The Effect of Retinoic Acid on in vitro Maturation and Fertilization Rate of Mouse Germinal Vesicle Stage Oocytes

OBJECTIVE: Retinoids are recognized as important regulators of cell differention and tissue function. Previous studies, performed both in vivo and in vitro, indicate that retinoids influence several reproductive events. In this study, we investigated the effect of all-trans retinoic acid (t-RA) on maturation and fertilization rate of immature oocytes (germinal vesicle). MATERIALS AND METHODS: Germinal vesicle (GV) oocytes were recovered from 4-6 week old female mice 48 hours after injection of 10 IU pregnant mare serum gonadotropin (PMSG). Collected oocytes were divided into seven groups: control, sham and five experimental groups. t-RA at concentrations of 1, 2, 4, 6, 8 µM were added to oocyte maturation medium in the experimental groups. The maturation rate was recorded after 24 hours of culture in a humidified atmosphere of 5% CO(2) at 37℃. Fertilization and developmental rates of matured oocytes were recorded after in vitro fertilization (IVF) and 24 hour culture. RESULTS: The rate of oocytes that developed to the metaphase ІІ stage of maturation significantly increased with 2 and 4 µM t-RA compared to the control and sham groups (p<0.05). In addition, the number of fertilized oocytes was significantly higher in 4 µµ retinoic acid compared to the control (p<0.05), but the difference between the number of fertilized oocytes which developed to the 2-cell stage was not significant between the two groups. CONCLUSION: The results show that t-RA enhanced mouse oocyte maturation in vitro and improved fertilization and development rates in a dose dependent manner.