Abstract：To research the effects of heterogeneous mouse cumulus cells (mCCs) on in vitro maturation of bovine denuded oocytes(DOs) and its development after parthenogenesis, bovine denuded germinal vesicle (GV) stage DOs were co-cultured in vitro with a mCCs monolayer in this study. The effect mechanism of cumulus cells on bovine DOs after in vitro maturation(IVM) and parthenogenesis were also discussed, and this could help to provide experimental bases for increasing maturation rate of bovine oocytes in vitro. Bovine oocytes were divided into four groups, namely COCs (cumulus-oocytes complexes) group, DOs+bCCs (bovine cumulus cells) group, DOs+mCCs group and DOs group. The extruded rate of oocytes in different groups of first polar body, glutathione (GSH) content and parthenogenetic development of MⅡ stage oocytes, relative expression levels of bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) mRNA of oocytes were detected after in vitro mature for 22~24h. The results showed that (1) Nuclear maturation rate of DOs+mCCs group and DOs+bCCs group [(68.48±5.71)%, (71.00±4.27)%] were significantly lower than that of COCs group (84.70±3.41)% (P<0.05), but significantly higher than that of DOs group (54.26±5.03)% (P<0.05); After parthenogenetic activation the GSH content and blastocyst rate of MⅡ oocytes of DOs+mCCs group [(2.48±0.24)pmol/oocyte, (44.19±4.03)%] were similar to those of DOs+bCCs group [(2.49±0.18)pmol/oocyte, (48.57±5.20)%] and DOs group [(2.40±0.17)pmol/oocyte, (43.47±7.34)%], but were all significantly lower than those of COCs group [(9.67±0.18)pmol/oocyte, (59.93±6.13)%)](P<0.05), and cleavage rate of different groups showed no significant difference [(98.85±4.32)%, (92.11±2.00)%, (95.40±4.11)%, (93.18±3.19)%] (P>0.05); (3)Relative expression levels of BMP15 and GDF9 mRNA of DOs+mCCs, DOs+bCCs and COCs group were all significantly higher than that of DOs group (P<0.05), but relative expression levels of GDF9 mRNA of DOs+mCCs and COCs group were significantly higher than that of DOs+bCCs group (P<0.05). The result indicated that mCCs could improve nuclear maturation rate and BMP15, GDF9 mRNA relative expression levels of bovine DOs, but could not enhance cytoplasmic maturation of DOs and parthenogenetic embryo development of MⅡ oocytes. It's suggested that cumulus cells can promote bovine oocytes nuclear maturation in vitro through some paracrine factors, and the effects of these factors may have no species specificity.
