The intraovarian actions of estrogen receptor-alpha are necessary to repress the formation of morphological and functional Leydig-like cells in the female gonad

Dysregulation of AR and ERα caused ovarian alterations in gerbils prenatally exposed to 17α-ethinylestradiol and pequi oil

This study investigated the effects of prenatal exposure to pequi oil and 17α-ethinylestradiol (EE2) on the histomorphometry and receptor expression (androgen receptor (AR) and estrogen receptor alpha (ERα) in gerbil ovaries (Meriones unguiculatus) during aging. Experimental groups included: control, vehicle (mineral oil), EE2: 15 µg/kg/day from gestational days 18-22, EE2/Pe: EE2 from days 18-22 and 300 mg/kg of pequi oil from days 18-26, and Pe: pequi oil only, via gavage. Female offspring were euthanized at 12 months, and ovaries were collected, processed histologically, and sectioned. Histological sections were stained with hematoxylin-eosin to analyze the superficial epithelium height and the tunica albuginea thickness. Immunohistochemistry for AR and ERα was performed, and the percentage of positive nuclei for these receptors was quantified in the theca interna, granulosa cells within follicles, and the interstitial gland. Data were analyzed using analysis of variance (ANOVA), Tukey's, and Kruskal-Wallis tests. The data revealed a significant decrease (p < 0.05) in the thickness of the tunica albuginea in the EE2 group, whereas this thickness was increased in the EE2/Pe and Pe groups. Epithelial height was lower in the EE2 group and higher in the EE2/Pe group. No significant changes in AR immunoreactivity were observed. In multilaminar follicles, ERα immunostaining was elevated in granulosa cells in the Pe group and in theca cells of the EE2 group. Additionally, the interstitial gland in the Pe group showed an increase in ERα expression. Pequi oil exposure upregulated ERα more markedly than AR during folliculogenesis and in interstitial cells, suggesting endocrine-modulating potential and relevance for ovarian regulation during aging.

Evaluation of Reference Gene Stability for Investigations of Intracellular Signalling in Human Cancer and Non-Malignant Mesenchymal Stromal Cells

BACKGROUND

Real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) is a powerful tool for analysing target gene expression in biological samples. To achieve reliable results by RT-qPCR, the most stable reference genes must be selected for proper data normalisation, particularly when comparing cells of different types. We aimed to choose the least variable candidate reference genes among eight housekeeping genes tested within a set of human cancer cell lines (HeLa, MCF-7, SK-UT-1B, A549, A431, SK-BR-3), as well as four lines of normal, non-malignant mesenchymal stromal cells (MSCs) of different origins.

METHODS

The reference gene stability was evaluated using four algorithms (BestKeeper, NormFinder, geNorm and the comparative ΔCt method) and ranked with the RefFinder web-based tool.

RESULTS

We found increased variability in the housekeeping genes' expression in the cancer cell lines compared to that in normal MSCs. POP4 and GAPDH were identified as the most suitable reference genes in cancer cells, while 18S and B2M were the most suitable in MSCs. POP4 and EIF2B1 were shown to be the least variable genes when analysing normal and cancer cell lines together. Epidermal growth factor receptor (EGFR) mRNA relative expression was normalised by the three most stable or three least stable reference genes to demonstrate the reliability of reference genes validation.

CONCLUSION

We analysed and selected stable reference genes for RT-qPCR analysis in the wide panel of cancer cell lines and MSCs. The study provides a reliable tool for future research concerning the expression of genes involved in various intracellular signalling pathways and emphasises the need for careful selection of suitable references before analysing target gene expression.

Female Reproductive Systems: Hormone Dependence and Receptor Expression

The female reproductive system which consists of the ovaries, uterus (myometrium, endometrium), Fallopian tubes, cervix and vagina is exquisitely sensitive to the actions of steroid hormones. The ovaries play a key role in the synthesis of bioactive steroids (oestrogens, androgens, progestins) that act both within the tissue (intracrine/paracrine) as well as on other reproductive organs following release into the blood stream (endocrine action). Sex steroid receptors encoded by the oestrogen (ESR1, ESR2), progesterone (PR) and androgen (AR) receptor genes, which are members of the superfamily of ligand activated transcription factors are widely expressed within these tissues. These receptors play critical role(s) in regulation of cell proliferation, ovulation, endometrial receptivity, myometrial cell function and inflammatory cell infiltration. Our understanding of their importance has been informed by studies on human tissues and cells, which have employed immunohistochemistry as well as a wide range of molecular and genetic methods to identify which processes are dependent steroid ligand activation. The development of mice with targeted deletions of each of these receptors has provided complementary data that has extended our appreciation of cell-cell interactions in the fine tuning of reproductive tissue function. This large body of work has formed the basis of new and improved therapeutics to treat conditions such as infertility.

ERβ Regulation of Gonadotropin Responses during Folliculogenesis

Gonadotropins are essential for regulating ovarian development, steroidogenesis, and gametogenesis. While follicle stimulating hormone (FSH) promotes the development of ovarian follicles, luteinizing hormone (LH) regulates preovulatory maturation of oocytes, ovulation, and formation of corpus luteum. Cognate receptors of FSH and LH are G-protein coupled receptors that predominantly signal through cAMP-dependent and cAMP-independent mechanisms that activate protein kinases. Subsequent vital steps in response to gonadotropins are mediated through activation or inhibition of transcription factors required for follicular gene expression. Estrogen receptors, classical ligand-activated transcriptional regulators, play crucial roles in regulating gonadotropin secretion from the hypothalamic-pituitary axis as well as gonadotropin function in the target organs. In this review, we discuss the role of estrogen receptor β (ERβ) regulating gonadotropin response during folliculogenesis. Ovarian follicles in Erβ knockout (Erβ^KO) mutant female mice and rats cannot develop beyond the antral state, lack oocyte maturation, and fail to ovulate. Theca cells (TCs) in ovarian follicles express LH receptor, whereas granulosa cells (GCs) express both FSH receptor (FSHR) and LH receptor (LHCGR). As oocytes do not express the gonadotropin receptors, the somatic cells play a crucial role during gonadotropin induced oocyte maturation. Somatic cells also express high levels of estrogen receptors; while TCs express ERα and are involved in steroidogenesis, GCs express ERβ and are involved in both steroidogenesis and folliculogenesis. GCs are the primary site of ERβ-regulated gene expression. We observed that a subset of gonadotropin-induced genes in GCs, which are essential for ovarian follicle development, oocyte maturation and ovulation, are dependent on ERβ. Thus, ERβ plays a vital role in regulating the gonadotropin responses in ovary.

Constitutive expression of Steroidogenic factor-1 (NR5A1) disrupts ovarian functions, fertility, and metabolic homeostasis in female mice

Steroid hormones regulate various aspects of physiology, from reproductive functions to metabolic homeostasis. Steroidogenic factor-1 (NR5A1) plays a central role in the development of steroidogenic tissues and their ability to produce steroid hormones. Inactivation of Nr5a1 in the mouse results in a complete gonadal and adrenal agenesis, absence of gonadotropes in the pituitary and impaired development of ventromedial hypothalamus, which controls glucose and energy metabolism. In this study, we set out to examine the consequences of NR5A1 overexpression (NR5A1+) in the NR5A1-positive cell populations in female mice. Ovaries of NR5A1+ females presented defects such as multi-oocyte follicles and an accumulation of corpora lutea. These females were hyperandrogenic, had irregular estrous cycles with persistent metestrus and became prematurely infertile. Furthermore, the decline in fertility coincided with weight gain, increased adiposity, hypertriglyceridemia, hyperinsulinemia, and impaired glucose tolerance, indicating defects in metabolic functions. In summary, excess NR5A1 expression causes hyperandrogenism, disruption of ovarian functions, premature infertility, and disorders of metabolic homeostasis. This NR5A1 overexpression mouse provides a novel model for studying not only the molecular actions of NR5A1, but also the crosstalk between endocrine, reproductive, and metabolic systems.

Indel mutations within the bovine HSD17B3 gene are significantly associated with ovary morphological traits and mature follicle number

Given the intensive selection for increased milk production, it is imperative that the problem of declining fertility in dairy cows be reversed. In female mammals their reproductive traits and functioning is controlled by a finely tuned process balancing estrogens and androgens, in which androgens (e.g., testosterone) as a precursor substance can participate in estrogen synthesis by activating 17β-hydroxysteroid dehydrogenase (17betaHSD). Being a key catalyst for testosterone synthesis, we hypothesized HSD17B3 gene is involved in the ovary's development and thereby capable of influencing cows' fecundity. Herein, to investigate the relationship between polymorphisms of the HSD17B3 gene and cow fertility, we characterized three insertion/deletion (indels) polymorphisms of this gene in 1110 healthy bovine ovaries. Their respective minimum allelic frequency (MAF) ranged from 0.180 to 0.482. For the ovary morphological traits, correlations revealed that both P1-D_15-bp and P4-D_19-bp demonstrated significant associations with ovarian height (P = 0.007 and 0.004, respectively), while P5-I_5-bp was found to be significantly associated with the ovarian weight (P = 0.024). For ovarian volume, a significant correlation was uncovered between it and both polymorphisms of P4-D_19-bp (P = 0.036) and P5-I_5-bp (P = 0.045). Cows with either the DD genotype of P4-D_19-bp or P5-I_5-bp tended to have greater ovarian volume, a result consistent with their relationship to ovarian weight (P5-I_5-bp) or height (P4-D_19-bp). For the mature follicle traits, polymorphisms of P4-D_19-bp were found significantly associated with the number of mature follicles (P = 0.045). Furthermore, expression levels of HSD17B3 differed significantly between the maximal and minimum groups of ovarian weight or volume, and the transcription factors GATA-1 and USF were predicted to bind P1-D_15-bp and P4-D_19-bp, respectively. This suggested the detected intron mutations could affect HSD17B3's transcription by regulating the binding of transcription factors, thereby affecting ovarian weight and other reproductive traits. As a potential effective molecular marker loci significantly related to traits of ovary and follicle, these three indels could be used in practical molecular marker-assisted selection (MAS) breeding programs, to optimize female fertility and enhance economic efficiency in the dairy cow industry.

Deficiency in insulin-like growth factors signalling in mouse Leydig cells increase conversion of testosterone to estradiol because of feminization

AIM

A growing body of evidence pointed correlation between insulin-resistance, testosterone level and infertility, but there is scarce information about mechanisms. The aim of this study was to identify the possible mechanism linking the insulin-resistance with testosterone-producing-Leydig-cells functionality.

METHODS

We applied in vivo and in vitro approaches. The in vivo model of functional genomics is represented by INSR/IGF1R-deficient-testosterone-producing Leydig cells obtained from the prepubertal (P21) and adult (P80) male mice with insulin + IGF1-receptors deletion in steroidogenic cells (Insr/Igf1r-DKO). The in vitro model of INSR/IGF1R-deficient-cell was mimicked by blockade of insulin/IGF1-receptors on the primary culture of P21 and P80 Leydig cells.

RESULTS

Leydig-cell-specific-insulin-resistance induce the development of estrogenic characteristics of progenitor Leydig cells in prepubertal mice and mature Leydig cells in adult mice, followed with a dramatic reduction of androgen phenotype. Level of androgens in serum, testes and Leydig cells decrease as a consequence of the dramatic reduction of steroidogenic capacity and activity as well as all functional markers of Leydig cell. Oppositely, the markers for female-steroidogenic-cell differentiation and function increase. The physiological significances are the higher level of testosterone-to-estradiol-conversion in double-knock-out-mice of both ages and few spermatozoa in adults. Intriguingly, the transcription of pro-male sexual differentiation markers Sry/Sox9 increased in P21-Leydig-cells, questioning the current view about the antagonistic genetic programs underlying gonadal sex determination.

CONCLUSION

The results provide new molecular mechanisms leading to the development of the female phenotype in Leydig cells from Insr/Igf1r-DKO mice and could help to better understand the correlation between insulin resistance, testosterone and male (in)fertility.

Dysregulation of hypothalamic-pituitary estrogen receptor α-mediated signaling causes episodic LH secretion and cystic ovary

Polycystic ovary syndrome (PCOS) is a hypothalamic-pituitary-gonadal (HPG) axis disorder. PCOS symptoms most likely result from a disturbance in the complex feedback regulation system of the HPG axis, which involves gonadotrophic hormones and ovarian steroid hormones. However, the nature of this complex and interconnecting feedback regulation makes it difficult to dissect the molecular mechanisms responsible for PCOS phenotypes. Global estrogen receptor α (ERα) knockout (KO) mice exhibit a disruption of the HPG axis, resulting in hormonal dysregulation in which female ERα KO mice have elevated levels of serum estradiol (E2), testosterone, and LH. The ERα KO females are anovulatory and develop cystic hemorrhagic ovaries that are thought to be due to persistently high circulating levels of LH from the pituitary. However, the role of ERα in the pituitary is still controversial because of the varied phenotypes reported in pituitary-specific ERα KO mouse models. Therefore, we developed a mouse model where ERα is reintroduced to be exclusively expressed in the pituitary on the background of a global ERα-null (PitERtgKO) mouse. Serum E2 and LH levels were normalized in PitERtgKO females and were comparable to wild-type serum levels. However, the ovaries of PitERtgKO adult mice displayed a more overt cystic and hemorrhagic phenotype when compared with ERα KO littermates. We determined that anomalous sporadic LH secretion caused the severe ovarian phenotype of PitERtgKO females. Our observations suggest that pituitary ERα is involved in the estrogen negative feedback regulation, whereas hypothalamic ERα is necessary for the precise control of LH secretion. Uncontrolled, irregular LH secretion may be the root cause of the cystic ovarian phenotype with similarities to PCOS.-Arao, Y., Hamilton, K. J., Wu, S.-P., Tsai, M.-J., DeMayo, F. J., Korach, K. S. Dysregulation of hypothalamic-pituitary estrogen receptor α-mediated signaling causes episodic LH secretion and cystic ovary.

Estrogen Hormone Biology

The hormone estrogen is involved in both female and male reproduction, as well as numerous other biological systems including the neuroendocrine, vascular, skeletal, and immune systems. Therefore, it is also implicated in many different diseases and conditions such as infertility, obesity, osteoporosis, endometriosis, and a variety of cancers. Estrogen works through its two distinct nuclear receptors, estrogen receptor alpha (ERα) and estrogen receptor beta (ERβ). Various transcriptional regulation mechanisms have been identified as the mode of action for estrogen, mainly the classical mechanism with direct DNA binding but also a nongenomic mode of action and one using tethered or indirect binding. The expression profiles of ERα and ERβ are unique with the primary sites of ERα expression being the uterus and pituitary gland and the main site of ERβ expression being the granulosa cells of the ovary. Mouse models with knockout or mutation of Esr1 and Esr2 have furthered our understanding of the role of each individual receptor plays in physiology. From these studies, it is known that the primary roles for ERα are in the uterus and neuroendocrine system, as female mice lacking ERα are infertile due to impaired ovarian and uterine function, whereas female mice lacking ERβ are subfertile due to ovarian defects. The development of effective therapies for estrogen-related diseases has relied on an understanding of the physiological roles and mechanistic functionalities of ERα and ERβ in human health and disease.

Toying with fate: Redirecting the differentiation of adrenocortical progenitor cells into gonadal-like tissue

Cell fate decisions are integral to zonation and remodeling of the adrenal cortex. Animal models exhibiting ectopic differentiation of gonadal-like cells in the adrenal cortex can shed light on the molecular mechanisms regulating steroidogenic cell fate. In one such model, prepubertal gonadectomy (GDX) of mice triggers the formation of adrenocortical neoplasms that resemble luteinized ovarian stroma. Transcriptomic analysis and genome-wide DNA methylation mapping have identified genetic and epigenetic markers of GDX-induced adrenocortical neoplasia. Members of the GATA transcription factor family have emerged as key regulators of cell fate in this model. Expression of Gata4 is pivotal for the accumulation of gonadal-like cells in the adrenal glands of gonadectomized mice, whereas expression of Gata6 limits the spontaneous and GDX-induced differentiation of gonadal-like cells in the adrenal cortex. Additionally, Gata6 is essential for proper development of the adrenal X-zone, a layer analogous to the fetal zone of the human adrenal cortex. The relevance of these observations to developmental signaling pathways in the adrenal cortex, to other animal models of altered adrenocortical cell fate, and to human diseases is discussed.

Obesity-induced infertility and hyperandrogenism are corrected by deletion of the insulin receptor in the ovarian theca cell

Women with polycystic ovary syndrome (PCOS) exhibit elevated androgen levels, oligoanovulation, infertility, and insulin resistance in metabolic tissues. The aims of these studies were to determine the role of insulin signaling in the development and function of ovarian theca cells and the pathophysiologic effects of hyperinsulinism on ovarian function in obesity. We disrupted the insulin receptor (IR) gene specifically in the theca-interstitial (TI) cells of the ovaries (Cyp17IRKO). No changes in reproductive development or function were observed in lean Cyp17IRKO female mice, suggesting that insulin signaling in TI cell is not essential for reproduction. However, when females were fed a high-fat diet, diet-induced obesity (DIO) wild-type (DIO-WT) mice were infertile and experienced increased circulating testosterone levels, whereas DIO-Cyp17IRKO mice exhibited improved fertility and testosterone levels comparable to those found in lean mice. The levels of phosphorylated IRS1 and CYP17 protein were higher in the ovary of DIO-WT compared with DIO-Cyp17IRKO or lean mice. Ex vivo studies using a whole ovary culture model demonstrated that insulin acts independently or additively with human chorionic gonadotropin to enhance androstenedione secretion. These studies reveal the causal pathway linking hyperinsulinism with ovarian hyperandrogenism and the infertility of obesity.

Effect of nutrition on plasma lipid profile and mRNA levels of ovarian genes involved in steroid hormone synthesis in Hu sheep during luteal phase

Ovarian steroid hormones regulate follicular growth and atresia. This study aims to determine whether key ovarian sterol-regulatory genes are differentially expressed in Hu sheep under different short-term nutritional regimens. Estrus was synchronized using intravaginal progestagen sponges. The ewes were assigned randomly to 3 groups. On d 6 to 12 of their estrous cycle, the control (CON) group received a maintenance diet (1.0×M), the supplemented (SUP) group received 1.5×M, and the restricted (R) group received 0.5×M. On d 7 to 12, blood samples were taken. The sheep were slaughtered at the end of the treatment, and their organs and ovaries were collected. The plasma concentrations of urea (P<0.01), total cholesterol (P<0.01), low-density lipoprotein cholesterol (P<0.01), NEFA (P<0.01), FSH (P<0.05), and estradiol (P<0.05) increased with decreasing dietary intake, whereas plasma triglyceride (P<0.01) and triiodothyronine (T3) concentrations decreased (P<0.05). The ewes in the R group had higher spleen weight and percentage of spleen to BW and lower liver and small intestine weights and percentage of liver/stomach to BW than the SUP group ewes (P<0.05). Nutritional restriction decreased the cytochrome p450 (CYP17A1) and estrogen receptor 1 (ESR1) mRNA expression (P<0.05) and increased the cytochrome p450 aromatase (CYP19A1) mRNA expression (P<0.05) in follicles>2.5 mm. Follicle size affected the mRNA expression of very low density lipoprotein receptor (VLDLR), estrogen receptor 2 (ESR2), FSH receptor (FSHR), CYP17A1, and CYP19A1 (P<0.05). In conclusion, we suggest that a potential mechanism by which short-term negative energy balance inhibits follicular growth may involve responses to disrupted reproductive hormone concentrations and influenced the intrafollicular expression of CYP17A1, CYP19A1, and ESR1. This result may be due to increased plasma urea and lipid concentrations.

Postnatal development of the endocrine pancreas in mice lacking functional GABAB receptors

Adult mice lacking functional GABAB receptors (GABAB1KO) have glucose metabolism alterations. Since GABAB receptors (GABABRs) are expressed in progenitor cells, we evaluated islet development in GABAB1KO mice. Postnatal day 4 (PND4) and adult, male and female, GABAB1KO, and wild-type littermates (WT) were weighed and euthanized, and serum insulin and glucagon was measured. Pancreatic glucagon and insulin content were assessed, and pancreas insulin, glucagon, PCNA, and GAD65/67 were determined by immunohistochemistry. RNA from PND4 pancreata and adult isolated islets was obtained, and Ins1, Ins2, Gcg, Sst, Ppy, Nes, Pdx1, and Gad1 transcription levels were determined by quantitative PCR. The main results were as follows: 1) insulin content was increased in PND4 GABAB1KO females and in both sexes in adult GABAB1KOs; 2) GABAB1KO females had more clusters (<500 μm(2)) and less islets than WT females; 3) cluster proliferation was decreased at PND4 and increased in adult GABAB1KO mice; 4) increased β-area at the expense of the α-cell area was present in GABAB1KO islets; 5) Ins2, Sst, and Ppy transcription were decreased in PND4 GABAB1KO pancreata, adult GABAB1KO female islets showed increased Ins1, Ins2, and Sst expression, Pdx1 was increased in male and female GABAB1KO islets; and 6) GAD65/67 was increased in adult GABAB1KO pancreata. We demonstrate that several islet parameters are altered in GABAB1KO mice, further pinpointing the importance of GABABRs in islet physiology. Some changes persist from neonatal ages to adulthood (e.g., insulin content in GABAB1KO females), whereas other features are differentially regulated according to age (e.g., Ins2 was reduced in PND4, whereas it was upregulated in adult GABAB1KO females).

Effects of aromatase or estrogen receptor gene deletion on masculinization of the principal nucleus of the bed nucleus of the stria terminalis of mice

The principal nucleus of the bed nucleus of the stria terminalis (BNSTp) is a sexually dimorphic nucleus, and the male BNSTp is larger and has more neurons than the female BNSTp. To assess the roles of neuroestrogen synthesized from testicular androgen by brain aromatase in masculinization of the BNSTp, we performed morphometrical analyses of the adult BNSTp in aromatase knockout (ArKO), estrogen receptor-α knockout (αERKO), and estrogen receptor-β knockout (βERKO) mice and their respective wild-type littermates. In wild-type littermates, the BNSTp of males had a larger volume and greater numbers of neuronal and glial cells than did that of females. The volume and neuron number of the BNSTp in ArKO and αERKO males and glial cell number of the BNSTp in αERKO males were significantly smaller than those of wild-type male littermates, and they were not significantly different from those in female mice with either gene knockout. In contrast, there was no significant morphological difference in the BNSTp between βERKO and wild-type mice. Next, we examined the BNSTp of ArKO males subcutaneously injected with estradiol benzoate (EB) on postnatal days 1, 2, and 3 (1.5 μg/day). EB-treated ArKO males had a significantly greater number of BNSTp neurons than did oil-treated ArKO males. The number of BNSTp neurons in EB-treated ArKO males was comparable to that in wild-type males. These findings suggested that masculinization of the BNSTp in mice involves the actions of neuroestrogen that was synthesized by aromatase and that this estrogen mostly binds to ERα during the postnatal period.

Ex3αERKO male infertility phenotype recapitulates the αERKO male phenotype

Disruption of the Esr1 gene encoding estrogen receptor α (ERα) by insertion of a neomycin resistance gene (neo) into exon 2 (αERKO mice) was shown previously to cause infertility in male mice. While full-length ERα protein was not expressed in αERKO mice, alternative splicing resulted in the low-level expression of a truncated form lacking the N-terminus A/B domain and containing the DNA- and ligand-binding domains. Thus, it was unclear whether the reproductive phenotype in αERKO males was only due to the lack of full-length ERα or was affected by the presence of the variant ERα isoform. The present study examined male mice with deletion of exon 3 of Esr1 gene, lacking the DNA-binding domain, and null for ERα (Ex3αERKO). Dilation of some seminiferous tubules was apparent in male Ex3αERKO mice as early as postnatal day 10 and was pronounced in all tubules from day 20 onward. At 6 weeks of age, sperm numbers and sperm motility were lower in Ex3αERKO mice than in wild-type (WT) mice, and the rete testis and efferent ductules were dilated. Mating studies determined that adult Ex3αERKO males were infertile and failed to produce copulatory plugs. Serum testosterone levels and Hsd17b3 and Cyp17a1 transcript levels were significantly higher, but serum estradiol, progesterone, LH, and FSH levels and Cyp19a1 transcript levels were not significantly different from those in WT mice. These results confirm and extend those seen in other studies on male mice with deletion of exon 3 of Esr1 gene. In addition, the reproductive phenotype of male Ex3αERKO mice recapitulated the phenotype of αERKO mice, strongly suggesting that the αERKO male infertility was not due to the presence of the DNA-binding domain in the truncated form of ERα and that full-length ERα is essential for maintenance of male fertility.

Developmental exposures of male rats to soy isoflavones impact Leydig cell differentiation

Testicular Leydig cells, which are the predominant source of the male sex steroid hormone testosterone, express estrogen receptors (ESRs) and are subject to regulation by estrogen. Following ingestion, the two major isoflavones in soybeans, genistin and daidzin, are hydrolyzed by gut microflora to form genistein and daidzein, which have the capacity to bind ESRs and affect gene expression. Thus, the increasing use of soy-based products as nondairy sources of protein has raised concerns about the potential of these products to cause reproductive toxicity. In the present study, perinatal exposure of male rats to isoflavones induced proliferative activity in Leydig cells. Isoflavones have the capacity to act directly as mitogens in Leydig cells, because genistein treatment induced Leydig cell division in vitro. Genistein action regulating Leydig cell division involved ESRs, acting in concert with signaling molecules in the transduction pathway mediated by protein kinase B (AKT) and mitogen-activated protein kinase (MAPK). Enhanced proliferative activity in the prepubertal period increased Leydig cell numbers, which alleviated deficits in androgen biosynthesis and/or augmented serum and testicular testosterone concentrations in adulthood. Together, these observations indicate that the perinatal exposures of male rats to isoflavones affected Leydig cell differentiation, and they imply that including soy products in the diets of neonates has potential implications for testis function.

Lack of functional GABA(B) receptors alters GnRH physiology and sexual dimorphic expression of GnRH and GAD-67 in the brain

GABA, the main inhibitory neurotransmitter, acts through GABA(A/C) and GABA(B) receptors (GABA(B)Rs); it is critical for gonadotropin regulation. We studied whether the lack of functional GABA(B)Rs in GABA(B1) knockout (GABA(B1)KO) mice affected the gonadotropin axis physiology. Adult male and female GABA(B1)KO and wild-type (WT) mice were killed to collect blood and tissue samples. Gonadotropin-releasing hormone (GnRH) content in whole hypothalami (HT), olfactory bulbs (OB), and frontoparietal cortexes (CT) were determined (RIA). GnRH expression by quantitative real-time PCR (qRT-PCR) was evaluated in preoptic area-anterior hypothalamus (POA-AH), medial basal-posterior hypothalamus (MBH-PH), OB, and CT. Pulsatile GnRH secretion from hypothalamic explants was measured by RIA. GABA, glutamate, and taurine contents in HT and CT were determined by HPLC. Glutamic acid decarboxylase-67 (GAD-67) mRNA was measured by qRT-PCR in POA-AH, MBH-PH, and CT. Gonadotropin content, serum levels, and secretion from adenohypophyseal cell cultures (ACC) were measured by RIA. GnRH mRNA expression was increased in POA-AH of WT males compared with females; this pattern of expression was inversed in GABA(B1)KO mice. MBH-PH, OB, and CT did not follow this pattern. In GABA(B1)KO females, GnRH pulse frequency was increased and GABA and glutamate contents were augmented. POA-AH GAD-67 mRNA showed the same expression pattern as GnRH mRNA in this area. Gonadotropin pituitary contents and serum levels showed no differences between genotypes. Increased basal LH secretion and decreased GnRH-stimulated gonadotropin response were observed in GABA(B1)KO female ACCs. These results support the hypothesis that the absence of functional GABA(B)Rs alters GnRH physiology and critically affects sexual dimorphic expression of GnRH and GAD-67 in POA-AH.

Increased exposure to estrogens disturbs maturation, steroidogenesis, and cholesterol homeostasis via estrogen receptor alpha in adult mouse Leydig cells

Deteriorated male reproductive health has been connected to overexposure to estrogens or to imbalanced androgen-estrogen ratio. Transgenic male mice expressing human aromatase (AROM(+) mice) serve as an apt model for the study of the consequences of an altered androgen-estrogen ratio. Our previous studies with AROM(+) mice showed that low androgen levels together with high estrogen levels result in cryptorchidism and infertility. In the present study, the AROM(+) mice were shown to have severe abnormalities in the structure and function of Leydig cells before the appearance of spermatogenic failure. Decreased expression of adult-type Leydig cell markers (Ptgds, Vcam1, Insl3, Klk21, -24 and -27, Star, Cyp17a1, and Hsd17b3) indicated an immature developmental stage of the Leydig cells, which appears to be the first estrogen-dependent alteration. Genes involved in steroidogenesis (Star, Cyp17a1, and Hsd17b3) were suppressed despite normal LH levels. The low expression level of kallikreins 21, 24, and 27 potentially further inhibited Leydig cell function via remodeling extracellular matrix composition. In connection with disrupted steroidogenesis, Leydig cells showed enlarged mitochondria, a reduced amount of smooth endoplasmic reticulum, and an accumulation of cholesterol and precursors for cholesterol synthesis. The results of studies with AROM(+) mice crossed with estrogen receptor alpha or beta (ERalpha and ERbeta, respectively) knockout mice lead to the conclusion that the structural and functional disorders caused by estrogen exposure were mediated via ERalpha, whereas ERbeta was not involved.

Estrogen receptor beta is required for optimal cAMP production in mouse granulosa cells

Granulosa cells of preovulatory follicles differentiate in response to FSH, and this differentiation is augmented by estradiol. We have previously shown that FSH-mediated granulosa cell differentiation requires functional estrogen receptor-beta (ERbeta) by demonstrating that the granulosa cells of ERbeta(-/-) FSH-treated mice are unable to maximally induce expression of the LH receptor (an indicator of granulosa cell differentiation) compared with ERbeta(+/+) controls. As a result, FSH-primed ERbeta(-/-) granulosa cells exhibit a reduced response to a subsequent ovulatory dose of LH. In this study, we further characterized the attenuated response of ERbeta(-/-) granulosa cells to stimulation by LH and FSH using isolated mouse granulosa cells and primary granulosa cell cultures. We observed a 50% reduction in cAMP levels in cultured ERbeta(-/-) granulosa cells exposed to LH compared with ERbeta(+/+) controls. We also observed an attenuated genomic response in granulosa cells isolated from FSH-primed ERbeta(-/-) mice compared with ERbeta(+/+) controls. Our data indicate that this attenuated response may result from inadequate levels of cAMP, because cAMP levels in cultured ERbeta(-/-) granulosa cells exposed to forskolin were approximately 50% lower than in ERbeta(+/+) granulosa cells. Phosphorylation of cAMP regulatory element binding protein, an indicator of protein kinase A activity, was also reduced in FSH-treated ERbeta(-/-) granulosa cells compared with ERbeta(+/+) controls. These are the first data to indicate that ERbeta plays a role in the induction of the cAMP pathway in mouse granulosa cells and that disruption of proper ERbeta signaling associated with this pathway may cause negative effects on ovulation and fertility.

The PDGF signaling pathway controls multiple steroid-producing lineages

The platelet-derived growth factor (PDGF) signaling pathway regulates numerous lineages of mesenchymal cell origin during development and in the adult. The transcriptional targets of this pathway have been shown to be required in several PDGF-dependent processes, but the roles of these targets in specific tissues is just beginning to be identified. In this study, we show that five different PDGF target genes are essential for male and/or female fertility. Mutations in each of these five different genes lead to defects in the steroid-producing cells in the testis and/or ovary and altered hormone production, suggesting that the PDGF pathway controls steroidogenesis through these genes in both sexes. Furthermore, conditional mutations of both PDGF receptors revealed a requirement in steroid-producing cells in multiple organs, including the testis, ovary, and adrenal cortex. Therefore, PDGF signaling may constitute a common mechanism in the control of multiple steroidogenic lineages.

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

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.