Notch1 Signaling Activation Contributes to Adult Hippocampal Neurogenesis Following Traumatic Brain Injury

BACKGROUND Neural stem cells are reported to exist in the hippocampus of adult mammals and are important sources of neurons for repair. The Notch1 signaling pathway is considered as one of the important regulators of neural stem cells, but its role in adult brains is unclear. We aimed to describe the role of Notch1 signaling in the adult rat hippocampus after traumatic brain injury. MATERIAL AND METHODS The model rats were randomly divided into 4 groups as follows: sham, sham-TBI, sham-Ad-TBI, and NICD-Ad-TBI. We used adenovirus-mediated gene transfection to upregulate endogenous NICD in vivo. Firstly, a TBI rat model was constructed with lateral fluid percussion. Then, the hippocampus was collected to detect the expression of Notch1 markers and stem cell markers (DCX) by Western blot analysis, immunohistochemistry, and immunofluorescence. The prognosis after TBI treatment was evaluated by the Morris Water Maze test. RESULTS First, we found the expression of NICD in vivo was significantly increased by adenovirus-mediated gene transfection as assessed by Notch1 immunofluorescence and Western blot analysis. Second, enhancing NICD stimulated the regeneration of neural stem cells in the DG of the adult rat brain following traumatic brain injury, as evaluated by DCX and NeuN double-staining. Furthermore, Notch1 signaling activation can promote behavioral improvement after traumatic brain injury, including spatial learning and memory capacity. CONCLUSIONS Our findings suggest that targeted regulation of Notch1 signaling may have a useful effect on stem cell transformation. Notch1 signaling may have a potential brain-protection effect, which may result from neurogenesis.