Vascular development during lung organogenesis

项目摘要/摘要 肺血管网络和相关的肺循环对心血管和呼吸系统都是必不可少的。 功能。肺循环发育异常可导致多个新生儿和 儿科心肺疾病。然而，肺血管系统的确切发育过程 而发行量仍然极具争议性。早期使用血管铸型和电子显微镜的研究 提示近端血管生成和外周血管生成同时独立地发生在 胚胎早期的小鼠肺，后来通过连接这两者来建立肺循环 结构。但其他工作使用的是人类胚胎肺或特定于内皮细胞的连续3-D重建 报告老鼠认为，肺循环要么是通过血管生成过程，要么是通过 血管生成是唯一的。限制这些研究的一个主要障碍是分别缺乏遗传工具 追踪不同来源的肺血管细胞。我们已经培育出一种独特的转基因小鼠品系， 其中胚胎肺间充质细胞可以从肺的开始被特异性地标记 器官发生。利用这个系统，我们的初步研究表明，肺间充质来源的血管 内皮细胞(血管生成)和支持细胞可以区别于那些来自前 存在肺外来源的内皮细胞(血管生成)，以及肺间充质来源的 早期胚胎小鼠内皮细胞可结合成原存在的肺外血管 肺，然后成为胎儿近端和远端血管生长的主要来源 妊娠中期的肺。因此，我们假设肺外新生血管最初作为干， 并触发邻近肺间充质祖细胞分化为血管内皮细胞和支持细胞 细胞，这些细胞又结合成预先存在的血管，并成为后续血管的主要来源 肺循环网络发育。提出了两个具体的目标来确定(1) 肺血管内皮细胞和支持细胞，(2)肺循环的动态过程 建制派。使用Tbx4肺增强子驱动的Tet-on可诱导Cre/荧光蛋白报告小鼠， 血管内皮细胞的起源(S)和动态生长(血管生成与血管生成)和 血管支持细胞将在体内确定。心内灌注荧光凝集素标记 肺内皮细胞的连接，也将定义肺循环的启动。因此，这个自我-- 包含的小项目将揭示一个新的概念，即胚胎肺间充质祖细胞有助于 通过血管生成和/或血管生成形成肺血管网络。所获得的数据将 极大地提高了我们对肺器官发生和相关疾病的认识。

Project Summary/Abstract Lung vascular network and related pulmonary circulation are essential for both cardiovascular and respiratory functions. Developmental abnormalities of the pulmonary circulation contribute to several neonatal and pediatric cardiopulmonary diseases. However, the exact developmental processes of pulmonary vasculature and circulation remain highly controversial. Earlier study using vascular casting and electron microscopy suggests that simultaneous and independent proximal angiogenesis and peripheral vasculogenesis occur in early embryonic mouse lung, and pulmonary circulation is established later on by connecting these two structures. But other works using serial 3-D reconstruction of human embryonic lung or endothelium-specific reporter mice suggest that the pulmonary circulation arises by either the process of vasculogenesis or angiogenesis exclusively. One major obstacle to limit these studies is lack of genetic tools for respectively tracking the pulmonary vascular cells of different origins. We have generated a unique transgenic mouse line, in which embryonic lung mesenchymal cells can be specifically marked from the beginning of lung organogenesis. Using this system, our preliminary studies suggest that lung mesenchyme-derived vascular endothelial cells (vasculogenesis) and supporting cells can be distinguished from those derived from pre- existing endothelial cells of extrapulmonary origin (angiogenesis), and that lung mesenchyme-derived endothelial cells can coalesce into pre-existing vessels of extrapulmonary origin in early embryonic mouse lung, and then become the major source of the growing vasculature in both proximal and distal parts of fetal lung at mid-gestation. Thus, we hypothesize that extrapulmonary angiogenic vessels initially serve as a stem, and trigger nearby lung mesenchymal progenitor cell differentiation into vascular endothelial and supporting cells, which in turn coalesce into the pre-existing vessels, and become the major source for subsequent pulmonary circulation network development. Two specific aims are proposed to determine (1) the origins of pulmonary vascular endothelial and supporting cells, (2) the dynamic processes of pulmonary circulation establishment. Using the Tbx4 lung enhancer-driven Tet-On inducible Cre/fluorescence protein reporter mice, the origin(s) and the dynamic growth of vascular endothelial cells (angiogenesis vs. vasculogenesis) and vascular supporting cells will be determined in vivo. By intra-cardiac perfusion of fluorescence-lectin to label the connected lung endothelial cells, the initiation of pulmonary circulation will also be defined. Thus, this self- contained small project will reveal a new concept that embryonic lung mesenchymal progenitor cells contribute to pulmonary vascular network formation via angiogenesis and/or vasculogenesis. The obtained data will significantly advance our knowledge in lung organogenesis and related diseases.