Bovine Follicular Fluid Contains Antagonist Activity for Cumulus Expansion Promoting Effect by Epidermal Growth Factor

Abstract

The present study was conducted to investigate the effects of bovine follicular fluid (bFF) fractions or epidermal growth factor (EGF) on cumulus cell expansion in bovine cumulus-oocyte complexes (COCs) in vitro. bFF derived from large follicles (15-20 mm) and its fractions (>100, 10-100 and <100 kDa) were added to the medium. Cumulus cell expansion was stimulated when COCs were incubated with the 10-100 and <100 kDa fractions or bFF; in contrast, the culture of COCs with the >100 kDa fraction resulted in the suppression of cumulus cell expansion. Although the >100 kDa fraction prohibited the expansion of cumulus cells in the medium with or without low concentration EGF, cumulus expansion was promoted when COCs were cultured with the >100 kDa fraction and high-concentration EGF. In conclusion, the results suggest that bFF contains promoting and inhibiting effect for expansion of cumulus cells in COCs in vitro. The inhibiting effect of bFF may act antagonistically against the effect of EGF for the event of expanding cumulus cells.