Improved cloning efficiency and developmental potential in bovine somatic cell nuclear transfer with the oosight imaging system.

In somatic cell nuclear transfer (SCNT) procedures, exquisite enucleation of the recipient oocyte is critical to cloning efficiency. The purpose of this study was to compare the effects of two enucleation systems, Hoechst staining and UV irradiation (hereafter, irradiation group) and Oosight imaging (hereafter, Oosight group), on the in vitro production of bovine SCNT embryos. In the Oosight group, the apoptotic index (2.8 ± 0.5 vs. 7.3 ± 1.2) was lower, and the fusion rate (75.6% vs. 62.9%), cleavage rate (78.0% vs. 63.7%), blastocyst rate (40.2% vs. 29.2%), and total cell number (128.3±4.8 vs. 112.2 ± 7.6) were higher than those in the irradiation group (all p<0.05). The overall efficiency after SCNT was twice as high in the Oosight group as that in the irradiation group (p<0.05). The relative mRNA expression levels of Oct4, Nanog, Interferon-tau, and Dnmt3A were higher and those of Caspase-3 and Hsp70 were lower in the Oosight group compared with the irradiation group (p<0.05). This is the first report to show the positive effect of the Oosight imaging system on molecular gene expression in the SCNT embryo. The Oosight imaging system may become the preferred choice for enucleation because it is less detrimental to the developmental potential of bovine SCNT embryos.