Coordinated Changes of Mitochondrial Biogenesis and Antioxidant Enzymes During Osteogenic Differentiation of Human Mesenchymal Stem Cells

Abstract

The multidifferentiation ability of mesenchymal stem cells holds great promise for cell therapy. Numerous studies have focused on the establishment of differentiation protocols, whereas little attention has been paid to the metabolic changes during the differentiation process. Mitochondria, the powerhouse of mammalian cells, vary in their number and function in different cell types with different energy demands, but how these variations are associated with cell differentiation remains elusive. In this study, we investigated the changes of mitochondrial biogenesis and bioenergetic function using human mesenchymal stem cells (hMSCs) because of their well-defined differentiation potentials. Upon osteogenic induction, the copy number of mitochondrial DNA, protein subunits of the respiratory enzymes, oxygen consumption rate, and intracellular ATP content were increased, indicating the upregulation of aerobic mitochondrial metabolism. On the other hand, undifferentiated hMSCs showed higher levels of glycolytic enzymes and lactate production rate, suggesting that hMSCs rely more on glycolysis for energy supply in comparison with hMSC-differentiated osteoblasts. In addition, we observed a dramatic decrease of intracellular reactive oxygen species (ROS) as a consequence of upregulation of two antioxidant enzymes, manganesedependent superoxide dismutase and catalase. Finally, we found that exogenous H 2 O 2 and mitochondrial inhibitors could retard the osteogenic differentiation. These findings suggested an energy production transition from glycolysis to oxidative phosphorylation in hMSCs upon osteogenic induction. Meanwhile, antioxidant enzymes were concurrently upregulated to prevent the accumulation of intracellular ROS. Together, our findings suggest that coordinated regulation of mitochondrial biogenesis and antioxidant enzymes occurs synergistically during osteogenic differentiation of hMSCs. STEM CELLS 2008;26:960 -968 Disclosure of potential conflicts of interest is found at the end of this article.

Mitochondrial Function and Energy Metabolism in Umbilical Cord Blood- and Bone Marrow-Derived Mesenchymal Stem Cells

“…Since the mitochondrial-tocytoplasm area ratio also increased after 14-days osteoinduction in all hMSC types and the increase was most striking in BMMSC > 50, we believe that the higher mitochondrial-to-cytoplasm area ratio in UCBMSC and BMMSC < 18 compared with BMMSC > 50 could indicate different overall maturation levels of these cells. Chen et al [29], however, have not noticed dramatic changes in mitochondrial mass during differentiation measured by nonyl acridine orange, a finding that is at variance with our results, as mitochondrial mass should increase as mitochondrial-to-cytoplasm area ratio increases. On the other hand, Chen et al [29] used BMMSC that were expanded in presence of growth factors (fibroblast growth factor and EGF), which may drive the cells toward a more mature progenitor state with already increased mitochondrial mass.…”

“…Chen et al [29], however, have not noticed dramatic changes in mitochondrial mass during differentiation measured by nonyl acridine orange, a finding that is at variance with our results, as mitochondrial mass should increase as mitochondrial-to-cytoplasm area ratio increases. On the other hand, Chen et al [29] used BMMSC that were expanded in presence of growth factors (fibroblast growth factor and EGF), which may drive the cells toward a more mature progenitor state with already increased mitochondrial mass. Our results suggest that the increase in mitochondrial-to-cytoplasm area ratio is one of the first observed indicators in osteogenic induction which is in line with recent work on murine cells [43].…”

“…Recently, more attention has been focused on mitochondria and cellular bioenergetics of stem cells, which has revealed their unique metabolic status [27][28][29]. It has been shown that mitochondrial activity or dormancy plays a major role in maintaining the undifferentiated state, whereas the proper activation and function of mitochondria is essential during the differentiation processes [29][30][31].…”

“…Recently, more attention has been focused on mitochondria and cellular bioenergetics of stem cells, which has revealed their unique metabolic status [27][28][29]. It has been shown that mitochondrial activity or dormancy plays a major role in maintaining the undifferentiated state, whereas the proper activation and function of mitochondria is essential during the differentiation processes [29][30][31]. In addition, mitochondrial reactive oxygen species (ROS) regulate the differentiation of several stem cell types; and recently, ROS have been shown to inhibit adhesion of hMSCs to the site of injury [32][33][34].…”

An active mitochondrial biogenesis occurs during dendritic cell differentiation

“…On the other hand, the key role of the mitochondrial SOD is illustrated by the lethal phenotype of mice lacking the matrix superoxide dismutase (Sod2) gene (Li et al, 1995). Finally, as described for osteogenic differentiation of human mesenchymal stem cells (Chen et al, 2008), our observations suggest that during DC differentiation a coordinated regulation between mitochondrial biogenesis and anti-oxidant defence systems needs to be orchestrated in order to let ROS production trigger differentiation but, at the same time, prevent accumulation of ROS when aerobic mitochondrial metabolism becomes dominant.…”