Post injury-released HMGB1 acts via TLR2/4 receptors to reduce the numbers of oligodendrocyte progenitor cells in vitro. (A) DAPI cell counts were significantly reduced in the presence of injury conditioned media, with no difference between control cultures and control conditioned medium. (B) NG2+ cells were significantly reduced in the presence of injury conditioned media compared to both control and control conditioned media. (C) There was no difference in GFAP+ cell counts in any of the conditioned media experiments. (D) Addition of BoxA, at a concentration of 100 ng/ml, did not affect NG2+ cell counts in control or control conditioned media conditions. However, BoxA rescued NG2+ cell counts in the presence of ICM to levels akin to the counts of control cultures (p < 0.0001). (E) Addition of ICM did not affect cell death in our cultures, assessed as the proportion of Caspase+ cells/DAPI+. For comparisons between two conditions, two-tailed student’s T-test was used, and for multiple different conditions, a two‐way ANOVA and one-way ANOVA with Dunnett's multiple comparison test was used. p values of < 0.05 were considered significant (*p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001). cNSPCs = rat cortical neural stem cell progenitors; CCM = controlled conditioned medium; ICM = injury conditioned medium; DIV = days in vitro.