title: Estrogen receptor-alpha mediates an intraovarian negative feedback loop on thecal cell steroidogenesis via modulation of Cyp17a1 (cytochrome P450, steroid 17alpha-hydroxylase/17,20 lyase) expression.
abstract: Excess androgen synthesis by thecal cells is invariably detrimental to preovulatory follicles in the ovary and is considered a fundamental characteristic of polycystic ovary syndrome in women. Investigators have long postulated that granulosa cell-derived estrogens modulate thecal cell steroidogenesis via a short negative-feedback loop within the follicle. To test this hypothesis, we assessed the steroidogenic capacity of individual wild-type (WT) and estrogen receptor-alpha (ER alpha)-null follicles when cultured in vitro under comparable conditions. Late-stage ER alpha-null follicles exhibited markedly increased expression of the thecal cell enzyme CYP17A1 and secreted much greater amounts of its end product, androstenedione. This phenotype was reproduced in WT follicles when exposed to an aromatase inhibitor or ER-antagonist, and prevented when the former treatment was supplemented with an ER alpha-specific agonist. ER alpha-null follicles also exhibited increased testosterone synthesis due to ectopic expression of hydroxysteroid (17beta) dehydrogenase type 3 (HSD17B3), a testis-specific androgenic enzyme. These data indicate that ER alpha functions within thecal cells to negatively modulate the capacity for androgen synthesis by repressing Cyp17a1 expression, and the biological activity of androgens produced by inhibiting Hsd17b3 expression. Hence, these findings provide novel evidence of an intraovarian ER alpha function that may be critical to the latter stages of folliculogenesis and overall ovarian function.
authors.affiliation: Department of Obstetrics and Gynecology, Tottori University Hospital, Yonago, Japan.
authors.forename: Fuminori
authors.initials: F
authors.lastname: Taniguchi
authors.forename: John F
authors.initials: JF
authors.lastname: Couse
authors.forename: Karina F
authors.initials: KF
authors.lastname: Rodriguez
authors.forename: Judith M A
authors.initials: JM
authors.lastname: Emmen
authors.forename: Donald
authors.initials: D
authors.lastname: Poirier
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Korach
mesh_terms: D000728:Androgens / Q000378:metabolism; D000818:Animals; D001141:Aromatase / Q000378:metabolism; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004958:Estradiol / Q000494:pharmacology; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000502:physiology*; D005260:Female; D015870:Gene Expression; D007118:Immunoassay; D051379:Mice; D018345:Mice, Knockout; D006080:Ovarian Follicle / Q000166:cytology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism; D013799:Theca Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
chemical_list: D000728:Androgens; D047628:Estrogen Receptor alpha; D013739:Testosterone; D004958:Estradiol; D003577:Cytochrome P-450 Enzyme System; D001141:Aromatase; D013254:Steroid 17-alpha-Hydroxylase