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A7641 - Conditional Deletion of Nedd4-2 in Lung Epithelial Cells Causes Diffuse Parenchymal Lung Disease in Adult Mice
Author Block: D. Leitz1, J. Duerr1, M. Szczygiel2, D. Dvornikov2, P. Konietzke3, H. Kawabe4, D. Rotin5, M. O. Wielpuetz3, M. F. Beers6, U. Klingmüller2, M. A. Mall1; 1Department of Translational Pulmonology, Translational Lung Research Center (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany, 2Division of Systems Biology of Signal Transduction, German Cancer Research Center (DKFZ), Translational Lung Research Center (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany, 3Department of Diagnostic and Interventional Radiology, Translational Lung Research Center (TLRC), German Center for Lung Research (DZL), Heidelberg, Germany, 4Department of Molecular Neurobiology, Max Planck Institute of Experimental Medicine, Göttingen, Germany, 5Hospital for Sick Children, University of Toronto, Toronto, ON, Canada, 6Pulmonary, Allergy, and Critical Care Division, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States.
RATIONALE: Diffuse Parenchymal Lung Diseases (DPLD) constitute a heterogeneous group of pulmonary diseases characterized by inflammation, fibrotic remodeling, and impaired gas exchange. Several mutations in different genes important for epithelial cell function have been reported to be associated with DPLD, but the pathogenesis remains poorly understood. METHODS: In this study, we used a mouse model enabling conditional deletion of Nedd4-2 in lung epithelial cells of adult mice. Nedd4-2 is a E3 ubiquitin ligase that was shown to be critical for regulation of the epithelial sodium channel ENaC, surfactant protein-C biosynthesis and TGFβ signaling which are known to be involved in pulmonary inflammatory diseases and pulmonary fibrosis. We intercrossed mice with Nedd4-2 flanked by lox-P sites (Nedd4-2fl/fl) with mice carrying the reverse tetracycline-dependent transactivator under control of the Club Cell Secretory Protein (CCSP)-Promoter (CCSP-rtTA2-M2) and mice expressing a PTet responsive Cre recombinase (LC-1). To study the impact of Nedd4-2 deletion in adult mice (hereafter referred to as Nedd4-2-/-), Cre activity was induced with doxycycline (dox) starting at the age of 4 weeks. To characterize disease development and progression we studied pulmonary morphology, collagen content, cytokine expressions of IL-13 and IL-1β, and lung mechanics at different time points of dox-induced deletion of Nedd4-2. Further, we measured oxygen saturation and performed micro-CT imaging in vivo to quantify fibrosis using a fibrosis score. RESULTS: Our results demonstrate that conditional deletion of Nedd4-2 in epithelial cells of the adult lung produces spontaneous chronic progressive interstitial lung disease with reduced oxygen saturation, continuous decline in lung compliance and increasing levels of IL-13, IL-1β, and TGFβ, and collagen content in the lung. Histology revealed patchy fibrotic lesions in the periphery of the lung with massive deposition of collagen, destruction of the lung parenchyma and signs of histological honeycombing. Micro-CT images of Nedd4-2-/- mice showed reticular opacities, ground glass opacities, traction bronchiectasis and honeycombing 4 months after deletion of Nedd4-2. CONCLUSION: These data suggest that this model may be useful to study biological pathways and define biomarkers in early pathogenesis and develop novel therapeutic strategies for patients with DPLD.