Hematopoeitic cell fates in the developing lung

描述（由申请人提供）：在本提案中，我们试图了解外源性CD 45+造血细胞在肺先天免疫系统发育和肺血管系统成熟中的作用。值得注意的是，我们的数据显示，胚胎肺包含2个解剖学上不同的CD 45+细胞集。一个CD 45+群体定位于间充质，包含早期和晚期巨噬细胞/骨髓谱系的细胞。这一发现沿着显示成熟巨噬细胞在暴露于LPS的分离的胚胎肺培养物中出现的数据，表明胚胎肺本身是髓样分化的部位。另一种CD 45+细胞群在胎儿晚期（E18）最为明显，聚集在肺动脉分支周围。这些细胞中的许多共表达平滑肌肌动蛋白，是扁平的，并且似乎处于并入血管壁的各个阶段;进一步的工作表明，notch-3依赖性信号传导控制它们的命运。在此，我们提出了以下中心假设：一个胎儿CD 45+群体局部分化，以响应间充质来源的信号，以帮助建立肺的先天免疫系统，而第二血管周围的CD 45+群体直接有助于肺动脉壁的成熟。在目标1中，我们将重点关注CD 45+间充质位点。我们的研究将阐明骨髓细胞成熟的个体发生，并确定肺实质细胞产生刺激巨噬细胞和树突状细胞分化的信号。使用肺胚胎培养物，我们将确定巨噬细胞和树突状细胞分化的精确区域，并评估肺上皮在这些事件中的作用。在目标2中，我们将关注血管周围的CD 45+细胞。我们将进一步定义它们的表型，评估它们在其他胚胎组织中的分布，并确定PU 1依赖的髓样细胞分化对其发育的重要性。在最后一组研究中，我们将重点关注notch-3在细胞命运决定中的作用，并确定在该细胞群中起作用的功能相关配体-notch-3结合相互作用。通过这项工作，我们将阐明发育中的肺和造血系统之间的相互作用如何确保新生的肺为呼吸空气做好准备。项目叙述：目前，很少或没有关于来自胎儿循环的细胞如何促进肺发育的信息。我们的研究表明，这些细胞不仅参与肺免疫系统的建立，而且还参与肺血管的发育。因此，这项工作将填补知识的主要空白，并应促进一个新的发展范式，了解胚胎肺如何成为装备空气呼吸。阐明这些发育过程对于推进先天性肺部疾病和折磨早产儿的特定肺部疾病的治疗至关重要。

DESCRIPTION (provided by applicant): In this proposal, we seek to understand the role of exogenously derived CD45+ hematopoeitic cells in the development of the lung's innate immune system, and in the maturation of the pulmonary vasculature. Notably, our data show that the embryonic lung contains 2 anatomically distinct sets of CD45+ cells. One CD45+ population localized to the mesenchyme, contains cells of early and late macrophage/myeloid lineage. This finding along with data showing that mature macrophages emerge in isolated embryonic lung cultures exposed to LPS, suggest that the embryonic lung itself is a site of myeloid differentiation. The other CD45+ population is most apparent in late fetal life (E18), aggregated around branches of the pulmonary artery. Many of these cells co-express smooth muscle actin, are flattened, and appear to be in various stages of incorporation into the vessel wall; further work suggests that notch-3 dependent signaling controls their fate. Herein, we propose the following central hypothesis: one fetal CD45+ population locally differentiates in response to mesenchyme-derived signals to help establish the lung's innate immune system, whereas the second peri-vascular CD45+ population directly contributes to maturation of the pulmonary artery wall. In Aim 1, we will focus on the CD45+ mesenchymal site. Our studies will clarify the ontogeny of myeloid cell maturation and identify lung parenchymal cells that produce signals stimulating macrophage and dendritic cell differentiation. Using lung embryonic cultures, we will then define the precise regions of macrophage and dendritic cell differentiation, and evaluate the role of the lung epithelium in these events. In Aim 2 we will focus on the peri-vascular CD45+ cells. We will further define their phenotype, evaluate their distribution in other embryonic tissues, and determine the importance of PU1 dependent myeloid cell differentiation for their development. In the final set of studies, we will focus on the role of notch-3 in cell fate determination and identify the functionally relevant ligand-notch-3 binding interaction that is operative in this cell population. Through this work, we will clarify how interactions between the developing lung and the hematopoeitic system ensure that the newly born lung is ready for air-breathing. PROJECT NARRATIVE: Currently, there is little or no information regarding how cells derived from the fetal circulation contribute to lung development. Our studies suggest that such cells are not only involved in establishment of the lung's immune system, but are also involved in development of the lung's blood vessels. This work will, thus, fill in major gaps in knowledge and should foster a new developmental paradigm for understanding how the embryonic lung becomes equipped air breathing. Elucidating these developmental processes is critical for advancing the treatment of congenital lung diseases, and the specific lung diseases that afflict premature infants.