The role of DNA damage response in human embryonic stem cells exposed to atmospheric oxygen tension: Implications for embryo development and differentiation

Previous retrospective cohort studies have found that, compared with oxygen tension in the uterus and fallopian tubes (2 %-8 %), exposure of pre-implantation embryos to atmospheric oxygen tension (AtmO₂, 20 %) during assisted reproductive technology(ART) can affect embryo quality, pregnancy outcomes and offspring health. However, current research on the effects and mechanisms of AtmO₂ on the development of embryos and offspring is mainly limited to animal experiments. Human embryonic stem cells (hESCs) play a special and irreplaceable role in the study of early human embryonic development. In this study, we used hESCs as a model to elucidate the possible effects and mechanisms of AtmO₂ exposure on human embryonic development. We found that exposure to AtmO₂ can reduce cell viability, produce oxidative stress, increase DNA damage, initiate DNA repair, activate autophagy, and increase cell apoptosis. We also noticed that approximately 50 % of hESCs survived, adapted and proliferated through high expression of self-renewal and pluripotency regulatory factors, and affected embryoid body differentiation. These data indicate that hESCs experience oxidative stress, accumulation of DNA damage, and activate DNA damage response under the selective pressure of AtmO₂.Some hESCs undergo cell death, whereas other hESCs adapt and proliferate through increased expression of self-renewal genes. The current findings provide in vitro evidence that exposure to AtmO₂ during the early preimplantation stage negatively affects hESCs.