Spatial Transcriptomics and Dual Dye Mapping Identify Wnt-Driven BBB Protection in Endothelial EphA4-Deficiency

Blood-brain barrier (BBB) disruption is a key pathological event following traumatic brain injury (TBI), yet its molecular and spatial characteristics remain incompletely understood. Here, we developed a dual dye-labeling system to assess the temporal and spatial dynamics of BBB permeability following controlled cortical impact (CCI) injury in EphA4f/f VE-Cadherin-CreERT2 (KO) and EphA4f/f (WT) mice. By tracking Evans Blue Dye (EBD), sodium fluorescein (NaFl), and IgG deposition, we reveal distinct patterns of extravasation in the injured cortex and hippocampus. NaFl, a small-molecule tracer, continues to extravasate for 7 days post-injury, whereas EBD leakage diminishes after 4 days. Notably, EC-specific EphA4 KO mice exhibit a protective role in BBB integrity. To further investigate BBB regulation, we integrated spatial transcriptomics with dye quantification, revealing that EphA4 EC ablation upregulates key BBB-related genes (Tjp2, Tjp3, Cldn1, and Ocln) and neuroprotective genes (Nr4a1 and Npas4). Notably, Wnt signaling genes are upregulated in the KO cortex, and we demonstrate that inhibition of Frizzled-4 (FZD4)/Wnt attenuates BBB protection in KO mice. Importantly, direct pharmacological activation of Wnt signaling with the FZD4 agonist FZM1.8 reduces lesion volume and BBB disruption. Overall, these findings demonstrate the effectiveness of spatial transcriptomics and dual-dye labeling in uncovering region-specific transcriptional changes associated with BBB disruption following CCI injury and in assessing the influence of EphA4/Wnt signaling. Wnt signaling emerges as a promising pathway for BBB protection and repair following TBI, offering a potential strategy to mitigate secondary brain injury.