Effect of injected position of cultured cumulus cells as donor cells on reconstructed in vitro matured porcine oocytes

The effect was studied of injected position of cultured cumulus cells as donor cells for nuclear transfer on the process of in vitro matured reconstructed porcine oocytes. The cumulus-oocyte complexes (COCs) obtained from ovaries were cultured in NCSU-23 maturation medium. The cumulus cells were separated from matured COCs, and cultured in DMEM medium (10% fetal calf serum, FCS) for up to 4 passages. The cultured cumulus cells were injected into the enucleated oocytes to obtain the reconstructed oocytes. The chosen positions were the perivitelline space, ooplasm edge and ooplasm center. After nuclear transfer, the reconstructed oocytes were fused and activated simultaneously. Then, the activated oocytes were cultured in NCSU-23 embryo culture medium for 16 h to observe the activation, or 144 h to observe the embryo development. It was found that the injected position affected the activation rate, pronuclear formation rate and embryo development rate of the reconstructed oocytes significantly. The activation rate, pronuclear formation rate and embryo development rate of the ooplasm edge group were obviously greater than the perivitelline space and ooplasm center groups. Furthermore, the injected position at the ooplasm edge favoured the more advanced development. The ooplasm edge would be an optimum injected position.