Differentiation and functionality of human bronchial epithelial cells in an air-liquid interface culture are modified by irradiation exposure

Kim Röder¹Sylvie Lerchl¹David Eilenstein¹Carola Hartel¹Insa Sigrid Schroeder¹Gerhard Thiel²Michael Scholz¹Claudia Fournier^1*

• ¹Biophysics, GSI Helmholtz Center for Heavy Ion Research, Helmholtz Association of German Research Centres (HZ), Darmstadt, Hessen, Germany
• ²Technische Universitat Darmstadt Fachbereich Biologie, Darmstadt, Germany

ABSTRACT Introduction: We investigated the effects of α-particle and X-ray irradiation on a human bronchial epithelium model, representing environmentally and medically relevant exposure. Our focus was on non-cancer outcomes, namely mucociliary transport (MCT) and epithelial barrier function, both crucial for cancer risk assessment and therapeutic efficacy. Materials and Methods: Basal stem cells were irradiated and terminally differentiated under air–liquid interface conditions into all epithelial cell types. Clonogenic survival assays were used to determine iso-effective doses. MCT was assessed by video tracking of fluorescent bead transport. Cell differentiation was characterized by qPCR for basal, ciliated, goblet, and club cell markers, and mucus composition was analyzed by ELISA for MUC5AC. Barrier integrity was evaluated by transepithelial electrical resistance (TEER) for ion permeability and FITC-Dextran flux for macromolecular permeability. Motility markers were assessed by unjamming transition (UJT) and epithelial-mesenchymal transition (EMT) by morphology and EMT specific mRNA expression. Inflammatory mediator release was quantified by qPCR and ELISA. Results: Irradiation reduced bead transport velocity and directedness, indicating impaired MCT. Differentiation marker expression suggested a shift from ciliated to secretory cells, without a corresponding increase in MUC5AC secretion. Barrier function was differentially affected: ion permeability decreased, whereas macromolecular permeability increased. Morphological changes were partially consistent with UJT, but not EMT. Inflammatory mediator levels remained unchanged. Discussion: MCT impairment did not correlate consistently with the observed differentiation shift. Radiation-induced transition processes, particularly UJT, may underlie the altered permeability. Non-cancer effects were most pronounced at higher doses, with stronger responses to X-ray compared to α-particle exposure, while the lower doses, still being significantly higher than the radiation exposure of a radon spa therapy, had no significant effect.