Autophagy Plays a Protective Role in Tumor Necrosis Factor-α-Induced Apoptosis of Bone Marrow-Derived Mesenchymal Stem Cells

Bone marrow-derived mesenchymal stem cells (BMSCs) are being broadly investigated for treating numerous inflammatory diseases. However, the low survival rate of BMSCs during the transplantation process has limited their application. Autophagy can maintain cellular homeostasis and protect cells against environmental stresses. Tumor necrosis factor- (TNF-) is an important inflammatory cytokine that can induce both autophagy and apoptosis of BMSCs. However, the actual role of autophagy in TNF--induced apoptosis of BMSCs remains poorly understood. In the current study, BMSCs were treated with TNF-/cycloheximide (CHX), and cell death was examined by the Cell Counting Kit-8, Hoechst 33342 staining, and flow cytometric analysis as well as by the level of caspase-3 and caspase-8. Meanwhile, autophagic flux was examined by analyzing the level of microtubule-associated protein light chain 3 B (LC3B)-II and SQSTEM1/p62 and by examining the amount of green fluorescent protein-LC3B by fluorescence microscopy. Then, the cell death and autophagic flux of BMSCs were examined after pretreatment and cotreatment with 3-methyladenine (3-MA, autophagy inhibitor) or rapamycin (Rap, autophagy activator) together with TNF-/CHX. Moreover, BMSCs pretreated with lentiviruses encoding short hairpin RNA of beclin-1 (BECN1) were treated with TNF-/CHX, and then cell death and autophagic flux were detected. We showed that BMSCs treated with TNF-/CHX presented dramatically elevated autophagic flux and cell death. Furthermore, we showed that 3-MA and shBECN1 treatment accelerated TNF-/CHX-induced apoptosis, but that Rap treatment ameliorated cell death. Our results demonstrate that autophagy protects BMSCs against TNF--induced apoptosis. Enhancing the autophagy of BMSCs may elevate cellular survival in an inflammatory microenvironment.