ROLE OF THE G-CSF RECEPTOR IN PROGENITOR MOBILIZATION

调控造血干细胞（HSC）增殖、自我更新和分化的机制是 这是我们理解和治疗许多造血系统疾病的基础， 骨髓衰竭综合征和造血系统恶性肿瘤。越来越多的证据表明， 骨髓中的细胞提供调节HSC的关键信号，然而这些信号的性质，甚至是细胞的增殖， 构成干细胞小生境的基质细胞类型知之甚少。我们实验室的最新研究 显示用粒细胞集落刺激因子（G-CSF）治疗导致骨中的显著变化 骨髓微环境，最终动员HSC进入血液。在这份提案中，我们计划 继续这项研究，以回答以下两个问题：1）什么是茎的细胞成分 细胞龛; 2）调节干细胞龛细胞数量和功能的信号是什么。本研究 与干细胞移植有直接的临床相关性，因为它可能导致增加HSC的新策略 动员产量和增强HSC归巢和移植后的植入。 初步的数据支持这一假设，即由单核细胞谱系的细胞产生的因子在单核细胞中的表达与单核细胞谱系的表达有关。 骨髓提供调节成骨细胞功能/存活关键信号， 因子受G-CSF调节。在目标1中，我们将鉴定由单核细胞产生的候选因子， 表征它们对G-CSF诱导的HSC动员和成骨细胞抑制的贡献。的 鉴定调节成骨细胞的因子可能导致小分子模拟物（或 拮抗剂），能够刺激（或抑制）成骨细胞（和可能的HSC）功能。 趋化因子Cxcl 12提供了调节HSC静止、存活和运输的关键信号。内 在骨髓中，Cxcl 12在成骨细胞、成骨细胞前体细胞、内皮细胞中表达，并且Cxcl 12- 丰富的网状（CAR）细胞。在目标2中，我们将在选定的基质细胞类型中选择性缺失Cxcl 12， 描述它们对HSC功能和运输的影响。为此，我们培育了转基因小鼠 携带Cxcl 12的floxed无效等位基因。这些研究应该提供新的见解细胞组成的 干细胞的生态位，并可能导致更好的策略，以增加造血干细胞的功能，在骨髓衰竭 综合征或干细胞移植后。提出了以下具体目标。 目标1。我们将确定骨髓单核细胞/巨噬细胞通过G- 脑脊液。 目标2.我们将确定成骨细胞和内皮细胞表达Cxcl 12对HSC的贡献， 功能和贩运。

The mechanisms regulating hematopoietic stem cell (HSC) proliferation, self-renewal, and differentiation are fundamental to our understanding and treatment of a number of hematopoietic disorders, including bone marrow failure syndromes and hematopoietic malignancies. Accumulating evidences suggests that stromal cells in the bone marrow provide key signals regulating HSC, yet the nature of these signals and even the stromal cell types that comprise the stem cell niche are poorly understood. Recent studies from our laboratory show that treatment with granulocyte colony-stimulating factor (G-CSF) results in marked changes in the bone marrow microenvironment that culminate in the mobilization of HSC into the blood. In this proposal, we plan to continue this research to answer the two following questions: 1) what are the cellular components of the stem cell niche; 2) what are the signals that regulate the number and function of stem cell niche cells. This research has direct clinical relevance for stem cell transplantation, since it may lead to novel strategies to increase HSC mobilization yields and enhance HSC homing and engraftment following transplantation. Preliminary data support the hypothesis that factor(s) produced by cells of the monocyte lineage in the bone marrow provide key signals that regulate osteoblast function/survival and that expression of these factor(s) is regulated by G-CSF. In Aim 1, we will identify candidate factors produced by monocytic cells and characterize their contribution to G-CSF-induced HSC mobilization and osteoblast suppression. The identification of factors that regulate osteoblasts may lead to the development of small molecule mimetics (or antagonists) that are able to stimulate (or inhibit) osteoblast (and possibly HSC) function. The chemokine Cxcl12 provides a key signal regulating HSC quiescence, survival, and trafficking. Within the bone marrow, Cxcl12 is expressed in osteoblasts, osteoblast precursors, endothelial cells, and Cxcl12- abundant reticular (CAR) cells. In Aim 2, we will selectively delete Cxcl12 in selected stromal cel types and characterize their effect on HSC function and trafficking. To this end, we have generated transgenic mice carrying a floxed null allele of Cxcl12. These studies should provide new insight into the cellular composition of the stem cell niche and may lead to better strategies to augment HSC function in bone marrow failure syndromes or after stem cell transplantation. The following specific aims are proposed. Aim 1. We will define the contribution of bone marrow monocytes/macrophages to HSC mobilization by G- CSF. Aim 2. We will define the contribution of Cxcl12 expression by osteoblasts and endothelial cells to HSC function and trafficking.