IGF1R controls mechanosignaling in myofibroblasts required for pulmonary alveologenesis.

Hua He,John Snowball,Jeffrey A Whitsett,Fei Sun,Cheng-Lun Na

doi:10.1172/jci.insight.144863

Abstract

Ventilation throughout life is dependent on the formation of pulmonary alveoli, which create an extensive surface area in which the close apposition of respiratory epithelium and endothelial cells of the pulmonary microvascular enables efficient gas exchange. Morphogenesis of the alveoli initiates at late gestation in humans and the early postnatal period in the mouse. Alveolar septation is directed by complex signaling interactions among multiple cell types. Here, we demonstrate that IGF1 receptor gene (Igf1r) expression by a subset of pulmonary fibroblasts is required for normal alveologenesis in mice. Postnatal deletion of Igf1r caused alveolar simplification, disrupting alveolar elastin networks and extracellular matrix without altering myofibroblast differentiation or proliferation. Moreover, loss of Igf1r impaired contractile properties of lung myofibroblasts and inhibited myosin light chain (MLC) phosphorylation and mechanotransductive nuclear YAP activity. Activation of p-AKT, p-MLC, and nuclear YAP in myofibroblasts was dependent on Igf1r. Pharmacologic activation of AKT enhanced MLC phosphorylation, increased YAP activation, and ameliorated alveolar simplification in vivo. IGF1R controls mechanosignaling in myofibroblasts required for lung alveologenesis.

Highlights

Formation of the mammalian lung requires precisely orchestrated interactions among a diversity of endothelial, mesenchymal, and epithelial cells regulated by autocrine and paracrine signaling that controls cell proliferation, migration, and production of the extracellular matrix (ECM)
Single-cell RNA sequencing data available on the Lung Gene Expression Analysis (LGEA) website demonstrated that IGF1 receptor gene (Igf1r) coexpressed with Gli1 and Pdgfra in a subset of lung fibroblasts on P1 [24] (Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/ jci.insight.144863DS1)
To assess whether IGF1R signaling was required for PDGFRα+ myofibroblast differentiation and proliferation, we introduced a Rosa26-eGFP allele into the mutant mice and isolated targeted cells based on GFP expression for RNA-Seq using FACS

Summary

Introduction

Formation of the mammalian lung requires precisely orchestrated interactions among a diversity of endothelial, mesenchymal, and epithelial cells regulated by autocrine and paracrine signaling that controls cell proliferation, migration, and production of the extracellular matrix (ECM). Alveologenesis the final phase of lung morphogenesis; in this phase an extensive surface area is created in which endothelial and epithelial cells come into close apposition, which is necessary for efficient gas exchange after birth. Extensive tissue remodeling occurs in late gestation during the saccular period of lung development, creating the dilated saccules needed for ventilation after birth [3]. Bulk generation of alveoli depends on a process termed “secondary septation,” in which subsets of fibroblasts extend to form alveolar ridges and produce elastin, ECM, and the signaling molecules that regulate mechanical forces guiding alveolar formation [6,7,8]. A subset of mesenchymal cells, PDGFRα+ fibroblasts, plays a critical role in the deposition of elastin and the diverse components of the ECM produced during alveologenesis. The role of myofibroblast contraction in the process is supported by recent observations that the inactivation of myosin light chain kinase gene (Mlck) inhibited alveologenesis [14]

Methods

Results

Conclusion