GLI1+ cells are a source of repair-supportive mesenchymal cells (RSMCs) during airway epithelial regeneration

Abstract

Repair-supportive mesenchymal cells (RSMCs) have been recently reported in the context of naphthalene (NA)-induced airway injury and regeneration. These cells transiently express smooth muscle actin (Acta2) and are enriched with platelet-derived growth factor receptor alpha (Pdgfra) and fibroblast growth factor 10 (Fgf10) expression. Genetic deletion of Ctnnb1 (gene coding for beta catenin) or Fgf10 in these cells using the Acta2-Cre-ERT2 driver line after injury (defined as NA-Tam condition; Tam refers to tamoxifen) led to impaired repair of the airway epithelium. In this study, we demonstrate that RSMCs are mostly captured using the Acta2-Cre-ERT2 driver when labeling occurs after (NA-Tam condition) rather than before injury (Tam-NA condition), and that their expansion occurs mostly between days 3 and 7 following NA treatment. Previous studies have shown that lineage-traced peribronchial GLI1+ cells are transiently amplified after NA injury. Here, we report that Gli1 expression is enriched in RSMCs. Using lineage tracing with Gli1Cre−ERT2 mice combined with genetic inactivation of Fgf10, we show that GLI1+ cells with Fgf10 deletion fail to amplify around the injured airways, thus resulting in impaired airway epithelial repair. Interestingly, Fgf10 expression is not upregulated in GLI1+ cells following NA treatment, suggesting that epithelial repair is mostly due to the increased number of Fgf10-expressing GLI1+ cells. Co-culture of SCGB1A1+ cells with GLI1+ cells isolated from non-injured or injured lungs showed that GLI1+ cells from these two conditions are similarly capable of supporting bronchiolar organoid (or bronchiolosphere) formation. Single-cell RNA sequencing on sorted lineage-labeled cells showed that the RSMC signature resembles that of alveolar fibroblasts. Altogether, our study provides strong evidence for the involvement of mesenchymal progenitors in airway epithelial regeneration and highlights the critical role played by Fgf10-expressing GLI1+ cells in this context.

GLI1+ Cells Contribute to Vascular Remodeling in Pulmonary Hypertension

“…Bulk RNA-seq data were deposited on Gene Expression Omnibus, accession number GSE253415. The accession number for the single-cell RNA-seq dataset from the hypoxia condition is GSE260788, while that for normoxia is GSE215094 (uninjured lung in the study by Chu et al 22 ).…”

“…21 We have also recently shown that GLI1+ cells contribute to airway regeneration and subepithelial remodeling. 22 In this study, we hypothesized that perivascular GLI1+ cells contribute to newly formed ACTA2+ cells in the pulmonary vasculature of mice exposed to hypoxia or cigarette smoke. We used genetic lineage tracing combined with state-of-the-art imaging and flow cytometry to quantify and analyze lineage-labeled and ACTA2+ cells during VR and reverse remodeling (RR).…”

Perinatal origins of bronchopulmonary dysplasia—deciphering normal and impaired lung development cell by cell

“…Recent studies have shown that L-MSCs may constitute a rather heterogenous population and their study might require more advanced methods, such as scRNA-seq or sc-proteomics [ 292 , 293 ]. Another recently emerging candidate resident MSC population are the Gli-1 + repair-supportive mesenchymal cells [ 298 , 299 ]. Progenitor properties of Gli-1 + cells were previously described in other organs, including bones [ 300 , 301 ], teeth [ 300 ], and liver [ 302 ].…”

“…Progenitor properties of Gli-1 + cells were previously described in other organs, including bones [ 300 , 301 ], teeth [ 300 ], and liver [ 302 ]. In the lung, Gli-1 + cells co-express Acta2 , Fgf10 and Pdgfra , thus resembling alveolar fibroblasts [ 225 , 298 ]. In mice Gli-1 + MSCs were shown to aid epithelial regeneration following naphthalene-induced airway injury [ 298 ], and were shown to be increased in bleomycin-induced lung fibrosis in mice [ 303 ].…”

“…In the lung, Gli-1 + cells co-express Acta2 , Fgf10 and Pdgfra , thus resembling alveolar fibroblasts [ 225 , 298 ]. In mice Gli-1 + MSCs were shown to aid epithelial regeneration following naphthalene-induced airway injury [ 298 ], and were shown to be increased in bleomycin-induced lung fibrosis in mice [ 303 ]. A more detailed characterization of all types of lung resident stem cell populations will clearly be of essence in understanding their role in normal and impaired lung development and regeneration.…”