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Pre‐maturation with cAMP modulators in conjunction with EGF‐like peptides during in vitro maturation enhances mouse oocyte developmental competence

Recent studies have independently shown that cyclic adenosine 3′5′‐monophosphate (cAMP) modulation prior to in vitro maturation (IVM) and epidermal growth factor (EGF)‐like peptide supplementation during IVM improve subsequent oocyte developmental outcomes. This study investigated the effects of an IVM system that incorporates these two concepts. Cumulus–oocyte complexes (COCs) were collected from pre‐pubertal mice either 46 hr post‐equine chorionic gonadotropin (eCG) (IVM) or post‐eCG + post‐human chorionic gonadotropin (hCG) stimulation (in vivo maturation; IVV). IVM COCs were treated with the cAMP modulators forskolin and IBMX for 1, 2, or 4 hr (pre‐IVM phase) prior to IVM. COCs then underwent IVM with the EGF‐like peptides amphiregulin or epiregulin, or with the common IVM stimulants follicle‐stimulating hormone (FSH) or EGF. A pre‐IVM phase increased the size of the subsequent blastocysts' inner‐cell‐mass compared to standard IVM, regardless of IVM treatment (P < 0.05). Unlike FSH or EGF, amphiregulin or epiregulin significantly increased blastocyst quality (trophectoderm and total cell numbers) and/or yield (P < 0.01) compared to standard IVM, and were the only treatments that produced blastocysts comparable to IVV‐derived blastocysts. Forskolin acutely up‐regulated EGF‐like peptide mRNA expression after a 2‐hr pre‐IVM phase (P < 0.001), although EGF receptor and ERK1/2 activities were not significantly different than control. IVV‐like levels of EGF‐like peptide mRNA expression during IVM were maintained only by supplementing with EGF‐like peptides and EGF, since expression levels induced by FSH were significantly lower in vitro than during IVV. However, EGF receptor and ERK1/2 phosphorylation levels were not significantly different across treatment groups. In conclusion, a pre‐IVM phase in conjunction with IVM in the presence of EGF‐like peptides endows high oocyte developmental competence, as evidenced by increased embryo yield and/or quality relative to FSH and EGF. Mol. Reprod. Dev. 81: ???–???, 2014. © 2014 Wiley Periodicals, Inc.