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

Proteomic analysis of egg production peak and senescence in the ovaries of Taihe black-boned silky fowl (Gallus gallus domesticus Brisson)

BACKGROUND

The Taihe black-boned silky fowl, a distinguished indigenous breed of chicken, is renowned for its dual utility in both traditional medicinal and culinary applications. However, the breed faces significant challenges due to its suboptimal reproductive capabilities and a notably brief egg-laying period, which have impeded its broader development and cultivation. In this research endeavor, we employed an advanced, rapid DIA (Data independent acquisition) quantitative proteomics method on the Astral platform to meticulously analyze the ovarian proteome of these chickens. By analyzing the ovarian proteomic information of Taihe black-boned silky fowl during peak and decline egg-laying periods, we aim to identify potential reproductive candidate proteins and the molecular mechanisms underlying egg-laying decline. This could enable us to implement interventions to improve the reproductive efficiency of this valuable breed.

RESULT

In this study, a total of 8,281 proteins were identified within the ovarian proteome of the Taihe black-boned silky fowl. Among these, 303 proteins exhibited significant differential expression, with 98 proteins significantly up-regulated and 205 proteins significantly down-regulated. The functional annotation of these proteins illuminated their crucial roles in the steroid hormone synthesis pathways, which are pivotal during the peak of egg production. Furthermore, during the later stages of laying, there was a noticeable upregulation of proteins associated with inflammatory senescence and oxidative stress. This change suggests an increase in reproductive stress within the ovary, highlighting the physiological shifts that affect productivity as the chickens age.

CONCLUSION

This study identified key candidate protein markers in the Taihe black-boned silky fowl during critical phases of their reproductive cycle, specifically peak and late egg-laying periods. These findings contribute valuable new scientific insights that can be utilized for the breeding optimization and effective management of this unique breed. By elucidating the protein dynamics during different laying phases, the research offers potential strategies aimed at enhancing reproductive performance and extending the reproductive lifespan of the Taihe black-boned silky fowl. This could lead to significant improvements in both the sustainability and profitability of farming this indigenous breed.

Roles of estrogen and its receptors in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is an endocrine disorder characterized by abnormal steroid hormone levels in peripheral blood and poor-quality oocytes. In the ovary, androgen is produced by theca cells, and estrogen is produced by granulosa cells. Androgen is converted to estrogen in granulosa cells, with cytochrome P450 aromatase as the limiting enzyme during this process. Estrogen receptors (ER) include ER alpha, ER beta, and membrane receptor GPR30. Studies have demonstrated that the abnormal functions of estrogen and its receptors and estradiol synthesis-related enzymes are closely related to PCOS. In recent years, some estrogen-related drugs have made significant progress in clinical application for subfertility with PCOS, such as letrozole and clomiphene. This article will elaborate on the recent advances in PCOS caused by abnormal expression of estrogen and its receptors and the application of related targeted small molecule drugs in clinical research and treatment.

Transcriptome analysis during 4-vinylcyclohexene diepoxide exposure-induced premature ovarian insufficiency in mice

The occupational chemical 4-Vinylcyclohexene diepoxide (VCD) is a reproductively toxic environmental pollutant that causes follicular failure, leading to premature ovarian insufficiency (POI), which significantly impacts a woman's physical health and fertility. Investigating VCD's pathogenic mechanisms can offer insights for the prevention of ovarian impairment and the treatment of POI. This study established a mouse model of POI through intraperitoneal injection of VCD into female C57BL/6 mice for 15 days. The results were then compared with those of the control group, including a comparison of phenotypic characteristics and transcriptome differences, at two time points: day 15 and day 30. Through a comprehensive analysis of differentially expressed genes (DEGs), key genes were identified and validated some using RT-PCR. The results revealed significant impacts on sex hormone levels, follicle number, and the estrous cycle in VCD-induced POI mice on both day 15 and day 30. The DEGs and enrichment results obtained on day 15 were not as significant as those obtained on day 30. The results of this study provide a preliminary indication that steroid hormone synthesis, DNA damage repair, and impaired oocyte mitosis are pivotal in VCD-mediated ovarian dysfunction. This dysfunction may have been caused by VCD damage to the primordial follicular pool, impairing follicular development and aggravating ovarian damage over time, making it gradually difficult for the ovaries to perform their normal functions.

In-vitro generation of follicle-like structures from human germ cell-like cells derived from theca stem cell combined with ovarian somatic cells

BACKGROUND

The objective of this study was to induce the differentiation of human theca stem cells (hTSCs) into germ cell-like cells (hGCLCs) and assess their developmental progression following in vitro 3D culture with ovarian somatic cells within the follicle-like structures. To achieve this, the hTSCs were isolated from small antral follicles of three patients of varying ages and were then seeded in a differentiation medium for 40 days. The differentiated hGCLCs were subsequently aggregated with somatic ovarian cells (cumulus cells and hTSCs) in a ratio of 1:10 and cultured in a growth medium in a suspension culture dish. In addition to examining the morphologies, sizes, and viabilities of the differentiated hGCLCs, this study also analyzed the expression of DAZL and GDF9 proteins within the follicle-like structures.

RESULTS

After 12 days, the hTSCs began to differentiate into hGCLCs, with their shapes changing from spindle-shaped to spherical. The sizes of hGCLCs increased during the differentiation period (from 25 μm to 50 μm). The survival rate of the hGCLCs after differentiation and in vitro development in primordial follicle-like structures was 54%. Unlike hTSCs, which did not express the DAZL protein, the hGCLCs and follicle-like structures successfully expressed DAZL protein (P-value < 0.05). However, hGCLCs poorly expressed the GDF9 protein. Further, the culture of hGCLCs in primordial follicle-like structures significantly increased GDF9 expression (P-value < 0.05).

CONCLUSION

In conclusion, our study demonstrated that 3D cultures with ovarian somatic cells in follicle-like structures caused the successful differentiation of reproducible hGCLCs from hTSCs derived from three patients of different ages. Moreover, this method not only enhanced the in vitro development of hGCLCs but also presented a novel approach for co-culturing and developing in vitro oocyte like cells, ultimately leading to the production of artificial follicles.

Next-generation sequencing of 500 POI patients identified novel responsible monogenic and oligogenic variants

BACKGROUND

Premature ovarian insufficiency refers to the loss of ovarian function before 40 years of age. The etiology is heterogeneous, and genetic factors account for 20-25% of cases. However, how to transform genetic findings to clinical molecular diagnose remains a challenge. To identify potential causative variations for POI, a next generation sequencing panel with 28 known causative genes of POI was designed, and a large cohort of 500 Chinese Han patients was screened directly. Pathogenic evaluation of the identified variants and the phenotype analysis were performed according to monogenic or oligogenic variants.

RESULTS

A total of 14.4% (72/500) of the patients carried 61 pathogenic or likely pathogenic variants in 19 of the genes in the panel. Interestingly, 58 variants (95.1%, 58/61) were firstly identified in patients with POI. FOXL2 harbored the highest occurrence frequency (3.2%, 16/500), among whom presented with isolated ovarian insufficiency instead of blepharophimosis-ptosis-epicanthus inversus syndrome. Moreover, luciferase reporter assay confirmed variant p.R349G, which account for 2.6% of POI cases, impaired the transcriptional repressive effect of FOXL2 on CYP17A1. The novel compound heterozygous variants in NOBOX and MSH4 were confirmed by pedigree haplotype analysis, and digenic heterozygous variants in MSH4 and MSH5 were firstly identified. Furthermore, nine patients (1.8%, 9/500) with digenic or multigenic pathogenic variants presented with delayed menarche, early onset of POI and high prevalence of primary amenorrhea compared with those with monogenic variation(s).

CONCLUSIONS

The genetic architecture of POI has been enriched through the targeted gene panel in a large cohort of patients with POI. Specific variants in pleiotropic genes may result in isolated POI rather than syndromic POI, whereas oligogenic defects might have cumulative deleterious effects on the severity of POI phenotype.

Nasturtium officinale L. and metformin alleviate the estradiol- induced polycystic ovary syndrome with synergistic effects through modulation of Bax/Bcl-2/p53/caspase-3 signaling pathway and anti-inflammatory and anti-oxidative effects

Polycystic ovary syndrome (PCOS) is one of the most common causes of infertility in women, which is associated with metabolic, hereditary and hormonal disorders. The aim of this study was to evaluate the therapeutic effects of Nasturtium officinale L. (N. officinale) on biochemical and molecular parameters in estradiol-induced PCOS in rats. Seventy Wistar rats in 7 groups (n = 10) were randomly assigned to normal (NC), PCOS, metformin (MET - 300 mg/kg), N. officinale (50 and 100 mg/kg) and co-treatment with MET and N. officinale groups. After 21 days of treatment, biochemical parameters levels of estrogen, LH and FSH along with serum levels of (IL-6 and IL-1β cytokines) and serum antioxidant parameters (enzymatic activity of catalase and superoxide dismutase) were measured. Finally, by measuring the expression of apoptosis related genes (Bax/Bcl-2/p53/caspase-3) with the help of real-time PCR and the expression of p53 with the help of immunohistochemistry in ovarian cells. N. officinale modulates hormones through its hypothalamic-pituitary-gonadal pathway with its synergistic effects along with MET. Also, in co-treatment groups (MET and N. officinale), the activity of serum antioxidant enzymes increased and also the serum level of inflammatory cytokines decreased. N. officinale, along with MET, amplified the Bax/Bcl2/p53/caspase-3 pathways, which eventually increased the number of p53 positive cells. These findings indicate that N. officinale extract along with MET can improve the physiological function of the ovaries in PCOS-induced disorders. PRACTICAL APPLICATIONS: Polycystic ovary syndrome (PCOS) is one of the most common causes of infertility in women, which is associated with metabolic, hereditary and hormonal disorders. The extract of Nasturtium officinale L. was able to intensify mitochondrial apoptotic pathway in cystic follicles and prevent their formation. It seems that pro-drugs containing N. officinale along with effective commercial drugs in PCOS can help ovulation and fertility in woman with this disease.

Is letrozole during ovarian stimulation useful in breast cancer patients undergoing fertility preservation to reduce early luteal progesterone levels following GnRH-agonist trigger?

BACKGROUND

In absence of contraindication, breast cancer patients of reproductive age can undergo fertility preservation with controlled ovarian stimulation for oocyte/embryo cryopreservation before the administration of potentially gonadotoxic treatments. High hormonal levels induced by ovarian stimulation might have an adverse impact on hormone-positive breast cancer. Whether letrozole supplementation during ovarian stimulation (COSTLES) reduces serum progesterone levels after GnRHa trigger remains unknown. We aimed to determine whether COSTLES might be useful for breast cancer patients undergoing fertility preservation to reduce early luteal progesterone levels following GnRH-agonist (GnRHa)trigger.

METHODS

All women who underwent COS with GnRH antagonist protocol with GnRHa trigger were included. Serum progesterone level measured 12 h after GnRHa trigger was compared between patients undergoing COS with letrozole supplementation (COSTLES group) and patients undergoing COS without letrozole (Control group) for fertility preservation purposes.

RESULTS

A total of 246 patients were included, of which 84 patients (34.1%) in the COSTLES group and 162 patients (65.6%) in the Control group. All patients in the COSTLES group were BC patients (n = 84, 100%), while the Control group included 77 BC patients (47.5%). Patients in the two groups were comparable. The mean number of oocytes recovered and vitrified at metaphase 2 stage did not significantly differ between the two groups. Serum progesterone levels on the day after GnRHa trigger were significantly lower in the COSTLES group (8.6 ± 0.7 vs. 10.5 ± 0.5 ng/mL, respectively, p < 0.03), as well as serum E2 levels (650.3 ± 57.7 vs. 2451.4.0 ± 144.0 pg/mL, respectively, p < 0.01). However, the GnRHa-induced LH surge was significantly higher in in the COSTLES group (71.9 ± 4.6 vs. 51.2 ± 2.6 UI/L, respectively, p < 0.01).

CONCLUSIONS

Our results show that COSTLES for fertility preservation in breast cancer patients using GnRHa trigger reduces serum progesterone levels compared to ovarian stimulation without letrozole. These findings encourage the use of COSTLES in this context to decrease the potential deleterious effect of elevated hormonal levels on hormone-positive breast cancer.

Genome-Wide Identification of mRNAs, lncRNAs, and Proteins, and Their Relationship With Sheep Fecundity

The exploration of multiple birth-related genes has always been a significant focus in sheep breeding. This study aimed to find more genes and proteins related to the litter size in sheep. Ovarian specimens of Small Tail Han sheep (multiple births) and Xinji Fine Wool sheep (singleton) were collected during the natural estrus cycle. Transcriptome and proteome of ovarian specimens were analyzed. The transcriptome results showed that "steroid hormone biosynthesis" and "ovarian steroidogenesis" were significantly enriched, in which HSD17B1 played an important role. The proteome data also confirmed that the differentially expressed proteins (DEPs) were enriched in the ovarian steroidogenesis pathway, and the CYP17A1 was the candidate DEP. Furthermore, lncRNA MSTRG.28645 was highly expressed in Small Tailed Han sheep but lowly expressed in Xinji fine wool sheep. In addition, MSTRG.28645, a hub gene in the co-expression network between mRNAs and lncRNAs, was selected as one of the candidate genes for subsequent verification. Expectedly, the overexpression and interference of HSD17B1 and MSTRG.28645 showed a significant effect on hormone secretion in granulosa cells. Therefore, this study confirmed that HSD17B1 and MSTRG.28645 might be potential genes related to the fecundity of sheep. It was concluded that both HSD17B1 and MSTRG.28645 were critical regulators in the secretion of hormones that affect the fecundity of the sheep.

Effect of Supplementation of Zinc-Methionine on Egg Production, Semen Quality, Reproductive Hormones, and Hatchability in Broiler Breeders

A biological study was conducted to explore the effect of zinc-methionine (Zn-Met) supplementation on productive, reproductive, and immunological response in broiler breeders. Adult healthy 45-week breeder males (192) and females (288) were used in a completely randomized design. Birds were randomly divided into four treatments consisting of six replicates and fed basal diet (control, 40 mg/kg), basal diet supplemented with Zn-Met 20 (T1), 40 (T2), and 60 mg/kg (T3). There was no effect (P > 0.05) on body weight and feed consumption among the breeders due to the supplementation of organic Zn. The T3 group had significantly (P < 0.05) higher semen volume, sperm motility, concentration, and live sperm count. The seminal plasma calcium and alkaline phosphatase activity were higher (P < 0.05), and total cholesterol and aspartate transaminase levels were low in the T3 group. Birds fed with additional supplementation of Zn (60 mg/kg) had improved both cellular and humoral immunity. Throughout the experimental period, the hen day egg production was comparable (P > 0.05) among the experimental groups. Organic Zn-supplemented group showed significant difference in both the internal and external egg qualities-albumen, yolk index, and shell thickness. The higher dose of organic Zn-fed groups had a significant difference in estrogen and progesterone concentration, and the highest testosterone concentration was observed in the T2 group. Supplementary organic Zn had a significant effect on the concentration of Zn and Cu in the seminal plasma. Serum Zn and Cu concentration was significantly increased due to the supplementation of organic zinc in both male and female breeders. The fertility and hatchability percentage were higher (P < 0.05) in the T2 group. It could be concluded that the additional supplementation of organic Zn (zinc-methionine) at 40 mg/kg to the basal diet improved the reproductive performance in broiler breeders.

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.

Ovarian transcriptomic analysis of black Muscovy duck at the early, peak and late egg-laying stages

Ovarian development is a complex process involving many genes and pathways. A well-developed ovary is essential for poultry to keep high egg production and egg fertility. In order to better understand the mechanism of egg production performance, a comparative transcriptomic analysis was performed on ovaries of black Muscovy ducks at the early (BE), peak (BP) and late laying (BL) stages. 1683 DEGs were identified from BL-vs-BE, BL-vs-BP and BP-vs-BE, and the up-regulated genes were 41, 835, 260, the down-regulated genes were 60, 255, 730, respectively. Besides, there were 32, 20 and 424 DEGs co-expressed in the two comparison groups, and 11 DEGs were co-expressed in the three comparison groups. HOXA10, HtrA3, StAR, ZP2 and TAT were found to be involved in the regulation of ovarian development were significantly differentially expressed at different laying stages, which helped to regulate ovarian maturation and egg production. Moreover, we discovered several important functional pathways, such as steroid hormone biosynthesis and ovarian steroidogenesis, that appear to be much more active in the BP ovary compared to those of the BE and BL. Furthermore, 17 coding and 244 non-coding new transcripts were detected in the three comparison groups, the gene structures were optimized and the gene annotation informations were improved. These findings will provide a solid foundation on ovarian development in black Muscovy ducks and other poultry animals at different laying stages, and help to understand the complex molecular and cellular mechanisms of ovary.

Expression of NOTCH receptors and ligands and prognosis of hepatocellular carcinoma

Aim: To elucidate potential prognostic significance of NOTCH receptor and ligand expression in hepatocellular carcinoma. Materials & methods: NOTCH receptors and ligands were divided into increased and decreased expression groups by X-tile program. The association between NOTCH receptors/ligands and prognosis was analyzed by Kaplan-Meier method and log-rank test. Gene set enrichment analysis was performed to explore NOTCH receptors/ligands-related pathways via gsea-3.0. Results: DLL3 and DLL4 were independent prognostic factors for overall survival. Further studies showed that only DLL3 was significantly associated with tumor, node, metastasis stage. Gene set enrichment analysis analysis demonstrated that retinol metabolism, drug metabolism cytochrome P450 and tryptophan metabolism were significantly enriched in DLL3 expression phenotype. Conclusion: We demonstrate that DLL3 may be a prognostic biomarker in hepatocellular carcinoma.

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.

The evolution and possible role of two Sox8 genes during sex differentiation in Japanese flounder (Paralichthys olivaceus)

Sox8 genes, as members of the Sox family, have been studied widely in mammals. However, regulation of sox8 genes in teleosts has rarely been studied, and functional analysis of these genes in teleosts has rarely been performed. Here, two duplicates of sox8 genes were identified in Japanese flounder, Posox8a and Posox8b. The analysis of expression showed that Posox8a and Posox8b were expressed in Sertoli cells of the testis, indicating that they play important roles in development and functional maintenance of the testis. Positive selection and phylogenetic analysis found that both Posox8a and Posox8b underwent the purification selection during evolutionary and that sox8 was most likely to be the ancestor sox8a. These results suggested that both Posox8a and Posox8b had important biological functions after generation from three rounds of whole-genome duplication in Japanese flounder. The functional differentiation of Posox8a and Posox8b was verified using cell transfection and dual-luciferase reporter assays; Posox8a overexpression-promoted 3β-hydroxysteroid dehydrogenase expression and Posox8b overexpression-promoted cytochrome P450 aromatase (cyp19a1; P450arom) expression. Finally, combined with Posox8a and Posox8b expression analysis from 30 to 100 days after hatch, we speculated that Posox8a and Posox8b might participate in the process of sex differentiation and gonadogenesis by regulating sex hormone biosynthesis in the Japanese flounder. Our study is the first to demonstrate the possible mechanism of Posox8a and Posox8b in Japanese flounder sex differentiation and gonadogenesis, laying a solid foundation for functional studies of sox8 genes in teleosts.

Mammalian target of rapamycin/eukaryotic initiation factor 4F pathway regulates follicle growth and development of theca cells in mice

The aim of the present study was to clarify the roles of the mammalian target of rapamycin (mTOR) signalling pathway in follicular growth and development of thecal cells. Using in vivo-grown and in vitro-cultured ovaries, histological changes were evaluated using haematoxylin and eosin (HE) staining. Differentially expressed genes (DEGs) from 0 day post partum (d.p.p.) to 8 d.p.p. ovaries were screened by microarray and verified by quantitative real-time polymerase chain reaction. Forty-two DEGs related to cell proliferation and differentiation were screened out, with most DEGs being related to the to mTOR signalling pathway. Then, 3 d.p.p. ovaries were retrieved and used to verify the role of mTOR signalling in follicle and thecal cell development using its activators (Ras homologue enriched in brain (Rheb) and GTP) and inhibitor (rapamycin). The development of follicles and thecal cells was significantly impaired in ovaries cultured in vitro Day 3 to Day 8. In in vitro-cultured ovaries, Rheb and GTP (is 100ngmL^-1 Rheb and 500ngmL^-1 GTP for 48h) significantly increased follicle diameter, the percentage of primary and secondary follicles and the umber of thecal cells, and upregulated expression of mTOR, phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), eukaryotic initiation factor (eIF) 4F and cytochrome P450, family 17, subfamily A, polypeptide 1 (CYP17A1). Rapamycin (10nM rapamycin for 24h) had opposite effects to those of Rheb and GTP, and partly abrogated (significant) the effects of Rheb and GTP when added to the culture in combination with these drugs. Thus, mTOR signalling plays an important role in follicle growth and thecal cell development.

A transcriptomic comparison of theca and granulosa cells in chicken and cattle follicles reveals ESR2 as a potential regulator of CYP19A1 expression in the theca cells of chicken follicles

Previous studies have shown that theca and granulosa cell layers in follicles do not play the same roles in mammals and birds, especially regarding the synthesis of estrogen. The functions of these two cell types have been well characterized in cattle, but they remain unclear in chickens. To clarify this issue, a comparison of small yellow follicles (SYFs) in chickens and cattle at different follicular development stages was done by weighted gene co-expression network analysis (WGCNA). The modules obtained from WGCNA were used for further identification of the key genes associated with CYP19A1 expression. Module preservation analysis showed high similarity between cow_D (the follicular phase before the LH surge) and chicken_SYF (small yellow follicle between 6 and 8 mm in diameter) datasets, and 10 top hub genes highly associated with CYP19A1 expression in chicken SYFs were identified in each module. A comparison of the transcriptomes of theca and granulosa cells (TCs and GCs) between chicken SYFs and cattle follicles at the differentiation stage, as well as the aforementioned hub genes, revealed that ESR2 is a potential regulator of CYP19A1 expression in the theca cells of chicken SYFs. Furthermore, 197 cell-specific (179 in theca and 18 in granulosa) and 235 cell-biased expressed genes (196 in theca and 39 in granulosa) in chicken small yellow follicles were also identified by transcriptomic comparison of theca and granulosa cells.

Identification of candidate reference chemicals for in vitro steroidogenesis assays

The Endocrine Disruptor Screening Program (EDSP) is transitioning from traditional testing methods to integrating ToxCast/Tox21 in vitro high-throughput screening assays for identifying chemicals with endocrine bioactivity. The ToxCast high-throughput H295R steroidogenesis assay may potentially replace the low-throughput assays currently used in the EDSP Tier 1 battery to detect chemicals that alter the synthesis of androgens and estrogens. Herein, we describe an approach for identifying in vitro candidate reference chemicals that affect the production of androgens and estrogens in models of steroidogenesis. Candidate reference chemicals were identified from a review of H295R and gonad-derived in vitro assays used in methods validation and published in the scientific literature. A total of 29 chemicals affecting androgen and estrogen levels satisfied all criteria for positive reference chemicals, while an additional set of 21 and 15 chemicals partially fulfilled criteria for positive reference chemicals for androgens and estrogens, respectively. The identified chemicals included pesticides, pharmaceuticals, industrial and naturally-occurring chemicals with the capability to increase or decrease the levels of the sex hormones in vitro. Additionally, 14 and 15 compounds were identified as potential negative reference chemicals for effects on androgens and estrogens, respectively. These candidate reference chemicals will be informative for performance-based validation of in vitro steroidogenesis models.

Morphological and Molecular Aspects of In Vitro Culture of Preantral Follicles Derived from Vitrified Ovarian

Objective

This study aimed to evaluate the expression of the genes related to folliculo-genesis after vitrification of mouse ovarian tissues using a two-step in vitro culture.

Materials and Methods

In this experimental study, vitrified and non-vitrified ovaries from 7- day old (neonate) female mice were cultured using alpha-Minimum Essential Medium (α-MEM) supplemented with 5% fetal bovine serum (FBS) for 7 days. Morphology, surface area of ovaries and percentage of normal follicles were evaluated and compared in both groups. After one-week culture, in non-vitrified group, preantral follicles of cultured ovaries were isolated and cultured in a three-dimensional alginate culture system for 12 days. Then, the collected metaphase (M) II oocytes were inseminated with capacitated spermatozoa derived from 7-8-week old (adult) male NMRI mice. Follicular diameter, oocyte maturation, fertilization, embryo development and the expression of genes related to follicular development (Pcna, Fshr and Cyp17a1,) using real time reverse transcription-polymerase chain reaction (RT-PCR) were assessed at the end of last culture period in both groups.

Results

The ovarian area in vitrified group (162468.20 703.78) was less than non-vitrified group (297211.40 6671.71), while the percentage of preantral follicles in vitrified group (18.40%) was significantly lower than those of non-vitrified group (24.50%) on day 7 of culture (P<0.05). There were no significant differences between the two groups in terms of follicular diameter, expression of genes related to development of follicles, oocyte maturation, fertilization, as well as embryo development (P>0.05).

Conclusion

The results of this study showed that vitrification of ovarian tissue following in vitro culture had negative impact on the survival and development of follicles within the tissue. However, no significant alterations were observed in development, gene expression and hormonal production of in vitro culture of isolated follicles derived from vitrified ovarian tissues as compared to the non-vitrified samples.

Diethylstilbestrol administration inhibits theca cell androgen and granulosa cell estrogen production in immature rat ovary

Diethylstilbestrol (DES), a strong estrogenic compound, is well-known to affect the reproductive system. In this study, we investigated the effects of DES administration on gonadotropin levels and ovarian steroidogenesis in prepubertal rats. DES treatment acutely reduced serum LH levels, followed by a reduction in the expression of various steroidogenesis-related genes in theca cells. Serum FSH levels were almost unaffected by DES-treatment, even though Cyp19a1 expression was markedly reduced. Serum progesterone, testosterone and estradiol levels were also declined at this time. LH levels recovered from 12 h after DES-treatment and gradually increased until 96 h with a reduction of ERα expression observed in the pituitary. Steroidogenesis-related genes were also up-regulated during this time, except for Cyp17a1 and Cyp19a1. Consistent with observed gene expression pattern, serum testosterone and estradiol concentrations were maintained at lower levels, even though progesterone levels recovered. DES-treatment induced the inducible nitric oxide synthase (iNOS) in granulosa cells, and a nitric oxide generator markedly repressed Cyp19a1 expression in cultured granulosa cells. These results indicate that DES inhibits thecal androgen production via suppression of pituitary LH secretion and ovarian Cyp17a1 expression. In addition, DES represses Cyp19a1 expression by inducing iNOS gene expression for continuous inhibition of estrogen production in granulosa cells.

Role of cytochrome b5 in the modulation of the enzymatic activities of cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1)

Cytochrome b5 (cyt b5) is a small hemoprotein that plays a significant role in the modulation of activities of an important steroidogenic enzyme, cytochrome P450 17α-hydroxylase/17,20-lyase (P450 17A1, CYP17A1). Located in the zona fasciculata and zona reticularis of the adrenal cortex and in the gonads, P450 17A1 catalyzes two different reactions in the steroidogenic pathway; the 17α-hydroxylation and 17,20-lyase, in the endoplasmic reticulum of these respective tissues. The activities of P450 17A1 are regulated by cyt b5 that enhances the 17,20-lyase reaction by promoting the coupling of P450 17A1 and cytochrome P450 reductase (CPR), allosterically. Cyt b5 can also act as an electron donor to enhance the 16-ene-synthase activity of human P450 17A1. In this review, we discuss the many roles of cyt b5 and focus on the modulation of CYP17A1 activities by cyt b5 and the mechanisms involved.

The Pathogenesis of Polycystic Ovary Syndrome (PCOS): The Hypothesis of PCOS as Functional Ovarian Hyperandrogenism Revisited

Polycystic ovary syndrome (PCOS) was hypothesized to result from functional ovarian hyperandrogenism (FOH) due to dysregulation of androgen secretion in 1989-1995. Subsequent studies have supported and amplified this hypothesis. When defined as otherwise unexplained hyperandrogenic oligoanovulation, two-thirds of PCOS cases have functionally typical FOH, characterized by 17-hydroxyprogesterone hyperresponsiveness to gonadotropin stimulation. Two-thirds of the remaining PCOS have FOH detectable by testosterone elevation after suppression of adrenal androgen production. About 3% of PCOS have a related isolated functional adrenal hyperandrogenism. The remaining PCOS cases are mild and lack evidence of steroid secretory abnormalities; most of these are obese, which we postulate to account for their atypical PCOS. Approximately half of normal women with polycystic ovarian morphology (PCOM) have subclinical FOH-related steroidogenic defects. Theca cells from polycystic ovaries of classic PCOS patients in long-term culture have an intrinsic steroidogenic dysregulation that can account for the steroidogenic abnormalities typical of FOH. These cells overexpress most steroidogenic enzymes, particularly cytochrome P450c17. Overexpression of a protein identified by genome-wide association screening, differentially expressed in normal and neoplastic development 1A.V2, in normal theca cells has reproduced this PCOS phenotype in vitro. A metabolic syndrome of obesity-related and/or intrinsic insulin resistance occurs in about half of PCOS patients, and the compensatory hyperinsulinism has tissue-selective effects, which include aggravation of hyperandrogenism. PCOS seems to arise as a complex trait that results from the interaction of diverse genetic and environmental factors. Heritable factors include PCOM, hyperandrogenemia, insulin resistance, and insulin secretory defects. Environmental factors include prenatal androgen exposure and poor fetal growth, whereas acquired obesity is a major postnatal factor. The variety of pathways involved and lack of a common thread attests to the multifactorial nature and heterogeneity of the syndrome. Further research into the fundamental basis of the disorder will be necessary to optimally correct androgen levels, ovulation, and metabolic homeostasis.

Allopregnanolone as a mediator of affective switching in reproductive mood disorders

RATIONALE

Reproductive mood disorders, including premenstrual dysphoria (PMD) and postpartum depression (PPD), are characterized by affective dysregulation that occurs during specific reproductive states. The occurrence of illness onset during changes in reproductive endocrine function has generated interest in the role of gonadal steroids in the pathophysiology of reproductive mood disorders, yet the mechanisms by which the changing hormone milieu triggers depression in susceptible women remain poorly understood.

OBJECTIVES

This review focuses on one of the neurosteroid metabolites of progesterone - allopregnanolone (ALLO) - that acutely regulates neuronal function and may mediate affective dysregulation that occurs concomitant with changes in reproductive endocrine function. We describe the role of the "neuroactive" steroids estradiol and progesterone in reproductive endocrine-related mood disorders to highlight the potential mechanisms by which ALLO might contribute to their pathophysiology. Finally, using existing data, we test the hypothesis that changes in ALLO levels may trigger affective dysregulation in susceptible women.

RESULTS

Although there is no reliable evidence that basal ALLO levels distinguish those with PMD or PPD from those without, existing animal models suggest potential mechanisms by which specific reproductive states may unmask susceptibility to affective dysregulation. Consistent with these models, initially euthymic women with PMD and those with a history of PPD show a negative association between depressive symptoms and circulating ALLO levels following progesterone administration.

CONCLUSIONS

Existing animal models and our own preliminary data suggest that ALLO may play an important role in the pathophysiology of reproductive mood disorders by triggering affective dysregulation in susceptible women.

Pregnenolone co-treatment partially restores steroidogenesis, but does not prevent growth inhibition and increased atresia in mouse ovarian antral follicles treated with mono-hydroxy methoxychlor

Mono-hydroxy methoxychlor (mono-OH MXC) is a metabolite of the pesticide, methoxychlor (MXC). Although MXC is known to decrease antral follicle numbers, and increase follicle death in rodents, not much is known about the ovarian effects of mono-OH MXC. Previous studies indicate that mono-OH MXC inhibits mouse antral follicle growth, increases follicle death, and inhibits steroidogenesis in vitro. Further, previous studies indicate that CYP11A1 expression and production of progesterone (P4) may be the early targets of mono-OH MXC in the steroidogenic pathway. Thus, this study tested whether supplementing pregnenolone, the precursor of progesterone and the substrate for HSD3B, would prevent decreased steroidogenesis, inhibited follicle growth, and increased follicle atresia in mono-OH MXC-treated follicles. Mouse antral follicles were exposed to vehicle (dimethylsulfoxide), mono-OH MXC (10 μg/mL), pregnenolone (1 μg/mL), or mono-OH MXC and pregnenolone together for 96 h. Levels of P4, androstenedione (A), testosterone (T), estrone (E1), and 17β-estradiol (E2) in media were determined, and follicles were processed for histological evaluation of atresia. Pregnenolone treatment alone stimulated production of all steroid hormones except E2. Mono-OH MXC-treated follicles had decreased sex steroids, but when given pregnenolone, produced levels of P4, A, T, and E1 that were comparable to those in vehicle-treated follicles. Pregnenolone treatment did not prevent growth inhibition and increased atresia in mono-OH MXC-treated follicles. Collectively, these data support the idea that the most upstream effect of mono-OH MXC on steroidogenesis is by reducing the availability of pregnenolone, and that adding pregnenolone may not be sufficient to prevent inhibited follicle growth and survival.

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.

Continuous administration of a P450 aromatase inhibitor induces polycystic ovary syndrome with a metabolic and endocrine phenotype in female rats at adult age

Studying the mechanisms for the complex pathogenesis of polycystic ovary syndrome (PCOS) requires animal models with endocrine, reproductive, and metabolic features of the syndrome. Hyperandrogenism seems to be a central factor in PCOS, leading to anovulation and insulin resistance. In female rats, continuous administration of letrozole, a nonsteroidal inhibitor of P450 aromatase, at 400 μg/d starting before puberty induces hyperandrogenemia and reproductive abnormalities similar to those in women with PCOS. However, despite high circulating testosterone levels, these rats do not develop metabolic abnormalities, perhaps because of their supraphysiological testosterone concentrations or because estrogen synthesis is completely blocked in insulin-sensitive tissues. To test the hypothesis that continuous administration of lower doses of letrozole starting before puberty would result in both metabolic and reproductive phenotypes of PCOS, we performed a 12-wk dose-response study. At 21 d of age, 46 female Wistar rats were divided into two letrozole groups (100 or 200 μg/d) and a control group (placebo). Both letrozole doses resulted in increased body weight, inguinal fat accumulation, anovulation, larger ovaries with follicular atresia and multiples cysts, endogenous hyperandrogemia, and lower estrogen levels. Moreover, rats that received 200 μg/d had insulin resistance and enlarged adipocytes in inguinal and mesenteric fat depots, increased circulating levels of LH, decreased levels of FSH, and increased ovarian expression of Cyp17a1 mRNA. Thus, continuous administration of letrozole, 200 μg/d, to female rats for 90 d starting before puberty results in a PCOS model with reproductive and metabolic features of the syndrome.

Letrozole increases ovarian growth and Cyp17a1 gene expression in the rat ovary

OBJECTIVE

To evaluate the effects of letrozole on ovarian size and steroidogenesis in vivo, as well as on proliferation and steroidogenesis of theca-interstitial cells alone and in coculture with granulosa cells using an in vitro model.

DESIGN

In vivo and in vitro studies.

SETTING

Research laboratory.

ANIMAL(S)

Immature Sprague-Dawley female rats.

INTERVENTION(S)

In vivo effects of letrozole were studied in intact rats receiving either letrozole (90-day continuous-release SC pellets, 400 μg/d) or placebo pellets (control group). In in vitro experiments, theca cells were cultured alone or in coculture with granulosa cells in the absence or presence of letrozole.

MAIN OUTCOME MEASURE(S)

Deoxyribonucleic acid synthesis was determined by thymidine incorporation assay; steroidogenesis by mass spectrometry; and steroidogenic enzyme messenger RNA (mRNA) expression by polymerase chain reaction.

RESULT(S)

In vivo, letrozole induced an increase in ovarian size compared with the control group and also induced a profound increase of androgen, LH levels, and Cyp17a1 mRNA expression. Conversely, a decrease in Star, Cyp11a1, and Hsd3b1 transcripts was observed in letrozole-exposed rats. In vitro, letrozole did not alter either theca cell proliferation or Cyp17a1 mRNA expression. Similarly, letrozole did not affect Cyp17a1 transcripts in granulosa-theca cocultures.

CONCLUSION(S)

These findings suggest that letrozole exerts potent, but indirect, effect on growth of rat ovary and dramatically increases androgen levels and Cyp17a1 mRNA expression, the key enzyme regulating the androgen biosynthesis pathway. The present findings reveal novel mechanisms of action of letrozole in the rat ovary.

Genome-wide matching of genes to cellular roles using guilt-by-association models derived from single sample analysis

Background

High-throughput methods that ascribe a cellular or physiological function for each gene product are useful to understand the roles of genes that have not been extensively characterized by molecular or genetic approaches. One method to infer gene function is "guilt-by-association", in which the expression pattern of a poorly characterized gene is shown to co-vary with the expression of better-characterized genes. The function of the poorly characterized gene is inferred from the known function(s) of the well-described genes. For example, genes co-expressed with transcripts that vary during the cell cycle, development, environmental stresses, and with oncogenesis have been implicated in those processes.

Findings

While examining the expression characteristics of several poorly characterized genes, we noted that we could associate each of the genes with a cellular phenotype by correlating individual gene expression changes with gene set enrichment scores from individual samples. We evaluated the effectiveness of this approach using a modest sized gene expression data set (expO) and a compendium of gene expression phenotypes (MSigDBv3.0). We found the transcripts that correlated best with enrichment in mitochondrial and lysosomal gene sets were mostly related to those processes (89/100 and 44/50, respectively). The reciprocal evaluation, ranking gene sets according to correlation of enrichment with an individual gene’s expression, also reflected known associations for prominent genes in the biomedical literature (16/19). In evaluating the model, we also found that 4% of the genome encodes proteins that are associated with small molecule and small peptide signal transduction gene sets, implicating a large number of genes in both internal and external environmental sensing.

Conclusions

Our results show that this approach is useful to infer functions of disparate sets of genes. This method mirrors the biological experimental approaches used by others to associate individual genes with defined gene expression changes. Moreover, the approach can be used beyond discovering genes related to a cellular process to discover meaningful expression phenotypes from a compendium that are associated with a given gene. The effectiveness, versatility, and breadth of this approach make possible its application in a variety of contexts and with a variety of downstream analyses.

Perimenopausal regulation of steroidogenesis in the nonhuman primate

Human aging is characterized by a marked decrease in circulating levels of dehydroepiandrosterone (DHEA) and DHEA-sulfate (DHEAS), hormonal changes associated with cognitive decline. Despite beneficial effects of DHEA supplementation in rodents, studies in elderly humans have generally failed to show cognitive improvement after treatment. In the present study we evaluate the effects of age and estradiol supplementation on expression of genes involved in the de novo synthesis of DHEA and its conversion to estradiol in the rhesus macaque hippocampus. Using reverse transcription polymerase chain reaction (RT-PCR) we demonstrate the expression of genes associated with this synthesis in several areas of the rhesus brain. Furthermore, real-time PCR reveals an age-related attenuation of hippocampal expression level of the genes CYP17A1, STS, and 3BHSD1/2. Additionally, short-term administration of estradiol is associated with decreased expression of CYP17A1, STS, SULT2B1, and AROMATASE, consistent with a downregulation not only of estrogen synthesis from circulating DHEA, but also of de novo DHEA synthesis within the hippocampus. These findings suggest a decline in neurosteroidogenesis may account for the inefficacy of DHEA supplementation in elderly humans, and that central steroidogenesis may be a function of circulating hormones and menopausal status.

Ornithine decarboxylase is upregulated by the androgen receptor in skeletal muscle and regulates myoblast proliferation

The aim of this study is to determine if the Odc1 gene, which encodes ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine biosynthesis, is directly regulated by the androgen receptor (AR) in skeletal muscle myoblasts and if Odc1 regulates myoblast proliferation and differentiation. We previously showed that expression of Odc1 is decreased in muscle from AR knockout male mice. In this study, we show in vivo that Odc1 expression is also decreased >60% in muscle from male muscle-specific AR knockout mice. In normal muscle homeostasis, Odc1 expression is regulated by age and sex, reflecting testosterone levels, as muscle of adult male mice expresses high levels of Odc1 compared with age-matched females and younger males. In vitro, expression of Odc1 is 10- and 1.5-fold higher in proliferating mouse C(2)C(12) and human skeletal muscle myoblasts, respectively, than in differentiated myotubes. Dihydrotestosterone increases Odc1 levels 2.7- and 1.6-fold in skeletal muscle cell myoblasts after 12 and 24 h of treatment, respectively. Inhibition of ODC activity in C(2)C(12) myoblasts by α-difluoromethylornithine decreases myoblast number by 40% and 66% following 48 and 72 h of treatment, respectively. In contrast, overexpression of Odc1 in C(2)C(12) myoblasts results in a 27% increase in cell number vs. control when cells are grown under differentiation conditions for 96 h. This prolonged proliferation is associated with delayed differentiation, with reduced expression of the differentiation markers myogenin and Myf6 in Odc1-overexpressing cells. In conclusion, androgens act via the AR to upregulate Odc1 in skeletal muscle myoblasts, and Odc1 promotes myoblast proliferation and delays differentiation.

Influence of anabolic combinations of an androgen plus an estrogen on biochemical pathways in bovine uterine endometrium and ovary

The application of anabolic steroids in food producing animals is forbidden in the EU since 1988, but the abuse of such drugs is a potential problem. The existing test systems are based on known compounds and can be eluded by newly emerging substances. The examination of physiological effects of anabolic hormones on different tissues to indirectly detect misuse might overcome this problem. Two studies were conducted with post-pubertal 24-months old Nguni heifers and pre-pubertal female 2-4 weeks old Holstein Friesian calves, respectively. The animals of the accordant treatment groups were administered combinations of estrogenic and androgenic compounds. The measurement of the gene expression pattern was undertaken with RT-qPCR. Target genes of different functional groups (receptors, angiogenesis, steroid synthesis, proliferation, apoptosis, nutrient metabolism and others) have been quantified. Several biochemical pathways were shown to be influenced by anabolic treatment. Both studies identified significant regulations in steroid and growth factor receptors (AR, ERβ, LHR, FSHR, Flt-1, PR, IGF-1R, Alk-6), angiogenic and tissue remodeling factors (VEGFs, FGFs, BMPs, ANGPT-2, MMPs, TIMP-2, CTSB), steroid synthesis (S5A1, HSD17, CYP19A1), proliferation (TNFα, IGF-1, IGFBPs, p53, c-fos; CEBPD, c-kit), apoptosis (CASP3, FasL, p53) and others (C7, INHA, STAR). Several genes were regulated to opposite directions in post-pubertal compared to pre-pubertal animals. PCA for Nguni heifers demonstrated a distinct separation between the control and the treatment group. In conclusion, anabolics modify hormone sensitivity and steroid synthesis, and they induce proliferative effects in the whole reproductive tract (uterus and ovary) as well as anti-angiogenic effects in the ovary. However, the extent will depend on the developmental stage of the animals.

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.

Epigenetic effects of endocrine-disrupting chemicals on female reproduction: an ovarian perspective

The link between in utero and neonatal exposure to environmental toxicants, such as endocrine-disrupting chemicals (EDCs) and adult female reproductive disorders is well established in both epidemiological and animal studies. Recent studies examining the epigenetic mechanisms involved in mediating the effects of EDCs on female reproduction are gathering momentum. In this review, we describe the developmental processes that are susceptible to EDC exposures in female reproductive system, with a special emphasis on the ovary. We discuss studies with select EDCs that have been shown to have physiological and correlated epigenetic effects in the ovary, neuroendocrine system, and uterus. Importantly, EDCs that can directly target the ovary can alter epigenetic mechanisms in the oocyte, leading to transgenerational epigenetic effects. The potential mechanisms involved in such effects are also discussed.

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.

Insufficient luteinizing hormone-induced intracellular signaling disrupts ovulation in preovulatory follicles lacking estrogen receptor-{beta}

Gonadotropin-stimulated estrogen receptor-beta (ERbeta)-null preovulatory follicles exhibit submaximal estradiol production, insufficient acquisition of LH receptor, and attenuated expression of essential ovulatory genes. These observations lead to low ovulatory rates compared with wild-type (WT) follicles. We hypothesize that insufficient LH receptor results in reduced cAMP production after an ovulatory stimulus. Individual preantral follicles were cultured with FSH for 4 d and then induced to ovulate with a single dose of human chorionic gonadotropin (hCG). cAMP levels 1 h after hCG were 50% lower in ERbeta-null than WT follicles. To determine whether the lack of LH receptor, and resulting lack of cAMP, could be bypassed by direct activation of adenylyl cyclase, WT and ERbeta-null follicles were induced to ovulate with forskolin. Ten micromolar forskolin doubled the ovulatory rate of ERbeta-null follicles compared with treatment with hCG ( approximately 50 vs. 25%, respectively). In WT follicles, 10 microm forskolin reduced the ovulation rate compared with hCG (14 vs. 83%, respectively), indicating that high doses of forskolin inhibited WT ovulation. A 10 microm concentration of forskolin induced cAMP levels in ERbeta-null follicles that were comparable to levels produced in WT follicles after hCG and either partially or completely rescued the attenuated expression of LH-responsive genes. These data indicate that direct activation of adenylyl cyclase, resulting in increased production of cAMP, partially rescues the ovulatory response of ERbeta-null follicles, suggesting that insufficient LH receptor and low cAMP levels contribute to their poor ovulatory rates. We also determined that ERbeta-null ovaries exhibit an alteration in the activation of ERK1/2. Our evaluation of the ERbeta-null ovarian phenotype indicates that ERbeta plays a role in facilitating folliculogenesis. We show that expression of ERbeta in preovulatory follicles is required for adequate cAMP production and propose that an optimal level of cAMP is required for hCG-stimulated ovulation.

Mice lacking Mrp1 have reduced testicular steroid hormone levels and alterations in steroid biosynthetic enzymes

The multidrug resistance-associated protein 1 (MRP1/ABCC1) is a member of the ABC active transporter family that can transport several steroid hormone conjugates, including 17beta-estradiol glucuronide, dehydroepiandrosterone sulfate (DHEAS), and estrone 3-sulfate. The present study investigated the role that MRP1 plays in maintaining proper hormone levels in the serum and testes. Serum and testicular steroid hormone levels were examined in both wild-type mice and Mrp1 null mice. Serum testosterone levels were reduced 5-fold in mice lacking Mrp1, while testicular androstenedione, testosterone, estradiol, and dehydroepiandrosterone (DHEA) were significantly reduced by 1.7- to 4.5-fold in Mrp1 knockout mice. Investigating the mechanisms responsible for the reduction in steroid hormones in Mrp1-/- mice revealed no differences in the expression or activity of enzymes that inactivate steroids, the sulfotransferases or glucuronosyltransferases. However, steroid biosynthetic enzyme levels in the testes were altered. Cyp17 protein levels were increased by 1.6-fold, while Cyp17 activity using progesterone as a substrate was also increased by 1.4- to 2.0-fold in mice lacking Mrp1. Additionally, the ratio of 17beta-hydroxysteroid dehydrogenase to 3beta-hydroxysteroid dehydrogenase, and steroidogenic factor 1 to 3beta-hydroxysteroid dehydrogenase were significantly increased in the testes of Mrp1-/- mice. These results indicate that Mrp1-/- mice have lowered steroid hormones levels, and suggests that upregulation of steroid biosynthetic enzymes may be an attempt to maintain proper steroid hormone homeostasis.

Characterization of the ovarian and reproductive abnormalities in prepubertal and adult estrogen non-responsive estrogen receptor alpha knock-in (ENERKI) mice

Estrogen non-responsive estrogen receptor alpha (ERalpha) knock-in (ENERKI) mice have a mutation (glycine 525 to leucine, G525L) in the ligand-binding domain of ERalpha. The mutant ERalpha protein has a significantly lower affinity and response to endogenous estrogens, while not altering growth factor activated ligand-independent pathways. ENERKI females demonstrated signs of early follicle development as determined by a significant increase in antral follicle formation by 20 days of age. Adult ENERKI females were infertile, had hemorrhagic ovarian follicular cysts, and failed to develop corpora lutea in response to a superovulation regimen. These results illustrate the importance of ERalpha ligand-induced signaling for ovarian development and for estrogen feedback on the hypothalamus and pituitary. Although ERalpha ligand-induced signaling by endogenous estrogens is lost in ENERKI females, the ERalpha selective agonist propyl pyrazole triol (PPT), a synthetic nonsteroidal compound, is still able to activate G525L ERalphain vivo to increase uterine weight. To test whether PPT could restore ligand-dependent receptor activation, ENERKI females were treated with PPT and evaluated for spontaneous ovulation, ovarian hemorrhagic cysts, and LH serum levels. Daily PPT treatments beginning on day 4 of life prevented formation of ovarian hemorrhagic cysts in adult ENERKI animals. In accordance with this result, preputial gland weight and LH levels were also lowered in these animals, indicating PPT treatments most likely led to restoration of ERalpha negative feedback of the hypothalamic-pituitary axis.

The mammalian ovary from genesis to revelation

Two major functions of the mammalian ovary are the production of germ cells (oocytes), which allow continuation of the species, and the generation of bioactive molecules, primarily steroids (mainly estrogens and progestins) and peptide growth factors, which are critical for ovarian function, regulation of the hypothalamic-pituitary-ovarian axis, and development of secondary sex characteristics. The female germline is created during embryogenesis when the precursors of primordial germ cells differentiate from somatic lineages of the embryo and take a unique route to reach the urogenital ridge. This undifferentiated gonad will differentiate along a female pathway, and the newly formed oocytes will proliferate and subsequently enter meiosis. At this point, the oocyte has two alternative fates: die, a common destiny of millions of oocytes, or be fertilized, a fate of at most approximately 100 oocytes, depending on the species. At every step from germline development and ovary formation to oogenesis and ovarian development and differentiation, there are coordinated interactions of hundreds of proteins and small RNAs. These studies have helped reproductive biologists to understand not only the normal functioning of the ovary but also the pathophysiology and genetics of diseases such as infertility and ovarian cancer. Over the last two decades, parallel progress has been made in the assisted reproductive technology clinic including better hormonal preparations, prenatal genetic testing, and optimal oocyte and embryo analysis and cryopreservation. Clearly, we have learned much about the mammalian ovary and manipulating its most important cargo, the oocyte, since the birth of Louise Brown over 30 yr ago.

Adrenocorticotropic hormone suppresses gonadotropin-stimulated estradiol release from zebrafish ovarian follicles

While stress is known to impact reproductive performance, the pathways involved are not entirely understood. Corticosteroid effects on the functioning of the hypothalamus-pituitary-gonadal axis are thought to be a key aspect of stress-mediated reproductive dysfunction. A vital component of the stress response is the pituitary secretion of adrenocorticotropic hormone (ACTH), which binds to the melanocortin 2 receptor (MC2R) in the adrenal glands and activates cortisol biosynthesis. We recently reported MC2R mRNA abundance in fish gonads leading to the hypothesis that ACTH may be directly involved in gonadal steroid modulation. Using zebrafish (Danio rerio) ovarian follicles, we tested the hypothesis that acute ACTH stimulation modulates cortisol and estradiol (E(2)) secretion. ACTH neither affected cortisol nor unstimulated E(2) release from ovarian follicles. However, ACTH suppressed human chorionic gonadotropin (hCG)-stimulated E(2) secretion in a dose-related manner, with a maximum decrease of 62% observed at 1 I.U. ACTH mL(-1). This effect of ACTH on E(2) release was not observed in the presence of either 8-bromo-cAMP or forskolin, suggesting that the mechanism(s) involved in steroid attenuation was upstream of adenylyl cyclase activation. Overall, our results suggest that a stress-induced rise in plasma ACTH levels may initiate a rapid down-regulation of acute stimulated E(2) biosynthesis in the zebrafish ovary, underscoring a novel physiological role for this pituitary peptide in modulating reproductive activity.

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.