Surfactant dysfunction during overexpression of TGF-β1 precedes profibrotic lung remodeling in vivo.
Transforming growth factor-β1 (TGF-β1) is involved in regulation of cellular proliferation, differentiation, and fibrogenesis, inducing myofibroblast migration and increasing extracellular matrix synthesis. Here, TGF-β1 effects on pulmonary structure and function were analyzed. Adenovirus-mediated gene transfer of TGF-β1 in mice lungs was performed and evaluated by design-based stereology, invasive pulmonary function testing, and detailed analyses of the surfactant system 1 and 2 wk after gene transfer. After 1 wk decreased static compliance was linked with a dramatic alveolar derecruitment without edema formation or increase in the volume of septal wall tissue or collagen fibrils. Abnormally high surface tension correlated with downregulation of surfactant proteins B and C. TTF-1 expression was reduced, and, using PLA (proximity ligand assay) technology, we found Smad3 and TTF-1 forming complexes in vivo, which are normally translocated into the nucleus of the alveolar epithelial type II cells (AE2C) but in the presence of TGF-β1 remain in the cytoplasm. AE2C show altered morphology, resulting in loss of total apical surface area per lung and polarity. These changes of AE2C were progressive 2 wk after gene transfer and correlated with lung compliance. Although static lung compliance remained low, the volume of septal wall tissue and collagen fibrils increased 2 wk after gene transfer. In this animal model, the primary effect of TGF-β1 signaling in the lung is downregulation of surfactant proteins, high surface tension, alveolar derecruitment, and mechanical stress, which precede fibrotic tissue remodeling and progressive loss of AE2C polarity. Initial TTF-1 dysfunction is potentially linked to downregulation of surfactant proteins.
Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany;
Elena
E
Lopez-Rodriguez
Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany;
Caroline
C
Boden
Department of Biochemistry and Molecular Biology, Faculty of Biology, Universidad Complutense de Madrid, Madrid, Spain;
Mercedes
M
Echaide
Department of Biochemistry and Molecular Biology, Faculty of Biology, Universidad Complutense de Madrid, Madrid, Spain;
Jesus
J
Perez-Gil
Firestone Institute of Respiratory Health, McMaster University, Hamilton, Ontario, Canada;
Martin
M
Kolb
Firestone Institute of Respiratory Health, McMaster University, Hamilton, Ontario, Canada;
Jack
J
Gauldie
Department of Experimental Pneumology, Hannover Medical School, Hannover, Germany; Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover, Germany; and.
Ulrich A
UA
Maus
Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany; Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover, Germany; and REBIRTH Cluster of Excellence, Hannover, Germany.
Matthias
M
Ochs
Institute of Functional and Applied Anatomy, Hannover Medical School, Hannover, Germany; Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), Hannover, Germany; and knudsen.lars@mh-hannover.de.
Lars
L
Knudsen
D056151:Airway Remodeling; D056809:Alveolar Epithelial Cells / Q000378:metabolism; D000818:Animals; D016764:Cell Polarity; D004268:DNA-Binding Proteins / Q000378:metabolism; D015536:Down-Regulation; D005355:Fibrosis; D015870:Gene Expression; D008168:Lung / Q000378:metabolism / Q000473:pathology; D017563:Lung Diseases, Interstitial / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008810:Mice, Inbred C57BL; D011663:Pulmonary Surfactants / Q000378:metabolism; D015398:Signal Transduction; D051900:Smad3 Protein / Q000378:metabolism; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1 / Q000096:biosynthesis / Q000235:genetics*
D004268:DNA-Binding Proteins; D011663:Pulmonary Surfactants; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D014157:Transcription Factors; D053773:Transforming Growth Factor beta1; C504004:Ttf1 protein, mouse
AE2C polarity; TGF-β1; TTF-1; pulmonary fibrosis; surfactant