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The following is a summary of “Radiation decreases bronchial epithelial progenitor function as assessed by organoid formation,” published in the January 2025 issue of the Respiratory Research by Kuipers et al.

Radiation-induced lung injury (RILI) is a significant adverse effect of radiotherapy for lung cancer, with damage to normal lung epithelium playing a crucial role in disease progression. However, the precise cellular mechanisms contributing to this injury remain incompletely understood. This study aimed to evaluate the impact of ionizing radiation (IR) on well-differentiated primary bronchial epithelial cells (PBEC), focusing on cytotoxicity, barrier function, inflammation, and epithelial progenitor capacity.

To investigate these effects, PBEC were cultured at the air-liquid interface (ALI) to allow mucociliary differentiation. The effects of IR at doses of 1, 2, 4, and 8 Gray (Gy) were assessed through multiple parameters, including lactate dehydrogenase (LDH) release and trans-epithelial electrical resistance (TEER) to evaluate cytotoxicity and barrier integrity. Gene expression analysis using quantitative PCR was performed to assess markers associated with cell cycle regulation (P21/CDKN1A, MKI67, E2F1, AEN, ATF3), while immunofluorescence staining for γH2Ax foci was used to evaluate DNA damage. Additionally, epithelial progenitor function was assessed by studying organoid formation capacity at 24 hours and 7 days post-irradiation.

Results demonstrated that IR led to a significant increase in γH2Ax foci, indicative of double-stranded DNA breaks, but did not induce notable changes in LDH release or TEER, suggesting an absence of direct cytotoxic effects or compromised barrier integrity. Furthermore, IR exposure did not upregulate markers associated with inflammation or epithelial-mesenchymal transition (EMT). However, IR had a substantial impact on cell cycle regulation, with significant upregulation of the cell cycle inhibitor P21/CDKN1A and a concurrent downregulation of proliferation markers MKI67 and E2F1. Notably, IR led to a marked and dose-dependent impairment in organoid formation capacity, which persisted for at least 7 days post-exposure, highlighting a sustained disruption of epithelial progenitor function.

In conclusion, while IR exposure did not induce overt cytotoxicity, inflammation, or EMT-related changes, it significantly impaired epithelial progenitor function, as evidenced by reduced organoid formation capacity. This effect was accompanied by DNA damage, upregulation of P21/CDKN1A, and suppression of proliferation markers. These findings indicate that organoid formation assays provide a highly sensitive method for evaluating the impact of IR on normal lung epithelial cells and could serve as a valuable tool in studying RILI. Further research is necessary to explore potential therapeutic interventions aimed at preserving epithelial progenitor function and mitigating radiation-induced lung damage.

Source: respiratory-research.biomedcentral.com/articles/10.1186/s12931-025-03105-z