ABSTRACT
Background: it is important to protect oocytes and embryos from oxidative stress in the culture medium. Melatonin has been shown to be a direct free radical scavenger
Objective: Effect of melatonin during in vitro oocyte maturation, fertilization and embryo development of mouse oocytes was evaluated
Materials and Methods: oocytes from supper-ovulated mouse were divided to two groups: cumulus oocyte complexes [COCs, group I] and denuded COC [d-COCs, group II]. The oocytes were cultured in maturation medium with different doses of melatonin [1×10[1]-10[5] nM] The cumulus expansion and nuclear status were evaluated after 24 h of in-vitro maturation. The oocytes were used for in-vitro fertilization. The fertilized oocytes were cultured in medium supplemented with different doses of melatonin
Results: the expansion [86.79%] and maturation [80.55%] rate of COCs increased in supplemented medium with 10 nM of melatonin vs. control group [73.33%], p=0.006 and p=0.026 respectively], but oocytes without cumulus cells indicated higher maturation rate at higher melatonin doses [10 and 100 ?M, 84.34% and 79.5% respectively[ vs. 69.33% in control group [p=0.002]. Fertilization rate was higher in treated medium with 1 [micro]M of melatonin [93.75%, p=0.007]
The rate of cleavage and blastocyst formation was promoted in medium supplemented with 10 and 100 nM of melatonin [92.37% and 89.36% vs. 81.25% in control group, p=0.002] We observed a dose dependent response to melatonin treatment in this experiment
Conclusion: exogenous melatonin can promote cumulus cell expansion, in vitro oocyte maturation, and embryo development. However we investigated a dose-dependent response in different stages of maturation and development. It may reflect sensitive rate of oocytes and embryos to culture conditions
ABSTRACT
Melatonin is a scavenger agent that has been used to promote in vitro embryo development. This study was designed to show the effects of melatonin on the quality and quantity rate of preimplantation mouse embryo development and pregnancy. In this experimental study, super ovulated, mated mice were killed by cervical dislocation to collect two-cell zygotes from the oviduct of pregnant 1 day NMRI mice. Zygotes were cultured to the hatching blastocyst stage and the numbers of embryos at different stages were recorded under an inverted microscope. The cleavage rates of two-cell zygotes were assayed until the blastocyst and hatching blastocyst stage in drops of T6 medium that contained either melatonin [1, 10, and 100×10[6], 10 and 100×10[9] M] or no melatonin. The cell numbers of blastocysts were determined by differential staining, implantation outcomes were studied, and development and pregnancy rate were compared by the Chi-square [development] and Fisher's exact [pregnancy rate] tests. The addition of 10 and 100 nM melatonin to the embryo culture media promoted the development of the two-cell stage embryos to blastocyst and hatching blastocysts [p<0.01] and caused a significant increase in total cell number [TCN], trophoectoderm [TE], and inner cell mass [ICM] of the blastocysts [p<0.01]. A difference was observed in the percentage of transferred embryos that were successfully implanted between the control and treatment groups [p<0.05]. The data indicate that 10 and 100 nM of melatonin positively impact mouse embryo cleavage rates, blastocyst TCN, and their implantation. Therefore, melatonin at low concentrations promotes an embryonic culture system in mice