Syzygium aromaticum essential oil supplementation during in vitro bovine oocyte maturation improves parthenogenetic embryonic development.

The use of natural antioxidants in culture media can be an alternative to minimize the negative effects of oxidative stress produced by culture conditions. Essential oil from Syzygium aromaticum (EOSA) has therapeutic properties, including antioxidant activity in different cell types, and could be an interesting antioxidant agent during in vitro maturation (IVM) of bovine oocytes. Therefore, we sought to evaluate the antioxidant effect of the EOSA on bovine IVM, levels of reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), and subsequent preimplantation embryonic development. Then, viable oocytes were matured in vitro under five sets of conditions: EOSA0 (without antioxidants), EOSA10 (10 μg/mL of EOSA), EOSA15 (15 μg/mL of EOSA), EOSA20 (20 μg/mL of EOSA), and CYS (100 μM of cysteamine). These oocytes were used in three experiments. In the first experiment, oocytes were evaluated for IVM according to the expansion and viability of cumulus cells, the presence of the first polar body, and metaphase II. In the second experiment, denuded oocytes were evaluated for an antioxidant effect by labeling them with H2DCFDA (ROS levels) and MitoTracker Red (ΔΨm). In the third experiment, denuded matured oocytes were artificially activated and embryos were cultured for eight days. In the first experiment, no difference was observed in the IVM rates (P > 0.05). Nevertheless, EOSA15, EOSA20, and CYS improved the viability of cumulus cells after IVM, with EOSA20 viability higher than that of EOSA0 (P < 0.05). In the second experiment, although no difference has been observed for ROS levels (P > 0.05), oocytes derived from the EOSA15, EOSA20, and CYS groups showed significantly lower ΔΨm compared to the EOSA0 group. In the third experiment, although no difference in cleavage rates was observed, EOSA20 improved the blastocyst/total oocyte and blastocyst/cleavage oocyte rates when compared to EOSA0 (P < 0.05). Moreover, the rates of the EOSA20 group were similar to that of the CYS group (P > 0.05). Additionally, embryos derived from EOSA15 and EOSA20 showed a higher number of cells when compared to those derived from EOSA0 (P < 0.05). Therefore, EOSA, at 20 μg/mL, increased the viability of cumulus cells, promoted a reduction of in ΔΨm, and improved embryonic development in bovine oocytes. In conclusion, EOSA, added to the IVM medium, could be an interesting alternative for the reduction of damage caused by the oxidative stress in bovine oocytes.