Abstract DP039: Fecal Microbiota Transplantation Mitigates Chronic Inflammation and Behavioral Deficits After Neonatal Brain Injury

Chronic inflammation persists for years after neonatal hypoxic-ischemic encephalopathy (HIE), impairing brain development and offering a target for chronic therapy. Growing evidence links gut microbiota to neurodevelopment and chronic inflammation. We hypothesized that HIE disrupts the gut microbiota and that microbiome restoration can reduce inflammation and improve outcomes. Using the Rice-Vannucci model, we compared pups with HIE vs controls (hypoxia alone or naïve). Gut inflammation was assessed histologically, by qPCR, and gene expression profiling (NanoString nCounter). Microbiota composition was analyzed at 24 hours and 5 months post-HIE by 16S rRNA sequencing. Fecal microbiota transplantation (FMT) from naïve donors was performed into HIE or hypoxia-sham mice and vice versa. Flow cytometry was conducted at 5 months, and behavioral testing was performed longitudinally. HIE brain injury, but not hypoxia alone, caused acute gut injury and elevated TNF-α (p<0.05). At the onset of the chronic phase, HIE mice showed significantly elevated TNF-α, IL-1β, CXCL10, and CCL2 alongside increased ARG1, CD206, CD163, and TGF-β1, indicating unresolved inflammation. HIE pups had a lower mean relative abundance of Lactobacillus 24 hours (p<0.05) and of Lactobacillus, Bifidobacterium, and Ruminococcus genera 5 months (p<0.01) after HIE. This indicates a loss of bacteria crucial for the production of short-chain fatty acids (SCFA), pivotal for gut barrier integrity, immune modulation, and brain health. At 5 months, mice with HIE vs controls had a higher % of myeloid (M) and a lower % of lymphoid (L) cells (M:L ratio= 0.9; p< 0.001), indicating persistent systemic inflammation vs controls (M:L = 0.15). Interestingly, FMT from age-matched controls into HIE mice significantly decreased myeloid cells and increased lymphocytes (M:L= 0.3; p<0.01), suggesting an anti-inflammatory effect. Healthy FMT had no effect in the hypoxia controls, supporting the specificity of this intervention for HIE-induced systemic inflammation. FMT of naïve-biome into HIE mice reversed the hyperactivity/anxiety phenotype observed chronically post-HIE. Conversely, biome from HIE mice induced depressive behavior in naïve mice (p<0.01). HIE induces gut inflammation, depletion of SCFA-producing bacteria, and persistent immune dysregulation. Restoration of a healthy biome reduced inflammation and improved behavioral outcomes, underscoring the gut-brain axis as a promising chronic therapeutic target.