Sustained YAP/TAZ activation promotes aberrant alveolar epithelial cell differentiation and drives persistent fibrotic remodeling
Isabella P. Gaona, A. Scott McCall, Natalie M. Geis, Arlo C. Colvard, Gianluca T. DiGiovanni, Taylor P. Sherrill, Ujjal K. Singha, David S. Nichols, Ana P. Serezani, Holly E. David, Jean-Philippe Cartailler, Shristi Shrestha, Sergey S. Gutor, Timothy S. Blackwell, Jonathan A. Kropski, Jason J. Gokey
Isabella P. Gaona, A. Scott McCall, Natalie M. Geis, Arlo C. Colvard, Gianluca T. DiGiovanni, Taylor P. Sherrill, Ujjal K. Singha, David S. Nichols, Ana P. Serezani, Holly E. David, Jean-Philippe Cartailler, Shristi Shrestha, Sergey S. Gutor, Timothy S. Blackwell, Jonathan A. Kropski, Jason J. Gokey
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Research Article Cell biology Pulmonology

Sustained YAP/TAZ activation promotes aberrant alveolar epithelial cell differentiation and drives persistent fibrotic remodeling

Abstract

YAP/TAZ signaling is required for initiation of lung alveolar repair, yet previous studies in idiopathic pulmonary fibrosis (IPF) predicted increased YAP/TAZ signaling in alveolar epithelial cells. We investigated whether persistent YAP/TAZ alveolar epithelial cell signaling contributes to failed epithelial repair and persistent fibrotic remodeling. In IPF lungs, we identified increased YAP+TAZ+ alveolar epithelial cells and increased transcriptional target expression. Pharmacological YAP/TAZ activation in human alveolar epithelial cell organoids and in murine AT2 cell organoids generated with genetic YAP/TAZ activation (YTactive) (via deletion of Hippo kinases Stk3 and Stk4) resulted in phenotype shifts into aberrant transitional and airway-like states. Bleomycin injury of YTactive mice resulted in persistent fibrotic remodeling at 28 and 56 days after bleomycin injury. Gene promoter activity associated with transitional cell markers (Krt19, Hopx, and Runx2) was increased in YTactive AT2 cells. Immunofluorescent staining showed a loss of AT2-associated Cebpa and increased Krt19 in YTactive lineage-traced AT2 cells 28 days after injury. Inhibition of YAP/TAZ using verteporfin resulted in improved lung repair in YTactive mouse lungs, including restored Cebpa and decreased Krt19+ transitional cells. These findings demonstrate that sustained YAP/TAZ activation drives abnormal alveolar repair and persistent fibrotic remodeling. Blocking aberrant persistent YAP/TAZ activity promotes adaptive repair and has potential as a therapeutic strategy for pulmonary fibrosis.

Authors

Isabella P. Gaona, A. Scott McCall, Natalie M. Geis, Arlo C. Colvard, Gianluca T. DiGiovanni, Taylor P. Sherrill, Ujjal K. Singha, David S. Nichols, Ana P. Serezani, Holly E. David, Jean-Philippe Cartailler, Shristi Shrestha, Sergey S. Gutor, Timothy S. Blackwell, Jonathan A. Kropski, Jason J. Gokey

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Figure 4

YTactive mice show increased and sustained fibrotic remodeling.

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YTactive mice show increased and sustained fibrotic remodeling. (A) Time...
(A) Timeline of mouse injury model with YAP/TAZ activated before bleomycin with lungs assessed at 14 and 28 days. (B) Masson’s trichrome staining of lung tissue sections from WT and YTactive mice at 14, 28, and 56 days after bleomycin or saline instillation. Scale bars: 100 μm. (C and D) Quantitative analysis of total collagen (C) and Ashcroft scoring of fibrosis (D) in WT and YTactive mice at 14 and 28 days after saline or bleomycin. Mice from 3 independent experiments were pooled in the following groups: WT saline (n = 10), YTactive saline (n = 8), day 14 WT bleomycin (n = 16), day 14 YTactive bleomycin (n = 13), day 28 WT bleomycin (n = 10), and day 28 YTactive (n = 16) bleomycin. (E) Timeline of mouse lung injury model with YAP/TAZ activated after bleomycin and collection at 28 and 56 days. (F and G) Quantitative analysis of total collagen (F) and Ashcroft scoring of fibrosis (G) in WT and YTactive mice at 28 and 56 days after saline or bleomycin. Mice across 3 independent experiments were grouped as WT saline (n = 9), YTactive saline (n = 8), day 28 WT bleomycin (n = 13), day 28 YTactive bleomycin (n = 14), day 56 WT bleomycin (n = 8), and day 56 YTactive bleomycin (n = 10). Ordinary 1-way ANOVA with Šidák’s multiple-comparison test with a single pooled variance was used to compare groups. (H) Immunofluorescence analysis of lineage-traced AT2 cells (green) expressing Hopx (white) and TAZ (red) at 28 days after injury. Red arrows indicate TAZ+ lineage-traced cells. White arrows indicate Hopx+TAZ+ lineage-traced cells. Scale bar: 50 μM. (I) Quantification of TAZ+ lineage-traced AT2 cells in WT and YTactive saline-treated mice (N = 3 mice each) and bleomycin-treated mice (N = 12 mice each) from 28 days after injury across both time courses.