P1.092: Remote ischemic conditioning restores hippocampal developmental pathways during necrotizing enterocolitis

Background: Necrotizing enterocolitis (NEC) is an intestinal disease that results in neurodevelopmental impairments in 40% of survivors. Previous research has identified the hippocampus as a region most vulnerable to injury during early neonatal life. It has been found neuroinflammation in the hippocampus and memory dysfunction in NEC, but the specific pathways and cell types involved in memory impairment remain unclear. Furthermore, remote ischemic conditioning (RIC) has been utilized as a neuroprotective strategy to counteract NEC induced brain injury. The aim of this study was to evaluate immune, vascular, and plasticity-associated pathways in hippocampal cell types by analyzing the brain of NEC induced mice with or without RIC administration.

Methods: NEC was induced in postnatal day 5 (P5) mice using a combination of hypoxia, hyperosmolar formula feeding, and oral lipopolysaccharide (4 mg/kg). Breastfed P9 pups served as controls. RIC was performed by applying brief cycles of ischemia and reperfusion for four cycles on a hindlimb using a tourniquet. Spatial transcriptomics was performed using multiplexed error-robust fluorescence in situ hybridization (MERFISH) to detect over 500 mRNA transcripts at high resolution. UMAP dimensional reduction and differential gene expression (DGE) analyses were applied to identify distinct cell types and characterize transcriptomic changes and perform enrichment analysis to identify dysregulated pathways in the hippocampus of control, NEC, or NEC+RIC pup mice.

Results: UMAP analysis identified six populations of major cell types including astrocytes, granular progenitors, neurons, oligodendrocytes, vascular, and macrophage cells. Compared to control, we found mostly downregulated genes during NEC for all the cell types. The top 20 most significantly downregulated genes for astrocytes, neurons, and granular cells are labeled in the volcano plot (Fig. 1A-C). We used gProfiler tool to identify downregulated pathways. We found that WNT, VEGF, TGFB, Delta-Notch, and cytokine/immune signaling and regulation pathways were all downregulated during NEC. Interestingly, when RIC was administered during NEC, all genes were upregulated, and the downregulated pathways and processes were restored to normal (Fig 1A-C).

Conclusion: There is a region-specific brain injury in NEC, with significant alterations in developmental pathways in the hippocampus, which may contribute to the impaired memory function observed in survivors. Excitingly, we found that RIC has a neuroprotective effect by restoring hippocampal development during NEC-related brain injury. Future research will focus on glia-neuron interactions to further elucidate the neurodevelopmental consequences of NEC and the beneficial effects of RIC.