1H-MR spectroscopy in evaluating the effect of neural stem cell transplantation on Alzheimer's disease in an APP-PS1 transgenic mouse model

Objective To explore the value of 1H-MRS on the evaluation of Alzheimer's disease (AD) with neural stem cells (NSCs) transplantation in an APP-PS1 double transgenic (tg) AD mouse model.Methods NSCs from C57BL/6 mice were cultured and amplified.APP-PS1 tg mice (n =30) aged 12 months were used as the study group,and mild-type mice (n =15) were used as the control group.Animals in the study group were randomized into two subgroups,the AD mice in one subgroup received NSCs transplantation (NSCs group) and in another subgroup received phosphate buffer saline (PBS,PBS group)in bilateral hippocampal CA1.Animals in the control group were not treated.Using a 7.0 T high-fieldstrength MR imager,1H-MRS was performed before and 6 weeks after transplantation to measure the area under the peak of n-acetyl aspartate (NAA),glutamate (Glu),myo-inositol ( mI),choline (Cho) and creatine (Cr) in the hippocampal area,NAA/Cr,Glu/Cr,mI/Cr and Cho/Cr ratio were calculated and compared with histopathological results (including Nissl's staining and electron microscope examination).Comparisons among NSCs,PBS and control groups were conducted by one-way ANOVA.Results NSCs from C57BL/6 mice were cultured successfully. Before transplantation,the mean NAA/Cr,Glu/Cr and mI/Cr in NSCs,PBS and control groups were 0.89 ± 0.05,0.88 ± 0.04 and 1.15 ± 0.05,0.40 ± 0.03,0.39 ± 0.03 and 0.45 ± 0.05,0.67 ± 0.05,0.67 ± 0.05 and 0.52 ± 0.04,respectively,and differences were statistically significant (F =148.918,7.529,59.468,P ＜ 0.01 ). There were no significant differences in NAA/Cr,mI/Cr and Glu/Cr ratios between NSCs and PBS groups before transplantation (t =0.147,0.096,0.207,P ＞ 0.05 ),but the differences were significant compared with the control group (t =0.255,0.467,0.171 and t =0.269,0.527,0.151,P ＜0.05).Six weeks after transplantation,the mean NAA/Cr,Glu/Cr and mI/Cr in three groups were 1.13 ±0.07,0.86 ±0.05 and 1.14 ±0.05,0.45 ± 0.04,0.38 ± 0.02 and 0.44 ± 0.03,0.58 ± 0.04,0.67 ± 0.04 and 0.53 ± 0.04,respectively,and differences were statistically significant ( F =112.092,23.076,44.367,P ＜ 0.01 ).NAA/Cr and Glu/Cr ratios were increased and mI/Cr was decreased in NSCs group,and the difference was significant compared with PBS group at the same time point ( t =0.271,0.071,0.089,P ＜ 0.05 ).There were no significant differences in NAA/Cr and Glu/Cr ( t =0.013,0.012,P ＞ 0.05 ),but there was a significant difference in mI/Cr between NSCs and control groups ( t =0.046,P ＜ 0.05).There were no significant differences in Cho before and after transplantation among the three groups (P ＞ 0.05 ). Nissl's staining showed that the number of neurons in the hippocampal area increased more significantly in tg mice receiving NSCs than that without receiving NSCs.Electron microscopy showed that most hippocampal NSCs in NSCs group were morphologically normal with abundant organelles,while hippocampal NSCs in PBS group were swollen with sparse synapses.Conclusion 1H-MRS is able to display intracranial metabolite changes before and after NSCs in APP-PS1 double transgenic AD mice and has an applicable value in evaluating the therapeutic effect of NSCs on AD. Key words: Alzheimer disease; Stem cells; Magnetic resonance spectroscopy; Mice,transgenic