First published February 5, 2019 - More info
Alveolar type 2 (AT2) cell endoplasmic reticulum (ER) stress is a prominent feature in adult and pediatric interstitial lung disease (ILD and ChILD), but in vivo models linking AT2 cell ER stress to ILD have been elusive. Based on a clinical ChILD case we identified a critical cysteine residue in the Surfactant Protein C gene (SFTPC) BRICHOS domain whose mutation induced ER stress in vitro. To model this in vivo, we generated a knock-in model expressing a cysteine-to-glycine substitution at codon 121 (C121G) in the Sftpc gene. SftpcC121G expression during fetal development resulted in a toxic gain of function resulting in fatal post-natal respiratory failure from disrupted lung morphogenesis. Induced SftpcC121G expression in adult mice resulted in an ER retained pro-protein causing AT2 cell ER stress. SftpcC121G AT2 cells were a source of cytokines expressed in concert with development of a polycellular alveolitis. These cytokines were subsequently found in a high-dimensional proteomic screen of bronchoalveolar lavage fluid from ChILD patients with the same class of SFTPC mutations. Following alveolitis resolution, SftpcC121G mice developed spontaneous pulmonary fibrosis and restrictive lung impairment. This model provides proof of concept linking AT2 cell ER stress to fibrotic lung disease coupled with translationally relevant biomarkers.