Gut microbiota alterations are associated with uterine immune homeostasis via microbiota-metabolite interactions

Uterine inflammation is a major cause of infertility and is commonly associated with local bacterial infection. However, the association between gut microbiota and uterine immune homeostasis remains incompletely understood.

This study aimed to examine the association between gut microbiota dysbiosis and uterine inflammation, and to identify microbiota-associated factors linked to host immune responses.

An antibiotic-induced dysbiosis mouse model was established, followed by fecal microbiota transplantation (FMT), microbial supplementation, metabolite intervention, and acute E. coli challenge to assess inflammation-related outcomes. Uterine inflammation, barrier integrity, and immune responses were evaluated. Gut microbiota and fecal metabolites were profiled by 16S rRNA sequencing and untargeted metabolomics, respectively.

Gut microbiota dysbiosis was associated with increased uterine inflammation, as indicated by elevated cytokine levels, immune cell infiltration, and impaired epithelial barrier integrity, whereas FMT partially reversed these changes. Taxonomic analysis showed a marked reduction in Prevotellaceae abundance during dysbiosis, which increased following microbial reconstitution. Supplementation with Prevotella copri was associated with reduced uterine inflammation and improved barrier integrity in dysbiotic mice. Integrated microbiome-metabolome analysis revealed that allopregnanolone was strongly associated with Prevotellaceae abundance. Dysbiosis was accompanied by reduced allopregnanolone levels, which increased after FMT. Exogenous administration of allopregnanolone was associated with reduced inflammatory markers and improved epithelial barrier integrity. Importantly, gut microbiota dysbiosis was associated with increased susceptibility to E. coli-induced uterine inflammation, whereas FMT, Prevotella copri, and allopregnanolone were associated with attenuation of infection-related inflammatory responses and tissue injury.

Together, these findings support a microbiota-metabolite-host interaction pattern in which Prevotella copri, together with the host-associated metabolite allopregnanolone, is associated with uterine immune homeostasis. While these results provide functional insights, further studies are required to elucidate the mechanisms linking gut microbiota to uterine inflammation.