Melatonin effect during different maturation stages of oocyte and subsequent embryo development in mice

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 (1×101-105 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 ?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. key words: in vitro oocyte maturation, development, in vitro fertilization, melatonin, cumulus-oocyte complex