Single-cell sequencing reveals intracranial microvasculature-derived CXCL12 promotes CD8+ T-cell infiltration and blood–brain barrier dysfunction after subarachnoid hemorrhage in mice

Processes related to how the intracranial microvasculature initiates brain‒peripheral crosstalk for subsequent blood‒brain barrier (BBB) dysfunction at an early stage after subarachnoid hemorrhage (SAH) ictus are still unknown. This study elucidated the effect and potential mechanism of intracranial microvasculature-mediated T-cell infiltration on BBB function after SAH. Publicly available single-cell RNA sequencing data related to SAH ( https://ngdc.cncb.ac.cn/omix ; Accession No. OMIX006611) were retrieved and analyzed. The dataset was derived from the white matter region of adult male C57BL/6J mice at 1 and 7 days after experimental SAH. The SAH model was induced by endovascular perforation, and experiments were subsequently conducted at 1, 3, 7, and 14 days after SAH to evaluate T-cell infiltration, BBB integrity, neuronal injury, and neurological function. After SAH, CXCL12 expression was increased in endothelial cells and pericytes, promoting CD8+ T-cell infiltration via the CXCR4 pathway. This immune infiltration appeared to exacerbate BBB disruption and contribute to worsened neurological function. Blocking CXCL12-CXCR4 signaling with a CXCL12 neutralizing antibody or the CXCR4-specific inhibitor AMD3100 significantly reduced CD8+ T-cell infiltration, attenuated BBB damage and improved the neurobehavioral outcomes of SAH mice. This study suggests that, following SAH, both pericytes and endothelial cells may contribute to immune regulation by producing CXCL12, which promotes CD8⁺ T-cell infiltration into the brain. This mechanism may play a role in BBB disruption and neurological dysfunction. Targeting the CXCL12-CXCR4 axis could offer a potential approach for mitigating immune-mediated injury after SAH.