How to make a good oocyte: an update on in-vitro models to study follicle regulation.

The ability to develop the technology to mature oocytes from immature oocytes in vitro is the ambition of many IVF clinics. If this can be successfully achieved then these techniques would be available to women with fertility problems. This would aid women at risk of premature ovarian failure, and possibly result in women no longer requiring an expensive drug regime and monitoring programme, which they currently have to undergo. The idea of harvesting immature oocytes for growth in vitro is not a new one, but progress has been slow in developing and optimizing techniques for use on humans and domestic species. At present, there are many technical reasons for the lack of progress in these species, such as length of culture and difficulty of follicle isolation. However, the major problem is our lack of knowledge of how the oocyte acquires developmental competence during its growth within the follicle. To date, culture systems have been developed that can support the growth and development of immature oocytes. These systems are beneficial in improving our knowledge of how autocrine/paracrine factors are involved in regulating and controlling oocyte development. However, only when we have a more in-depth understanding of what is required during development to make a viable oocyte, will we perhaps be able to develop in-vitro culture systems for clinical application. This review will focus on how analysis of early follicular growth and development, using in-vitro culture systems, has advanced our knowledge of the factors and process involved in the regulation of oocyte and somatic cell development.