Vitamin C Rescues in vitro Embryonic Development by Correcting Impaired Active DNA Demethylation

Abstract

During preimplantation development, a wave of genome-wide DNA demethylation occurs to acquire a hypomethylated genome of the blastocyst. As an essential epigenomic event, postfertilization DNA demethylation is critical to establish full developmental potential. Despite its importance, this process is prone to be disrupted due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF), and thus leading to epigenetic errors. However, since the first case of aberrant DNA demethylation reported in IVF embryos, its underlying mechanism remains unclear and the strategy for correcting this error remains unavailable in the past decade. Thus, understanding the mechanism responsible for DNA demethylation defects, may provide a potential approach for preventing or correcting IVF-associated complications. Herein, using mouse and bovine IVF embryos as the model, we reported that ten-eleven translocation (TET)-mediated active DNA demethylation, an important contributor to the postfertilization epigenome reprogramming, was impaired throughout preimplantation development. Focusing on modulation of TET dioxygenases, we found vitamin C and α-ketoglutarate, the well-established important co-factors for stimulating TET enzymatic activity, were synthesized in both embryos and the oviduct during preimplantation development. Accordingly, impaired active DNA demethylation can be corrected by incubation of IVF embryos with vitamin C, and thus improving their lineage differentiation and developmental potential. Together, our data not only provides a promising approach for preventing or correcting IVF-associated epigenetic errors, but also highlights the critical role of small molecules or metabolites from maternal paracrine in finetuning embryonic epigenomic reprogramming during early development.

Glutathione safeguards TET‐dependent DNA demethylation and is critical for the acquisition of totipotency and pluripotency during preimplantation development

“…In line with this notion, DNA methylation and gene expression patterns of IVF embryos have been partially corrected by supplementing oviductal fluid into culture medium. Correspondingly, our previous study has found that AsA, enriched in both embryos and oviduct environment, is involved in DNA demethylation in preimplantation embryos 14 . Similarly, the present study identifies that GSH, which is also synthesized by both the embryo and oviduct, maintains redox homeostasis and safeguards DNA demethylation in preimplantation.…”

“…Correspondingly, our previous study has found that AsA, enriched in both embryos and oviduct environment, is involved in DNA demethylation in preimplantation embryos. 14 Similarly, the present study identifies that GSH, which is also synthesized by both the embryo and oviduct, maintains redox homeostasis and safeguards DNA demethylation in preimplantation. The important role of paracrine GSH in developmental potential was further supported by the result that exogenous that exogenous supplementation of GSH significantly prompted ICM specification via facilitating 5hmC formation.…”

“…To investigate the influence of GSH on the development of bovine pre‐implantation embryos, we incorporated GSH into the culture medium during the zygotic stage following IVF. Preparation of bovine blastocysts were collected according to the previously described protocol 14 …”

“…The IVF and embryo transfer procedures were carried out according to the previously described protocol. 14 Briefly, cumulus-oocyte complexes were equilibrated in the modified human tubal fluid for 30 min, after which capacitated sperm was added. After 3-4 h of fertilization, the zygotes were washed and cultured in KSOM+AA medium at 37°C in a 5% CO 2 environment until they reached the 2-cell or blastocyst stage.…”

WNT Co-Receptor LRP6 Is Critical for Zygotic Genome Activation and Embryonic Developmental Potential by Interacting with Oviductal Paracrine Ligand WNT2

“…To decipher the receptor–ligand repertoire of embryonic WNT signaling, we first analyzed the dynamic expression patterns of WNT signaling receptors in in vivo conceived embryos and their temporally corresponding oviduct/uterus, using our previously published RNA-seq data [ 16 ]. Several WNT signaling receptors, such as Fzd5 , Fzd6 , etc., showed higher expression levels in oviduct/uterus, indicating that these receptors may function in the oviduct/uterus ( Figure 1 A).…”