Micronucleus formation in human keratinocytes is dependent on radiation quality and tissue architecture

• Published in: Environmental and molecular mutagenesis Vol. 56; no. 1; pp. 22 - 31
• Main Authors: Snijders, Antoine M., Mannion, Brandon J., Leung, Stanley G., Moon, Sol C., Kronenberg, Amy, Wiese, Claudia
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01-01-2015; Wiley Subscription Services, Inc
• Subjects: Architecture; Boats; Cell Culture Techniques; Cell Proliferation - radiation effects; Cytokinesis - radiation effects; DNA damage; DNA repair; Dose-Response Relationship, Radiation; Epidermis - pathology; Epidermis - radiation effects; Fibroblasts - pathology; Fibroblasts - radiation effects; Gamma Rays - adverse effects; Humans; Immunoenzyme Techniques; Infant, Newborn; Keratinocytes - pathology; Keratinocytes - radiation effects; Micronuclei, Chromosome-Defective - radiation effects; Micronucleus Tests; organotypic epithelia; RBE; risk prediction; space radiation; organotypic epithelia; space radiation; RBE; DNA damage; risk prediction
• ISSN: 0893-6692; 1098-2280
• DOI: 10.1002/em.21887

The cytokinesis‐block micronucleus (MN) assay was used to assess the genotoxicity of low doses of different types of space radiation. Normal human primary keratinocytes and immortalized keratinocytes grown in 2D monolayers each were exposed to graded doses of 0.3 or 1.0 GeV/n silicon ions or similar energies of iron ions. The frequencies of induced MN were determined and compared to γ‐ray data. RBEmax values ranged from 1.6 to 3.9 for primary keratinocytes and from 2.4 to 6.3 for immortalized keratinocytes. At low radiation doses ≤0.4 Gy, 0.3 GeV/n iron ions were the most effective at inducing MN in normal keratinocytes. An “over‐kill effect” was observed for 0.3 GeV/n iron ions at higher doses, wherein 1.0 GeV/n iron ions were most efficient in inducing MN. In immortalized keratinocytes, 0.3 GeV/n iron ions produced MN with greater frequency than 1.0 GeV/n iron ions, except at the highest dose tested. MN formation was higher in immortalized keratinocytes than in normal keratinocytes for all doses and radiation qualities investigated. MN induction was also assessed in human keratinocytes cultured in 3D to simulate the complex architecture of human skin. RBE values for MN formation in 3D were reduced for normal keratinocytes exposed to iron ions, but were elevated for immortalized keratinocytes. Overall, MN induction was significantly lower in keratinocytes cultured in 3D than in 2D. Together, the results suggest that tissue architecture and immortalization status modulate the genotoxic response to space radiation, perhaps via alterations in DNA repair fidelity. Environ. Mol. Mutagen. 56:22–31, 2015. © 2014 Wiley Periodicals, Inc.