Advantages of vitrification preservation in assisted reproduction and potential influences on imprinted genes

Abstract

Cryopreservation has important application in assisted reproductive technology (ART). The vitrification technique has been widely used in the cryopreservation of oocytes and embryos, as a large number of clinical results and experimental studies have shown that vitrification can achieve a higher cell survival rate and preimplantation development rate and better pregnancy outcomes. Ovarian tissue vitrification is an alternative method to slow freezing that causes comparatively less damage to the original follicular DNA. At present, sperm preservation mainly adopts slow freezing or rapid freezing (LN2 vapor method), although the vitrification method can achieve higher sperm motility after warming. However, due to the use of high-concentration cryoprotectants and ultra-rapid cooling, vitrification may cause strong stress to gametes, embryos and tissue cells, resulting in potentially adverse effects. Imprinted genes are regulated by epigenetic modifications, including DNA methylation, and show single allele expression. Their accurate regulation and correct expression are very important for the placenta, fetal development and offspring health. Considering that genome imprinting is very sensitive to changes in the external environment, we comprehensively summarized the effect of cryopreservation—especially the vitrification method in ART—on imprinted genes. Animal studies have found that the vitrification of oocytes and embryos can have a significant impact on some imprinted genes and DNA methylation, but the few studies in humans have reported almost no influence, which need to be further explored. This review provides useful information for the safety assessment and further optimization of the current cryopreservation techniques in ART.

Study on the optimal time limit of frozen embryo resuscitation transfer and the effect of a long-term frozen embryo on pregnancy outcome

“…Theoretically, freezing embryos at -196°C in liquid nitrogen inhibits enzyme activity, and cell metabolism, making it possible for embryos to be frozen for a long time. Vitri cation is the preferred method in our study, ensuring consistent freezing techniques and a higher survival rate compared to slow freezing 20,21 .However, vitri cation, characterized by high cryoprotectants concentrations and ultrarapid cooling, can stress gametes, embryos, and histiocytes, potentially causing adverse effects 22 .…”

Vitrification of human blastocysts for couples undergoing assisted reproduction: an updated review

“…Indeed, it is worth mentioning that CPAs, especially when used at high concentrations, might cause toxicity in a time and temperature dependent manner (Fuller, 2004). With this concern, a few studies have been recently published, reporting some detrimental effects of the cryopreservation procedure on the epigenetic makeup of the embryo (Barberet et al, 2020;Chen et al, 2022). Also, reports suggest that cryopreservation may affect some cellular processes, such as cell functionality, protein expression, DNA integrity, cytoskeletal and nuclear structures (Kader et al, 2009;Kopeika et al, 2015;Verheijen et al, 2019;Palomares and Rodriguez, 2022).…”

“…Also, reports suggest that cryopreservation may affect some cellular processes, such as cell functionality, protein expression, DNA integrity, cytoskeletal and nuclear structures (Kader et al, 2009;Kopeika et al, 2015;Verheijen et al, 2019;Palomares and Rodriguez, 2022). As cryopreservation becomes more widely used, not only in ART but also in other fields, such as regenerative medicine or transplantation medicine, it is extremely important to examine potential genomic and epigenetic changes associated with current cryopreservation practices (Xu et al, 2010;Chen et al, 2022). A retrospective study reported that singleton pregnancies obtained from vitrified-warmed embryo replacement are associated with less obstetric and perinatal morbidity, and had reduced odds of low birth weight, preterm birth and small for gestational age (SGA) (Pelkonen and Koivunen, 2010;Wennerholm and Henningson, 2013;Ishihara et al, 2014;Maheshwari et al, 2018).…”

“…Importantly, ART procedures and cryopreservation coincide with the period of epigenome reprogramming, going from fertilization through to blastocyst formation. Modifications at this very delicate point might have repercussions during the future life of the conceived baby (Sendzikaite and Kelsey, 2019;Barberet et al, 2020;Chen et al, 2022). Thus, elements associated with vitrification protocols, such as the consequences of chilling, osmotic induced stress, and high concentrations of CPAs, might have an influence on epigenome integrity and transcript stability, with potential consequences for the offspring (Barberet et al, 2020;Chen et al, 2022).…”

“…Modifications at this very delicate point might have repercussions during the future life of the conceived baby (Sendzikaite and Kelsey, 2019;Barberet et al, 2020;Chen et al, 2022). Thus, elements associated with vitrification protocols, such as the consequences of chilling, osmotic induced stress, and high concentrations of CPAs, might have an influence on epigenome integrity and transcript stability, with potential consequences for the offspring (Barberet et al, 2020;Chen et al, 2022). Therefore, the main aim of this narrative review is to describe the value and efficacy of the vitrification programme in modern ART, and highlight the current state of knowledge about the impact that a high concentration of CPAs, used with the vitrification process, might have on epigenetic alteration and possible consequences for future generations.…”