Abstract

While antenatal glucocorticoids are widely used to enhance lung function in preterm infants, cellular and molecular mechanisms by which glucocorticoid receptor (GR) signaling influences lung maturation remain poorly understood. Deletion of the glucocorticoid receptor gene (Nr3c1) from fetal pulmonary mesenchymal cells phenocopied defects caused by global Nr3c1 deletion, while lung epithelial- or endothelial-specific Nr3c1 deletion did not alter lung function at birth. We integrated genome-wide gene expression profiling, ATAC-seq, and single cell RNA-seq data in mice in which GR was deleted or activated to identify the cellular and molecular mechanisms by which glucocorticoids control prenatal lung maturation. GR activated differentiation of a newly defined proliferative mesenchymal progenitor cell (PMP) into matrix fibroblasts (MFB), in part by directly activating extracellular matrix-associated target genes, including Fn1, Col16a4, and Eln and modulating VEGF, JAK-STAT and WNT signaling. Loss of mesenchymal GR signaling blocked PMP differentiation into mature MFB, which in turn caused proliferation of SOX9+ alveolar epithelial progenitor cells and inhibited differentiation of more mature AT2 and AT1 cells. GR signaling controls genes required for differentiation of a subset of proliferative mesenchymal progenitors into matrix fibroblasts in turn, regulating signals controlling AT2/AT1 progenitor cell proliferation and differentiation, identifying cells and processes by which glucocorticoid signaling regulates fetal lung function.

Data Availability

All sequencing data from the present study has been deposited to GEO (https://www.ncbi.nlm.nih.gov/geo/). R code used for data analysis is available at Github - Xu Lab.

• Whole lung microarray data from mesenchyme-specific GR deletion mice (Col1a2-Cre;Nr3c1fl/fl) at E16.5 & E18.5 - GSE30143
• RNA-seq of lung (Twist2Cre;Rosa26mT/mG mice treated with dexamethasone or saline) at E18.5; RNA-seq of CD106+ (CD45-/CD31-/CD309-/CD106+) and CD106- cells; ATAC-seq of CD106+ cells at E16.5 and E18.5; scRNA-seq of mouse lung (wild type embryos treated with Dex or saline in vivo and harvested at E18.5) – GSE136954