Stage-dependent Effect of Leptin on Development of Porcine Embryos Derived from Parthenogenetic Activation and Transgenic Somatic Cell Nuclear Transfer

Accumulating evidence suggests that leptin may play important roles in preimplantation embryonic development, although this remain controversial, and little is known about whether leptin has a stage-dependent regulatory effect on development of porcine embryos derived by parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT). The objective of this study was to investigate the effects of addition of leptin to in vitro culture (IVC) medium on development of porcine embryos derived by PA and SCNT. We found that addition of 50 ng/ml human recombinant leptin improved the rate of PA embryos reaching the blastocyst stage and increased the total cell number of blastocysts compared with the control group. The maximal blastocyst rate of SCNT embryos was achieved at 50 ng/ml, and the total cell number of blasocysts was increased significantly at 500 ng/ml leptin concentration. However, the ratio of the inner cell mass (ICM) to total cell number was not affected in any of the groups. Supplementation of leptin (50 ng/ml) from day 3, approximately the 4-8-cell stage, as in the case of the positive control, significantly increased the blatocyst rate of PA embryos compared with the negative control and inhibited cell apoptosis. There were no beneficial effects on embryonic development when 50 ng/ml leptin was added to the culture medium from day1 to day 3 or from day 4 to day 6. These results indicate that leptin could improve the development and the quality of PA and SCNT embryos; and 50 ng/ml leptin performs its primary stimulatory effect at 4-8-cell stage and that leptin may have no effect on the maternal-zygote transition (MZT) of porcine PA and SCNT embryos.