The Effect Of VPA On Hippocampal Neurogenesis In APP/PS1/Nestin-GFP Triple Transgenic Dementia Model Mice2

Objective: Study the dynamic changes of hippocampal neurogenesis in the different ages of Alzheimer's disease(AD) dementia model mice, and to observe the effect of valproic acid sodium salt(VPA), which is one of the clinical first-line antiepileptic drugs, on hippocampal neurogenesis in APP/PS1/Nestin-GFP triple transgenic AD model mice, and discuss their mechanisms. The results of this research will provide new exprimental basis for studying the pathogenesis and clinical treatment of AD.Methods: This study is divided into two parts. The first part: The APP/PS1 double transgenic heterozygous mice were crossed with the Nestin-GFP homozygous transgenic mice to yield APP/PS1/Nestin-GFP triple transgenic mice(AD), and Nestin-GFP transgenic mice(WT) after genetic identification. Mice at the age of 7 days, 1, 3, and 7 months were used in this study, 8- 10 mice in each age group, and both male and female mice were used. The Brd U labeling, immunofluorescence combined confocal laser technology and Golgi-Cox staining were used to observe the dynamic changes of hippocampal neurogenesis in the experimental mice.The second part: APP/PS1/Nestin-GFP triple transgenic mice at the age of 3 months and 7 months were chosen as the experimental objects. Within each age, 8- 10 mice were randomly divided into 2 groups: VPA-treated and saline-treated. 30 mg/kg·d of VPA and the same volume of saline were peritoneally injected into experimental mice for 4 weeks. After 4-week treatment, Morris water maze was conducted to observe the learning and memory ability of experimental mice; the Brd U labeling, immunofluorescence combined confocal laser technology, Golgi-Cox staining and western blot were used to observe the effect of VPA on the hippocampal neurogenesis and senile plaques in the experimental mice, and to discuss related mechanism.Results:1. The first part: Compared with the WT mice, the number of neural stem cells(Nestin-GFP) in AD mice was significantly decreased(P < 0.01), the proliferation of neural stem cells(Brd U) was inhibited(P < 0.05), the newborn neurons and astrocytes(DCX, GFAP) were decreased(P < 0.05), the number of mature neurons showed no obvious difference(P > 0.05), and the spine densities on neuron dendrites were decreased(P < 0.05).2. Morris water maze test: In the visible platform test, both in 3 months and 7 months old mice, there were no difference in escape latency and path length between VPA group and saline group(P > 0.05); In the hidden platform test, compared with saline group, VPA group at the age of 3 months had a significant shorter escape latency(P < 0.001) and lesser path length(P < 0.01) on the forth and fifth day; VPA group at the age of 7 months also had a significant shorter escape latency(P < 0.01) and lesser path length(P < 0.01) on the forth and fifth day; In the probe test, VPA group at the age of 3 months had much more platform-passing times than saline group(P < 0.01) within one minute; VPA group at the age of 7 months had more platform-passing times than saline group(P < 0.05) within one minute.3. The second part of morphological results: Compared with the saline groups, the number of neural stem cells(Nestin-GFP) in VPA groups were significantly increased(P < 0.05), and the proliferation of neural stem cells(Brd U) were significantly promoted(P < 0.05), the number of newborn neurons(DCX) were significantly increased(P < 0.01), and the number of astrocytes(GFAP) were increased(P < 0.05), the number of mature neurons showed no obvious difference(P > 0.05), the spine densities on neuron dendrites were increased(P < 0.05), the number and area of senile plaque decreased(P < 0.05).4. The second part of western blot: Compared with the saline groups, both in 3 months and 7 months old mice, total GSK-3? protein in VPA groups showed no obvious difference(P > 0.05), while p Ser9-GSK-3? protein was significantly increased in 3 months old mice(P < 0.05) and 7 months old mice(P < 0.001).Conclusion:1. In AD mice, hippocampal neurogenesis decreased with age;2. Compared with normal mice, hippocampal neurogenesis in the APP/PS1/Nestin-GFP triple transgenic mice was significantly decreased;3. VPA can improve the capability of spatial learning and memory of APP/PS1/Nestin-GFP triple transgenic mice;4. VPA treatment could significantly reduce the formation of senile plaques in APP/PS1/Nestin-GFP triple transgenic mice5. VPA treatment could improve the hippocampal neurogenesis in APP/PS1/Nestin-GFP triple transgenic mice;6. VPA exerts its therapeutic effects by inhibiting the activity of GSK-3?.