Effect of Ethanol on Parthenogenetic Activation and α-Tocopherol Supplementation during In Vitro Maturation on Developmental Competence of Summer-Collected Bovine Oocytes

Abstract

The use of α-tocopherol during in vitro maturation (IVM) is an alternative to minimize the adverse effects of heat stress on oocyte competence. However, α-tocopherol is diluted in ethanol, which can induce oocyte parthenogenetic activation (PA). This study aimed to evaluate the role of ethanol concentration on PA and the effect of α-tocopherol supplementation during IVM on the developmental competence and the expression of key genes in blastocysts derived from summer-collected oocytes. All in vitro embryo production was conducted at 5% O2, 5% CO2 at 38.5 °C. Experiment 1: oocytes were cultured with or without 0.05% ethanol. As positive PA control matured oocytes were subjected to 3% or 7% ethanol for 7 min. Oocytes from all groups were placed in fertilization medium (22 h) and culture medium (9 days). Ethanol at 0.05% during IVM did not induce oocyte PA, however, 3% and 7% ethanol were effective parthenogenetic inductors. Experiment 2: oocytes were cultured in maturation medium supplemented with 0, 50, 100 and 200 μM α-tocopherol, diluted in 0.05% ethanol. After in vitro fertilization and embryo culture, we assessed blastocyst apoptotic index and the transcription of a panel of genes. The results showed that supplementation with 100 μM α-tocopherol reduced apoptotic index and increased the expression of SOD2. In conclusion, 100 μM α-tocopherol, diluted in 0.05% ethanol, can be used during IVM to embryonic quality.

Developmental Hurdles That Can Compromise Pregnancy during the First Month of Gestation in Cattle

“…The development of a female embryo without fertilization can be induced with various chemicals, and specifically those that interfere with cytoplasmic calcium availability and the activity of mitogen-activated protein kinases and serine-threonine protein kinases [73,74]. However, excessive ethanol in IVM medium (>3.0% v/v) and longer-than-normal IVM or combined IMV-IVF periods (e.g., >26 h or >44 h, respectively) will increase parthenogenesis rates [75][76][77].…”

Influence of calcium ionophore on the fertilization of bovine oocytes and their further embryonic development

“…However, the most promising method of artificial activation of oocytes is chemical stimulation. For this purpose, there are used ethanol (Fujinami et al, 2004;Báez et al, 2021), calcium ionophore A213187 (Hosseini et al, 2008;Xu et al, 2021), ionomycin (Méo et al, 2008;Jia et al, 2023), puromycin (De Sutter et al, 1992de Castro et al, 2022), strontium chloride (Kim et al, 2014;Fawzy et al, 2018), phorbol ester (Cuthbertson & Cobbold, 1985;Zhao et al, 2014), thimerosal (Kumbha et al, 2020), dehydroleukodine, ionomycin, anisomycin, cycloheximide, 6-dimethylaminopurine (Vichera et al, 2002, alone and in combinations. Addition of those compounds is mostly oriented at mobilization of intracellular calcium by depletion of its reserves, release of intracellular reserves of calcium and promotion of ingress of extracellular calcium ions inside the cell.…”