CGRP induction in cystic fibrosis airways alters the submucosal gland progenitor cell niche in mice
Weiliang Xie, … , Xiaoming Liu, John F. Engelhardt
Weiliang Xie, … , Xiaoming Liu, John F. Engelhardt
Published July 18, 2011
Citation Information: J Clin Invest. 2011;121(8):3144-3158. https://doi.org/10.1172/JCI41857.
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Research Article

CGRP induction in cystic fibrosis airways alters the submucosal gland progenitor cell niche in mice

Abstract

In cystic fibrosis (CF), a lack of functional CF transmembrane conductance regulator (CFTR) chloride channels causes defective secretion by submucosal glands (SMGs), leading to persistent bacterial infection that damages airways and necessitates tissue repair. SMGs are also important niches for slow-cycling progenitor cells (SCPCs) in the proximal airways, which may be involved in disease-related airway repair. Here, we report that calcitonin gene–related peptide (CGRP) activates CFTR-dependent SMG secretions and that this signaling pathway is hyperactivated in CF human, pig, ferret, and mouse SMGs. Since CGRP-expressing neuroendocrine cells reside in bronchiolar SCPC niches, we hypothesized that the glandular SCPC niche may be dysfunctional in CF. Consistent with this hypothesis, CFTR-deficient mice failed to maintain glandular SCPCs following airway injury. In wild-type mice, CGRP levels increased following airway injury and functioned as an injury-induced mitogen that stimulated SMG progenitor cell proliferation in vivo and altered the proliferative potential of airway progenitors in vitro. Components of the receptor for CGRP (RAMP1 and CLR) were expressed in a very small subset of SCPCs, suggesting that CGRP indirectly stimulates SCPC proliferation in a non-cell-autonomous manner. These findings demonstrate that CGRP-dependent pathways for CFTR activation are abnormally upregulated in CF SMGs and that this sustained mitogenic signal alters properties of the SMG progenitor cell niche in CF airways. This discovery may have important implications for injury/repair mechanisms in the CF airway.

Authors

Weiliang Xie, John T. Fisher, Thomas J. Lynch, Meihui Luo, Turan I.A. Evans, Traci L. Neff, Weihong Zhou, Yulong Zhang, Yi Ou, Nigel W. Bunnett, Andrew F. Russo, Michael J. Goodheart, Kalpaj R. Parekh, Xiaoming Liu, John F. Engelhardt

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Figure 6

LRCs in SMGs and the SAE have the capacity to reenter the cell cycle following a second injury.

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LRCs in SMGs and the SAE have the capacity to reenter the cell cycle fol...
(A–C) Mice were naphthalene injured and labeled with BrdU on days 1, 3, and 5 after injury. At 90 days after injury, mice were reinjured with naphthalene and euthanized 20 hours later. Tracheal sections were then stained for BrdU (red) and cyclin D1 (green). Photomicrographs depict double-positive cells (yellow arrowheads) in the SAE and/or SMGs of (A and B) Cftr+/– and (C and D) Cftr–/– mice. (E–I) Wild-type mice were injured with naphthalene and initially labeled with IdU on days 1, 3, and 5 after injury. Animals were subsequently reinjured again at 80 days and labeled with CldU on days 1, 3, and 5 following the second injury. Thirty-five days following the second injury, tracheal sections were costained for CldU, IdU, and/or K14. (E and F) Photomicrographs demonstrating all 3 channels for K14, CldU, and IdU (E is a collage). F is an enlargement of the boxed SMG region in E demonstrating one K14+CldU+IdU+ cell marked by a purple arrowhead. (G–I) Dual channel images of glandular regions demonstrating single- and double-labeled nuclei marked with colored arrows (IdU+, blue; CldU+, red; IdU+CldU+, purple). Photomicrographs show SMG regions with clearly visible singly labeled nuclei (H and I), demonstrating the specificity of the staining and clustering of double-positive nuclei (G). Results in all panels are representative of 3 independent mice. Scale bars: 25 μm (A–D, F–I), 100 μm (E).