Cellular crosstalk in the hematopoietic microenvironment

摘要： 我们的总体目标是确定产生TNFα的造血细胞调节 血管和血管周围HSPC（造血干细胞和祖细胞）血管龛。HSPC是 负责产生血液中发现的所有细胞，是生命不可缺少的。HSPC位于 与由不同类型细胞组成的特定结构（龛）相关的骨髓，包括 内皮细胞、CD 45-CD 31-LepR+、CD 45-CD 31-Ng 2+细胞和巨核细胞。这些壁龛保持着 调节HSPC，是HSC维护不可缺少的。然而，人们对这些机制知之甚少， 在体内平衡和再生过程中调节生态位的不同组成部分。识别这些 机制对于了解HSPC在健康和疾病中的调节方式至关重要，因为它可能导致 新的治疗方法来治疗疾病。 在我们的初步研究中，我们发现了两种TNF α产生细胞的全新功能， 造血：1）我们发现骨髓（而不是外周）粒细胞使用TNF α产生一个 促进维持造血的基质小生境扩张的再生微环境 并加速小鼠自体移植后的造血恢复。我们的结果表明 粒细胞和/或TNF α信号的操纵可用于加速供体细胞移植后的移植。 移植我们还发现，在人类β地中海贫血患者中， 初始移植物预测更快的外周和中性粒细胞植入。这一数据支持了以下假设： 粒细胞也可能在驱动人类患者的再生中发挥作用。2)我们发现TNF-α- 产生细胞控制血管周围小生境的大小和HSC在BM小生境中的定位。我们的结果 表明，在体内平衡过程中，TNF α产生细胞通过控制血管微生态位丰度来调节血管微生态位丰度。 龛内内皮细胞和血管周围细胞的数量。我们还发现，在TNFα-/-小鼠中，HSC 远离血管周围的壁龛。在这项建议中，我们研究了这种TNF α介导的机制， 蜂窝串话在目标1中，我们将研究粒细胞驱动血管和 造血再生，它们在血管内稳态中的功能，以及药物操作是否 可以利用这些粒细胞来促进骨髓消融后的再生。在本提案的目标2中， 将利用嵌合小鼠和遗传模型进行Tnfrsf 1a（TNF α受体之一）再活化和TNFα 缺失和HSC及其小生境的5色免疫荧光成像，以确定来源和靶点 调节HSC功能和定位于小生境的TNF α。

Abstract: Our overall goal is to identify the mechanisms through which TNFα-producing hematopoietic cells regulate blood vessels and perivascular HSPC (Hematopoietic stem and progenitor cells) vascular niches. HSPC are responsible for generating all the cells found in the blood and are indispensable for life. HSPC reside in the bone marrow associated with specific structures (niches) composed by different types of cells including endothelial cells, CD45-CD31-LepR+, CD45-CD31-Ng2+ cells and megakaryocytes. These niches maintain and regulate HSPC and are indispensable for HSC maintenance. However, little is known about the mechanisms that regulate the different components of the niche during homeostasis and regeneration. Identifying these mechanisms is critical to understand how HSPC are regulated in health and disease and because it might lead to novel therapies that target the niche to treat disease. In our preliminary studies we have discovered two entirely novel functions for TNF-producing cells in hematopoiesis: 1) We found that bone marrow (but not peripheral) granulocytes use TNF to create a regenerative microenvironment that promotes the expansion of the stromal niches that sustain hematopoiesis and accelerates hematopoietic recovery after autologous transplantation in mice. Our results suggest that manipulation of granulocytes and/or TNF signals can be used to accelerate donor cell engraftment after transplantation. We also found, in human beta thalassemia patients, that higher numbers of granulocytes in the initial graft predicted faster peripheral and neutrophil engraftment. This data supports the hypothesis that granulocytes might also play a role in driving regeneration in human patients. 2) We found that TNF- producing cells control the size of the perivascular niche and HSC localization to BM niches. Our results demonstrate that, during homeostasis, TNF-producing cells regulate vascular niche abundance by controlling the numbers of endothelial cells and perivascular cells in the niche. We also found that, in Tnfα-/- mice, HSC relocate away from perivascular niches. In this proposal we investigate the mechanisms of this TNF-mediated cellular crosstalk. In Aim 1 we will investigate the mechanisms through which granulocytes drive vascular and hematopoietic regeneration, their function in vascular homeostasis, and whether pharmacological manipulation of these granulocytes can be utilized to promote regeneration after myeloablation. In Aim 2 of this proposal we will utilize chimeric mice and genetic models for Tnfrsf1a (one of the TNF receptors) reactivation and Tnfα deletion and a 5-color immunofluorescence imaging of HSC and their niches to identify the source and targets of TNF that regulate HSC function and localization to the niche.