Modulating Developmental Competence in Ovine Oocytes: Role of Sodium Hydrosulfide as an Exogenous Hydrogen Sulfide Donor in Conventional and Biphasic Maturation.

The developmental competence of oocytes is crucial for successful fertilization and embryonic development; however, optimizing this capacity remains challenging. Hydrogen sulfide (H2S), a gasotransmitter recognized for its cytoprotective and antioxidant properties, has the potential to enhance oocyte quality. This study investigated the effects of sodium hydrosulfide (NaHS), an exogenous H2S donor, on the developmental competence of ovine oocytes in both conventional (C-IVM) and biphasic in vitro maturation (Pre-IVM) systems. Immature ovine oocytes were cultured in C-IVM medium supplemented with increasing NaHS concentrations (0-10 mM) to determine the optimal concentration based on redox state, mitochondrial status, and developmental outcomes. Subsequently, the effects of NaHS during the Pre-IVM phase of the biphasic system were evaluated, focusing on meiotic arrest, cytoplasmic maturation, and developmental competence. The results revealed that 2.5 mM NaHS during C-IVM significantly improved oocyte quality by reducing reactive oxygen species (ROS) levels, increasing glutathione (GSH) content, and enhancing blastocyst rates. Furthermore, a 6-h exposure to 2.5 mM NaHS during Pre-IVM did not alter germinal vesicle (GV) rates and cyclic AMP levels but significantly decreased ROS levels and increased mitochondrial mass index at both 6 and 24 h. In the biphasic system, 2.5 mM NaHS notably elevated blastocyst rates. These findings suggest that NaHS could serve as a promising supplement to improve IVM efficiency and embryonic development, providing valuable insights for assisted reproductive technologies.