<scp>SCG2</scp> mediates blood–brain barrier dysfunction and schizophrenia‐like behaviors after traumatic brain injury

Traumatic brain injury (TBI), which is characterized by acute neurological dysfunction, is also one of the most widely recognized environmental risk factors for various neurological and psychiatric disorders. However, the role of TBI in neurological perturbation and the mechanisms underlying these disorders remain unknown. We evaluated transcriptional changes in cells of the frontal cortex after TBI by exploiting single-cell RNA sequencing (scRNA-Seq). We adopted the gene expression omnibus and scRNA-Seq to identify the mediation by secretogranin II (SCG2) of TBI-induced schizophrenia. Astrocytes are a principal source of SCG2 in the frontal cortex after TBI. Our analysis indicated that SCG2-triggered disruption of the blood-brain barrier (BBB) via the CypA-MMP-9 signaling pathway. Furthermore, astrocytic SCG2 knockout in the frontal cortex reduced BBB damage, mitigated inflammation, and inhibited schizophrenia after TBI. In conclusion, we identified the SCG2-CypA-MMP-9 signaling pathway in reactive astrocytes as a key switch in the protection of the BBB and provided a novel therapeutic avenue for treating psychiatric disorders after TBI.