Experimental groups

Initially, mice were randomly allocated into six groups (n=6 for each group): sham group (mice were subjected to scalp incision procedure only) and TBI groups (3, 6, 12, 24 and 72 hours [h]). Sham mice were sacrificed right after operation and TBI mice were euthanized at the indicated time-point after TBI. Their brain samples were collected for further analysis.

Furthermore, mice were randomly assigned to 4 groups: 1) sham group, 2) TBI group, 3) TBI + FTY720 group: FTY720 (0.5 mg/kg, Selleck chemicals, Houston, TX, USA) was intraperitoneally administered right after TBI. 4) TBI + vehicle group, equal volumes of vehicle [1% dimethylsulfoxide (DMSO)] were injected immediately after TBI. FTY720 with a purity of more than 99% was dissolved in saline containing 1% DMSO.