The Correlation Of The Neural Stem Cells Proliferation With The Expression Of Toll-like Receptor 4 In Hippocampus In Mouse Model Of Traumatic Brain Injury

In accordance with current researches, traumatic brain injury(TBI) can make change of the expression of toll-like receptor 4(TLR4), however, neural stem cells(NSCs) that responded to the change remains unclear.Objective: In the present study, behavioral change in mouse model of traumatic brain injury, change of protein and m RNA of MYD88 and the relationship between the change and NSCs’ proliferation in hippocampus in the mouse model of TBI has been investigated using traumatic brain injury device when we make use of the inhibitor of TLR4.Methods: In our experiments, the mouse model of TBI had been investigated using a PCI-3000 device. Proliferative neural cells in hippocampus were labeled with the thymidine analog 5-bromo-2-deoxyuridine(Brd U). TLR4 was inhibited by an inhibitor called CLI-095 purchased from Invivo Gen, which was injected intraperitoneally to make TLR4 inhibited.We then made NSCs to be labeled by Nestin. We randomly divided adult male C57BL/6 mice into the following 3 groups, the solvent group, CLI-095 group, and sham group. CLI-095 was intraperitoneally injected into mice in CLI-095 group. We made real-time polymerase chain reaction(RT-PCR) to be as the way to detecte m RNA of MYD88 and we made use of the behavioral evaluation including the open field test, elevated plus maze and Morris water maze to detecte the change of behavior of mice 72 hours after TBI. Morphological observation on the expression of MYD88, Brd U and Nestin in the hippocampus was performed by immunofluorescence(IF). Western blotting was used to performe relative quantification of MYD88 expression at the protein level.Results: 1. It could be observed that the expression of MYD88 m RNA after CLI-095’s injection was lower than solvent was injected intraperitoneally(P<0.05) but results in the sham group was also lower than that in the former two groups(P<0.05). In the behavioral detections, CLI-095’s injection could make mice have better performance(P<0.05) but mice in the other two groups both had poor performance than the sham one(P<0.05). 2. The protein of MYD88 expressed higher at 72 hours after TBI but it decreased when CLI-095 was injected intraperitoneally at 6 hours after TBI and the following 2 days at the same time(P<0.05). However, more Brd U-labeled cells could be focused after the inhibitor’s injection intraperitoneally compared with mice which were injected with solvent(P<0.05). 3. The protein level of MYD88 increased at 72 hours after cerebral injury, but the expression of MYD88 decreased after CLI-095 was injected intraperitoneally at 6 hours after TBI and the following 2 days at the same time. While the number of Nestin-labeled cells become more after the inhibitor’s injection intraperitoneally compared with mice injected with solvent(P<0.05).Conclusion: 1. TBI could influence the behavior of mice while the changed m RNA of MYD88 could have lower expression by the inhibitor of TLR4. The inhibition of TLR4 played akey role in the regain of neural function after TBI and it may be one of the key factors in the repair of neural injury. This result could be sometimes considered to make sense on the recovery of neural function in mice from brain injury. 2. MYD88 and NSCs were in the opposite expression. It was to say that the inhibition of TLR4 could activate the proliferation of NSCs probably and then might make injured neural cells repaired in the following period of time. 3. The above indicated that hippocampal proliferating cells(suggestive of NSCs) expressed TLR4 and there was a potential association between inhibited TLR4 and the proliferation of NSCs after TBI. It was concluded that hippocampal TLR4 might play an essential role in endogenous neural regeneration after TBI.