Establishment and Application of a NovelIn VitroModel of Microglial Activation in Traumatic Brain Injury

Abstract

Mechanical impact-induced primary injury after traumatic brain injury (TBI) leads to acute microglial pro-inflammatory activation and consequently mediates neurodegeneration, which is a major secondary brain injury mechanism. However, the detailed pathologic cascades have not been fully elucidated, partially because of the pathologic complexity in animal TBI models. Although there are severalin vitroTBI models, none of them closely mimic post-TBI microglial activation. In the present study, we aimed to establish anin vitroTBI model, specifically reconstituting the pro-inflammatory activation and associated neurodegeneration following TBI. We proposed three sets of experiments. First, we established a needle scratch injured neuron-induced microglial activation and neurodegenerationin vitromodel of TBI. Second, we compared microglial pro-inflammatory cytokines profiles between thein vitroTBI model and TBI in male mice. Additionally, we validated the role of injured neurons-derived damage-associated molecular patterns in amplifying microglial pro-inflammatory pathways using thein vitroTBI model. Third, we applied thein vitromodel for the first time to characterize the cellular metabolic profile of needle scratch injured-neuron-activated microglia, and define the role of metabolic reprogramming in mediating pro-inflammatory microglial activation and mediated neurodegeneration. Our results showed that we successfully established a novelin vitroTBI model, which closely mimics primary neuronal injury-triggered microglial pro-inflammatory activation and mediated neurodegeneration after TBI. Thisin vitromodel provides an advanced and highly translational platform for dissecting interactions in the pathologic processes of neuronal injury-microglial activation-neuronal degeneration cascade, and elucidating the detailed underlying cellular and molecular insights after TBI.SIGNIFICANCE STATEMENTMicroglial activation is a key component of acute neuroinflammation that leads to neurodegeneration and long-term neurologic outcome deficits after TBI. However, it is not feasible to truly dissect primary neuronal injury-induced microglia activation, and consequently mediated neurodegenerationin vivo. Furthermore, there is currently lacking ofin vitroTBI models closely mimicking the TBI primary injury-mediated microglial activation. In this study, we successfully established and validated a novelin vitroTBI model of microglial activation, and for the first time, characterized the cellular metabolic profile of microglia in this model. This novel microglial activationin vitroTBI model will help in elucidating microglial inflammatory activation and consequently associated neurodegeneration after TBI.