Traumatic Brain Injury Stimulates Neural Stem Cell Proliferation via Mammalian Target of Rapamycin Signaling Pathway Activation

TBI activates mTORC1 signaling in NSCs. Mice received a moderate CCI at the age of 9 weeks and were sacrificed at 24 or 48 h after injury as well as after sham injury (n = 5 for each group). A–I, Immunostaining with antibodies against GFP (green) and pS6 (red) shows mTORC1 signaling activation in NSCs (white arrows) in sham animals (A–C) 24 h (D–F) and 48 h (G–I) after CCI in the subgranular zone. J, Quantification of total pS6-positive NSCs after sham surgery and 24 and 48 h after CCI, respectively. K, Quantification of percentage of pS6-positive NSCs in the epicenter after sham surgery and 24 and 48 h after CCI, respectively (*p < 0.05, **p < 0.01, ***p < 0.001).

TBI activates mTORC1 signaling in proliferating NSCs. Mice received a moderate CCI at the age of 9 weeks and were sacrificed at 24 or 48 h after injury as well as after sham injury (n = 5 for each group). A dose of BrdU was administered 4 h before perfusion. A, Experimental strategy. B–M, Immunostaining with antibodies against GFP (green), BrdU (cyan), and pS6 (red) shows proliferating NSCs with (white arrows) or without (arrowheads) mTORC1 signaling activation in sham animals (B–E), 24 h (F–I) and 48 h (J–M) after CCI in the subgranular zone. N–P, Quantification of total proliferating NSCs (N), total pS6-positive proliferating NSCs (O), and total pS6-negative proliferating NSCs (P) after sham surgery and 24 and 48 h after CCI, respectively. Q, Quantification of percentage of pS6-positive proliferating NSCs after sham surgery and 24 and 48 h after CCI, respectively (*p < 0.05, **p < 0.01, ***p < 0.001).

Rapamycin treatment inhibits mTORC1 signaling and cell proliferation in the hippocampus after TBI. A, Experimental strategy. B–E, Immunostaining with antibody against pS6 (red) shows mTORC1 signaling activity after rapamycin or vehicle treatment in sham animals or 48 h after CCI. F–I, Immunostaining with antibodies against BrdU (red) shows cell proliferation in the HDG after rapamycin or vehicle treatment in sham animals or 48 h after CCI. DAPI staining shows structure of HDG.

Inhibition of mTORC1 signaling ablates TBI-enhanced NSC proliferation. Mice were treated with the same procedure as in Figure 4A (n = 5 for each group). A–L, Immunostaining with antibodies against GFP (green) and BrdU (red) shows NSC proliferation (white arrows) in the SGZ after rapamycin or vehicle treatment in sham animals and 48 h after CCI. M, Quantification of NSC proliferation in the SGZ after rapamycin or vehicle treatment in sham animals and 48 h after CCI (*p < 0.05, **p < 0.01, ***p < 0.001).