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 6hr in a portable incubator and then subjected to standard in vitro maturation (IVM) for 18hr. The oocytes in the control groups were cultured (standard IVM) for 24hr 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.