Cerebral microthrombi promote focal Cav-1-dependent blood-brain barrier impairment, triggering neuroinflammation and neuronal damage after traumatic brain injury

Traumatic brain injury (TBI) is frequently accompanied by blood-brain barrier (BBB) dysfunction, but the microvascular events that initiate barrier failure and secondary neural injury have remained poorly understood. This study set out to identify those initiating events and the endothelial program that links them to downstream damage.

Using highly sensitive fluorescent nanoscale tracers, correlative light and electron microscopy, single-cell transcriptomics, and genetic manipulation of Caveolin-1 (Cav-1), the authors examined BBB leakage after TBI in mice. They found that leakage occurs focally at sites of cerebral microthrombus formation rather than uniformly. Endothelial cells adjacent to microthrombi remained structurally intact but displayed a distinct transcriptional program enriched in both thrombosis- and transcytosis-related genes, including Cav-1.

Microthrombi promoted Cav-1-dependent transcytosis and size-selective extravasation of blood-borne proteins, exposing the surrounding parenchyma to circulating factors and inducing focal microglial activation and neuronal damage in vivo. In human induced pluripotent stem cell-derived neurons, these blood-borne proteins directly impaired neuronal structure and network function. Genetic deletion of Cav-1 markedly reduced microthrombus-associated BBB leakage, immune-cell diapedesis, microglial activation, and neuronal loss, while endothelial re-expression of Cav-1 using AAVs restored leakage.

Human TBI data showed early dynamic coagulation dysregulation associated with adverse clinical outcome, focal cerebral vascular injury, and endothelial transcriptional signatures consistent with reduced barrier integrity and increased caveolae-associated transport.

Together, the findings identify cerebral microthrombi as focal sites of Cav-1-dependent BBB dysfunction and establish pathological endothelial transcytosis as a mechanistic link between post-traumatic microvascular thrombosis, blood protein extravasation, and secondary neuronal injury. Targeting Cav-1-dependent transcytosis may therefore provide a strategy to limit pathological BBB permeability and secondary injury after TBI.