Role of the thymic epithelium on the outcome of allogeneic transplantation

描述（由申请人提供）：同种异体造血干细胞移植（HSCT）的成功结果取决于供体来源的T细胞对宿主免疫系统的完全重建。虽然完整的胸腺对T细胞重建至关重要，但胸腺依赖性T细胞库的恢复可能受到胸腺上皮变化的限制，这些变化是由化疗/放疗方案或移植物抗宿主病（GVHD）引起的移植介导的毒性引起的。本研究的目的是研究体内给予上皮细胞营养因子是否对同种异体骨髓移植（alloc - bmt）后的T细胞再生和GVHD的预防有有益的影响。我们将在这些实验中使用的营养因子包括角化细胞生长因子（KGF）和NF受体激活因子？B配体（RANKL）与缺乏信号蛋白Sin表达的转基因动物模型相结合。KGF是一种有效的上皮细胞有丝分裂原，在临床前小鼠模型中已被证明可以扩大胸腺皮质和髓质上皮，增加胸腺增生，并阻止GVHD的发展。另一方面，RANKL对于胸腺髓质上皮细胞（mTECs）亚群的发育和分化很重要，这些细胞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在胸腺上皮中表达，并且Sin缺乏抑制KGF-和rankl诱导的胸腺上皮细胞的扩增。在本提案中，我们将验证以下假设：KGF和rankl介导的胸腺上皮扩张导致allo-BMT后更好的T细胞重建和对GVHD的保护。Sin缺乏抑制KGF/RANKL信号传导，并在移植后改善这些因素的有益作用。为了验证这一假设，我们将：1)使用在Sin缺失背景下的alloo - bmt小鼠模型来检查kgf介导的a) T细胞库再生是否需要Sin；b)重建T细胞介导的免疫反应和c)对GVHD的保护。2)研究RANKL是否也能保护机体免受同种异体bmt相关的毒性，它是否独立于KGF或与KGF联合作用，以及RANKL在同种异体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调控KGF/RANKL介导的胸腺上皮细胞扩增的分子机制。我们预计这些实验将为在正常或移植条件下胸腺上皮如何调节胸腺生成提供新的见解，可能确定RANKL和Sin作为同种异体骨髓移植后胸腺上皮介导的T细胞重构的调节因子，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.