Liu Zhen, Wang Cunfu, Wang Xiao, Xu Shunliang
Department of Neural Medicine, Second Hospital of Shandong University, Jinan, China.
Cell Physiol Biochem. 2015;37(1):321-30. doi: 10.1159/000430356. Epub 2015 Aug 24.
BACKGROUND/AIMS: Alzheimer's disease (AD) is one of the most common dementias among aged people, and is clinically characterized by progressive memory loss, behavioral and learning dysfunction and cognitive deficits. So far, this is no cure for AD. A therapeutic effect of transplantation of mesenchymal stem cells (MSCs) into murine model of AD has been reported, but remains to be further improved. Brn-4 is a transcription factor that plays a critical role in neuronal development, whereas the effects of Brn-4 overexpression in transplanted MSCs on AD are unknown.
MSCs were isolated from mouse bone marrow and induced to overexpress antisense of miRNA-937 (as-miR-937) through adeno-associated virus (AAV)-mediated transduction, and purified by flow cytometry based on expression of a GFP co-transgene in the cells. The Brn-4 levels in mouse MSCs were examined in miR-937-modified MSCs by RT-qPCR and by Western blot. These miR-937-modified MSCs were then transplanted into an APP/PS1 transgenic AD model in mice. The effects of saline control, MSCs and asmiR-937 MSCs on AD mice were examined by deposition of amyloid-beta peptide aggregates (Aβ), social recognition test (SR), Plus-Maze Discriminative Avoidance Task (PM-DAT) and the levels of Brain-derived neurotrophic factor (BDNF) in the mouse brain.
MSCs expressed high levels of Brn-4 transcripts but low levels of Brn-4 protein. Poor protein vs mRNA levels of Brn-4 in MSCs appeared to result from the presence of high levels of miR-937 in MSCs. miR-937 inhibited translation of Brn-4 mRNA through binding to the 3'-UTR of the Brn-4 mRNA in MSCs. Expression of as-miR-937 significantly increased Brn-4 protein levels in MSCs. Transplantation of as-miR-937-expressing MSCs significantly reduced the deposition of Aβ, increased the levels of BDNF, and significantly improved the appearance in SR and PM-DAT in AD mice.
Overexpression of as-miR-937 in MSCs may substantially improve the therapeutic effects of MSCs on AD, possibly through augmenting Brn-4 levels in MSCs.
背景/目的：阿尔茨海默病（AD）是老年人中最常见的痴呆症之一，其临床特征为进行性记忆丧失、行为和学习功能障碍以及认知缺陷。迄今为止，AD尚无治愈方法。已有报道称将间充质干细胞（MSCs）移植到AD小鼠模型中有治疗效果，但仍有待进一步改善。Brn-4是一种在神经元发育中起关键作用的转录因子，而在移植的MSCs中过表达Brn-4对AD的影响尚不清楚。
从小鼠骨髓中分离出MSCs，并通过腺相关病毒（AAV）介导的转导诱导其过表达miRNA-937的反义链（as-miR-937），并基于细胞中共转基因GFP的表达通过流式细胞术进行纯化。通过RT-qPCR和蛋白质免疫印迹法检测miR-937修饰的MSCs中小鼠MSCs中Brn-4的水平。然后将这些miR-937修饰的MSCs移植到APP/PS1转基因AD小鼠模型中。通过淀粉样β肽聚集体（Aβ）沉积、社会识别试验（SR）、加迷宫辨别回避任务（PM-DAT）以及小鼠脑中脑源性神经营养因子（BDNF）的水平，检测生理盐水对照、MSCs和as-miR-937 MSCs对AD小鼠的影响。
MSCs表达高水平的Brn-4转录本，但Brn-4蛋白水平较低。MSCs中Brn-4蛋白与mRNA水平的差异似乎是由于MSCs中存在高水平的miR-937。miR-937通过与MSCs中Brn-4 mRNA的3'-UTR结合来抑制Brn-4 mRNA的翻译。as-miR-937的表达显著增加了MSCs中Brn-4蛋白水平。移植表达as-miR-937的MSCs可显著减少Aβ沉积，增加BDNF水平，并显著改善AD小鼠在SR和PM-DAT中的表现。
在MSCs中过表达as-miR-937可能会显著提高MSCs对AD的治疗效果，可能是通过提高MSCs中Brn-4的水平来实现的。
