Epidermal growth factor enhances oocyte maturation in pigs

Abstract

Epidermal Growth Factor (EGF) has been reported to stimulate nuclear maturation in porcine oocytes (Sommer et al., 1992). The objective of this experiment was to test the effect of EGF alone or in combination with gonadotropins and follicular shell coculture, on cytoplasmic maturation of oocytes in vitro. A preliminary experiment tested the effective dose of EGF for stimulation of oocyte nuclear maturation in our culture system. Nuclear maturation rates (MII%) of 67.2 ± 4.6, 81.1 ± 8.6, and 80.7 ± 5.1 for oocyte complexes cultured in the presence of 0.1, 1, and 10 ng/ml EGF, respectively, were significantly higher (P < 0.05) than for oocytes cultured in the absence of EGF (18.1 ± 9.4%). In the main experiment a 2 × 2 × 2 factorial random complete block design was used to examine the effect of EGF (1.0 ng/ml) alone or in combination with gonadotropins and follicular shell coculture on cytoplasmic maturation. Cytoplasmic maturation was evaluated by the ability of oocytes to decondense sperm nuclei after sperm penetration. EGF alone did not stimulate cytoplasmic maturation in oocytes in vitro (P > 0.05). However, EGF showed a positive interaction (P < 0.05) with gonadotropin treatment on male pronuclear formation. We conclude that EGF alone can stimulate nuclear maturation in pig oocytes, and EGF can interact with gonadotropins to enhance cytoplasmic maturation. A high level of cytoplasmic maturation of in vitro matured pig oocytes could be achieved using a combination of EGF, gonadotropin, and follicular shell supplementation to the culture environment.