Improve Lung Regeneration Through Targeting Tuft Cells Following Viral Infection

摘要 季节性流感和当前的COVID-19大流行造成严重的健康和财政负担。严重病毒感染 导致急性肺损伤、炎症并导致组织重塑和纤维化。有趣的是， 基底细胞（也称为豆荚细胞）在急性感染和重塑阶段存在于外周肺中。初始 研究表明这些细胞能够产生I型和II型肺泡上皮细胞（AEC）。然而，尽管如此， 随后的谱系追踪研究揭示了荚状体细胞对肺泡再生的贡献即使有也是极小的。 此外，我们的初步数据表明，豆荚细胞产生杯状细胞，导致粘液化生伴随 通过化学感受簇细胞（也称为刷状细胞）的存在。值得注意的是，簇状细胞的基因切除促进了 豆荚细胞分化为AEC。我们进一步的分析显示，簇状细胞表达Notch配体Jag 2， 而豆荚细胞表达具有显著Notch激活的Notch受体。一致地，Notch抑制导致降低的 粘液化生和改善肺泡再生。因此，我们假设，簇细胞促进粘液 病毒感染后，通过旁分泌JAG 2/Notch激活，可导致豆荚细胞化生并阻碍肺泡再生。 设计了两个具体的目标来检验这一假设。目的1：阐明毛簇细胞在细胞内表达的分子机制， 促进病毒感染后的粘膜化生。目的2：通过诱导分化，促进豆荚细胞向AEC分化。 靶向簇细胞中的JAG 2。为此，我们将联合收割机结合新型COVID-19小鼠模型和豆荚细胞类器官 从COVID-19患者肺部建立，以测试JAG/Notch诱饵在促进肺泡再生方面的功效。 总之，这一提议不仅将阐明病毒感染后损害肺再生的疾病机制， 还为治疗流感和冠状病毒感染的肺部提供了新的治疗方法。

ABSTRACT Seasonal influenza and the current COVID-19 pandemic cause serious health and financial burdens. Severe viral infection leads to acute lung injury, inflammation and contributes to tissue remodeling and fibrosis. Intriguingly, clusters of ectopic basal cells (also known as pod cells) are present in the peripheral lungs during acute infection and remodeling phases. Initial studies indicated that these cells were able to generate type I and II alveolar epithelial cells (AECs). Nevertheless, subsequent lineage tracing studies revealed that pod cells had minimal if any contribution to alveolar regeneration. Moreover, our preliminary data suggest that pod cells give rise to goblet cells, resulting in mucous metaplasia accompanied by the presence of chemosensory tuft cells (also known as brush cells). Significantly, genetic ablation of tuft cells promotes the differentiation of pod cells into AECs. Our further analyses revealed that tuft cells express the Notch ligand Jag2, whereas pod cells express Notch receptors with prominent Notch activation. Consistently, Notch inhibition led to reduced mucous metaplasia and improved alveolar regeneration. We therefore hypothesize that tuft cells promote mucous metaplasia of pod cells and impede alveolar regeneration via paracrine JAG2/Notch activation upon viral infection. Two specific aims were devised to test the hypothesis. Aim1: To address the molecular mechanisms by which tuft cells promote mucous metaplasia following viral infection. Aim2: To promote the differentiation of pod cells into AECs through targeting JAG2 in tuft cells. In this aim we will combine a novel COVID-19 mouse model and pod cell organoids established from COVID-19 patient lungs to test the efficacy of a JAG/Notch decoy in promoting alveolar regeneration. Together this proposal will not only elucidate the disease mechanisms impairing lung regeneration post viral infection, but also offer new therapeutic approaches to treat lungs infected by influenza and coronavirus.