Estrogen actions on follicle formation and early follicle development

Spatiotemporal single-cell RNA sequencing reveals the role of steroid hormone pathway during chicken primordial follicle formation

The size of the initial primordial follicle pool in the ovary depends on primordial follicle formation, which determines the female reproductive lifespan. However, the molecular regulation of primordial follicle formation in chickens remains unclear. In this study, the left ovaries of chickens were collected at 2 d posthatch (dph), 5.5 dph, and 10.5 dph to examine the formation of primordial follicles. Single-cell mRNA sequencing (scRNA-seq) and spatial transcriptomic analysis were performed to explore the ovarian microenvironment and identify regulatory pathways involved in the formation of primordial follicles in chickens. Histomorphological analysis of chicken ovary tissues revealed the presence of germ cell cysts at 1 dph, which began to disintegrate at 2 dph. Primordial follicles appeared at 5.5 dph and continued to develop into larger-diameter follicles. scRNA-seq and spatial transcriptomic analysis revealed 24 cellular clusters involved in chicken primordial follicle formation. The metabolic pathway of steroid hormone synthesis was found in pregranulosa and pretheca cells. Histological analysis showed that chicken ovaries did not form primordial follicles after the inhibition of the steroid hormone synthesis pathway by simvastatin or tamoxifen. In addition, mRNA transcriptomic and bioinformatics analyses revealed that GREB1 was a downstream gene of the steroid hormone synthesis pathway during the formation of chicken primordial follicles. This study provides a valuable foundation for investigating primordial follicle formation in avian species and optimizing their reproductive performance.

Single-cell sequencing reveals the transcriptional alternations of 17β-estradiol suppressing primordial follicle formation in neonatal mouse ovaries

Estrogen has been implicated in multiple biological processes, but the variation underlying estrogen-mediated primordial follicle (PF) formation remains unclear. Here, we show that 17β-estradiol (E2) treatment of neonatal mice led to the inhibition of PF formation and cell proliferation. Single-cell RNA sequencing (scRNA-seq) revealed that E2 treatment caused significant changes in the transcriptome of oocytes and somatic cells. E2 treatment disrupted the synchronised development of oocytes, pre-granulosa (PG) cells and stromal cells. Mechanistically, E2 treatment disrupted several signalling pathways critical to PF formation, especially down-regulating the Kitl and Smad1/3/4/5/7 expression, reducing the frequency and number of cell communication. In addition, E2 treatment influenced key gene expression, mitochondrial function of oocytes, the recruitment and maintenance of PG cells, the cell proliferation of somatic cells, as well as disordered the ovarian microenvironment. This study not only revealed insights into the regulatory role of estrogen during PF formation, but also filled in knowledge of dramatic changes in perinatal hormones, which are critical for the physiological significance of understanding hormone changes and reproductive protection.

Edible bird's nest improves the premature ovarian failure induced by tripterygium glycosides

Premature ovarian failure (POF) is a common disease in the field of gynecological endocrinology that seriously affects the physical and mental health of patients. Previous studies found that edible bird's nest (EBN) could improve uterine function. These suggested that EBN might also have an ameliorating effect on POF. Therefore, in this study, tripterygium glycosides (TGs) were used to induce POF in rats, and the effect of EBN on the improvement of POF was investigated. After the administration of EBN for 14 days, ovarian index and uterine index, serum hormone levels, apoptosis rate of ovarian granulosa cells, follicle-stimulating hormone receptor (FSHR) protein expression level, and the histopathological examination of the ovaries were determined. It was found that administration of medium and high EBN dose groups increased the ovarian index and granular layer thickness of rats with POF. Particularly, higher follicle-stimulating hormone levels and lower corpus luteum content were observed in the high EBN dose group. In addition, there were lower luteinizing hormone levels and fewer atretic follicles but higher progesterone levels in the medium EBN dose group. These results indicated that EBN had preventive and curative effects on POF induced by TGs. Its mechanism of action might be related to the reduction of ovarian granulosa cell apoptosis, regulation of hormones and receptors, and inhibition of follicle closure.

Enhanced inhibition of human and rat aromatase activity by benzene ring substitutions in bisphenol A: QSAR structure-activity relationship and in silico docking analysis

Bisphenol A (BPA) is a widely used plastic material, but its potential endocrine disrupting effect has restricted its use. The BPA alternatives have raised concerns. This study aimed to compare inhibitory potencies of 11 BPA analogues on human and rat placental aromatase (CYP19A1). The inhibitory potency on human CYP19A1 ranged from bisphenol H (IC50, 0.93 μM) to tetramethyl BPA and tetrabromobisphenol S (ineffective at 100 μM) when compared to BPA (IC50, 73.48 μM). Most of them were mixed/competitive inhibitors and inhibited estradiol production in human BeWo cells. Molecular docking analysis showed all BPA analogues bind to steroid active site or in between steroid and heme of CYP19A1 and form a hydrogen bond with catalytic residue Met374. Pharmacophore analysis showed that there were 4 hydrophobic regions for BPA analogues, with bisphenol H occupying 4 regions. Bivariate correlation analysis showed that LogP (lipophilicity) and LogS (water solubility) of BPA analogues were correlated with their IC50 values. Computerized drug metabolism and pharmacokinetics analysis showed that bisphenol H, tetrabromobisphenol A, and tetrachlorobisphenol A had low solubility, which might explain their weaker inhibition on estradiol production on BeWo cells. In conclusion, BPA analogues mostly can inhibit CYP19A1 and the lipophilicity determines their inhibitory strength.

MicroRNA-338-3p helps regulate ovarian function by affecting granulosa cell function and early follicular development

BACKGROUND

Follicular development in mammalian ovaries is a complex and dynamic process, and the interactions and regulatory-feedback loop between the follicular microenvironment, granulosa cells (GCs), and oocytes can affect follicular development and normal ovary functions. Abnormalities in any part of the process may cause abnormal follicular development, resulting in infertility. Hence, exploring the pathogenesis of abnormal follicular development is extremely important for diagnosing and treating infertile women.

METHODS

RNA sequencing was performed with ovarian cortical tissues established in vitro. In situ-hybridization assays were performed to study microRNA-338-3p (miR-338-3p) expressed in GCs and oocytes. In vitro culture models were established with GCs and neonatal mouse ovaries to study the biological effects of miR-338-3p. We also performed in vivo experiments by injecting adeno-associated virus vectors that drive miR-338-3p overexpression into the mouse ovarian bursae.

RESULTS

Sequencing analysis showed that miR-338-3p was expressed at significantly higher levels in ovarian cortical tissues derived from patients with ovarian insufficiency than in cortical tissues derived from patients with normal ovarian function; miR-338-3p was also significantly highly expressed in the GCs of patients with diminished ovarian reserve (P < 0.05). In situ-hybridization assays revealed that miR-338-3p was expressed in the cytoplasm of GCs and oocytes. Using in vitro culture models of granulosa cells, we found that miR-338-3p overexpression significantly suppressed the proliferation and oestradiol-production capacity of GCs (P < 0.05). In vitro culture models of neonatal mouse ovaries indicated that miR-338-3p overexpression suppressed the early follicular development in mouse ovaries. Further analysis revealed that miR-338-3p might be involved in transforming growth factor β-dependent regulation of granulosa cell proliferation and, thus, early follicular development. Injecting miR-338-3p-overexpression vectors into the mouse ovarian bursae showed that miR-338-3p down-regulated the oocyte mitochondrial membrane potential in mice and disrupted mouse oestrous cycles.

CONCLUSION

miR-338-3p can affect early follicular development and normal ovary functions by interfering with the proliferation and oestradiol production of GCs. We systematically elucidated the regulatory effect of miR-338-3p on follicular development and the underlying mechanism, which can inspire new studies on the diagnosis and treatment of diseases associated with follicular development abnormalities.

Nanowarming improves survival of vitrified ovarian tissue and follicular development in a sheep model

Tissue cryopreservation has allowed long term banking of biomaterials in medicine. Ovarian tissue cryopreservation in particular helps patients by extending their fertility window. However, protection against tissue injury during the thawing process has proven to be challenging. This is mainly due to the heterogenous and slow distribution of the thermal energy across the vitrified tissue during a conventional warming process. Nanowarming is a technique that utilizes hyperthermia of magnetic nanoparticles to accelerate this process. Herein, hyperthermia of synthesized PEGylated silica-coated iron oxide nanoparticles was used to deter the injury of cryopreserved ovarian tissue in a sheep model. When compared to the conventional technique, our findings suggest that follicular development and gene expression in tissues warmed by the proposed technique have been improved. In addition, Nanowarming prevented cellular apoptosis and oxidative stress. We therefore conclude that Nanowarming is a potential complementary candidate to increase efficiency in the ovarian cryopreservation field.

Colitis-Mediated Dysbiosis of the Intestinal Flora and Impaired Vitamin A Absorption Reduce Ovarian Function in Mice

Changes in the composition and ratio of the flora during colitis have been found to potentially affect ovarian function through nutrient absorption. However, the mechanisms have not been fully explored. To investigate whether colitis-induced dysbacteriosis of the intestinal flora affects ovarian function, mice were given dextran sodium sulfate (DSS) through drinking water. High-throughput sequencing technology was used to clarify the composition and proportion of bacterial flora as well as gene expression changes in the colon. Changes in follicle type, number, and hormone secretion in the ovary were detected. The results showed that 2.5% DSS could induce severe colitis symptoms, including increased inflammatory cell infiltration, severe damage to the crypt, and high expression of inflammatory factors. Moreover, vitamin A synthesis metabolism-related genes Rdh10, Aldh1a1, Cyp26a1, Cyp26b1, and Rarβ were significantly decreased, as well as the levels of the steroid hormone synthase-related proteins STAR and CYP11A1. The levels of estradiol, progesterone, and Anti-Mullerian hormone as well as the quality of oocytes decreased significantly. The significantly changed abundances of Alistipes, Helicobacter, Bacteroides, and some other flora had potentially important roles. DSS-induced colitis and impaired vitamin A absorption reduced ovarian function.

In utero bisphenol A exposure disturbs germ cell cyst breakdown through the PI3k/Akt signaling pathway and BDNF expression

PURPOSE

To determine the influence of the environmental endocrine disruptor bisphenol A (BPA) on germ cell cyst breakdown and explore the possible mechanisms regulating this activity.

METHODS

BPA (2 μg/kg/d or 20 μg/kg/d) or tocopherol-stripped corn oil (vehicle control) was administered to pregnant mice by gavage at gestational day 11, and the offspring (prenatally treated mice) were sacrificed and ovariectomized at postnatal day (PND) 4 and PND22. Ovarian morphology was documented in the first filial (F1) generation female offspring, and the follicles were analyzed and classified morphologically on PND 4. To discover differentially expressed genes and associated target pathways, we used RNA-seq, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and Gene Ontology (GO) analysis. The mRNA expression of key steroid hormone synthesis-related genes was evaluated by Q-PCR in forskolin-induced KGN cells. Western blotting (WB) and qRTPCR were used to determine the protein and gene expression levels of brain-derived neurotrophic factor (BDNF).

RESULTS

BPA, a typical endocrine disrupting chemical (EDC), decreased the expression of the key steroid hormone synthesis-related genes P450scc and aromatase, while the expression of Star increased significantly and caused no significant difference in the expression of Cyp17a1 or HSD3β in forskolin-induced KGN cells. Moreover, we confirmed that in utero exposure to environmentally relevant concentrations of BPA (2 μg/kg/d and 20 μg/kg/d) could significantly disrupt germ cell cyst breakdown, leading to the generation of fewer primordial follicles than in the control group. The factors mediating the inhibitory effects included the PI3K-Akt signaling pathway and a significant downregulation of BDNF.

CONCLUSIONS

These findings indicate that in utero exposure to BPA at low doses, which are lower than recommended as 'safe' dosages, may influence the formation of primordial follicles by inhibiting the expression of steroid hormone synthesis-related genes and partly by regulating the BDNF-mediated PI3K/Akt pathway.

Toxic effect window of ovarian development in female offspring mice induced by prenatal prednisone exposure with different doses and time

BACKGROUND

Prednisone is one of the most used synthetic glucocorticoids during pregnancy. Epidemiological investigations suggested that prenatal prednisone therapy could affect fetal development, but systematic studies on its effects on ovarian development and the "toxic effect window" remained scarce.

METHODS

In this study, by simulating clinical application characteristics, Kunming mice were given prednisone by oral gavage with different doses (0.25 or 1.0 mg/kg·d) or at different time gestational days (GD) (GD0-9, GD10-18, or GD0-18). Blood and ovaries of fetal mice were collected on GD18, and the serum estradiol level and the related function indexes of ovarian granulosa cells and oocytes were detected.

RESULTS

Compared with the control group, prenatal prednisone exposure (PPE) induced pathological injury and enhanced cell proliferation in fetal mice ovary. Furthermore, the expression of steroid synthesis functional genes in pre-granulosa cells, the oocyte function markers, and developmentally related genes was enhanced with different doses or at different time of PPE. The Hippo signaling was activated in the fetal ovary of PPE groups. The above changes were most significant in the low or high-dose and full-term PPE groups.

CONCLUSION

PPE caused various cell developmental toxicity in the fetal ovary, especially in the low or high-dose, full-term exposure groups. The potential mechanism might be related to the activation of the Hippo signaling pathway.

Characterization of relaxin 3 and its receptors in chicken: Evidence for relaxin 3 acting as a novel pituitary hormone

Mammalian relaxin (RLN) family peptides binding their receptors (RXFPs) play a variety of roles in many physiological processes, such as reproduction, stress, appetite regulation, and energy balance. In birds, although two relaxin family peptides (RLN3 and INSL5) and four receptors (RXFP1, RXFP2, RXFP2-like, and RXFP3) were predicated, their sequence features, signal properties, tissue distribution, and physiological functions remain largely unknown. In this study, using chickens as the experimental model, we cloned the cDNA of the cRLN3 gene and two receptor (cRXFP1 and cRXFP3) genes. Using cell-based luciferase reporter assays, we demonstrate that cRLN3 is able to activate both cRXFP1 and cRXFP3 for downstream signaling. cRXFP1, rather than cRXFP3, is a cognate receptor for cRLN3, which is different from the mammals. Tissue distribution analyses reveal that cRLN3 is highly expressed in the pituitary with lower abundance in the hypothalamus and ovary of female chicken, together with the detection that cRLN3 co-localizes with pituitary hormone genes LHB/FSHB/GRP/CART and its expression is tightly regulated by hypothalamic factors (GnRH and CRH) and sex steroid hormone (E2). The present study supports that cRLN3 may function as a novel pituitary hormone involving female reproduction.

Molecular characterization and functional analysis of Esr1 and Esr2 in gonads of Chinese soft-shelled turtle (Pelodiscus sinensis)

Estrogens and their receptors play crucial roles in regulating the gonadal development of vertebrates. To clarify the roles of estrogen receptors in the gonadal development of turtles, estrogen receptors (Esr1 and Esr2) in Chinese soft-shelled turtle (Pelodiscus sinensis) were identified and characterized, and their function in gonads was investigated by intraperitoneal injection of agonist propylpyrazoletriol (PPT) and diarylpropionitrile (DPN), and antagonist ICI 182,780 (ICI). Ps-Esr1 encoded a 588 amino acid protein and Ps-Esr2 encoded a 556 amino acid protein. The two receptors contained classic domains, including the DNA-binding domain and ligand-binding domain, and amino acid sequences showed high homology with other turtles. Ps-Esr1 showed the highest expression in the testis, followed by the ovary and liver. However, Ps-Esr2 showed the highest expression in the ovary, followed by the brain and testis. Ps-Esr1 expression showed an up-regulation trend in gonadal differentiation. Histomorphometric analysis showed that the number of follicles increased in female juvenile turtles treated with DPN or PPT. In addition, Tsc2, GnRH, and Fshβ were up-regulated in ovaries of turtles treated with agonists, while Sycp3 and Picalm were up-regulated in testes of turtles treated with agonists. Treatment with the antagonist decreased the number of sperm in matured turtles. Stra8, Scyp3, Dmc1, Picalm, Evl, Boule, and Cdk1 were up-regulated in testis after antagonist treatment. The results indicated that Esr1 might play an important role in gonadal differentiation, and the two estrogen receptors might be involved in the spermatogenesis of the turtle. These results could provide a reference for further research on the function of the estrogen signal in male vertebrates.

The association of serum phthalate metabolites with biomarkers of ovarian reserve in women of childbearing age

Phthalates (PAEs) are widely used plasticizers drawing increasing concern due to reproductive toxicity. However, studies on serum PAEs metabolites (mPAEs) and their associations with human ovarian function remain very scarce. In this study, from April 2019 to August 2020, a total of 297 women of childbearing age were recruited in Tianjin, China. Eleven mPAEs were analyzed in serum samples and eight mPAEs were detected at frequencies > 65% with median concentrations of 0.43-15.3 ng/mL. In multinomial logistic analysis, an increase in serum mono (2-isobutyl) phthalate (miBP) was associated with decline in antral follicle count (AFC) (OR=1.26, 95% CI: 0.99, 1.61) and 5-mono-(2-ethyl-5-hydroxyhexyl) phthalate (mEHHP) was significantly associated with AFC increase (OR=1.43, 95% CI: 1.06, 1.92), which were aligned with the associations found between mPAEs and AMH through generalized linear regression. In multiple linear regression models, per 10% increase in serum mono (2-ethylhexyl) phthalate (mEHP), mono (2-ethyl-5-oxohexyl) phthalate (mEOHP) (oxo-mEHP), and principal component 1 featured for high concentrations of mono-n-butyl phthalate (mBP), miBP and mEHP were associated with 0.15 (95% CI: -0.29, -0.02), 0.01 (95% CI: -0.01, 0.00) and 0.01 (95% CI: -0.02, 0.00) ln-unit decrease in estradiol (E2) levels, respectively, while mono-[(2-carboxymethyl) hexyl] phthalate (mCMHP) (carboxymethyl-mEHP) was positively associated with 0.05 ln-unit increase of E2 (95% CI: 0.02, 0.08). The observed negative associations between mPAEs and the Anti-Müllerian hormone (AMH) also aligned with the change in AFC. Generalized linear regression also revealed nonlinear associations between mono-ethyl phthalate (mEP), mCMHP and follicle-stimulating hormone (FSH). Overall, serum mEHP and its metabolites were negatively associated with E2. miBP was negatively associated with AFC. The nonlinear associations between mPAEs and FSH, and AMH need further study.

Effects of active immunization against a 13-amino acid receptor-binding epitope of FSHβ on fertility regulation in female mice

Follicle-stimulating hormone (FSH) is crucial for ovarian folliculogenesis and thus essential for female fertility. Here, we developed a novel FSH vaccine based on the tandem of a 13-amino acid receptor-binding epitope of FSHβ (FSHβ13AA-T) and used a mouse model to test its efficacy in female fertility regulation. Compared to placebo-immunized controls, FSHβ13AA-T vaccination: induced a marked (P < 0.05) antibody generation; reduced (P < 0.05) serum concentrations of FSH, inhibin B and 17β-estradiol; disrupted (P < 0.05) normal estrous cyclicity; delayed (P = 0.08) establishment of pregnancy; blocked (P < 0.05) folliculogenesis; and reduced (P < 0.05) litter size. Mechanistically, FSH vaccination reduced (P < 0.05) ovarian estrogen production by decreasing Lhcgr, Cyp19a1 and HSD3β1 expression, and suppressed ovarian follicular development by decreasing ovarian Fshr, Inhα, Foxo3a, Bmp15 and Cdh1 expression. Overall, vaccination of female mice with FSHβ13AA-T substantially disrupted FSH-dependent ovarian steroidogenesis and folliculogenesis, and caused subfertility. Therefore, vaccines based on FSHβ13AA-T have potential as anti-fertility/contraceptive agents in females.

Development of a predictive model for luteal phase oocyte retrieval in poor responders undergoing natural cycle IVF

The aim of this study is the development of a prediction model indicating successful application of Oocyte Retrieval performed during the Luteal Phase (LuPOR) in poor responders, as defined by the retrieval of at least one MII oocyte. Recruitment included 1688 poor responders diagnosed as per Bologna Criteria, undergoing natural cycle ICSI between 2012 and 2020. Oocyte collections were performed during the follicular phase and during the luteal phase similarly. Antral Follicle Count (AFC), Estradiol (E₂) levels evaluated on both trigger days prior to Follicular Phase Oocyte Retrieval (FoPOR) and LuPOR, and the number of small follicles 8–12 mm that were not aspirated during FoPOR were identified as predictive factors indicative of an efficient LuPOR practice with an Area Under the Curve (AUC) of 0.86, 0.86, 0.89 as well as 0.82 respectively. The combination of the above-mentioned characteristics into a prediction model provided an AUC of 0.88, specificity and a sensitivity of 0.73 and 0.94 respectively and an accuracy of 0.89. The model provided a positive predictive value (PPV) of 93.5% and a negative predictive value (NPV) of 46.8%. The clinical conclusion of the present study aims to be of added value to the clinician, by providing a prediction model defining the POR population benefiting from LuPOR. The high PPV of this model may renders this tool helpful for the practitioner that considers LuPOR.

Oocyte Survival and Development during Follicle Formation and Folliculogenesis in Mice Lacking Aromatase

BACKGROUND

Assembly of oocytes into primordial follicles is essential for establishing the ovarian reserve required for female fertility. In mice, this process begins during embryonic development. Primordial germ cells form cysts by incomplete mitosis until 13.5 days post coitum (dpc). These cysts break apart just before birth. Some oocytes undergo apoptosis while surviving oocytes are enclosed by granulosa cells to form primordial follicles. Cyst breakdown and primordial follicle formation were previously shown to be inhibited by estradiol and estrogenic compounds in vitro, suggesting that estrogen is important for regulation of this process.

METHODS

To determine the role of fetal estrogen in cyst breakdown and follicle formation these processes were quantified in aromatase deficient (ArKO) mice between 17.5 dpc and postnatal day (PND) 9. Ovaries of ArKO mice were also examined at 2-week intervals to determine if folliculogenesis is affected by lack of estrogen and the age at which the typical ArKO ovarian phenotype first appears.

RESULTS

Oocyte number, follicle assembly, and follicle development in ArKO mice did not differ from controls between 17.5 dpc and PND 9. At 2 weeks, ArKO ovaries still had oocytes in cysts while all oocytes were enclosed in follicles in wild type ovaries. From 2 to 8 weeks oocyte numbers were similar in all genotypes with a significant reduction at 10 weeks in ovaries from homozygous mutants. Abnormal hemorrhagic follicles were observed starting at 6 weeks, earlier than previously reported and hemosiderin deposits were found starting at 8 weeks.

CONCLUSIONS

These results suggest that a lack of fetal estrogen does not affect oocyte survival or the rate of primordial follicle formation perinatally, and maternal estrogen or other signals are the chief regulators. The appearance of abnormal hemorrhagic follicles observed as early as 6 weeks suggests that the lack of estrogen becomes problematic at this time.

Insights into in vivo follicle formation: a review of in vitro systems

In vitro systems capable of reconstituting the process of mouse oogenesis are now being established to help develop further understanding of the mechanisms underlying oocyte/follicle development and differentiation. These systems could also help increase the production of useful livestock or genetically modified animals, and aid in identifying the causes of infertility in humans. Recently, we revealed, using an in vitro system for recapitulating oogenesis, that the activation of the estrogen signaling pathway induces abnormal follicle formation, that blocking estrogen-induced expression of anti-Müllerian hormone is crucial for normal follicle formation, and that the production of α-fetoprotein in fetal liver tissue is involved in normal in vivo follicle formation. In mouse fetuses, follicle formation is not carried out by factors within the ovaries but is instead orchestrated by distal endocrine factors. This review outlines findings from genetics, endocrinology, and in vitro studies regarding the factors that can affect the formation of primordial follicles in mammals.

Effect of oestrogen on mouse follicle growth and meiotic resumption

Many studies have shown that oestrogen affects late follicular development, but whether oestrogen is involved in other aspects of folliculogenesis remains unclear. In this study, two antagonists of oestrogen, tamoxifen and G15, were used to determine the effects of oestrogen on folliculogenesis. Mouse preantral follicles and cumulus-oocyte complexes (COCs) were cultured in vitro. The results showed that follicle growth stimulated using pregnant mare serum gonadotrophin (PMSG) was inhibited using tamoxifen, whether in vivo or in vitro. The average diameters, the maximum diameters of follicles and the numbers of follicles with a diameter of more than 300 μm decreased significantly following a 4-day culture with tamoxifen. G15, the antagonist of oestrogen via the membrane receptor, did not change follicular growth stimulated by PMSG in vitro. Results of in vitro maturation of COCs showed that germinal vesicle breakdown (GVBD) occurred spontaneously (95.1%) after 2 h in culture, and the GVBD ratio changed little with the addition of either oestrogen or 10 μM G15. However, first polar body (PBI) extrusion was driven by oestrogen markedly and supplementation with 10 μM G15 inhibited PBI extrusion (82.4% vs 55.0%) significantly. These results demonstrated that oestrogen promotes follicle growth through the nuclear receptor during follicle growth and then triggers the transition of metaphase to anaphase through the membrane receptor during meiotic resumption. So oestrogen plays a progressive role in the two phases of follicle growth and oocyte meiotic resumption.

Early preantral follicles of the domestic cat express gonadotropin and sex steroid signalling potential

Key biomolecular processes which regulate primordial ovarian follicle dormancy and early folliculogenesis in mammalian ovaries are not fully understood. The domestic cat is a useful model to study ovarian folliculogenesis and is the most relevant for developing in vitro growth methods to be implemented in wild felid conservation breeding programs. Previously, RNA-sequencing of primordial, primary, and secondary follicle samples from domestic cat implicated ovarian steroidogenesis and steroid reception during follicle development. Here we aimed to identify which sex steroid biosynthesis and metabolism enzymes, gonadotropin receptors, and sex steroid receptors are present and may be potential regulators. Differential gene expression, functional annotation, and enrichment analyses were employed and protein localisation was studied too. Gene transcripts for PGR, PGRMC1, AR (steroid receptors), CYP11A1, CYP17A1, HSD17B1 and HSD17B17 (steroidogenic enzymes), and STS (steroid metabolising enzyme) were significantly differentially expressed (Q values of ≤0.05). Differential gene expression increased in all transcripts during follicle transitions apart from AR which decreased by the secondary stage. Immunohistochemistry localised FSHR and LHCGR to oocytes at each stage. PGRMC1 immunostaining was strongest in granulosa cells whereas AR was strongest in oocytes throughout each stage. Protein signals for steroidogenic enzymes were only detectable in secondary follicles. Products of these significantly differentially expressed genes may regulate domestic cat preantral folliculogenesis. In vitro growth could be optimised as all early follicles express gonadotropin and steroid receptors meaning hormone interaction and response may be possible. Protein expression analyses of early secondary follicles supported its potential for producing sex steroids.

Copper and Selenium stimulates CYP19A1 expression in caprine ovarian granulosa cells: possible involvement of AKT and WNT signalling pathways

The role of copper and selenium on activation of estradiol synthesis pathways viz. PKA/AKT/WNT is not clearly elucidated. On this background we attempt to elcuiated the role of copper and selenium on mRNA expression of genes associated with estradiol synthesis in caprine ovarian granulose cell models. Ovarian granulosa cells from medium (3-5 mm) sized follicles were aspirated and distributed separately to different groups. Group I: control, Group II: cupric chloride (Cu: 0.5 mM), Group III: sodium selenite (Se: 100 ng/ml), Group IV: Cu + Se. The cells (10⁵/well) were cultured in 96 well plate in the base culture medium of MEMα comprising of nonessential amino acids (1.1 mM), FSH (10 ng/mL), transferrin (5 µg/mL), IGF-I (2 ng/mL), androstenedione (10^-6 M), penicillin (100 IU/mL), streptomycin (0.1 mg/mL) and fungizone (0.625 µl/mL) and insulin (1 ng/mL). The cells were incubated in a carbondioxide incubator (38 °C, 5% CO₂, 95% RH). The medium was changed on alternate days and cells were harvested on day 6. Day 6 media was used for estimation of estradiol. The RNA isolated form harvested cells was used for qPCR assay. There was no significant (p > 0.05) difference in estradiol concentration between groups. The mRNA expression of AKT1, CYP19A1, WNT2 & 4, FZD6 and APC2 were significantly (p < 0.05) higher in Cu and Cu + Se groups compared to control. Whereas, the mRNA transcript of DVL1 and CSNK1 was significantly (p < 0.05) higher in Cu + Se group compared to control. Incontrast, no significant difference in mRNA expression of PRKAR1A and CTNNB1 was noticed. Our study support a key role of copper and selenium in activation of AKT and WNT signalling pathway that further lead to increase in the mRNA expression of CYP19A1.

The effect of lutein and Urtica dioica extract on in vitro production of embryo and oxidative status in polycystic ovary syndrome in a model of mice

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most prevalent endocrinopathies in women during the reproductive age. Herbal medicines are used increasingly alone or in supplement with chemical medicines for the treatment of different diseases and dysfunctions. This study was aimed to evaluate the effects of lutein and nettle (Urtica dioica) extract on the biochemical parameters and the reproductive function in the PCOS model of mice.

METHODS

Following the induction of PCOS by dehydroepiandrosterone (DHEA), the mice (n = 98) were randomly assigned into seven groups, each consisting of fourteen mice; the groups were included control group (received solvent), PCOS group (received 6 mg/100 g B.W/day IP, DHEA for 21 days), PCOS+ Nettle extract (200 and 400 mg/kg), PCOS+ Lutein (125 and 250 mg/kg), and PCOS+ NL (200 mg/kg nettle extract and 125 mg/kg lutein). The nettle extract and lutein were administrated using gavage for 30 consecutive days after PCOS induction. Malondialdehyde (MDA), total antioxidant capacity (TAC), and estrogen were measured in serum, ovary, and uterus samples by the ELISA method. The total number of oocytes, oocyte quality, fertilization rate, 2-cell blastocyst, and arrested embryos (type I, type II, and type III) were also investigated.

RESULTS

A combination treatment of the nettle and lutein produced the lowest concentration of MDA in comparison to other groups which affected by the PCOS. The lowest level of TAC was observed in the PCOS group without treatment. The number of oocytes, oocyte quality, fertilization rate, and 2-cell blastocyst were significantly higher in the control group, but the lowest values were observed in the PCOS group without any treatment.

CONCLUSIONS

The most favorable findings include improving antioxidant capacity, oocyte and embryo quality were observed in the PCOS+ 125 L group.

Expression patterns and oestradiol regulation of growth differentiation factor 9 in Schizothorax prenanti

Growth differentiation factor 9 (GDF9) plays pivotal roles in regulating follicular development in many mammalian species. In the present study, the full-length Schizothorax prenanti gdf9 cDNA sequence was isolated and characterized, and its expression pattern in developing gonads and in the gonads of exogenous oestradiol (E₂)-fed fish were analysed. The S. prenanti gdf9 cDNA sequence consisted of 1958 base pairs (bp), encoded a 413 amino acid, and showed high sequence similarity with Carassius gibelio and Cyprinus carpio. The quantitative real-time PCR analysis revealed that gdf9 was mainly expressed in the gonads, with particularly high expression in the cortical alveoli stage ovary and late-spermatogenic stage testis. Immunohistochemical signals for Gdf9 were mainly detected in chromatin nucleolar oocytes, spermatogonia and spermatocytes. Furthermore, the gonadal expression of gdf9 induced by exogenous E₂ was related to the feeding time and dose. Taken together, these findings were helpful to gain a better understanding of the role of Gdf9 in both folliculogenesis and spermatogenesis in S. prenanti.

Chronic exposure to low dose of bisphenol A causes follicular atresia by inhibiting kisspeptin neurons in anteroventral periventricular nucleus in female mice

Bisphenol-A (BPA) is an estrogenic chemical extensively used in industrial and household applications. The present study was conducted to investigate the effect of chronic exposure to BPA on the adult female neuroendocrine system. Herein, we found that expose of adult female mice to BPA (50 μg/kg) by oral gavage for 60 days (BPA mice) prolonged diestrus and decreased serum 17β-estradiol (E2) concentration by reducing the number of antral follicles and corpora luteum. In comparison with controls, the levels of serum luteinizing hormone (LH), follicle stimulating hormone (FSH), hypothalamic gonadotrophin releasing hormone (GnRH) and the expression of kisspeptin in anteroventral periventricular nucleus (AVPV) decreased in BPA mice, which could be reversed by injecting kisspeptin-10 (i.c.v.). Treatment with BPA or estrogen receptor α (ERα) antagonist MPP, but not ERβ antagonist PHTPP inhibited E2-induced AVPV-kisspeptin expression in ovariectomized mice. Use of ERα agonist PPT rather than ERβ agonist DPN enhanced AVPV-kisspepetin expression, which decreased after treatment with BPA. The amplitude of the proestrus LH surge decreased in mice exposed to BPA, but was recovered by administering kisspeptin-10. The present study provides in vivo evidence that chronic exposure to a low dose of BPA suppressed ERα-induced activation of AVPV-kisspeptin neurons, leading to prolonged diestrus and reduced ovulation in adult female mice.

A Gatekeeping Role of ESR2 to Maintain the Primordial Follicle Reserve

Over the entire reproductive lifespan in mammals, a fixed number of primordial follicles serve as the source of mature oocytes. Uncontrolled and excessive activation of primordial follicles can lead to depletion of the ovarian reserve. We observed that disruption of estrogen receptor β (ESR2) signaling results in increased activation of primordial follicles in Esr2-null (Esr2-/-) rats. However, follicle assembly was unaffected, and the total number of follicles remained comparable between neonatal wild-type and Esr2-/- ovaries. While the activated follicle counts were increased in Esr2-/- ovary, the number of primordial follicles were markedly decreased. Excessive recruitment of primordial follicles led to premature ovarian senescence in Esr2-/- rats and was associated with reduced levels of serum AMH and estradiol. Disruption of ESR2 signaling through administration of a selective antagonist (PHTPP) increased the number of activated follicles in wildtype rats, whereas a selective agonist (DPN) decreased follicle activation. In contrast, primordial follicle activation was not increased in the absence of ESR1, indicating that the regulation of primordial follicle activation is ESR2 specific. Follicle activation was also increased in Esr2 mutants lacking the DNA binding domain, suggesting a role for the canonical transcriptional activation function. Both primordial and activated follicles express ESR2, suggesting a direct regulatory role for ESR2 within these follicles. We also detected that loss of ESR2 augmented the activation of AKT, ERK, and mTOR pathways. Our results indicate that the lack of ESR2 upregulated both granulosa and oocyte factors, which can facilitate AKT and mTOR activation in Esr2-/- ovaries leading to increased activation of primordial follicles.

Novel CYP19A1 Mutations Extend the Genotype-Phenotype Correlation and Reveal the Impact on Ovarian Function

Context

The steroidogenic enzyme aromatase (CYP19A1) is required for estrogen biosynthesis from androgen precursors in the ovary and extragonadal tissues. The role of aromatase, and thus estrogens, is best illustrated by genetic variations of the CYP19A1 gene leading to aromatase deficiency or excess.

Objective

The objective of this work is to characterize novel CYP19A1 variants.

Design setting and patients

Variants causing aromatase deficiency were suspected in four 46,XX children of African and Indian origin by careful clinical phenotyping. Sequencing of the CYP19A1 gene identified novel variants. Minigene experiments, aromatase activity assay, and computational, and histological analysis were used to characterize the variants.

Main outcome measure and results

CYP19A1 variants were found in all patients: a deletion in intron 9 leading to p.P423_H503del, a delins variant at p.P154, and point variants p.V161D, p.R264C, p.R375C. Except for R264C, all variants showed a loss of function. Protein structure and dynamics studies were in line with functional assays. The 2 female patients with delins variants manifested with ambiguous genitalia at birth. Histologic investigation revealed normal ovarian tissue on one side and a streak gonad on the other. Two female patients presented with abnormal pubertal development and polycystic ovaries.

Conclusion

In girls, aromatase deficiency usually manifests at birth, but diagnosis may also be made because of abnormal pubertal development or ovarian torsion due to (poly)cystic ovaries. The ovary harboring CYP19A1 variants may present as streak gonad or appears normal at birth, but is then at very high risk to produce cysts with aging and is therefore prone to ovarian torsion.

Effects of 5-Hydroxymethylfurfural on Pubertal Development of Female Wistar Rats

OBJECTIVE

5-Hydroxymethylfurfural (HMF) is formed when sugars are heated in the presence of amino acids. HMF is naturally present in many foods. To investigate the toxic effects of HMF on the reproductive system of peripubertal rats.

METHODS

In the study, 24 immature female Wistar rat were divided into three groups: control (CT) fed with no HMF; low dose fed with 750 mg/kg/day of HMF and high dose (HD) groups fed with 1500 mg/kg/day of HMF. All groups received these diets for three weeks from postnatal day (PND) 21. The vaginal opening (VO) was monitored daily and euthanasia occurred on PND 44. Gonadotropin, estradiol (E2), progesterone and anti-Müllerian hormone (AMH) concentrations were measured. Reproductive organ weights and ovarian follicle counts were compared.

RESULTS

The HD HMF group had earlier VO. Higher mean luteinising hormone (2.9±1.2 vs 1.3±0.3 mIU/mL) and mean E2 (34.7±8.8 vs 21.2±3.9 pg/mL) and lower mean AMH (2.7±0.5 vs 4.7±0.7 ng/mL) concentrations were found in the HD compared to the CT group. The HD group also had increased number of secondary atrophic follicles.

CONCLUSION

These results indicate that peripubertal exposure to HMF at HD result in precocious puberty and decreased AMH levels in female Wistar rats.

Nanoplastics Cause Neurobehavioral Impairments, Reproductive and Oxidative Damages, and Biomarker Responses in Zebrafish: Throwing up Alarms of Wide Spread Health Risk of Exposure

Plastic pollution is a growing global emergency and it could serve as a geological indicator of the Anthropocene era. Microplastics are potentially more hazardous than macroplastics, as the former can permeate biological membranes. The toxicity of microplastic exposure on humans and aquatic organisms has been documented, but the toxicity and behavioral changes of nanoplastics (NPs) in mammals are scarce. In spite of their small size, nanoplastics have an enormous surface area, which bears the potential to bind even bigger amounts of toxic compounds in comparison to microplastics. Here, we used polystyrene nanoplastics (PS-NPs) (diameter size at ~70 nm) to investigate the neurobehavioral alterations, tissue distribution, accumulation, and specific health risk of nanoplastics in adult zebrafish. The results demonstrated that PS-NPs accumulated in gonads, intestine, liver, and brain with a tissue distribution pattern that was greatly dependent on the size and shape of the NPs particle. Importantly, an analysis of multiple behavior endpoints and different biochemical biomarkers evidenced that PS-NPs exposure induced disturbance of lipid and energy metabolism as well as oxidative stress and tissue accumulation. Pronounced behavior alterations in their locomotion activity, aggressiveness, shoal formation, and predator avoidance behavior were exhibited by the high concentration of the PS-NPs group, along with the dysregulated circadian rhythm locomotion activity after its chronic exposure. Moreover, several important neurotransmitter biomarkers for neurotoxicity investigation were significantly altered after one week of PS-NPs exposure and these significant changes may indicate the potential toxicity from PS-NPs exposure. In addition, after ~1-month incubation, the fluorescence spectroscopy results revealed the accumulation and distribution of PS-NPs across zebrafish tissues, especially in gonads, which would possibly further affect fish reproductive function. Overall, our results provided new evidence for the adverse consequences of PS-NPs-induced behavioral dysregulation and changes at the molecular level that eventually reduce the survival fitness of zebrafish in the ecosystem.

Roles of poly (ADP-ribose) polymerase 1 activation and cleavage in induction of multi-oocyte ovarian follicles in the mouse by 3-nitropropionic acid

3-nitropropionic acid (3-NPA) is known to be a mitochondrial toxin produced by plants and fungi, which may produce DNA damage in cells. However, studies of its reproductive toxicology are lacking. We know that poly(ADP-ribose) polymerase (PARP) plays an important role in a large variety of physiological processes and is involved in DNA repair pathways. The present study was therefore aimed at exploring the involvement of PARP-1 activation and cleavage after 3-NPA stimulation in female mice. We observed an increased number of atretic follicles and multi-oocyte follicles (MOFs) after treatment with 3-NPA and serum concentrations of 17β-oestradiol and progesterone were significantly reduced. Our results provide evidence that PARP-1 cleavage and activational signals are involved in pathological ovarian processes stimulated by 3-NPA. In addition, total superoxide dismutase, glutathione peroxidase and catalase activities were significantly increased, whereas succinate dehydrogenase was decreased in a dose-dependent manner. Results from our in vitro study similarly indicated that 3-NPA inhibited the proliferation of mouse granulosa cells and increased apoptosis in a dose-dependent manner. In summary, 3-NPA induces granulosa cell apoptosis, follicle atresia and MOFs in the ovaries of female mice and causes oxidative stress so as to disrupt endogenous hormonal systems, possibly acting through PARP-1 signalling.

17α-Estradiol promotes ovarian aging in growth hormone receptor knockout mice, but not wild-type littermates

Growth hormone receptor knockout mice (GHRKO) have reduced body size and increased insulin sensitivity. These mice are known for having extended lifespan, healthspan and female reproductive longevity. Seventeen α-estradiol (17α-E2) is reported to increase insulin sensitivity and extend lifespan in male mice, with less robust effects in female mice. The aim of this study was to evaluate the ovarian reserve in wild type and GHRKO mice treated with 17α-E2. The mice were divided into four groups, GHRKO mice receiving a standard chow diet, GHRKO mice treated 17α-E2, wild type mice receiving a standard chow diet and WT mice treated with 17α-E2. 17α-E2 was provided in the diet for four months. IGF1 plasma concentrations and changes in body weight were assessed. Histological slides were prepared from the ovaries and the number of follicles was counted. GHRKO mice receiving the control diet had a greater number of primordial follicles and lower numbers of primary follicles compared to the other groups (p < 0.05). 17α-E2 treatment decreased the number of primordial follicles in GHRKO mice (p < 0.05), however had no effect in wild type mice. Treatment with 17α-E2 had no significant effect on the change in body weight during the experiment (p = 0.75). Plasma IGF1 concentrations were significantly lower in GHRKO mice as compared to wild type. In conclusion, we found that GHRKO mice displayed lesser primordial follicle activation as compared to wild type mice, but this phenotype was reversed by 17α-E2 administration, suggesting that ovarian aging is increased by 17α-E2 in long-living mice with extended reproductive longevity.

Immuno expression pattern of proliferating cell nuclear antigen (PCNA) in normal and atretic follicles of buffalo ovary

The present study was aimed to determine the expression pattern of PCNA in normal and atretic follicles of buffalo ovary. PCNA was localized specifically in the nucleus of the different types of cells in the ovary of buffalo. It was localized in the follicular cells of primordial and primary follicles, granulosa cells in secondary follicles and in all the compartments of a healthy tertiary follicle. The atretic follicles revealed weak PCNA expression. PCNA expression varied in different degrees of atresia and during different seasons.

Neonatal exposure to a glyphosate-based herbicide alters the histofunctional differentiation of the ovaries and uterus in lambs

The aim of the present study was to compare the effect of oral and subcutaneous exposure to a glyphosate-based herbicide (GBH) on the female reproductive system, specifically in the ovaries and uterus of prepubertal lambs. To this end, ewe lambs were exposed to a s.c. (n: 5) or an oral (n: 5) environmentally relevant dose of GBH (2 mg/kg/day) or to vehicle (controls, n: 12), from postnatal day (PND) 1 to PND14. Serum glyphosate and aminomethylphosphonic acid (AMPA) concentrations were measured on PND15 and PND45. The ovaries and uterus were obtained and weighed on PND45. Ovarian follicular dynamics and uterine morphological features were determined by picrosirius-hematoxylin staining. The proliferation marker Ki67 was evaluated by immunohistochemistry in ovarian and uterine samples. Glyphosate but not AMPA was detected in serum of exposed lambs on PND15, whereas neither glyphosate nor AMPA were detected on PND45. Controls were negative for glyphosate and AMPA on PND15 and PND45. GBH exposure did not affect ovarian or uterine weight. However, on PND45, the ovary of GBH-exposed lambs showed altered follicular dynamics, increased proliferation of granulosa and theca cells, and decreased mRNA expression of FSHR and GDF9, whereas their uterus showed decreased cell proliferation but no alterations in the histomorphology or gene expression. In conclusion, GBH exposure altered the ovarian follicular dynamics and gene expression, and the proliferative activity of the ovaries and uterus of lambs. It is noteworthy that all the adverse effects found in the ovaries and uterus of both GBH-exposed groups were similar, independently of the administration route.

The effects of dietary levels of genistein on ovarian follicle number and gene expression

Genistein is a phytoestrogen found in soy. We previously found that adult exposure to dietary levels of genistein affected gestation time, parturition time, litter size, pup weight, and pup mortality in CD-1 mice. The present study investigated the effects of adult genistein exposure on follicle number and gene expression in the ovaries of CD-1 mice. We found that exposure to genistein had no effect on follicle number, but it did affect the expression of apoptotic regulatory genes (Bax, Bcl-2, Bid, and Dffa) in the ovary.

Programmed cell death in the human ovary

During a woman's reproductive life, only about 400 primordial follicles will develop into a preovulatory follicle and undergo ovulation, releasing an oocyte available for fertilization. The process of formation and selection of these follicles is complex and involves a multistep process characterized by a balance between survival and death of the oocytes and the surrounding follicular cells. Although the mechanisms underlying such process are not completely clarified yet, it is common idea that they can occur through various types of programmed cellular death (PCD). Since atresia is the principal destiny of the ovarian follicles, it is relevant to understand how this process takes place and how it is regulated. In this review, after a summary description of folliculogenesis in humans, the main mechanisms of atresia reported to occur during folliculogenesis from birth to adult age, in the human ovary and in other mammals when appropriate, are described.

Effect of (R)-(+) Pulegone on Ovarian Tissue; Correlation with Expression of Aromatase Cyp19 and Ovarian Selected Genes in Mice

Objective

Pulegone (PGN) is a monoterpene ketone, whose metabolites exert several cytotoxic effects in various tissues. The present study was conducted in order to evaluate the (R)-(+) PGN-induced alterations in ovarian aromatization, proto-oncogenes and estrogen receptorα (ERα) and ERβ receptors expressions.

Materials and Methods

In this experimental study, mature albino mice were divided into experimental (received 25 mg/kg, 50 mg/kg and 100 mg/kg PGN, orally for 35 days) and control (received 2% solution of Tween 80 as a PGN solvent, orally) groups. The mRNA levels of Erα, Erβ, p53, Bcl-2, and cytochrome p450 (Cyp19) as well as ovarian angiogenesis were analyzed through reverse transcription polymerase chain reaction and immunohistochemical techniques, respectively. Moreover, apoptosis of follicular cells, serum estrogen and progesterone levels and mRNA damage were investigated via using terminal transferase and biotin-16-dUTP staining, electrochemilunescence and fluorescent microscopy methods, respectively.

Results

The PGN reduced Erα, Erβ and Cyp19 expression at 50 mg/kg and 100 mg/kg doses, while significantly elevating p53 and reducing Bcl-2 expression. Finally, PGN impaired ovarian angiogenesis, increased apoptosis, elevated follicular atresia and reduced serum levels of estrogen and progesterone.

Conclusion

Chronic exposure to PGN (50 mg/kg and 100 mg/kg), severely affects ovarian aromatization, proto- oncogenes mRNA levels and expression of ERs.

Untapped Reserves: Controlling Primordial Follicle Growth Activation

Even with the benefit of assisted reproductive technologies (ART), many women are unable to conceive and deliver healthy offspring. One common cause of infertility is the inability to produce eggs capable of contributing to live birth. This can occur despite standard-of-care treatment to maximize the recovery of eggs from growing ovarian follicles. Dormant primordial follicles in the human ovary are a 'reserve ' that can be exploited clinically to overcome this problem. We discuss how controlling primordial follicle growth activation (PFGA) can produce increased numbers of high-quality eggs available for fertility treatment(s). We consider the state of the art in interventions used to control PFGA, and consider genetic and epigenetic strategies on the horizon that might improve compromised oocyte quality to increase live births.

Mobile phone (1800MHz) radiation impairs female reproduction in mice, Mus musculus, through stress induced inhibition of ovarian and uterine activity

Present study investigated the long-term effects of mobile phone (1800MHz) radiation in stand-by, dialing and receiving modes on the female reproductive function (ovarian and uterine histo-architecture, and steroidogenesis) and stress responses (oxidative and nitrosative stress). We observed that mobile phone radiation induces significant elevation in ROS, NO, lipid peroxidation, total carbonyl content and serum corticosterone coupled with significant decrease in antioxidant enzymes in hypothalamus, ovary and uterus of mice. Compared to control group, exposed mice exhibited reduced number of developing and mature follicles as well as corpus lutea. Significantly decreased serum levels of pituitary gonadotrophins (LH, FSH), sex steroids (E2 and P4) and expression of SF-1, StAR, P-450scc, 3β-HSD, 17β-HSD, cytochrome P-450 aromatase, ER-α and ER-β were observed in all the exposed groups of mice, compared to control. These findings suggest that mobile phone radiation induces oxidative and nitrosative stress, which affects the reproductive performance of female mice.

Effects of in vitro exposure to butylparaben and di-(2 ethylhexyl) phthalate, alone or in combination, on ovarian function

Parabens and phthalates are commercial chemicals widely used in the manufacture of industrial and consumer products frequently found as contaminants in biological fluids. We evaluated the effects of di-(2-ethylhexyl) phthalate (DEHP) (ranging from 10(-9) to 10(-7) m [1-100 nm; 0.39-39 ng ml(-1) ]) and butylparaben (BP) (ranging from 10(-8) to 10(-5) m [10 nm-10 μm; 1.9 ng ml(-1) to 1.9 μg ml(-1) ]), alone and in combination, on isolated mouse preantral follicle and human granulosa cell (hGC) cultures to study direct effects on follicle growth and ovarian steroidogenesis. Our results revealed that, in follicle culture, DEHP and BP attenuate estradiol output but only when present together. DEHP decreases progesterone concentrations in the spent media of hGC cultures, an effect that was attenuated when BP was added together with DEHP. Although changes in steroidogenesis were observed, no effects on follicular development or survival were noted in the culture systems. We suggest that BP and DEHP act with additive effect to decrease estradiol production whereas at later stages of follicle development BP blocks the effect of DEHP in hGCs resulting in decreased progesterone output. Taken together our results suggest that DEHP and BP adversely affect steroidogenesis from the preantral stage onward and the effects of these chemicals are both stage-dependent and modified by co-exposure. Copyright © 2016 John Wiley & Sons, Ltd.

Chronic Exposure of Female Mice to an Environmental Level of Perfluorooctane Sulfonate Suppresses Estrogen Synthesis Through Reduced Histone H3K14 Acetylation of the StAR Promoter Leading to Deficits in Follicular Development and Ovulation

Perfluorooctane sulfonate (PFOS) at a high dose of 10 mg/kg has been reported to affect the neuroendocrine system and exert toxic effects in rodents. The present study examined the influence of chronic exposure to a low-dose of PFOS (0.1 mg/kg/day) on female reproductive endocrine and function. Herein, we show that adult female mice exposed to PFOS by gavage for 4 months (PFOS-mice) exhibited a prolongation of diestrus without signs of toxic effects. The numbers of mature follicles and corpora luteum were significantly reduced in PFOS-mice with increase of atresic follicles. The levels of serum estrogen (E2) and progesterone at proestrus and diestrus were reduced in PFOS-mice. In comparison with controls, PFOS-mice showed a significant decrease in the levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH), and gonadotrophin-releasing hormone, the number of kisspeptin neurons and the level of kiss1 mRNA in anteroventral periventricular nucleus at proestrus but not at diestrus, which could be corrected with the normalization to E2. PFOS-mice did not generate an LH-surge at proestrus, which could be rescued by the application of E2 or kisspeptin-10. Notably, the level of ovarian steroidogenic acute regulatory (StAR) mRNA was decreased in PFOS-mice with the reduction of histone H3K14 acetylation in StAR promoter relative to control mice, whereas the P450scc expression and histone H3K14 acetylation showed no difference between the groups. The present study provides evidence that the chronic exposure to the low-dose of PFOS through selectively reducing histone acetylation of StAR suppresses the biosynthesis of E2 to impair the follicular development and ovulation.

The developmental origins of the mammalian ovarian reserve

The adult mammalian ovary is devoid of definitive germline stem cells. As such, female reproductive senescence largely results from the depletion of a finite ovarian follicle pool that is produced during embryonic development. Remarkably, the crucial nature and regulation of follicle assembly and survival during embryogenesis is just coming into focus. This developmental pathway involves the coordination of meiotic progression and the breakdown of germ cell cysts into individual oocytes housed within primordial follicles. Recent evidence also indicates that genetic and environmental factors can specifically perturb primordial follicle assembly. Here, we review the cellular and molecular mechanisms by which the mammalian ovarian reserve is established, highlighting the presence of a crucial checkpoint that allows survival of only the highest-quality oocytes.

Effects of GnRH agonists on the expression of developmental follicular anti-mullerian hormone in varying follicular stages in cyclic mice in vivo

Gonadotrophin‑releasing hormone (GnRH) agonists (GnRHa) have been widely used to induce a state of downregulation for in vitro fertilization, and its direct effects on the pituitary are well known. However, the effects of GnRHa on the expression of anti‑mullerian hormone (AMH) by follicles in varying stages in vivo remain to be fully elucidated. In the present study 84 cyclic mice were randomly divided equally into four GnRHa groups and three cyclic mice were used as a control group. The expression levels of AMH in follicles of varying stages between days 0 and 7 following GnRHa administration were quantified using immunohistochemistry. The expression of AMH in follicles at various stages revealed dynamic changes during the process of downregulation. AMH in primary follicles initially increased and then decreased gradually. In small and large preantral follicles and in granulosa cells (GCs) surrounding the oocyte of small antral follicles, the expression of AMH began to increase on day 1, was attenuated on day 2, and then increased to a peak. The expression levels of AMH in the GCs surrounding the basement membrane, in contrast to the GCs surrounding the oocyte, were significantly lower and did not increase on day 1. In all stages of follicles, the expression of AMH declined gradually between the peak level and last day of downregulation. On day 7, the varying follicular stages all expressed lower levels of AMH than on day 0. This decrease was more prominent in the higher dose groups, compared with the lower dose groups. In conclusion, GnRHa was observed to induce time‑dependent changes in the expression of AMH at varying follicular stages, which occurred in a dose‑dependent manner.

Cellular and molecular regulation of the activation of mammalian primordial follicles: somatic cells initiate follicle activation in adulthood

BACKGROUND

The first small follicles to appear in the mammalian ovaries are primordial follicles. The initial pool of primordial follicles serves as the source of developing follicles and oocytes for the entire reproductive lifespan of the animal. Although the selective activation of primordial follicles is critical for female fertility, its underlying mechanisms have remained poorly understood.

METHODS

A search of PubMed was conducted to identify peer-reviewed literature pertinent to the study of mammalian primordial follicle activation, especially recent reports of the role of primordial follicle granulosa cells (pfGCs) in regulating this process.

RESULTS

In recent years, molecular mechanisms that regulate the activation of primordial follicles have been elucidated, mostly through the use of genetically modified mouse models. Several molecules and pathways operating in both the somatic pfGCs and oocytes, such as the phosphatidylinositol 3 kinase (PI3K) and the mechanistic target of rapamycin complex 1 (mTORC1) pathways, have been shown to be important for primordial follicle activation. More importantly, recent studies have provided an updated view of how exactly signaling pathways in pfGCs and in oocytes, such as the KIT ligand (KL) and KIT, coordinate in adult ovaries so that the activation of primordial follicles is achieved.

CONCLUSIONS

In this review, we have provided an updated picture of how mammalian primordial follicles are activated. The functional roles of pfGCs in governing the activation of primordial follicles in adulthood are highlighted. The in-depth understanding of the cellular and molecular mechanisms of primordial follicle activation will hopefully lead to more treatments of female infertility, and the current progress indicates that the use of existing primordial follicles as a source for obtaining fertilizable oocytes as a new treatment for female infertility is just around the corner.

Short term exposure to di-n-butyl phthalate (DBP) disrupts ovarian function in young CD-1 mice

Di-n-butyl phthalate (DBP) is present in many beauty and medical products. Human exposure estimates range from 0.007-0.01 mg/kg/day in the general population and up to 0.233 mg/kg/day in patients taking DBP-coated medications. Levels of phthalates tend to be higher in women, thus, evaluating ovarian effects of DBP exposure is of great importance. Mice were given corn oil (vehicle) or DBP at 0.01, 0.1, and 1000 mg/kg/day (high dose) for 10 days to test whether DBP causes ovarian toxicity. Estrous cyclicity, steroidogenesis, ovarian morphology, and apoptosis and steroidogenesis gene expression were evaluated. DBP exposure decreased serum E2 at all doses, while 0.1DBP increased FSH, decreased antral follicle numbers, and increased mRNA encoding pro-apoptotic genes (Bax, Bad, Bid). Interestingly, mRNAs encoding the steroidogenic enzymes Hsd17b1, Cyp17a1 and Cyp19a1 were increased in all DBP-treated groups. These novel findings show that DBP can disrupt ovarian function in mice at doses relevant to humans.

Effect of azaline B on follicular development and functions in the hamster

The usefulness of azaline B, a GnRH antagonist, in suppressing gonadotropin secretion in the golden hamster was examined by examining follicular development, steroidogenesis and expression of steroidogenic enzymes. Serum levels of P and E declined significantly, while FSH or LH was undetectable in azaline B-treated hamsters. FSH significantly increased serum E levels, whereas LH upregulated serum P levels. The formation of antral follicles ceased in azaline-treated hamsters, but was reversed by FSH with or without LH supplement. FSH also activated the primordial follicle pool resulting in increased formation of primary and preantral follicles. Further, an increasing trend in the formation of preantral follicles in response to E or E + P, and the formation of antral follicles in response to E + P treatment was evident. The level of Cyp11a1 mRNA increased markedly in LH- or LH + FSH-treated hamsters, whereas FSH with or without LH upregulated Cyp17a1, Cyp19a1 and Fshr mRNA expression. E without or with P also upregulated ovarian Cyp19a1 mRNA expression. The expression of enzyme protein corroborated the mRNA data. In summary, azaline B is an efficient GnRH antagonist in the hamster, and will be useful in studying the selective effect of gonadotropins on ovarian functions without disrupting the physiological functions of other hormones in ovarian cells.

Low-density lipoprotein receptor affects the fertility of female mice

Low-density lipoprotein receptor (LDLR) has been demonstrated to play a central role in lipoprotein metabolism, with Ldlr-deficient (Ldlr–/–) mice developing severe dyslipidemia. In the present study we investigated whether Ldlr knockout could harm female reproduction and explored the mechanisms involved. The results indicate that although the number of litters born to Ldlr–/– mice did not differ significantly from that born to controls, the number of pups per litter was significantly lower in the former group. Interestingly, although Ldlr–/– mice were obese, the weight of their ovaries was lower than that in control mice. Serum cholesterol levels was significantly higher in Ldlr–/– mice than in their wild-type counterparts. In contrast, there were significant decreases in cholesterol, triglyceride and total lipid levels in ovaries of Ldlr–/– mice. Both ovarian lipid deposition, as detected by Oil red O staining, and lipid droplets, as evaluated by transmission electron microscopy, supported decreased lipid levels in ovaries from Ldlr–/– mice. In addition, Ldlr–/– mice had fewer ovarian follicles, more atretic follicles, lower oestrogen levels and spent significantly less time in oestrus than did the controls. Superovulation assays indicated immature Ldlr–/– mice ovulated fewer ova than controls. These results indicate that lack of Ldlr results in dyslipidaemia and poor fertility.

Through the smoke: use of in vivo and in vitro cigarette smoking models to elucidate its effect on female fertility

A finite number of oocytes are established within the mammalian ovary prior to birth to form a precious ovarian reserve. Damage to this limited pool of gametes by environmental factors such as cigarette smoke and its constituents therefore represents a significant risk to a woman's reproductive capacity. Although evidence from human studies to date implicates a detrimental effect of cigarette smoking on female fertility, these retrospective studies are limited and present conflicting results. In an effort to more clearly understand the effect of cigarette smoke, and its chemical constituents, on female fertility, a variety of in vivo and in vitro animal models have been developed. This article represents a systematic review of the literature regarding four of experimental model types: 1) direct exposure of ovarian cells and follicles to smoking constituents' in vitro, 2) direct exposure of whole ovarian tissue with smoking constituents in vitro, 3) whole body exposure of animals to smoking constituents and 4) whole body exposure of animals to cigarette smoke. We summarise key findings and highlight the strengths and weaknesses of each model system, and link these to the molecular mechanisms identified in smoke-induced fertility changes.

Progressive obesity alters ovarian folliculogenesis with impacts on pro-inflammatory and steroidogenic signaling in female mice

Diet-induced obesity induces immune cell infiltration and inflammation in peri-ovarian adipose tissue and mRNA expression of inflammatory markers in ovarian tissue. Whether these changes are associated with obesity-related ovarian dysfunction remains unknown. In the present study, qRT-PCR and Western blotting techniques were used to compare mRNA and protein abundance of ovarian immune cell and inflammation markers, along with NF-kappaB and steroidogenic pathway members in normal wild-type non-agouti (a/a; lean) and lethal yellow mice (KK.CG-A(y/)J; obese) at 6, 12, 18, or 24 wk of age. Our data revealed that, beginning at 12 wk of age, NF-kappaB inflammatory signaling members were elevated (P < 0.05) in obese females. Interestingly obesity had opposing and temporal effects on the steroidogenic enzyme pathway. Obesity decreased (P < 0.05) STAR protein at 12, 18, and 24 wk of age. CYP11A1 and CYP19A1 proteins were increased (P < 0.05) at 12 wk but were decreased (P < 0.05) at 18 and 24 wk. Interestingly, CYP19A1 was increased in lethal yellow mouse ovaries at 6 wk of age, potentially indicating early puberty onset. These data demonstrate that obesity alters expression of ovarian inflammatory and steroidogenic pathway genes in ways which could adversely affect ovarian function.

Development of mammalian ovary

Pre-natal and early post-natal ovarian development has become a field of increasing importance over recent years. The full effects of perturbations of ovarian development on adult fertility, through environmental changes or genetic anomalies, are only now being truly appreciated. Mitigation of these perturbations requires an understanding of the processes involved in the development of the ovary. Herein, we review some recent findings from mice, sheep, and cattle on the key events involved in ovarian development. We discuss the key process of germ cell migration, ovigerous cord formation, meiosis, and follicle formation and activation. We also review the key contributions of mesonephric cells to ovarian development and propose roles for these cells. Finally, we discuss polycystic ovary syndrome, premature ovarian failure, and pre-natal undernutrition; three key areas in which perturbations to ovarian development appear to have major effects on post-natal fertility.