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 tis- sue function. Previous studies, performed both in vivo and in vitro, indicate that retin- oids 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 ex- perimental groups. t-RA at concentrations of 1, 2, 4, 6, 8 ?M 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 at 37°C. 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 ?? stage of maturation significantly increased with 2 and 4 ?M t-RA compared to the control and sham groups (p < 0.05). In addition, the number of fertilized oocytes was significantly higher in 4 ?? 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.