Role of the thymic epithelium on the outcome of allogeneic transplantation

描述（由申请人提供）：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。虽然完整的胸腺对于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细胞变化的限制，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。本提案的目的是检查是否通过在体内施用上皮细胞营养因子来促进胸腺上皮，对异基因骨髓移植（allo-BMT）后T细胞再生和预防GVHD发挥有益作用。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NF？B配体（RANKL）与信号蛋白Sin表达缺陷的遗传修饰的动物模型的组合。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显示其扩张皮质和髓质胸腺上皮，增加胸腺生成，并防止GVHD的发展。另一方面，RANKL对胸腺髓质上皮细胞（mTEC）亚群的发育和分化非常重要，该亚群通过消除自身反应性T细胞克隆参与抑制自身免疫。我们最近发现Sin在胸腺上皮中表达，Sin缺乏抑制KGF和RANKL诱导的胸腺上皮细胞扩增。在本提案中，我们将检验以下假设：KGF和RANKL介导的胸腺上皮细胞扩增导致更好的T细胞重建和allo-BMT后的GVHD保护。Sin缺乏抑制KGF/RANKL信号传导并改善移植后这些因子的有益作用。为了检验这一假设，我们将：1）使用Sin缺陷背景下的allo-BMT小鼠模型来检查Sin是否是KGF介导的a）T细胞库再生; B）T细胞介导的免疫应答的重建和c）免于GVHD的保护所必需的。2)检查RANKL给药是否也可以防止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)使用Sin缺陷小鼠鉴定KGF和RANKL的胸腺上皮细胞靶点，并阐明Sin调节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，可能将RANKL和Sin确定为allo-BMT后胸腺上皮介导的T细胞重建的调节因子，并可能导致确定新的策略/靶点，以更好地管理HSCT的结局。 公共卫生相关性：在本申请中，使用基因修饰的小鼠模型，我们将检查通过在体内施用上皮细胞营养因子来加强胸腺上皮是否对T细胞重建和异基因骨髓移植后移植物抗宿主病的预防发挥有益作用。我们预计，这里提出的实验将提供洞察胸腺上皮细胞调节T细胞重建的机制，在正常或移植条件下，并可能确定新的治疗策略或目标，以更好地管理与临床移植和移植物抗宿主病相关的并发症。

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. PUBLIC HEALTH RELEVANCE: In this application, using a genetically modified mouse model, we will examine whether boosting the thymic epithelium by in vivo administration of epithelial-cell-trophic-factors, exerts beneficial effects on T cell reconstitution and prevention of graft-versus-host disease following allogeneic bone marrow transplantation. We anticipate that the experiments proposed here will provide insight into the mechanisms through which the thymic epithelium regulates T cell reconstitution under normal or transplantation conditions, and may identify novel therapeutic strategies or targets to better manage complications associated with clinical transplantation and graft-versus-host disease.