Department of Orthopedics, The First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China.
Department of Orthopedics, The Fourth Hospital of China Medical University, Shenyang, Liaoning 110032, P.R. China.
Mol Med Rep. 2019 May;19(5):4091-4100. doi: 10.3892/mmr.2019.10069. Epub 2019 Mar 21.
Alzheimer's disease (AD) and osteoporosis (OP) are 2 common progressive age‑associated diseases, primarily affecting the elderly worldwide. Accumulating evidence has demonstrated that patients with AD are more likely to suffer from bone mass loss and even OP, but whether it is a pathological feature of AD or secondary to motor dysfunction remains poorly understood. The present study aimed to investigate whether amyloid‑β1‑42 (Aβ1‑42), the typical pathological product of AD, exhibited a negative effect on the proliferation of bone marrow mesenchymal stem cells (BMSCs) and the role of autophagy. The proliferation of BMSCs was measured using a Cell Counting Kit‑8 assay, cell cycle analysis and 5‑ethynyl‑2'‑deoxyuridine (EdU) staining. The autophagy‑associated proteins microtubule‑associated proteins 1A/1B light chain 3B and sequestosome 1 (p62) were evaluated by western blot analysis and autophagosomes were detected by transmission electron microscopy and immunofluorescence. The activity of the protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway was measured using western blot analysis, and the autophagy inducer rapamycin (RAPA), inhibitor 3‑methyladenine (3‑MA) and the AKT activator SC79 were also used to investigate the role of AKT/mTOR signaling pathway and autophagy in the proliferation of BMSCs. The results suggested that the proliferation of BMSCs treated with Aβ1‑42 was inhibited, with the autophagy level increasing following treatment with Aβ1‑42 in a dose‑dependent manner, while the AKT/mTOR signaling pathway participated in the regulation of the autophagy level. Activation of autophagy using RAPA inhibited the decrease in proliferation of BMSCs, while suppression of autophagy by 3‑MA and activation of the AKT/mTOR signaling pathway increased the decrease in proliferation of BMSCs caused by Aβ1‑42. It was concluded that Aβ1‑42, as an external stimulus, suppressed the proliferation of BMSCs directly and that the AKT/mTOR signaling pathway participated in the regulation of the level of autophagy. Concomitantly, autophagy may serve as a resistance mechanism in inhibiting the decreased proliferation of BMSCs treated with Aβ1‑42.
阿尔茨海默病（AD）和骨质疏松症（OP）是 2 种常见的进行性与年龄相关的疾病，主要影响全球老年人。越来越多的证据表明，AD 患者更有可能出现骨量丢失甚至 OP，但这是 AD 的病理特征还是继发于运动功能障碍仍不清楚。本研究旨在探讨 AD 的典型病理产物β淀粉样蛋白 1-42（Aβ1-42）是否对骨髓间充质干细胞（BMSCs）的增殖有负向作用以及自噬的作用。通过细胞计数试剂盒-8 测定法、细胞周期分析和 5-乙炔基-2'-脱氧尿苷（EdU）染色来测量 BMSCs 的增殖。通过 Western blot 分析评估自噬相关蛋白微管相关蛋白 1A/1B 轻链 3B 和自噬溶酶体相关蛋白 1（p62），通过透射电子显微镜和免疫荧光检测自噬体。通过 Western blot 分析测量蛋白激酶 B（AKT）/哺乳动物雷帕霉素靶蛋白（mTOR）信号通路的活性，并使用自噬诱导剂雷帕霉素（RAPA）、抑制剂 3-甲基腺嘌呤（3-MA）和 AKT 激活剂 SC79 来研究 AKT/mTOR 信号通路和自噬在 BMSCs 增殖中的作用。结果表明，Aβ1-42 处理后 BMSCs 的增殖受到抑制，且 Aβ1-42 呈剂量依赖性增加自噬水平，而 AKT/mTOR 信号通路参与了自噬水平的调节。使用 RAPA 激活自噬抑制了 BMSCs 增殖的下降，而 3-MA 抑制自噬和激活 AKT/mTOR 信号通路增加了 Aβ1-42 引起的 BMSCs 增殖下降。结论是，Aβ1-42 作为一种外部刺激物，直接抑制 BMSCs 的增殖，AKT/mTOR 信号通路参与了自噬水平的调节。同时，自噬可能作为一种抵抗机制，抑制 Aβ1-42 处理后 BMSCs 增殖的减少。
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