Effect of mouse cumulus cells on the in vitro maturation and developmental potential of bovine denuded germinal vesicle oocytes

We investigated the effect mouse cumulus cells (mCCs) on the in vitro maturation (IVM) and developmental potential of bovine denuded germinal vesicle oocytes (DOs). Cumulus-oocyte complexes (COCs), DOs and DOs cocultured with either mCCs (DOs + mCCs) or bovine cumulus cells (bCCs; DOs + bCCs) were subjected to IVM. The meiosis II (MII) rates of DOs, glutathione (GSH) contents, zona pellucida (ZP) hardening and parthenogenetic blastocyst rates of MII oocytes were determined. The relative expression levels of bone morphogenetic protein 15 (BMP-15) and growth differentiation factor 9 (GDF-9) in MII oocytes were measured using quantitative real-time polymerase chain reaction (PCR). mCCs significantly increased the MII rate of DOs from 53.5 +/- 3.58% to 69.67 +/- 4.72% (p < 0.05) but had no effect on the GSH content (2.17 +/- 0.31 pmol/oocyte with mCCs, 2.14 +/- 0.53 pmol/oocyte without mCCs). For the DOs + mCCs group, the BMP-15 and GDF-9 expression levels were significantly higher and the ZP dissolution time was significantly lower (162.49 +/- 12.51 s) than that of the DOs group (213.95 +/- 18.87 s; p < 0.05). The blastocyst rate of the DOs + mCCs group (32.56 +/- 4.94%) was similar to that of the DOs group (31.75 +/- 3.65%) but was significantly lower than that of the COCs group (43.52 +/- 5.37%; p < 0.05). In conclusion, mCCs increased the MII rate of DOs and expression of certain genes in MII oocytes, and decreased the ZP hardening of MII oocytes, but could not improve their GSH content or developmental potential.