The role of steroidogenic factor 1 (SF-1) in steroidogenic cell function of the testes and ovaries of mature mice.

In brief: The nuclear receptor steroidogenic factor 1 (SF-1) is essential for mature mouse gonad steroidogenic gene expression, for Leydig and Sertoli cell function, and depletion of SF-1 in steroidogenic cells of the testis compromises steroidogenesis, spermatogenesis and male fertility. Abstract: Steroidogenic factor 1 (SF-1 or NR5A1) plays an essential role in the development of fetal gonads and regulates genes involved in steroid biosynthesis. Since SF-1 is expressed in multiple cell types in mouse gonads, we developed three novel conditional knockout (cKO) mouse models employing Cre-recombinase and floxed alleles of SF-1 (Nr5a1f/f) to identify its role in testes and ovaries of mature mice: Cytochrome P450 17α-hydroxylase (Cyp17Cre/+;Nr5a1f/f, Leydig and theca cell-specific), aromatase (Cyp19Cre/+;Nr5a1f/f, Sertoli and granulosa cell-specific), as well as a combination of both (Cyp17+Cyp19-Cre;Nr5a1f/f). Compared to control animals, Cyp19-Cre;Nr5a1f/f cKO males showed normal fertility and testicular function. The Cyp17Cre/+;Nr5a1f/f cKO males had smaller testis, with drastically reduced Leydig cell volumes and impaired steroidogenesis, though their reproductive performance remained comparable to controls. Some 50% of Cyp17Cre/++Cyp19Cre/+;Nr5a1f/f double-cKO (dKO) males were infertile, while the remaining 50% showed significantly reduced fertility. These dKO males also had smaller testis with degenerative seminiferous tubules, abnormal Leydig cell morphology and lower levels of intra-testicular testosterone. Abnormal Sertoli cell localization was noted in dKO testes, with increased Sox9, p27 and inhibin subunit ßb and decreased androgen receptor expression. Female mice from all genotypes showed normal reproductive capacity, though steroidogenic gene expression levels were significantly decreased in both Cyp17Cre/+;Nr5a1f/f cKO and dKO females. These results show the essential role of SF-1 in mature mouse gonad steroidogenic gene expression, for Leydig and Sertoli cell function, and that depletion SF-1 in all steroidogenic cells of the testis compromises steroidogenesis, spermatogenesis and male fertility.

Steroidogenic Factor 1 Regulation of the Hypothalamic-Pituitary-Ovarian Axis of Adult Female Mice.

The orphan nuclear receptor steroidogenic factor-1 (SF-1 or NR5A1) is an indispensable regulator of adrenal and gonadal formation, playing roles in sex determination, hypothalamic development, and pituitary function. This study aimed to identify the roles of SF-1 in postnatal female reproductive function. Using a progesterone receptor-driven Cre recombinase, we developed a novel murine model, characterized by conditional depletion of SF-1 [PR-Cre;Nr5a1f/f; conditional knockout (cKO)] in the hypothalamic-pituitary-gonadal axis. Mature female cKO were infertile due to the absence of ovulation. Reduced gonadotropin concentrations in the pituitary gland that were nevertheless sufficient to maintain regular estrous cycles were observed in mature cKO females. The cKO ovaries showed abnormal lipid accumulation in the stroma, associated with an irregular expression of cholesterol homeostatic genes such as Star, Scp2, and Acat1. The depletion of SF-1 in granulosa cells prevented appropriate cumulus oöphorus expansion, characterized by reduced expression of Areg, Ereg, and Ptgs2. Exogenous delivery of gonadotropins to cKO females to induce ovulation did not restore fertility and was associated with impaired formation and function of corpora lutea accompanied by reduced expression of the steroidogenic genes Cyp11a1 and Cyp19a1 and attenuated progesterone production. Surgical transplantation of cKO ovaries to ovariectomized control animals (Nr5a1f/f) resulted in 2 separate phenotypes, either sterility or apparently normal fertility. The deletion of SF-1 in the pituitary and in granulosa cells near the moment of ovulation demonstrated that this nuclear receptor functions across the pituitary-gonadal axis and plays essential roles in gonadotropin synthesis, cumulus expansion, and luteinization.

The endogenous hydrogen sulfide generating system regulates ovulation.

The generation of free-radicals such as nitric oxide has been implicated in the regulation of ovarian function, including ovulation. Tissues that generate nitric oxide typically generate another free-radical gas, hydrogen sulfide (H2S), although little is known about the role of H2S in ovarian function. The hypothesis of this study was that H2S regulates ovulation. Treatment with luteinizing hormone (LH) increased the levels of mRNA and protein of the H2S generating enzyme cystathionine γ-lyase (CTH) in granulosa cells of mice and humans in vivo and in vitro. Pharmacological inhibition of H2S generating enzymes reduced the number of follicles ovulating in mice in vivo and in vitro, and this inhibitory action was reversed by cotreatment with a H2S donor. Addition of a H2S donor to cultured mouse granulosa cells increased basal and LH-dependent abundance of mRNA encoding amphiregulin, betacellulin and tumor necrosis alpha induced protein 6, proteins important for cumulus expansion and follicle rupture. Inhibition of CTH activity reduced abundance of mRNA encoding matrix metalloproteinase-2 and -9 and tissue-type plasminogen activator, and cotreatment with the H2S donor increased the levels of these mRNA above those stimulated by LH alone. We conclude that the H2S generating system plays an important role in the propagation of the preovulatory cascade and rupture of the follicle at ovulation.