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CD45+造血细胞在肺先天免疫系统发育和肺血管成熟中的作用。值得注意的是，我们的数据显示胚胎肺包含两组解剖学上不同的CD45+细胞。一个CD45+群体定位于间质，包含早期和晚期巨噬细胞/髓系细胞。这一发现以及显示成熟巨噬细胞在暴露于LPS的分离胚胎肺培养物中出现的数据表明，胚胎肺本身是骨髓分化的一个部位。其他CD45+群体在胎儿晚期（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，呈扁平状，似乎处于与血管壁结合的不同阶段；进一步的研究表明，依赖于缺口3的信号控制着它们的命运。在此，我们提出以下中心假设：一个胎儿CD45+群体在响应间质来源的信号时局部分化，以帮助建立肺部的先天免疫系统，而第二个血管周围CD45+群体直接促进肺动脉壁的成熟。在Aim 1中，我们将重点关注CD45+间充质位点。我们的研究将阐明髓细胞成熟的个体发生机制，并确定产生刺激巨噬细胞和树突状细胞分化信号的肺实质细胞。利用肺胚胎培养，我们将定义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，我们将重点关注血管周围的CD45+细胞。我们将进一步确定它们的表型，评估它们在其他胚胎组织中的分布，并确定PU1依赖性骨髓细胞分化对它们发育的重要性。在最后一组研究中，我们将关注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与功能相关的配体-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肺为呼吸空气做好准备。项目描述：目前，很少或没有关于胎儿循环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部免疫系统的建立，而且还参与肺部血管的发育。因此，这项工作将填补知识上的主要空白，并应该为理解胚胎肺如何装备空气呼吸培养一个新的发展范式。阐明这些发育过程对于推进先天性肺部疾病的治疗以及影响早产儿的特定肺部疾病至关重要。

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.