VEGF/KDR Signaling in Airway Epithelial Regeneration and Disease

摘要 粘液化生通常与多种肺部疾病的发病率和死亡率相关， 纤维化、COPD和哮喘。然而，导致粘液化生的细胞和分子机制尚不清楚。 这些疾病在很大程度上仍不为人所知。最近的谱系追踪数据表明，俱乐部细胞是起源细胞 用于粘膜上皮化生。然而，俱乐部细胞是一个异质群体，它仍然是未知的 哪种俱乐部细胞亚群有助于粘液化生。此外，导致 到粘液细胞分化在很大程度上是不确定的。我们的目标是解决这些悬而未决的问题， 提议我们的单细胞RNA测序分析确定了三个俱乐部细胞亚群，其中两个是 其特征在于VEGF受体2（也称为Flk 1或Kdr）的表达。值得注意的是，Kdr的缺失 导致出生后早期肺内气道上皮的粘膜化生。此外，委员会认为， 短暂增加的Kdr需要在气道再生过程中阻断粘膜化生， 萘挑战上皮Kdr的缺失或配体Vegfa的亚型突变导致大量的 表达Sox 9的粘液细胞，Sox 9已显示调节肠中的粘液细胞分化。 重要的是，粘膜化生也与Kdr表达减少伴随着Kdr表达增加有关。 卵清蛋白（OVA）诱导的哮喘肺中的S 0X 9蛋白水平。因此，我们假设VEGF/Kdr 信号传导是气道炎症中阻止俱乐部细胞亚群粘液分化的看门人 在哮喘期间，抑制Kdr通过Sox 9促进粘膜化生 发病机制我们制定了三个具体的目标来检验假设。目的1：检验假设， 上皮Kdr通过Erk信号传导阻断俱乐部细胞分化为粘液细胞。目的2：检验假设 Vegfa/Kdr信号阻断了俱乐部细胞亚群的粘液化生。目标3：检验假设 Vegfa/Kdr信号通过抑制Sox 9阻断粘膜化生。这些研究的结果将 提供了重要的见解，细胞和分子机制，管理正常粘液细胞分化 以及这个机制是如何出错导致粘膜化生的我们的研究还将提供潜在的 这种常见病理实体的治疗靶点。

ABSTRACT Mucous metaplasia is commonly associated with morbidity and mortality in multiple lung diseases including fibrosis, COPD and asthma. However, the cellular and molecular mechanisms leading to mucous metaplasia in these diseases remain largely unknown. Recent lineage tracing data suggest that club cells are the cell of origin for metaplastic mucous epithelium. However, the club cell is a heterogenous population, and it remains unknown which club cell subpopulation(s) contribute to mucous metaplasia. Moreover, the molecular mechanisms leading to mucous cell differentiation are largely undetermined. We aim to address these outstanding issues in this proposal. Our single-cell RNA sequencing analysis identified three club cell subpopulations, two of which are characterized by the expression of VEGF receptor 2 (also known as Flk1 or Kdr). Significantly, deletion of Kdr leads to mucous metaplasia of the intrapulmonary airway epithelium at the early postnatal stage. Furthermore, transiently increased Kdr is required for blocking mucous metaplasia during airway regeneration following naphthalene challenge. Loss of epithelial Kdr or a hypomorphic mutation for the ligand Vegfa leads to abundant mucous cells expressing Sox9 which has been shown to regulate mucous cell differentiation in the intestine. Importantly, mucous metaplasia is also associated with reduced Kdr expression accompanied by increased SOX9 protein levels in ovalbumin (OVA)-induced asthmatic lungs. We therefore hypothesize that Vegf/Kdr signaling is a gatekeeper blocking mucous differentiation of club cell subpopulations during airway regeneration, and that suppressed Kdr promotes mucous metaplasia via Sox9 during asthma pathogenesis. We formulate three specific aims to test the hypothesis. Aim 1: To test the hypothesis that epithelial Kdr blocks club cell differentiation into mucous cells via Erk signaling. Aim 2: To test the hypothesis that Vegfa/Kdr signaling blocks mucous metaplasia of club cell subpopulations. Aim 3: To test the hypothesis that Vegfa/Kdr signaling blocks mucous metaplasia via inhibition of Sox9. Findings from these studies will provide critical insights into the cellular and molecular mechanisms that govern normal mucous cell differentiation and how the mechanism goes awry, leading to mucous metaplasia. Our study will also provide potential therapeutic targets for this common pathological entity.