Effects of varying β-caryophyllene levels on nuclear and cytoplasmic maturation in bovine oocytes

This study aimed to evaluate the effects of β-caryophyllene and its antioxidant potential at different concentrations during in vitro maturation (IVM) of bovine oocytes. Immature oocytes were divided into the groups: without antioxidant (control group); and groups supplemented with 100 µM cysteamine (CYS), 1 µM (β1), 5 µM (β5), and 10 µM (β10) β-caryophyllene. After 24h00 IVM, oocytes were analyzed for cumulus cell viability and expansion, presence of the first polar body (1PB), metaphase II (MII), cytoplasmic maturation, levels of reactive oxygen species (ROS), intracellular glutathione (GSH) and mitochondrial membrane potential (ΔΨm). Cumulus cell expansion rate was similar among all antioxidant groups (CYS [93.8%], β1 [91.8%], β5 [93.7%], and β10 [93.3%]), being higher than the control group (87.4%, P < 0.05). However, β-caryophyllene reduced cumulus cell viability compared to the control and CYS groups (P < 0.05). MII rates ranged from 79.6% to 90.0% (P < 0.05) with no difference between groups. β5 (93.8%) showed a higher 1PB rate compared to the other groups (P < 0.05). In terms of cytoplasmic maturation, β1 showed a higher number of oocytes with dispersed mitochondria (87.7%), similar to group CYS (80.6%) and superior to other treatments (P < 0.05). Additionally, β1 ensured a greater heterogeneous mitochondria distribution pattern (84.2%) when compared to the other groups (P < 0.05). Upon the evaluation of oxidative stress in arbitrary fluorescence units (AFU), CYS, β1, β5 and β10 reduced ROS levels (0.37 ± 0.2 vs. 0.42 ± 0.1 vs. 0.55 ± 0.1 vs. 0.48 ± 0.1), respectively, when compared to the control (1.00 ± 0.5), (P < 0.05). A similar response occurred in the GSH analysis, where the groups with antioxidants (CYS, β1, β5 and β10) presented higher levels (1.00 ± 0.19 vs. 0.96 ± 0.22 vs. 0.95 ± 0.46 vs. 1.01 ± 0.26), respectively, compared to the control (0.50 ± 0.17), (P < 0.05). However, only β5 (0.73 ± 0.40) was able to decrease ΔΨm compared to the control (P < 0.05). In summary, lower concentrations (1 and 5 µM) of β-caryophyllene ensure a reduction in oxidative stress and promote better conditions for bovine IVM.