N-Acetylcysteine Promotes the Maturation of Sheep Oocytes and Embryo Development In Vitro

During the in vitro maturation process of oocytes, oxidative stress is commonly present, and excessive oxidative stress can affect oocyte maturation. Thus, adding antioxidants during maturation is an effective strategy for reducing oxidative stress. N-acetylcysteine (NAC), a derivative of cysteine, participates in glutathione (GSH) metabolism and stimulates glutathione synthesis. However, a clear understanding of the effect of NAC on sheep oocytes remains unknown. In this study, we investigated NAC's impact on the maturation of sheep oocytes, and the results revealed that the maturation rate, and subsequently the cleavage and blastocyst formation, were significantly enhanced by incubation with 1 mM NAC. The GSH and Ca²⁺ levels increased, and the cortical granules were significantly elevated, whereas the reactive oxygen species levels were significantly reduced in the 1 mM NAC-treated group. Additionally, the number of inner cell masses was significantly increased. The findings of this study support the hypothesis that NAC increases oocyte maturation rate by protecting them from oxidative stress damage. These discoveries provide a new approach for improving the efficiency of in vitro production of sheep embryos.