RNA Sequencing Reveals Novel Gene Insights in Repeated Traumatic Brain Injury in vivo

The neuropathophysiological response following repeated TBIs is very poorly understood. To address this gap, we utilized a closed-head injury mouse model and RNA sequencing methods to evaluate the effects of single, and double TBIs, at both a mild and moderate severity, on the cortical transcriptome. Mouse cortical tissue transcriptome was analyzed twenty-four hours following injury, and a total of 1,356 genes were found to be statistically differentially expressed in at least one condition, compared to its respective control. 80 genes were significantly up/down regulated in the repeated TBI conditions, while 54 were significantly up/down regulated in the single TBI conditions. We found that TBI triggers important alterations in the expression of the genes encoding relaxin-3, orexin, oxytocin, and vasopressin, four neuromodulators associated with stress-related responses among their functions. Relaxin3 was the only gene that was significantly upregulated in all injury conditions compared to control, while orexin expression was increased by a mild single impact. Furthermore, impairments to the oxytocin-vasopressin system were demonstrated as a significant downregulation of oxytocin following repeated injuries, and a expressive increase in vasopressin expression after a single mild or moderate impact. Tumor necrosis factor was significantly elevated in the single and repeated moderate conditions, which is suggestive of possible neuroinflammation for TBI. Our transcriptome level analysis provides novel insights into the acute cortical response following repeated TBIs, suggesting potential molecular mechanisms underlying secondary injuries and neurobehavioral symptoms triggered by TBI.