肝移植后Th17-Treg转分化促进肝癌复发转移的机制研究

The recurrence and metastasis of hepatocellular carcinoma after liver transplant are closely associated with post-transplant immune status. We found that Th17 cells were activated during graft rejection. Recent studies showed that Th17 cells could transdifferentiate to other T cell subtypes, which lead to the changes of their functions. Our previous studies showed that murine liver transplantation enhanced Th17-Treg conversion and the pro-tumor functions of Tregs transdifferentiated from Th17 are stronger than normal Tregs. We also observed that murine IL-33 level was increased after liver transplantation, which have been showed to promote Treg differentiation. Thus, we hypothesized that liver transplantation promotes Th17-Treg transdifferentiation via IL-33，which induces hepatocellular carcinoma recurrence and metastasis. And IL-33 could be the therapeutic target. It remains elusive that whether this conversion impact the recurrence and metastasis of hepatocellular carcinoma after liver transplant. This project would use animal models and clinical samples to investigate the mechanisms of Th17-Treg transdifferentiation and its impacts on immune responses and the recurrence and metastasis of hepatocellular carcinoma. Moreover, we will analyze the key cytokines，signaling pathways，and therapeutic targets of this process. Finally, we will clarify its clinical significance. Our aim is to clarify the mechanisms of Th17-Treg transdifferentiation in promoting hepatocellular carcinoma after liver transplantation, which could provide new therapeutic targets for the treatments.

肝移植术后肝癌复发转移与移植后机体免疫状态密切相关。本课题组前期研究发现Th17参与肝移植排斥反应。Th17近年来被发现可以转分化为其他T细胞亚群，导致功能转变。我们的前期研究发现小鼠肝移植后Th17-Treg转分化增强，且从Th17转化来的Treg较常规Treg具有更强的促癌作用。我们还发现小鼠肝移植后IL-33表达升高。研究表明IL-33具有促进Treg分化的作用。因此，我们推测肝移植后IL-33水平升高促进了Th17-Treg转分化，继而促进肝移植后肝癌复发转移，基于IL-33在这一过程中的关键作用，其可作为潜在的干预靶点。目前Th17-Treg转分化在肝移植术后肝癌复发转移中的作用尚不清楚。本项目拟明确肝移植后Th17-Treg转分化的机制及其对肝癌复发转移的影响作用，分析促进Th17-Treg转分化的关键细胞因子和信号通路，为探寻移植术后肝癌复发转移的干预靶点奠定基础。

本项目以肝移植中Th17/Treg平衡及其关键调控因子IL-33的免疫学变化和作用机制为重点研究方向。课题组首先验证了肝移植中Th17-Treg转分化和IL-33变化的现象，但发现转分化细胞在整体Th17和Treg中比例较低，同时由于严重的缺血再灌注损伤（IRI），动物模型的生存期难以满足肝癌复发的研究要求。因此，课题组一方面选择生存率更高的大鼠模型开展后续研究，另一方面深入探讨IL-33和Th17/Treg平衡在IRI中的作用机制。通过系列动物实验和临床标本检测，结合转录组测序和单细胞测序的多组学检测技术，我们取得了以下主要发现：肝移植可显著上调IL-33水平，IL-33可促进Th17/Treg平衡向Th17方向偏移，加重肝移植IRI。而在IRI更加严重的脂肪变性供肝肝移植中，IL-33和Th17的表达上调更加显著。并且，IL-33还可通过激活中性粒细胞，促进中性粒细胞胞外诱捕网（NETs）形成，进一步加重肝移植IRI。最后，结果显示靶向阻断IL-33可有效减轻肝移植IRI，延长大鼠肝移植术后生存期。因此，本项目表明IL-33对Th17/Treg平衡和中性粒细胞/NETs的调控是肝移植IRI的重要机制，IL-33将成为减轻肝移植IRI，改善肝移植患者预后的重要治疗靶点。