EGFR activation correlates with intracranial pressure and outcome in a mixed intracranial bleeding porcine model

The pig model is an advanced system for studying human brain injury due to its anatomical similarities with the brain, such as brain size, gyrencephalic structure, skull shape, and white-to-gray matter ratio. Brain hemorrhage increases intracranial pressure through blood accumulation and brain swelling, leading to impaired cerebral blood flow, ischemia, and potentially, secondary injury, thus further exacerbating neurological damage. This study investigates the role of receptor tyrosine kinases (RTKs) in the injury response and clinical outcomes, focusing on their potential as therapeutic targets for intracranial pressure control after injury.

To this end, we developed a sustained, resuscitated pig model of acute mixed intracranial bleeding with ICP and hemorrhagic shock. Multimodal brain monitoring and neurological assessments offered insights into the progression of the injury.

Our findings showed that 36-48 hours post-injury, animals exhibited signs of cerebral tissue hypoxia, neuroinflammation, and extensive tissue damage. Elevated HIF1-α expression in the injured hemisphere confirmed local hypoperfusion. Inflammatory markers such as TNF-α, CD68, and MMP-9 were upregulated in both hemispheres, reflecting a generalized neuroinflammatory response. Gene expression analysis revealed increased markers of vascular, astrocytic, and neuroimmune activation, particularly related to endothelial integrity and astrocyte activation.

RTK expression analysis showed increased levels of VEGFR1, VEGFR2, Tie-2, EGFR, and Axl in the injured cortex, with activation of EGFR/ErbB4 and HGFR/Met pathways. Hierarchical clustering of our transcriptional analysis revealed distinct patterns of activation, highlighting the direct relationship between severity of ICP increase and astrocyte response. In particular, EGFR phosphorylation correlated with i) severity of ICP increase, ii) neurological evaluation using a modified Glasgow Coma Scale, and iii) survival.

These findings suggest that modulating EGFR signaling may offer a therapeutic approach for managing ICP and improving outcome in traumatic brain injury.