Autophagy alleviates the decrease in proliferation of amyloid β(1–42)-treated bone marrow mesenchymal stem cells via the AKT/mTOR signaling pathway

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-β(1–42) (Aβ(1–42)), 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 Aβ(1–42) was inhibited, with the autophagy level increasing following treatment with Aβ(1–42) 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 Aβ(1–42). It was concluded that Aβ(1–42), 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 Aβ(1–42).