Growth and development of mammalian oocytes in vitro

In mammalian ovaries, most of the oocytes are in early stages of development and only a small number of these will complete their development, ovulate, and be available for fertilization. Systems for the culture of oocytes at these early stages, when they are present in preantral follicles, are described herein. Results show that oocytes can undergo a major part of their development in vitro. As methods for oocyte development in vitro improve, these culture systems will allow the efficient use of the large available pool of preantral follicles for clinical, agricultural, or zoological purposes.