Oocyte--granulosa cell interactions.

In the past, different protocols of ovulation induction, aimed to overcome problems of anovulatory infertility in humans, have been developed during IVF programmes. However, administration of exogenous hormones may cause severe health problems, e.g. ovarian hyperstimulation syndrome. To overcome this problem an attractive alternative is to develop in-vitro systems that allow follicle and oocyte growth and maturation. This paper reviews the current status of research on oocyte-granulosa cell interactions and on the autocrine and paracrine factors involved in follicle development. The ovarian follicle is a morphological and functional unit in which the somatic and germ cell components are intimately associated and interdependent. The co-ordinate development of follicle and oocyte leads to a number of modifications in the growing oocyte necessary for the acquisition of competence to mature correctly and to undergo fertilization and embryo development. The search for the optimal culture conditions and the correct balance of hormones necessary to obtain a fertilizable oocyte in vitro is extremely important for clinical and agricultural applications.