Objective: To explore the effects of transplanted neural stem cells (NSCs) on synaptogenesis in an Alzheimer' disease (AD) murine model and related mechanism.
Methods: Twenty 9-month-old APP/PS1 double transgenic mice were randomly divided into 2 groups. One group received NSCs transplantation (NSC group) in bilateral hippocampi while another group received an equal volume of 0.01 mol/L phosphate buffer saline (PBS group) as a negative control group. Ten wild-type mice were selected as the positive control group (WT group) without any treatment. After 8-week transplantation, the expressions of synaptophysin (SYN) and growth associated protein-43 (GAP-43) proteins in hippocampal areas were analyzed by immunofluorescence and Western blot. The number and structure of synapses in transplanted regions were observed by electron microscopy.
Results: (1) Immunofluorescence staining showed that NSC-induced neurons highly expressed SYN and GAP-43 at the protein levels; (2) the expression of SYN and GAP-43 significantly increased in the NSC group versus the PBS group (F = 58.367, P < 0.01; F = 75.296, P < 0.01). No difference existed in the SYN level between NSC and WT groups (P > 0.05). However, the GAP-43 expression was significantly higher than that of the WT group (P < 0.01); (3) ultrastructure showed that the number of synapses in the NSC group with normal morphology (12.1 ± 2.1) increased than that in the PBS group (6.5 ± 2.2) (F = 15.981, P < 0.01). No difference existed between NSC and WT groups (11.0 ± 1.4) (P > 0.05).
Conclusion: NSC-induced neurons increase the number of synapses by an up-regulation of synaptic proteins, SYN and GAP-43. Thus synaptogenesis may be a key factor in improving the symptom of AD mice.