Contribution of macrophages in the HSC niche

项目概要： 我们实验室以前的研究表明，骨髓（BM）中的CD 169+巨噬细胞 通过调节基质细胞中CXCL 12的合成来促进造血干细胞（HSC）的生态位活性， 在BM中的保留。初步结果揭示了巨噬细胞在直接调节细胞增殖中的两种新功能。 HSC功能。首先，我们提供的证据表明，巨噬细胞是至关重要的HSC再生后，遗传毒性， 通过调节肠道微生物群信号介导的铁可用性来挑战。二是 发现BM巨噬细胞可以转移到HSC/祖细胞的关键保留信号，赋予在BM中的居留。 事实上，已经接受巨噬细胞转移的HSC保留在BM中，而只有那些 在G-CSF给药后，未从BM微环境中动员。这些结果提高了 关于巨噬细胞在调节HSC、RBC和HSC中的各种功能是否是重要的新问题， 生产，或清除是由相同的细胞实现的，或者BM巨噬细胞是否具有专门的 功能协调发展的在这个提议中，我们将探讨巨噬细胞可以直接促进生态位的假设， 通过调节HSC再生和从BM排出的能力来调节HSC的活性。具体目标1： 研究巨噬细胞如何与微生物群相互作用以促进HSC再生。我们将使用基因 模型来操纵HSC和巨噬细胞中的铁传递途径，以剖析铁 在造血再生期间供应给HSC/祖细胞。我们还将评估BM巨噬细胞如何 可以感知来自微生物群的信号。在具体目标2中，我们将研究 巨噬细胞分配骨髓驻留。我们将评估连接蛋白在细胞间通讯中的作用 使用CRISPR/Cas9介导的靶向，并确定胞啃作用作为转移机制的作用。在特定 目的3：进一步明确骨髓巨噬细胞的分布。我们将评估空间 这些巨噬细胞与血管结构，HSC和成红细胞的关系，使用免疫荧光 显像我们将使用遗传学方法研究BM驻留巨噬细胞的起源（胚胎或造血）。 追踪方法这些研究将揭示一个未被充分认识的组成部分的关键功能， HSC利基并发现血液疾病的新治疗方法。

PROJECT SUMMARY: Previous studies from our laboratory have suggested that CD169+ macrophages of the bone marrow (BM) contribute to the hematopoietic stem cell (HSC) niche activity by regulating CXCL12 synthesis in stromal cells and their retention in the BM. Preliminary results reveal two novel functions of macrophages in directly regulating the HSC function. First, we provide evidence that macrophages are critical for HSC regeneration after genotoxic challenge via the regulation of iron availability mediated by signals from the gut microbiota. Second, we have found that BM macrophages can transfer to HSCs/progenitors key retention signals that confer residence in BM. Indeed, HSCs that have received the transfer from macrophages are retained in the BM, whereas only those that have not are mobilized from the BM microenvironment following G-CSF administration. These results raise important new questions as to whether the various functions of macrophages in regulating HSCs, RBC production, or clearance are achieved by the same cells or whether the BM macrophages have specialized functions. In this proposal, we will explore the hypothesis that macrophage can directly contribute to niche activities by regulating HSCs’ ability to regenerate and to egress from the BM. In Specific Aim 1, we will investigate how macrophages interact with the microbiota to promote HSC regeneration. We will use genetic models to manipulate iron delivery pathways in HSCs and macrophages to dissect the mechanism by which iron is supplied to HSCs/progenitors during hematopoietic regeneration. We will also evaluate how BM macrophages can sense signals from the microbiota. In Specific Aim 2, we will investigate the mechanisms by which macrophages assign bone marrow residence. We will assess the role of connexins in the cell-cell communication using CRISPR/Cas9-mediated targeting and determine the role of trogocytosis as transfer mechanism. In Specific Aim 3, we will further define the bone marrow-resident macrophage population. We will evaluate the spatial relationship of these macrophages with vascular structures, HSCs and erythroblasts using immunofluorescence imaging. We will investigate the origin (embryonic or hematopoietic) of BM- resident macrophages using genetic tracing methods. These studies will shed light into the critical functions of an under-appreciated component of the HSC niche and uncover new therapeutic approaches for blood disorders.