Hsu Shu-Han, Chen Chien-Tsun, Wei Yau-Huei
Department of Biochemistry and Molecular Biology, National Yang Ming University, Taipei, Taiwan.
Stem Cells. 2013 Dec;31(12):2779-88. doi: 10.1002/stem.1441.
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.
我们之前证明，代谢转换和线粒体激活是人间充质干细胞（hMSCs）成骨分化所必需的。然而，龛中的干细胞或移植到损伤组织中的干细胞经常会遇到缺氧应激，这会阻碍有氧代谢。因此，我们研究了氧张力（1% 与 21%）对 hMSCs 代谢和成骨分化的影响。我们发现，缺氧会损害成骨分化，碱性磷酸酶活性降低以及成骨标志物核心结合因子 a-1 和骨桥蛋白的表达减弱表明了这一点。此外，如呼吸酶表达减少和氧消耗率降低所示，分化诱导的线粒体激活受到损害。相反，糖酵解酶上调和乳酸生成增加表明无氧代谢增强，使细胞更多地依赖无氧糖酵解来供应能量。此外，给予 2-脱氧葡萄糖（一种糖酵解抑制剂）而非抗霉素 A（一种呼吸抑制剂）可显著降低在缺氧条件下分化的 hMSCs 的细胞内 ATP 水平。用氯化钴（一种缺氧诱导因子-1α（HIF-1α）稳定剂）处理可重现缺氧的抑制作用，表明 HIF-1α 参与了 hMSCs 分化的受损过程。这些结果表明，缺氧会抑制代谢转换和线粒体功能，从而抑制 hMSCs 的成骨分化。
