Effect of growth factors, EGF and IGF-I, and estradiol on in vitro maturation of sheep oocytes

The objective of these experiments was to determine the effect of exogenous addition of insulin-like growth factor-I (IGF-I, 100 ng/mL), epidermal gro wth factor (EGF, 10 ng/mL) and estradiol (E2, 100 ng/mL) to the maturation medium of sheep oocytes on their subsequent development in vitro. Addition of IGF-I to the maturation medium did not improve nuclear or cytoplasmic ma turation of sheep oocytes at the concentration tested. However, EGF improve d significantly the resumption of meiosis (84% oocytes in metaphase II stag e after IVM vs. 59% in medium alone). Cleavage rate and blastocyst developm ent rates were improved (P<0.01) after addition of EGF (60% and 29%, respec tively), as compared with maturation in TCM 199 alone (39% and 19%, respect ively), but remained lower than rates observed after maturation in complete medium containing follicular fluid (FF, 10%) and FSH (81% and 35%, respect ively). No additive effect of EGF over FSH was observed during these experi ments. Addition of FF to FSH containing maturation medium improved signific antly both cleavage (P<0.001) and blastocyst rates (P<0.05). Addition of E2 to the NM medium is not required when medium already contains FF. However, in defined conditions supplementation of maturation medium with E2 had a p ositive effect. These results suggest that EGF, FSH and E2 may play an impo rtant role in the nuclear and cytoplasmic maturation of sheep oocytes in vi tro. (C) 2000 by Elsevier Science Inc.