Involvement Of Wnt/?-catenin Signaling Mediated Hippocampal Neurogenesis In Sleep-deprivation And Traumatic Brain Injury Induced Cognitive Impairment

Sleep deprivation(SD)is defined as the decrease of sleeping due to various causes,including length and quality.Along with the increasing pace of life and work pressure,sleep deprivation is becoming a general social phenomenon in modern society.Sleep deprivation for a long time is reported associated with several disorders such like immune decreasing,endocrinal dysfunction,cardiovascular risk,emotional and cognitive impairment and so on.It has been reported associated with more complications,lower life quality and increasing mortality.Therefore,sleep medicine is paid more and more attention as compared with other subjects.Traumatic brain injury is also called Brain trauma,craniocerebral injury or head injury,defined as craniocerebral tissues injury due to external trauma,which are the major causes of death accident of children and middle aged or young people,disability and emotional dysfunction.And most Traumatic brain injury patients are persistently suffering with the post-traumatic stress disorder,cognitive impairment and disability,which bring family and society enormous economic burden.Wnt signaling pathway is a basic growth regulation pathway,in which classical Wnt/?-catenin signaling pathway plays an important role in the proliferation,differentiation,migration and apoptosis of neural stem cells.Wnt signaling is also a key driver of stem cells in most adult mammalian tissues,including cancer and early evolution of animals,and is also critical to developmental processes of cell proliferation,differentiation,and tissue patterns.Mutation in the components of Wnt signaling pathway often leads to a variety of growth-related pathological diseases and cancers.The interest in Wnt signaling has been steadily rising since the first member of the Wnt family was first discovered 35 years ago.A large number of animal and human studies have shown that hippocampal neonatal neurogenesis is closely related to cognitive and anxiety depression behaviors.However,whether sleep deprivation and traumatic brain injury affect hippocampal neuron occurrence,leading to cognitive and behavioral disorders,was still clear.Therefore,we designed the following experiment and investigate whether Wnt/?-catenin signaling pathway mediates the development of hippocampal neurons after sleep deprivation and traumatic brain injury.This study is divided into two parts as following.Part one: Involvement of Wnt/?-catenin signaling in sleep-deprivation induced cognitive impairmentThe effects and mechanism of hippocampal neurogenesis in sleep deprivation via Wnt/?-catenin signaling pathway.In this research,sleep deprivation animal models are made on healthy adult male wild-type C57BL/6 mice and those modified multiple platform method.We studied the hippocampal neuron occurrence by BrdU/DCX immunofluorescence double labeling,changes of wnt signaling by Wnt-signaling-reporter Topgal mice.And the Nestin/ROSA/EX3 mice in which Wnt signaling was activated in neural stem cells were used to study the effects of Wnt signaling on hippocampal neurogenesis and learning and memory in mice with sleep deprivation.The elevated cross maze and the open field were used to evaluate the anxiety,while rotating rod experiment is used to test the sensory motor coordination ability.And we use Morris water maze to assess the spatial learning and memory ability of mice.The result shows that SD mice don't behave anxious and represent decreasing ability of spatial learning and memory compared with control group.Double-immunostaining of BrdU/DCX showed that the hippocampal neurons of mice were significantly attenuated after 5d's SD.And the expression of the Wnt signaling reporter gene ?-gal is reduced in hippocampal neural stem cells.Activation of Wnt signaling in Nestin/ROSA/EX3 gene-modified mice significantly promoted hippocampal neuronal development and improved spatial memory in SD mice.Conclusion: Wnt/?-catenin signaling is involved in the reduction of hippocampal neurons induced by sleep deprivation in mice.Enhancing Wnt signaling can improve the neuronal activity and learning and memory ability of hippocampus in SD mice.Part two: Involvement of Wnt/?-catenin signaling in traumatic brain injury induced cognitive impairmentIn this part of the experiment,male wild-type C57BL/6 mice and Wnt signaling reporter Topgal mice were subjected to a controlled cortical impact model,and the anxiety changes were verified by elevated cross maze and open field experiments.Morris water maze verified the ability changes of mice learning and memory.The double-immunostaining of BrdU/DCX was used to observe the changes of hippocampal neurons in the mice after brain trauma.The cortex and hippocampus of the control side and the injured side were examined 5 days after the injury.As regard to the control cortical impact model of Topgal mice,the Wnt signal in neural stem cells was observed by Nestin/?-gal immunofluorescence double labeling.The results showed that after 5 days of brain trauma,the learning and memory ability of mice decreased significantly,and anxiety behavior occurred compared with sham-operated group mice.Double-immunostaining of BrdU/DCX showed that hippocampal neurons in mice decreased,and wnt signaling reporter ?-gal decreased in hippocampal neurons.Wnt/?-catenin signal pathway activator Lithium chloride therapy of CCI mice was used to observe the effect on Wnt signal and learning and memory ability.Conclusion: The hippocampal neurogenesis is decreased by brain injury via Wnt/?-catenin signal.Meanwhile,After Lithium chloride treatment,Wnt signal increased and learning and memory ability improved.