Detection and quantification of epithelial progenitor cell populations in human healthy and IPF lungs

Abstract

BackgroundIn the human lung, epithelial progenitor cells in the airways give rise to the differentiated pseudostratified airway epithelium. In mice, emerging evidence confers a progenitor function to cytokeratin 5 (KRT5+) or cytokeratin 14 (KRT14+)-positive basal cells of the airway epithelium. Little is known, however, about the distribution of progenitor subpopulations in the human lung, particularly about aberrant epithelial differentiation in lung disease, such as idiopathic pulmonary fibrosis (IPF).MethodsHere, we used multi-color immunofluorescence analysis to detect and quantify the distribution of airway epithelial progenitor subpopulations in human lungs obtained from healthy donors or IPF patients.ResultsIn lungs from both, healthy donors and IPF patients, we detected KRT5+KRT14-, KRT5-KRT14+ and KRT5+KRT14+ populations in the proximal airways. KRT14+ cells, however, were absent in the distal airways of healthy lungs. In IPF, we detected a dramatic increase in the amount of KRT5+ cells and the emergence of a frequent KRT5+KRT14+ epithelial population, in particular in distal airways and alveolar regions. While the KRT14- progenitor population exhibited signs of proper epithelial differentiation, as evidenced by co-staining with pro-SPC, aquaporin 5, CC10, or MUC5B, the KRT14+ cell population did not co-stain with bronchial/alveolar differentiation markers in IPF.ConclusionsWe provide, for the first time, a quantitative profile of the distribution of epithelial progenitor populations in human lungs. We show compelling evidence for dysregulation and aberrant differentiation of these populations in IPF.

Emerging therapies for idiopathic pulmonary fibrosis, a progressive age-related disease

“…KRT5 + Δp63 + cells have persistent activation of the Notch signalling pathway and promote microhoneycombing rather than the regeneration of normal alveoli 60 . These data suggest that stressed AEC2s in the IPF lung are inefficient at regenerating the lung and that a second pool of progenitor cells mediates the repair response that favours honeycombing and fibrosis 35,61 .…”

“…KRT5 + Δp63 + cells have persistent activation of the Notch signalling pathway and promote microhoneycombing rather than the regeneration of normal alveoli 60 . These data suggest that stressed AEC2s in the IPF lung are inefficient at regenerating the lung and that a second pool of progenitor cells mediates the repair response that favours honeycombing and fibrosis 35,61 .Immunohistochemical evidence suggests that some epithelial cells are molecularly reprogrammed to undergo EMT 62,63 . However, the contribution of this EMT-like process to the fibrotic response remains unresolved.…”

Elastase-Induced Parenchymal Disruption and Airway Hyper Responsiveness in Mouse Precision Cut Lung Slices: Toward an Ex vivo COPD Model

“…To further investigate the parenchymal damage induced by elastase and H 2 O 2, markers of alveolar epithelial Type I and II cells were assessed: T1α and Aqp5 (specific for alveolar Type I cells), Con43 and Rage (both alveolar Type I cell associated), and Sftpc (specific for alveolar Type II cells; McElroy and Kasper, 2004; Smirnova et al, 2016). In our model, the structural damage caused by elastase was associated with a specific decrease in expression of alveolar type I and II markers.…”

“…COPD is characterized by a loss of alveolar epithelial type I and II cells and hence alveolar structure integrity (Barnes, 2016). To investigate the alveolar epithelial repair marker expression after elastase or H 2 O 2 treatment, several markers were chosen: T1α and Aqp5 (specific for alveolar Type I cells), Con43 and Rage (both alveolar Type I cell associated), and Sftpc (specific for alveolar Type II cells; McElroy and Kasper, 2004; Smirnova et al, 2016). Some of these markers such as Aqp5 and Sftpc are decreased in COPD, and this decrease is correlated with a lower lung function (Wang et al, 2007; Zhao et al, 2014).…”

Erratum: Emerging therapies for idiopathic pulmonary fibrosis, a progressive age-related disease

“…KRT5 + Δp63 + cells have persistent activation of the Notch signalling pathway and promote micro-honeycombing rather than the regeneration of normal alveoli 60 . These data suggest that stressed AEC2s in the IPF lung are inefficient at regenerating the lung and that a second pool of progenitor cells mediates the repair response that favours honeycombing and fibrosis 35,61 .…”