Transporting bovine oocytes in a medium supplemented with different macromolecules and antioxidants: Effects on nuclear and cytoplasmic maturation and embryonic development in vitro

Abstract

We investigated whether supplementing the medium used to transport bovine oocytes with different macromolecules [foetal calf serum (FCS) or bovine serum albumin (BSA)] or a mixture of antioxidants (cysteine, cysteamine and catalase) affects their nuclear and cytoplasmic maturation and thereby affects their subsequent embryonic development and cryotolerance. Oocytes were transported for 6 hr in a portable incubator and then subjected to standard in vitro maturation (IVM) for 18 hr. The oocytes in the control groups were cultured (standard IVM) for 24 hr in medium containing 10% FCS (Control FCS) or 10% FCS and the antioxidant mixture (Control FCS+Antiox). The intracellular concentrations of reactive oxygen species (ROS) at the end of IVM period were lower in the oocytes subjected to simulated transport in the presence of a macromolecular supplement or the antioxidant mixture than that of the control group (FCS: 0.62 and BSA: 0.66 vs. Control FCS: 1.00, p < .05; and Transp: 0.58 and Transp Antiox: 0.70 vs. Control FCS: 1.00, p < .05). After IVM, the mitochondrial membrane potentials of the transported oocytes were lower than those of the non-transported oocytes (FCS: 0.41 and BSA: 0.57 vs. Control FCS: 1.00, p < .05; and Transp: 0.48 and Transp Antiox: 0.51 vs. Control FCS: 1.00 and Control Antiox: 0.84, p < .05). The blastocyst formation rates (36.9% average) and the re-expansion rates of vitrified-warmed blastocysts (53%, average) were unaffected (p > .05) by the treatments. In conclusion, supplementing the medium in which bovine oocytes are transported with antioxidants or different macromolecules did not affect their in vitro production of embryos or their cryotolerance.

Antioxidant Nobiletin Enhances Oocyte Maturation and Subsequent Embryo Development and Quality

“…This pattern of distribution is similar to that described for bovine oocytes in other studies, which demonstrated that mitochondrial reorganization is necessary for cytoplasmic maturation, rearrangement of the cytoskeleton and developmental capacity after IVF [ 31 , 33 , 34 ]. Another important function of mitochondria is to synthesize adenosine triphosphate (ATP) through β-oxidation and this process involves the electron transport chain [ 4 ]. However, electrons may be lost during this process and could be bond to O 2 , resulting in the production of ROS that decreases the developmental competence of the oocyte [ 35 ].…”

“…Nevertheless, IVP of cattle embryos still has limitations, considering that not all the oocytes have the ability to develop into a viable embryo after IVM [ 2 ], as the culture systems decrease the quality of these gametes [ 3 ]. One of the causes is the increase in the production of reactive oxygen species (ROS) caused by the oxygen tension at which IVM is performed [ 4 ]. Under normal conditions, the cell produces a ROS level that acts beneficially for tissue regeneration, intracellular redox regulation, and embryogenesis, but an excess of ROS can oxidize cellular molecules, such as lipids, carbohydrates, amino acids, and nucleic acids, modifying their functions and compromising cellular viability by producing lipid peroxidation, mitochondrial damage, and apoptosis [ 4 ].…”

“…One of the causes is the increase in the production of reactive oxygen species (ROS) caused by the oxygen tension at which IVM is performed [ 4 ]. Under normal conditions, the cell produces a ROS level that acts beneficially for tissue regeneration, intracellular redox regulation, and embryogenesis, but an excess of ROS can oxidize cellular molecules, such as lipids, carbohydrates, amino acids, and nucleic acids, modifying their functions and compromising cellular viability by producing lipid peroxidation, mitochondrial damage, and apoptosis [ 4 ]. The strategy to avoid the harmful effects caused by an excess of ROS is the use of a wide variety of antioxidants during IVM, such as Vitamin C that protects cells against ROS and acts as an inhibitor of lipid peroxidation [ 5 ], cysteamine, which increases intracellular glutathione (GSH) content that protects cells from the deleterious effects of oxidative stress [ 6 ] and catalase, which reduces the intracellular concentrations of ROS during IVM and the percentage of apoptotic cells [ 3 ].…”

Efficiency of different incubation systems for the in vitro production of bovine embryos

“…Apparently, the portable incubation system used in our study (with a controlled gaseous atmospheric tension) was efficient in avoiding these deleterious effects, because the oocyte maturation rate and ROS levels were similar to the other groups. Ambrogi et al (2017) also avoided these negative effects when the transport-maturation medium was supplemented with an antioxidant mixture.…”

Delaying meiotic resumption during transportation of bovine cumulus–oocyte complexes: effects on development, apoptosis and caspases activity of in vitro-produced embryos

“…Interestingly, it was observed that although supplementation of IVM medium with BSA had retarded the meiosis resumption of oocytes cultured throughout the period within the incubator (Contr Lab BSA group), it was accelerated when oocytes were cultured in the presence of BSA during 6 h of simulated transport (Contr Transp BSA group). According to Ambrogi et al (2017), transportation of oocytes in incubators with an uncontrolled gaseous atmospheric tension can lead to alterations in the pH of the medium and increase the activity of oxidases, culminating in increased ROS production (Guérin et al, 2001;Guemra et al, 2014). Previous reports have demonstrated that H 2 O 2 acts as a signalling molecule that modulates various aspects of oocyte physiology, including the blockage and resumption of meiosis (Combelles et al, 2009;Pandey et al, 2010).…”