Sericin Supplementation Prior to and During In Vitro Maturation Mitigates H2O2-Induced Oxidative Stress in Bovine Oocytes

Oxidative stress during oocyte handling and in vitro maturation (IVM) can impair meiotic competence and compromise developmental potential in bovine oocytes. Thus, this study aimed to evaluate whether sericin supplementation during both prior to IVM and IVM phases could mitigate hydrogen peroxide (H₂O₂)-induced oxidative stress. All oocytes were cultured in tissue culture medium (TCM-199) at 38.5°C under 5% CO₂ and allocated into three groups: (1) the control group, without H₂O₂ induction and without sericin, (2) the oxidative stress group, exposed to 100-μM H₂O₂ for 1 h in collecting media and subsequently cultured in standard medium (-SC), and (3) the sericin-supplemented group, exposed to H₂O₂ under the same condition as -SC group but supplemented with 0.1% sericin in the collecting medium and 0.05% sericin in the maturation medium (+SC). After culture, two parameters were assessed: nuclear maturation to the metaphase II (MII) stage, evaluated by aceto-orcein staining, and malondialdehyde (MDA) levels, as an indicator of lipid peroxidation. The maturation rates were 70.36 ± 3.94%, 32.62 ± 5.89%, and 74.56 ± 6.05% for the control, -SC, and +SC groups, respectively, with significant differences observed between the -SC group and the control and +SC groups (p < 0.001). The corresponding MDA levels were 1.97 ± 0.14, 2.94 ± 0.28, and 1.09 ± 0.32 μM for the control, SC-, and SC + groups, respectively. The + SC group showed significantly lower MDA levels than both the control (p < 0.05) and the -SC groups (p < 0.001). These findings demonstrated that sericin supplementation attenuates oxidative stress-associated lipid peroxidation and preserves nuclear maturation in bovine oocytes under experimentally induced oxidative stress conditions, supporting its potential use as an antioxidant supplement during oocyte handling prior to IVM.

bovine oocyte; in vitro maturation; oxidative stress; sericin.