Role of the thymic epithelium on the outcome of allogeneic transplantation

描述(申请人提供)：异基因造血干细胞移植(HSCT)的成功结果取决于供者来源的T细胞对宿主免疫系统的完全重建。虽然完整的胸腺对于T细胞重建至关重要，但胸腺依赖T细胞的恢复可能会受到胸腺上皮细胞变化的限制，这些变化是由移植引起的化疗/放疗方案或移植物抗宿主病(GVHD)引起的。本研究的目的是探讨体内应用上皮细胞营养因子促进胸腺上皮细胞生长是否对T细胞再生和预防异基因骨髓移植后移植物抗宿主病(GVHD)有积极作用。我们将在这些实验中使用的营养因子包括角质形成细胞生长因子(KGF)和核因子B受体激活剂(RANKL)，以及信号蛋白Sin表达缺陷的转基因动物模型。KGF是一种强有力的上皮细胞有丝分裂原，已被证明在临床前小鼠模型中可以扩张皮质和髓质胸腺上皮，增加胸腺生成，防止GVHD的发展。另一方面，RANKL对于髓质胸腺上皮细胞亚群(MTECs)的发育和分化非常重要，mTECs参与通过消除自身反应性T细胞克隆来抑制自身免疫。我们最近发现Sin在胸腺上皮细胞中表达，Sin缺乏抑制KGF和RANKL诱导的胸腺上皮细胞的扩张。在这个方案中，我们将检验以下假设：KGF和RANKL介导的胸腺上皮扩张导致更好的T细胞重建和对异基因骨髓移植后GVHD的保护。SIN缺乏抑制了KGF/RANKL信号转导，改善了这些因子在移植后的有利作用。为了验证这一假设，我们将：1)使用Sin缺乏背景下的allo-BMT小鼠模型来检查Sin是否对于KGF介导的a)T细胞再生；b)T细胞介导的免疫反应的重建和c)对移植物抗宿主病的保护是必需的。2)研究RANKL给药是否也可以预防allo-BMT相关毒性，它是否独立于KGF或与KGF联合作用，以及RANKL在allo-BMT中的作用是否需要Sin。3)利用Sin缺陷小鼠鉴定KGF和RANKL的胸腺上皮细胞靶点，阐明Sin调节KGF/RANKL介导的胸腺上皮细胞增殖的分子机制。我们预计，这些实验将为胸腺上皮如何在正常或移植条件下调节胸腺生成提供新的见解，可能确定RANKL和Sin是异基因骨髓移植后胸腺上皮介导的T细胞重建的调节因子，并可能导致识别新的策略/靶点，以更好地管理HSCT的结果。

DESCRIPTION (provided by applicant): The successful outcome of allogeneic hematopoietic stem-cell transplantation (HSCT) depends on the complete reconstitution of the host's immune system by donor-derived T cells. While an intact thymus is critically important for T cell reconstitution, thymus-dependent T cell repertoire restoration may be limited by changes in the thymic epithelium, brought about by transplant-mediated toxicities from chemotherapy/radiation regimens or graft vs. host disease (GVHD). The aim of this proposal is to examine whether boosting the thymic epithelium by in vivo administration of epithelial-cell-trophic-factors, exerts beneficial effects on T cell regeneration and prevention of GVHD following allogeneic bone marrow transplantation (allo-BMT). The trophic factors we will use in these experiments include keratinocyte growth factor (KGF) and receptor activator of NF?B ligand (RANKL) in conjunction to a genetically modified animal model deficient in expression of the signaling protein Sin. KGF is a potent epithelial cell mitogen which has been shown to expand the cortical and medullary thymic epithelium, increase thymopoiesis, and prevent the development of GVHD in preclinical mouse models. RANKL on the other hand, is important for development and differentiation of a subpopulation of medullary thymic epithelial cells (mTECs) involved in suppressing autoimmunity through elimination of autoreactive T cell clones. We recently found that Sin is expressed in the thymic epithelium and Sin deficiency inhibits KGF- and RANKL-induced expansion of thymic epithelial cells. In this proposal we will test the following hypothesis: KGF- and RANKL-mediated expansion of the thymic epithelium leads to better T cell reconstitution and protection from GVHD following allo-BMT. Sin deficiency inhibits KGF/RANKL signaling and ameliorates the beneficial effects of these factors after transplantation. To test this hypothesis we will: 1) Use allo-BMT mouse models in the Sin-deficient background to examine whether Sin is required for KGF-mediated a) T cell repertoire regeneration; b) reconstitution of T cell-mediated immune responses and c) protection from GVHD. 2) Examine whether RANKL administration can also protect from allo-BMT-related toxicity, whether it acts independently of or in conjunction with KGF and if Sin is required for the effects of RANKL in allo-BMT. 3) Use Sin deficient mice to identify the thymic epithelial cell targets of KGF and RANKL as well as elucidate the molecular mechanisms through which Sin regulates KGF/RANKL-mediated thymic epithelial cell expansion. We anticipate that these experiments will provide novel insight into how the thymic epithelium regulates thymopoiesis under normal or transplantation conditions, may identify RANKL and Sin as regulators of thymic epithelia-mediated T cell reconstitution following allo-BMT, and may lead to the identification of novel strategies/targets to better manage the outcome of HSCT.