Leptin promoted meiotic maturation of bovine oocytes and development of parthenogenetic activation and yak (Bos grunniens)-bovine interspecies cloned embryos

Leptin has a central role in the regulation of oocyte and embryo development. The objective of the current study was to investigate the effect of leptin addition during oocyte maturation in vitro on meiotic maturation of bovine oocytes and development of parthenogenetic activation (PA) and yak-bovine interspecies cloned embryos. In addition, the effect of leptin supplementation in embryo culture medium on preimplantation development of yak-bovine interspecies cloned embryos was investigated. Leptin addition at 10 and 100ng/mL during oocyte maturation significantly increased the proportion of bovine oocytes that developed to metaphase II (MII) stage compared to the control (81.0+/-3.8 and 77.0+/-4.0 versus 62.2+/-1.8, P<0.05). Leptin at 10ng/mL significantly increased the blastocyst rate after PA compared to the control (31.6+/-4.3 versus 20.4+/-3.2, P<0.05). Leptin supplementation at 10ng/mL during oocyte maturation strikingly increased the blastocyst development of yak-bovine interspecies cloned ernbryos (33.2+/- 4.0 versus 22.8+/- 2.7, P<0.05) and the inner cell mass (ICM) and total cell number per blastocyst, and reduced the incidence of apoptotic cells per blastocyst compared to the control. When present in the embryo culture medium, leptin at 100 ng/mL significantly increased the blastocyst development of yak-bovine interspecies cloned embryos compared to the control (34.2 +/- 4.9 versus 22.0 +/- 3.2, P<0.05). Meanwhile, leptin at 100 and 1000ng/mL significantly increased ICM and total cell number per blastocyst and reduced the proportion of apoptotic cells per blastocyst. In conclusion, leptin supplementation promoted the meiotic maturation of bovine oocytes and the developmental capacity of PA and yak-bovine interspecies cloned embryos.