TREM2 affects DAM-like cell transformation in the acute phase of TBI in mice by regulating microglial glycolysis

Background: Traumatic brain injury (TBI) is characterized by high mortality and disability rates. Disease-associated microglia (DAM) are a newly discovered subtype of microglia. However, their presence and function in the acute phase of TBI remain unclear. Although glycolysis is important for microglial differentiation, its regulatory role in DAM transformation during the acute phase of TBI is still unclear. In this study, we investigated the functions of DAM-like cells in the acute phase of TBI in mice, as well as the relationship between their transformation and glycolysis.

Methods: In this study, a controlled cortical impact model was used to induce TBI in adult male wild-type (WT) C57BL/6 mice and adult male TREM2 knockout mice. Various techniques were used to assess the role of DAM-like cells in TBI and the effects of glycolysis on DAM-like cells, including RT‒qPCR, immunofluorescence assays, behavioural tests, extracellular acidification rate (ECAR) tests, Western blot analysis, cell magnetic sorting and culture, glucose and lactate assays, and flow cytometry.

Results: DAM-like cells were observed in the acute phase of TBI in mice, and their transformation depended on TREM2 expression. TREM2 knockout impaired neurological recovery in TBI mice, possibly due in part to their role in clearing debris and secreting VEGFa and BDNF. Moreover, DAM-like cells exhibited significantly increased glycolytic activity. TREM2 regulated the AKT‒mTOR‒HIF-1α pathway and glycolysis in microglia in the acute phase of TBI. The increase in glycolysis in microglia partially contributed to the transformation of DAM-like cells in the acute phase of TBI in mice.

Conclusions: Taken together, the results of our study demonstrated that DAM-like cells were present in the acute phase of TBI in mice. TREM2 might influence DAM-like cell transformation by modulating the glycolysis of microglia. Our results provide a new possible pathway for intervening TBI.