Mechanisms controlling early human lung development

总结 虽然许多控制小鼠肺分支的分子途径已经被确定，但很少有 关于早期人类肺部分支的研究我们的初步数据显示， 人胎肺中驱动分支的机制与小鼠中的不同。肺分支 形态发生依赖于几种细胞和分子事件，包括细胞迁移、增殖、近端- 远端图案化和上皮-间充质串扰。小鼠肺的近端-远端模式是 以近端和远端隔室中Sox 2和Sox 9的排他性表达为界限 并受FGF信号转导调节。在假腺期对人肺的仔细分析 阶段显示远端上皮中存在双SOX 2 +/SOX 9+祖细胞群 芽，这是需要分支。我们的初步数据表明，FGF 10不诱导细胞分支。 人类胎儿的肺，不像老鼠的肺。相反，我们发现FGF 18诱导细胞分支， 人肺外植体，以及伴随的FGF 18和平滑肌细胞（SMC）的减少， 与分支受损有关同时，我们观察到平滑肌细胞延伸到周围的 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 根据观察，我们假设FGF 18，而不是FGF 10，在驱动人肺 通过协调上皮/间充质信号分支，导致SMC分化， 迁移，进而收缩以机械地引导早期人肺中的分支形态发生 发展在第一个目标中，我们将确定协调上皮/间充质FGF 18的作用， 促进早期人胎肺发育的信号传导。在这个目标中，我们将使用互补增益， A）确定FGF 18在人胎儿肺分支中的作用 外植体，B）确定FGF 18是否直接作用于上皮以促进分支和维持 C）鉴定FGF 18信号传导对间充质祖细胞的作用， SMC增殖、迁移和分化。在第二个目标中，我们将确定动态和 SMC在人胎肺中指导上皮分支的机械功能。为此，我们将（A） 真实的确定SMC的分化和动态运动如何驱动人类上皮分支 体外肺外植体，B）测定SMC收缩性对人肺分支的影响，使用 F-肌动蛋白聚合和肌球蛋白活化的抑制剂，和C）确定上皮-SMC 这是人类肺部正确分支所需的相互作用。先天性小肺（CSL），也称为 肺发育不全，是一种常见的新生儿肺部疾病，大约影响，可能是由于 不同的损伤影响不同的发育机制。了解潜在的机制 早期人类肺部发育将改变我们对人类肺部发育的概念， 发现可能的治疗途径，以恢复或增强新生儿肺发育， CSL。

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.