PURPOSE: Radioactive cesium-bearing microparticles (CsMPs) were generated by the Fukushima Daiichi nuclear power plant (FNPP) accident. Despite their low radioactivity, CsMPs are insoluble and their dose distribution to the surrounding tissues is non-uniform, raising concerns about their biological effects. In this study, we investigated the cellular effects of CsMPs collected from soil contaminated by the FNPP accident. MATERIALS AND METHODS: Each three CsMP was placed on immortalized normal human epithelial cells (hTERT-RPE1) and co-incubated for up to 72 h. Induction of DNA double-strand breaks (DSBs) and cell proliferation were analyzed in relation to the distance from a CsMP. In addition, gene expression analysis was performed after cells were co-incubated with a CsMP for 24 h. RESULTS: Cs), induced DSBs and growth arrest in adjacent cells at high radiation doses. DSBs were also induced in cells 1 cm distant from CsMP-1; however, these cells maintained their ability to proliferate. CsMP-1 also induced the expression of interferon-stimulated genes (ISGs) involved in inflammatory responses and stress tolerance in cells proximal to CsMP-1. Neither a non-radioactive mock particle nor CsMP-3, containing 7.6 Bq of radioactive Cs, influenced DSB induction, even in the adjacent cells. CONCLUSIONS: Our study suggests that factors secreted by cells that undergo premature senescence following high-dose exposure to CsMP-1 may confer a growth advantage to cells experiencing DSBs at a distance from the CsMP.
Suzuki et al. (2026) studied this question.