Functional AR signaling is evident in an in vitro follicle culture bioassay that encompasses most stages of folliculogenesis.

Androgens serve distinct physiological functions within the ovary. The biological action of androgens is primarily exerted through transcriptional regulation by the nuclear androgen receptor (AR), but the molecular cascades governed by AR remain largely unknown. At present, there is eminent concern that environmental man-made chemicals with (anti-)androgenic properties among other are capable of modulating hormonal responses thereby interfering with normal physiological processes, critical to fertility. In the present study, we aimed to further characterize a standardized and reproducible follicle culture system in terms of AR expression during in vitro folliculogenesis in order to be able to use it as a bioassay to study effects of (anti-)androgens on follicular and oocyte growth, steroid secretion profile and oocyte meiotic maturation capacity. Immunohistochemical analysis revealed cytoplasmic AR protein was translocated to the nucleus of both granulosa and theca cells in response to endogenous androgen production in theca cells during preantral follicular development. During the antral phase in vitro, AR was differentially expressed in mural and cumulus cells, implying an oocyte-mediated regulation. Treatment of follicles with either hydroxyflutamide or bicalutamide, two model anti-androgenic compounds, resulted in a reduced follicular growth during the preantral phase, an altered steroidogenic environment, and an arrest in oocyte meiotic maturation in response to hCG. In conclusion, AR expression in the culture model corresponded well to what is described in vivo and this system revealed several ovarian functions being targeted by AR antagonists that can be further investigated by more in-depth molecular techniques.