Conditional Clara cell ablation reveals a self-renewing progenitor function of pulmonary neuroendocrine cells

Abstract

The neuroepithelial body (NEB) is a highly dynamic structure that responds to chronic airway injury through hyperplasia of associated pulmonary neuroendocrine (PNE) cells. Although NEB dysplasia is correlated with preneoplastic conditions and PNE cells are thought to serve as a precursor for development of small cell lung carcinoma, mechanisms regulating expansion of the PNE cell population are not well understood. Based on studies performed in animal models, it has been suggested that NEB-associated progenitor cells that are phenotypically distinct from PNE cells contribute to PNE cell hyperplasia. We have previously used a Clara cell-specific toxicant, naphthalene, to induce airway injury in mice and have demonstrated that naphthalene-resistant Clara cells, characterized by their expression of Clara cell secretory protein (CCSP), and PNE cells contribute to airway repair and associated hyperplasia of NEBs. This study was conducted to define the contribution of NEB-associated CCSP-expressing progenitor cells to PNE cell hyperplasia after Clara cell ablation. Transgenic (CCtk) mice were generated in which herpes simplex virus thymidine kinase was expressed within all CCSP-expressing cells of the conducting airway epithelium through the use of transcriptional regulatory elements from the mouse CCSP promoter. Chronic administration of ganciclovir (GCV) to CCtk transgenic mice resulted in selective ablation of CCSP-expressing cells within conducting airways. Proliferation and hyperplasia of PNE cells occurred in the absence of detectable proliferation among any other residual airway epithelial cell populations. These results demonstrate that PNE cells function as a self-renewing progenitor population and that NEB-associated Clara cells are not necessary for PNE cell hyperplasia.

Basal Cells Are a Multipotent Progenitor Capable of Renewing the Bronchial Epithelium

“…19 Transgenic mice (n ϭ 4) were exposed to GCV delivered over a 24-hour period by miniosmotic pumps (ALZET, Palo Alto, CA) as described previously. 16 To continuously label proliferating cells following GCV treatments in CCtk mice, 14-day miniosmotic pumps delivering 0.5 l/hour of sterile 20 mg/ml bromodeoxyuridine (BrdU) in normal saline solution were implanted subcutaneously on recovery day 2.…”

“…14 -18 CGRP-expressing progenitor cells of the bronchiolar epithelium serve a selfrenewing function but lack the potential for multipotent differentiation. 16,19 In contrast, naphthalene-resistant CE cells are absolutely required for renewal of the bronchiolar epithelium. 14,16 Bronchial airways also harbor at least two distinct progenitor cell populations.…”

Perspectives of purinergic signaling in stem cell differentiation and tissue regeneration

“…They can be discriminated from Clara cells by their resistance to naphthalene and their close association with pulmonary neuroepithelial bodies (NEBs) [123,124]. ATP released from secretory vesicles of rodent NEBs [125] in response to depolarization in lung slices promotes paracrine effects on surrounding Clara-like cells by activation of P2Y2 receptors. Considering the stem cell-like characteristics of Clara-like cells, this purinergic signaling might be of great importance for airway epithelial repair after injury [123].…”

Hyperplasia of Alveolar Neuroendocrine Cells in Rat Lung Carcinogenesis by Silica with Selective Expression of Proadrenomedullin-Derived Peptides and Amidating Enzymes

“…Recent literature has paid attention to the question of whether differentiated NE cells are capable of proliferation, and whether hyperplastic reactions are due to neuroendocrine cell division or to the recruitment and differentiation of nearby epithelial stem cells (Reynolds et al, 2000a(Reynolds et al, , 2000b. In the present model, serial PCNA/endocrine marker immunohistochemical studies were performed to address this question.…”

“…Markers for proliferation have been found in differentiated endocrine cells (Montuenga et al, 1992b;Stevens et al, 1997), but the participation of non-NE progenitor cells in the process has also been shown (Reynolds et al, 2000a(Reynolds et al, , 2000b. Changes in the intracellular levels of peptides that render the cells more detectable by immunocytochemical techniques have also been proposed to explain the rapid increase of endocrine cell numbers found in acute conditions (Bousbaa et al, 1994).…”