Follicular development in vitro.

There has been tremendous interest in recent years in the culture of oocytes and follicles. Although much of the research using follicle culture aims to increase understanding of the regulation of follicle development, an important goal has been to develop a method that will eventually allow maturation of human oocytes from the primordial follicle to the mature Graafian stage. We are still some way from this at present, although it has now been achieved in the mouse. In this article, we consider various methods of follicle culture for primordial, preantral, and antral follicles. In vitro development of primordial follicles has used primarily whole ovaries or ovarian fragments as a source of follicles. Culture of later stages of follicle development uses mainly isolated follicular units, either whole (with an intact basement membrane and, in some cases, attached thecal cells) or nonintact (oocyte-somatic cell complexes, which may or may not have remnants of basement membranes and/or thecal cells attached).