What impact does oocyte vitrification have on epigenetics and gene expression?

Abstract

Children conceived by assisted reproductive technologies (ART) have a moderate risk for a number of adverse events and conditions. The question whether this additional risk is associated with specific procedures used in ART or whether it is related to the intrinsic biological factors associated with infertility remains unresolved. One of the main hypotheses is that laboratory procedures could have an effect on the epigenome of gametes and embryos. This suspicion is linked to the fact that ART procedures occur precisely during the period when there are major changes in the organization of the epigenome. Oocyte freezing protocols are generally considered safe; however, some evidence suggests that vitrification may be associated with modifications of the epigenetic marks. In this manuscript, after describing the main changes that occur during epigenetic reprogramming, we will provide current information regarding the impact of oocyte vitrification on epigenetic regulation and the consequences on gene expression, both in animals and humans. Overall, the literature suggests that epigenetic and transcriptomic profiles are sensitive to the stress induced by oocyte vitrification, and it also underlines the need to improve our knowledge in this field.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

“…It has been voiced that ICSI may differentiate the methylation patterns as evaluated in newborn blood [ 301 , 302 ]. Further to this, cryopreservation of oocytes or embryos has been considered as a cause of epigenetic modifications [ 303 , 304 ]. Regarding the embryo biopsy data on animal models epigenetic alterations are showcased [ 305 ].…”

Effect of Sperm Cryopreservation on miRNA Expression and Early Embryonic Development

“…Oocyte freezing, including “social egg freezing” and “medical egg freezing,” is an important technique ( Kool et al, 2018 ; Barberet et al, 2020 ). As clinical human samples were difficult to obtain, mouse oocyte miRNAs were analyzed in this study.…”

“…All oocytes were thawed by Vit Kit-Thaw (Easycheck, Nanjing, China), which include four bottles of thawing solution: DM-1, DM-2, DM-3, and WM. In short, oocytes were placed in 200 µl thawing solution (DM-1) at 37°C for 1 min and transferred to two drops of thawing solution (DM-2 and DM-3) in turn, each for 3 min, then were put into another thawing solution (WM) for 3 min and cultured later in incubators (5% CO 2 and 37°C) for 30 min to recover ( Barberet et al, 2020 ).…”

Fertilization, Oocyte Activation, Calcium Release and Epigenetic Remodelling: Lessons From Cancer Models

“…Methylation in oocytes is initiated in the cohort of oocytes recruited at the beginning of each ovarian cycle to undergo ovulation. Methylation proceeds with follicular growth from the primary to the preantral and antral stages when methylation is completed (Sendžikaitė and Kelsey, 2019;Barberet et al, 2020). The mammalian oocyte methylome is established in a transcription-dependent manner, leaving nontranscribing genes and intergenic areas hypomethylated, resulting in a bimodal and clustered methylome consisting of hyper-and hypomethylated domains (Sendžikaitė and Kelsey, 2019).…”