The Metabolomic Profile of Spent Culture Media from Day-3 Human Embryos Cultured under Low Oxygen Tension

Abstract

Despite efforts made to improve the in vitro embryo culture conditions used during assisted reproduction procedures, human embryos must adapt to different in vitro oxygen concentrations and the new metabolic milieu provided by the diverse culture media used for such protocols. It has been shown that the embryo culture environment can affect not only cellular metabolism, but also gene expression in different species of mammalian embryos. Therefore we wanted to compare the metabolic footprint left by human cleavage-stage embryos under two types of oxygen atmospheric culture conditions (6% and 20% O2). The spent culture media from 39 transferred and implanted embryos from a total of 22 patients undergoing egg donation treatment was analyzed; 23 embryos came from 13 patients in the 6% oxygen concentration group, and 16 embryos from 9 patients were used in the 20% oxygen concentration group. The multivariate statistics we used in our analysis showed that human cleavage-stage embryos grown under both types of oxygen concentration left a similar metabolic fingerprint. We failed to observe any change in the net depletion or release of relevant analytes, such as glucose and especially fatty acids, by human cleavage-stage embryos under either type of culture condition. Therefore it seems that low oxygen tension during embryo culture does not alter the global metabolism of human cleavage-stage embryos.

Metabolic signature of spent culture media shows lipid metabolism as a determinant of pregnancy outcomes

“…The first objective with multivariate data analysis (PCA) was to reduce the dimensionality of the complex data set to facilitate visualization and potentially cluster groups of samples. By performing an exploratory analysis, it became clear that spent culture media can be a powerful non-invasive source of information, as also described in recent publications (de Los Santos et al, 2015;Gomez et al, 2021).…”

The influence of oxygen concentration during embryo culture on obstetric and neonatal outcomes: a secondary analysis of a randomized controlled trial

“…The underlying mechanism by which the use of atmospheric oxygen may be harmful for human embryos was inferred from animal studies. These studies revealed that low oxygen concentration during embryo culture could be beneficial to gene expression patterns, the proteome, energy metabolism or the methylome (Katz-Jaffe et al, 2005;Rinaudo et al, 2006;Wu and Zhang, 2010;de los Santos et al, 2015;Kaser et al, 2018). In the early stages, 20% oxygen was associated with an overall increase in amino acid turnover and pyruvate uptake by mouse embryos.…”

“…Some studies show clear evidence suggesting that global loss of DNA methylation of the paternal genome is attributable to Tetmediated oxidation. Tet proteins contribute to dynamic changes in DNA methylation, and gene expression studies will enhance our understanding of epigenetic regulation (Wu and Zhang, 2010;de los Santos et al, 2015;Kaser et al, 2018). There are few studies comparing reduced and atmospheric oxygen culture conditions in humans.…”

“…There are few studies comparing reduced and atmospheric oxygen culture conditions in humans. Studies looking at the metabolic fingerprint of good quality Day 3 human embryos showed that, at least in terms of net depletion or release of some relevant analytes such as glucose or fatty acids (Katz-Jaffe et al, 2005;de los Santos et al, 2015), no differences were found between low O 2 and normoxic embryo culture conditions. More recent data in human blastocysts have demonstrated that, at the blastocyst stage, even small variations of oxygen during culture (from 5% to 2%) impact the relative abundances of anabolic amino acids and metabolites involved in redox homeostasis by upregulating mucin 1, showing that oxygen influences embryo metabolism and may be important, at least at this more differentiated stage of development (Kaser et al, 2018).…”

Metabolite availability as a window to view the early embryo microenvironment in vivo

“…Indeed, in vitro studies empirically determined that 5–8% oxygen partial pressure during embryo culture improves embryo quality and pregnancy outcome when compared with atmospheric air (Bontekoe et al, ; de los Santos et al, ; Karagenc, Sertkaya, Ciray, Ulug, & Bahceci, ; Kasterstein et al, ; Meintjes et al, ; Nastri et al, ; Waldenstrom, Engstrom, Hellberg, & Nilsson, ; Wale & Gardner, ), suggesting that higher oxygen partial pressure in the oviduct may be embryo‐toxic due to a redox imbalance. Interestingly, a recent study reported that human cleavage‐stage embryos grown under 5% or 20% oxygen possessed similar metabolic fingerprints (de los Santos et al, ); however, the effects on global gene transcription in response to this environment are not clear. Further, higher in vivo oxygen partial pressures may delay key events, such as blastocyst formation or implantation, resulting in poor live‐birth rates.…”