Lacticaseibacillus rhamnosus GG modulates epithelial responses to space-relevant heavy-ion irradiation in a human gut-on-chip

Space radiation poses significant risks to human health, particularly to the radiation-sensitive gastrointestinal tract, yet the role of the microbiome in modulating intestinal responses to space-relevant heavy-ion exposure remains poorly understood due to the lack of advanced human-relevant experimental models. Here, we adapted a previously developed gut-on-chip (HuMiX) that recapitulates host-microbiome crosstalk to investigate the specific role of Lacticaseibacillus rhamnosus GG (LGG) on the radiation response of normal human intestinal cells (FHs 74 Int) after exposure to 600 MeV per nucleon Si-28 or 1 GeV per nucleon Fe-56 ions. First, results showed that LGG induced transcriptional reprogramming characterized by reduced proliferative signaling and changes in metabolic and epithelial organization pathway, confirming efficient interaction with the FHs 74 Int cells. Irradiation at an absorbed dose of 50 cGy of Si-28 or Fe-56 ions triggered canonical radiation responses, including activation of inflammatory signaling, DNA damage pathways, p53 signaling, and cell-cycle checkpoints, while suppressing developmental and epithelial differentiation programs. Despite shared radiation-response signatures, the two radiation qualities produced distinct transcriptional profiles: Fe-56 preferentially activated inflammatory and lipid metabolic pathways, whereas Si-28 induced interferon signaling, oxidative phosphorylation, and translation-related programs. Importantly, LGG modulated the radiation response with differences in DNA repair- and replication-associated transcriptional programs. Quantification revealed significantly reduced residual gamma-H2AX-53BP1 DNA damage foci in irradiated LGG-exposed cells compared with irradiated cells cultured without LGG. Together, these findings demonstrate the utility of organ-on-chip platforms to investigate human tissue responses to space radiation and reveal a potential microbiome-mediated mechanism of intestinal radioprotection.