Ovarian follicle culture systems for mammals

Current approaches for the propagation and maintenance of mammalian ovarian follicles are reviewed in the context of the two dominant functional attributes of the follicle: sustaining oogenesis and regulating steroidogensis. Evidence is summarized indicating that the major utility for follicle cultures until recently has been to understand the steroidogenic properties of the follicle especially with regard to estrogen biosynthesis. Less stringent regulation of exposure to gonadotropins is tolerated in most systems when cell survival and differentiation are monitored for both the theca and granulosa components. In sharp contrast, establishing primary cultures of follicles for the maintenance of oogenesis is far more sensitive to a variety of experimental conditions and can in many cases compromise both the growth and maturative phases of oogenesis, a more recent focus for the applications of follicle culture in assisted reproductive technologies. Specific parameters that are discussed include media supplements, oocyte-granulosa interactions, culture atmosphere requirements, and maintenance of three-dimensional architecture. Limitations based upon species variations and the need for microfluidic devices are discussed in the context of clinically relevant translational goals especially as they pertain to the emerging field of fertility preservation.