Environmental Oxygen Tension Regulates the Energy Metabolism and Self-Renewal of Human Embryonic Stem Cells

Abstract

Energy metabolism is intrinsic to cell viability but surprisingly has been little studied in human embryonic stem cells (hESCs). The current study aims to investigate the effect of environmental O2 tension on carbohydrate utilisation of hESCs. Highly pluripotent hESCs cultured at 5% O2 consumed significantly more glucose, less pyruvate and produced more lactate compared to those maintained at 20% O2. Moreover, hESCs cultured at atmospheric O2 levels expressed significantly less OCT4, SOX2 and NANOG than those maintained at 5% O2. To determine whether this difference in metabolism was a reflection of the pluripotent state, hESCs were cultured at 5% O2 in the absence of FGF2 for 16 hours leading to a significant reduction in the expression of SOX2. In addition, these cells consumed less glucose and produced significantly less lactate compared to those cultured in the presence of FGF2. hESCs maintained at 5% O2 were found to consume significantly less O2 than those cultured in the absence of FGF2, or at 20% O2. GLUT1 expression correlated with glucose consumption and using siRNA and chromatin immunoprecipitation was found to be directly regulated by hypoxia inducible factor (HIF)-2α at 5% O2. In conclusion, highly pluripotent cells associated with hypoxic culture consume low levels of O2, high levels of glucose and produce large amounts of lactate, while at atmospheric conditions glucose consumption and lactate production are reduced and there is an increase in oxidative metabolism. These data suggest that environmental O2 regulates energy metabolism and is intrinsic to the self-renewal of hESCs.

Distinct profiles of human embryonic stem cell metabolism and mitochondria identified by oxygen

“…In concordance with what we and others have reported, atmospheric oxygen induced a more oxidative profile in MEL2 hES cells when compared to cells maintained in physiological oxygen (Forristal et al 2013, Harvey et al 2014, Turner et al 2014. In this study we have extended these observations to show that mtDNA, ATP, mitochondrial mass and genetic regulators of mitochondria respond to changes in the extracellular oxygen concentration in MEL2 cells.…”

“…Physiological oxygen was shown to significantly alter MEL2 hES cell mitochondrial function and metabolite turnover. MEL2 is a well-characterized hES cell line that shows the expected hES cell metabolism in culture (Forristal et al 2013, Harvey et al 2014, Turner et al 2014. As such, these data confirm that oxygen is a regulator of hES cell mitochondrial activity.…”

“…Embryo culture in atmospheric oxygen (20%), compared to physiological concentrations, is associated with perturbed gene expression (Harvey et al 2004, Rinaudo et al 2006 changes to the proteome (Katz-Jaffe et al 2005), alterations in metabolic activity (Lane & Gardner 2005, Wale & Gardner 2012, Wale & Gardner 2013) and retarded development in several species, including the human (Thompson et al 1990, Meintjes et al 2009, Waldenströ m et al 2009). In previous reports, hES cell lines showed changes in metabolism (Forristal et al 2013, Harvey et al 2014, epigenetics (Petruzzelli et al 2014), transcription (Forsyth et al 2008, Westfall et al 2008, self-renewal capacity (Prasad et al 2009), clonal recovery , Hewitt et al 2006 and pluripotency (Ezashi et al 2005) in response to changes in environmental oxygen concentration. For example, culture of hES cells in physiological oxygen (w5%) results in increased glucose consumption and increased lactate production when compared to cells cultured in 20% oxygen (Forristal et al 2013, Harvey et al 2014, Turner et al 2014.…”

“…In previous reports, hES cell lines showed changes in metabolism (Forristal et al 2013, Harvey et al 2014, epigenetics (Petruzzelli et al 2014), transcription (Forsyth et al 2008, Westfall et al 2008, self-renewal capacity (Prasad et al 2009), clonal recovery , Hewitt et al 2006 and pluripotency (Ezashi et al 2005) in response to changes in environmental oxygen concentration. For example, culture of hES cells in physiological oxygen (w5%) results in increased glucose consumption and increased lactate production when compared to cells cultured in 20% oxygen (Forristal et al 2013, Harvey et al 2014, Turner et al 2014. Increased glucose consumption in physiological oxygen is accompanied by increased glycolytic gene expression (Westfall et al 2008, Harvey et al 2014.…”

Reappraisal of putative glyoxalase 1-deficient mouse and dicarbonyl stress on embryonic stem cellsin vitro

“…The latter was indicated by increased flux of formation of D-lactate, formed from metabolism of MG by the glyoxalase system [3]. We found increased consumption of glucose and net formation of L-lactate in 3% oxygen cultures reflecting increased anaerobic glycolysis, as found previously [55].…”