Faecal microbiota transplantation protects against radiation‐induced toxicity

Severe radiation exposure may cause acute radiation syndrome, a possibly fatal condition requiring effective therapy. Gut microbiota can be manipulated to fight against many diseases. We explored whether intestinal microbe transplantation could alleviate radiation‐induced toxicity. High‐throughput sequencing showed that gastrointestinal bacterial community composition differed between male and female mice and was associated with susceptibility to radiation toxicity. Faecal microbiota transplantation (FMT) increased the survival rate of irradiated animals, elevated peripheral white blood cell counts and improved gastrointestinal tract function and intestinal epithelial integrity in irradiated male and female mice. FMT preserved the intestinal bacterial composition and retained mRNA and long non‐coding RNA expression profiles of host small intestines in a sex‐specific fashion. Despite promoting angiogenesis, sex‐matched FMT did not accelerate the proliferation of cancer cells in vivo . FMT might serve as a therapeutic to mitigate radiation‐induced toxicity and improve the prognosis of tumour patients after radiotherapy. Synopsis Faecal microbiota transplantation ameliorates radiation‐induced toxicity in irradiated mice by improving gastrointestinal tract function and epithelial integrity, preserving gut bacterial composition and maintaining the small intestine transcriptome. Gut microbiota determines the radiosensitivity of hosts. Faecal microbiota transplantation (FMT) fights against radiation‐induced gastrointestinal toxicity. FMT preserves enteric bacterial composition and retains the RNA expression profile of irradiated hosts. FMT might emerge as a therapeutic schedule in tumour radiotherapy to improve prognosis. Graphical Abstract Faecal microbiota transplantation ameliorates radiation‐induced toxicity in irradiated mice by improving gastrointestinal tract function and epithelial integrity, preserving gut bacterial composition and maintaining the small intestine transcriptome.