Epidermal Growth Factor Promote Mouse Oocyte Maturation In Vitro:Potential Role Of The C-erbB2 Protooncogene

Objective and Methods: The mechanism of oocyte maturation is not well-known.This research used mouse oocyte culture model to study the effect of both c-erbB₂ and epidermal growth factor (EGF) on mouse oocyte maturation in vitro,and the potential role of the c-erbB₂ protooncogene on EGF effect. Results:(1)c-erbB₂ASODN inhibited the rate of germinal versical breakdown(GVBD) and the first polar(PBâ… ) extrusion of denuded oocytes(DOs) in a dose-dependent and time-dependent way,and delayed their maturation time significantly.By 24h of culture,compare with the control group,the GVBD percentage of low,medium and high concentration c-erbB₂ASODNs group decreased 8.9, 26.6 and 37.0% respectively and the PBâ… extrusion percentage of medium and high concentration c-erbB₂ASODNs group decreased 13.1 and 22.7% .(2) EGF also stimulated meiosis of DO directly in a dose-dependent way. By 24h of culture,compare with the control group,the GVBD percentage of 1ng/ml EGF group,10ng/ml EGF group and 50ng/ml EGF group increased 19.0,27.0 and 20.6%, and the rate of PBâ… increased 13.0,21.9 and 14.4%. (3) c-erbB₂ASODN inhibited the effect of EGF on oocyte maturation in a time-dependent way.(4) In GVBD oocytes, RT-PCR showed that c-erbB2mRNA was expressed in oocytes and c-erbB2mRNA was the highest in EGF group,midst in EGF+c-erbB2ASODN group,and weakest in c-erbB2ASODN group. Conclusion:Our results indicate that (1) c-erbB2 exists in the oocyte and has promoting effect on oocyte maturation in vitro and when oocyte's GVBD, c-erbB2mRNA of oocytes is increased. (2) EGF plays a role in inducing denuded oocyte maturation through up-regulating c-erbB2 expression of oocyte. Interferecing c-erbB2 expression can reduce the effect of EGF on oocyte.