Diverse Homeostatic Roles for Distinct Macrophages in the Developing Lung Vasculature

肺泡化是肺发育的最后阶段，主要发生在出生后，显著增加 气体交换表面积。早期通过血管生成快速生长的肺血管 肺泡化推动远端肺生长，血管生成障碍损害肺泡化。在其他器官中， 特化巨噬细胞通过促进血管形成、提供存活和 向EC的迁移提示，并促进血管吻合。然而，巨噬细胞在血管紧张性疾病中的作用 发展中的肺血管系统仍然完全未知。我们最近开始了一个项目，雇用了 单细胞RNA测序用于确定胚胎晚期和出生后早期肺中巨噬细胞的多样性 发展。巨噬细胞是极其异质性的，具有不同的表型，这些表型是谱系和组织- 具体的，并且受微环境的影响很大。该提案中的初步数据表明， 出生后巨噬细胞多样性极大增加。存在特化的、高度增殖的巨噬细胞 出生前和出生后被复杂和动态的不同巨噬细胞亚型的混合物所取代 表现出独特的基因特征，基因表达的发育梯度，以及在 肺提示在组织重塑、血管生成和免疫方面有不同的功能。有趣的是， 胚胎巨噬细胞被发现完全包围小动脉并表达许多基因，这些基因 调节肺分支、血管生成和EC表型。出生后，这些细胞转变为中间体 亚群只存在于出生后的头几周，表达额外的组织重塑基因。 综上所述，我们的数据提出了不同的巨噬细胞群支持肺泡化的假设。 通过表达影响血管生长的因子来调节肺血管的发育 以及改建，这将通过三个具体目标进行测试。目标1将在现场合并多路复用 杂交，谱系追踪，原代EC和巨噬细胞的研究，以及转基因和 基因敲除小鼠确定特定巨噬细胞亚群在调节EC表型和调节肺中的作用 实质和血管生长。AIM 2将利用多重原位杂交，条件基因敲除小鼠 从肺内皮细胞和巨噬细胞到探测通路的单细胞数据集的模型和配体-受体图谱 介导巨噬细胞与内皮细胞的通讯。最后，目标3将确定慢性高氧血症是否会改变多样性和 肺巨噬细胞在急性损伤和恢复后的表型，特别是损伤 肺巨噬细胞的发育和动态平衡功能。这些研究的成功完成将 对肺巨噬细胞在胚胎和出生后早期的不同功能提供多方面的观点 在单细胞分辨率下的发展，并确定可以直接转化为小说的新途径 以肺损害为特征的疾病中调节血管生长和再生的策略 血管生成。

Alveolarization, the final stage of lung development occurring primarily postnatally, markedly increases gas exchange surface area. Rapid growth of the pulmonary vasculature by angiogenesis during early alveolarization drives distal lung growth, and disrupted angiogenesis impairs alveolarization. In other organs, specialized macrophages support angiogenesis by promoting blood vessel formation, providing survival and migratory cues to EC, and facilitating vascular anastomoses. However, the role of macrophages in the developing pulmonary vasculature remains entirely unknown. We recently embarked on a project employing single cell RNA-sequencing to define macrophage diversity during late embryonic and early postnatal lung development. Macrophages are extremely heterogenous with diverse phenotypes that are lineage- and tissue- specific, and highly influenced by the microenvironment. Preliminary data in this proposal demonstrate a tremendous increase in macrophage diversity after birth. Specialized, highly proliferative macrophages present before birth are replaced after birth by a complex and dynamic mixture of diverse macrophage subtypes exhibiting unique gene signatures, developmental gradients in gene expression, and specific locations within the lung suggesting distinct functions in tissue remodeling, angiogenesis, and immunity. Interestingly, a subset of embryonic macrophages was found to completely encircle small arterioles and express numerous genes that regulate lung branching, angiogenesis, and EC phenotype. After birth, these cells transitioned to an intermediate subset present only during the first few weeks of postnatal life that expressed additional tissue remodeling genes. Taken together, our data suggest the hypothesis that distinct macrophage populations support alveolarization by regulating pulmonary vascular development through the expression of factors that influence vascular growth and remodeling, which will be tested through three specific aims. Aim 1 will combine multiplexed in situ hybridization, lineage tracing, studies in primary EC and macrophages, and advanced imaging in transgenic and knock-out mice to define the role of specific macrophage subsets in modulating EC phenotype and regulating lung parenchymal and vascular growth. Aim 2 will utilize multiplexed in situ hybridization, conditional knock out mouse models, and ligand-receptor profiling of single cell datasets from pulmonary EC and macrophages to probe pathways mediating macrophage-EC communication. Finally, Aim 3 will determine if chronic hyperoxia alters diversity and phenotype of the lung macrophages during acute injury and after recovery, and specifically impairs developmental and homeostatic functions of lung macrophages. The successful completion of these studies will provide a multifaceted view of the diverse functions of lung macrophages during embryonic and early postnatal development at single cell resolution, and identify new pathways that could be directly translated into novel strategies to modulate vascular growth and regeneration in diseases marked by impaired pulmonary angiogenesis.