We previously demonstrated that metabolic switch and mitochondrial activation are required for osteogenic differentiation of human mesenchymal stem cells (hMSCs). However, stem cells in niches or transplanted into injured tissues constantly encounter hypoxic stress that hinders aerobic metabolism. Therefore, we investigated the effects of
oxygen tension (1% vs. 21%) on metabolism and osteogenic differentiation of hMSCs. We found that
hypoxia impaired osteogenic differentiation as indicated by attenuation of
alkaline phosphatase activity and expression of osteogenic markers
core binding factor a-1 and
osteopontin. In addition, differentiation-induced mitochondrial activation was compromised as shown by the decrease in the expression of respiratory
enzymes and oxygen consumption rate. On the contrary, anaerobic metabolism was augmented as revealed by the upregulation of glycolytic
enzymes and increase of
lactate production, rendering the cells to rely more on anaerobic glycolysis for energy supply. Moreover, administration of
2-deoxyglucose (a glycolytic inhibitor) but not
antimycin A (a respiratory inhibitor) significantly decreased intracellular
ATP levels of hMSCs differentiating under
hypoxia. Treatment with
cobalt chloride, a
hypoxia-inducible factor-1α (HIF-1α) stabilizer, recapitulated the inhibitory effects of
hypoxia, suggesting that HIF-1α is involved in the compromise of hMSCs differentiation. These results suggest that
hypoxia inhibits metabolic switch and mitochondrial function and therefore suppresses osteogenic differentiation of hMSCs.