Melatonin Improves the Quality of In Vitro Produced (IVP) Bovine Embryos: Implications for Blastocyst Development, Cryotolerance, and Modifications of Relevant Gene Expression

Abstract

To evaluate the potential effects of melatonin on the kinetics of embryo development and quality of blastocyst during the process of in vitro bovine embryo culture. Bovine cumulus–oocyte complexes (COCs) were fertilized after in vitro maturation. The presumed zygotes were cultured in in vitro culture medium supplemented with or without 10−7 M melatonin. The cleavage rate, 8-cell rate and blastocyst rate were examined to identify the kinetics of embryo development. The hatched blastocyst rate, mortality rate after thawing and the relevant transcript abundance were measured to evaluate the quality of blastocyst. The results showed that melatonin significantly promoted the cleavage rate and 8-cell embryo yield of in vitro produced bovine embryo. In addition, significantly more blastocysts were observed by Day 7 of embryo culture at the presence of melatonin. These results indicated that melatonin accelerated the development of in vitro produced bovine embryos. Following vitrification at Day 7 of embryo culture, melatonin (10−7 M) significantly increased the hatched blastocyst rate from 24 h to 72 h and decreased the mortality rate from 48 h to 72 h after thawing. The presence of melatonin during the embryo culture resulted in a significant increase in the gene expressions of DNMT3A, OCC, CDH1 and decrease in that of AQP3 after thawing. In conclusion, melatonin not only promoted blastocyst yield and accelerated in vitro bovine embryo development, but also improved the quality of blastocysts which was indexed by an elevated cryotolerance and the up-regulated expressions of developmentally important genes.

Melatonin protects in vitro matured porcine oocytes from toxicity of Aflatoxin B1

“…Our data indicates that a relative high level of melatonin (10 −3 mol/L) significantly reversed the reduction in blastocyst quality caused by AFB1 exposure during oocyte maturation. Similarly, previous studies also proved that melatonin has an essential function in improving embryo quality under normal IVM‐IVF conditions or stressed conditions …”

Knock-Out Serum Replacement and Melatonin Effects on Germ Cell Differentiation in Murine Testicular Explant Cultures

“…Based on promising results for melatonin in previous work using testicular tissue of CD-1 mice4 and rats,20 we hypothesized its positive effect in our murine testicular organ cultures. The concentration of melatonin we used was 10 −7  M, which was used previously to produce the antioxidant effect 4,26,36,37…”

Baicalin increases developmental competence of mouse embryos <i>in vitro</i> by inhibiting cellular apoptosis and modulating <i>HSP70</i> and DNMT expression

“…Previous studies have shown that the embryo quality and viability is mainly affected by in vitro culture conditions [4, 22,23,24], and high-quality embryos can be achieved through modifying culture conditions [24, 25]. Baicalin has been reported to promote embryo implantation and maintain pregnancy in mice [13].…”

“…Although the mechanism behind baicalin-induced up-regulation of Dnmt3a gene expression is unclear, higher Dnmt3a mRNA levels in mouse blastocyst than its early developmental stage to establish a new embryonic methylation pattern have been reported [47]. Moreover, the beneficial effects of melatonin on bovine embryo-quality have also been shown to be due to the increased DNMT3a gene expression [25]. Our study indicates that baicalin enhances developmental competence of mouse embryos in vitro via down-regulating Dnmt1 and up-regulating Dnmt3a gene expressions to improve DNA methylation.…”