Coordination of Ovulation and Oocyte Maturation: A Good Egg at the Right Time

Notch Signaling Induced by Endoplasmic Reticulum Stress Regulates Cumulus-Oocyte Complex Expansion in Polycystic Ovary Syndrome

Endoplasmic reticulum (ER) stress activated in granulosa cells contributes to the pathophysiology of polycystic ovary syndrome (PCOS). In addition, recent studies have demonstrated that Notch signaling plays multiple roles in the ovary via cell-to-cell interactions. We hypothesized that ER stress activated in granulosa cells of antral follicles in PCOS induces Notch signaling in these cells, and that activated Notch signaling induces aberrant cumulus-oocyte complex (COC) expansion. Expression of Notch2 and Notch-target transcription factors was increased in granulosa cells of PCOS patients and model mice. ER stress increased expression of Notch2 and Notch-target transcription factors in cultured human granulosa-lutein cells (GLCs). Inhibition of Notch signaling abrogated ER stress-induced expression of genes associated with COC expansion in cultured human GLCs, as well as ER stress-enhanced expansion of cumulus cells in cultured murine COCs. Furthermore, inhibition of Notch signaling reduced the areas of COCs in PCOS model mice with activated ER stress in the ovary, indicating that Notch signaling regulates COC expansion in vivo. Our findings suggest that Notch2 signaling is activated in granulosa cells in PCOS and regulates COC expansion. It remains to be elucidated whether aberrant COC expansion induced by the ER stress-Notch pathway is associated with ovulatory dysfunction in PCOS patients.

Effect of dominant follicle status at the time of retrieval on the clinical outcomes in natural cycle IVF combined with immature oocyte treatment

Objective: It is commonly believed that the oocytes from small follicles are unhealthy when a dominant follicle (DF) is recruited in the ovaries, especially when the DF is ovulated. This study aims to confirm whether the presence or ovulation of DF at the time of retrieval affects the clinical outcome of the natural cycle IVF with in vitro maturation (NC-IVF/M) treatment.

Methods: Data were collected from 446 women with regular menstrual cycle and 536 retrieval cycles using NC-IVF/M treatment. The cycles were divided into three groups based on the results of the oocyte retrieval cycle. Group A covers the collection of oocytes from the DF and small follicles; Group B incorporates failed oocyte retrieval from DF and then the oocytes are retrieved only from small follicles; and Group C includes the retrieval of oocytes only from small follicles accompanied with an ovulated DF. Furthermore, Group B and C have subgroups to include whether in vivo matured oocytes were obtained from small follicles. Following aspiration of DF and small follicles, mature oocytes were inseminated on the date of retrieval by intracytoplasmic sperm injection (ICSI) and the immature oocytes were matured in vitro. If the immature oocytes were matured in vitro, they were inseminated using ICSI, and then the embryos obtained from in vivo and in vitro matured oocytes were transferred accordingly.

Results: The oocytes from DF were successfully retrieved in 445 cycles (83.0%), failed to be retrieved in 54 cycles (10.1%) and ovulated in 37 cycles (6.9%). In Group A, an average of 2.0 ± 1.7 mature oocytes were retrieved, which was significantly higher than the average of Group B, with 1.3 ± 1.3 matured oocytes and Group C, with an average of 1.1 ± 1.5 matured oocytes (P < 0.01). However, the average number of immature oocytes retrieved from each group show no difference among the three groups. There was no significant difference in maturation rates of immature oocytes, fertilization rates among the three groups. The clinical pregnancy rate per transfer cycle is 34.5%, 34.6% and 25.7% in Group A, B and C, respectively. No significant differences were observed in embryonic development and implantation capacity in Group B and C in comparison to Group A. And there was no significant difference in clinical pregnancy, implantation, live birth and miscarriage rates among the three groups. No significant differences were observed in the developmental and implantation capacity according to with or without in vivo matured oocytes were retrieved in Group B and Group C.

Conclusion: The presence or ovulation of the dominant follicle from the ovaries does not significantly influence the developmental and implantation capacity of immature oocytes retrieved from small follicles, suggesting that NC-IVF/M is a promising treatment option for women without ovarian stimulation.

Signal pathway of LH-induced expression of nuclear progestin receptor in vertebrate ovulation

Nuclear progestin receptor (PGR), which is induced in the follicles destined to undergo ovulation, is believed to be obligatory for rupture of the follicles during ovulation in vertebrates. Studies in some mammals and teleost medaka have revealed the outline of the central signaling pathway that leads to the PGR expression in the preovulatory follicles at ovulation. In this review, we summarize the current knowledge on what signaling mediators are involved in the LH-induced follicular expression of PGR at ovulation in these animals. LH-inducibility of follicular PGR expression is conserved. In both group of animals, activation of the LH receptor on the granulosa cell surface with LH commonly results in the increase of intracellular cAMP levels, while the downstream signaling cascades activated by high level of cAMP are totally different between mice and medaka. PGR is currently presumed to be induced via PKA/CREB-mediated transactivation and ERK1/2-dependent signaling in mice, but the receptor is induced via EPAC/RAP and AKT/CREB pathways in the teleost medaka. The differences and similarities in the signaling pathways for PGR expression between them is discussed from comparative and evolutionary aspects. We also discussed questions concerning PGR expression and its regulation needed to be investigated in future.

The granulosa cell response to luteinizing hormone is partly mediated by YAP1-dependent induction of amphiregulin

Background

The LH surge is a pivotal event that triggers multiple key ovarian processes including oocyte maturation, cumulus expansion, follicular wall rupture and luteinization of mural granulosa and theca cells. Recently, LH-dependent activation of the Hippo signaling pathway has been shown to be required for the differentiation of granulosa cells into luteal cells. Still, the precise interactions between Hippo and LH signaling in murine granulosa cells remain to be elucidated.

Methods

To detect the expression of effectors of the Hippo pathway, western blot, immunohistochemical and RT-qPCR analyses were performed on granulosa cells treated with LH in vitro or isolated from immature mice treated with eCG and hCG. Cultured granulosa cells were pretreated with pharmacologic inhibitors to identify the signaling pathways involved in Hippo regulation by LH. To study the roles of Yap1 and Taz in the regulation of the LH signaling cascade, RT-qPCR and microarray analyses were done on granulosa cells from Yap1^f/f;Taz^f/f mice treated with an adenovirus to drive cre expression. RT-qPCR was performed to evaluate YAP1 binding to the Areg promoter following chromatin immunoprecipitation of granulosa cells collected from mice prior to or 60 min following hCG treatment.

Results

Granulosa cells showed a transient increase in LATS1, YAP1 and TAZ phosphorylation levels in response to the ovulatory signal. This Hippo activation by LH was mediated by protein kinase A. Furthermore, Yap1 and Taz are required for the induction of several LH target genes such as Areg, Pgr and Ptgs2, and for the activation of the ERK1/2 pathway. Consistent with these results, there was a substantial overlap between genes that are upregulated by LH and those that are downregulated following loss of Yap1/Taz, highlighting a major role for Hippo in mediating LH actions in the ovulation process. Finally, we showed that there is a marked recruitment of YAP1 to the Areg promoter of granulosa cells in response to hCG stimulation.

Conclusions

Overall, these results indicate that Hippo collaborates with the cAMP/PKA and ERK1/2 pathways to participate in the precise regulation of the LH cascade, and that Areg, as a direct transcriptional target of YAP1, is involved in mediating its actions in the ovary.

Intraovarian, Isoform-Specific Transcriptional Roles of Progesterone Receptor in Ovulation

Progesterone receptor (PGR) activity is obligatory for mammalian ovulation; however, there is no established direct functional pathway explaining how progesterone receptor completely and specifically regulates oocyte release. This study examined the overarching cell- and isoform-specific effects of the PGR within each cellular compartment of the ovary, using mice null for the PGR (PRKO), as well as isoform-specific null mice. The PGR was expressed in ovarian granulosa and stromal cells and although PRKO ovaries showed no visible histological changes in preovulatory ovarian morphology, follicle rupture did not occur. Reciprocal ovarian transplant experiments established the necessity of ovarian PGR expression for ovulation. Cumulus–oocyte complexes of PRKO mice exhibited normal morphology but showed some altered gene expression. The examination of mitochondrial activity showed subtle differences in PRKO oocytes but no differences in granulosa cell respiration, glycolysis or β-oxidation. Concurrently, RNA-seq identified novel functional pathways through which the PGR may regulate ovulation. PGR-A was the predominant transcriptionally active isoform in granulosa cells and 154 key PGR-dependent genes were identified, including a secondary network of transcription factors. In addition, the PGR regulated unique gene networks in the ovarian stroma. Collectively, we establish the effector pathways activated by the PGR across the ovarian cell types and conclude that PGR coordinates gene expression in the cumulus, granulosa and stromal cells at ovulation. Identifying these networks linking the PGR to ovulation provides novel targets for fertility therapeutics and nonhormonal contraceptive development.

Dibutyltin dichloride exposure affects mouse oocyte quality by inducing spindle defects and mitochondria dysfunction

Dibutyltin dichloride (DBTCl) is a widespread environmental pollutant that is frequently employed as a light and heat sustainer for polyvinyl chloride (PVC) plastics and is a teratogen in vivo. Nevertheless, its destructiveness in mammalian oocytes remains unclear. This study highlighted the consequences of DBTCl vulnerability on mouse oocyte. Our results revealed that exposure to 5.0 mg/kg/day of DBTCl for ten days reduced the number of mature follicles and oocytes in the ovaries and inhibited the meiotic maturation of oocytes. Single-cell transcriptomic analysis indicated that DBTCl exposure interfered with the expression of more than 400 genes in oocytes, including those involved in multiple biological pathways. Specifically, DBTCl exposure impaired spindle assembly and chromosome alignment. In addition, DBTCl exposure caused mitochondrial dysfunction, which led to the accumulation of reactive oxygen species (ROS) and induced apoptosis. In summary, our study illustrates that mitochondrial dysfunction and redox perturbation are the major causes of the reduced quality of oocytes exposed to DBTCl.

Steroidogenic Factor 1 Regulation of the Hypothalamic-Pituitary-Ovarian Axis of Adult Female Mice

The orphan nuclear receptor steroidogenic factor-1 (SF-1 or NR5A1) is an indispensable regulator of adrenal and gonadal formation, playing roles in sex determination, hypothalamic development, and pituitary function. This study aimed to identify the roles of SF-1 in postnatal female reproductive function. Using a progesterone receptor-driven Cre recombinase, we developed a novel murine model, characterized by conditional depletion of SF-1 [PR-Cre;Nr5a1f/f; conditional knockout (cKO)] in the hypothalamic-pituitary-gonadal axis. Mature female cKO were infertile due to the absence of ovulation. Reduced gonadotropin concentrations in the pituitary gland that were nevertheless sufficient to maintain regular estrous cycles were observed in mature cKO females. The cKO ovaries showed abnormal lipid accumulation in the stroma, associated with an irregular expression of cholesterol homeostatic genes such as Star, Scp2, and Acat1. The depletion of SF-1 in granulosa cells prevented appropriate cumulus oöphorus expansion, characterized by reduced expression of Areg, Ereg, and Ptgs2. Exogenous delivery of gonadotropins to cKO females to induce ovulation did not restore fertility and was associated with impaired formation and function of corpora lutea accompanied by reduced expression of the steroidogenic genes Cyp11a1 and Cyp19a1 and attenuated progesterone production. Surgical transplantation of cKO ovaries to ovariectomized control animals (Nr5a1f/f) resulted in 2 separate phenotypes, either sterility or apparently normal fertility. The deletion of SF-1 in the pituitary and in granulosa cells near the moment of ovulation demonstrated that this nuclear receptor functions across the pituitary-gonadal axis and plays essential roles in gonadotropin synthesis, cumulus expansion, and luteinization.

Inter-Alpha-Trypsin Inhibitor Heavy Chain 4 Plays an Important Role in the Development and Reproduction of Nilaparvata lugens

Simple Summary

The brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae), is a destructive insect pest of rice. It causes reductions in rice yield and great economic losses. In this study, we used RNAi to explore the function of the inter-alpha-trypsin inhibitor heavy chain 4 (ITIH4) gene in the development and reproduction of the brown planthopper. Our results revealed that ITIH4 influences the survival, ovarian development, egg production, and egg hatching of this insect, indicating that ITIH4 plays important roles in development and reproduction. Considering the importance of ITIH4 in the brown planthopper, it may be a potential target for pest management.

Abstract

The brown planthopper, Nilaparvata lugens, is a difficult-to-control insect pest affecting rice yields in Asia. As a structural component of the inter-alpha-trypsin inhibitor (ITI), the inter-alpha-trypsin inhibitor heavy chain (ITIH) has been reported to be involved in various inflammatory or malignant disorders, ovarian development, and ovulation. To reveal the function of ITIH4 in N. lugens, the gene encoding N. lugens ITIH4 (NlITIH4) was cloned and characterized. NlITIH4 contains a signal peptide, a vault protein inter-alpha-trypsin domain, and a von Willebrand factor type A domain. qPCR analysis showed that NlITIH4 was expressed at all developmental stages and in all tissues (fat body, ovary, and gut), with the highest expression in the fat body. Double stranded NlITIH4 (dsNlITIH4) injection clearly led to an RNAi-mediated inhibition of the expression of NlITIH4 and resulted in reduced survival, delayed ovarian development, and reduced egg production and egg hatching. These results indicate that NlITIH4 plays an important role in the development and reproduction of N. lugens.

Melatonin Signaling Pathways Implicated in Metabolic Processes in Human Granulosa Cells (KGN)

Female reproduction depends on the metabolic status, especially during the period of folliculogenesis. Even though it is believed that melatonin can improve oocyte competence, there is still limited knowledge of how it can modulate metabolic processes during folliculogenesis and which signaling pathways are involved in regulating gene expression. To investigate the effects of melatonin on metabolic signals during the antral stage of follicular development, human granulosa-like tumor cells (KGN) were treated with melatonin or forskolin, and gene expression was analyzed with RNA-seq technology. Following appropriate normalization and the application of a fold change cut-off of 1.5 (FC 1.5, p ≤ 0.05), 1009 and 922 genes were identified as differentially expressed in response to melatonin and forskolin, respectively. Analysis of major upstream regulators suggested that melatonin may activate PKB/mTOR signaling pathways to program the metabolism of KGN cells to support slower growth and differentiation and to prevent follicular atresia. Similarly, PKA activation through stimulation of cAMP synthesis with FSK seemed to exert the same effects as melatonin in reducing follicular growth and regulating differentiation. This study suggests that melatonin may act through PKA and PKB simultaneously in human granulosa cells to prevent follicular atresia and early luteinization at the antral stage.

The role of cellular senescence in female reproductive aging and the potential for senotherapeutic interventions

BACKGROUND

Advanced maternal age is associated with decreased oocyte quantity and quality as well as uterine and placental dysfunctions. These changes lead to infertility, pregnancy complications and birth defects in the offspring. As the mean age of giving birth is increasing worldwide, prevention of age-associated infertility and pregnancy complications, along with the more frequent use of ART, become extremely important. Currently, significant research is being conducted to unravel the mechanisms underlying female reproductive aging. Among the potential mechanisms involved, recent evidence has suggested a contributing role for cellular senescence, a cellular state of irreversible growth arrest characterized by a hypersecretory and pro-inflammatory phenotype. Elucidating the role of senescence in female reproductive aging holds the potential for developing novel and less invasive therapeutic measures to prevent or even reverse female reproductive aging and increase offspring wellbeing.

OBJECTIVE AND RATIONALE

The review will summarize the positive and negative implications of cellular senescence in the pathophysiology of the female reproductive organs during aging and critically explore the use of novel senotherapeutics aiming to reverse and/or eliminate their detrimental effects. The focus will be on major senescence mechanisms of the ovaries, the uterus, and the placenta, as well as the potential and risks of using senotherapies that have been discovered in recent years.

SEARCH METHODS

Data for this review were identified by searches of MEDLINE, PubMed and Google Scholar. References from relevant articles using the search terms 'Cellular Senescence', 'Aging', 'Gestational age', 'Maternal Age', 'Anti-aging', 'Uterus', 'Pregnancy', 'Fertility', 'Infertility', 'Reproduction', 'Implant', 'Senolytic', 'Senostatic', 'Senotherapy' and 'Senotherapeutic' where selected. A total of 182 articles published in English between 2005 and 2020 were included, 27 of which focus on potential senotherapies for reproductive aging. Exclusion criteria were inclusion of the terms 'male' and 'plants'.

OUTCOMES

Aging is a major determinant of reproductive wellbeing. Cellular senescence is a basic aging mechanism, which can be exploited for therapeutic interventions. Within the last decade, several new strategies for the development and repurposing of drugs targeting senescent cells have emerged, such as modulators of the anti-inflammatory response, oxidative stress, DNA damage, and mitochondria and protein dysfunctions. Several studies of female reproductive aging and senotherapies have been discussed that show promising results for future interventions.

WIDER IMPLICATIONS

In most countries of the Organization for Economic Co-operation and Development, the average age at which women give birth is above 30 years. Currently, in countries such as the Netherlands, Australia, Spain, Finland, Germany and the UK, birth rates among 30- to 34-year-olds are now higher than in any other age groups. This review will provide new knowledge and scientific advancement on the senescence mechanisms during female reproductive aging, and benefit fundamental and clinical scientists and professionals in the areas of reproduction, cancer, immunobiology and fibrosis.

Excessive follicle-stimulating hormone during ovarian stimulation of cattle may induce premature luteinization of most ovulatory-size follicles†

High follicle-stimulating hormone (FSH) doses during ovarian stimulation are detrimental to ovulatory follicle function and decrease live birth rate in cattle and women. However, the mechanism whereby excessive FSH causes ovarian dysfunction is unknown. This study tested the hypothesis that excessive FSH during ovarian stimulation induces premature luteinization of ovulatory-size follicles. Small ovarian reserve heifers were injected twice daily for 4 days with 70 IU (N = 7 heifers) or 210 IU (N = 6 heifers) Folltropin-V [commercial FSH-enriched preparation of porcine pituitary glands with minor (<1%) luteinizing hormone (LH) contamination, cpFSH]. Ovulatory-size (≥10 mm) follicles were excised from ovaries after the last cpFSH injection and hormone concentrations in follicular fluid (FF) were determined using ELISA. Luteinization was monitored by assessing cumulus cell-oocyte complex (COC) morphology and measuring concentrations of estradiol (E), progesterone (P), and oxytocin (O) in FF. COCs were classified as having compact (cCOC) or expanded (eCOC) cumulus cell layers, and as estrogen-active (E:P in FF ≥1), estrogen-inactive (EI, E:P in FF ≤1 > 0.1), or extreme-estrogen-inactive (EEI, E:P in FF ≤0.1). A high proportion (72%) of ovulatory-size follicles in 210 IU, but not 70 IU, dose heifers displayed eCOCs. The high doses also produced higher proportions of EI or EEI follicles which had lower E:P ratio and/or E but higher P and/or O concentrations compared with the 70 IU dose heifers. In conclusion, excessive cpFSH doses during ovarian stimulation may induce premature luteinization of most ovulatory-size follicles in heifers with small ovarian reserves.

Autophagy regulates differentiation of ovarian granulosa cells through degradation of WT1

Ovarian granulosa cells (GCs) proliferate and differentiate along with follicular growth, and this is indispensable for oocyte development and female fertility. Although the role of macroautophagy/autophagy in ovarian function has been reported, its contribution to the regulation of GC characteristics remains elusive. The siRNA-mediated knockdown of two key autophagy-related genes ATG5 and BECN1 and the autophagy inhibitor chloroquine were used to interfere with autophagy in GCs. Inhibition of autophagy both genetically and pharmacologically resulted in decreased expression of genes associated with GC differentiation, including CYP19A1/Aromatase and FSHR, as well as in reduced estradiol synthesis. Mechanistically, when autophagy was disrupted, the transcription factor WT1 accumulated in GCs due to its insufficient degradation by the autophagic pathway, and this inhibited GC differentiation. Finally, decreased expression of several autophagy-related genes, as well as reduced LC3-II:LC3-I and elevated SQSTM1/p62 protein levels, which are indications of decreased autophagy, were detected in GCs from biochemical premature ovarian insufficiency patients. In summary, our study reveals that autophagy regulates the differentiation of ovarian GCs by degrading WT1 and that insufficient autophagy might be involved in ovarian dysfunction.

Regulatory Role and Potential Importance of GDF-8 in Ovarian Reproductive Activity

Growth differentiation factor-8 (GDF-8) is a member of the transforming growth factor-beta superfamily. Studies in vitro and in vivo have shown GDF-8 to be involved in the physiology and pathology of ovarian reproductive functions. In vitro experiments using a granulosa-cell model have demonstrated steroidogenesis, gonadotrophin responsiveness, glucose metabolism, cell proliferation as well as expression of lysyl oxidase and pentraxin 3 to be regulated by GDF-8 via the mothers against decapentaplegic homolog signaling pathway. Clinical data have shown that GDF-8 is expressed widely in the human ovary and has high expression in serum of obese women with polycystic ovary syndrome. GDF-8 expression in serum changes dynamically in patients undergoing controlled ovarian hyperstimulation. GDF-8 expression in serum and follicular fluid is correlated with the ovarian response and pregnancy outcome during in vitro fertilization. Blocking the GDF-8 signaling pathway is a potential therapeutic for ovarian hyperstimulation syndrome and ovulation disorders in polycystic ovary syndrome. GDF-8 has a regulatory role and potential importance in ovarian reproductive activity and may be involved in folliculogenesis, ovulation, and early embryo implantation.

Advances in the study of CDC42 in the female reproductive system

CDC42 is a member of the Rho‐GTPase family and is involved in a variety of cellular functions including regulation of cell cycle progression, constitution of the actin backbone and membrane transport. In particular, CDC42 plays a key role in the establishment of polarity in female vertebrate oocytes, and essential to this major regulatory role is its local occupation of specific regions of the cell to ensure that the contractile ring is assembled at the right time and place to ensure proper gametogenesis. The multifactor controlled ‘inactivation‐activation’ process of CDC42 also allows it to play an important role in the multilevel signalling network, and the synergistic regulation of multiple genes ensures maximum precision during gametogenesis. The purpose of this paper is to review the role of CDC42 in the control of gametogenesis and to explore its related mechanisms, with the aim of further understanding the great research potential of CDC42 in female vertebrate germ cells and its future clinical translation.

Follicle-stimulating hormone mediates the consumption of serum-derived glycogen by bovine cumulus-oocyte complexes during in vitro maturation

Background and Aim:

Oocyte in vitro maturation (IVM) is an appealing approach for several assisted reproductive technologies and dissecting oocyte maturation. Nonetheless, IVM leads to lower developmental competence and usually relies on undefined, serum-containing media. Therefore, biochemical profiling aimed to explore fluctuations in IVM media content during the acquisition of oocyte developmental competence.

Materials and Methods:

Bovine cumulus-oocyte complexes (COCs) underwent IVM in TCM199 medium with Earle’s salts, supplemented with 2.0 mM L-glutamine, 10% fetal bovine serum, antibiotics, and 0.05 IU/mL porcine follicle-stimulating hormone (FSH+) or vehicle control (CTL) medium for 22 h.

Results:

FSH withdrawal (CTL) diminished several processes associated with the acquisition of oocyte developmental competence, such as reduced cumulus cell expansion, diminished estradiol synthesis (FSH+: 116.0±0.0 pg/mL vs. CTL: 97.6±18.0 pg/mL), and lower oocyte nuclear maturation rate (FSH+: 96.47% vs. CTL: 88.76%). Fresh media formulations (i.e., TCM199 with FSH or vehicle) were indistinguishable under biochemical profiling threshold conditions. Biochemical profiling showed similar total protein and lipid concentrations between groups. Further, total sugar concentrations diminished from fresh media to their post-IVM counterparts, albeit in an FSH-independent manner. Glycogen concentrations remained unaltered after IVM within CTL media, albeit were substantially lower after IVM under FSH+ conditions.

Conclusion:

FSH mediates the consumption of serum-derived glycogen by bovine COCs during IVM and implies that serum-free media should contain increased glucose concentrations to facilitate the acquisition of oocyte developmental competence.

Transcriptome and Proteome Analysis Revealed Key Pathways Regulating Final Stage of Oocyte Maturation of the Turkey (Meleagris gallopavo)

In birds, the zona pellucida (ZP) matrix that surrounds the ovulated oocyte—called the inner perivitelline layer—is involved in sperm–zona interaction and successful fertilization. To identify the important genes and proteins connected with the final step of egg development, next-generation sequencing and two-dimensional electrophoresis, combined with mass spectrometry, were used for the analysis of mature oocytes at the F1 developmental stage. A total of 8161 genes and 228 proteins were annotated. Six subfamilies of genes, with codes ZP, ZP1–4, ZPD, and ZPAX, were identified, with the dominant expression of ZPD. The main expression site for ZP1 was the liver; however, granulosa cells may also participate in local ZP1 secretion. A ubiquitination system was identified in mature oocytes, where ZP1 was found to be the main ubiquitinated protein. Analysis of transcripts classified in estrogen receptor (ESR) signaling indicated the presence of ESR1 and ESR2, as well as a set of estrogen-dependent genes involved in both genomic and nongenomic mechanisms for the regulation of gene expression by estrogen. Oxidative phosphorylation was found to be a possible source of adenosine triphosphate, and the nuclear factor erythroid 2-related factor 2 signaling pathway could be involved in the response against oxidative stress. Oocyte–granulosa cell communication by tight, adherens, and gap junctions seems to be essential for the final step of oocyte maturation.

Oocyte Competence Biomarkers Associated With Oocyte Maturation: A Review

Oocyte developmental competence is one of the determining factors that influence the outcomes of an IVF cycle regarding the ability of a female gamete to reach maturation, be fertilized, and uphold an embryonic development up until the blastocyst stage. The current approach of assessing the competency of an oocyte is confined to an ambiguous and subjective oocyte morphological evaluation. Over the years, a myriad of biomarkers in the cumulus-oocyte-complex has been identified that could potentially function as molecular predictors for IVF program prognosis. This review aims to describe the predictive significance of several cumulus-oocyte complex (COC) biomarkers in evaluating oocyte developmental competence. A total of eight acclaimed cumulus biomarkers are examined in the study. RT-PCR and microarray analysis were extensively used to assess the significance of these biomarkers in foreseeing oocyte developmental competence. Notably, these biomarkers regulate vital processes associated with oocyte maturation and were found to be differentially expressed in COC encapsulating oocytes of different maturity. The biomarkers were reviewed according to the respective oocyte maturation events namely: nuclear maturation, apoptosis, and extracellular matrix remodeling, and steroid metabolism. Although substantial in vitro evidence was presented to justify the potential use of cumulus biomarkers in predicting oocyte competency and IVF outcomes, the feasibility of assessing these biomarkers as an add-on prognostic procedure in IVF is still restricted due to study challenges.

Integrated Analysis of Transcriptome and Histone Modifications in Granulosa Cells During Ovulation in Female Mice

The ovulatory luteinizing hormone (LH) surge induces rapid changes of gene expression and cellular functions in granulosa cells (GCs) undergoing luteinization. However, it remains unclear how the changes in genome-wide gene expression are regulated. H3K4me3 histone modifications are involved in the rapid alteration of gene expression. In this study, we investigated genome-wide changes of transcriptome and H3K4me3 status in mouse GCs undergoing luteinization. GCs were obtained from mice treated with equine chorionic gonadotropin (hCG) before, 4 hours, and 12 hours after human chorionic gonadotropin injection. RNA-sequencing identified a number of upregulated and downregulated genes, which could be classified into 8 patterns according to the time-course changes of gene expression. Many genes were transiently upregulated or downregulated at 4 hours after hCG stimulation. Gene Ontology terms associated with these genes included steroidogenesis, ovulation, cumulus-oocyte complex (COC) expansion, angiogenesis, immune system, reactive oxygen species (ROS) metabolism, inflammatory response, metabolism, and autophagy. The cellular functions of DNA repair and cell growth were newly identified as being activated during ovulation. Chromatin immunoprecipitation-sequencing revealed a genome-wide and rapid change in H3K4me3 during ovulation. Integration of transcriptome and H3K4me3 data identified many H3K4me3-associated genes that are involved in steroidogenesis, ovulation, COC expansion, angiogenesis, inflammatory response, immune system, ROS metabolism, lipid and glucose metabolism, autophagy, and regulation of cell size. The present results suggest that genome-wide changes in H3K4me3 after the LH surge are associated with rapid changes in gene expression in GCs, which enables GCs to acquire a lot of cellular functions within a short time that are required for ovulation and luteinization.

Nickel sulfate exposure induces ovarian inflammation and fibrosis and decreases oocyte quality in mice

Nickel is a heavy metal element extensively distributed in the environment and widely used in modern life. Divalent nickel is one of the most widespread forms of nickel and has been reported as toxic to various tissues. However, whether exposure to divalent nickel negatively affects ovarian homeostasis and oocyte quality remains unclear. In this study, we found that 3 weeks of nickel sulfate exposure affected body growth and decreased the weight and coefficient of the ovary, and increased atretic follicles exhibiting enhanced apoptosis in granulosa cells. Further studies have found that nickel sulfate triggered ovarian fibrosis and inflammation via transforming growth factor-β1 and nuclear factor-κB pathways, and reduced oocyte development ability. In addition, nickel sulfate increased the level of reactive oxygen species, which induced DNA damage and early apoptosis. Moreover, it was found that nickel sulfate caused damage to the mitochondria showing aberrant morphology, distribution and membrane potential while decreased levels of histone methylation. To summarize, our results indicated that nickel sulfate exposure triggered ovarian fibrosis and inflammation and caused structural and functional disorders of mitochondria in oocytes, which consequently disturbed ovarian homeostasis and follicle development and decreased oocyte quality.

The m6A mRNA demethylase FTO in granulosa cells retards FOS-dependent ovarian aging

Multifunctional N6-methyladenosine (m6A) has been revealed to be an important epigenetic component in various physiological and pathological processes, but its role in female ovarian aging remains unclear. Thus, we demonstrated m6A demethylase FTO downregulation and the ensuing increased m6A in granulosa cells (GCs) of human aged ovaries, while FTO-knockdown GCs showed faster aging-related phenotypes mediated. Using the m6A-RNA-sequence technique (m6A-seq), increased m6A was found in the FOS-mRNA-3'UTR, which is suggested to be an erasing target of FTO that slows the degradation of FOS-mRNA to upregulate FOS expression in GCs, eventually resulting in GC-mediated ovarian aging. FTO acts as a senescence-retarding protein via m6A, and FOS knockdown significantly alleviates the aging of FTO-knockdown GCs. Altogether, the abovementioned results indicate that FTO in GCs retards FOS-dependent ovarian aging, which is a potential diagnostic and therapeutic target against ovarian aging and age-related reproductive diseases.

A platform utilizing Drosophila ovulation for nonhormonal contraceptive screening

A significant unmet need for new contraceptive options for both women and men remains due to side-effect profiles, medical concerns, and the inconvenience of many currently available contraceptive products. Unfortunately, the development of novel nonsteroidal female contraceptive medicine has been stalled in the last couple of decades due to the lack of effective screening platforms. Drosophila utilizes conserved signaling pathways for follicle rupture, a final step in ovulation that is essential for female reproduction. Therefore, we explored the potential to use Drosophila as a model to screen compounds that could inhibit follicle rupture and be nonsteroidal contraceptive candidates. Using our ex vivo follicle rupture assay, we screened 1,172 Food and Drug Administration (FDA)-approved drugs and identified six drugs that could inhibit Drosophila follicle rupture in a dose-dependent manner. In addition, we characterized the molecular actions of these drugs in the inhibition of adrenergic signaling and follicle rupture. Furthermore, we validated that three of the four drugs consistently inhibited mouse follicle rupture in vitro and that two of them did not affect progesterone production. Finally, we showed that chlorpromazine, one of the candidate drugs, can significantly inhibit mouse follicle rupture in vivo. Our work suggests that Drosophila ovulation is a valuable platform for identifying lead compounds for nonsteroidal contraceptive development and highlights the potential of these FDA-approved drugs as novel nonsteroidal contraceptive agents.

Glucocorticoids, Stress and Delta-9 Tetrahydrocannabinol (THC) during Early Embryonic Development

Elevated molecular stress in women is known to have negative impacts on the reproductive development of oocytes and the embryos prior to implantation. In recent years, the prevalence of cannabis use among women of reproductive age has risen due to its ability to relieve psychological stress and nausea, which are mediated by its psychoactive component, ∆-9-tetrahydrocannabinol (THC). Although cannabis is the most popular recreational drug of the 21st century, much is unknown about its influence on molecular stress in reproductive tissues. The current literature has demonstrated that THC causes dose- and time-dependent alterations in glucocorticoid signaling, which have the potential to compromise morphology, development, and quality of oocytes and embryos. However, there are inconsistencies across studies regarding the mechanisms for THC-dependent changes in stress hormones and how either compounds may drive or arrest development. Factors such as variability between animal models, physiologically relevant doses, and undiscovered downstream gene targets of both glucocorticoids and THC could account for such inconsistencies. This review evaluates the results of studies which have investigated the effects of glucocorticoids on reproductive development and how THC may alter stress signaling in relevant tissues.

Sex Maintenance in Mammals

The crucial event in mammalian sexual differentiation occurs at the embryonic stage of sex determination, when the bipotential gonads differentiate as either testes or ovaries, according to the sex chromosome constitution of the embryo, XY or XX, respectively. Once differentiated, testes produce sexual hormones that induce the subsequent differentiation of the male reproductive tract. On the other hand, the lack of masculinizing hormones in XX embryos permits the formation of the female reproductive tract. It was long assumed that once the gonad is differentiated, this developmental decision is irreversible. However, several findings in the last decade have shown that this is not the case and that a continuous sex maintenance is needed. Deletion of Foxl2 in the adult ovary lead to ovary-to-testis transdifferentiation and deletion of either Dmrt1 or Sox9/Sox8 in the adult testis induces the opposite process. In both cases, mutant gonads were genetically reprogrammed, showing that both the male program in ovaries and the female program in testes must be actively repressed throughout the individual's life. In addition to these transcription factors, other genes and molecular pathways have also been shown to be involved in this antagonism. The aim of this review is to provide an overview of the genetic basis of sex maintenance once the gonad is already differentiated.

Systematic Analysis of Long Noncoding RNA and mRNA in Granulosa Cells during the Hen Ovulatory Cycle

Simple Summary

Chicken is one of the most economically important farm poultry, and providing many food products, such as meat and eggs for human consumption. However, follicle transcriptome studies in chickens with timepoints relating to changes in luteinizing hormone level remain unknown. In this study, the largest preovulatory follicle of chicken underwent the early, middle, and terminal stages of ovulatory cycle. Our work provides a comprehensive analysis of lncRNAs and mRNAs in chicken granulosa cells during the ovulatory cycle. A total of 12,479 mRNAs and 7528 lncRNAs were identified among the three stages. Thousands of lncRNAs were annotated, and the most differentially abundant genes were detected in the luteinizing hormone surge stage. Functional features of the lncRNAs and mRNAs at each stage were revealed, which was also associated with the changes in serum luteinizing hormone level. Especially, genes related to oxidative stress, steroids regulation, and inflammatory process were enriched in the luteinizing hormone surge stage, The comprehensive data generated in this study provides the foundation for future investigations to improve the reproductive performance of chickens and explore the mechanisms responsible for female ovarian diseases.

Abstract

Long non-coding RNAs (lncRNAs) and mRNAs are temporally expressed during chicken follicle development. However, follicle transcriptome studies in chickens with timepoints relating to changes in luteinizing hormone (LH) levels are rare. In this study, gene expression in Rohman layers was investigated at three distinct stages of the ovulatory cycle: zeitgeber time 0 (ZT0, 9:00 a.m.), zeitgeber time 12 (ZT12, 9:00 p.m.), and zeitgeber time 20 (ZT20, 5:00 a.m.) representing the early, middle, and LH surge stages, respectively, of the ovulatory cycle. Gene expression profiles were explored during follicle development at ZT0, ZT12, and ZT20 using Ribo-Zero RNA sequencing. The three stages were separated into two major stages, including the pre-LH surge and the LH surge stages. A total of 12,479 mRNAs and 7528 lncRNAs were identified among the three stages, and 4531, 523 differentially expressed genes (DEGs) and 2367, 211 differentially expressed lncRNAs (DELs) were identified in the ZT20 vs. ZT12, and ZT12 vs. ZT0, comparisons. Functional enrichment analysis revealed that genes involved in cell proliferation and metabolism processes (lipid-related) were mainly enriched in the ZT0 and ZT12 stages, respectively, and genes related to oxidative stress, steroids regulation, and inflammatory process were enriched in the ZT20 stage. These findings provide the basis for further investigation of the specific genetic and molecular functions of follicle development in chickens.

Cionin, a vertebrate cholecystokinin/gastrin homolog, induces ovulation in the ascidian Ciona intestinalis type A

Cionin is a homolog of vertebrate cholecystokinin/gastrin that has been identified in the ascidian Ciona intestinalis type A. The phylogenetic position of ascidians as the closest living relatives of vertebrates suggests that cionin can provide clues to the evolution of endocrine/neuroendocrine systems throughout chordates. Here, we show the biological role of cionin in the regulation of ovulation. In situ hybridization demonstrated that the mRNA of the cionin receptor, Cior2, was expressed specifically in the inner follicular cells of pre-ovulatory follicles in the Ciona ovary. Cionin was found to significantly stimulate ovulation after 24-h incubation. Transcriptome and subsequent Real-time PCR analyses confirmed that the expression levels of receptor tyrosine kinase (RTK) signaling genes and a matrix metalloproteinase (MMP) gene were significantly elevated in the cionin-treated follicles. Of particular interest is that an RTK inhibitor and MMP inhibitor markedly suppressed the stimulatory effect of cionin on ovulation. Furthermore, inhibition of RTK signaling reduced the MMP gene expression in the cionin-treated follicles. These results provide evidence that cionin induces ovulation by stimulating MMP gene expression via the RTK signaling pathway. This is the first report on the endogenous roles of cionin and the induction of ovulation by cholecystokinin/gastrin family peptides in an organism.

Triggering change in stimulation protocols: a matter of oocyte maturation and beyond

Since the birth of Louise Brown, in vitro fertilization (IVF) stimulation protocols have evolved significantly. One particular area of focus has been the process of final oocyte maturation, during which the oocyte gains competence to support fertilization and early embryonic development up to implantation. The field of human assisted reproductive technology (ART) is witnessing increased utilization of GnRH agonists (GnRHa) as trigger agents, in addition to or instead of the traditionally used human chorionic gonadotropin (hCG). Future translational studies will reveal whether oocyte developmental competence, as reflected in live birth outcomes, are not only non-inferior, but also superior with the use of GnRHa as a trigger for both nuclear and cytoplasmic oocyte maturation.

Expression of tissue factor and tissue factor pathway inhibitors during ovulation in rats: a relevance to the ovarian hyperstimulation syndrome

BACKGROUND

Blood coagulation has been associated with ovulation and female infertility. In this study, the expression of the tissue factor system was examined during ovulation in immature rats; the correlation between tissue factor and ovarian hyperstimulation syndrome (OHSS) was evaluated both in rats and human follicular fluids.

METHODS

Ovaries were obtained at various times after human chorionic gonadotropin (hCG) injection to investigate the expression of tissue factor system. Expression levels of ovarian tissue factor, tissue factor pathway inhibitor (Tfpi)-1 and Tfpi-2 genes and proteins were determined by real-time quantitative polymerase chain reaction (qPCR), and Western blot and immunofluorescence analyses, respectively. Expression levels of tissue factor system were also investigated in ovaries of OHSS-induced rats and in follicular fluid of infertile women.

RESULTS

The expression of tissue factor in the preovulatory follicles was stimulated by hCG, reaching a maximum at 6 h. Tissue factor was expressed in the oocytes and the preovulatory follicles. Tfpi-2 mRNA levels were mainly increased by hCG in the granulosa cells whereas the mRNA levels of Tfpi-1 were decreased by hCG. Human CG-stimulated tissue factor expression was inhibited by the progesterone receptor antagonist. The increase in Tfpi-2 expression by hCG was decreased by the proliferator-activated receptor γ (PPARγ) antagonist. Decreased expression of the tissue factor was detected in OHSS-induced rats. Interestingly, the tissue factor concentrations in the follicular fluids of women undergoing in vitro fertilization were correlated with pregnancy but not with OHSS.

CONCLUSIONS

Collectively, the results indicate that tissue factor and Tfpi-2 expression is stimulated during the ovulatory process in rats; moreover, a correlation exists between the levels of tissue factor and OHSS in rats but not in humans.

Neurotensin: A novel mediator of ovulation?

The midcycle luteinizing hormone (LH) surge initiates a cascade of events within the ovarian follicle which culminates in ovulation. Only mural granulosa cells and theca cells express large numbers of LH receptors, and LH-stimulated paracrine mediators communicate the ovulatory signal within the follicle. Recent reports identified the neuropeptide neurotensin (NTS) as a product of granulosa cells. Here, we demonstrate that granulosa cells were the primary site of NTS expression in macaque ovulatory follicles. Granulosa cell NTS mRNA and protein increased after human chorionic gonadotropin (hCG) administration, which substitutes for the LH surge. To identify ovulatory actions of NTS, a NTS-neutralizing antibody was injected into preovulatory macaque follicles. hCG administration immediately followed, and ovaries were removed 48 hours later to evaluate ovulatory events. Follicles injected with control IgG ovulated normally. In contrast, 75% of NTS antibody-injected follicles failed to ovulate, containing oocytes trapped within unruptured, hemorrhagic follicles. Serum progesterone was unchanged. Of the three NTS receptors, SORT1 was highly expressed in follicular granulosa, theca, and endothelial cells; NTSR1 and NTSR2 were expressed at lower levels. Excessive blood cells in NTS antibody-injected follicles indicated vascular anomalies, so the response of monkey ovarian endothelial cells to NTS was evaluated in vitro. NTS stimulated endothelial cell migration and capillary sprout formation, consistent with a role for NTS in vascular remodeling associated with ovulation. In summary, we identified NTS as a possible paracrine mediator of ovulation. Further investigation of the NTS synthesis/response pathway may lead to improved treatments for infertility and novel targets for contraception.

Metabolomics analysis of follicular fluid coupled with oocyte aspiration reveals importance of glucocorticoids in primate periovulatory follicle competency

Gonadotropin administration during infertility treatment stimulates the growth and development of multiple ovarian follicles, yielding heterogeneous oocytes with variable capacity for fertilization, cleavage, and blastocyst formation. To determine how the intrafollicular environment affects oocyte competency, 74 individual rhesus macaque follicles were aspirated and the corresponding oocytes classified as failed to cleave, cleaved but arrested prior to blastulation, or those that formed blastocysts following in vitro fertilization. Metabolomics analysis of the follicular fluid (FF) identified 60 unique metabolites that were significantly different between embryo classifications, of which a notable increase in the intrafollicular ratio of cortisol to cortisone was observed in the blastocyst group. Immunolocalization of the glucocorticoid receptor (GR, NR3C1) revealed translocation from the cytoplasm to nucleus with oocyte maturation in vitro and, correlation to intrafollicular expression of the 11-hydroxy steroid dehydrogenases that interconvert these glucocorticoids was detected upon an ovulatory stimulus in vivo. While NR3C1 knockdown in oocytes had no effect on their maturation or fertilization, expansion of the associated cumulus granulosa cells was inhibited. Our findings indicate an important role for NR3C1 in the regulation of follicular processes via paracrine signaling. Further studies are required to define the means through which the FF cortisol:cortisone ratio determines oocyte competency.

Reversing complete mechanical transzonal projections disruption during mouse in vitro follicle culture with unaltered oocyte competence†

In vitro oocyte growth is widely studied as an alternative fertility preservation approach. Several animal models are used to generate extensive information on this complex process regulated by the constant and dynamic interaction between the oocyte and its somatic compartment throughout follicle growth and maturation. A two-dimensional attachment mouse secondary follicle culture system was used to assess the oocyte's capacity to overcome disconnection from its somatic companions at different developmental stages for final competence acquisition. To test this, complete mechanical denudation of oocytes from preantral (PA) and early antral (EA) follicles was performed. Established endpoints were the oocyte's potential to reconnect with somatic cells and the impact of connectivity disruption on mature oocyte quality. This study proves that oocytes from PA and EA cultured mouse follicles can overcome complete denudation, restoring likely functional transzonal projections with no significant differences in meiotic and developmental competence compared with those from intact cultured follicles. These novel findings constitute good premises for developing successful strategies to rescue human oocyte competence in the context of in vitro culture approaches such as nonhuman chorionic gonadotropin triggered in vitro maturation.

Short-term Western-style diet negatively impacts reproductive outcomes in primates

A maternal Western-style diet (WSD) is associated with poor reproductive outcomes, but whether this is from the diet itself or underlying metabolic dysfunction is unknown. Here, we performed a longitudinal study using regularly cycling female rhesus macaques (n = 10) that underwent 2 consecutive in vitro fertilization (IVF) cycles, one while consuming a low-fat diet and another 6–8 months after consuming a high-fat WSD. Metabolic data were collected from the females prior to each IVF cycle. Follicular fluid (FF) and oocytes were assessed for cytokine/steroid levels and IVF potential, respectively. Although transition to a WSD led to weight gain and increased body fat, no difference in insulin levels was observed. A significant decrease in IL-1RA concentration and the ratio of cortisol/cortisone was detected in FF after WSD intake. Despite an increased probability of isolating mature oocytes, a 44% reduction in blastocyst number was observed with WSD consumption, and time-lapse imaging revealed delayed mitotic timing and multipolar divisions. RNA sequencing of blastocysts demonstrated dysregulation of genes involved in RNA binding, protein channel activity, mitochondrial function and pluripotency versus cell differentiation after WSD consumption. Thus, short-term WSD consumption promotes a proinflammatory intrafollicular microenvironment that is associated with impaired preimplantation development in the absence of large-scale metabolic changes.

Insufficient Cumulus Expansion and Poor Oocyte Retrieval in Endometriosis-Related Infertile Women

Endometriosis (EMs) is a common cause for female infertility, leading to the need for in vitro fertilization (IVF). In clinics, we found the operative oocyte retrieval to be more or less difficult in women with EMs. We hypothesized that EMs may be involved in the insufficient cumulus expansion that partially explained the lower oocyte retrieval in EMs-related infertile women undergoing assisted reproductive technology (ART). To explore whether the insufficient cumulus expansion exists in EMs-related infertile women and whether there is a possible relationship between the insufficient cumulus expansion and the clinical phenomenon of difficulty in oocyte retrieval. Those infertile women undergoing IVF recorded in our database between January 2013 and October 2017 were included. The expression levels of cumulus expansion-related genes (HAS2/PTGS2/PTX3/TNFAIP6) in the cumulus cells (CCs) from 19 infertile women with EMs and 24 controls were analyzed by real-time PCR. After that, 635 women with EMs-associated infertility (the EMs group) and 4634 women with male factor-associated infertility (the control group) were included in the retrospective analysis. The clinical outcomes were compared between the two groups. The relative mRNA levels of cumulus expansion-related genes were significantly decreased in the CCs from those infertile women with EMs when compared to the control group (all p < 0.05), especially the expression of PTGS2. The mean oocyte retrieval rates (proportion of obtained oocytes in punctured follicles) were (76.33 ± 2.58)% and (71.80 ± 0.58)% (p < 0.01). The mean numbers of flushing times per follicle were 1.11 ± 0.65 and 3.86 ± 1.53 (p < 0.001). The lower expression of cumulus expansion-related genes in CCs suggests the insufficient cumulus expansion in EMs-related infertile women, which partially explains a possible mechanism related to poor oocyte retrieval.

The Emerging Roles and Therapeutic Potential of Extracellular Vesicles in Infertility

Infertility is becoming much more common and affects more couples. The past years witnessed the rapid development of the diagnosis and treatment upon infertility, which give numerous coupled more opportunities become parents. Extracellular vesicles are known as nano-sized membrane vesicles to play a major role in intracellular communication. In recent years, several basic and clinical studies have tried to investigate the correlation between the reproductive health/disorder and extracellular vesicles. However, the mechanism is still unclear. In this review, we reviewed the relationship between reproductive physiology and extracellular vesicles, and then collectively focused on the recent findings on the relationship between extracellular and infertility, and its consequent influence on the novel insight regarding the therapeutic strategies for infertility in the future clinical practice.

Dissection of the Ovulatory Process Using ex vivo Approaches

Ovulation is a unique physiological phenomenon that is essential for sexual reproduction. It refers to the entire process of ovarian follicle responses to hormonal stimulation resulting in the release of mature fertilization-competent oocytes from the follicles and ovaries. Remarkably, ovulation in different species can be reproduced out-of-body with high fidelity. Moreover, most of the molecular mechanisms and signaling pathways engaged in this process have been delineated using in vitro ovulation models. Here, we provide an overview of the major molecular and cytological events of ovulation observed in frogs, primarily in the African clawed frog Xenopus laevis, using mainly ex vivo approaches, with the focus on meiotic oocyte maturation and follicle rupture. For the purpose of comparison and generalization, we also refer extensively to ovulation in other biological species, most notoriously, in mammals.

Nuclear receptors: Key regulators of somatic cell functions in the ovulatory process

The development of the ovarian follicle to its culmination by ovulation is an essential element of fertility. The final stages of ovarian follicular growth are characterized by granulosa cell proliferation and differentiation, and steroid synthesis under the influence of follicle-stimulating hormone (FSH). The result is a population of granulosa cells poised to respond to the ovulatory surge of luteinizing hormone (LH). Members of the nuclear receptor superfamily of transcription factors play indispensable roles in the regulation of these events. The key regulators of the final stages of follicular growth that precede ovulation from this family include the estrogen receptor beta (ESR2) and the androgen receptor (AR), with additional roles for others, including steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1). Following the LH surge, the mural and cumulus granulosa cells undergo rapid changes that result in expansion of the cumulus layer, and a shift in ovarian steroid hormone biosynthesis from estradiol to progesterone production. The nuclear receptor best associated with these events is LRH-1. Inadequate cumulus expansion is also observed in the absence of AR and ESR2, but not the progesterone receptor (PGR). The terminal stages of ovulation are regulated by PGR, which increases the abundance of the proteases that are directly responsible for rupture. It further regulates the prostaglandins and cytokines associated with the inflammatory-like characteristics of ovulation. LRH-1 regulates PGR, and is also a key regulator of steroidogenesis, cellular proliferation, and cellular migration, and cytoskeletal remodeling. In summary, nuclear receptors are among the panoply of transcriptional regulators with roles in ovulation, and several are necessary for normal ovarian function.

Ultradian rhythms in heart rate variability and distal body temperature anticipate onset of the luteinizing hormone surge

The menstrual cycle is characterized by predictable patterns of physiological change across timescales. Although patterns of reproductive hormones across the menstrual cycle, particularly ultradian rhythms, are well described, monitoring these measures repeatedly to predict the preovulatory luteinizing hormone (LH) surge is not practical. In the present study, we explored whether non-invasive measures coupled to the reproductive system: high frequency distal body temperature (DBT), sleeping heart rate (HR), sleeping heart rate variability (HRV), and sleep timing, could be used to anticipate the preovulatory LH surge in women. To test this possibility, we used signal processing to examine these measures in 45 premenopausal and 10 perimenopausal cycles alongside dates of supra-surge threshold LH and menstruation. Additionally, urinary estradiol and progesterone metabolites were measured daily surrounding the LH surge in 20 cycles. Wavelet analysis revealed a consistent pattern of DBT and HRV ultradian rhythm (2-5 h) power that uniquely enabled anticipation of the LH surge at least 2 days prior to its onset in 100% of individuals. Together, the present findings reveal fluctuations in distal body temperature and heart rate variability that consistently anticipate the LH surge, suggesting that automated ultradian rhythm monitoring may provide a novel and convenient method for non-invasive fertility assessment.

Protein Cargo of Extracellular Vesicles From Bovine Follicular Fluid and Analysis of Their Origin From Different Ovarian Cells

Follicular fluid (FF) fills the interior portion of the ovarian antral follicle and provides a suitable microenvironment for the growth of the enclosed oocyte through molecular factors that originate from plasma and the secretions of follicular cells. FF contains extracellular nanovesicles (ffEVs), including 30-100-nm membrane-coated exosomes, which carry different types of RNA, proteins, and lipids and directly influence oocyte competence to develop embryo. In the present study, we aimed to characterize the protein cargo of EVs from the FF of 3-6-mm follicles and uncover the origins of ffEVs by assessing expression levels of corresponding mRNAs in bovine follicular cells and oocyte and cell proteomes. Isolated exosome-like ffEVs were 53.6 + 23.3 nm in size and could be internalized by cumulus-oocyte complex. Proteomes of ffEVs and granulosa cells (GC) were assessed using nanoflow liquid chromatography coupled with high-resolution tandem mass spectrometry after the gel fractionation of total proteins. In total, 460 protein isoforms corresponding to 322 unique proteins were identified in ffEVs; among them, 190 were also identified via GC. Gene Ontology terms related to the ribosome, protein and RNA folding, molecular transport, endocytosis, signal transduction, complement and coagulation cascades, apoptosis, and developmental biology pathways, including PI3K-Akt signaling, were significantly enriched features of ffEV proteins. FfEVs contain numerous ribosome and RNA-binding proteins, which may serve to compact different RNAs to regulate gene expression and RNA degradation, and might transfer ribosomal constituents to the oocyte. Majority of genes encoding ffEV proteins expressed at different levels in follicular cells and oocyte, corroborating with numerous proteins, which were reported in bovine oocyte and cumulus cells in other studies thus indicating possible origin of ffEV proteins. The limited abundance of several mRNAs within follicular cells indicated that corresponding ffEV proteins likely originated from circulating exosomes released by other tissues. Analysis of bovine ffEV transcriptome revealed that mRNAs present in ffEV accounted for only 18.3% of detected ffEV proteins. In conclusion, our study revealed numerous proteins within ffEVs, which originated from follicular and other cells. These proteins are likely involved in the maintenance of follicular homeostasis and may affect oocyte competence.

In Vitro Study on the Regulation of Annexin IV and VEGF by hCG in the Human Endometrium

Objective

Whether changes in vascular endothelial growth factor (VEGF) and annexin IV during implantation are regulated through the LH/hCG-R needs further research. To investigate the mechanism of hCG on the expression of annexin IV and VEGF in human endometrial cells.

Methods

Endometrial cells were isolated and identified from human specimens. The proportion of glandular and epithelial cells was analyzed. Annexin IV and VEGF were analyzed by qRT-PCR (mRNA), western blot (proteins), and immunohistochemistry (proteins). Protein location was identified by immunohistochemistry. The cells were cultured with hCG, hCG/PD98059 (a MAPK inhibitor), or no treatment (control).

Results

The proportions between the glandular epithelial cells and stromal cells at inoculation and when adding hCG were 25.8 ± 0.2% and 27.8 ± 0.04%, respectively (P > 0.05). LH/hCG-R, annexin IV, and VEGF were found in the cytoplasm of endometrial cells. After 2, 6, 12, and 24 h of hCG treatment, compared with 1 h, VEGF mRNA was increased by 1.25-fold, 3.19-fold, 4.21-fold, and 4.86-fold and annexin IV by 2.23-fold, 3.37-fold, 5.14-fold, and 5.02-fold. Compared with the control group, annexin IV mRNA and protein were increased in the hCG and hCG/PD98059 groups (mRNA/protein: 1.99-fold/1.80-fold and 2.33-fold/1.93-fold, P < 0.05). Compared with the control group, VEGF mRNA and protein were increased in the hCG group (mRNA/protein: 2.30-fold/1.86-fold), but not in the hCG/PD98059 group.

Conclusion

hCG could upregulate the mRNA and protein expression of annexin IV and VEGF. The upregulation of annexin IV by hCG could not be inhibited by PD98059, but the upregulation of VEGF by hCG could.

The relationship between a novel evaluation parameter of premature luteinization and IVF outcomes

RESEARCH QUESTION

Can premature luteinization of granulosa cells (PLGC) act as a novel parameter of premature luteinization and affect IVF outcomes?

STUDY DESIGN

In this retrospective cohort study, infertile patients undergoing fresh IVF cycles between January 2006 and December 2016 at the Reproductive Medicine Center in Tongji Hospital were included. A total of 42,468 cycles were conducted. Propensity score matching was carried out to match the baseline characteristics, and participants were assigned to the PLGC group and control group. The main outcomes were pregnancy rate and live birth rate.

RESULTS

Patient characteristics and clinical outcomes were compared before and after matching. In general, the fate of oocytes in the PLGC group was much worse than those in the control group after matching, including metaphase II rate, two-pronuclei rate, available embryo rate, blastocyst formation rate, high-quality blastocyst rate, pregnancy rate, implantation rate and live birth rate. Among those potential risk factors, gonadotrophin duration, oestradiol and progesterone on HCG day were positively associated with the occurrence of PLGC in the multivariate logistic regression model, with gonadotrophin dosage negatively related. Moreover, cumulus-oocyte complexes with PLGC showed a high correlation with elevated progesterone levels over 1.5 ng/ml.

CONCLUSIONS

Our findings demonstrated the adverse effect of PLGC on oocyte competency. In evaluating cumulus-oocyte complexes, PLGC provide an available novel parameter for premature luteinization judgement in clinical and individualized precise treatment. Close monitoring of progesterone level as well as critical analysis of progesterone elevation can reduce the occurrence of premature luteinization.

Tetraspanins, More than Markers of Extracellular Vesicles in Reproduction

The participation of extracellular vesicles in many cellular processes, including reproduction, is unquestionable. Although currently, the tetraspanin proteins found in extracellular vesicles are mostly applied as markers, increasing evidence points to their role in extracellular vesicle biogenesis, cargo selection, cell targeting, and cell uptake under both physiological and pathological conditions. In this review, we bring other insight into the involvement of tetraspanin proteins in extracellular vesicle physiology in mammalian reproduction. We provide knowledge regarding the involvement of extracellular vesicle tetraspanins in these processes in somatic cells. Furthermore, we discuss the future direction towards an understanding of their functions in the tissues and fluids of the mammalian reproductive system in gamete maturation, fertilization, and embryo development; their involvement in mutual cell contact and communication in their complexity.

Expression of ADR-α1, 2 and ADR-β2 in cumulus cell culture of infertile women with polycystic ovary syndrome and poor responder who are a candidate for IVF: the novel strategic role of clonidine in this expression

OBJECTIVE

Alpha and beta-adrenoceptors (ADR-α1, 2, and β2) play a regulatory role in the folliculogenesis and steroidogenesis in the ovarian follicles. This study aimed to measure these adrenoceptors mRNA and its protein levels in cumulus cells (CCs) culture of poor ovarian reserve (POR) and polycystic ovarian syndrome (PCOS) infertile women (IVF candidate) and the effect of clonidine treatment at CCs culture.

METHODS

This case/control study was conducted in 2017 includes a control (donation oocytes) and two studies (PCO and POR) groups. The ovulation induction drugs were prescribed in all groups. After the oocyte puncture, the follicular fluid was collected and CCs were isolated were cultured. RNA was extracted and cDNA was synthesized and designed the primer for the ADR-α1, 2 and ADR-β2 gene expression. The protein levels were investigated by Western Blot.

RESULTS

The results showed a high level of three adrenergic expressions in PCO women compared to the control group (p-value <.001), which can be reduced by clonidine. POR group showed a significant decrease in the gene expression of ADR-α1 (p-value = .004) and ADR-α2 (p-value = .003) compared to the control group and clonidine treatment had no effect.

CONCLUSION

The significant increase of three adrenoceptors gene expression and protein levels in CCs culture indicate to the hyperactivity of the ovarian sympathetic nervous system at the receptor levels in women with PCOS, and clonidine confirmed it by reducing this expression. In POR women, the reduction of ADR-α1, 2 expressions maybe lead to the aging process in the ovary.

The Role of the Epididymis and the Contribution of Epididymosomes to Mammalian Reproduction

It is well-established that testicular spermatozoa are immature and acquire motility and fertilization capabilities during transit throughout the epididymis. The epididymis is a duct-like organ that connects the testis to the vas deferens and is comprised of four anatomical regions: the initial segment, caput, corpus, and cauda. Sperm maturation occurs during epididymal transit by the interaction of sperm cells with the unique luminal environment of each epididymal region. In this review we discuss the epididymis as an essential reproductive organ responsible for sperm concentration, maturation (including sperm motility acquisition and fertilizing ability), protection and storage. Importantly, we also discuss specific characteristics and roles of epididymal-derived exosomes (epididymosomes) in establishing sperm competency within the intricate process of reproduction. This review suggests that an increasing body of evidence is working to develop a complete picture of the role of the epididymis in male reproduction, offspring health, and disease susceptibility.

Controlling chronic low-grade inflammation to improve follicle development and survival

Chronic low-grade inflammation is one cause of follicle development disturbance. Chronic inflammation exists in pathological conditions such as premature ovarian failure, physiological aging of the ovaries, and polycystic ovary syndrome. Inflammation of the whole body can affect oocytes via the follicle microenvironment, oxidative stress, and GM-CSF. Many substances without toxic side-effects extracted from natural organisms have gradually gained researchers' attention. Recently, chitosan oligosaccharide, resveratrol, anthocyanin, and melatonin have been found to contribute to an improvement in inflammation. This review discusses the interrelationships between chronic low-grade inflammation and follicle development, the underlying mechanisms, and methods that may improve follicle development by controlling the level of chronic low-grade inflammation.

TGF-β1 promotes vitamin D-induced prostaglandin E2 synthesis by upregulating vitamin D receptor expression in human granulosa-lutein cells

There is increasing evidence showing the importance of vitamin D (Vit D) and its nuclear receptor, the Vit D receptor (VDR), in female reproductive health. Transforming growth factor-β1 (TGF-β1) and its functional receptors are expressed in human oocytes and granulosa cells that participate in follicular development and ovulation. Recently, Sma- and Mad-related protein 3 (SMAD3; a downstream effector of TGF-β1) has been proposed to mediate crosstalk between the Vit D and TGF-β1 signaling pathways, but this relationship has not been fully explored and has yet to be tested in human granulosa-lutein (hGL) cells. In this study, we showed that TGF-β1 significantly promoted the expression of VDR, and this stimulatory effect occurred through the activin receptor-like kinase 5 type I receptor-mediated SMAD3 and ERK1/2 signaling pathways in hGL cells. Additionally, we showed that Vit D increased the expression of cyclooxygenase 2 (COX-2) and the synthesis of prostaglandin E2 (PGE2) in a time- and dose-dependent manner. Furthermore, we demonstrated a synergistic effect of TGF-β1 and Vit D on the expression of COX-2 and synthesis of PGE2, and this effect could be attenuated by silencing the expression of VDR. Our findings indicate that TGF-β1 upregulates the expression of VDR, which promotes Vit D-induced COX-2 expression and subsequent PGE2 production by activating the SMAD3 and ERK1/2 signaling pathways in hGL cells.

Chromosome Missegregation in Single Human Oocytes Is Related to the Age and Gene Expression Profile

The growing trend for women to postpone childbearing has resulted in a dramatic increase in the incidence of aneuploid pregnancies. Despite the importance to human reproductive health, the events precipitating female age-related meiotic errors are poorly understood. To gain new insight into the molecular basis of age-related chromosome missegregation in human oocytes, we combined the transcriptome profiles of twenty single oocytes (derived from females divided into two groups according to age <35 and ≥35 years) with their chromosome status obtained by array comparative genomic hybridization (aCGH). Furthermore, we compared the transcription profile of the single oocyte with the surrounding cumulus cells (CCs). RNA-seq data showed differences in gene expression between young and old oocytes. Dysregulated genes play a role in important biological processes such as gene transcription regulation, cytoskeleton organization, pathways related to RNA maturation and translation. The comparison of the transcription profile of the oocyte and the corresponding CCs highlighted the differential expression of genes belonging to the G protein-coupled receptor superfamily. Finally, we detected the loss of a X chromosome in two oocytes derived from women belonging to the ≥35 years age group. These aneuploidies may be caused by the detriment of REEP4, an endoplasmic reticulum protein, in women aged ≥35 years. Here we gained new insight into the complex regulatory circuit between the oocyte and the surrounding CCs and uncovered a new putative molecular basis of age-related chromosome missegregation in human oocytes.

Bushen Tiaojing (II and III) Decoctions Activate MAPK14 and MAPK3/1 to Promote the Expression of Cumulus Expansion-Related Factors in Mice

Background

Bushen Tiaojing Decoctions (BSTJ-II-D and BSTJ-III-D) are used to assist pregnancy in clinical practice. In this study, we explored the ability of sequential administration of BSTJ-II-D and BSTJ-III-D to promote cumulus cell (CC) expansion and its underlying mechanisms in controlled ovarian hyperstimulation (COH) mice.

Methods

Kunming mice were randomly divided into three groups. The normal group was injected intraperitoneally with saline, and distilled water was administered orally by gavage. As the COH model, mice were injected with GnRHa, eCG, and hCG. Subsequently, the BSTJD group received BSTJ-II-D and BSTJ-III-D orally by gavage, while the control group received distilled water. We evaluated CC expansion and oocyte first polar body (PB1) extrusion under a stereomicroscope. Serum levels of follicle-stimulating hormone (FSH) were detected by radioimmunoassay. The expression of the CC expansion-related factors PTX3 and PTGS2 was detected by immunofluorescence, western blot, and quantitative real-time-polymerase chain reaction analyses (qRT-PCR). Expression of p-MAPK14, p-MAPK3/1, MAPK14, and MAPK3/1 was detected by western blot analysis.

Results

Sequential administration of BSTJ-II-D and BSTJ-III-D promoted cumulus expansion and oocyte PB1 extrusion and upregulated PTX3 and PTGS2 expression at the mRNA and protein levels. Furthermore, the levels of p-MAPK14/MAPK14, p-MAPK3/1/MAPK3/1 proteins, and serum FSH in the BSTJD group were higher than those in the normal and control groups.

Conclusions

Sequential administration of BSTJ-II-D and BSTJ-III-D promotes cumulus expansion and oocyte maturation in COH mice by increasing FSH expression and activating the MAPK14 and MAPK3/1 signalling pathways, thereby increasing expression of PTX3 and PTGS2.

Interleukins' expression profile changes in granulosa cells of preovulatory follicles during the postpartum period in dairy cows

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Interleukin (IL) 4 expression was significantly altered during the postpartum period.

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IL8 and IL15 were the most significantly induced during the postpartum period.

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Correlation between increased BHB levels and induction of proinflammatory cytokines.

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Interleukins analyzed were differentially regulated during follicular development.

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ILs induced during the post-partum period were also induced 24 h post-hCG injection.

The postpartum period in dairy cows is associated with a state of temporary negative energy balance and could induce functional changes into ovarian granulosa cells (GC) resulting in significant impact on the ovarian function and fertility. Yet, the regulation of interleukin receptors (ILRs) in GC as well as ILs expression profile during the postpartum period have not been fully investigated. We hypothesized that the postpartum period is associated with changes in ILs expression profile that could affect follicular development and ovulation rate. First, we aimed to investigate the expression and regulation of different IL and IL receptors in GC at different stages of follicular development and then analyse the changes in target ILs expression profile induced during the postpartum period. In the first objective, normal cycling cows were selected and GC were collected from small follicles (SF), dominant follicles at day 5 of the estrous cycle (DF), and ovulatory follicles, 24 h following hCG injection (OF). In the second objective, dairy cows between 50 and 70 days postpartum were randomly selected, and β-hydroxybutyrate (BHB) concentrations were measured in blood samples in order to assign cows to the BHB⁺ group (>1.4 mmol/L) or BHB⁻ group (<1.2 mmol/L). GC were collected from preovulatory follicles by transvaginal aspiration. Total RNA was extracted from GC of all groups for analysis of target ILs and ILRs expression. Steady-state mRNA levels of IL4R was strongest in the DF, while IL15R expression was greatest in the OF, and IL21R showed increased steady-state mRNA levels in the corpus luteum as compared to the different groups of follicles. Overall, expression of IL1A, IL1B, IL8, IL15, IL23 and TNFα was stronger in OF as compared to DF, while IL4 and IL10 expression was stronger in SF than in DF. Similarly, expression of IL1A, IL1B, IL8, IL15, IL23, and TNFα were significantly stronger in GC of BHB⁺ cows than in the control, while IL4 expression was significantly reduced in BHB⁺ as compared to control cows. We have established an IL expression profile, which suggest a correlation with BHB levels during the postpartum period. Additionally, we have demonstrated a differential regulation of target ILRs in GC at different stages of follicular development. Overall, these data provide a better understanding of the changes that could affect follicular development and ovulation during the postpartum period and lay the ground for further investigations.

Expression and Contribution of NLRP3 Inflammasome During the Follicular Development Induced by PMSG

Follicular development and following ovulation induced by luteinizing hormone (LH) surge are critical for ovarian functions, but the molecular mechanism regulating ovarian ovulation attracts more attention and remains mainly unknown. Recent researches on the nucleotide leukin rich polypeptide 3 (NLRP3) inflammasome shred light on it. Given pregnant mare serum gonadotropin (PMSG) can not only trigger the follicular development, but also induce the following ovulation, the present study therefore examined that expression and localization of NLRP3 inflammasome through immunohistochemistry and Western blotting during the follicular development induced by PMSG. The results showed expressions of NLRP3 and the adaptor protein apoptosis-associated speck-like protein (ASC) significantly increased in the outside of intrafollicular fluid, further analysis found that caspase-1 was activated and IL-1β production was also upregulated after 52 h-treatment of PMSG. Furthermore, a significant increase of ovulation-related genes, hypoxia inducible factor (HIF)-1α and endothelin (ET)-1, was found after 52 h-treatment of PMSG. To our knowledge, it is the first time to clearly indicated the activation of NLRP3 inflammasome may contribute to the ovulation of PMSG-treated ovaries, which will help to further clarify the ovulatory mechanism in mammals.

Downregulation of homeodomain protein Cut is essential for Drosophila follicle maturation and ovulation

Proper development and maturation of a follicle is essential for successful ovulation and reproduction; however, the molecular mechanisms for follicle maturation, particularly for somatic follicle cell differentiation, are poorly understood. During Drosophila oogenesis, the somatic follicle cells encasing oocytes undergo two distinct well-established transitions: the mitotic to endocycle switch at stage 6/7 and the endocycle to gene amplification switch at stage10A/10B. Here, we identify a novel third follicle cell transition that occurs in the final stages of oogenesis (stage 13/14). This late follicle cell transition is characterized by upregulation of the transcription factor Hindsight (Hnt), and downregulation of the homeodomain transcription factor Cut and the zinc-finger transcription factor Tramtrack-69 (Ttk69). We demonstrate that inducing expression of Cut in stage 14 follicle cells is sufficient to inhibit follicle rupture and ovulation through its negative regulation of Hnt and promotion of Ttk69 expression. Our work illustrates the importance of the stage13/14 transition for follicle maturation and demonstrates the complex regulation required for somatic follicle cells to differentiate into a state primed for follicle rupture and ovulation.