In vitro culture methods of preantral follicles.

Folliculogenesis is a highly regulated, dynamic process requiring various autocrine, paracrine, and endocrine factors that need to be reproduced in vitro. The mammalian ovary consists of a finite number of follicles at birth, with the majority in a quiescent state, awaiting recruitment. In vitro culture of preantral follicles presents a unique challenge of mimicking the dynamics of the ovarian environment, a methodical sequence of cell communication, and interaction with secretory, hormonal, and growth factors. In larger mammalian species, maintenance of follicular morphology is imperative to maintain communication between the cumulus-oocyte complexes. Three-dimensional culture systems help to maintain this architecture and have been used for the successful culture of follicles in various animal models, including humans and nonhuman primates, and have resulted in live birth in rodent models. Clinically, in vitro follicular development could revolutionize assisted reproductive technology by providing a means of using the more numerous immature ovarian follicles in patient populations that are unable to undergo ovarian stimulation.