Melatonin promotes the cumulus–oocyte complexes quality of vitrified–thawed murine ovaries; with increased mean number of follicles survival and ovary size following heterotopic transplantation

We have tested the protective effect of melatonin on neonate murine ovarian tissue after vitrification, thawing and heterotopic transplantation into ovariectomized recipient mice. Vitrified ovaries from neonate (CBA × C57Bl/6) F1 hybrid mice were thawed under standard condition with or without the addition of 100 µM melatonin. Following transplantation, melatonin (20 mg/kg/day) or saline solution (physiological saline) was injected i.p. to the treated and non-treated groups for 48 h respectively. Follicle survival and development, together with ovary size followed. Also, vaginal cytology was carried out for monitoring restored puberty. Histological and immunohistochemical studies showed that melatonin could promote the quality of the cumulus–oocyte complexes with uniform distribution of granulosa and stromal cells in the ovarian grafts. Furthermore, the mean follicles survival was improved and the ovary size increased (P ≤ 0.001). The overall mean number of follicles entering the next maturation stage dramatically increased. However, the revascularization and restoration of puberty of ovarian grafts were similar between melatonin-treated and control groups. In conclusion, melatonin as a protection from ischemic injury and a reduce oxidative stress, was shown beneficial during the early days of transplantation.