The effects of melatonin on bovine uniparental embryos development in vitro and the hormone secretion of COCs

Abstract

Melatonin is a unique multifunctional molecule that mediates reproductive functions in animals. In this study, we investigated the effects of melatonin on bovine partheno- genetic and androgenetic embryonic development, oocytematuration, the reactive oxy- gen species (ROS) levels in parthenogenetic and androgenetic embryos and cumulus- oocyte complexes (COCs) hormone secretion with melatonin supplementation at four concentrations (0, 10, 20, and 30 pmol/mL), respectively. The results showed that melatonin significantly promoted the rates of bovine parthenogenetic and androgenetic embryonic cleavage and morula and blastocysts development (P < 0.05). The rate of cleavage was higher in the androgenetic embryo than that in the parthenogenetic embryo. Compared with the parthenogenetic embryos, the androgenetic embryos had a poor developmental competence from morula to blastocyst stage. Moreover, the levels of ROS were significantly lower in the parthenogenetic and androgenetic embryoes with melatonin-treated group than that of the control group (P < 0.05). Melatonin supplemented significantly increased the maturation rate of oocyte in vitro (P <0.05). More importantly, melatonin significantly promoted the secretion of progesterone and estradiol by COCs (P <0.05). To reveal the regulatory mechanism of melatonin on steroids synthesis, we found that steroidogenic genes (CYP11A1, CYP19A1 and StAR)were upregulated, suggesting thatmelatonin regulated estradiol and progesterone secretion throughmediating the expression of steroidogenic genes (CYP11A1,CYP19A1 and StAR). In addition, MT1 and MT2 were identified in bovine early parthenogenetic and androgenetic embryos usingwestern blot. It could be concluded thatmelatonin had beneficial effects on bovine oocyte in vitro maturation, COC hormone secretion, early development of subsequent parthenogenetic and androgenetic embryos. It is inferred that melatonin could be used to enhance the efficiency of in vitro developed embryos.