Growth and Differentiation of Small Ovarian Follicles in Mammals: Problems and Future Perspectives

Abstract

The in vitro development of mammalian ovarian follicles still represents a challenge. Results achieved in the past several years have clarified some important aspects concerning the regulation of follicle and oocyte development, but the complexity of the process leading in vivo to the production of a fertilizable egg makes quite difficult to obtain large numbers of fully-grown mature germ cells starting from in vitro cultured follicles. The main problem is that culture systems currently utilized do not assure satisfactorily a co-ordinate development of both the somatic and germinal components of the ovarian follicle. An ideal culture media might be specially designed by the addition of specific components in correct ratio, in the attempt to reflect the dynamic changes which characterize follicle development. This is important, especially in the light of the fact that the period of culture could vary considerably, depending on the timing of follicle growth in vivo in the various species, being also influenced by the age of donors, methods and aims of culture. Despite this, in vitro technology represents not only an important tool to understand regulative processes underlying follicle development, but also a future option for the preservation of fertility. The present paper reviews current knowledge on advances and problems relevant to the culture of primordial and preantral mammalian follicles.