The role of intra-ovarian interactions in the regulation of follicle dominance

Abstract

The processes that precisely control the selection of ovulatory follicles from a growing cohort are poorly understood. This reduction in follicle number occurs through several phases of selection, consequently we limit the use of the term 'selection' to the first major reduction of growing follicles, at the pre-to early antral stage. The final process of selection, achieving the appropriate ovulatory number, is referred to as 'dominance'. We discuss possible mechanisms that could bring about these reductions and highlight intra-ovarian involvement, particularly via follicle-follicle interactions. Analogies are drawn between local ovarian events and processes commonly reported in the determination of cell fate in developmental biology. Two facets of intra-follicular interactions are proposed: initially that follicle-follicle interactions mediate early selection processes at the preantral stage, and later that during antral development dominant follicles directly affect the fate of the subordinate cohort members.

Assessing ovarian response: antral follicle count versus anti-Müllerian hormone

“…The ovarian reserve is principally composed of 'resting' primordial follicles, which may remain at the arrested stage of development for more than 40 years before developing into primary follicles (Baerwald et al, 2012;Gougeon, 1996;Gougeon et al, 1994). Most (>99%) primordial follicles that undergo further development will be lost to atresia during the maturation process (Baerwald et al, 2012;Baker and Spears, 1999). Once a primordial follicle has been selected to enter active follicular growth, granulosa cells of the now primary follicle begin to express AMH (Visser and Themmen, 2005;Weenen et al, 2004).…”

Xenografting of Bovine Secondary Follicles into Ovariectomized Female Severe Combined Immunodeficient Mice

“…Although the mechanism that regulates the selection of a species-specific number of dominant follicles for ovulation is not yet well understood, it is known that only one follicle is selected and ovulated in each estrous cycle in the cow. In vivo, this mechanism of follicular selection is considered to be influenced by the concentration of circulating hormones [16,17]. Gonadotrophins are involved in follicular development and apoptosis.…”

In vitro maturation of human oocytes for assisted reproduction

“…In standard IVF, exogenous gonadotropins are used to rescue the growth of small follicles that would have been inhibited otherwise by the dominant one. In IVM, the strategy is to retrieve and rescue immature oocytes before they can be adversely affected by the endocrine and paracrine influences of the growing dominant follicle (21,22). Ideally, retrieval of immature oocytes should occur around the time of selection of the dominant follicle.…”