In vitro development of reconstructed porcine oocytes after somatic cell nuclear transfer

This study was designed to examine the developmental ability of porcine emb ryos after somatic cell nuclear transfer. Porcine fibroblasts were isolated from fetuses at Day 40 of gestation. In vitro-matured porcine oocytes were enucleated and electrically fused with somatic cells. The reconstructed eg gs were activated using electrical stimulus and cultured in vitro for 6 day s. Nuclear-transferred (NT) embryos activated at a field strength of 120 V/ mm (11.6 +/- 1.6%) showed a higher developmental rate as compared to the 15 0-V/mm group (6.5 +/- 2.3%) (P < 0.05), but the mean cell numbers of blasto cysts were similar between the two groups. Rates of blastocyst development from NT embryos electrically pulsed at different times (2, 4, and 6 h) afte r electrofusion were 11.6 +/- 2.9, 6.6 +/- 2.3, and 8.1 +/- 3.3%, respectiv ely. The mean cell numbers of blastocysts developed from NT embryos were gr adually decreased (30.4 +/- 10.4 > 24.6 +/- 10.1 > 16.5 +/- 7.4 per blastoc yst) as exposure time (2, 4, and 6 h) of nuclei to oocyte cytoplast before activation was prolonged. There was a significant difference in the cell nu mber between the 2- and 6-h groups (P < 0.05). Nuclear-transferred embryos (9.4 +/- 0.9%) had a lower developmental rate than in vitro fertilization ( IVF)-derived (21.4 +/- 1.9%) or parthenogenetic embryos (22.5 +/- 7.2%) (P < 0.01). The mean cell number (28.9 +/- 11.4) of NT-derived blastocysts was smaller than that (38.6 +/- 10.4) of IVF-derived blastocysts (P < 0.05) an d was similar to that (29.9 +/- 12.1) of parthenogenetic embryos. Our resul ts suggest that porcine NT eggs using somatic cells after electrical activa tion have developmental potential to the blastocyst stage, although with sm aller cell numbers compared to IVF embryos.