Reprogramming to pluripotency involves not only profound epigenetic and transcriptional change but necessitates the restructuring of metabolism. Worryingly, resultant induced pluripotent stem cells (iPSC) retain a metabolic memory of their somatic origin. While physiological oxygen, a known regulator of embryonic development and embryonic stem cell physiology, has been shown to increase the proportion of somatic cells reprogrammed to iPSC, whether this increased efficiency is accompanied by physiological alterations has not been examined. The aim of this study was, therefore, to determine whether oxygen concentration during reprogramming affected iPSC metabolic memory.
Neonatal human dermal fibroblasts (NHDF) were reprogrammed under either 20% or 5% oxygen in mTeSR1 medium. Resultant iPSC were maintained in their respective oxygen conditions, or challenged with the opposing oxygen concentration, and analysed for carbohydrate utilisation, mitochondrial metabolism, telomere length and transcriptional differences.
All iPSC lines retained aspects of somatic cell metabolic memory and failed to regulate carbohydrate metabolism, similar to their parental NHDF cells, in contrast to the metabolic response characteristic of embryonic stem cells. Significantly, basal and maximal respiration, along with mitochondrial ATP production, were only modulated in iPSC reprogrammed under physiological oxygen. Consistent with an observed reduction in telomere length, RNA-seq revealed transcriptomic instability in iPSC reprogrammed under atmospheric oxygen.
These data reveal oxygen availability during reprogramming perturbs subsequent transcriptional and metabolic profiles of iPSC. Physiological oxygen enables the acquisition of a more embryonic stem cell-like physiology, although metabolic reprogramming remains incomplete. As metabolism links nutrient availability with epigenetic regulation, these perturbations may plausibly persist in iPSC‑derived differentiated populations, and impact downstream application of iPSC for disease modelling, drug discovery and cell therapy.