Inflammatory Regulation of Hematopoietic Stem and Progenitor Cells to Enhance Innate Immunity

项目摘要/摘要 中性粒细胞减少症是某些白细胞的缺陷，是化疗的一种常见副作用，暴露出 患者死于机会性感染的风险很高。恢复中性粒细胞的现有方法，包括 G-CSF注射和粒细胞输注在结果上没有产生明显的改善，而且新的 我们需要一些方法。白细胞是骨髓造血干/祖细胞的产物 细胞(HSPC)，可通过循环炎症信号触发分裂和分化。我们的前辈 研究表明，炎性细胞因子干扰素-γ(IFNG)对造血有很强的刺激作用 干细胞(HSC)分裂和髓系分化。然而，持续的IFNG暴露抑制了HSC的自我更新， 最终导致骨髓衰竭。无论是造血干细胞还是其后代，多能祖细胞(MPP)， 也同样对IFNG作出反应尚不清楚。此外，缺乏对信号转导的分子理解 IFNG诱导的促进HSPC分化的途径对利用HSPC的前免疫功能构成了障碍 在防止有害影响的同时进行IFNG。在前期工作中，我们鉴定了干扰素诱导的造血干细胞基因。 刺激，我们通过功能获得和功能丧失的研究表明，示范基因可以关键地调节 HSPC分化。因此，我们假设IFNG诱导的转录变化可以被用来激活 静止的HSCs产生更多的中性粒细胞，从而提高从感染中恢复的能力。其基本原理是 在HSCs中有调控地诱导特定的IFNG靶标可能会增强短期骨髓生成 扰乱了长期的骨髓功能。设计了三个目标来描述动力学、机制、 依赖IFNG的HSPC分化结果。在目标1中，我们将衡量HSC的贡献 与IFNG刺激后循环粒细胞的MPPS进行比较，从而揭示了 在这些HSPC亚型中，作为中性粒细胞来源的HSPC是最有效的。在目标2中，我们将评估IFNG诱导 功能丧失、异种移植和功能生化在HSPC分化中的作用因素 学习。最后，在目标3中，我们将测试IFNG诱导HSPC髓系分化在病原体中的作用 用A组链球菌性肌炎小鼠模型清除。目标3中的研究将通过以下方式通知，但 不依赖于目标1和目标2的结果。这些研究将提供必要的关键机制数据 设计新的以干细胞为基础的治疗中性粒细胞减少症的方法，并可能揭示对骨髓的新见解 由于过度炎症而导致的衰竭综合症。

Project Summary / Abstract Neutropenia, a deficiency in certain white blood cells, is a common side effect of chemotherapy that exposes patients to a high risk of death from opportunistic infections. Existing methods to restore neutrophils, including G-CSF administration and granulocyte infusions, have not produced a clear improvement in outcome, and new approaches are needed. White blood cells are the product of bone marrow hematopoietic stem and progenitor cells (HSPCs) that can be triggered to divide and differentiate by circulating inflammatory signals. Our prior work shows that the inflammatory cytokine interferon gamma (IFNg) is a potent stimulus for hematopoietic stem cell (HSC) division and myeloid differentiation. Yet persistent IFNg exposure inhibits HSC self-renewal, eventually leading to bone marrow failure. Whether HSCs or their progeny, the multipotent progenitors (MPPs), are equally responsive to IFNg is unknown. Furthermore, a lack of molecular understanding of signaling pathways induced by IFNg to promote HSPC differentiation poses a barrier to utilizing proimmune functions of IFNg while preventing deleterious effects. In preliminary work we identify genes induced in HSCs upon IFNg stimulation, and we show by gain- and loss-of-function studies that an exemplary gene can critically regulate HSPC differentiation. Thus we hypothesize that IFNg-induced transcriptional changes can be used to activate quiescent HSCs to produce more neutrophils, resulting in improved recovery from infection. The rationale is that regulated induction of specific IFNg targets in HSCs may enhance short-term myelopoiesis without disrupting long-term bone marrow function. Three aims are designed to characterize the kinetics, mechanism, and outcome of IFNg-dependent HSPC differentiation. In Aim 1, we will measure the contribution of HSCs versus MPPs to circulating granulocytes after IFNg stimulation using lineage-tracing, thereby revealing which of these HSPC subtypes is most potent as a source of neutrophils. In Aim 2, we will evaluate IFNg-inducible factors for their role in HSPC differentiation using loss of function, xenotransplant, and functional biochemical studies. Finally, in Aim 3, we will test the utility of IFNg-induced HSPC myeloid differentiation in pathogen clearance using a mouse model of Group A Streptococcal myositis. Studies in Aim 3 will be informed by, but not dependent on, results of Aims 1 and 2. These studies will provide critical mechanistic data needed to design novel stem cell-based therapies for neutropenic fever and may reveal new insights into bone marrow failure syndromes that result from excessive inflammation.