Steady-state level of epidermal growth factor (EGF) mRNA and effect of EGF on in vitro culture of caprine preantral follicles

Our aim was to verify the steady-state level of epidermal growth factor (EGF) mRNA in goat follicles at various developmental stages and to investigate the influence of EGF on the survival, antrum formation and growth of secondary follicles cultured for 6 days. Primordial, primary and secondary goat follicles and small and large antral follicles were obtained to quantify EGF mRNA by real-time reverse transcription with the polymerase chain reaction. The influence of EGF and the presence or absence of follicle-stimulating hormone (FSH) on the development of secondary follicles and on mRNA expression for EGF and FSH receptor (FSH-R) was determined after 6 days of culture. Survival, antrum formation and follicular diameter were evaluated every other day of culture. EGF mRNA levels in secondary follicles were significantly higher than those in primordial follicles, whereas in small and large antral follicles, EGF mRNA levels in cumulus–oocyte complexes (COCs) were significantly higher than in granulosa/theca cells. During culture, EGF in the presence or absence of FSH increased the follicular daily growth rate of secondary follicles when compared with that in enriched alpha minimal essential medium. FSH, EGF or both reduced EGF mRNA levels, whereas EGF reduced FSH-R mRNA levels after follicle culture for 6 days. Thus, EGF mRNA levels are higher in secondary follicles than in earlier stages, with both FSH and EGF promoting the growth of goat secondary follicles. EGF and/or FSH reduce EGF mRNA levels, whereas EGF decreases FSH-R mRNA levels, in cultured secondary follicles.