The ovarian reserve of primordial follicles and the dynamic reserve of antral growing follicles: what is the link?

Genetic relationships between early menopause and the behaviour of theca interna during follicular atresia

Genetic variants are known to contribute to about 50% of the heritability of the age of menopause and recent studies suggest that genes associated with genome maintenance are involved. The idea that increased rates of follicular atresia could lead to depletion of the primoridial follicle reserve and early menopause has also been canvassed, but there is no direct evidence of this. In studies of the transcriptomics of follicular atresia, it was found that in the theca interna, the largest group of genes are in fact down-regulated and associated with 'cell cycle and DNA replication', in contrast with the up-regulation of apoptosis-associated genes which occurs in granulosa cells. Many of the genes down-regulated in the theca interna are the same as or related to the genes in loci associated with early menopause. From these findings, we suggest that early menopause could be due to increased rates of follicular atresia initiated from the theca interna.

Association between Anti-Müllerian Hormone Concentration and Inflammation Markers in Serum during the Peripartum Period in Dairy Cows

The relationships between changes in anti-Müllerian hormone (AMH) concentration and various traits, including milk somatic cell counts (SCC), were evaluated. Blood samples were collected from 43 Holstein cows 14 days before (D-14) and 10 (D10) and 28 days after (D28) parturition, and vaginal discharge score (VDS) and polymorphonuclear leukocyte (PMNL) percentages were assessed in endometrial samples at D28. Cows were separated into four quartiles (Q1-Q4) based on changes in AMH concentration during the peripartum period (AMH ratio: D28/D-14). Correlations between AMH ratio and each parameter were evaluated and classified into high-AMH (Q4, 1.83 ± 0.12, n = 11) and low-AMH (Q1, 0.83 ± 0.05, n = 11) groups. The AMH ratio was positively correlated with magnesium and non-esterified fatty acids levels, and the albumin/globulin ratio at D10 and D28, but negatively correlated with serum amyloid A (SAA) at D10. SAA and γ-globulin levels were significantly higher in the low-AMH group at D28. There was no significant difference in VDS, PMNL percentage, and milk SCC between the two groups. The decreasing AMH ratio from the prepartum to the postpartum period corresponds to high inflammation biomarker levels. Whether it subsequently affects the reproductive prognosis of postpartum cows needs further investigations.

Beneficial effects of a decreased meal frequency on nutrient utilization, secretion of luteinizing hormones and ovarian follicular development in gilts

Background

Replacement gilts are typically fed ad libitum, whereas emerging evidence from human and rodent studies has revealed that time-restricted access to food has health benefits. The objective of this study was to investigate the effect of meal frequency on the metabolic status and ovarian follicular development in gilts.

Methods

A total of 36 gilts (Landrace × Yorkshire) with an age of 150±3 d and a body weight of 77.6±3.8 kg were randomly allocated into one of three groups (n = 12 in each group), and based on the group allocation, the gilts were fed at a frequency of one meal (T1), two meals (T2), or six meals per day (T6) for 14 consecutive weeks. The effects of the meal frequency on growth preference, nutrient utilization, short-chain fatty acid production by gut microbial, the post-meal dynamics in the metabolic status, reproductive hormone secretions, and ovarian follicular development in the gilts were measured.

Results

The gilts in the T1 group presented a higher average daily gain (+ 48 g/d, P < 0.05) and a higher body weight (+ 4.9 kg, P < 0.05) than those in the T6 group. The meal frequency had no effect on the apparent digestibility of dry matter, crude protein, ether extract, ash, and gross energy, with the exception that the T1 gilts exhibited a greater NDF digestibility than the T6 gilts (P < 0.05). The nitrogen balance analysis revealed that the T1 gilts presented decreased urine excretion of nitrogen (− 8.17 g/d, P < 0.05) and higher nitrogen retention (+ 9.81 g/d, P < 0.05), and thus exhibited higher nitrogen utilization than the T6 gilts. The time-course dynamics of glucose, α-amino nitrogen, urea, lactate, and insulin levels in serum revealed that the T1 group exhibited higher utilization of nutrients after a meal than the T2 or T6 gilts. The T1 gilts also had a higher acetate content and SCFAs in feces than the T6 gilts (P < 0.05). The age, body weight and backfat thickness of the gilts at first estrous expression were not affected by the meal frequency, but the gilts in the T1 group had higher levels of serum luteinizing hormone on the 18th day of the 3rd estrus cycle and 17β-estradiol, a larger number of growing follicles and corpora lutea, and higher mRNA expression levels of genes related to follicular development on the 19th day of the 3rd estrus cycle.

Conclusions

The current findings revealed the benefits of a lower meal frequency equal feed intake on nutrient utilization and reproductive function in replacement gilts, and thus provide new insights into the nutritional strategy for replacement gilts, and the dietary pattern for other mammals, such as humans.

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.

Association between heat stress during intrauterine development and the calving-to-conception and calving-to-first-service intervals in Holstein cows

Heat stress has been widely studied in relation to its effects on the production and reproduction of dairy cattle. However, the long-term effects of heat stress during intrauterine development on adult cows have been scarcely considered. Thus, the aim of this study was to evaluate possible changes in the reproductive performance of Holstein cows gestated under different values of the Temperature-Humidity Index (THI) during their intrauterine development. Data collected from a database of reproductive and productive records of 10,790 Holstein cows from the central region of Argentina and the THI data from the agrometeorological station of the Instituto Nacional de Tecnología Agropecuaria (INTA) EEA Rafaela, Santa Fe, Argentina, were used. The gestation of the cows evaluated was divided into trimesters, in which the highest THI cycles (sum of three or more consecutive days of exposure to a THI ≥72 during each trimester) and number of days with a THI ≥ 72 were calculated. The calving-to-conception and calving-to-first-service intervals of the cows evaluated were considered as reproductive variables associated with their first lactation. Generalized Linear Mixed Models were used, considering the cow's dairy farm as a random factor within the model. The exposure of the animals to environments with a THI ≥72 during the first trimester of gestation had a negative impact on the reproductive efficiency parameters analyzed. The results obtained indicate that the exposure of pregnant females to high THI values has a long-term impact on their daughters, which may contribute to a decrease in their reproductive performance, possibly through inherited epigenetic characteristics that remain in later generations through fetal programming.

Perfluorooctanoic acid (PFOA) inhibits the gap junction intercellular communication and induces apoptosis in human ovarian granulosa cells

Perfluorooctanoic acid (PFOA) has attracted widespread research attention as it is very stable, bioaccumulates, and causes reproductive toxicity. Data from several animal experiments and epidemiological studies indicate that female fertility may decline because of ovarian granulosa cell (GC) apoptosis as oocyte quality is positively associated with effective gap junctional intercellular communication (GJIC) between GCs. To the best of our knowledge, however, no previous trials have been conducted or reported on the effects of PFOA exposure on apoptosis induction in human GCs. Moreover, the roles of GJIC in GC survival and in the induction of apoptosis in GCs by PFOA remain unclear. To test this, we cultured human GCs in vitro and treated them with 0 μM, 0.3 μM, 3 μM, or 30 μM PFOA for 24 h. We also treated a human ovarian GC line (KGN) with various combinations of PFOA, retinoic acid (RA, 10 μM), and carbenoxolone disodium (CBX, 50 mM). Our findings showed that PFOA lowered human GC viability and increased apoptosis. The effects of CBX resemble those of PFOA. The combination of PFOA and CBX enhances the inhibition of GJIC by PFOA and promotes apoptosis. The effects of RA are the opposite to those of PFOA. The combination of RA and PFOA mitigates PFOA-induced GJIC inhibition and reduces apoptosis. The observed expression levels of apoptosis-related proteins were consistent with the aforementioned findings. Hence, our study demonstrated that PFOA may induce human ovarian GC apoptosis by inhibiting GJIC.

Genetic evidence for Amh modulation of gonadotropin actions to control gonadal homeostasis and gametogenesis in zebrafish and its noncanonical signaling through Bmpr2a receptor

Anti-Müllerian hormone (Amh) plays an important role in gonadal function. Amh deficiency causes severe gonadal dysgenesis and dysfunction in zebrafish, with gonadal hypertrophy in both sexes. However, its mechanism of action remains unknown. Intriguingly, the Amh cognate type II receptor (Amhr2) is missing in the zebrafish genome, in sharp contrast to other species. Using a series of zebrafish mutants (amh, fshb, fshr and lhcgr), we provided unequivocal evidence for actions of Amh, via modulation of gonadotropin signaling, on both germ cell proliferation and differentiation. The gonadal hypertrophy in amh mutants was abolished in the absence of Fshr in females or Fshr/Lhcgr in males. Furthermore, we demonstrated that knockout of bmpr2a, but not bmpr2b, phenocopied all phenotypes of the amh mutant in both sexes, including gonadal hypertrophy, hyperproliferation of germ cells, retarded gametogenesis and reduced fshb expression. In summary, the present study provided comprehensive genetic evidence for an intimate interaction of gonadotropin and Amh pathways in gonadal homeostasis and gametogenesis and for Bmpr2a as the possible missing link for Amh signaling in zebrafish.

Comparison of methods for quantifying primordial follicles in the mouse ovary

Background

Accurate evaluation of primordial follicle numbers in mouse ovaries is an essential endpoint for studies investigating how endogenous and exogenous insults, such as maternal aging and chemotherapy, impact the ovarian reserve. In this study, we compared and contrasted two methods for counting healthy primordial follicles following exposure to cyclophosphamide (75 mg/kg), a well-established model of follicle depletion. The first was the fractionator/optical dissector technique, an unbiased, assumption-free stereological approach for quantification of primordial follicle numbers. While accurate, highly reproducible and sensitive, this method relies on specialist microscopy equipment and software, requires specific fixation, embedding and sectioning parameters to be followed, and is largely a manual process that is tedious and time-consuming. The second method was the more widely used serial section and direct count approach, which is relatively quick and easy. We also compared the impacts of different fixatives, embedding material and section thickness on the overall results for each method.

Results

Direct counts resulted in primordial follicle numbers that were significantly lower than those obtained by stereology, irrespective of fixation and embedding material. When applied to formalin fixed tissue, the direct count method did not detect differences in follicle numbers between saline and cyclophosphamide treated groups to the same degree of sensitivity as the gold standard stereology method (referred to as the Reference standard). However, when Bouin’s fixative was used, direct counts and stereology were comparable in their ability to detect follicle depletion caused by cyclophosphamide.

Conclusions

This work indicates that the direct count method can produce similar results to stereology when Bouin’s fixative is used instead of formalin. The findings presented here will assist others to select the most appropriate experimental approach for accurate follicle enumeration, depending on whether the primary objective of the study is to determine absolute primordial follicle numbers or relative differences between groups.

Transcriptomic profiles of the ovaries from piglets neonatally exposed to 4-tert-octylphenol

The environmental pollutants with hormonal activities may influence steroid-mediated processes in neonatal ovaries and increase the incidence of reproductive disorders. The aim of the current study was to examine effects of 4-tert-octylphenol (OP), a non-ionic surfactant widely used in a variety of industrial applications which has been reported to mimic the 17β-estradiol activity, on the expression of protein-coding (mRNAs) and long non-coding (lncRNAs) transcripts in neonatal ovaries of the pig. By employing RNA-Seq we aimed to gain insights into regulatory networks underlying the OP effects on the follicular development in pigs. Piglets were injected (sc) daily with OP (100 mg/kg bw) or corn oil (controls) between postnatal Days 1 and 10 (n = 3/group). Ovaries were excised from the 11-day-old piglets and total cellular RNA was isolated and sequenced. Two hundred three differentially expressed genes (DEGs; P-adjusted < 0.05 and log₂ fold change ≥1.0) and 23 differentially expressed lncRNAs (DELs; P-adjusted < 0.05 and log₂ fold change ≥ 1.0) were identified in OP-treated piglet ovaries. The DEGs were assigned to Gene Ontology terms, covering biological processes, molecular functions and cellular components, which linked the DEGs to functions associated with movement of cell or subcellular component, regulation of plasma membrane bounded cell projection assembly as well as hydrolase and endopeptidase activity. In addition, STRING analysis demonstrated the strongest interactions between genes related to negative regulation of endopeptidase activity. Some correlations between DEGs and DELs were also found, revealing that the OP action on the ovary may be partially executed via the changes in the lncRNA expression. These results suggest that neonatal exposure of pigs to OP induces changes in the ovarian transcriptomic profile associated with genes encoding serine protease inhibitors and involved in steroid synthesis as well as genes linked to intracellular and membrane transport. We suggest that the changes in the mRNA and lncRNA expression in the ovaries of OP-treated piglets may disturb ovarian cellular function, including steroidogenesis, proliferation and apoptosis.

Antral follicular count and its relationship with ovarian volume, preantral follicle population and survival, oocyte meiotic progression and ultrastructure of in vitro matured bovine cumulus-oocyte complexes

This study aimed to evaluate the relationship between antral follicular count (AFC) and ovarian volume (OV), preantral follicular population and survival, meiotic progression and ultrastructure of cumulus-oocyte complexes (COCs) after in vitro maturation. In experiment 1, the relationship between AFC and preantral follicle population and survival was evaluated by classical histology. In experiment 2, the relationship among AFC, OV, ability of oocytes to resume meiosis and ultrastructure of in vitro matured bovine COCs was studied. A positive correlation (P < 0.05) between AFC and the numbers of healthy primordial, degenerate and total follicles was observed, as well as with healthy secondary follicles and total follicles. The numbers of grades I and II oocytes in ovaries of high AFC class were higher compared with those with intermediate or lower AFC. After in vitro maturation, COCs from ovaries of high AFC had a higher percentage of oocytes in metaphase II compared with those of intermediate and low AFC (P < 0.0001). Ovaries of intermediate AFC had a higher percentage of oocytes in metaphase II compared with ovaries with low AFC (P < 0.0001). The proportion of oocytes in metaphase I, telophase I and anaphase I in COCs from ovaries of intermediate AFC (26.04%) was higher (P < 0.05) compared with that seen in COCs of ovaries with high (8.55%) and low (14.15%) AFC. No differences in the ultrastructure of oocytes were seen. In conclusion, after in vitro maturation, cow ovaries with high AFC have higher numbers of oocytes that reach in metaphase II (MII), but they also have higher numbers of degenerated primordial and primary follicles.

The CC-chemokine receptor 2 is involved in the control of ovarian folliculogenesis and fertility lifespan in mice

The chemokine receptor 2 (CCR2) was first described as a chemotactic factor involved in immune responses, but it also plays an essential function in several biological processes. The chemokine (C-C motif) ligand 2 (CCL2) binds to CCR2 triggering G protein-coupled receptor (GPCR) signaling in leukocytes, including activation of PI3K/Akt/mTOR, a key pathway that is also related to follicular activation and survival. However, the potential role of CCR2 in ovarian follicular physiology remain unexplored. Thus, we investigated the role of CCR2 on follicular growth during adult life and aging. Ovaries and oocytes were collected from wild type (WT) mice at 1.5 months old (mo), and CCR2 expression was observed predominantly in oocytes included in growing follicles, as well as after ovulation. Follicle populations were assessed in WT and CCR2-/- mice at 1.5 mo, and CCR2-/- mice had more primordial and less primary and secondary follicles, while there were no differences in antral follicle numbers. Pro-apoptotic genes Bax and Casp3 were downregulated, while anti-apoptotic Bcl2 was upregulated in CCR2-/- mice. To further characterize the role of CCR2 in ovarian aging, follicle populations were assessed in WT and CCR2-/- mice at 1.5, 2.5, 6, 10, and 12 mo. A larger ovarian follicular reserve at 1.5-6 mo was observed in CCR2-/- mice. Finally, CCR2-/- aged mice (6-12 mo) ovulated more oocytes than WT mice. Altogether, these data suggest that CCR2 plays an important role in the regulation of murine folliculogenesis, potentially affecting the reproductive lifespan.

The potential biological functions of circular RNAs during the initiation of atresia in pig follicles

The specific expression profile and function of circular RNAs (circRNAs) in mammalian ovarian follicles, especially during the atresia process, are unclear. In this study, genome-wide deep circRNA sequencing was applied to screen circRNAs in healthy and early atretic antral follicles in pig ovaries. A total of 40,567 distinct circRNAs were identified in follicles, among which 197 circRNAs (108 upregulated and 89 downregulated) were significantly shifted during the early atresia process. Most differentially expressed circRNAs (DECs) lacked protein-coding potential. Annotation analysis of the DECs revealed 162 known host genes, or noncoding RNAs, and 10 intergenic regions. The key pathways in which these host genes are involved include the focal adhesion-PI3K-Akt-mTOR signaling pathway, vascular endothelial growth factor A (VEGFA)-vascular endothelial growth factor receptor 2 signaling pathway and transforming growth factor-beta signaling pathway. Further comparison analysis between host genes of DECs and the differentially expressed linear messenger RNA transcripts revealed the cotranscription of circRNAs and their linear mRNAs in inhibin beta units (INHBA and INHBB), glutathione S-transferase (GSTA1), and VEGFA. In addition, we predicted 196 pairs of potential circRNA-micro RNA (miRNA) interactions among 77 DECs and 101 porcine miRNAs. We have identified 16 functional miRNAs by comparing the 101 miRNAs to the functional miRNAs reported in mammal ovarian follicle atresia and granulosa cell apoptosis studies. Our study adds new knowledge to circRNA distribution profiles in pig ovarian follicles, offers a valuable reference for transcriptomic profiles in the initiation of follicular atresia, highlights warranted circRNAs for further functional investigation, and provides possible biomarkers for ovarian dysfunctions.

Vitamin D3 action within the ovary - an updated review

Vitamin D3 is well-known as a major regulator of calcium and phosphorus homeostasis. A growing body of evidence highlights its crucial role in the regulation of reproductive processes in females. The role of vitamin D3 in the female reproductive tract has been extensively investigated because its receptor is abundant in reproductive organs, including ovary. Importantly, besides expression of vitamin D3 receptor, the ovary is an extrarenal site of vitamin D3 metabolism. The influence of vitamin D3 on follicular development and ovarian steroidogenesis has been investigated. Furthermore, vitamin D3 deficiency has also been associated with polycystic ovary syndrome, premature ovarian failure and ovarian cancer. The objective of this review is to summarize our knowledge about the contribution of vitamin D3 to physiological and pathological processes within the ovary.

Evaluation of relationship between HbA1c levels and ovarian reserve in patients with type 1 diabetes mellitus

In organ or non-organ-specific autoimmune disorders, human ovary is usually the target of the autoimmune attack. We aimed to demonstrate the correlation between ovarian reserve and DM1, based on the view that women with type-1 diabetes mellitus (DM1) will have lower AMH levels secondary to poor glycemic control and autoimmune attacks. Ovarian functions of 42 patients diagnosed with DM1 who use insulin and 65 healthy volunteers were analyzed. Basal hormone and AMH levels were measured during the follicular phase. Fasting and postprandial blood glucose concentrations, HbA1c and C-peptide levels were evaluated. The mean antral follicle count (AFC) was significantly lower in DM1 patients than in healthy controls (p = .001). The AMH levels were lower in women with DM1 than in the controls (p = .001). The HbA1c values of DM1 patients, who formed the study group, was significantly higher than the control group. Ovarian reserve that is evaluated with serum AMH level is affected by poor glycemic control in type 1 diabetes. Due to the time of the autoimmune damage in the ovaries and the observable effects of this damage, more comprehensive and longer-term studies are needed to be conducted for the follow-up of reproductive abnormalities.

Increased chemotherapy-induced ovarian reserve loss in women with germline BRCA mutations due to oocyte deoxyribonucleic acid double strand break repair deficiency

OBJECTIVE

To assess whether woman who have BRCA mutations (WBM) experience more declines in ovarian reserve after chemotherapy treatment, as it induces oocyte death by deoxyribonucleic acid (DNA) damage, and BRCA mutations result in DNA damage repair deficiency.

DESIGN

Longitudinal cohort study.

SETTING

Academic centers.

PATIENT(S)

The 108 evaluable women with breast cancer were stratified into those never tested (negative family history; n = 35) and those negative (n = 59) or positive (n = 14) for a pathogenic BRCA mutation.

INTERVENTION(S)

Sera were longitudinally obtained before and 12-24 months after chemotherapy treatment, assayed for antimüllerian hormone (AMH), and adjusted for age at sample collection.

MAIN OUTCOME MEASURE(S)

Ovarian recovery, defined as the geometric mean of the after chemotherapy age-adjusted AMH levels compared with baseline levels.

RESULT(S)

Compared with the controls, the before chemotherapy treatment AMH levels were 24% and 34% lower in those negative or positive for BRCA mutations, consistent with accelerated ovarian aging in WBM. The WBM had a threefold difference in AMH recovery after chemotherapy treatment (1.6%), when compared with BRCA negative (3.7%) and untested/low risk controls (5.2%). Limiting the analysis to the most common regimen, doxorubicin and cyclophosphamide followed by paclitaxel, showed similar results. These findings were mechanistically confirmed in an in vitro mouse oocyte BRCA knockdown bioassay, which showed that BRCA deficiency results in increased oocyte susceptibility to doxorubicin.

CONCLUSION(S)

Women who have pathogenic BRCA mutations are more likely to lose ovarian reserve after chemotherapy treatment, suggesting an emphasis on fertility preservation. Furthermore, our findings generate the hypothesis that DNA repair deficiency is a shared mechanism between aging, infertility, and cancer.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00823654.

Equine Aging and the Oocyte: A Potential Model for Reproductive Aging in Women

Numerous similarities in reproductive aging have been documented between the mare and woman. Aging is associated with a decline in fertility. In mares and women, oocyte transfer procedures were initially used to establish that oocyte donor age is associated with oocyte quality. Age-associated differences in oocytes include altered morphology, gene expression, and developmental potential. Reactive oxygen species and mitochondrial dysfunction are thought to be important contributors to loss of oocyte quality. In the woman, aneuploidy is a primary consideration with maternal aging. Although misalignment of chromosomes during meiosis has been observed in the mare, less is known in this area. Reproductive aging will be reviewed in the mare and compared with the woman with emphasis on factors that affect oocyte quality and developmental potential. Areas in which the mare could be used as a research model to study reproductive aging in women will be highlighted.

Gonad differentiation toward ovary

Gonad differentiation depends on a set of cellular and hormonal signals interacting in a specific order, with very precise windows of action, to contribute to the establishment of the genital tract and a male or female phenotype. Research initially focused on the stages of gonad differentiation toward testis, in particular following the identification in 1990 of the SRY factor on chromosome Y. The mechanisms involved in gonad differentiation toward ovary took longer to identify. Thanks to patients with different sexual development (DSD) and animal knock-out models, description of the cascades involved in the activation and maintenance of ovarian development has progressed considerably in recent years.

Fetal programming in dairy cows: Effect of heat stress on progeny fertility and associations with the hypothalamic-pituitary-adrenal axis functions

Ambient temperatures that result in body temperatures beyond those of the thermo-neutral zone for dairy cattle can lead to reduced reproductive efficiencies that have negative effects on economic and productive efficiencies of dairy farms. In addition, in pregnant cows, ambient temperature-induced heat stress leads to modifications in the epigenome of the developing embryo, which, in turn, could lead to phenotypic variations in the sexually mature animal and its offspring. In the mammalian response to stress, adrenocorticotropic hormone stimulates the synthesis and secretion of glucocorticoids, which may have detrimental effects on the hypothalamic-pituitary-gonadal axis and the female estrous cycle. The aim of this review is to describe the effects of ambient heat stress on the reproductive system of dairy cattle and its potential trans-generational effects. There are many heat stress occurrences in dairy cattle during a large portion of the year in many countries and there is an increase in incidence with the onset of global warming. These heat stress conditions make it possible that the embryo/fetus of cows may be affected when heat stress conditions prevail in ways that there is impaired fertility of the sexually mature cows that develop from these embryos/fetuses. This is the outcome because of molecular changes in ovarian glucocorticoid response caused by epigenetic modifications established during fetal development.

Bisphenol S Impaired Human Granulosa Cell Steroidogenesis in Vitro

Bisphenol S (BPS) is a structural analog of the endocrine disruptor bisphenol A (BPA); it is the main BPA replacement in the plastics industry. Previous studies have shown that BPA and BPS exhibit similar effects on reproduction in fish and rodent species. BPS reportedly alters steroidogenesis in bovine granulosa cells. Luteinised granulosa cells collected from 59 women who were undergoing an in vitro fertilization procedure were cultured for 48 h in the presence or absence of BPS (10 nM, 100 nM, 1 µM, 10 µM or 50 µM). BPS exposure was investigated by assessing follicular fluids from these 59 women for their BPS content. Culture medium, cells, total messenger RNA (mRNA) and total protein extracted from the luteinised granulosa cells were examined for oestradiol and progesterone secretion, cellular proliferation, viability, gene expression, steroidogenic enzyme expression and cell signaling. BPS was measured in follicular fluids using mass spectrometry. Exposure of granulosa cells to 10 or 50 µM BPS for 48 h induced a 16% (p = 0.0059) and 64% (p < 0.0001) decrease, respectively, in progesterone secretion; 50 µM BPS decreased oestradiol secretion by 46% (p < 0.0001). Ten µM BPS also tended to reduce CYP11A1 protein expression by 37% (p = 0.0947) without affecting HSD3B1 and CYP19A1 expression. Fifty µM BPS increased ERRγ expression. Environmental levels of BPS (nanomolar range) did not induce changes in steroidogenesis in human granulosa cells. The effects of BPS were observed after only 48 h of BPS exposure. These acute effects might be similar to chronic effects of physiological BPS levels.

Bisphenol S Impaired In Vitro Ovine Early Developmental Oocyte Competence

INTRODUCTION

Bisphenol A (BPA) is a widespread compound in the plastic industry that is especially used to produce baby bottles, food packaging and metal cans. BPA, an endocrine disruptor, leads to alterations in reproductive function and therefore has been banned from the food industry. Unregulated BPA analogues, particularly Bisphenol S (BPS), have emerged and are now used in the plastic industry. Thus, this study aimed to examine the acute effects of low and environmental doses of BPS on ewe oocyte quality and developmental competence, and its mechanism of action, during in vitro maturation.

METHODS

Ewe cumulus-oocyte complexes underwent in vitro maturation in the presence or absence of BPS (1 nM, 10 nM, 100 nM, 1 µM or 10 µM). Oocytes were then subjected to in vitro fertilisation and development.

RESULTS

1 µM BPS induced a 12.7% decrease in the cleavage rate (p = 0.004) and a 42.6% decrease in the blastocyst rate (p = 0.017) compared to control. The blastocyst rate reduction was also observed with 10 nM BPS. Furthermore, 10 µM BPS reduced the oocyte maturation rate, and 1 µM BPS decreased cumulus cell progesterone secretion. PR and AMH gene expression were reduced in cumulus cells. BPS induced a 5-fold increase in MAPK 3/1 activation (p = 0.04).

CONCLUSIONS

BPS impaired ewe oocyte developmental competence. The data suggest that BPS might not be a safe BPA analogue. Further studies are required to elucidate its detailed mechanism of action.

UFL1 Alleviates LPS-Induced Apoptosis by Regulating the NF-κB Signaling Pathway in Bovine Ovarian Granulosa Cells

Ubiquitin-like modifier 1 ligating enzyme 1 (UFL1) is an E3 ligase of ubiquitin fold modifier 1 (UFM1), which can act together with its target protein to inhibit the apoptosis of cells. Lipopolysaccharides (LPS) can affect the ovarian health of female animals by affecting the apoptosis of ovarian granulosa cells. The physiological function of UFL1 on the apoptosis of bovine (ovarian) granulosa cells (bGCs) remains unclear; therefore, we focused on the modulating effect of UFL1 on the regulation of LPS-induced apoptosis in ovarian granulosa cells. Our study found that UFL1 was expressed in both the nucleus and cytoplasm of bGCs. The results here demonstrated that LPS caused a significant increase in the apoptosis level of bGCs in cows, and also dramatically increased the expression of UFL1. Furthermore, we found that UFL1 depletion caused a significant increase in apoptosis (increased the expression of BAX/BCL-2 and the activity of caspase-3). Conversely, the overexpression of UFL1 relieved the LPS-induced apoptosis. In order to assess whether the inhibition of bGCs apoptosis involved in the nuclear factor-κB (NF-κB) signaling pathway resulted from UFL1, we detected the expression of NF-κB p-p65. LPS treatment resulted in a significant upregulation in the protein concentration of NF-κB p-p65, and knockdown of UFL1 further increased the phosphorylation of NF-κB p65, while UFL1 overexpression significantly inhibited the expression of NF-κB p-p65. Collectively, UFL1 could suppress LPS-induced apoptosis in cow ovarian granulosa cells, likely via the NF-κB pathway. These results identify a novel role of UFL1 in the modulation of bGC apoptosis, which may be a potential signaling target to improve the reproductive health of dairy cows.

Immature oocyte incidence: Contributing factors and effects on mature sibling oocytes in intracytoplasmic sperm injection cycles

Objective

The aim of this study was to investigate which factors contribute to the incidence of immature oocytes (germinal vesicle -GV- and metaphase I -MI-) and how they impact the intracytoplasmic sperm injection (ICSI) outcomes of sibling mature oocytes.

Methods

Data from 3,920 cycles performed from June/2010 to August/2016 in a private university-affiliated IVF center were evaluated for the influence of controlled ovarian stimulation protocol (COS) on immature oocytes incidence and its effects on ICSI outcomes.

Results

MI (p=0.004) and GV (p=0.029) number were negatively correlated with gonadotropin dose. Patients stimulated by rFSH had increased GV/oocyte rate in both GnRH agonists (p<0.001) and antagonist (p=0.042) protocols, in comparison to rFSH associated with rLH protocol. MI and GV/oocyte rates were negatively correlated to fertilization (p<0.001), high-quality embryo on da p<0.001; GV/oocyte p=0.033) and pregnancy (MI/oocyte p=0.002; GV/oocyte p=0.013) rates. Cycles above a 10.5% MI/oocyte cut-off were correlated to higher response to ovarian stimulation, poor embryo development and almost two times lower pregnancy rate. Immature oocyte incidence is affected by COS and impacts on ICSI outcomes.

Conclusion

Our evidence suggests that oocytes derived from a cohort with high incidence of maturation fail may have detrimental clinical outcomes.

Neonatal Exposure to Agonists and Antagonists of Sex Steroid Receptors Affects AMH and FSH Plasma Level and Their Receptors Expression in the Adult Pig Ovary

Simple Summary

The ovarian development and the establishment of ovarian reserve during fetal and/or neonatal life is critical for future reproductive success. Many environmental chemicals are known to negatively affect development and physiology of human and animal ovaries by interfering with endocrine systems, resulting in aberrant reproductive functions. The present study shows the long-term impact of neonatal exposure to agonists and antagonists of sex steroid receptors on AMH and FSH signalling in the ovary of adult pigs. Our findings suggest alteration in ovarian follicle recruitment from ovarian reserve arising from neonatal disruption of androgen/estrogen signalling induced by environmental endocrine active compounds. Everyday use of many endocrine disruptors is already prohibited after their harmful impacts on normal physiology have become known. Nevertheless, market introduction of new chemicals with potential deleterious influence on reproductive physiology has continued. Our outcomes confirm that a neonatal window plays an essential role in the physiological programming of ovarian function in adult pigs. The influence of environmental chemicals on this critical neonatal window needs to be investigated in order to gain a comprehensive view of deleterious interactions between endocrine disrupting chemicals and ovarian function.

Abstract

In this study piglets were injected with testosterone propionate (TP, an androgen), flutamide (FLU, an antiandrogen), 4-tert-octylphenol (OP, an estrogenic compound), ICI 182,780 (ICI, an antiestrogen) or corn oil (controls) between postnatal days 1 and 10 (N = 5/group). Then plasma anti-Müllerian hormone (AMH) and follicle stimulating hormone (FSH) concentration and the expression of their receptors were examined in the adult pig ovary. TP and FLU decreased plasma AMH and FSH concentration. In preantral follicles, TP resulted in upregulation of AMHR2 and FSHR expression, but decreased AMH protein abundance. FLU upregulated AMHR2 expression, while OP increased FSHR mRNA. In small antral follicles, OP upregulated ACVR1 and BMPR1A expression, while FLU increased BMPR1A mRNA. FLU and ICI resulted in upregulation of AMHR2 expression. TP and FLU upregulated AMH expression, while it was downregulated in response to OP or ICI. Moreover, OP and ICI resulted in downregulation of FSHR expression, while FLU decreased FSHR protein abundance. In conclusion, neonatal exposure to either agonist or antagonist of androgen receptor affected AMH and FSH signalling systems in preantral follicles. In small antral follicles these systems were influenced by compounds with estrogenic, antiestrogenic, and antiandrogenic activity. Consequently, these hormonal agents may cause an accelerated recruitment of primordial follicles and affect the cycling recruitment of small antral follicles in pigs.

Accelerated ovarian reserve depletion in female anti-Müllerian hormone knockout mice has no effect on lifetime fertility†

Anti-Müllerian hormone (AMH) inhibits the activation of primordial follicles in the ovary. This causes an increased rate of ovarian reserve depletion in Amh−/− mice. The depletion of the ovarian reserve is responsible for the onset of menopause but age-related infertility occurs in advance of ovarian reserve depletion. To determine whether accelerated loss of primordial follicles leads to earlier onset infertility, Amh−/− and Amh+/+ females were paired with Amh+/+ stud males and birth rates were recorded across the females’ reproductive lifespan. The number of primordial follicles remaining in the ovaries of Amh−/− and Amh+/+ females were quantified in two cohorts at 11–12 and 12–13 months of age. As expected, the ovarian reserve in the Amh−/− females became depleted approximately 1 month earlier than Amh+/+ females. However, no difference was observed in the cumulative number of births over the lifespan, nor were there any differences in mean littersize at any age. It is possible that the reproductive lifespan of mice is too short for sufficient divergence of primordial follicles numbers to cause differences in Amh−/− and Amh+/+ female fertility. An alternative explanation contradicts current thinking; the function of AMH may be unrelated to the longevity of the reproductive lifespan in female mice.

Influence of microwave-assisted dehydration on morphological integrity and viability of cat ovarian tissues: First steps toward long-term preservation of complex biomaterials at supra-zero temperatures

Ovarian tissue contains large pools of immature oocytes enclosed in primordial follicles, making it an attractive target for fertility preservation in female cancer patients, livestock and wild species. Compared to cryopreservation, desiccation and long-term storage of samples at supra-zero temperatures (using strategies inspired from small organisms to resist extreme environments) would be more cost-effective and convenient. The objective of the study was to characterize the influence of microwave-assisted dehydration on structural and functional properties of living ovarian tissues. While this method allows preservation of single cells (cat oocytes and sperm cells so far) using trehalose as the xeroprotectant, it has not been developed for multicellular tissues yet. Ovarian cortex biopsies were reversibly permeabilized, exposed to various concentrations of trehalose, and dried for different times using a commercial microwave under thermal control. Effective dehydration of samples along with proper trehalose retention were reached within 30 min of microwave drying. Importantly, the process did not affect morphology and DNA integrity of follicles or stromal cells. Moreover, transcriptional activity and survival of follicles were partially maintained following 10 min of drying, which already was compatible with storage at non-cryogenic temperatures. Present data provide critical foundation to develop dry-preservation techniques for long-term storage of living multicellular tissues.

The Impact of Chemotherapy on the Ovaries: Molecular Aspects and the Prevention of Ovarian Damage

Cancer treatment, such as chemotherapy, induces early ovarian follicular depletion and subsequent infertility. In order to protect gametes from the gonadotoxic effects of chemotherapy, several fertility preservation techniques—such as oocyte or embryo cryopreservation with or without ovarian stimulation, or cryopreservation of the ovarian cortex—should be considered. However, these methods may be difficult to perform, and the future use of cryopreserved germ cells remains uncertain. Therefore, improving the methods currently available and developing new strategies to preserve fertility represent major challenges in the area of oncofertility. Animal and ovarian culture models have been used to decipher the effects of different cytotoxic agents on ovarian function and several theories regarding chemotherapy gonadotoxicity have been raised. For example, cytotoxic agents might (i) have a direct detrimental effect on the DNA of primordial follicles constituting the ovarian reserve and induce apoptosis; (ii) induce a massive growth of dormant follicles, which are then destroyed; or (ii) induce vascular ovarian damage. Thanks to improvements in the understanding of the mechanisms involved, a large number of studies have been carried out to develop molecules limiting the negative impact of chemotherapy on the ovaries.

Serum Concentrations of AMH and E2 and Ovarian and Uterine Traits in Gilts

Simple Summary

Poor sow retention is a common issue amongst piggeries that creates excessive wastage. Premature culling is largely attributed to reproductive inadequacy. Thus, it is clear the traditional methods for selecting breeding females are inefficient and early markers of reproductive success are required. The aim of this study was to examine whether circulating levels of anti-Müllerian hormone and oestradiol could be useful indicators of ovarian and uterine traits in young gilts. The findings suggest that at a young age, anti-Müllerian hormone could be used to mark the ovarian reserve. Further research into whether the two hormones could be used to mark uterine capacity is needed.

Abstract

Poor sow retention due to reproductive failure is a common reproductive inefficiency amongst piggeries. This shows that traditional methods of gilt selection are inadequate and a marker of reproductive success is needed. The aim of this study was to determine whether circulating levels of AMH and E2 at D80 and D160 are associated with uterine and ovarian traits at D160. Uterine weight, horn length and horn diameter were measured, and ovarian follicle counts were determined histologically. There was a negative relationship between both D80 and D160 AMH levels and D160 ovarian follicle populations. There was also a positive relationship between D80 E2 levels and uterine capacity in gilts that were pubertal at D160. The findings indicate that D80 and D160 AMH could be used to predict ovarian reserve and that D80 E2 levels may be indicative of uterine capacity in precocial gilts.

Evaluation of ovarian reserve in women with psoriasis

The aim of this study is to evaluate ovarian reserve in women with psoriasis. Thirty-six women with psoriasis and 36 healthy women were enrolled in this prospective study. On day 3 of the menstrual cycle, blood samples for AMH and other hormones were collected. On the same day, antral follicle count (AFC), and ovarian volumes were measured. A multiple regression analysis was carried out to examine the contribution of factors to the serum AMH levels in patients with psoriasis. The serum AMH levels and ovarian volumes were lower in the psoriasis group than in the control group (1.85 ± 1.13 ng/ml vs 2.46 ± 1.21 ng/ml, p = .029 and 10.43 ± 3.08 cm³ vs 11.93 ± 3.01 cm³, p = .038). However, the mean AFC between the two groups was not significantly different. The psoriasis area severity index (PASI) score did not correlate with AMH. On the other hand, the duration of the disease negatively correlated with AMH, total AFC and ovarian volume. In the multiple regression analysis, duration of disease and total AFC were the most significant contributors to the serum AMH levels in patients with psoriasis. Autoimmune diseases may affect ovarian reserve regardless of immunosuppresive treatment. Longitudinal follow-ups regarding reproductive function might be required in women with psoriasis.

Ufl1/RCAD, a Ufm1 E3 ligase, has an intricate connection with ER stress

Ufmylation is a type of post-translational modification that deals with complex and fine-tuned cellular activities. This modification proceeds mainly through a three-step enzymatic reaction with ubiquitin-fold modifier 1 (Ufm1), ubiquitin-like modifier-activating enzyme 5 (Uba5), Ufm1-conjugating enzyme 1 (Ufc1) and Ufm1-specific ligase 1 (Ufl1). Ufl1 has previously been reported to function as a Ufm1 E3 ligase in the ufmylation system, but knowledge of its physiological functions remains poor. At the subcellular level, Ufl1 is enriched in the endoplasmic reticulum (ER), implying that it may regulate events closely associated with the ER and ER functions, such as protein synthesis, folding, and secretion, compounding lipids or sterols, and maintaining calcium homeostasis. Different physiological or pathological stress circumstances can, however, disrupt ER homeostasis, giving rise to an incongruous condition that is harmful to cellular activity and ultimately causes ER stress. Understanding the relationship between Ufl1 and ER stress in physiology and pathology may reveal the pathogenesis of some diseases and provide new guidance to create a therapeutic method. Herein, we review the current literature and discuss the relationship between Ufl1 and ER stress (in hematopoietic disease, heart disease, etc.), thus providing insight into additional diseases.

Neonatal exposure to agonists and antagonists of sex steroid receptors induces changes in the expression of oocyte-derived growth factors and their receptors in ovarian follicles in gilts

The objective of the present study was to examine the effects of neonatal exposure to either agonists or antagonists of androgen and estrogen receptors on the expression of growth and differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) and their cognate receptors (TGFBR1, BMPR1B, and BMPR2) in ovarian follicles of adult pigs. Piglets were injected subcutaneously with testosterone propionate (TP, an androgen, at 20 mg/kg bw), flutamide (FLU, an antiandrogen, at 50 mg/kg bw), 4-tert-octylphenol (OP, an estrogenic compound, 100 mg/kg bw), ICI 182,780 (ICI, an antiestrogen, 400 μg/kg bw), or corn oil (control) between postnatal Days 1 and 10 (n = 5/group). Ovarian follicles were excised from adult pigs on Days 8-11 of the estrous cycle. The expression of GDF9, BMP15, TGFBR1, BMPR1B and BMPR2 were examined in the population of preantral and small antral ovarian follicles using real-time PCR, Western blot and immunohistochemistry. In preantral follicles, the upregulation of GDF9 mRNA and protein expression was found in pigs that were neonatally exposed to TP or FLU, while administration of TP or ICI resulted in upregulation of BMP15. TGFBR1 and BMPR2 mRNA and protein expression were upregulated in preantral follicles of adult pigs that were neonatally exposed to TP or FLU, while administration of TP or ICI resulted in upregulation of BMPR1B. In small antral follicles, the mRNA and protein for TGFBR1 and BMPR2 were upregulated, while BMPR1B was downregulated in response to neonatal OP treatment. In addition, treatment with FLU upregulated BMPR1B and BMPR2 mRNA and protein expression, while downregulated the expression of TGFBR1. Moreover, GDF9 and BMP15 were immunolocalized in oocytes and granulosa cells of preantral follicles obtained from both control and treated ovaries. TGFBR1, BMPR1B and BMPR2 receptors were observed in the oocytes and granulosa cells of preantral follicles as well as in granulosa and theca cells of small antral follicles. In conclusion, the present study demonstrated neonatal exposure to either agonists or antagonists of androgen and estrogen receptors affected GDF9 and BMP15 signalling in ovaries of adult pigs. It seems that neonatal androgen excess or deficiency may lead to the acceleration of initial follicle recruitment, while neonatal exposure to compounds with antiandrogenic and estrogenic activity may disturb small antral follicles fate. Therefore, it confirms that neonatal window is critical for programming of ovarian function in pigs.

SMAD3 directly regulates cell cycle genes to maintain arrest in granulosa cells of mouse primordial follicles

Primordial follicles, consisting of granulosa cell (GC)-enveloped oocytes are maintained in a state of developmental arrest until activated to grow. The mechanism that operates to maintain this arrested state in GCs is currently unknown. Here, we show the TGFβ-activated transcription factor SMAD3 is expressed in primordial GC nuclei alongside the cell cycle proteins, cyclin D2 (CCND2) and P27. Using neonatal C57/Bl6 mouse ovaries densely populated with primordial follicles, CCND2 protein co-localised and was detected in complex with P27 by immunofluorescence and co-immunoprecipitation, respectively. In the same tissue, SMAD3 co-precipitated with DNA sequences upstream of Ccnd2 and Myc transcription start sites implicating both as direct SMAD3 targets. In older ovaries follicle growth was associated with nuclear exclusion of SMAD3 and reduced P27 and CCND2 in GCs, alongside elevated Myc expression. Brief (2 H) exposure of neonatal ovaries to TGFβ1 (10 ng/ml) in vitro led to immediate dissociation of SMAD3 from the Ccnd2 and Myc promoters. This coincided with elevated Myc and phospho-S6, an indicator of mTOR signalling, followed by a small increase in mean primordial GC number after 48 H. These findings highlight a concentration-dependent role for TGFβ signalling in the maintenance and activation of primordial follicles, through SMAD-dependent and independent signalling pathways, respectively.

Flutamide-induced alterations in transcriptional profiling of neonatal porcine ovaries

Background

Androgens are involved in the regulation of ovarian development during fetal/neonatal life. Environmental chemicals displaying anti-androgenic activities may affect multiple signal transduction pathways by blocking endogenous androgen action. The aim of the current study was to examine effects of the anti-androgen flutamide on the expression of coding transcripts and long non-coding RNAs (lncRNAs) in neonatal porcine ovaries. By employing RNA-Seq technology we aimed to extend our understanding of the role of androgens in neonatal folliculogenesis and examine the impact of the anti-androgen flutamide on ovarian function.

Method

Piglets were subcutaneously injected with flutamide (50 mg/kg BW) or corn oil (controls) between postnatal days 1 and 10 (n = 3/group). Ovaries were excised from the 11-day-old piglets and total cellular RNAs were isolated and sequenced.

Results

Flutamide-treated piglet ovaries showed 280 differentially expressed genes (DEGs; P-adjusted < 0.05 and log₂ fold change ≥1.0) and 98 differentially expressed lncRNAs (DELs; P-adjusted < 0.05 and log₂FC ≥ 1.0). The DEGs were assigned to GO term, covering biological processes, molecular functions and cellular components, which linked the DEGs to functions associated with cellular transport, cell divisions and cytoskeleton. In addition, STRING software demonstrated strongest interactions between genes related to cell proliferation. Correlations between DEGs and DELs were also found, revealing that a majority of the genes targeted by the flutamide-affected lncRNAs were associated with intracellular transport and cell division.

Conclusions

Our results suggest that neonatal exposure of pigs to flutamide alters the expression of genes involved in ovarian cell proliferation, ovarian steroidogenesis and oocyte fertilization, which in turn may affect female reproduction in adult life.

GSK-3β protects fetal oocytes from premature death via modulating TAp63 expression in mice

Background

Female mammals have a limited reproductive lifespan determined by the size of the primordial follicle pool established perinatally. Over two thirds of fetal oocytes are abolished via programmed cell death during early folliculogenesis. However, the underlying mechanisms governing fetal oocyte attrition remain largely elusive.

Results

Here, we demonstrate that glycogen synthase kinase-3 beta (GSK-3β) is indispensable for fetal oocyte maintenance during meiotic prophase I in mice. In vitro inhibition of GSK-3β activity or in vivo conditional deletion of Gsk-3β in the germline led to a dramatic loss of fetal oocytes via apoptosis, which subsequently resulted in a reduced capacity of the primordial follicle pool. Inhibition of GSK-3β also impeded meiotic progression in fetal oocytes and led to a deficiency in DNA double-strand break (DSB) repair associated with premature upregulation of Tap63, the major genome guardian of the female germline, following GSK-3β inhibition in fetal ovaries. Mechanistically, we demonstrated that aberrant nuclear translocation of β-catenin was responsible for the abnormal expression of TAp63 and global fetal oocyte attrition following GSK-3β inhibition.

Conclusions

In summary, GSK-3β was essential for sustaining fetal oocyte survival and folliculogenesis via fine-tuning the cytoplasmic-nuclear translocation of β-catenin, which in turn modulates timely TAp63 expression during meiotic prophase I in mice. Our study provides a perspective on the physiological regulatory role of DNA damage checkpoint signaling in fetal oocyte guardianship and female fertility.

Electronic supplementary material

The online version of this article (10.1186/s12915-019-0641-9) contains supplementary material, which is available to authorized users.

A bovine-specific FSH enzyme immunoassay and its application to study the role of FSH in ovarian follicle development during the postnatal period

The primary aim of this study was to develop a FSH enzyme immunoassay (EIA) for the bovine species. The newly developed EIA was validated for FSH determination in bovine plasma by comparison with an existing bovine FSH radioimmunoassay. The EIA detected bovine FSH with a high sensitivity (0.1 ng/ml). Cross-reactivity of the EIA was 0.01% with bovine LH, 51% with ovine FSH, <0.1% with porcine FSH and <0.01% with equine FSH. Using this EIA on different time series of plasma in cows, we have confirmed the presence of a FSH pre-ovulatory peak at estrus, of periodic FSH fluctuations accompanying the waves of terminal follicular development, and of FSH pulses, mainly asynchronous with LH ones, in the peri-ovulatory phase of the cycle. In a second objective, the EIA was used to assess the role of FSH in regulating the development of ovarian follicles up to the small antral stage in young calves. To answer this question, six calves were submitted to weekly blood sampling during their first 3 months of life, and FSH changes were studied concomitantly to those of anti-Müllerian hormone (AMH), a well-established endocrine marker of the ovarian population of small antral follicles in cows. In the ovaries of 3-month calves, the population of 3 to 5 mm follicles contained the highest intra-follicular AMH amounts, and the number of 3 to 5 mm follicles on ovaries was closely correlated with AMH concentrations in the plasma of calves at this age (rs = 0.94). Before 3 months of age, only two out of six calves showed a clear postnatal FSH peak in plasma, and no correlation was found between plasma FSH and AMH concentrations. These results indicate that female calves undergo different patterns of FSH secretion and that postnatal activation of follicular growth up to the small antral stage appears independent and not directly related to circulating FSH levels.

Repeatability of antral follicle count according parity in dairy cows

Ovarian reserve in cattle can be predicted by an indicator, the antral follicle count (AFC), which is easily determined via ovarian ultrasonography. However, the repeatability of AFC measurements in the same individual taken approximately 1 year apart after first parity remains unclear. This study, thus, aimed to clarify the between-lactation repeatability of AFC after first parity in dairy cows. We measured the AFC of the same individual cows consecutively across both first and second parity, both second and third parity, and both third and fourth parity in 31, 37, and 26 heads, respectively. The values of the intraclass correlation coefficients (ICC) for the AFCs in first–second and second–third parity cows were more than 0.8, and the value of the ICC for the AFCs in third–fourth parity cows was significantly lower than that in first–second parity cows (P = 0.01). Subsequently, based on the average number of AFCs measured at some points from first to third parity, we classified the cows into three tertiles: <11 (low), 11–15 (intermediate), and ≥ 15 (high). We then compared the reproductive performance of the first through third parity cows among the groups. The hazards of pregnancy by 200 days postpartum were higher in the high group than in the other groups (P < 0.05). Our findings demonstrate that between-lactation repeatability of AFC from first through third parity in dairy cows is very high, and that cows with an AFC of ≥ 15 have a better reproductive performance than cows with a low AFC.

Identification of microRNAs in granulosa cells from patients with different levels of ovarian reserve function and the potential regulatory function of miR-23a in granulosa cell apoptosis

This study aimed to determine the microRNA (miRNA) profiles in granulosa cells (GCs) from the follicular fluid (FF) of patients with varying levels of ovarian reserve function. We included 45 women undergoing in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) treatment. After collecting GCs from each patient, total RNA was extracted from 12 samples. Using Illumina/deep-sequencing technology, we analyzed the small RNAs in each group. Using the R package, we identified the differentially expressed (DE) miRNAs among patients with varying levels of ovarian reserve function. We identified 20 conserved and 3 novel miRNAs that were upregulated in the poor ovarian response (POR) group and 30 conserved miRNAs and 1 novel miRNA that were upregulated in the polycystic ovary syndrome (PCOS) group. Bioinformatics analysis revealed complementary pairing between miR-23a and the 3'-untranslated region (UTR) of the Sirt1 mRNA. miR-23a can regulate SIRT1 protein expression at the posttranscriptional level in GCs. Overexpressing miR-23a can inhibit the expression of SIRT1, decrease the stimulatory effect of SIRT1 on the ERK1/2 pathway, inhibit the expression of p-ERK1/2, and increase apoptosis in GCs. Previous studies confirmed that miR-23a targets SIRT1 and promotes apoptosis in GCs by inhibiting the ERK1/2 signaling pathway. This study provides a novel perspective regarding the role of miRNAs in the regulation of human GC apoptosis in vitro.

Outcomes of random start versus clomiphene citrate and gonadotropin cycles in occult premature ovarian insufficiency patients, refusing oocyte donation: a retrospective cohort study

The aim of this study is to present the clinical outcomes of a random start, a spontaneous folliculogenesis protocol versus Clomiphene Citrate and Gonadotropin treatment in women with occult premature ovarian insufficiency. Women underwent treatment between 1 February 2009, and 30 May 2016. 41 women were treated with the random start protocol while 48 cases received ovarian stimulation with clomiphene and gonadotropins. All included cases met the criteria of 4 months of oligo-ovulation, follicular-stimulating hormone levels over 30 IU/L and anti-Mullerian hormone levels below 0.30 ng/mL. The random start protocol involved following the subjects for up to 6 months until spontaneous folliculogenesis occurred. The mean number of oocytes collected, mature oocytes, fertilized oocytes, and grade II embryos were significantly higher in the random start protocol (p < .05). The doses of gonadotropin administration and hCG were significantly lower in the random start protocol (p < .05). The clinical pregnancy and live birth rates were significantly higher in the random start protocol (p < .05). Likely stimulation is of little benefit in women with occult premature ovarian insufficiency. Observation while waiting for spontaneous folliculogenesis results in better outcomes, and less oocyte collections.

Effect of bST administration on plasma concentrations of IGF-I and follicular dynamics and ovulation during the interovulatory cycle of sheep and goats

This study used a comparative approach to gather clinical information to assess the effect of bovine somatotropin (bST) on follicular dynamics and ovulation in sheep and goats during an interovulatory cycle. The performance of general markers of ovarian function and specific features of follicular dynamics obtained by daily ultrasonography (US) were used to assess the hypothesis that bST, associated with supraphysiological levels of IGF-I, was able to disrupt the follicular dynamics and ovulation in Highlander ewes and Saanen goats. In Exp 1, 15 ewes and 14 goats were estrous-synchronized (P₄-6 days + PGFα d-6) and then allocated to a bST-treated group (50 and 100 mg, Lactotropin^®; n = 5 females each) and to an untreated control group (5 ewes and 4 goats) to assess the activity of bST through plasma IGF-I (RIA). In Exp 2, 12 animals from each species were synchronized. At day 6, they were divided into a bST-group (100 mg in sheep and 50 mg in goats, n = 6 each) and an untreated control group (n = 6 each). Starting at day 6 and up to 22 days after ovulation in sheep and 25 days in goats, each female was subjected to daily US (10 mHz probe) to assess follicular and luteal (CL) dynamics and ovulation. This included assessments of both general ovarian features and specific follicular wave features. Our results showed that bST increased plasma IGF-I by day 3 (p < 0.01) when compared to the control group. Moreover, these concentrations were maintained for at least 10 days in sheep and 10 days in goats before returning to pre-treatment concentrations. Increases in IGF-I after bST doses were similar in terms of a daily and total amount (P > 0.10). Results from Exp.2 indicate that in sheep, bST administration had a subtle inhibitory effect on follicular function. However, bST in goats had a stronger influence, extending the interovulatory cycle (P = 0,034), increasing the number of follicular waves during the period (P = 0.003), and reducing the functional potential of large follicles as measured by their lower follicular diameter (P = 0.02), duration of the follicle waves (P = 0.02), and persistence of follicles after reaching their maximum diameters (P = 0.04). In addition, untreated sheep and goats shared common patterns of terminal follicular development and ovulations characterized by overlapping between follicular waves and ovulations of follicles from different waves, features not seen in cattle.

PGRMC1/2 promotes luteal vascularization and maintains the primordial follicles of mice

To determine whether conditional depletion of progesterone receptor membrane component (PGRMC) 1 and PGRMC2 affected ovarian follicle development, follicle distribution was assessed in ovaries of young (≈3-month-old) and middle-aged (≈6-month-old) control (Pgrmc1/2fl/fl) and double conditional PGRMC1/2-knockout (Pgrmc1/2d/d) mice. This study revealed that the distribution of primary, preantral and antral follicles was not altered in Pgrmc1/2d/d mice, regardless of the age. Although the number of primordial follicles was similar at ≈3 months of age, their numbers were reduced by ≈80% in 6-month-old Pgrmc1/2d/d mice compared to age-matched Pgrmc1/2fl/fl mice. The Pgrmc1/2d/d mice were generated using Pgr-cre mice, so ablation of Pgrmc1 and Pgrmc2 in the ovary was restricted to peri-ovulatory follicles and subsequent corpora lutea (CL). In addition, the vascularization of CL was attenuated in Pgrmc1/2d/d mice, although mRNA levels of vascular endothelial growth factor A (Vegfa) were elevated. Moreover, depletion of Pgrmc1 and Pgrmc2 altered the gene expression profile in the non-luteal component of the ovary such that Vegfa expression, a stimulator of primordial follicle growth, was elevated; Kit Ligand expression, another stimulator of primordial follicle growth, was suppressed and anti-Mullerian hormone, an inhibitor of primordial follicle growth, was enhanced compared to Pgrmc1/2fl/fl mice. These data reveal that luteal cell depletion of Pgrmc1 and 2 alters the expression of growth factors within the non-luteal component of the ovary, which could account for the premature demise of the adult population of primordial follicles. In summary, the survival of adult primordial follicles is dependent in part on progesterone receptor membrane component 1 and 2.

High-throughput ovarian follicle counting by an innovative deep learning approach

The evaluation of the number of mouse ovarian primordial follicles (PMF) can provide important information about ovarian function, regulation of folliculogenesis or the impact of chemotherapy on fertility. This counting, usually performed by specialized operators, is a tedious, time-consuming but indispensable procedure.The development and increasing use of deep machine learning algorithms promise to speed up and improve this process. Here, we present a new methodology of automatically detecting and counting PMF, using convolutional neural networks driven by labelled datasets and a sliding window algorithm to select test data. Trained from a database of 9 millions of images extracted from mouse ovaries, and tested over two ovaries (3 millions of images to classify and 2 000 follicles to detect), the algorithm processes the digitized histological slides of a completed ovary in less than one minute, dividing the usual processing time by a factor of about 30. It also outperforms the measurements made by a pathologist through optical detection. Its ability to correct label errors enables conducting an active learning process with the operator, improving the overall counting iteratively. These results could be suitable to adapt the methodology to the human ovarian follicles by transfer learning.

Towards international standardization of immunoassays for Müllerian inhibiting substance/anti-Müllerian hormone

Research question

Is formulated and lyophilized, recombinant human Müllerian inhibiting substance, also known as anti-Müllerian hormone (AMH), suitable for the preparation of a WHO international standard to calibrate AMH immunoassays?

Design

The AMH content of a trial preparation, coded SS-581, was determined by five laboratories using seven immunoassay methods. Participants were requested to report the content of the preparation in terms of their method calibrators through the measurement of a minimum of five concentrations in the linear part of the dose-response curve. Participants were also asked to measure, concomitantly, a panel of six serum samples containing AMH at concentrations of 0.1–13.0 ng/ml.

Results

Across all assays, including two automated assays in development, the geometric mean content was 361.76 ng/ampoule with a geometric coefficient of variation (GCV%) of 39.95%. When measured by immunoassays that were commercially available at the time of the study, the mean content was 423.08 ng/ampoule, with a GCV% of 26.67%. The inter-method geometric means of five serum samples with an AMH concentration >0.3 ng/ml and measured concomitantly with dilutions of SS-581 varied with a range of GCV% of 14.90–22.35%, which may reflect the use of serum sample value transfer to calibrate current immunoassays, some of which use non-human AMH calibrators. The AMH in trial preparation SS-581 was shown to be biologically active in the Müllerian duct regression assay.

Conclusions

A reference material prepared using human recombinant AMH is a promising candidate for the preparation of an international standard for AMH for immunoassays calibrated to recombinant human AMH.

The local regulation of folliculogenesis by members of the transforming growth factor superfamily and its relevance for advanced breeding programmes

Regulation of the growth and maturation of the ovarian follicle is critical for normal reproductive function. Alterations in this growth can lead to pathological conditions, such as cystic follicles, reduced oocyte quality, or an abnormal endocrine environment leading to poor fertility. Alterations in follicular growth also influence the number of follicles ovulating and thus can change litter size. Both endocrine factors, such as follicle stimulating hormone and luteinizing hormone, as well as local factors, are known to regulate follicular growth and development. This review will focus on the role of local factors in regulation of ovarian follicular growth in ruminants, with a focus on members of the transforming growth factor superfamily. The potential role of these factors in regulating proliferation, apoptosis, steroidogenesis and responsiveness to gonadotrophins will be considered.

Impact of a gestational exposure to diesel exhaust on offspring gonadal development: experimental study in the rabbit

The aim of the present work was to address experimentally the possible impact of exposure to air pollution during gestation on the differentiation and function of the gonads of the offspring using a rabbit model. Rabbits were exposed daily to diluted diesel exhaust gas or filtered air from the 3rd until the 27th day of gestation, during which time germ cells migrate in genital ridges and divide, and fetal sex is determined. Offspring gonads were collected shortly before birth (28th day of gestation) or after puberty (7.5 months after birth). The structure of the gonads was analyzed by histological and immunohistological methods. Serum concentrations of testosterone and anti-Müllerian hormone were determined using ELISA. The morphology and the endocrine function of the gonads collected just at the arrest of the exposure were similar in polluted and control animals in both sexes. No differences were observed as well in gonads collected after puberty. Sperm was collected at the head of the epididymis in adults. Sperm motility and DNA fragmentation were measured. Among all parameters analyzed, only the sperm DNA fragmentation rate was increased three-fold in exposed males. Mechanisms responsible for these modifications and their physiological consequences are to be further clarified.

Circulating anti-Müllerian hormone and breast cancer risk: A study in ten prospective cohorts

A strong positive association has been observed between circulating anti-Müllerian hormone (AMH), a biomarker of ovarian reserve, and breast cancer risk in three prospective studies. Confirming this association is important because of the paucity of biomarkers of breast cancer risk in premenopausal women. We conducted a consortium study including ten prospective cohorts that had collected blood from premenopausal women. A nested case-control design was implemented within each cohort. A total of 2,835 invasive (80%) and in situ (20%) breast cancer cases were individually matched to controls (n = 3,122) on age at blood donation. AMH was measured using a high sensitivity enzyme-linked immunoabsorbent assay. Conditional logistic regression was applied to the aggregated dataset. There was a statistically significant trend of increasing breast cancer risk with increasing AMH concentration (ptrend across quartiles <0.0001) after adjusting for breast cancer risk factors. The odds ratio (OR) for breast cancer in the top vs. bottom quartile of AMH was 1.60 (95% CI = 1.31-1.94). Though the test for interaction was not statistically significant (pinteraction  = 0.15), the trend was statistically significant only for tumors positive for both estrogen receptor (ER) and progesterone receptor (PR): ER+/PR+: ORQ4-Q1  = 1.96, 95% CI = 1.46-2.64, ptrend <0.0001; ER+/PR-: ORQ4-Q1  = 0.82, 95% CI = 0.40-1.68, ptrend  = 0.51; ER-/PR+: ORQ4-Q1  = 3.23, 95% CI = 0.48-21.9, ptrend  = 0.26; ER-/PR-: ORQ4-Q1  = 1.15, 95% CI = 0.63-2.09, ptrend  = 0.60. The association was observed for both pre- (ORQ4-Q1 = 1.35, 95% CI = 1.05-1.73) and post-menopausal (ORQ4-Q1  = 1.61, 95% CI = 1.03-2.53) breast cancer (pinteraction  = 0.34). In this large consortium study, we confirmed that AMH is associated with breast cancer risk, with a 60% increase in risk for women in the top vs. bottom quartile of AMH.

Initiation of follicular atresia: gene networks during early atresia in pig ovaries

In mammals, more than 99% of ovarian follicles undergo a degenerative process known as atresia. The molecular events involved in atresia initiation remain incompletely understood. The objective of this study was to analyze differential gene expression profiles of medium antral ovarian follicles during early atresia in pig. The transcriptome evaluation was performed on cDNA microarrays using healthy and early atretic follicle samples and was validated by quantitative PCR. Annotation analysis applying current database (Sus scrofa 11.1) revealed 450 significantly differential expressed genes between healthy and early atretic follicles. Among them, 142 were significantly upregulated in early atretic with respect to healthy group and 308 were downregulated. Similar expression trends were observed between microarray data and quantitative RT-PCR confirmation, which indicated the reliability of the microarray analysis. Further analysis of the differential expressed genes revealed the most significantly affected biological functions during early atresia including blood vessel development, regulation of DNA-templated transcription in response to stress and negative regulation of cell adhesion. The pathway and interaction analysis suggested that atresia initiation associates with (1) a crosstalk of cell apoptosis, autophagy and ferroptosis rather than change of typical apoptosis markers, (2) dramatic shift of steroidogenic enzymes, (3) deficient glutathione metabolism and (4) vascular degeneration. The novel gene candidates and pathways identified in the current study will lead to a comprehensive view of the molecular regulation of ovarian follicular atresia and a new understanding of atresia initiation.

Histone demethylase KDM4A and KDM4B expression in granulosa cells from women undergoing in vitro fertilization

PURPOSE

To assess expression of the histone demethylases KDM4A and KDM4B in granulosa collected from women undergoing oocyte retrieval and to determine if expression was related to pregnancy outcome.

METHODS

Cumulus and mural granulosa cells were obtained from women undergoing oocyte retrieval. KDM4A and KDM4B mRNA expression was determined by qRT-PCR. KDM4A and KDM4B proteins were immunohistochemically localized in ovarian tissue sections obtained from archival specimens.

RESULTS

KDM4A and KDM4B protein was localized to oocytes, granulosa cells, and theca and luteal cells in ovaries from reproductive-aged women. KDM4A and KDM4B mRNA expression was overall higher in cumulus compared to mural granulosa. When comparing granulosa demethylase gene expression, KDM4A and KDM4B mRNA expression was higher in both cumulus and mural granulosa from not pregnant patients compared to patients in the pregnant-live birth group.

CONCLUSIONS

Histone demethylases KDM4A and KDM4B mRNA are differentially expressed in cumulus and mural granulosa. Expression of both KDM4A and KDM4B mRNA was lower in cumulus granulosa and mural granulosa from pregnant compared to not pregnant patients. These findings suggest that altered expression of histone demethylases may impact epigenetic changes in granulosa cells associated with pregnancy.