| Summary: | 碩士 === 國立陽明大學 === 生化暨分子生物研究所 === 97 === Previous studies of our lab revealed that mitochondrial metabolism is activated during osteogenic differentiation of human mesenchymal stem cells (hMSCs). In this study, we investigated the effects of oxygen concentration (1% vs. 21% O2) on mitochondrial metabolism during osteogenic differentiation of hMSCs. We found that hypoxia (1% O2) attenuated the activation of mitochondrial metabolism during osteogenic differentiation in several aspects including the decrease in protein levels of subunits of respiratory enzyme complexes, in mitochondrial membrane potential and oxygen consumption rate. However, mitochondrial mass was dramatically increased, suggesting a compensatory increase of mitochondria under hypoxia. On the contrary, anaerobic metabolism was up-regulated as revealed by the increase of glycolytic enzymes and the rate of lactate release. Due to the inability of differentiating osteoblasts to shift into aerobic metabolism under hypoxia, the up-regulation of antioxidant enzymes was less obvious and intracellular ROS levels were decreased more dramatically than that occurred under normoxia. Therefore, the osteogenic differentiation was compromised under hypoxia as indicated by the decrease of osteogenic markers such as cbfa-1, alkaline phosphatase (ALP) activity and the intracellular calcium content. Administration of cobalt chloride, a hypoxia-mimic compound, also suppressed ALP activity and oxygen consumption rate and increased lactate release rate. Moreover, PGC-1���z�nbut not cbfa-1, was slightly recovered after the treatment with echinomycin, a specific HIF-1�� inhibitor. These results suggest that activation of HIF-1�� was involved in the suppression of mitochondrial metabolism and inhibition of osteogenic differentiation of hMSCs. Taken together, our findings suggest that the metabolic shift is attenuated and osteogenic differentiation is compromised for osteogenesis of hMSCs under hypoxia.
|
|---|
