Time-dependent changes of microglial exosomal miRNAs expression signatures following repetitive mild traumatic brain injury

To acquire the time profiling of miRNA levels in microglial exosomes from injured brain after rmTBI, we employed a developed rmTBI mice model, and harvested the microglial exosomes at 1, 3, 7, 14, 21, 28, 35 and 42 DPI. The exosomes were first identified by TEM scanning, NTA measurement and Western Blot. miRNA microArray was performed to detect the miRNA levels in microglial exosomes after rmTBI. 3, 14 and 42 DPI were selected to respectively represents the time-point of acute phase, sub-acute phase and chronic phase after rmTBI. 10 miRNAs had an expression change of more than two-folds (up- or down-regualted) with a P value less than 0.05 at the 3 time-points. Among them, the expression changes of miR-124-3p were particularly evident. In addition, miR-124-3p was the only miRNA that up-regulated at 3 and 14 DPI, and down-regulated (reversely expressed) at 42 DPI, suggesting that its low expression in the chronic phase after rmTBI may exert a reverse impact on neural pathology, compared with that in the acute and sub-acute phase. miRNA microArray was performed to detect the miRNA levels in microglial exosomes after rmTBI. 3, 14 and 42 DPI were selected to respectively represents the time-point of acute phase, sub-acute phase and chronic phase after rmTBI.