FGF18 regulation of postnatal lung development

FGF 18对出生后肺发育的调节 总结： 肺泡形成是肺发育的最后阶段，其中肺的表面积通过 通过形成次级隔膜（隔膜脊）细分肺泡囊，然后变薄， 以产生有效的空气/血液气体交换器官。支气管肺发育不良（BPD）是一种 肺泡发育受损的早产的常见并发症。BPD经常导致慢性 呼吸道疾病然而，除了维生素A和支持性护理外，没有治疗方法可以促进肺泡 和血管发育，以改善BPD婴儿的预后。 人类和啮齿类动物的肺泡形成可分为两个阶段。在第一阶段，肺泡 肌成纤维细胞（AMF）和其它间充质和上皮细胞调节次级隔膜的形成。 在第二阶段，间隔壁经历一个成熟过程，包括变薄，通过损失， 间充质细胞和微脉管系统的重塑，以单层毛细血管网络并列， 肺泡1型（AT 1）细胞。成熟的肺泡壁确保成人肺中有效的空气/血液气体交换。 深入了解调节肺泡分隔和间隔壁成熟的机制将是 需要为患有BPD的早产儿开发治疗方法，并为成人开发潜在的治疗方法。 肺再生然而，关于间充质祖细胞的身份， AMF和其他间充质细胞类型的功能，以及产生AMF的机制， 在完成二次分隔时终止并清除肺部AMF。 成纤维细胞生长因子18（Fgf 18）在肺泡形成期间在AMF和AT 1细胞中以高水平表达。 我们发现新生儿肺中FGF 18的条件性失活导致肺泡形成受损。通过 通过对Fgf 18表达细胞的谱系追踪，我们发现AMF在第一阶段的免疫后从肺中清除。 肺泡形成，与肺泡壁变薄一致，但AT 1细胞保留。 在这个建议中，我们使用了一个独特的遗传工具的谱系追踪和基因失活，细胞 分选结合RNA深度测序，以及单细胞和单核RNA测序，以鉴定 间充质和上皮FGF 18对肺泡发生第一和第二阶段的相对贡献， 在肺泡发生期间对FGF 18的细胞反应，在肺泡形成中产生成纤维细胞亚型的祖细胞， 肺泡隔，以及从肺中特异性清除AMF的机制。拟议的实验将 还生成了在肺泡发生期间存在的间隔间充质细胞类型的基因表达图谱， 将成为研究界的资源。

Title: FGF18 regulation of postnatal lung development Summary: Alveologenesis is the final stage of lung development where the surface area of the lung is increased by subdividing alveolar saccules through the formation of secondary septae (septal ridges), followed by thinning of the septal walls to generate an efficient air/blood gas exchange organ. Bronchopulmonary dysplasia (BPD) is a common complication of preterm birth in which alveologenesis is impaired. BPD often results in chronic respiratory disease. However, besides Vitamin A and supportive care, no therapies exist to promote lung alveolar and vascular development to improve the outcomes of infants with BPD. Alveologenesis can be divided into two phases in humans and rodents. During the first phase, alveolar myofibroblasts (AMFs) and other mesenchymal and epithelial cells regulate the formation of secondary septae. During the second phase, the septal walls undergo a maturation process that involves thinning, through loss of mesenchymal cells and remodeling of the microvasculature, to a single layer capillary network juxtaposed with alveolar type 1 (AT1) cells. The mature alveolar wall ensures efficient air/blood gas exchange in the adult lung. An in-depth understanding the mechanisms that regulate alveolar septation and septal wall maturation will be required to develop therapies for premature infants with BPD and for developing potential therapies for adult lung regeneration. However, there are specific knowledge gaps about the identity of mesenchymal progenitors that give rise to AMFs, the functions of AMFs and other mesenchymal cell types, and the mechanisms that terminate and clear AMFs from the lung at the completion of secondary septation. Fibroblast Growth Factor 18 (Fgf18) is expressed at high levels in AMFs and AT1 cells during alveologenesis. We show that conditional inactivation of Fgf18 in the neonatal lung results in impaired alveologenesis. Through lineage tracing of Fgf18-expressing cells, we find that the AMFs are cleared from the lung after the first phase of alveologenesis, coinciding with alveolar wall thinning, but that AT1 cells are retained. In this proposal, we use a combination of unique genetic tools for lineage tracing and gene inactivation, cell sorting coupled with RNA deep sequencing, and single cell and single nuclei RNA sequencing, to identify the relative contribution of mesenchymal and epithelial FGF18 to the first and second phases of alveologenesis, the cellular response(s) to FGF18 during alveologenesis, the progenitors that give rise to fibroblasts sub-types in alveolar septae, and the mechanisms that specifically clear AMFs from the lung. The proposed experiments will also generate an atlas of gene expression for septal mesenchymal cell types present during alveologenesis that will serve as a resource for the research community.