Dynamics of human follicular growth and in-vitro oocyte maturation.

The physiological trigger for meiotic resumption in the human oocyte is the surge of luteinizing hormone, but it can also occur spontaneously if oocytes are released from antral follicles and cultured in vitro. The development of novel techniques for the culture of murine oocytes has raised the possibility of growing human oocytes to maturity in vitro. Such a system could open the door to a number of techniques with revolutionary consequences. It would clearly be of benefit in basic physiological studies of follicular development, as well as being used to test the effect of toxicological substances on oocyte maturation. More significantly, such a system could provide a source of human oocytes for in-vitro fertilization (IVF) where immature or germinal vesicle oocytes are cultured to maturity before being fertilized. If this can be achieved, it might facilitate oocyte cryopreservation, where surplus oocytes are stored, thus avoiding the need for repeated superovulation. A combination of immature oocyte cryopreservation for later maturation and IVF will provide the opportunity to establish oocyte banks and help overcome some of the practical and ethical dilemmas that are currently shadowing the field of reproductive medicine.