In vivo function of macrophage in healthy and diseased erythropoiesis

描述（由申请人提供）： Marcel Bessis在50年前提出了特定的骨髓（BM）微环境促进谱系定型的血液前体分化的概念，其中他在开创性研究中描述了成红细胞岛，一种由处于不同分化阶段的成红细胞包围的中央巨噬细胞（M）构成的结构。虽然使用体外重建分析的研究已经明确表明骨髓来源的M？在红细胞生成中的作用，但目前没有体内证据表明M？是必需的，甚至在出生后红细胞生成中发挥作用。体内知识缺乏的一个主要原因是BM M的性质定义不清，直到最近，缺乏特定的遗传模型。我们已经定义了BM单核吞噬细胞的亚群，并表明CD 169 + M？调节造血干细胞生态位。我们的初步研究还表明，BM CD 169 + M？促进红细胞生成，因为它们在体内的选择性消耗损害了5-氟尿嘧啶或苯肼诱导的贫血后的红细胞生成恢复。此外，在来自突变JAK 2 V617 F的转基因过表达的真性红细胞增多症（PV）的遗传模型中，我们发现M耗竭使红细胞压积正常化，这表明PV中的红细胞生成出乎意料地依赖于来自微环境的信号。基于这些初步结果，我们建议进一步评估BM M？在健康和患病红细胞生成中的分子基础和功能。在具体目标1中，我们将定义体内调节BM红细胞龛（成红细胞岛）的分子机制。我们将与Dr M合作表征CD 169+成红细胞岛。Narla（NYBC）和J. Chasis（Berkeley），并通过流式细胞术和转录谱分析与M.梅拉德山（Mt. Sinai）。我们将产生巨噬细胞特异性的遗传模型的候选人M？受体先前建议发挥作用的成红细胞岛（Vcam 1，Itgav，和Maea）。在具体目标2中，我们将研究骨髓M？在慢性疾病中的作用。我们将分析红细胞生成应激的模型，如镰状细胞病和地中海贫血，后者与S。Rivella（Cornell）.然后，我们将与J. Zhao博士（俄克拉荷马州）和Tony绿色（剑桥大学）合作，使用第一个目标中产生的M？特异性CD 169-DTR耗竭和M？特异性遗传模型，评估转基因JAK 2 V617 F模型中巨噬细胞的影响。在具体目标3中，我们将检查骨髓消融术后扩大中央巨噬细胞在红细胞生成恢复中的潜在治疗获益。我们将使用转基因模型（与R. Stanley，Einstein）和药理学方法（长效IL-4复合物）。这些研究将首次定义BM巨噬细胞在红细胞生成中的体内作用，并可能导致在以红细胞扩增为特征的疾病中调节红细胞生成的新方法。 (End摘要）

DESCRIPTION (provided by applicant): The notion that a specific bone marrow (BM) microenvironment promotes the differentiation of lineage- committed blood precursors was suggested 50 years ago by Marcel Bessis where he described in seminal studies the erythroblastic island, a structure made of a central macrophage (M) surrounded by erythroblasts at varying stages of differentiation. Although studies using in vitro reconstitution analyses have clearly suggested a role for marrow-derived M¿ in erythropoiesis, there is currently no in vivo evidence that M¿ are required or even play a role in postnatal erythropoiesis. A major reason for the deficit of in vivo knowledge stems from the poorly defined nature of BM M¿ and, until recently, the lack of specific genetic models. We have defined subsets of BM mononuclear phagocytes and showed that CD169+ M¿ regulated the hematopoietic stem cell niche. Our preliminary studies also suggest that BM CD169+ M¿ promote erythropoiesis since their selective in vivo depletion compromised erythropoietic recovery after 5-fluorouracil- or phenylhydrazine-induced anemia. Additionally, in a genetic model of polycythemia vera (PV) from transgenic overexpression of mutated JAK2V617F, we have found that M¿ depletion normalized the hematocrit, suggesting that erythropoiesis in PV, unexpectedly, depends on signals from the microenvironment. Based on these preliminary results, we propose to evaluate further the molecular basis and function of BM M¿ in healthy and diseased erythropoiesis. In Specific Aim 1, we will define in vivo molecular mechanisms regulating the BM erythroid niche (erythroblastic island). We will characterize CD169+ erythroblastic islands in collaboration with Drs M. Narla (NYBC) and J. Chasis (Berkeley) and get new insight on central M¿ by flow cytometry and transcriptional profiling collaboration with Dr. M. Merad (Mt. Sinai). We will generate macrophage-specific genetic models for candidate M¿ receptors previously suggested to play a role in the erythroblastic island (Vcam1, Itgav, and Maea). In Specific Aim 2, we will examine the contribution of bone marrow M¿ in chronically diseased erythron. We will analyze models of erythropoietic stress such as sickle cell disease and thalassemia, the latter in collaboration with Dr. S. Rivella (Cornell). We will then evaluate the impact of macrophage in transgenic JAK2V617F models in collaboration with Dr. J. Zhao (Oklahoma) and Tony Green (Cambridge) using M¿-specific CD169-DTR depletion and M¿-specific genetic models generated in the first aim. In Specific Aim 3, we will examine the potential therapeutic benefit of expanding the central macrophage in the erythropoietic recovery after myeloablation. We will use transgenic models (Csf1 overexpression in collaboration with Dr. R. Stanley, Einstein) and pharmacological approaches (long-acting IL-4 complexes). These studies will define for the first time the in vivo roles of BM macrophages in erythropoiesis and will likely lead to novel ways to regulate erythropoiesis in diseases characterized by erythron expansion. (End of Abstract)