ABSTRACT
Objective To investigate the proliferative capacity of neural stem cells (NSCs) in rat hippocampus after traumatic brain injury (TBI) and its relationship with Janus kinase 2/signaling and transcriptional activation factor 3 (JAK2/STAT3) signaling pathway activity.Methods A total of 108 SD rats were randomly divided into control group (36 rats) and TBI group (72 rats).The TBI model was constructed by PinPointTM Precision Cortical Impactor.At 1,3,7,14,21 and 28 days after injury,the brain tissues were taken for immunofluorescence staining to detect the proliferation of NSCs [5-bromodeoxyuridine (BrdU) +/stem cell key protein-2 (Sox2) +] in hippocampus,and phosphorylated JAK2 (p-JAK2) and phosphorylated STAT3 (p-STAT3) were detected by Western blot.The expression level of p-JAK2 and p-STAT3 as well as the changing trend were analyzed.On the basis of preliminary analysis of the proliferation of NSCs and the change of JAK2/STAT3 signaling pathway activity in hippocampus,another 24 SD rats were randomly divided into TBI + normal saline group and TBI +AG490 (JAK2 specific inhibitor) group,with 12 rats in each group.At 7 days after injury,the proliferation of NSCs in hippocampus was detected by immunofluorescence staining,and the expression levels of p-JAK2 and p-STAT3 were detected by Western blot,so as to further confirm the correlation between the proliferation ability of NSCs in hippocampus and JAK2/STAT3 signaling pathway.Results Compared with the control group,the number of NSCs in the hippocampus of the TBI group and the expression of p-JAK2 and p-STAT3 increased.And the most significant increase occurred at 7 days after injury [number of NSCs:31.2 ± 4.7 in the control group,111.4 ± 8.1 in the TBI group (P ＜ 0.01);p-JAK2:1.11 ± 0.09 in the control group,2.16 ± 1.01 in the TBI group (P ＜ 0.01);p-STAT3:1.05 ± 0.06 in the control group and 2.06 ± 0.09 in the TBI group (P ＜ 0.01)].The proliferation of NSCs in hippocampus of TBI group was consistent with the change of p-JAK2 and p-STAT3 expression.Seven days after injury,the expression levels of p-JAK2 and p-STAT3 and the proliferation ability of NSCs in the TBI + AG490 were significantly decreased [p-JAK2:2.18 ± 0.15 in the TBI + isotonic saline group,1.24 ±0.10 in the TBI + AG490 group (P ＜0.01);p-STAT3:2.21 ±0.12 in the TBI + isotonic saline group,1.25 ± 0.11 in the TBI + AG490 group (P ＜ 0.01);NSCs number:112.8 ± 8.6 in the TBI + isotonic saline group,75.5 ± 6.4 in the TBI + AG490 group (P ＜ 0.05)].Conclusions The proliferation of NSCs in hippocampus of rats increased after TBI,and the activity of JAK2/STAT3 signaling pathway also increased,following the same trend.JAK2 inhibitor AG490 can reduce the activity of JAK2/STAT3 signaling pathway and the proliferation of NSCs.This can provide reference for researches on TBI promoting nerve regeneration and function repair.