Beta‐mercaptoethanol supplementation of in vitro maturation medium does not influence nuclear and cytoplasmic maturation of equine oocytes

Abstract

In vitro embryo production in the horse is still not as efficient as in other species. Oxidative stress negatively affects oocyte and embryo culture. To attenuate/minimize the oxidative stress, antioxidants such as low-molecular thiol compounds can be added to culture media. Beta-mercaptoethanol (BME) has been shown to improve maturation and embryo development in different species. The aim of this study was to investigate whether the addition to maturation medium of BME at common (0.1 mM) and high (0.7 mM) concentration could improve oocyte maturation also in the horse. Equine oocytes recovered from slaughterhouse ovaries were used. Meiotic configuration after in vitro maturation (IVM) and early embryo production after intracytoplasmic sperm injection (ICSI) were considered as criteria for assessing nuclear and cytoplasmic maturation, respectively. A total of 1,076 oocytes were analysed over two experiments: 848 (control n = 293, BME 0.1 n = 270, BME 0.7 n = 285) were stained with Hoechst 33342 and examined for nuclear stage after 26 hr of IVM, and 228 MII oocytes were fertilized by ICSI (control n = 83, BME 0.1 n = 65, BME 0.7 n = 80). Cleavage rates were determined after 60 hr of culture. Unlike results obtained in other species, the addition of BME did not influence maturation rates (51.9% control vs 55.6% BME 0.1 mM and 55.1% BME 0.7 mM), nor cleavage rates after ICSI (38.6% vs 38.5% and 41.3%, respectively). In conclusion, the addition of BME at 0.1 and 0.7 mM to the maturation medium, in our culture conditions, has no effect on nuclear and cytoplasmic maturation of equine oocytes.

Overnight holding aids in selection of developmentally competent equine oocytes

“…In the present study, the overall maturation rate was 54.3%, similarly to other previous reports in the horse (Hall et al, 2013;Merlo et al, 2016Merlo et al, , 2018. Extending the IVM length (both 36 h and 44 h) increased nuclear maturation compared to direct 24-26 h IVM, but was similar to delayed (after 20 h holding) 24 h IVM.…”

Importance of Supplementation during In Vitro Production of Livestock Animals

“…Also, supplementation with β-mercaptoethanol during equine IVM did not affect maturation rates and cleavage rates after ICSI [127]. Although maturation rates of bovine were also not Theriogenology -Recent Advances in the Field increased, the quality and developmental competence of embryos originating from these oocytes were improved [128].…”

Fibroblast Growth Factor 10 Enhances Equine Oocyte Maturation and Blastocyst Formation In Vitro

“…Equine IVM rates vary between 30% to 60%, while IVF rates are around 4% to 33%, with only two foals having been born from both techniques [1,3,4]. In horses, the hormonal requirements during oocyte maturation remain unknown, and physiological patterns of follicle development and ovulation differ substantially from those in other species [3].…”