In vivo function of macrophage in healthy and diseased erythropoiesis

描述(由申请人提供)： 50年前，Marcel Bessis提出了特定的骨髓(BM)微环境促进谱系决定的血液前体细胞分化的概念，他在其开创性研究中描述了红细胞岛，这是一种由处于不同分化阶段的红细胞包围的中央巨噬细胞(M)组成的结构。尽管使用体外重建分析的研究已经清楚地表明骨髓来源的M？在红细胞生成中的作用，但目前没有体内证据表明M？在出生后的红细胞生成中是必需的，甚至是起作用的。体内知识不足的一个主要原因是骨髓M？的定义不明确，而且直到最近，还缺乏特定的遗传模型。我们已经定义了骨髓单核巨噬细胞亚群，并表明CD169M？调节造血干细胞的生态位。我们的初步研究还表明，BM CD169 M？促进了红细胞生成，因为它们在体内的选择性耗竭影响了5-氟尿嘧啶或苯肼诱导的贫血后的红细胞生成恢复。此外，在真性红细胞增多症(PV)的遗传模型中，我们发现突变的JAK2V617F转基因过表达导致红细胞压积正常化，这表明PV的红细胞生成意外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？在健康和疾病红细胞生成中的分子基础和功能。在特定的目标1中，我们将在体内确定调节BM红系生态位(红细胞岛)的分子机制。我们将与DRS M.Narla(NYBC)和J.Chasis(Berkeley)合作对CD169红系母细胞岛进行表征，并通过与M.Merad博士(Mt.西奈半岛)。我们将为先前被认为在红细胞岛(Vcam1，Itgav和Maea)中发挥作用的候选M？受体建立巨噬细胞特异性的遗传模型。在特定的目标2中，我们将研究骨髓M？在慢性疾病红细胞中的作用。我们将与康奈尔大学的S.Rivella博士合作，分析镰状细胞病和地中海贫血等红细胞生成应激的模型。然后，我们将与J.赵博士(俄克拉荷马州)和Tony Green(剑桥)合作，使用第一个目标中创建的M？特异性CD169-DTR耗竭和M？特异性遗传模型，评估巨噬细胞在转基因JAK2V617F模型中的影响。在特定的目标3中，我们将研究扩大中央巨噬细胞在骨髓清除术后的红细胞恢复中的潜在治疗益处。我们将使用转基因模型(与R·斯坦利博士，爱因斯坦合作)和药理学方法(长效IL-4复合体)。这些研究将首次确定骨髓巨噬细胞在红细胞生成中的体内作用，并可能导致调节以红细胞扩张为特征的疾病的红细胞生成的新方法。 (摘要结束)

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)