Early-life gut microbiome maturity regulates blood-brain barrier and cognitive development.

The gut microbiome is an emerging factor in the neurobiology of disease. Blood-brain barrier (BBB) integrity is essential for proper brain function. However, the role the initial microbiome plays in BBB and brain development is unclear. In this study, we colonized germ-free pregnant mice with human full-term- or preterm-infant-derived gut microbiota, thereby establishing these communities in the resulting offspring. We discovered that mice harboring a full-term-associated microbiome exhibited stronger memory and learning capabilities and dramatically decreased early-life BBB permeability when compared to those with a prematurity-associated microbiome. Whole-brain single-cell RNA sequencing revealed downregulation of synaptic signaling genes in BBB cell types of mice with the prematurity-associated microbiome, indicating that microbiome maturity influences BBB transcriptional programs that support cognitive development. Comprehensive metagenomics and metabolomics uncovered bacterial populations and genomic pathways corresponding with decreased levels of circulating long-chain acylcarnitines and lysophosphatidylcholines in mice with the full-term-associated microbiome. Our findings highlight the microbiome as a therapeutic target for improving long-term neurodevelopmental outcomes due to its effect on the early-life BBB.