Establishment and depletion of the ovarian reserve: physiology and impact of environmental chemicals

Effectiveness of naturopathy for pregnancy in women with diminished ovarian reserve: feasibility randomized controlled trial

RESEARCH QUESTION

Is conducting a randomized control trial (RCT) to assess the effectiveness of whole-system naturopathy in improving pregnancy rates among women with diminished ovarian reserve (DOR) feasible?

DESIGN

A two-arm, parallel group, assessor-blinded feasibility RCT was conducted. Women with DOR, trying to conceive naturally or by ART, were randomly assigned to naturopathy plus usual care, or usual care alone for 16 weeks. Primary outcomes were feasibility (recruitment, adherence, retention rates), acceptability and safety. Secondary outcomes included ongoing pregnancy rates, live birth rates and health-related outcomes (mental health, quality of life, diet, exercise, sleep and weight). Statistical significance of the differences between the two groups (P-values) were exploratory.

RESULTS

One hundred and fifteen women completed the screening survey between March and November 2022. Of these, 66 women were assessed for eligibility and 41 (62%) consented. Recruitment resulted in seven enrolments each month. All 41 participants (100%) adhered to the intervention, 38 (93%) completed end-point questionnaires, 32 (78%) found study participation to be acceptable and 18 out of 21 (86%) from the intervention group would recommend a naturopathic intervention to other women with DOR. The naturopathic treatment was associated with only mild and temporary adverse events. No between-group differences were observed for pregnancy and live birth rates.

CONCLUSION

The evaluation of whole-system naturopathy through a RCT was feasible and the treatment was acceptable and well tolerated according to women with DOR. Outcomes from this study will help inform sample size calculations powered for fertility outcomes for future RCTs on this topic.

The crucial role of HFM1 in regulating FUS ubiquitination and localization for oocyte meiosis prophase I progression in mice

BACKGROUND

Helicase for meiosis 1 (HFM1), a putative DNA helicase expressed in germ-line cells, has been reported to be closely associated with premature ovarian insufficiency (POI). However, the underlying molecular mechanism has not been clearly elucidated. The aim of this study was to investigate the function of HFM1 in the first meiotic prophase of mouse oocytes.

RESULTS

The results suggested that the deficiency of HFM1 resulting in increased apoptosis and depletion of oocytes in mice, while the oocytes were arrested in the pachytene stage of the first meiotic prophase. In addition, impaired DNA double-strand break repair and disrupted synapsis were observed in the absence of HFM1. Further investigation revealed that knockout of HFM1 promoted ubiquitination and degradation of FUS protein mediated by FBXW11. Additionally, the depletion of HFM1 altered the intranuclear localization of FUS and regulated meiotic- and oocyte development-related genes in oocytes by modulating the expression of BRCA1.

CONCLUSIONS

These findings elaborated that the critical role of HFM1 in orchestrating the regulation of DNA double-strand break repair and synapsis to ensure meiosis procession and primordial follicle formation. This study provided insights into the pathogenesis of POI and highlighted the importance of HFM1 in maintaining proper meiotic function in mouse oocytes.

3-Methyl-4-nitrophenol Exposure Deteriorates Oocyte Maturation by Inducing Spindle Instability and Mitochondrial Dysfunction

3-methyl-4-nitrophenol (PNMC), a well-known constituent of diesel exhaust particles and degradation products of insecticide fenitrothion, is a widely distributed environmental contaminant. PNMC is toxic to the female reproductive system; however, how it affects meiosis progression in oocytes is unknown. In this study, in vitro maturation of mouse oocytes was applied to investigate the deleterious effects of PNMC. We found that exposure to PNMC significantly compromised oocyte maturation. PNMC disturbed the spindle stability; specifically, it decreased the spindle density and increased the spindle length. The weakened spindle pole location of microtubule-severing enzyme Fignl1 may result in a defective spindle apparatus in PNMC-exposed oocytes. PNMC exposure induced significant mitochondrial dysfunction, including mitochondria distribution, ATP production, mitochondrial membrane potential, and ROS accumulation. The mRNA levels of the mitochondria-related genes were also significantly impaired. Finally, the above-mentioned alterations triggered early apoptosis in the oocytes. In conclusion, PNMC exposure affected oocyte maturation and quality through the regulation of spindle stability and mitochondrial function.

Chlorothalonil exposure compromised mouse oocyte in vitro maturation through inducing oxidative stress and activating MAPK pathway

Chlorothalonil (CTL) is widely used in agricultural production and antifoulant additive globally due to its broad spectrum and non-systemic properties, resulting in its widespread existence in foods, soil and water. Extensive evidence demonstrated that exposure to CTL induced adverse effects on organisms and in particular its reproductive toxicity has been attracted public concern. However, the influences of CTL on oocyte maturation is mysterious so far. In this study, we documented the toxic effects of CTL on oocyte in vitro maturation and the related underlying mechanisms. Exposure to CTL caused continuous activation of spindle assembly checkpoints (SAC) which in turn compromised meiotic maturation in mouse oocyte, featured by the attenuation of polar body extrusion (PBE). Detection of cytoskeletal dynamics demonstrated that CTL exposure weakened the acetylation level of α-tubulin and impaired meiotic spindle apparatus, which was responsible for the aberrant state of SAC. Meanwhile, exposure to CTL damaged the function of mitochondria, inducing the decline of ATP content and the elevation of reactive oxygen species (ROS), which thereby induced early apoptosis and DNA damage in mouse oocytes. In addition, exposure to CTL caused the alteration of the level of histone H3 methylation, indicative of the harmful effects of CTL on epigenetic modifications in oocytes. Further, the CTL-induced oxidative stress activated mitogen-activated protein kinase (MAPK) pathway and injured the maturation of oocytes. In summary, exposure to CTL damaged mouse oocyte in vitro maturation via destroying spindle assembly, inducing oxidative stress and triggering MAPK pathway activation.

Melatonin alleviates the toxic effect of di(2-ethylhexyl) phthalate on oocyte quality resulting from CEBPB suppression during primordial follicle formation

Presently, the exposure of plasticizers to humans and animals occurs daily, which pose a potential threat to reproductive health. In the present study, a pregnant mouse model exposed to di(2-ethylhexyl) phthalate (DEHP, one of the most common plasticizers) and melatonin was established, and the single-cell transcriptome technology was applied to investigate the effects of melatonin in ovarian cells against DEHP. Results showed that DEHP markedly altered the gene expression pattern of ovarian cells, and severely weakened the histone methylation modification of oocytes. The administration of melatonin recovered the expression of LHX8 and SOHLH1 proteins that essential for primordial follicle formation, and increased the expression of CEBPB, as well as key genes of histone methylation modification (such as Smyd3 and Kdm5a). In addition, the ovarian damage caused by DEHP was also relieved after the overexpression of CEBPB, which suggested melatonin could improve primordial follicle formation progress via enhancing CEBPB expression in mice. Besides, the apoptosis of ovarian cells induced by DEHP also was diminished by melatonin. The study provides evidence of melatonin preventing the damage mediated by plasticizers on the reproductive system in females and CEBPB may serve as a downstream target factor of melatonin in the process.

Downregulation of homeobox A1 in human granulosa cells is involved in diminished ovarian reserve through promoting cell apoptosis and mitochondrial dysfunction

Granulosa cell apoptosis contributes to the occurrence of diminished ovarian reserve (DOR). HOXA1, belonging to the HOX gene family, is involved in regulating cancer cell apoptosis. However, whether HOXA1 participates in the granulosa cell apoptosis in DOR patients remains to be elucidated. In the current study, we demonstrated the differential transcriptomic landscape of granulosa cells in DOR patients compared to that in the controls and identified decreased expression of the HOXA1 gene. Meanwhile, we found that HOXA1 was a gonadotropin-response gene, in which FSH could promote its expression, whereas LH inhibited HOXA1 expression in human granulosa cells. CCK-8 assay, flow cytometry and TUNEL staining results showed that inhibition of endogenous HOXA1 expression promoted human granulosa cell apoptosis. Moreover, knockdown of HOXA1 increased Bax while reducing Bcl2 protein expression. Furthermore, we found a total of 947 differentially expressed genes (DEGs), including 426 upregulated genes and 521 downregulated genes using transcriptome sequencing technology. Enrichment analysis results showed that the DEGs were involved in apoptosis and mitochondrial function-related signaling pathways. Knockdown of HOXA1 impaired mitochondrial functions, exhibiting increased reactive oxygen species (ROS) and cytoplasmic Ca2+ levels, decreased mitochondrial membrane potential, ATP production and mitochondrial DNA (mtDNA) copy number, and abnormal mitochondrial cristae. Our findings demonstrated that aberrantly reduced HOXA1 expression induced granulosa cell apoptosis in DOR patients and impaired mitochondrial function, which highlighted the potential role of HOXA1 in the occurrence of DOR and provided new insight for the treatment of DOR.

Premature ovarian insufficiency: a review on the role of tobacco smoke, its clinical harm, and treatment

Premature ovarian insufficiency (POI) is a condition in which the quantity of follicles and the quality of oocytes gradually decrease. This results in an estrogen secretion disorder and abnormal follicle development, which can lead to related diseases, early onset of menopause, sexual dysfunction, and an increased risk of cardiovascular issues, osteoporosis, and depression, among others. This disease significantly impacts the physical and mental health and overall quality of life of affected women. Factors such as genetic abnormalities, oophorectomy, radiotherapy for malignancy, idiopathic conditions, and an unhealthy lifestyle, including smoking, can accelerate the depletion of the follicular pool and the onset of menopause. Extensive research has been conducted on the detrimental effects of tobacco smoke on the ovaries. This article aims to review the advancements in understanding the impact of tobacco smoke on POI, both in vivo and in vitro. Furthermore, we explore the potential adverse effects of common toxicants found in tobacco smoke, such as polycyclic aromatic hydrocarbons (PAHs), heavy metals like cadmium, alkaloids like nicotine and its major metabolite cotinine, benzo[a]pyrene, and aromatic amines. In addition to discussing the toxicants, this article also reviews the complications associated with POI and the current state of research and application of treatment methods. These findings will contribute to the development of more precise treatments for POI, offering theoretical support for enhancing the long-term quality of life for women affected by this condition.

Cyanidin-3-O-glucoside Mitigates the Ovarian Defect Induced by Zearalenone via p53-GADD45a Signaling during Primordial Follicle Assembly

Zearalenone (ZEN) is well known as a kind of endocrine disruptor whose exposure is capable of causing reproductive toxicity in animals. Cyanidin-3-O-glucoside (C3G) is a derivative of cyanidin and owns multiple biofunctions, and prior efforts have suggested that C3G has therapeutic actions for reproductive diseases. In this article, a ZEN exposure model during primordial follicle assembly was constructed using the in vitro culture platform of neonatal mouse ovaries. We investigated the protective effect of C3G on ZEN-induced ovarian toxicity during primordial follicle assembly in mice, as well as its potential mechanism. Interestingly, we observed that C3G could effectively protect the ovary from ZEN damage, mainly by restoring primordial follicle assembly, which upregulated the expression of LHX8 and SOHLH1 proteins and relieved ZEN-induced DNA damage. Next, to explore the mechanism by which C3G rescued ZEN-induced injury, we performed RNA sequencing (RNA-seq). The bioinformatic analysis illustrated that the rescue pathway of C3G was associated with p53-Gadd45a signaling and cell cycle. Then, western blotting and flow cytometry results revealed that C3G restored the expression levels of cyclin-dependent kinase 6 (CDK6) and cyclin D2 (CCND2) and regulated the ovarian cell cycle to normal. In conclusion, our findings manifested that C3G could alleviate ZEN-induced primordial follicle assembly impairment by restoring the cell cycle involved in p53-GADD45a signaling.

Regenerative Potential of Granulocyte Colony-Stimulating Factor Immobilized by Using Electron-Beam Synthesis Nanotechnology in an Experimental Model of Ovarian Reserve Depletion

The pharmacological activity of granulocyte CSF (G-CSF) immobilized using electron-beam synthesis nanotechnology (imG-CSF) was evaluated in an experimental model of ovarian reserve depletion. The effectiveness of the drug was compared with that of its unmodified form. Depletion of the ovarian follicular pool in female Sprague-Dawley rats was caused by a single intravenous injection of the antitumor drug etoposide in the maximum tolerated dose. The effectiveness of the studied drugs was assessed by serum concentration of anti-Mullerian hormone (AMH) measured by ELISA and by the number of primordial, two-layer, multilayer, and atretic follicles counted on serial sections of the ovaries (5-μm thick; through the entire organ) stained with hematoxylin and eosin. It was found that imG-CSF prevents depletion of the ovarian reserve in the model used, which was confirmed by high AMH concentration and higher numbers of primordial, two- and multilayer follicles in comparison with the corresponding parameters in the control (etoposide), and by a decrease in the severity of atretic processes. Unmodified form of the drug demonstrated lower efficiency.

Making a good egg: human oocyte health, aging, and in vitro development

Mammalian eggs (oocytes) are formed during fetal life and establish associations with somatic cells to form primordial follicles that create a store of germ cells (the primordial pool). The size of this pool is influenced by key events during the formation of germ cells and by factors that influence the subsequent activation of follicle growth. These regulatory pathways must ensure that the reserve of oocytes within primordial follicles in humans lasts for up to 50 years, yet only approximately 0.1% will ever be ovulated with the rest undergoing degeneration. This review outlines the mechanisms and regulatory pathways that govern the processes of oocyte and follicle formation and later growth, within the ovarian stroma, through to ovulation with particular reference to human oocytes/follicles. In addition, the effects of aging on female reproductive capacity through changes in oocyte number and quality are emphasized, with both the cellular mechanisms and clinical implications discussed. Finally, the details of current developments in culture systems that support all stages of follicle growth to generate mature oocytes in vitro and emerging prospects for making new oocytes from stem cells are outlined.

Quantitative analysis of ovarian surface photographs as a tool for assessment of chemical effects on folliculogenesis and ovulation in rats

Female reproductive toxicity assessments rely on histological evaluation of ovaries by hematoxylin & eosin (H&E)-stained cross-sections. This is time-consuming, labor-intensive and costly, thus alternative methods for ovarian toxicity assessment could be valuable. Here, we report on an improved method based on quantification of antral follicles (AF) and corpora lutea (CL) using ovarian surface photographs, called 'surface photo counting' (SPC). To validate a potential utility for the method to detect effects on folliculogenesis in toxicity studies, we investigated ovaries from rats exposed to two well-known endocrine disrupting chemicals (EDCs), diethylstilbestrol (DES) and ketoconazole (KTZ). Animals were exposed to DES (0.003, 0.012, 0.048 mg/kg body weight (bw)/day) or KTZ (3, 12, 48 mg/kg bw/day) during puberty or adulthood. At the end of the exposure, ovaries were photographed under stereomicroscope and subsequently processed for histological assessments to allow for direct comparison between the two methods by quantifying AF and CL. There was a significant correlation between the SPC and histology methods, albeit CL counts correlated better than AF counts, potentially due to their larger size. Effects of DES and KTZ were found by both methods, suggesting applicability of the SPC method to chemical hazard and risk assessment. Based on our study, we propose that SPC can be employed as a fast and cheap tool for assessment of ovarian toxicity in in vivo studies to prioritize chemical exposure groups for further histological assessment.

Gestational dibutyl phthalate exposure impairs primordial folliculogenesis in mice through autophagy activation and NOTCH2 signal interruption

Female reproductive lifespan is largely determined by the size of the primordial follicle pool, which is established in early life. Dibutyl phthalate (DBP), a popular plasticiser, is a known environmental endocrine disruptor that poses a potential threat to reproductive health. However, DBP impact on early oogenesis has been rarely reported. In this study, maternal exposure to DBP in gestation disrupted germ-cell cyst breakdown and primordial follicle assembly in foetal ovary, impairing female fertility in adulthood. Subsequently, altered autophagic flux with autophagosome accumulation was observed in DBP-exposed ovaries carrying CAG-RFP-EGFP-LC3 reporter genes, whereas autophagy inhibition by 3-methyladenine attenuated the impact of DBP on primordial folliculogenesis. Moreover, DBP exposure reduced the expression of NOTCH2 intracellular domain (NICD2) and decreased interactions between NICD2 and Beclin-l. NICD2 was observed within the autophagosomes in DBP-exposed ovaries. Furthermore, NICD2 overexpression partially restored primordial folliculogenesis. Furthermore, melatonin significantly relieved oxidative stress, decreased autophagy, and restored NOTCH2 signalling, consequently reversing the effect on folliculogenesis. Therefore, this study demonstrated that gestational DBP exposure disrupts primordial folliculogenesis by inducing autophagy, which targets NOTCH2 signalling, and this impact has long-term consequences on fertility in adulthood, strengthening the potential contribution of environmental chemicals to the development of ovarian dysfunctional diseases.

High-dose synthetic phenolic antioxidant propyl gallate impairs mouse oocyte meiotic maturation through inducing mitochondrial dysfunction and DNA damage

Propyl gallate (PG) is one of the most widely used antioxidants in food products, cosmetics and pharmaceutical industries. Increased research has suggested that exposure to PG influences reproductive health in humans and animals. However, until now, it has not yet been confirmed whether PG would impact oocyte quality. In this study, the hazardous effects of PG on oocyte meiotic maturation were investigated in mice. The findings showed that PG exposure compromises oocyte meiosis by inducing mitochondrial stress which activates apoptosis to trigger oocyte demise. Moreover, DNA damage was significantly induced in PG-treated oocytes, which might be another cause of oocyte developmental arrest and degeneration. Besides, the level of histone methylation (H3K27me2 and H3K27me3) in oocyte was also significantly increased by PG exposure. Furthermore, PG-induced oxidative stress was validated by the increased level of reactive oxygen species (ROS), which might be the underlying reason for these abnormities. In conclusion, the foregoing findings suggested that PG exposure impaired oocyte meiotic maturation by yielding mitochondrial stress to activate apoptosis, inducing DNA damage and oxidative stress, and altering histone methylation level.

Postnatal oogenesis leads to an exceptionally large ovarian reserve in naked mole-rats

In the long-lived naked mole-rat (NMR), the entire process of oogenesis occurs postnatally. Germ cell numbers increase significantly in NMRs between postnatal days 5 (P5) and P8, and germs cells positive for proliferation markers (Ki-67, pHH3) are present at least until P90. Using pluripotency markers (SOX2 and OCT4) and the primordial germ cell (PGC) marker BLIMP1, we show that PGCs persist up to P90 alongside germ cells in all stages of female differentiation and undergo mitosis both in vivo and in vitro. We identified VASA+ SOX2+ cells at 6 months and at 3-years in subordinate and reproductively activated females. Reproductive activation was associated with proliferation of VASA+ SOX2+ cells. Collectively, our results suggest that highly desynchronized germ cell development and the maintenance of a small population of PGCs that can expand upon reproductive activation are unique strategies that could help to maintain the NMR's ovarian reserve for its 30-year reproductive lifespan.

Epigenetic regulation in premature ovarian failure: A literature review

Premature ovarian failure (POF), or premature ovarian insufficiency (POI), is a multifactorial and heterogeneous disease characterized by amenorrhea, decreased estrogen levels and increased female gonadotropin levels. The incidence of POF is increasing annually, and POF has become one of the main causes of infertility in women of childbearing age. The etiology and pathogenesis of POF are complex and have not yet been clearly elucidated. In addition to genetic factors, an increasing number of studies have revealed that epigenetic changes play an important role in the occurrence and development of POF. However, we found that very few papers have summarized epigenetic variations in POF, and a systematic analysis of this topic is therefore necessary. In this article, by reviewing and analyzing the most relevant literature in this research field, we expound on the relationship between DNA methylation, histone modification and non-coding RNA expression and the development of POF. We also analyzed how environmental factors affect POF through epigenetic modulation. Additionally, we discuss potential epigenetic biomarkers and epigenetic treatment targets for POF. We anticipate that our paper may provide new therapeutic clues for improving ovarian function and maintaining fertility in POF patients.

Characterization of the Postnatal Naked Mole-Rat Ovary: From Primordial Germ Cells to Meiotic Prophase I Oocytes

The mammalian reproductive cycle, including those of humans and mice, begins very early in development. In utero, the ovaries become populated with primordial germ cells (PGCs) that will generate the oogonia. First, these cells proliferate mitotically, and then they trigger the meiotic program and initiate meiotic prophase I. Since these processes happen during gestation, their study had been very limited and challenging. Recently, we reported that, in the naked mole-rat (Heterocephalus glaber) ovary, there is mitotic expansion of the PGCs, and the initiation of the meiotic program occurs postnatally. In this chapter, we present a comprehensive collection of protocols that permit the analysis of naked mole-rat germ cells, from PGCs to oocytes, in meiotic prophase I, using in vivo and in vitro approaches.

Azoxystrobin exposure impairs meiotic maturation by disturbing spindle formation in mouse oocytes

Fungicides are a type of pesticide used to protect plants and crops from pathogenic fungi. Azoxystrobin (AZO), a natural methoxyacrylate derived from strobilurin, is one of the most widely used fungicides in agriculture. AZO exerts its fungicidal activity by inhibiting mitochondrial respiration, but its cytotoxicity to mammalian oocytes has not been studied. In this study, we investigated the effect of AZO exposure on mouse oocyte maturation to elucidate the underlying mechanisms of its possible reproductive toxicity. We found that AZO exposure disturbed meiotic maturation by impairing spindle formation and chromosome alignment, which was associated with decreased microtubule organizing center (MTOC) integrity. Moreover, AZO exposure induced abnormal mitochondrial distribution and increased oxidative stress. The AZO-induced toxicity to oocytes was relieved by melatonin supplementation during meiotic maturation. Therefore, our results suggest that AZO exposure impairs oocyte maturation not only by increasing oxidative stress and mitochondrial dysfunction, but also by decreasing MTOC integrity and subsequent spindle formation and chromosome alignment.

The effects of endocrine-disrupting chemicals on ovarian- and ovulation-related fertility outcomes

Exposure to endocrine-disrupting chemicals (EDCs) is unavoidable, which represents a public health concern given the ability of EDCs to target the ovary. However, there is a large gap in the knowledge about the impact of EDCs on ovarian function, including the process of ovulation. Defects in ovulation are the leading cause of infertility in women, and EDC exposures are contributing to the prevalence of infertility. Thus, investigating the effects of EDCs on the ovary and ovulation is an emerging area for research and is the focus of this review. The effects of EDCs on gametogenesis, uterine function, embryonic development, and other aspects of fertility are not addressed to focus on ovarian- and ovulation-related fertility issues. Herein, findings from epidemiological and basic science studies are summarized for several EDCs, including phthalates, bisphenols, per- and poly-fluoroalkyl substances, flame retardants, parabens, and triclosan. Epidemiological literature suggests that exposure is associated with impaired fecundity and in vitro fertilization outcomes (decreased egg yield, pregnancies, and births), while basic science literature reports altered ovarian follicle and corpora lutea numbers, altered hormone levels, and impaired ovulatory processes. Future directions include identification of the mechanisms by which EDCs disrupt ovulation leading to infertility, especially in women.

Association between environmental pollutants and the FSH/AMH ratio as a marker of ovarian reserve

The ovarian function decreases with age, and various markers, such as follicle stimulating hormone, inhibin B, antral follicle count, and anti-Müllerian hormone, are used for its evaluation. Recently, exposure to various environmental pollutants in daily life has been reported as an important cause of ovarian function decline. Therefore, the present study aimed to confirm the effect of environmental pollutants on the relationship between age and decline in ovarian function. The exposure levels of 16 environmental pollutants were evaluated in women aged 26-40 years, and the AMH levels and FSH/AMH ratios were used as markers for the decline of ovarian function. The participants were divided into two groups: low-level or high-level for each environmental pollutant if their exposure level was below or above the median respectively. The slope of the decrease or increase in the AMH level and FSH/AMH ratio of each group with age was evaluated. The FSH/AMH ratio better presented the difference in the rate of change with age in each group than did AMH alone. In particular, the rate of change in the FSH/AMH ratio increased 5.2 and 3.7 times (p<0.05) in the group exposed to high levels of the volatile organic compound metabolite, trans, trans-muconic acid and the polycyclic aromatic hydrocarbons metabolite, 2-hydroxynaphthalene, respectively, than in the low-level exposure groups for those metabolites. This study confirmed that environmental pollutants influenced the rate of change in the FSH/AMH ratio with age. Further studies on larger populations are necessary in the future.

Beyond Genes: Germline Disruption in the Etiology of Autism Spectrum Disorders

Investigations into the etiology of autism spectrum disorders have been largely confined to two realms: variations in DNA sequence and somatic developmental exposures. Here we suggest a third route-disruption of the germline epigenome induced by exogenous toxicants during a parent's gamete development. Similar to cases of germline mutation, these molecular perturbations may produce dysregulated transcription of brain-related genes during fetal and early development, resulting in abnormal neurobehavioral phenotypes in offspring. Many types of exposures may have these impacts, and here we discuss examples of anesthetic gases, tobacco components, synthetic steroids, and valproic acid. Alterations in parental germline could help explain some unsolved phenomena of autism, including increased prevalence, missing heritability, skewed sex ratio, and heterogeneity of neurobiology and behavior.

Bromoacetic acid impairs mouse oocyte in vitro maturation through affecting cytoskeleton architecture and epigenetic modification

As a major public health achievement, disinfection of drinking water significantly decreases outbreaks of waterborne disease, but produces drinking water disinfection by-products (DBPs) unfortunately. The haloacetic acids (HAAs) including bromoacetic acid (BAA), the second major class of DBPs, are considered as a global public health concern. BAA has been identified as cytotoxic, genotoxic, mutagenic, carcinogenic, and teratogenic in somatic cells. However, the toxic effects of BAA on oocyte maturation remain obscure. Herein, we documented that exposure to BAA compromised mouse oocyte maturation in vitro, causing blocked polar body extrusion (PBE). Meiotic progression analysis demonstrated that exposure to BAA induced the activated spindle assembly checkpoint (SAC) mediated metaphase I (MI) arrest in oocytes. Further study revealed that exposure to BAA resulted in the hyperacetylation of α-tubulin, disrupting spindle assembly and chromosome alignment, which is responsible for the activation of SAC. Besides, the organization of actin, the other major component of cytoskeleton in oocytes, was disturbed after BAA exposure. In addition, exposure to BAA altered the status of histone H3 methylation and 5 mC, indicative of the damaged epigenetic modifications. Moreover, we found that exposure to BAA induced DNA damage in a dose-dependent manner in oocytes. Collectively, our study evidenced that exposure to BAA intervened mouse oocyte maturation via disrupting cytoskeletal dynamics, damaging epigenetic modifications and inducing accumulation of DNA damage.

A New Understanding, Guided by Single-Cell Sequencing, of the Establishment and Maintenance of the Ovarian Reserve in Mammals

BACKGROUND

Oocytes are a finite and non-renewable resource that are maintained in primordial follicle structures. The ovarian reserve is the totality of primordial follicles, present from birth, within the ovary and its establishment, size, and maintenance dictates the duration of the female reproductive lifespan. Understanding the cellular and molecular dynamics relevant to the establishment and maintenance of the reserve provides the first steps necessary for modulating both individual human and animal reproductive health as well as population dynamics.

SUMMARY

This review details the key stages of establishment and maintenance of the ovarian reserve, encompassing germ cell nest formation, germ cell nest breakdown, and primordial follicle formation and activation. Furthermore, we spotlight several formative single-cell sequencing studies that have significantly advanced our knowledge of novel molecular regulators of the ovarian reserve, which may improve our ability to modulate female reproductive lifespans.

KEY MESSAGES

The application of single-cell sequencing to studies of ovarian development in mammals, especially when leveraging genetic and environmental models, offers significant insights into fertility and its regulation. Moreover, comparative studies looking at key stages in the development of the ovarian reserve across species has the potential to impact not just human fertility, but also conservation biology, invasive species management, and agriculture.

Endocrine disrupting chemicals impact on ovarian aging: Evidence from epidemiological and experimental evidence

Endocrine-disrupting chemicals (EDCs) are ubiquitous in daily life, but their harmful effects on the human body have not been fully explored. Recent studies have shown that EDCs exposure could lead to infertility, menstrual disorder and menopause, resulting in subsequent effects on female health. Therefore, it is of great significance to clarify and summarize the impacts of EDCs on ovarian aging for explaining the etiology of ovarian aging and maintaining female reproductive health. Here in this review, we focused on the impacts of ten typical environmental contaminants on the progression of ovarian aging during adult exposure, including epidemiological data in humans and experimental models in rodents, with their clinical phenotypes and underlying mechanisms. We found that both persistent (polychlorinated biphenyls, perfluoroalkyl and polyfluoroalkyl substances) and non-persistent (phthalates) EDCs exposure could increase an overall risk of ovarian aging, leading to the diminish of ovarian reserve, decline of fertility or fecundity, irregularity of the menstrual cycle and an earlier age at menopause, and/or premature ovarian insufficiency/failure in epidemiological studies. Among these, the loss of follicles can also be validated in experimental studies of some EDCs, such as BPA, phthalates, parabens and PCBs. The underlying mechanisms may involve the impaired ovarian follicular development by altering receptor-mediated pro-apoptotic pathways, inducing signal transduction and cell cycle arrest and epigenetic modification. However, there were inconsistent results in the impacts on fertility/fecundity, menstrual/estrous cycle and hormone changes response to different EDCs, and differences between human and animal studies. Our review summarizes the current state of knowledge on ovarian disrupters, highlights their risks to ovarian aging and identifies knowledge gaps in humans and animals. We therefore propose that females adopt healthy lifestyle changes to minimize their exposure to both persistent and non-persistent chemicals, that have the potential damage to their reproductive function.

Phthalate monoesters act through peroxisome proliferator-activated receptors in the mouse ovary

Widespread use of phthalates as solvents and plasticizers leads to everyday human exposure. The mechanisms by which phthalate metabolites act as ovarian toxicants are not fully understood. Thus, this study tested the hypothesis that the phthalate metabolites monononyl phthalate (MNP), monoisononyl phthalate (MiNP), mono(2-ethylhexyl) phthalate (MEHP), monobenzyl phthalate (MBzP), monobutyl phthalate (MBP), monoisobutyl phthalate (MiBP), and monoethyl phthalate (MEP) act through peroxisome proliferator-activated receptors (PPARs) in mouse granulosa cells. Primary granulosa cells were isolated from CD-1 mice and cultured with vehicle control (dimethyl sulfoxide) or MNP, MiNP, MEHP, MBzP, MBP, MiBP, or MEP (0.4-400 μM) for 24 h. Following culture, qPCR was performed for known PPAR targets, Fabp4 and Cd36. Treatment with the phthalate metabolites led to significant changes in Fabp4 and Cd36 expression relative to control in dose-dependent or nonmonotonic fashion. Primary granulosa cell cultures were also transfected with a DNA plasmid containing luciferase expressed under the control of a consensus PPAR response element. MNP, MiNP, MEHP, and MBzP caused dose-dependent changes in expression of luciferase, indicating the presence of functional endogenous PPAR receptors in the granulosa cells that respond to phthalate metabolites. The effects of phthalate metabolites on PPAR target genes were inhibited in most of the cultures by co-treatment with the PPAR-γ inhibitor, T0070907, or with the PPAR-α inhibitor, GW6471. Collectively, these data suggest that some phthalate metabolites may act through endogenous PPAR nuclear receptors in the ovary and that the differing structures of the phthalates result in different levels of activity.

Case Report: A Novel Homozygous Frameshift Mutation of the SKIV2L Gene in a Trichohepatoenteric Syndrome Patient Presenting With Short Stature, Premature Ovarian Failure, and Osteoporosis

Background: Trichohepatoenteric syndrome (THES) is a rare Mendelian autosomal recessive genetic disease characterized by intractable diarrhea, woolly hair, facial abnormality, immune dysfunction, and intrauterine growth restriction. THES mutations are found in the TTC37 and SKIV2L genes, which encode two components of the human superkiller (SKI) complex.

Methods and results: We report one case of a 32-year-old woman of Chinese descent with THES, who was born with a low weight (2000 g). She had intractable diarrhea during the neonatal period and was allergic to cow’s milk and condensed milk, but did not require total parenteral nutrition. She experienced menarche at age 12 and amenorrhea at age 28. In May 2019, the patient presented with a left fibular head fracture and was diagnosed with osteoporosis. Genetic testing showed a novel mutation in exon1 [p.E5Afs∗37 (c.12_13del)] of SKIV2L, which is composed of 28 exons. After the diagnosis, hormone replacement therapy was prescribed, in addition to the routine calcium and vitamin D supplements.

Conclusion: This case expands the clinical characteristic and phenotype spectrum of THES, providing further understanding of SKIV2L and its autoimmune influence.

Zinc pyrithione exposure compromises oocyte maturation through involving in spindle assembly and zinc accumulation

Zinc Pyrithione (ZPT), a Food and Drug Administration (FDA) approved chemical, is widely used for topical antimicrobials and cosmetic consumer products, including anti-dandruff shampoos. ZPT and its degraded byproducts have detected in large quantities in the environment, and identified to pose healthy risks on aquatic organisms and human. However, so far, knowledge about ZPT effects on female reproduction, particularly oocyte maturation and quality, is limited. Herein, we investigated the adverse impact of ZPT on mouse oocyte maturation and quality in vitro and found exposure to ZPT significantly compromises oocyte maturation. The results revealed that ZPT disturbed the meiotic cell cycle by impairing cytoskeletal dynamics, kinetochore-microtubule attachment (K-MT), and causing spindle assembly checkpoints (SAC) continuous activation. Further, we observed the microtubule-organizing centers (MTOCs) associated proteins p-MAPK and Aurora-A were disrupted in ZPT-treated oocytes, signified by decreased expression and abnormal localization, responsible for the severe cytoskeletal defects. In addition, ZPT exposure induced a significant increase in the levels of H3K9me2, H3K9me3, H3K27me1, and H3K27me3, suggesting the alterations of epigenetic modifications. Moreover, the accumulation of zinc ions (Zn2+) was observed in ZPT-treated oocytes, which was detrimental because overmuch intracellular Zn2+ disrupted oocyte meiosis. Finally, these above alterations impaired spindle organization and chromosome alignment in metaphase-II (MII) oocytes, indicative of damaged oocytes quality. In conclusion, ZPT exposure influenced oocyte maturation and quality via involvement in MTOCs-associated proteins mediated spindle defects, altered epigenetic modifications and zinc accumulation.

Effect of ambient air pollutants on in vitro fertilization-embryo transfer pregnancy outcome in Zhengzhou, China

With the acceleration of China's urbanization and industrialization, air pollution has become a major environmental problem. Retrospective data analysis of 6564 patients who underwent IVF-ET in the center for reproductive medicine of the First Affiliated Hospital of Zhengzhou University from 2015 to 2020. Different stages were selected from 90 days before oocyte retrieval to 35 days after transfer and divided into five exposure periods. Multivariate logistic regression was used to analyze the relationship between six ambient air pollutants (PM_2.5, PM₁₀, NO₂, SO₂, CO and O₃) and the IVF-ET pregnancy outcome. The results showed that air pollutants can significantly affect the IVF pregnancy outcome. The harmful effects of ambient air pollutants are more obvious in the patients aged < 35 years, single embryo transfer and cleavage stage embryo transfer.

Role of autophagy in follicular development and maintenance of primordial follicular pool in the ovary

The reproductive life span of the organism mainly depends on follicular development that maintains the primordial follicle pool in the cohort of follicles within the ovary. The total count of primordial follicles decreases with age due to ovulation and follicular atresia. Follicular atresia, a process of ovarian follicles degradation, mainly occurs via apoptosis, but recent studies also favor autophagy existence. Autophagy is a cellular and energy homeostatic response that helps to maintain the number of healthy primordial follicles, germ cell survival, and removal of corpus luteum remnants. But the excessive autophagic cell death changes both the quality and quantity of oocytes that ultimately affect female reproductive health. Autophagy regulation occurs by various autophagy-regulated genes like BECN1 and LC3-II (autophagy marker genes). Their abnormal regulation or mutation highly influences follicular development by alteration of primordial follicles formation, the decline in oocytes count, and germ cell loss. Various classical signaling pathways such as PI3K/AKT/mTOR, MAPK/ERK1/2, AMPK, and IRE1 are involved in granulosa and oocytes autophagy, while mTOR signaling is the primary mechanism. Along with basal level autophagy, chemical/hormone/stress-mediated autophagy also affects follicular development and female reproduction. In this review, we have primarily focused on granulosa cell and oocytes' autophagy, mechanism, and the role of autophagy determining marker genes in follicular development.

Gossypol exposure induces mitochondrial dysfunction and oxidative stress during mouse oocyte in vitro maturation

Gossypol is a yellow natural polyphenolic compound extracted from the seeds, leaves, stems, and flower buds of the cotton plant. Several studies have shown that exposure to gossypol impacts reproductive health in both humans and animals. However, whether gossypol exposure would influence oocyte quality has not yet been determined. Here, we studied the effects of gossypol on the meiotic maturation of mouse oocytes in vitro. The results revealed that gossypol exposure did not affect germinal vesicle breakdown (GVBD) but significantly reduced polar body extrusion (PBE) rates. Moreover, we observed meiotic spindle organization and chromosome alignment were entirely disturbed after gossypol exposure. Further, gossypol exposure also caused mitochondrial dysfunction and abruptly decreased the levels of cellular ATP, and diminished the mitochondrial membrane potential (MMP). Accordingly, gossypol-induced oxidative stress was confirmed through an increased level of reactive oxygen species (ROS). Early apoptosis incidence also increased as identified by positive Annexin-V signaling. Collectively, the above findings provide evidence that gossypol exposure impaired oocyte meiotic maturation, disturbed spindle structure and chromosome dynamics, disrupted mitochondrial function, induced oxidative stress, and triggered early apoptosis. These findings emphasize gossypol's adverse effects on oocyte maturation and thus on female fertility.

Protective Mechanism of Luteinizing Hormone and Follicle-Stimulating Hormone Against Nicotine-Induced Damage of Mouse Early Folliculogenesis

Previous studies have shown that nicotine could impair the germ cell cyst breakdown and the primordial follicle assembly by autophagy. In this paper, we discovered that luteinizing hormone (LH) and follicle-stimulating hormone (FSH) could counteract the damage caused by nicotine of mouse germ cell cyst breakdown. The neonatal mice were separately intraperitoneally injected with nicotine, nicotine plus LH, nicotine plus FSH, and saline (control) for 4 days. Compared with the nicotine group, the quality of oocytes and the number of follicles were remarkably increased in the nicotine plus LH group or nicotine plus FSH group. LH and FSH could alleviate nicotine-induced oocyte autophagy by different pathways. LH reduced the nicotine-induced autophagy by restoring the phosphorylation level of adenosine 5′-monophosphate-activated protein kinase α-1, while FSH by downregulating the phosphorylation level of Forkhead box class O 1. In addition, in a subsequent study of 6-week mice in different treated groups, we found that LH and FSH supplementation significantly improved normal maturation rates, fertilization rates, and embryo’s developmental potential of oocytes in oocytes exposed to nicotine. Taken together, these results suggested that LH and FSH could counteract the damage caused by nicotine and finally ensure normal germ cell cyst breakdown and early embryo development.

Maternal Zearalenone exposure impacted ovarian follicle formation and development of suckled offspring

Zearalenone (ZEN) is a secondary metabolite, which is mainly produced by Fusarium fungi and exists in various feeds and agricultural products. Recently, an increasing amount of data has shown that ZEN, as an estrogen-like hormone, can have harmful effects on the female reproductive system, especially on oogenesis and folliculogenesis. Breast milk is considered to be the ideal form of nutrition for infants; however, there are some records of contaminants in food, such as mycotoxins, which may be transferred from maternal blood to milk. In this study, we investigated the toxic effects of breast milk on folliculogenesis in offspring following maternal ZEN exposure. Our results showed that maternal ZEN exposure significantly inhibited the process of primordial follicle (PF) assembly and reduced the number of PFs in suckled offspring's ovaries. In addition, RNA-seq analysis showed that RIG-I-like receptor (RLRs) signaling pathways were activated after exposed to ZEN, which increased the expression levels of DNA damage (γ-H2AX, RAD51, and PARP1) and apoptosis related protein (BAX/BCL2 and Caspase-3). Finally, ZEN exposure interfered with follicular development, as evidenced by the reduced percentages of oocyte maturation and embryonic development when the offspring grew to adolescence. It is worth noting that maternal ZEN exposure disrupted the tri-methylation levels of H3K4, H3K9, and H3K27 in the offspring's oocytes. Our results indicated that maternal ZEN exposure affected ovarian development in offspring through the breast milk, which may be detrimental to their reproductive capability in adult life.

Inflammatory cytokines as key players of apoptosis induced by environmental estrogens in the ovary

Natural and synthetic environmental estrogens (EEs), interfering with the physiological functions of the body's estrogens, are widespread and are rising much concern for their possible deleterious effects on human and animal health, in particular on reproduction. In fact, increasing evidence indicate that EEs can be responsible for a variety of disfunctions of the reproductive system especially in females such as premature ovarian insufficiency (POI). Because of their great structural diversity, the modes of action of EEs are controversial. One important way through which EEs exert their effects on reproduction is the induction of apoptosis in the ovary. In general, EEs can exert pro-and anti-apoptotic effects by agonizing or antagonizing numerous estrogen-dependent signaling pathways. In the present work, results concerning apoptotic pathways and diseases induced by representative EEs (such as zearalenone, bisphenol A and di-2-ethylhexyl phthalate), in ovaries throughout development are presented into an integrated network. By reviewing and elaborating these studies, we propose inflammatory factors, centered on the production of tumor necrosis factor (TNF), as a major cause of the induction of apoptosis by EEs in the mammalian ovary. As a consequence, potential strategies to prevent such EE effect are suggested.

The effect of prophylactic bilateral salpingectomy on ovarian reserve in patients who underwent laparoscopic hysterectomy

BACKGROUND

Bilateral salpingectomy has been proposed to reduce the risk of ovarian cancer, but it is not clear whether the surgery affects ovarian reserve. This study compares the impact of laparoscopic hysterectomy for benign disease with or without prophylactic bilateral salpingectomy on ovarian reserve.

METHODS

Records were reviewed for 373 premenopausal women who underwent laparoscopic hysterectomy with ovarian reserve for benign uterine diseases. The serum anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and three-dimensional antral follicle count (AFC) were assessed before surgery and 3 and 9 months postoperatively to evaluate ovarian reserve. Patients were divided into two groups according to whether they underwent prophylactic bilateral salpingectomy. The incidence of pelvic diseases was monitored until the ninth month after surgery.

RESULTS

There was no significant difference between the two surgery groups in terms of baseline AMH, E2, FSH, LH, and AFC (all P > 0.05). There was no difference in potential bias factors, including patient age, operative time, and blood loss (all P > 0.05). There was also no significant difference between the two groups 3 months after surgery with respect to AMH (P = 0.763), E2 (P = 0.264), FSH (P = 0.478), LH (P = 0.07), and AFC (P = 0.061). Similarly, there were no differences between groups 9 months after surgery for AMH (P = 0.939), E2 (P = 0.137), FSH (P = 0.276), LH (P = 0.07) and AFC (P = 0.066). At 9 months after the operation, no patients had malignant ovarian tumors. The incidences of benign ovarian tumors in the salpingectomy group were 0 and 2.68 % at 3 and 9 months after surgery, respectively, and the corresponding values in the control group were 0 and 5.36 %. The incidences of pelvic inflammatory disease in the salpingectomy group were 10.72 and 8.04 % at 3 and 9 months after surgery, respectively, while corresponding values in the control group were 24.13 and 16.09 %.

CONCLUSIONS

Prophylactic bilateral salpingectomy did not damage the ovarian reserve of reproductive-age women who underwent laparoscopic hysterectomy. Prophylactic bilateral salpingectomy might be a good method to prevent the development of ovarian cancer. Larger clinical trials with longer follow-up times are needed to further evaluate the risks and benefits.

Perinatal hypoxia leads to primordial follicle activation and premature depletion of ovarian reserve

BACKGROUND

The human ovary contains 6-million follicles during the 20th week of embryonic development and 1 million at birth. Girls born at small for gestational age weight demonstrate higher FSH levels during infancy, an earlier onset of puberty, and menarche. In light of these observations, we hypothesized that exposure to hypoxia at the early neonatal period might impact the primordial follicular pool and lead to premature depletion of ovarian reserve.

METHODS

Ovarian development in the rat model at days 1-5 postpartum reflects its human counterpart in the late perinatal period. We exposed newborn rat pups (n = 5) to controlled hypoxia, (5% oxygen/95% nitrogen) for 10 min three times daily for days 1-5 postpartum. On day 5, ovaries were harvested, H&E, Ki-67, and TUNEL staining were performed.

RESULTS

The percentage of primordial follicles out of total follicles in ovaries of pups exposed to hypoxia was lower compared to control (76 ± 8.2% and 90.33 ± 6.3% respectively, p < .05). Correspondingly the percentage of primary and secondary follicles was higher than in control. The mean stromal Ki67 staining score was significantly lower in the study group (1.67 ± 0.58 and 2.5 ± 0.55 respectively, p < .05). TUNEL staining demonstrated no difference in stromal apoptosis rates between both groups.

CONCLUSIONS

We provide evidence for the first time that perinatal hypoxia causes premature activation and growth initiation of dormant follicles. These changes were associated with decreased stromal cell proliferation, suggesting hypoxia-induced impairment of the support cell pool as a possible mechanism for accelerated follicular activation.

Perinatal exposure to a human relevant mixture of persistent organic pollutants: Effects on mammary gland development, ovarian folliculogenesis and liver in CD-1 mice

The ability of persistent organic pollutants (POPs) with endocrine disrupting properties to interfere with the developing reproductive system is of increasing concern. POPs are transferred from dams to offspring and the high sensitivity of neonates to endocrine disturbances may be caused by underdeveloped systems of metabolism and excretion. The present study aimed to characterize the effect of in utero and lactational exposure to a human relevant mixture of POPs on the female mammary gland, ovarian folliculogenesis and liver function in CD-1 offspring mice. Dams were exposed to the mixture through the diet at Control, Low or High doses (representing 0x, 5000x and 100 000x human estimated daily intake levels, respectively) from weaning and throughout mating, gestation, and lactation. Perinatally exposed female offspring exhibited altered mammary gland development and a suppressed ovarian follicle maturation. Increased hepatic cytochrome P450 enzymatic activities indirectly indicated activation of nuclear receptors and potential generation of reactive products. Hepatocellular hypertrophy was observed from weaning until 30 weeks of age and could potentially lead to hepatotoxicity. Further studies should investigate the effects of human relevant mixtures of POPs on several hormones combined with female reproductive ability and liver function.

How Family Histories Can Inform Research About Germ Cell Exposures: The Example of Autism

Throughout the scientific literature, heritable traits are routinely presumed to be genetic in origin. However, as emerging evidence from the realms of genetic toxicology and epigenomics demonstrate, heritability may be better understood as encompassing not only DNA sequence passed down through generations, but also disruptions to the parental germ cells causing de novo mutations or epigenetic alterations, with subsequent shifts in gene expression and functions in offspring. The Beyond Genes conference highlighted advances in understanding these aspects at molecular, experimental and epidemiological levels. In this commentary I suggest that future research on this topic could be inspired by collecting parents' germ cell exposure histories, with particular attention to cases of families with multiple children suffering idiopathic disorders. In so doing I focus on the endpoint of autism spectrum disorders (ASD). Rates of this serious neurodevelopment disability have climbed around the world, a growing crisis that cannot be explained by diagnostic shifts. ASD's strong heritability has prompted a research program largely focused on DNA sequencing to locate rare and common variants, but decades of this gene-focused research have revealed surprisingly little about the molecular origins of the disorder. Based on my experience as the mother of two children with idiopathic autism, and as a research philanthropist and autism advocate, I suggest ways researchers might probe parental germ cell exposure histories to develop new hypotheses that may ultimately reveal sources of non-genetic heritability in a subset of idiopathic heritable pathologies.

Effect of Jiajian Guishen Formula on the senescence-associated heterochromatic foci in mouse ovaria after induction of premature ovarian aging by the endocrine-disrupting agent 4-vinylcyclohexene diepoxide

ETHNOPHARMACOLOGICAL RELEVANCE

Jiajian Guishen Formula (JJGSF), which is a prescription of Traditional Chinese Medicine (TCM), has been reported to be useful in the treatment of premature ovarian insufficiency (POI).

AIM OF THE STUDY

To investigate the therapeutic effects of JJGSF on the treatment of POI induced by 4-vinylcyclohexene diep-oxide (VCD), an endocrine-disrupting chemical (EDC), and to elucidate the potential mechanism.

MATERIALS AND METHODS

Female 8-week-old ICR mice (N = 72) were randomized into six groups, containing the Model group, Control group, three JJGSF groups, and Progynova group which was served as a positive control. After model establishment by VCD, the Progynova group were given a daily intragastric administration of Progynova, and the three JJGSF groups (high dose group, medium dose group and low dose group) received a daily intragastric administration of JJGSF at doses of 9, 4.5 and 2.25 g/kg for four weeks. The general growth of the mice was observed and the estrous cycles were examined. The serum hormone concentrations were measured by enzyme-linked immunosorbent assay (ELISA). To explore the potential mechanism of effect, the protein expressions of H3K9me3, HP1, and HMGA1/HMGA2 related to senescence-associated heterochromatic foci (SAHF), were determined by Immunofluorescence and Western blot analysis, respectively.

RESULTS

After treating with JJGSF, the estrous cycles were improved significantly. The level of estrogen (E2) and anti-müllerian hormone (AMH) was increased and the ratio of follicle-stimulating hormone (FSH) to luteinizing hormone (LH) in serum was decreased significantly. Furthermore, a significant down-regulation of HMGA1/HMGA2 on protein level, a reduction distribution of HP1 and H3K9me3 in ovarian, and a lower fraction of SAHF-positive cells were observed after the administration with JJGSF, additionally effects showed a positive correlation with dosages.

CONCLUSIONS

JJGSF could treat POI by the mechanism of inhibiting SAHF.

Experimental study for the establishment of a chemotherapy-induced ovarian insufficiency model in rats by using cyclophosphamide combined with busulfan

With an improvement in the survival rate of cancer patients, chemotherapy-induced premature ovarian insufficiency (POI) is increasingly affecting the quality of life of female patients. Currently, there are many relevant studies using mice as an animal model. However, a large coefficient of variation for weight in mice is not appropriate for endocrine-related studies, compared with rats; therefore, it is necessary to identify an appropriate experimental model in rats. In this study, cyclophosphamide combined with busulfan was used to establish an animal model. We compared several common modeling methods using chemotherapeutic drugs, cisplatin, cyclophosphamide, and 4-vinylcyclohexene diepoxide (VCD), and we found that the combination of cyclophosphamide and busulfan was more effective in establishing a POI model in rats with few side effects by analyzing general physical conditions, pathological tissue sections of heart, liver, lung, spleen, kidney, uterus, and ovary, serum hormone levels, and follicle counts; thus, providing a more reliable model basis for subsequent studies.

Single-cell transcriptome dissection of the toxic impact of Di (2-ethylhexyl) phthalate on primordial follicle assembly

Rationale: Accumulated evidence indicates that environmental plasticizers are a threat to human and animal fertility. Di (2-ethylhexyl) phthalate (DEHP), a plasticizer to which humans are exposed daily, can trigger reproductive toxicity by acting as an endocrine-disrupting chemical. In mammals, the female primordial follicle pool forms the lifetime available ovarian reserve, which does not undergo regeneration once it is established during the fetal and neonatal period. It is therefore critical to examine the toxicity of DEHP regarding the establishment of the ovarian reserve as it has not been well investigated. Methods: The ovarian cells of postnatal pups, following maternal DEHP exposure, were prepared for single cell-RNA sequencing, and the effects of DEHP on primordial follicle formation were revealed using gene differential expression analysis and single-cell developmental trajectory. In addition, further biochemical experiments, including immunohistochemical staining, apoptosis detection, and Western blotting, were performed to verify the dataset results. Results: Using single-cell RNA sequencing, we revealed the gene expression dynamics of female germ cells and granulosa cells following exposure to DEHP in mice. Regarding germ cells: DEHP impeded the progression of follicle assembly and interfered with their developmental status, while key genes such as Lhx8, Figla, and others, strongly evidenced the reduction. As for granulosa cells: DEHP likely inhibited their proliferative activity, and activated the regulation of cell death. Furthermore, the interaction between ovarian cells mediated by transforming growth factor-beta signaling, was disrupted by DEHP exposure, since the expression of GDF9, BMPR1A, and SMAD3 was affected. In addition, DNA damage and apoptosis were elevated in germ cells and/or somatic cells. Conclusion: These findings offer substantial novel insights into the reproductive toxicity of DEHP exposure during murine germ cell cyst breakdown and primordial follicle formation. These results may enhance the understanding of DEHP exposure on reproductive health.

Single-cell transcriptomic profiling provides insights into the toxic effects of Zearalenone exposure on primordial follicle assembly

Rationale: Zearalenone (ZEN), a pollutant in our daily diet, seriously threatens the reproductive health of humans and animals. The primordial follicle (PF) assembly in the mouse occurs during the perinatal period, which determines the whole ovarian reserve in reproductive lifespan. In the current investigation, we administered ZEN orally to perinatal mice from 16.5 days post coitum (dpc) to postnatal day 3 (PD3), and single-cell RNA sequencing (scRNA-seq) was performed on PD0 and PD3 ovarian tissues in the offspring to check ZEN toxic to primordial follicle formation at the single cell level. Methods: Ovarian tissues (in vivo) were examined by single cell RNA sequencing analysis, Immunostaining, and Western blotting. Ovarian tissues (in vitro) were examined by qRT-PCR, Immunostaining, and Western blotting. Results: We found that ZEN exposure altered the developmental trajectory of both germ cells and granulosa cells. Furthermore, after establishing the cell-cell communication network between germ cells and granulosa cells, we found that this was perturbed by ZEN exposure, especially during the Hippo signaling pathway. Conclusions: This study showed that ZEN affected the status of germ cells and granulosa cells through the Hippo signaling pathway and blocked the assembly of PFs. This research contributes to our deeper understanding of the mechanisms of toxicity in different cell types and the disruption of normal intercellular signaling by ZEN exposure.

Detrimental effect of Bisphenol S in mouse germ cell cyst breakdown and primordial follicle assembly

The female reproductive lifespan is largely determined by the size of primordial follicle pool, which is established in early life. Bisphenol S (BPS), frequently present in plastic products used in daily life, has been demonstrated as an exogenous estrogen-like endocrine disrupting chemical interfering with the endocrine and reproductive systems. However, the molecular mechanisms of its reproductive toxicity remain to be determined. In the present study, we focused on the effect of BPS on the early ovarian folliculogenesis of mice. Our in vivo experiments showed that the treatment with BPS at 2 and 10 μg/kg body weight/day for 3 days induced abnormal germ cell cyst breakdown and primordial follicle assembly in the mouse ovary, further affecting later ovarian differentiation and reducing oocyte quality. In addition, our in vitro study demonstrated that BPS could interact with estrogen receptors (ERs) to induce phosphorylation of JNKs, which is responsible for reducing oocyte adhesion in cysts. Meanwhile, BPS exposure up-regulated Notch signaling pathway to increase the proliferation of granulosa cells precursors. Our study provided new evidence for the adverse effects of BPS on female reproduction, especially after perinatal exposure, and elucidated how it works.

Effects of Environment and Lifestyle Factors on Anovulatory Disorder

Anovulatory disorder comprises around 30% of female infertility. The origin of ovulatory failure is rooted in pituitary FSH secretion. Any factor or process that disrupts the finely tuned interactions of hypothalamo-pituitary-ovarian axis can potentially lead to anovulation. The World Health Organization (WHO) has classified anovulatory disorders into three categories: hypothalamic-pituitary failure, hypothalamic-pituitary dysregulation, and ovarian failure. Due to industrial development, environmental pollution, and global warming, the human living environment has undergone tremendous changes. Industrial waste, noise, pesticides, fertilizers, and vehicular emission are visible pollutants responsible for environmental contamination and ill effects on health of all living systems. A considerable body of research suggests that chemical exposures in the environment or workplace may be associated with endocrine disruption of the synthesis, secretion, transport, binding, or elimination of natural hormones. For instance, some advanced biological mechanisms suggest that heavy metals may affect progesterone production, which possibly disturbs endocrine function in pregnant women. On the other hand, our lifestyle factors have also changed accordingly, which greatly influence overall health and well-being, including fertility. Many lifestyle factors such as nutrition, weight, exercise, and psychological stress can have substantial effects on female ovulation.

Effects of Environmental Endocrine-Disrupting Chemicals on Female Reproductive Health

Environmental endocrine-disrupting chemicals (EDCs) are xenobiotic compounds that are frequently contacted in daily life. With the species and quantity of substances created and utilized by human beings significantly surpassing the self-purification capacity of nature, a large number of hazardous substances are enriched in the human body through the respiratory tract, digestive tract, and skin. Some of these compounds cause many problems endangering female reproductive health by simulating/antagonizing endogenous hormones or affecting the synthesis, metabolism, and bioavailability of endogenous hormones, including reproductive disorders, fetal birth defects, fetal developmental abnormalities, endocrine and metabolic disorders, and even gynecological malignancies. Therefore, the study of the relationship between environmental EDCs and female reproductive diseases and related mechanisms is of considerable significance to women, children health care, and improve the quality of the population.

Effects of Environment and Lifestyle Factors on Premature Ovarian Failure

Premature ovarian insufficiency (POI) or primary ovarian failure is defined as a cessation of the menstrual cycle in women younger than 40 years old. It is strictly defined as more than 4 months of oligomenorrhea or amenorrhea in a woman <40 years old, associated with at least two follicle-stimulating hormone (FSH) levels >25 U/L in the menopausal range, detected more than 4 weeks apart. It is estimated that POI was affected 1 and 2% of women. Although 80% of POI cases are of unknown etiology, it is suggested that genetic disorder, autoimmune origin, toxins, and environmental factors, as well as personal lifestyles, may be risk factors of developing POI. In this section, we will discuss the influences of environmental and lifestyle factors on POI. Moreover updated basic research findings regarding how these environmental factors affect female ovarian function via epigenetic regulations will also be discussed.

Germ cell nests in adult ovaries and an unusually large ovarian reserve in the naked mole-rat

The naked mole-rat (NMR, Heterocephalus glaber) is renowned for its eusociality and exceptionally long lifespan (> 30 y) relative to its small body size (35-40 g). A NMR phenomenon that has received far less attention is that females show no decline in fertility or fecundity into their third decade of life. The age of onset of reproductive decline in many mammalian species is closely associated with the number of germ cells remaining at the age of sexual maturity. We quantified ovarian reserve size in NMRs at the youngest age (6 months) when subordinate females can begin to ovulate after removal from the queen's suppression. We then compared the NMR ovarian reserve size to values for 19 other mammalian species that were previously reported. The NMR ovarian reserve at 6 months of age is exceptionally large at 108,588 ± 69,890 primordial follicles, which is more than 10-fold larger than in mammals of a comparable size. We also observed germ cell nests in ovaries from 6-month-old NMRs, which is highly unusual since breakdown of germ cell nests and the formation of primordial follicles is generally complete by early postnatal life in other mammals. Additionally, we found germ cell nests in young adult NMRs between 1.25 and 3.75 years of age, in both reproductively activated and suppressed females. The unusually large NMR ovarian reserve provides one mechanism to account for this species' protracted fertility. Whether germ cell nests in adult ovaries contribute to the NMR's long reproductive lifespan remains to be determined.

Bisphenol B Exposure Disrupts Mouse Oocyte Meiotic Maturation in vitro Through Affecting Spindle Assembly and Chromosome Alignment

Bisphenol B (BPB), a substitute of bisphenol A (BPA), is widely used in the polycarbonate plastic and resins production. However, BPB proved to be not a safe alternative to BPA, and as an endocrine disruptor, it can harm the health of humans and animals. In the present study, we explored the effects of BPB on mouse oocyte meiotic maturation in vitro. We found that 150 μM of BPB significantly compromised the first polar body extrusion (PBE) and disrupted the cell cycle progression with meiotic arrest. The spindle assembly and chromosome alignment were disordered after BPB exposure, which was further demonstrated by the aberrant localization of p-MAPK. Also, BPB exposure increased the acetylation levels of α-tubulin. As a result, the spindle assemble checkpoint (SAC) was continuously provoked, contributing to meiotic arrest. We further demonstrated that BPB severely induced DNA damage, but the ROS and ATP production were not altered. Furthermore, the epigenetic modifications were changed after BPB exposure, as indicated by increased K3K9me3 and H3K27me3 levels. Besides, the pattern of estrogen receptor α (ERα) dynamics was disrupted with a mass gathering on the spindle in BPB-exposed oocytes. Our collective results indicated that exposure to BPB compromised meiotic maturation and damaged oocyte quality by affecting spindle assembly and chromosome alignment, acetylation of α-tubulin, DNA damage, epigenetic modifications, and ERα dynamics in mouse oocytes.

Exogenous Oestrogen Impacts Cell Fate Decision in the Developing Gonads: A Potential Cause of Declining Human Reproductive Health

The increasing incidence of testicular dysgenesis syndrome-related conditions and overall decline in human fertility has been linked to the prevalence of oestrogenic endocrine disrupting chemicals (EDCs) in the environment. Ectopic activation of oestrogen signalling by EDCs in the gonad can impact testis and ovary function and development. Oestrogen is the critical driver of ovarian differentiation in non-mammalian vertebrates, and in its absence a testis will form. In contrast, oestrogen is not required for mammalian ovarian differentiation, but it is essential for its maintenance, illustrating it is necessary for reinforcing ovarian fate. Interestingly, exposure of the bi-potential gonad to exogenous oestrogen can cause XY sex reversal in marsupials and this is mediated by the cytoplasmic retention of the testis-determining factor SOX9 (sex-determining region Y box transcription factor 9). Oestrogen can similarly suppress SOX9 and activate ovarian genes in both humans and mice, demonstrating it plays an essential role in all mammals in mediating gonad somatic cell fate. Here, we review the molecular control of gonad differentiation and explore the mechanisms through which exogenous oestrogen can influence somatic cell fate to disrupt gonad development and function. Understanding these mechanisms is essential for defining the effects of oestrogenic EDCs on the developing gonads and ultimately their impacts on human reproductive health.

The peri-menopause in a woman's life: a systemic inflammatory phase that enables later neurodegenerative disease

The peri-menopause or menopausal transition—the time period that surrounds the final years of a woman’s reproductive life—is associated with profound reproductive and hormonal changes in a woman’s body and exponentially increases a woman’s risk of cerebral ischemia and Alzheimer’s disease. Although our understanding of the exact timeline or definition of peri-menopause is limited, it is clear that there are two stages to the peri-menopause. These are the early menopausal transition, where menstrual cycles are mostly regular, with relatively few interruptions, and the late transition, where amenorrhea becomes more prolonged and lasts for at least 60 days, up to the final menstrual period. Emerging evidence is showing that peri-menopause is pro-inflammatory and disrupts estrogen-regulated neurological systems. Estrogen is a master regulator that functions through a network of estrogen receptors subtypes alpha (ER-α) and beta (ER-β). Estrogen receptor-beta has been shown to regulate a key component of the innate immune response known as the inflammasome, and it also is involved in regulation of neuronal mitochondrial function. This review will present an overview of the menopausal transition as an inflammatory event, with associated systemic and central nervous system inflammation, plus regulation of the innate immune response by ER-β-mediated mechanisms.