TAZ is required for lung alveolar epithelial cell differentiation after injury
Tianhe Sun, Zhiyu Huang, Hua Zhang, Clara Posner, Guiquan Jia, Thirumalai R. Ramalingam, Min Xu, Hans Brightbill, Jackson G. Egen, Anwesha Dey, Joseph R. Arron
Tianhe Sun, Zhiyu Huang, Hua Zhang, Clara Posner, Guiquan Jia, Thirumalai R. Ramalingam, Min Xu, Hans Brightbill, Jackson G. Egen, Anwesha Dey, Joseph R. Arron
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Research Article Pulmonology Stem cells

TAZ is required for lung alveolar epithelial cell differentiation after injury

Abstract

The lung is a relatively quiescent organ during homeostasis but has a remarkable capacity for repair after injury. Alveolar epithelial type I cells (AEC1s) line airspaces and mediate gas exchange. After injury, they are regenerated by differentiation from their progenitors — alveolar epithelial type II cells (AEC2s) — which also secrete surfactant to maintain surface tension and alveolar patency. While recent studies showed that the maintenance of AEC2 stemness is Wnt dependent, the molecular mechanisms underlying AEC2-AEC1 differentiation in adult lung repair are still incompletely understood. Here, we show that WWTR1 (TAZ) plays a crucial role in AEC differentiation. Using an in vitro organoid culture system, we found that tankyrase inhibition can efficiently block AEC2-AEC1 differentiation, and this effect was due to the inhibition of TAZ. In a bleomycin-induced lung injury model, conditional deletion of TAZ in AEC2s dramatically reduced AEC1 regeneration during recovery, leading to exacerbated alveolar lesions and fibrosis. In patients with idiopathic pulmonary fibrosis (IPF), decreased blood levels of the receptor for advanced glycation end products (RAGE), a biomarker of AEC1 health, were associated with more rapid disease progression. Our findings implicate TAZ as a critical factor involved in AEC2-to-AEC1 differentiation, and hence the maintenance of alveolar integrity after injury.

Authors

Tianhe Sun, Zhiyu Huang, Hua Zhang, Clara Posner, Guiquan Jia, Thirumalai R. Ramalingam, Min Xu, Hans Brightbill, Jackson G. Egen, Anwesha Dey, Joseph R. Arron

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Figure 1

IWR-1 inhibits AEC2-to-AEC1 differentiation in vitro.

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IWR-1 inhibits AEC2-to-AEC1 differentiation in vitro. TdTomato+ lineage-...
TdTomato+ lineage-labeled AEC2s were sorted from SPC-CreERT2; Rosa-lsl-tdTomato mouse lungs after tamoxifen administration. (A) 3D alveolar spheroid culture schematic: AEC2s were cultured in Matrigel with NHLF for 2 weeks or until alveolospheres developed. (B–G) Cells were treated with either control (DMSO) (B–D) or IWR-1 (E–G) throughout culture. Merged bright-field (BF) and fluorescence (FL) full-plate images (B and E) and FL close-ups (C and F) show the overall difference in shapes of the cultured spheroids under these 2 conditions. (D and G) Representative high-power BF images emphasize the distinct smooth surface of spheroids cultured with IWR-1 as compared to controls. (H and I) Whole spheroids were immunostained for AEC2 (SPC), AEC1 (HOPX), and Nuclei (Hoechst). Single focal planes of Z-stack images are shown. Full Z-stack images are available as Supplemental Videos 1 (control) and 2 (IWR-1). (J) Gene expression ratios (mean ± SD, 3 biological replicates) between Spc and Hopx, Aqp5, and Pdpn were used to quantify the AEC2 versus AEC1 composition of each well. No signals were detected with NHLF alone with these mouse qPCR probes. *P < 0.05; ***P < 0.001 (unpaired 2-tailed Student’s t tests). (K) Sorted AEC2s from C57B6 mice were cultured directly on cell culture–treated slides without (control) or with IWR-1 for 5 days in the presence of 10% serum. Cells were immunostained for AQP5 and nuclei were counterstained with Hoechst. Scale bars: 1 mm (B and E); 300 μm (C and F); 30 μm (D and G–I); 100 μm (K).