Effects of cysteamine, FSH and estradiol-17β on in vitro maturation of porcine oocytes

Abstract

Porcine cumulus-oocyte complexes (COCs) were cultured for 48 h with addition or absence of exogenous estradiol-17β (E 2; 1 μg/mL) in the maturation medium (mM199). The medium was supplemented with sodium pyruvate (0.1 mg/mL), 10% (v/v) FCS, various concentrations of FSH (0, 1 and 10 μg/mL) and with or without cysteamine (150 μM). When supplemented with E 2, cysteamine enhanced the rates of germinal vesicle breakdown (GVBD) and maturation to metaphase-II (M-II) in COCs cultured in the medium with O and 1 μ/mL FSH (P<0.05). Among COCs cultured with FSH, oocytes cultured with 1 μg/mL FSH and E 2 but without cysteamine showed the lowest rates of GVBD and M-II. The rates were, however, significantly increased when cysteamine was added to the same medium or by increasing FSH concentration to 10 μg/mL in the maturation medium. E 2 significantly inhibited the rates of GVBD and M-II in COCs cultured without FSH and cysteamine (a group of oocytes with spontaneous maturation). When COCs were cultured in TCM 199 with 1 or 10 μg/mL FSH, with or without E 2 (1 μg/mL) and fertilized in vitro, the rates of male pronucleus formation were not increased by increasing FSH concentration, but the addition of cysteamine to the maturation medium significantly enhanced the rates in the same FSH treatment. The results indicate that E 2 inhibits spontaneous GVBD and maturation to M-II of porcine oocytes and that a low concentration of FSH (1 μg/mL) is not sufficient to induce full nuclear maturation, compared with 10 μg/mL FSH, but that it can complete nuclear maturation with cysteamine and E 2. However, the cytoplasmic maturation is promoted only by the addition of cysteamine in the medium.