Am. J. Respir. Cell Mol. Biol.,
Volume 24, Number 6, June, 2001 671-681
Clara Cell Secretory Protein-Expressing Cells of the Airway
Neuroepithelial Body Microenvironment Include a Label-Retaining Subset
and Are Critical for Epithelial Renewal after Progenitor Cell Depletion
Kyung U.
Hong,*
Susan D.
Reynolds,*
Adam
Giangreco,
Cheryl M.
Hurley,
and
Barry R.
Stripp
Department of Environmental Medicine, University of Rochester, Rochester, New York
Stem cells with potential to contribute to the re-establishment
of the normal bronchiolar epithelium have not been definitively demonstrated. We previously established that neuroepithelial bodies (NEBs) sequester regenerative cells that contribute to bronchiolar regeneration after selective chemical
depletion of Clara cells, a major progenitor cell population.
Two candidate stem cells were identified on the basis of proliferative potential after chemical ablation: a pollutant-resistant subpopulation of Clara cells that retain their expression
of Clara cell secretory protein (CCSP) (variant CCSP-expressing [CE] cells or vCE cells) and calcitonin gene-related peptide
(CGRP)-expressing pulmonary neuroendocrine cells (PNECs).
In the present study, two populations of label-retaining cells
were identified within the NEB: CGRP-expressing cells and a
subpopulation of CE cells. To investigate contributions made by CE and CGRP-expressing cells to epithelial renewal, CE cells were ablated through acute administration of ganciclovir to
transgenic mice expressing herpes simplex virus thymidine
kinase under the regulatory control of the mouse CCSP promoter. CGRP-immunoreactive PNECs proliferated after depletion of CE cells, yet were unable to repopulate CE cell-depleted
airways. These results support the notion that vCE cells represent either an airway stem cell or are critical for stem cell
maintenance, and suggest that PNECs are not sufficient for
epithelial renewal.
*
Equally contributing authors.
Abbreviations: acetylated tubulin, ACT; basement membrane, BM; bromodeoxyuridine, BrdU; Clara-cell secretory protein, CCSP; CCSP-HSVtk, CCtk; CCSP-expressing, CE; calcitonin gene-related peptide, CGRP;
cytochrome P450 2F2 isozyme, CYP2F2; 4,6-diamidino-2-phenylindole, DAPI; ganciclovir, GCV; herpes simplex virus thymidine kinase, HSVtk;
immunoreactive, IR; messenger RNA, mRNA; neuroepithelial body, NEB;
phosphate-buffered saline, PBS; pulmonary neuroendocrine cell, PNEC;
standard error of the mean, SEM; transit-amplifying, TA; thymine deoxyribose, TdR; variant CE, vCE.