Maternal gut dysbiosis is associated with altered enteric and cortical inhibitory circuit development

Maternal environmental factors critically influence neural circuit maturation during early development. The maternal gut microbiota has emerged as an important upstream regulator of offspring neurodevelopment, yet its role in shaping the structural organization of enteric and cortical inhibitory circuits remains poorly defined. Here, we examined whether gestational disruption of the maternal gut microbiota is associated with alterations in parallel enteric and cortical inhibitory circuit development.

Maternal gut dysbiosis was induced in pregnant GAD67-GFP mice by oral vancomycin administration during gestation. Maternal and offspring microbiota were analyzed using full-length 16S rRNA gene sequencing to assess microbial diversity and vertical transmission. Offspring were examined at postnatal day 14 for intestinal morphology, altered barrier integrity, and enteric nervous system (ENS) organization. Cortical inhibitory circuits were analyzed by quantifying GAD67-positive interneuron density and performing three-dimensional morphological reconstruction in layers II/III of the somatosensory cortex, motor cortex, medial entorhinal cortex, and CA1 region of the hippocampus.

Maternal dysbiosis significantly reduced microbial diversity and disrupted maternal-offspring microbial transmission. These changes were associated with impaired intestinal development, including reduced crypt height, thinning of the muscularis propria, fragmented Claudin-1 expression, and reduced Auerbach's plexus area without changes in neuronal density, indicating altered enteric network organization. In the brain, maternal dysbiosis induced region-specific cortical vulnerability, with reduced dendritic length and branching of GAD67-positive interneurons in the somatosensory and motor cortices, while interneuron morphology in the medial entorhinal cortex and hippocampus was preserved. Interneuron density was selectively reduced in the motor cortex.

These findings indicate that gestational maternal dysbiosis is associated with co-occurring structural alterations in intestinal and cortical inhibitory systems, selectively affecting inhibitory circuit architecture in sensorimotor regions. While the present model does not isolate microbiota-specific mechanisms from potential antibiotic-induced maternal physiological changes, the data support an association between disrupted maternal microbial ecology and offspring enteric and cortical neuroanatomical development during early postnatal life. These findings should be interpreted as descriptive associations and do not establish mechanistic gut-brain interactions.