Oocyte in vitro maturation (IVM)
Ovaries were obtained from a local slaughterhouse and delivered to the laboratory within 2 hours. The ovaries were aspirated with a 18-gauge needle to obtain cumulus-oocyte complexes (COCs) from follicles with 2–8 mm in diameter. The COCs with more than three layers of cumulus cells and evenly distributed cytoplasm were sorted in the study. For IVM, the COCs were cultured in chemically defined TCM-199 supplemented with 0.005 IU/mL FSH (Sigma–Aldrich, Cat. no. F2293), 1 μg/mL 17β-estradiol (Cat. no. E4389), 100 μM cysteamine (Sigma–Aldrich, Cat. no. M6500), and 10% FBS (Gibco, Cat. no. GIB-16000–044) in a humidified atmosphere of 5% CO2 at 38.5 °C.