The Role of KGF in Thymopoiesis

描述(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情况下再生T淋巴细胞 成熟T淋巴细胞的耗尽已成为一个关键因素 临床医学中存在的问题。癌症患者，初级免疫 造血干细胞移植(HSCT)的缺陷、艾滋病毒或接受者 由于长时间的免疫而遭受严重的发病率和死亡率 缺乏症。我们实验室以前的工作已经证明T 临床或实验性HSCT重建正常胸腺后的淋巴细胞生成 个体发育学。对免疫缺陷的人类、狗和/或基因敲除小鼠的研究 证明胸腺的生成依赖于胸腺内产生的两种 基质来源的细胞因子、白介素7(IL-7)和c-kit配体(KL)。IL-7和 KL对细胞的增殖、存活和 未成熟的CD3-CD4-CD8-(三阴性，TN)胸腺细胞的分化， 从而允许发育出更成熟的胸腺细胞。IL-7和KL是 两者都是由胸腺上皮细胞(TEC)产生的，胸腺上皮细胞可以 通过免疫表型分离。胸腺生成缺陷的ONCE机制 HSCT后观察到放射或化疗诱导的TEC杀伤 从而产生IL-7和KL。结果，胸腺细胞分化的进展 从TN阶段开始是有限的，胸腺的生成是有缺陷的。管理 造血干细胞移植后重组IL-7或骨髓基质联合移植 逆转录病毒转导IL-7基因的细胞导致 显著改善HSCT后的胸腺生成和免疫重建 小鼠模型。TEC损伤致胸腺损伤的一般病理生理模型 不足提示，对TEC存活或恢复的调控 HSCT对HSCT后的胸腺生成至关重要。角质形成细胞生长因子 是酸性成纤维细胞生长因子家族的成员，该家族具有特异性 促进上皮细胞的增殖、存活和分化。 在化疗或放疗前服用KGF已被证明对 改善粘膜、皮肤和肺的毒性，同时也减少 移植物抗宿主病(GVHD)的发生率和严重程度。像其他人一样 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。移植前给予KGF导致 胸腺生成能力的持续正常化和 抗原特异性T淋巴细胞。KCF通过增加HSCT后的数量发挥其作用 IL-7的生产。目前拨款中建议的研究将测试 胸腺内KGF信号调节正常胸腺生成的假说 放疗后胸腺和造血干细胞移植后胸腺恢复良好。这些研究将 评价KGF治疗的HSCT中TEC恢复的机制 受体小鼠。KGF基因敲除小鼠和在其体内诱导表达KGF的小鼠 胸腺细胞和T淋巴细胞将被用来测试胸腺细胞来源的作用 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 有关胸腺微环境如何维持的信息，以及 从细胞毒性损伤中恢复，以及胸腺细胞如何影响发育 它们的微环境。

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.