Division of Pulmonary, Critical Care and Sleep Medicine and.
Department of Pathology.
Am J Respir Cell Mol Biol. 2023 May;68(5):523-536. doi: 10.1165/rcmb.2022-0269OC.
Normal lung development critically depends on HH (Hedgehog) and PDGF (platelet-derived growth factor) signaling, which coordinate mesenchymal differentiation and proliferation. PDGF signaling is required for postnatal alveolar septum formation by myofibroblasts. Recently, we demonstrated a requirement for HH in postnatal lung development involving alveolar myofibroblast differentiation. Given shared features of HH signaling and PDGF signaling and their impact on this key cell type, we sought to clarify their relationship during murine postnatal lung development. Timed experiments revealed that HH inhibition phenocopies the key lung myofibroblast phenotypes of (platelet-derived growth factor subunit A) and (platelet-derived growth factor receptor alpha) knockouts during secondary alveolar septation. Using a dual signaling reporter, , we show that HH and PDGF pathway intermediates are concurrently expressed during alveolar septal myofibroblast accumulation, suggesting pathway convergence in the generation of lung myofibroblasts. Consistent with this hypothesis, HH inhibition reduces expression and diminishes the number of Pdgfra-positive and -lineage cells in postnatal lungs. Bulk RNA sequencing data of Pdgfra-expressing cells from Postnatal Day 8 (P8) lungs show that HH inhibition alters the expression not only of well-established HH targets but also of several putative PDGF target genes. This, together with the presence of Gli-binding sites in PDGF target genes, suggests HH input into PDGF signaling. We identified these HH/PDGF targets in several postnatal lung mesenchymal cell populations, including myofibroblasts, using single-cell transcriptomic analysis. Collectively, our data indicate that HH signaling and PDGF signaling intersect to support myofibroblast/fibroblast function during secondary alveolar septum formation. Moreover, they provide a molecular foundation relevant to perinatal lung diseases associated with impaired alveolarization.
正常的肺发育严重依赖于 HH（Hedgehog）和 PDGF（血小板衍生生长因子）信号，这些信号协调间充质分化和增殖。PDGF 信号对于出生后肺泡间隔形成的肌成纤维细胞是必需的。最近，我们证明了 HH 在涉及出生后肺发育的肺泡肌成纤维细胞分化中的必要性。鉴于 HH 信号和 PDGF 信号的共享特征及其对这种关键细胞类型的影响，我们试图在小鼠出生后肺发育过程中阐明它们之间的关系。定时实验表明，HH 抑制类似于 PDGF 亚单位 A 和 PDGF 受体 alpha 敲除的关键肺肌成纤维细胞表型在次级肺泡间隔形成过程中。使用双信号报告基因，我们表明 HH 和 PDGF 通路中间产物在肺泡间隔肌成纤维细胞积累过程中同时表达，表明在肺肌成纤维细胞生成中通路融合。这一假设与 HH 抑制降低 表达并减少出生后肺中 Pdgfra 阳性和谱系细胞的数量一致。来自出生后第 8 天（P8）肺的 Pdgfra 表达细胞的批量 RNA 测序数据表明，HH 抑制不仅改变了众所周知的 HH 靶基因的表达，还改变了几个假定的 PDGF 靶基因的表达。这与 PDGF 靶基因中存在 Gli 结合位点一起表明 HH 输入到 PDGF 信号中。我们使用单细胞转录组分析在几种出生后肺间充质细胞群体中鉴定了这些 HH/PDGF 靶基因，包括肌成纤维细胞。总的来说，我们的数据表明 HH 信号和 PDGF 信号相交以支持次级肺泡间隔形成期间肌成纤维细胞/成纤维细胞的功能。此外，它们为与肺泡化受损相关的围产期肺部疾病提供了相关的分子基础。
