Bovine somatic cell nuclear transfer using mitomycin C-mediated chemical oocyte enucleation

Chemical oocyte enucleation holds the potential to ease somatic cell nuclear transfer (SCNT), although high enucleation rates remain limited to micromanipulation-based approaches. Therefore, this study aimed to test mitomycin C (MMC) for use in bovine functional chemical oocyte enucleation. Incubation of denuded eggs in 10 mu g ml(-1) MMC for different periods did not affect most maturation rates (0.5 h: 85.78%(A), 1.0 h: 72.77%(B), 1.5 h: 83.87%(A), and 2.0 h: 82.05%(A)) in comparison with non-treated controls (CTL; 85.77%(A)). Parthenogenetic development arrest by MMC was efficient at cleavage (CTL: 72.93%(A), 0.5 h: 64.92%(A,B), 1.0 h: 60.39%(B,C), 1.5 h: 66.35%(A,B), and 2.0 h: 53.84%(C)) and blastocyst stages (CTL: 33.94%(A), 0.5 h: 7.58%(B), 1.0 h: 2.47%(C), 1.5 h: 0.46%(C), and 2.0 h: 0.51%(C)). Blastocysts were obtained after nuclear transfer (NT) using MMC enucleation [NT(MMC): 4.54%(B)] but at lower rates than for the SCNT control [NT(CTL): 26.31%(A)]. The removal of the meiotic spindle after MMC incubation fully restored SCNT blastocyst development [NT(MMC+SR): 24.74%(A)]. Early pregnancies were obtained by the transfer of NT(MMC) and NT(MMC+SR) blastocysts to synchronized recipients. In conclusion, MMC leads to functional chemical oocyte enucleation during SCNT and further suggests its potential for application towards technical improvements.