Synergetic effects of epidermal growth factor and estradiol on cytoplasmic maturation of porcine oocytes

This study was conducted to examine the effect of epidermal growth factor (EGF) and 17beta-estradiol (E-2) on nuclear and cytoplasmic (male pronuclear formation and early embryo development) maturation of porcine oocytes. Oocytes were aspirated from antral follicles and cultured in modified TCM-199 medium supplemented with 0.57 mM cysteine, 10 IU/ml eCG, 10 IU/ml hCG, with or without EGF and/or E-2. In vitro fertilisation of matured oocytes was performed in a modified Tris-buffered medium (mTBM) with frozen-thawed ejaculated spermatozoa. Oocytes were transferred to NCSU-23 supplemented with 0.4% bovine serum albumin at 6 h after in vitro fertilisation. Significantly higher (p < 0.05) rates of nuclear maturation, pronuclear formation and cleavage (91.7%, 65.2% and 37.3% respectively) were observed when oocytes were cultured in the medium containing both EGF (10 ng/ml) and E-2 (1 mug/ml) than in the medium supplemented with either EGF or E, or without both, Intracellular glutathione concentration in the oocytes cultured in the medium containing both E-2 and EGF was also significantly higher (12.1 pmol per oocyte) than that of oocytes cultured in the medium with E-2 or EGF alone or without both. These findings suggested that EGF and E-2 have a synergestic effect on both nuclear and cytoplasmic maturation of porcine oocytes.