Vascular development during lung organogenesis

项目总结/摘要 肺血管网和相关的肺循环对于心血管和呼吸系统都是必不可少的 功能协调发展的肺循环的发育异常导致几种新生儿和 小儿心肺疾病然而，肺血管的确切发育过程 和发行量仍然存在很大争议。使用血管铸型和电子显微镜的早期研究 表明，同时和独立的近端血管生成和外周血管发生， 早期胚胎小鼠的肺，肺循环建立后，通过连接这两个 结构.但是其他的工作使用人胚肺或内皮特异性的连续3D重建， 报告小鼠提示肺循环通过血管发生过程或 仅血管生成。限制这些研究的一个主要障碍是缺乏遗传工具， 追踪不同来源的肺血管细胞。我们已经培育出了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，肺间质来源的血管， 内皮细胞（血管发生）和支持细胞可以与那些来源于前 现有的肺外来源的内皮细胞（血管生成），以及肺间充质来源的 早期胚胎小鼠肺外血管内皮细胞可融合成血管 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，我们假设肺外血管生成血管最初是作为主干， 并触发附近的肺间充质祖细胞分化为血管内皮细胞和支持细胞， 细胞，这反过来又合并到预先存在的血管，并成为随后的主要来源， 肺循环网络发育。提出了两个具体目标，以确定（1）的起源 肺血管内皮细胞和支持细胞;（2）肺循环的动力学过程 建立。使用Tbx4肺增强子驱动的Tet-On诱导型Cre/荧光蛋白报告基因小鼠， 血管内皮细胞的起源和动态生长（血管生成与血管发生），以及 将在体内测定血管支持细胞。通过心内灌注荧光凝集素标记 连接的肺内皮细胞，肺循环的启动也将被定义。因此，这个自我- 包含的小项目将揭示一个新的概念，胚胎肺间充质祖细胞有助于 通过血管生成和/或血管发生的肺血管网形成。获得的数据将 大大提高了我们对肺器官发生和相关疾病认识。

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.