Yap/Taz regulate alveolar regeneration and resolution of lung inflammation
Ryan LaCanna, … , Marla R. Wolfson, Ying Tian
Ryan LaCanna, … , Marla R. Wolfson, Ying Tian
Published May 1, 2019; First published April 15, 2019
Citation Information: J Clin Invest. 2019;129(5):2107-2122. https://doi.org/10.1172/JCI125014.
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Categories: Research Article Pulmonology Stem cells

Yap/Taz regulate alveolar regeneration and resolution of lung inflammation

Abstract

Alveolar epithelium plays a pivotal role in protecting the lungs from inhaled infectious agents. Therefore, the regenerative capacity of the alveolar epithelium is critical for recovery from these insults in order to rebuild the epithelial barrier and restore pulmonary functions. Here, we show that sublethal infection of mice with Streptococcus pneumoniae, the most common pathogen of community-acquired pneumonia, led to exclusive damage in lung alveoli, followed by alveolar epithelial regeneration and resolution of lung inflammation. We show that surfactant protein C–expressing (SPC-expressing) alveolar epithelial type II cells (AECIIs) underwent proliferation and differentiation after infection, which contributed to the newly formed alveolar epithelium. This increase in AECII activities was correlated with increased nuclear expression of Yap and Taz, the mediators of the Hippo pathway. Mice that lacked Yap/Taz in AECIIs exhibited prolonged inflammatory responses in the lung and were delayed in alveolar epithelial regeneration during bacterial pneumonia. This impaired alveolar epithelial regeneration was paralleled by a failure to upregulate IκBa, the molecule that terminates NF-κB–mediated inflammatory responses. These results demonstrate that signals governing resolution of lung inflammation were altered in Yap/Taz mutant mice, which prevented the development of a proper regenerative niche, delaying repair and regeneration of alveolar epithelium during bacterial pneumonia.

Authors

Ryan LaCanna, Daniela Liccardo, Peggy Zhang, Lauren Tragesser, Yan Wang, Tongtong Cao, Harold A. Chapman, Edward E. Morrisey, Hao Shen, Walter J. Koch, Beata Kosmider, Marla R. Wolfson, Ying Tian

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Figure 2

Alveolar epithelial regeneration and Yap/Taz expression in mouse lungs during bacterial pneumonia.

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Alveolar epithelial regeneration and Yap/Taz expression in mouse lungs d...
(A) Schematic of experimental design (left) and confocal images of lung sections at 0 dpi and 4 dpi. AECIIs in DNA synthesis phase were detected using Click-iT EdU Alexa Fluor (green) and coimmunostaining with antibody against pro-SPC (SPC) (red). Cell nuclei were stained with DAPI (blue). (B) Quantification of EdU+SPC+ cells as percentage of total SPC+ cells analyzed (~2200 SPC+ cells per animal). (C) Confocal images of lung sections of SPC-CreERT2, Rosa26-mTmG mice at 0, 7, and 14 dpi. Mice were administrated with 3 doses of tamoxifen to label SPC+ AECIIs. Fourteen days after the last tamoxifen treatment, mice were infected with SpT4. AECII-to-AECI differentiation was visualized by coimmunostaining with antibodies against GFP (lineage-labeled AECIIs) and T1a (AECIs). Arrowheads point to regions double-positive for GFP and T1a. (D) Quantification of percentage of GFP+T1a+ area of total GFP+ area per field using ImageJ. (E) Flow cytometry analysis of dissociated lung cells showing the percentage of GFP+T1a+ cells of total T1a+ cells at indicated time points. (F) Confocal images of lung sections of SPC-CreERT2, Rosa26-mTmG mice. Immunostaining with antibodies against GFP (lineage-labeled AECIIs) and Yap and Taz. Cell nuclei were stained with DAPI (blue). (G) Western blot using lung tissue lysates at 0 dpi or purified AECIIs at 0 and 7 dpi, blotted with anti-YAP, anti-pYAP (Ser127), anti-Taz, anti-pTaz (S89), and anti–β-actin. Histograms showed average of total YAP or TAZ normalized to β-actin (loading control), together with average ratio of pYAP/YAP and pTAZ/TAZ. n ≥ 4 per group (B, D, E); n = 3 per group (G). *P < 0.05; **P < 0.01; ****P < 0.0001, 1-way ANOVA (B, D, E) and Student’s t test (G). Scale bars: 10 μm.