The Fetal Lung Mesothelial Differentiation Program

描述（由申请人提供）：间皮衍生细胞在多大程度上有助于肺发育和产后修复是该领域的一个开放和基本问题。这项资助的目的是解决这一基本问题，并评估Wilm's肿瘤1转录因子（WT 1）在这些事件中的关键作用。使用携带具有敲入Cre重组酶和GFP基因的WT1等位基因的小鼠品系，我们产生了初步数据，导致将检验的3个假设：1）胎儿间皮细胞含有分化的间充质肺细胞的祖细胞2）WT 1控制关键基因的表达，例如控制间皮细胞迁移到胎儿肺中的刺猬（Hh）途径成分，和3）间皮衍生的细胞有助于出生后肺修复和再生长。总之，我们发现WT1在E11.5至E16期间选择性地在肺间皮中表达，并且在成人中检测不到。我们确定了一个类似的时间模式WT1表达在灵长类动物肺，这表明一个保守的mesothelium WT1程序在哺乳动物物种。谱系追踪显示，间皮来源的细胞产生大量支气管平滑肌细胞（BSM），沿着其他实质肺细胞，其身份将被确定（目的1）。我们观察到WT1表达与间皮细胞进入潜在的肺和活跃的Hh信号传导相一致。从机制上讲，我们发现WT1与间皮细胞中多个Hh通路基因的启动子结合，并且间皮Hh信号的选择性丢失显著减弱了与EMT基因表达减少相关的进入下层肺的能力。这些数据指出了WT1在胎儿间皮中的关键作用，控制诸如参与迁移和EMT的Hh信号传导的途径，这将被进一步探索（目的2）。有趣的是，初步数据表明，WT1在肺切除术后的肺再生过程中被重新激活，而WT1在炎症性肺损伤（如哮喘和纤维化）中没有被重新激活。这些研究结果表明，2模型如何间皮可能有助于肺重塑在出生后的生活。在模型1中，胎儿WT 1调节的间皮细胞程序被重新激活。在模型2中，发育中的胎儿间皮细胞产生的实质细胞有助于修复。将进一步检查这些模型在多大程度上参与出生后生命中的肺再生长和重塑（目的3）。 我们期望这些研究的完成将为今后在这方面的工作奠定坚实的基础。 肺生物学的新领域。

DESCRIPTION (provided by applicant): To what extent mesothelial-derived cells contribute to lung development and post-natal repair is an open and basic question for the field. The objectives of this grant are to address this fundamental issue and to assess the key role of the Wilm's tumor 1 transcription factor (WT1) in these events. Using mouse lines that carry WT1 alleles with a knock-in Cre recombinase and GFP genes, we generated preliminary data leading to 3 hypotheses that will be examined: 1) the fetal mesothelium contains progenitors for differentiated mesenchymal lung cells 2) WT1 controls the expression of key genes, such as hedgehog (Hh) pathway constituents that control mesothelial migration into the fetal lung, and 3) mesothelium-derived cells contribute to post-natal lung repair and re-growth. To summarize, we found that WT1 is selectively expressed in the lung mesothelium from E11.5 to E16 and is undetectable in the adult. We identified a similar temporal pattern of WT1 expression in the primate lung, suggesting a conserved mesothelial WT1 program across mammalian species. Lineage tracing showed that mesothelium-derived cells give rise to a substantial number of bronchial smooth muscle cells (BSM), along with other parenchymal lung cells whose identities will be established (Aim 1). We observed that WT1 expression coincides with mesothelial cell entry into the underlying lung and active Hh signaling. Mechanistically, we found that WT1 binds to the promoters of multiple Hh pathway genes in mesothelial cells, and that selective loss of mesothelial Hh signaling markedly attenuates entry into the underlying lung in association with diminished expression of EMT genes. These data point to a key role for WT1 in the fetal mesothelium, controlling pathways such as Hh signaling that are involved in migration and EMT, which will be further explored (Aim 2). Interestingly, preliminary data indicate that WT1 is reactivated during lung re-growth post-pneumonectomy whereas WT1 is not re-activated in inflammatory lung injuries, such as asthma and fibrosis. These findings suggest 2 models for how the mesothelium may contribute to lung remodeling in post-natal life. In model 1, the fetal WT1-regulated mesothelial program is re-activated. In model 2, parenchymal cells that arise from the fetal mesothelium in development contribute to repair. To what degree these models are involved in lung re- growth and remodeling in post-natal life will be further examined (Aim 3). We expect that completion of these studies will establish a firm foundation for future work in this new area of lung biology.