Mechanisms controlling early human lung development

摘要 虽然许多支配小鼠肺分支的分子通路已经被定义，但很少有 已知人类早期的肺分支。我们的初步数据显示，分子和细胞 人胎肺分支的驱动机制与小鼠不同。肺分支 形态发生依赖于几个细胞和分子事件，包括细胞迁移、增殖、近端- 远端纹饰和上皮-间充质串音。小鼠肺中的近-远端图案是 以Sox2和Sox9在近端和远端隔室的独占表达为界 分别表达，并受成纤维细胞生长因子信号调节。假腺体形成过程中人肺的仔细分析 分期显示在远端上皮细胞中存在SOX2+/SOX9+双祖细胞群 花蕾，这是分枝所必需的。我们的初步数据显示，FGF10不会在 人胎肺，与小鼠肺不同。相反，我们证明了FGF18诱导了 人肺外植体以及随之而来的FGF18和平滑肌细胞(SMC)的减少 与分支功能受损有关。同时，我们观察到SMC延伸到 人类发育中的肺，似乎安排在新的上皮芽出现之前。基于这些 观察到，我们假设FGF18而不是FGF10在驱动人类肺的过程中起重要作用 通过协调上皮/间充质信号分支导致SMC分化和 迁移，进而收缩以机械方式引导早期人类肺的分支形态发生 发展。在第一个目标中，我们将定义协调上皮/间充质FGF18的作用 促进人类早期胎肺发育的信号转导。在这个目标中，我们将使用互补增益和 功能丧失途径确定FGF18在人胎肺分支中的作用 外植体，B)确定FGF18是否直接作用于上皮细胞以促进分支和维持 和C)确定FGF18信号对间充质祖细胞的影响 SMC的增殖、迁移和分化。在第二个目标中，我们将确定动态和 人胎肺SMC引导上皮分支的力学功能。在这个目标中，我们将A) 实时检测人SMC的分化和动态运动如何驱动上皮分支 B)确定SMC收缩能力对人肺分支的影响，使用 F-肌动蛋白聚合和肌球蛋白激活的抑制物，以及C)决定上皮-SMC 人类肺的适当分支所需的相互作用。先天性小肺(CSL)，也称为 作为肺发育不良，是一种常见的新生儿肺部疾病，影响大约是由 不同的侮辱方式影响着不同的发育机制。了解潜在的机制 早期的人类肺发育将改变我们对人类肺发育的概念，从而可能允许 发现可能的治疗途径，以恢复或促进新生儿的肺发育 中超。

Summary While many of the molecular pathways that govern mouse lung branching have been defined, little is known about early human lung branching. Our preliminary data show that the molecular and cellular mechanisms driving branching in the human fetal lung are different from those in mouse. Lung branching morphogenesis relies on several cellular and molecular events including cell migration, proliferation, proximal- distal patterning and epithelial-mesenchymal crosstalk. Proximal-distal patterning in the mouse lung is demarcated by the exclusive expression of Sox2 and Sox9 in the proximal and distal compartments respectively, and regulated by FGF signaling. Careful analyses of the human lung during the pseudoglandular stage revealed the presence of a double SOX2+/SOX9+ progenitor cell population in the distal epithelial buds, that is required for branching. Our preliminary data showed that FGF10 does not induce branching in the human fetal lung, unlike in mouse lung. In contrast, we showed that FGF18 induces branching in human lung explants, and a concomitant decrease of FGF18 and smooth muscle cells (SMCs), is associated with impaired branching. Meanwhile, we observed that SMCs extend to the periphery of the human developing lung, and seem to arrange prior to the emergence of new epithelial buds. Based on these observations, we hypothesize that FGF18, but not FGF10, plays an important role in driving human lung branching through coordinate epithelial/mesenchymal signals leading to SMC differentiation and migration, that in turn contract to mechanically guide branching morphogenesis in early human lung development. In the first aim, we will define the role of coordinate epithelial/mesenchymal FGF18 signaling in promoting early human fetal lung development. In this aim we will use complementary gain and loss of function approaches to A) determine the effect of FGF18 in the branching of human fetal lung explants, B) define whether FGF18 acts directly on the epithelium to promote branching and maintenance of SOX2/SOX9 progenitors and C) identify the effect of FGF18 signaling on mesenchymal progenitors and SMC proliferation, migration and differentiation. In the second aim, we will determine the dynamic and mechanical functions of SMCs in directing epithelial branching in human fetal lung. In this aim, we will A) determine in real time how differentiation and dynamic movement of SMCs drive epithelial branching in human lung explants in vitro, B) determine the effect of SMC contractility on human lung branching, using inhibitors of F-actin polymerization and myosin activation, and C) determine the epithelial-SMC interactions required for proper branching of the human lung. Congenital small lung (CSL), also known as pulmonary hypoplasia, is a common neonatal lung condition affecting approximately that may result from different insults affecting different developmental mechanisms. Understanding the mechanisms underlying early human lung development will transform our concepts of human lung development, and thus may allow for the discovery of possible therapeutic avenues to restore or enhance lung development for neonates with CSL.