子可能是靶点 移植中的治疗障碍。这种方法有很强的直接和积极影响的潜力 移植患者的结局。

The long-term survival of allografts and patients receiving deceased donor organs remain poor. There is evidence to suggest that cold ischemia (CI) and the subsequent reperfusion during transplants causes cellular injury, which leads to an induction of T cell alloimmunity against donor tissue and ultimately graft rejection. The mechanism by which ischemia reperfusion (IR) initiates cellular injury, the manner of the injury, and how this injury impacts alloresponse are poorly understood. To better mimic human deceased donor transplants, the Fairchild laboratory developed an allograft heart transplant model whereby the donor organ is subjected to extended CI prior to transplantation followed by administration of an CTLA4Ig costimulatory blockade. Allograft hearts subjected to CI were rejected whereas those not subjected to CI survived. Preliminary studies using this model indicated that complement deficiency in the recipients prolonged the survival of CI-treated allografts, correlating with reduced circulating TNFα. As TNFα is a known inducer of necroptosis, an inflammatory cell death, additional studies showed that organs from CYLD-deficient donors, (which are defective in necroptosis) survived longer than wild type organs whereas organs from SHARPIN- deficient donors (which have accelerated necroptosis) were rapidly rejected. Based on these studies, we have proposed and will test the unifying hypothesis that complement activation following CI/IR during transplants leads to the induction of TNFα, which then induces necroptosis of cells in donor tissues. In turn, this inflammatory cellular injury activates T cell alloimmunity to cause rejection. This collaborative study brings together in a highly synergistic manner the unique strengths of three laboratories to address the above hypothesis. (1) In Aim 1, we will examine the role of mannose-binding lectin (MBL)-initiated complement activation in triggering TNF-dependent necroptosis in our allograft transplant model using MBL, TNF and TNFRs knockouts/knockins. (2) In Aim 2, the role of the TNF cell death pathway in CI-initiated rejection will be further dissected using donor organs derived from various knockouts/knockins of CYLD, RIPK1, RIPK3, Caspase-8 and SHARPIN. (3) Necroptosis releases damage-associated molecular patterns (DAMPs) and thus in Aim 3, we will examine how DAMPs are sensed by host antigen-presenting cells and how this leads to induction of the T cell alloresponse. All three aims are highly significant, as they will provide insights into which molecules during (1) initiation, (2) cellular injury and (3) effector phases of graft rejection may be targeted for therapeutic blockade in transplants. The approach has strong potential to directly and positively impact outcomes of transplant patients.