In vitro models for oocyte development.

The mammalian ovary has a large store of primordial follicles, which are a potential source of oocytes for in vitro production of embryos. Several culture systems have been developed to support the growth and development of oocytes from rodent primordial and preantral follicles and progress is slowly being made in modifying these techniques to support the in vitro growth of porcine and bovine follicles. Oocytes from porcine preantral follicles can acquire competence to resume meiosis and proceed to Metaphase II after in vitro growth (IVG) but fertilisation has yet to be demonstrated. This paper presents the current status of technology for the in vitro growth and development of immature mammalian oocytes. Culture systems used successfully to grow immature rodent oocytes are compared and adaptations of these methods to support porcine and bovine oocyte growth discussed.