Ciliated Cells of Pseudostratified Airway Epithelium Do Not Become Mucous Cells after Ovalbumin Challenge

Abstract

Mucous cell metaplasia is a hallmark of airway diseases, such as asthma and chronic obstructive pulmonary disease. The majority of human airway epithelium is pseudostratified, but the cell of origin of mucous cells has not been definitively established in this type of airway epithelium. There is evidence that ciliated, club cell (Clara), and basal cells can all give rise to mucus-producing cells in different contexts. Because pseudostratified airway epithelium contains distinct progenitor cells from simple columnar airway epithelium, the lineage relationships of progenitor cells to mucous cells may be different in these two epithelial types. We therefore performed lineage tracing of the ciliated cells of the murine basal cell-containing airway epithelium in conjunction with the ovalbumin (OVA)-induced murine model of allergic lung disease. We genetically labeled ciliated cells with enhanced Yellow Fluorescent Protein (eYFP) before the allergen challenge, and followed the fate of these cells to determine whether they gave rise to newly formed mucous cells. Although ciliated cells increased in number after the OVA challenge, the newly formed mucous cells were not labeled with the eYFP lineage tag. Even small numbers of labeled mucous cells could not be detected, implying that ciliated cells make virtually no contribution to the new goblet cell pool. This demonstrates that, after OVA challenge, new mucous cells do not originate from ciliated cells in a pseudostratified basal cell-containing airway epithelium.Keywords: mucous cell metaplasia; pseudostratified airway epithelium; ovalbumin; ciliated cell; goblet or mucous cell Mucous metaplasia is one of hallmarks of respiratory diseases, such as asthma (1) and chronic obstructive pulmonary disease (COPD) (2). It is characterized by an increased number of mucous cells (goblet cells) in the airway epithelium and, consequently, an excess of airway mucus that can contribute to airway obstruction, mucus plugging, chronic cough, decreased pulmonary function, increased risk of infection, and death (3-7). Mouse models of the acute allergic response to inhaled allergens, such as ovalbumin (OVA), are frequently used to study features of clinical asthma, including the appearance of goblet cells (8-10). Mechanistically, IL-13 is known to promote goblet cell metaplasia in murine models of allergic lung disease (11)(12)(13)(14), and increased levels of IL-13 are associated with asthma and COPD (3,15,16). Recently, SAM pointed domain containing ets transcription factor (SPDEF) and Forkhead box protein A3 (FOXA3) have been identified as transcription factors exclusively expressed in airway goblet cells, and the expression of both is increased after pulmonary allergen and IL-13 exposure (17,18).Prior animal studies of allergic lung disease largely focused on the murine small airway epithelium and, in aggregate, suggested that club cells (Clara) are the cells of origin of goblet cells after an allergen challenge. A decrease in the number of club cells accompanied by an increase in the...

Lung regeneration: mechanisms, applications and emerging stem cell populations

“…In the lungs of humans, as well as other mammals, this region of the airway also contains goblet cells, which are marked by expression of the transcription factor SPDEF and mucin-5ac (Muc5ac). Cell lineage–tracing studies in mice have shown that goblet cells, which arise in mice only after injury or in disease states, are derived from secretoglobin family 1a member 1–expressing (Scgb1a1 + ) secretory cells and not ciliated epithelial cells in the postnatal lung after injury 45 . Studies grafting basal and luminal cell populations into tracheas denuded of epithelium in mice followed by implantation of the reseeded tracheal xenografts into immunodeficient mice suggest that either basal or luminal cells can regenerate the tracheal epithe-lium 40,46,47 .…”

Injury Induces Direct Lineage Segregation of Functionally Distinct Airway Basal Stem/Progenitor Cell Subpopulations

“…Immunofluorescent detection has been described previously (Kim et al, 2012; Pardo-Saganta et al, 2013; Tata et al, 2013a). Briefly, the detection of Notch2 intracellular domain and of c-myb required signal amplification.…”

“…Mouse tracheal basal cells were obtained and cultured as previously described (Pardo-Saganta et al 2013; Tata et al 2013a; Zhao et al 2014). Lentiviral vectors expressing murine N2ICD were generated from 3XFlagNICD2 plasmid (Addgene, 20184).…”

Early life allergen‐induced mucus overproduction requires augmented neural stimulation of pulmonary neuroendocrine cell secretion

“…However, unlike human airways, mouse airways have few mucin‐producing cells under normal conditions. Allergen exposure induces mucus overproduction by up‐regulating mucin expression in secretory cells (2, 3). While the origin of cells that produce mucin differs between humans and mice, mechanisms underlying mucus overproduction in allergic inflammation are evolutionally conserved.…”