136 INVESTIGATION OF LEPTIN ON DEVELOPMENT OF MOUSE EMBRYOS

Abstract

Leptin is a hormone-like protein of 167 amino acids. As an adipocyte-related hormone it has an important role in weight regulation and physical fitness but also has effects on reproductive and other physiological mechanisms. The aim of the present study was to investigate the effects of different concentrations of leptin added to the culture media, the quality, in vitro development rate, and in vivo rate of mouse embryos. Superovulated CB6F1 (C57BL/6XBalb/c) hybrid female mice (5–6 weeks of age) were killed ~18 to 20 h after hCG administration. Single-cell embryos were flushed from the oviducts of the dead mice with human tubal fluid medium supplemented with HEPES and 3 mg mL^–1 of BSA. They were cultured in Quinn's cleavage medium supplemented with 4 mg mL^–1 of BSA in 5% CO₂, 37°C until reaching 2-cell stage. The 2-cell embryos were randomly divided into 4 groups and cultured in Quinn's blastocyst medium supplemented with 4 mg mL^–1 BSA + 0, 10, 50, and 100 ng mL^–1 leptin (L0, L10, L50, and L100) in 5% CO₂, 37°C until the blastocyst stage. Some of the developing blastocysts were used for differential staining for the inner cell mass and trophectoderm (TE) cells [Mallol et al. 2013 Syst. Biol. Reprod. Med. 59,117–122]. Some of them were transferred into pseudopregnant females (CD1) on the 2.5 to 3.5th days and kept until the 13.5th day of pregnancy for the in vivo development rate. The results were evaluated using one-way ANOVA with Bonferroni post-hoc test in SPSS 22.0. The P-values <0.05 were considered statistically significant. Each experiment was repeated at least 4 times. The blastocyst development rates of L0, L10, L50, and L100 were 92.57% (162/175), 97.16% (205/211), 97.80% (178/182), and 97.85% (182/186), respectively. The in vitro development rates were significantly higher in the L10, L50, and L100 compared with L0 (P < 0.05). The inner cell mass cells of L0, L10, L50, and L100 were 13.17, 14, 16, and 15.43. There was no significant difference between the groups in terms of inner cell mass cells (P > 0.05). The TE cells of L0, L10, L50, and L100 were 47, 56.4, 53.7, and 58.57, respectively. The TE numbers were significantly increased in the presence of L10 and L100 compared with L0 (P < 0.05). The in vivo development rates of L0, L10, L50, and L100 were 13.51% (5/37), 48.72% (19/39), 15.38% (6/39), and 41.03% (16/39), respectively. The in vivo development rates of L10 and L100 were significantly higher than for L0 and L50 (P < 0.05). The resorption rates of L0, L10, L50, and L100 were 10.8% (4/37), 30.8% (12/39), 12.8% (5/39), and 20.5% (8/39), respectively. There was no significant difference between the groups in terms of the resorption rates (P > 0.05). This study found that L10, L50, and L100 were supporting the development of the embryos in the in vitro culture. The L10, L50, and L100 significantly increased the total cell numbers. The L10 and L100 were particularly effective on the number of the TE cells. In conclusion, 10 and 100 ng mL^–1 leptin have a positive effect on the in vitro, quality and in vivo development of the mouse embryo. Therefore, leptin seems to play an important role on the embryo development and in vivo development.

Research supported by TUBITAK-113O223.