Effect of Melatonin on Developmental Competence of Denuded Human Oocytes During in Vitro Maturation

Melatonin is known to be a free radical scavenger and to exist at high concentrations in follicular fluid. It has been previously reported that supplementation of culture medium with melatonin improves oocyte maturation and embryo development in vitro in several animal models. It has been further reported that melatonin also has an effect on denuded bovine oocytes.We studied the effect of supplementing in vitro maturation (IVM) medium with melatonin on oocyte maturation and embryo development. This retrospective study was performed between July 2016 and December 2016. We analyzed 536 immature oocytes from 214 patients following clomiphene or letrozole stimulation. Oocytes were denuded with hyaluronidase then cultured in M199 supplemented with 25 μM dbcAMP and 50 ng/ml EGF (mM199; control). In the melatonin group (MT), mM199 was supplemented with 0.1 nM melatonin. After 27h IVM, mature oocytes were observed spindles by poloscope prior to ICSI. Fertilized embryos were cultured for 5 days. We studied the effect of melatonin on oocyte maturation, spindle visualization, fertilization, cleavage and blastocyst development. There were no significant differences between the control and MT groups in nuclear maturation rate or fertilization rate (51.4% vs. 45.6%, 86.0% vs. 75.9% respectively). While the number of mature oocytes with visible spindles in the MT group (74.5%) was significantly higher than in controls (61.3%), cleavage rate and blastocyst formation rates, per fertilized oocytes, were similar between the two groups (control vs. MT, 87.5% vs. 90.7%, 20.0% vs. 22.4% respectively). There was no significant difference in blastocyst developmental rate per IVM. Melatonin improved the spindle visualization rates of matured oocytes observed by polscope. However maturation rate, fertilization rate, and blastocyst development did not improve.