Cigarette smoke and diesel particles repress functional responses in lung epithelial progenitors

Abstract

Background: COPD is characterized by irreversible airflow limitation. Though studies indicate causative roles of cigarette smoke/air pollution in provoking the development of COPD, the precise impact of these factors on lung progenitors is unclear. We hypothesized cigarette smoke and diesel particles might reduce the functionality of lung epithelial progenitors. Methods: Murine lung organoids were set up by co-culturing epithelial cells (EpCAM+/CD45-/CD31-) with CCL206 fibroblasts in Matrigel. Organoids were exposed to different concentrations of Cigarette Smoke Extract (CSE) or Diesel Exhaust Particles (DEP) throughout entire culture period. Results: The number of organoids observed on day 7 was significantly decreased by 5% CSE and by 200 μg/mL DEP, yet slightly increased by 50 and 100 μg/mL DEP. CSE had no effect on the number of airway type organoids by day 14, but they were significantly increased by 50 and 100 μg/mL DEP, and decreased by 200 μg/mL DEP. The number of alveolar type organoids was significantly decreased by both 5% CSE and by 200 μg/mL DEP. Immunofluorescence studies showed the number of acetylated-α tubulin+ and pro-SPC+ organoids were significantly decreased by 5% CSE and by 200 μg/mL DEP respectively. The size of airway type organoids was significantly smaller in response to 5% CSE. Both 5% CSE and 200 μg/mL DEP significantly reduced the size of alveolar type organoids by day 14. Conclusion: Cigarette smoke and diesel particles functionally inhibit lung organoid formation by epithelial progenitors. Alveolar organoid formation was particularly more sensitive to these exposures. We speculate such a mechanism may contribute to defective alveolar repair in COPD.