Disrupted blood-brain barrier maturation links congenital heart diseases to hippocampal injury: Insights from a translational neonatal mouse model.

BACKGROUND

Neurodevelopmental impairment is the most common non-cardiac morbidity in children with congenital heart diseases (CHDs), yet its pathogenic mechanisms remain poorly understood due to a lack of disease-specific animal models. Right ventricular outflow tract obstruction (RVOTO) is a prevalent CHD lesion. We investigated whether neonatal RVOTO disrupts postnatal brain maturation, focusing on the blood-brain barrier (BBB).

METHODS

RVOTO was induced in postnatal day 1 (P1) C57BL/6 mouse pups via pulmonary artery banding (PAB); sham-operated littermates served as controls. Hemodynamics were validated by echocardiography. At P21, brain tissues were analyzed using bulk RNA-sequencing, qRT-PCR, immunofluorescence, and Nissl staining to assess BBB-associated pathways and neuropathology.Functional BBB integrity was assessed via FITC-dextran extravasation and transmission electron microscopy (TEM). An intermediate time point (P14) was also examined.

RESULTS

PAB successfully established hemodynamically significant RVOTO. Transcriptomic analysis revealed 2611 differentially expressed genes in RVOTO brains. Gene Ontology and KEGG enrichment analyses indicated significant disruption of biological processes and pathways critical for BBB maturation, including cell adhesion, ion transport, and extracellular matrix organization. BBB functional impairment was confirmed by increased FITC-dextran leakage and ultrastructural abnormalities, including disrupted tight junctions and detached astrocytic end-feet. BBB maturation impairment was further confirmed by substantial hippocampal pathology and a significant reduction of astrocytes, the critical cell type for BBB maturation. Quantitative analyses revealed region-specific astrocyte reduction and neuronal loss, particularly in the dentate gyrus (DG) and Cornu Ammonis (CA) regions. These changes were already detectable at P14, suggesting a failure of maturation.

CONCLUSIONS

We present the first neonatal mouse model of RVOTO that recapitulates CHD-associated brain dysmaturation. The model demonstrates that neonatal RVOTO disrupts BBB maturation, primarily through astrocytic deficiency, and leads to hippocampal injury. These findings provide a direct mechanistic link between a specific cardiac lesion and the pattern of neurodevelopmental deficits observed in children with CHDs, offering a novel platform for investigating the heart-brain axis and testing future neuroprotective strategies.