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

Abstract

Oxygen is a powerful regulator of cell function and embryonic development. It has previously been determined that oxygen regulates human embryonic stem (hES) cell glycolytic and amino acid metabolism, but the effects on mitochondria are as yet unknown. Two hES cell lines (MEL1, MEL2) were analyzed to determine the role of 5% (physiological) and 20% (atmospheric) oxygen in regulating mitochondrial activity. In response to extended physiological oxygen culture, MEL2 hES cells displayed reduced mtDNA content, mitochondrial mass and expression of metabolic genes TFAM, NRF1, PPARa and MT-ND4. Furthermore, MEL2 hES cell glucose consumption, lactate production and amino acid turnover were elevated under physiological oxygen. In stark contrast, MEL1 hES cell amino acid and carbohydrate use and mitochondrial function were relatively unaltered in response to oxygen. Furthermore, differentiation kinetics were delayed in the MEL1 hES cell line following BMP4 treatment. Here we report the first incidence of metabolic dysfunction in a hES cell population, defined as a failure to respond to oxygen concentration through the modulation of metabolism, demonstrating that hES cells can be perturbed during culture despite exhibiting the defining characteristics of pluripotent cells. Collectively, these data reveal a central role for oxygen in the regulation of hES cell metabolism and mitochondrial function, whereby physiological oxygen promotes glucose flux and suppresses mitochondrial biogenesis and gene expression.

Energy Metabolism Regulates Stem Cell Pluripotency

“…Indeed, the importance of reduced oxygen tension has been examined across a number of stem cell populations (Mohyeldin et al, 2010), including a role in improving the acquisition (Yoshida et al, 2009) and maintenance of pluripotency (Ezashi et al, 2005;Forsyth et al, 2006;Prasad et al, 2009;Lengner et al, 2010;Mathieu et al, 2013;Christensen et al, 2015). In part these beneficial effects of physiologically relevant oxygen levels (2-5%) may be due to a reduction in mitochondrial function and oxygen utilization associated with elevated utilization of glucose via glycolysis and amino acid turnover (Forristal et al, 2013;Christensen et al, 2014;Turner et al, 2014;Lees et al, 2015Lees et al, , 2019Harvey et al, 2016b), although these metabolic changes can occur in the absence of changes in self-renewal (Harvey et al, 2016b). These effects of oxygen may be cell line dependent and may not occur in all iPSC lines, suggesting that metabolic fidelity may represent a marker for PSC and nuclear reprogramming quality (Lees et al, 2015;Harvey et al, 2018;Spyrou et al, 2019).…”

“…In part these beneficial effects of physiologically relevant oxygen levels (2-5%) may be due to a reduction in mitochondrial function and oxygen utilization associated with elevated utilization of glucose via glycolysis and amino acid turnover (Forristal et al, 2013;Christensen et al, 2014;Turner et al, 2014;Lees et al, 2015Lees et al, , 2019Harvey et al, 2016b), although these metabolic changes can occur in the absence of changes in self-renewal (Harvey et al, 2016b). These effects of oxygen may be cell line dependent and may not occur in all iPSC lines, suggesting that metabolic fidelity may represent a marker for PSC and nuclear reprogramming quality (Lees et al, 2015;Harvey et al, 2018;Spyrou et al, 2019). However, the effect of reduced oxygen tension on the transition between naïve and primed pluripotency, as well as the distinct metabolic phenotypes of these states have not been investigated.…”

The paradox of metabolism in quiescent stem cells

“…Human naïve pluripotent stem cells have higher glycolysis than primed pluripotent stem cells . Human ESCs depend on glycolysis and convert 70–80% of the glucose consumed to lactate . The higher glycolysis in naïve human PSCs results in more glucose carbons entering lactate, nucleotides and serine , and is associated with high nuclear N‐MYC and C‐MYC .…”

“…Human na€ ıve pluripotent stem cells use mainly aerobic glycolysis to produce ATP rather than mitochondrial oxidative phosphorylation [49-51]. Human na€ ıve pluripotent stem cells have higher glycolysis than primed pluripotent stem cells [54,55]. Human ESCs depend on glycolysis and convert 70-80% of the glucose consumed to lactate [54,55].…”

Mitochondrial and glycolytic remodeling during nascent neural differentiation of human pluripotent stem cells

“…Human pluripotent stem cells (hPSCs) and human induced pluripotent stem cells (hiPSCs) exhibit a heavy dependency on glycolysis, with 70-90% of the consumed glucose accounted for as lactate (Zhang et al, 2011;Zhou et al, 2012;Lees et al, 2015;Harvey et al, 2016). In contrast, mitochondrial oxidative phosphorylation (OxPhos) occurs at relatively low levels in hPSCs compared with their differentiated counterparts (Cho et al, 2006;Varum et al, 2011).…”