The effects of leptin on in vitro development of mouse embryos

Cho, Young Rok; Joo, Jong Kil; Kim, Hwi Gon; Na, Yong Jin; Lee, Kyu Sup

Abstract

OBJECTIVE
To investigate the effects of leptin on in vitro development of mouse embryos.
METHODS
Female C57BL mice, aged 8 to 15 weeks, were superovulated with IP injection of 5 IU of PMSG followed by 5 IU hCG at 48 hours later. And then the mice were mated with male mice. The next morning, one-cell embryos were collected and cultured in media added with various concentrations (0, 5, 50, 500 ng/mL) of leptin for 4 days. In addition, to determine whether the sensitivity to leptin varied at different stages of development, embryos at 2- or 4-cell stage were treated with the same concentrations of leptin and cultured up to blastocyst stage. The total cell number of blastocyst was assessed and the expression of leptin receptor was examined in all stages of development by immnuofluorescence.
RESULTS
The rate of blastocyst formation from one-cell embryos significantly increased at culture media that leptin was added at 50 ng/mL concentration, whereas decreased at 500 ng/mL concentration compared to the control (P<0.05). The development rate of embryos, from 2-cell stage, was similar to the rate from 1-cell stage. However, the addition of leptin to culture media in 4-cell embryos had no significant effects on embryo development compared to the control. In addition, the dose-dependent stimulatory or inhibitory effect of leptin on embryo development was weakened at 2-cell and 4-cell embryo stages compared one-cell embryo stage. The total cell number of blastocyst also significantly increased at 50 ng/mL of leptin, but decreased at 500 ng/mL. Leptin receptor was expressed in all stages from one-cell embryos to blastocyst. The intensity of Ob-Rb immnuostaining was mainly stronger in one- or two-cell embryos, decreased with advancing development stages, and increased again in blastocyst.
CONCLUSION
This study shows that addition of leptin to embryo culture media affects embryo development in a dose-dependent and developmental stage-dependent manner. The effects of leptin seems to be associated with the expression pattern of leptin receptor at different stages of development.