The Role of KGF in Thymopoiesis

描述（由申请人提供）：患者的能力，特别是 成年人，在疾病或治疗相关的T淋巴细胞再生后， 成熟T淋巴细胞区室的耗竭已经成为一个关键的 临床医学的问题。癌症患者，原发性免疫 缺乏症、HIV或造血干细胞移植（HSCT）接受者 由于长期免疫， 缺陷我们实验室以前的工作表明，T 临床或实验性HSCT后的淋巴细胞生成重现正常胸腺 个体发育对免疫缺陷的人、狗和/或基因敲除小鼠的研究， 证明了胸腺生成依赖于胸腺内产生两种 基质衍生的细胞因子，白细胞介素-7（IL-7）和c-kit配体（KL）。IL-7和 KL是细胞增殖、存活和 未成熟的CD 3-CD 4-CD 8-（“三阴性”，TN）胸腺细胞的分化， 从而允许发育更成熟的胸腺细胞。IL-7和KL是 两者都是由胸腺上皮细胞（TEC）在胸腺中产生的， 通过免疫表型分离。胸腺生成缺陷的一种机制 HSCT后观察到的是辐射或化疗诱导的TEC杀伤 产生IL-7和KL。结果，胸腺细胞分化的进展 从Tn期开始是有限的，胸腺生成是有缺陷的。总局 HSCT后重组IL-7或骨髓基质细胞共移植 已经用IL-7基因逆转录病毒转导的细胞导致 显著改善HSCT后的胸腺生成和免疫重建， 鼠模型。胸腺TEC损伤的一般病理生理模型 不足表明，调节TEC的存活或恢复后， HSCT对于HSCT后的胸腺生成至关重要。角质细胞生长因子 是酸性成纤维细胞生长因子家族的成员， 促进上皮细胞的增殖、存活和分化。 在化疗或放疗前给予KGF已被证明 改善粘膜、皮肤和肺毒性，同时还降低 移植物抗宿主病（GVHD）的发生率和严重程度。像其他 上皮细胞、成熟TEC表达KGF受体（KGFR），而胸腺细胞和 胸腺成纤维细胞表达KGF。移植前KGF给药导致 持续正常化的胸腺生成能力和产生 抗原特异性T淋巴细胞。KCF通过增加HSCT后 IL-7产生。本批拨款建议的研究，将测试 假设胸腺内KGF信号传导调节正常的胸腺生成， 以及辐射后和HSCT后的胸腺恢复。这些研究将 评估KGF处理的HSCT中TEC恢复的机制 受体小鼠KGF敲除小鼠和在其细胞中诱导表达KGF的小鼠， 胸腺细胞和T淋巴细胞将用于测试胸腺细胞衍生的 KGF在正常和HSCT后胸腺生成中的作用这些研究将提供重要的 关于胸腺微环境如何维持的信息， 从细胞毒性损伤中恢复，以及胸腺细胞如何影响 他们的微环境。

DESCRIPTION (provided by applicant): The ability of patients, especially adults, to regenerate T lymphocytes after disease- or treatment-related depletion of the mature T lymphocyte compartment has emerged as a critical problem in clinical medicine. Patients with cancer, primary immune deficiencies, HIV, or recipients of hematopoietic stem cell transplants (HSCT) suffer significant morbidity and mortality because of prolonged immune deficiency. Previous work in our laboratory has demonstrated that T lymphopoiesis after clinical or experimental HSCT recapitulates normal thymic ontogeny. Studies of immunodeficient humans, dogs and/or knockout mice have demonstrated that thymopoiesis depends on the intrathymic production of two stroma-derived cytokines, interleukin-7 (IL-7) and c-kit ligand (KL). IL-7 and KL are synergistically required for the proliferation, survival and differentiation of immature CD3-CD4-CD8- ("triple negative," TN) thymocytes, thereby permitting the development of more mature thymocytes. IL-7 and KL are both produced in the thymus by thymic epithelial cells (TEC), which can be isolated by immunophenotype. Once mechanism for the defective thymopoiesis observed after HSCT is the radiation or chemotherapy-induced killing of the TEC which make IL-7 and KL. As a result, progression of thymocyte differentiation from the Tn stage is limited and thymopoiesis is defective. Administration of either recombinant IL-7 after HSCT, or co-transplantation of marrow stromal cells which have been retrovirally transduced with the IL-7 gene results in significantly improved post-HSCT thymopoiesis and immune reconstitution in murine models. The general pathophysiologic model of TEC damage causing thymic insufficiency suggests that regulation of survival or recovery of the TEC after HSCT is critical for post-HSCT thymopoiesis. Keratinocyte growth factor (KGF) is a member of the acidic fibroblastic growth factor family which specifically promotes the proliferation, survival and differentiation of epithelial cells. Administration of KGF before chemotherapy or radiation has been shown to ameliorate the mucosal, cutaneous, and pulmonary toxicity while also decreasing the incidence and severity of graft-versus-host disease (GVHD). Like other epithelial cells, mature TEC express KGF receptors (KGFR) while thymocytes and thymic fibroblasts express KGF. Pre-transplant KGF administration caused sustained normalization of thymopoietic capacity and generation of antigen-specific T lymphocytes. KCF exerted its effects by increasing post-HSCT IL-7 production. The proposed studies in the present grant will test the hypothesis that intrathymic KGF signaling regulates both normal thymopoiesis as well as thymic recovery after radiation and after HSCT. The studies will evaluate the mechanism by which TEC recovery occurs in KGF treated HSCT recipient mice. KGF knockout mice and mice which inducibly express KGF in their thymocytes and T lymphocytes will be used to test the role of thymocyte-derived KGF in normal and post-HSCT thymopoiesis. The studies will provide important information regarding how the thymic microenvironment is maintained and recovered from cytotoxic injury, and how thymocytes influence the development of their microenvironment.