Title: Expression of mutant Sftpc in murine alveolar epithelia drives spontaneous lung fibrosis.

Authors: Nureki, Shin-Ichi; Tomer, Yaniv; Venosa, Alessandro; Katzen, Jeremy; Russo, Scott J; Jamil, Sarita; Barrett, Matthew; Nguyen, Vivian; Kopp, Meghan; Mulugeta, Surafel; Beers, Michael F

Published In J Clin Invest, (2018 Aug 31)

Abstract: Epithelial cell dysfunction is postulated as an important component in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Mutations in the surfactant protein C (SP-C) gene (SFTPC), an alveolar type II (AT2) cell-restricted protein, have been found in sporadic and familial IPF. To causally link these events, we developed a knockin mouse model capable of regulated expression of an IPF-associated isoleucine-to-threonine substitution at codon 73 (I73T) in Sftpc (SP-CI73T). Tamoxifen-treated SP-CI73T cohorts developed rapid increases in SftpcI73T mRNA and misprocessed proSP-CI73T protein accompanied by increased early mortality (days 7-14). This acute phase was marked by diffuse parenchymal lung injury, tissue infiltration by monocytes, polycellular alveolitis, and elevations in bronchoalveolar lavage and AT2 mRNA content of select inflammatory cytokines. Resolution of alveolitis (2-4 weeks), commensurate with a rise in TGF-β1, was followed by aberrant remodeling marked by collagen deposition, AT2 cell hyperplasia, α-smooth muscle actin-positive (α-SMA-positive) cells, and restrictive lung physiology. The translational relevance of the model was supported by detection of multiple IPF biomarkers previously reported in human cohorts. These data provide proof of principle that mutant SP-C expression in vivo causes spontaneous lung fibrosis, strengthening the role of AT2 cell dysfunction as a key upstream driver of IPF pathogenesis.

PubMed ID: 29920187

MeSH Terms: Airway Remodeling; Alveolar Epithelial Cells/metabolism; Alveolar Epithelial Cells/pathology; Amino Acid Substitution; Animals; Disease Models, Animal; Gene Expression; Gene Knock-In Techniques; Humans; Idiopathic Pulmonary Fibrosis/etiology; Idiopathic Pulmonary Fibrosis/metabolism; Idiopathic Pulmonary Fibrosis/pathology; Intercellular Signaling Peptides and Proteins; Mice; Mice, Mutant Strains; Mice, Transgenic; Mutant Proteins/genetics*; Mutant Proteins/metabolism*; Peptides/genetics*; Peptides/metabolism*; Protein Processing, Post-Translational; Pulmonary Alveoli/metabolism*; Pulmonary Alveoli/pathology*; Pulmonary Surfactant-Associated Protein C; RNA, Messenger/genetics; RNA, Messenger/metabolism