Expansion of hedgehog disrupts mesenchymal identity and induces emphysema phenotype
Chaoqun Wang, … , Harold A. Chapman, Tien Peng
Chaoqun Wang, … , Harold A. Chapman, Tien Peng
Published July 12, 2018
Citation Information: J Clin Invest. 2018;128(10):4343-4358. https://doi.org/10.1172/JCI99435.
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Research Article Development Pulmonology

Expansion of hedgehog disrupts mesenchymal identity and induces emphysema phenotype

Abstract

GWAS have repeatedly mapped susceptibility loci for emphysema to genes that modify hedgehog signaling, but the functional relevance of hedgehog signaling to this morbid disease remains unclear. In the current study, we identified a broad population of mesenchymal cells in the adult murine lung receptive to hedgehog signaling, characterized by higher activation of hedgehog surrounding the proximal airway relative to the distal alveoli. Single-cell RNA-sequencing showed that the hedgehog-receptive mesenchyme is composed of mostly fibroblasts with distinct proximal and distal subsets with discrete identities. Ectopic hedgehog activation in the distal fibroblasts promoted expression of proximal fibroblast markers and loss of distal alveoli and airspace enlargement of over 20% compared with controls. We found that hedgehog suppressed mesenchymal-derived mitogens enriched in distal fibroblasts that regulate alveolar stem cell regeneration and airspace size. Finally, single-cell analysis of the human lung mesenchyme showed that segregated proximal-distal identity with preferential hedgehog activation in the proximal fibroblasts was conserved between mice and humans. In conclusion, we showed that differential hedgehog activation segregates mesenchymal identities of distinct fibroblast subsets and that disruption of fibroblast identity can alter the alveolar stem cell niche, leading to emphysematous changes in the murine lung.

Authors

Chaoqun Wang, Nabora S. Reyes de Mochel, Stephanie A. Christenson, Monica Cassandras, Rebecca Moon, Alexis N. Brumwell, Lauren E. Byrnes, Alfred Li, Yasuyuki Yokosaki, Peiying Shan, Julie B. Sneddon, David Jablons, Patty J. Lee, Michael A. Matthay, Harold A. Chapman, Tien Peng

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Figure 5

Hh activation disrupts the alveolar niche through suppression of mesenchymal feedback to stem/progenitor cells.

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Hh activation disrupts the alveolar niche through suppression of mesench...
(A) Isolation of lung mesenchymal fibroblasts from UbccreERT2/+:R26RSmoM2/+ animals followed by induction of 4OHT-activated Gli1 expression while Hgf expression was concurrently downregulated. Data are represented as mean ± SEM, with n = 3 per group. (B) SFTPC+ distal alveolar stem/progenitor cells were cocultured with Hh-inducible (UbccreERT2/+:R26RSmoM2/+) mesenchyme. 4OHT induction significantly reduced the formation of alveolar organoids, which was partially rescued with the addition of recombinant HGF. Colony-forming efficiency was defined as follows: (no. of colonies/no. added progenitors) × 100. Data are represented as mean ± SD, with n = 3 per group. (C) Western blotting analysis of phosphorylated MET (p-MET), MET, and GAPDH in whole-lung lysate from Hh-expanded and control mice. Relative protein level of p-MET was calculated by p-MET/MET. Data are represented as mean ± SEM, with n ≥ 3 per group. (D) Inducible deletion of the HGF receptor, MET, from SFTPC+ alveolar stem/progenitor- induced airspace enlargement in the distal compartment of the lung. Data are represented as mean ± SEM, with n = 5 per group. Scale bars: 200 μm (B); 100 μm (D). Each dot represents individual biological replicate. Statistical analysis was done using 1-tailed Student’s t test (A, C, and D) and 1-way ANOVA with Fisher’s LSD test (B). *P < 0.05. Results were replicated (n ≥ 2 experiments).