Changes in DNA methylation and imprinting disorders in E9.5 mouse fetuses and placentas derived from vitrified eight‐cell embryos

Abstract

Vitrification is increasingly used in assisted reproductive technology (ART) laboratories worldwide, and potential vitrification‐induced risks require further exploration. The effect of vitrification on changes in DNA methylation and imprinting disorders was investigated in E9.5 mouse fetuses and placentas. Fetus and placental tissues were collected from the natural mating (nautural conception [NC]) group, in vitro culture (IVC) group and vitrified embryo transfer (VET) group. The fetal crown‐rump length at E9.5 in both the IVC (0.210 ± 0.059 mm) and VET (0.205 ± 0.048 mm) groups was significantly reduced compared with the NC group (0.288 ± 0.083 mm). The global methylation levels of fetuses were decreased in the IVC group compared with the NC group and it was increased after vitrification compared with IVC (p < 0.05), similar to what was observed in the NC group (p > 0.05). The changes could be attributed to the disorders of DNA methyltransferases and ten‐eleven translocations. In the IVC and VET fetuses, a majority of maternally expressed genes were upregulated, which repressed fetal growth. Furthermore, vitrification led to a change in the methylation level of KvDMR1, which resulted in the disturbance of gene imprinting. According to our results, vitrification could contribute to increased methylation compared with IVC and contributes to a gene imprinting disorder rather than recovery. Despite the routine use of embryo vitrification in clinical settings, the effect that this procedure may have on genomic imprinting deserves much greater attention.

DNA methylation, environmental exposures and early embryo development

“…Selective loss of DNA methylation of imprinted loci was observed in blastocysts subsequent to fertilization of vitrified bovine and mouse oocytes (Chen, Zhang et al, 2016;Cheng et al, 2014), whereas others found no effect on DNA methylation levels at the H19/IGF2 ICR loci at embryonic day 3 in human ICSI blastocysts following vitrification (Derakhshan-Horeh et al, 2016). When vitrification of mouse embryo at E2.5 (8-cell stage) was paired with IVC, transferred embryos revealed increased levels of global DNA methylation in both E9.5 fetus and placenta compared to IVC, but interestingly were similar to naturally mated derived samples (Ma et al, 2019). The long-term effect of vitrification was further observed in the fetus with increased DNA methylation levels at the imprinted KvDMR1 loci and significant gene expression increase of Dnmt1 and Dnmt3b compared to the IVC and natural mating groups.…”

Comparison of pregnancy outcomes in young patients following fresh versus frozen single blastocyst transfer:A retrospective study

“…In addition, In addition, genes related to foetal growth and development, at the genome-wide methylation level and the methylation level of speci c sites, were disordered in the fresh embryo transfer group, and various methylation levels in the freeze-thaw embryo transfer group similar to the natural pregnancy group. Some researchers [17] have provided an explanation for this phenomenon: freeze-thaw embryo transfer cannot reverse the effect of fresh embryo transfer on embryo gene methylation but will cause a new embryo methylation disorder. Hiuraand et al [18] conducted microarray gene chip analysis on human placenta obtained after freeze-thaw embryo transfer (n=64), fresh embryo transfer (n=16), and natural pregnancy (n=28).…”

Epigenetics in the Uterine Environment: How Maternal Diet and ART May Influence the Epigenome in the Offspring with Long-Term Health Consequences

“…ART treatment can interfere with epigenetic changes, particularly DNA methylation [ 146 ], starting from the preimplantation period in humans and animals [ 147 , 148 ], affecting early embryogenesis and offspring health [ 149 , 150 , 151 ]. The procedures implemented during ART treatment, such as ovarian stimulation using hormones, the in vitro maturation of oocytes and preimplantation embryos, and the use of ICSI and embryo cryopreservation, expose the embryo to environmental conditions that differ from those in spontaneous fertilization and embryogenesis, and which may alter the normal epigenetic mechanisms [ 149 , 152 ].…”