Crosstalk Control of Thymic Epithelial Development

描述(申请人提供)：胸腺上皮细胞(TECs)负责调节未成熟胸腺细胞发育成具有自我耐受性的成熟T细胞。一种常见的内胚层来源的TEC前体细胞最近被证明可以同时产生皮质和髓质TEC亚群，然而，调控这一过程的信号通路和细胞间相互作用尚不清楚。TEC的发育和组织依赖于胸腺细胞在上皮网络中迁移时从发育中的胸腺细胞接收到的串扰信号。这项研究的目标是确定SP胸腺细胞/TEC相互作用的性质和功能，这些相互作用调节胸腺髓质的发育，胸腺微环境对中枢耐受起关键作用。通过将成熟的T细胞过继转移到T细胞发育受阻的小鼠体内而诱导的骨髓重建将被用来测试特定的T细胞/TEC相互作用的贡献。 我们建议：(1)使用MHC I/MHC II类双KO小鼠来确定胸腺髓质的扩张和分化是否依赖TCR/MHC相互作用，并确定CD4 SP、CDS SP和Tregs在这一过程中的特定贡献；(2)在新开发的Wnt信号报告鼠品系中，使用胎儿胸腺器官培养和骨髓重建实验，以了解Wnt信号在mTEC发育中的贡献，并确定SP胸腺细胞分泌的可溶性Wnt抑制分子是否抑制TEC中规范的Wnt信号通路，从而提供mTEC从前体细胞发育所必需的分子开关。充分了解与TEC发育和组织有关的信号通路和细胞相互作用，对于设计合理的治疗策略以对抗与自身免疫相关的年龄相关胸腺退缩和胸腺结构缺陷至关重要。这些策略还将显著影响骨髓移植治疗癌症的有效性，因为它们可以对抗与包括化疗和放射在内的预备性细胞去除治疗以及移植后移植物抗宿主病相关的严重胸腺过早退化。

DESCRIPTION (provided by applicant): The thymic epithelial cells (TECs) are responsible for regulating the development of immature thymocytes into functional self-tolerant mature T cells. A common endoderm-derived TEC progenitor was recently shown to give rise to both cortical and medullary TEC subsets, however, the signaling pathways and cell-to-cell interactions that regulate this process are poorly defined. TEC development and organization is dependent on crosstalk signals received from developing thymocytes as they migrate through the epithelial network. The goal of this study will be to define both the nature and function of the SP thymocyte/TEC interactions that regulate development of the thymic medulla, the thymic microenvironment that is critically responsible for central tolerance. The medullary reconstitution induced by adoptive transfer of mature T cells into mice with blocks in T cell development will be used to test the contribution of specific T cell/TEC interactions. We propose to: (1) use MHC class I / MHC class II double KO mice to determine if the expansion and differentiation of the thymic medulla is dependent on TCR/MHC interactions and identify the specific contributions of CD4 SP, CDS SP and Tregs, in this process; (2) use both fetal thymic organ cultures and medullary reconstitution assays in a newly developed Wnt signaling reporter mouse strain, to access the contribution of Wnt signaling in mTEC development and determine if soluble Wnt inhibitory molecules secreted by SP thymocytes inhibit the canonical Wnt signaling pathway in TECs, thereby providing a molecular switch that is necessary for mTEC development from precursor cells. Fully understanding the signaling pathways and cellular interactions which contribute to TEC development and organization will be critical to designing rational therapeutic strategies to counteract age-associated thymic involution and thymic architecture defects associated with autoimmunity. These strategies will also significantly impact the effectiveness of bone marrow transplantation for cancer treatment by counteracting the severe premature thymic degeneration associated with preparative cytoablative treatments including chemotherapy and radiation, as well as post-transplant GVHD.