Metabolic co-dependence of the oocyte and cumulus cells: essential role in determining oocyte developmental competence

Mogroside III improves bovine oocyte in vitro maturation by regulating autophagy in cumulus cells

In vitro maturation (IVM) of oocytes is pivotal for successful embryo production. Cumulus cells (CCs) contribute to oocyte maturation through the secretion of hormones and nutrients, with proper autophagic activity being crucial for this process. However, the role of autophagy in CCs remains underexplored. Siraitia grosvenorii extract Mogroside III (MIII), known for its antioxidant properties, has yet to be extensively studied for its impact on bovine oocyte IVM and its potential regulatory effects on autophagy. This study assessed the influence of MIII on autophagic activity in CCs and its subsequent effects on oocyte developmental potential. The results demonstrated that MIII enhanced bovine oocyte IVM, promoted CC expansion, and supported embryonic development. Transcriptomic analysis indicated that MIII upregulated the expression of autophagy-related genes. In vitro experiments on CCs revealed that MIII increased LC3B protein levels, reduced SQSTM1 accumulation, and upregulated the gene expression of LC3, Beclin1, and ATG5. In co-culture systems, autophagy inhibition in CCs impaired oocyte IVM and embryonic development, but MIII alleviated these effects, restoring oocyte developmental capacity compromised by 3-MA-induced autophagy inhibition. Mechanistically, MIII facilitated the degradation of WT1 by upregulating LC3B, influencing CC differentiation, enhancing FSHR synthesis, and increasing estrogen and progesterone secretion. In conclusion, MIII enhances oocyte developmental potential by modulating autophagy in CCs.

Effect of IVM media supplementation with a blend of n6/n3 fatty acids on the quality of bovine oocytes and blastocysts

Optimizing in vitro maturation (IVM) media can enhance blastocyst yield and quality. This study explores the effects of supplementing IVM medium with a blend of two essential polyunsaturated fatty acids (LA and ALA) at a ratio observed in the serum of experimental heifers on the quality of bovine oocytes, cumulus cells (CC), and blastocysts. The in vitro embryo production protocol was based on commercial media (Bioscience, UK). Oocyte-cumulus complexes (COCs) from slaughterhouse-derived ovaries were matured in a 100 μM LA + ALA blend at a 3:1 ratio (75 μM LA + 25 μM ALA). Following maturation, selected COCs underwent reactive oxygen species (ROS) and glutathione (GSH) measurements in oocytes and apoptosis detection in CC (TUNEL). The remaining oocytes were fertilized and cultured to the blastocyst stage, where cell counts and apoptosis levels were assessed. Our findings indicate that the LA + ALA blend positively influenced specific quality parameters in oocytes (reduced ROS level) and blastocysts (increased total cell number (TCN) and a lower apoptotic index (AI)). However, the treatment did not significantly affect other parameters, such as AI in CCs, cleavage, and blastocyst rates or ICM: TCN and ICM: TE ratios. This study demonstrates that a moderate (100 μM) fatty acid (FA) dose benefits oocytes and blastocysts. Given the opposing effects of individual FAs and the limited data on FA blends, our results suggest that ALA may counteract the adverse effects of LA. Mitigation of oxidative stress and AI and an increased TCN underscore the importance of optimized FA supplementation in IVM media.

Impact of female age on concentrations of reproductive hormones and oocyte-specific growth factors in follicular fluid from human small antral follicles

STUDY QUESTION

Does maternal age impact hormonal secretions from granulosa cells, theca cells, and the oocyte in human small antral follicles?

SUMMARY ANSWER

Major hormones secreted by granulosa and theca cells, as well as the oocyte-specific TGF-β members-GDF9, BMP15, and the GDF9/BMP15 heterodimer cumulin-maintain a consistent concentration within the follicular fluid of human small antral follicles, regardless of maternal age.

WHAT IS KNOWN ALREADY

It is well established that female fertility declines with increasing age. However, it is not known whether this decline is exclusively due to a reduction in oocyte quality and quantity or also involves a decline in the hormone-secreting capabilities of granulosa cells, theca cells, and the oocyte itself.

STUDY DESIGN, SIZE, DURATION

This is a retrospective study of follicular fluid obtained from human small antral follicles collected in connection with cryopreservation of ovarian tissue at the Laboratory of Reproductive Biology, University Hospital Copenhagen, Rigshospitalet, Denmark, between 2010 and 2020 as part of the hospital's fertility preservation program.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Follicular fluid samples from human small antral follicles measuring 3-13 mm in diameter from macroscopically normal ovaries of 381 patients aged 5-43 years were included in the study, provided that at least one of the following parameters was measured: AMH, Inhibin A, Inhibin B, oestradiol (E2), progesterone (P4), androstenedione, testosterone, and/or the oocyte-specific TGF-β members GDF9, BMP15, or cumulin.

MAIN RESULTS AND THE ROLE OF CHANCE

In a linear regression analysis adjusted for follicular volume, female age did not predict the follicular fluid concentrations of AMH, Inhibin B, Inhibin A, E2, androstenedione, testosterone, GDF9, BMP15, or cumulin. Although a significant association was observed between female age and follicular fluid P4 levels, the predictive value of age was poor, accounting for at most 5% of the variation in P4.

LIMITATIONS, REASONS FOR CAUTION

Hormonal levels may vary with the degree of atresia in each follicle; however, the health status of the small antral follicles in this study was not characterized. Additionally, we cannot exclude possible age-related differences in human follicles larger than 10 mm, as very few of these were included. Furthermore, we did not include women above the age of 43, despite the potential for more pronounced age-related effects in these patients.

WIDER IMPLICATIONS OF THE FINDINGS

Our results support the idea that the age-related decline in female fertility is primarily due to a reduction in oocyte quality and quantity, but further research is needed to confirm this.

STUDY FUNDING/COMPETING INTEREST(S)

No specific funding was obtained, and the authors have no conflicts of interest to declare in relation to this work.

TRIAL REGISTRATION NUMBER

N/A.

Ovarian Endometrioma Disrupts Oocyte-Cumulus Communication and Mitochondrial Function, With Melatonin Mitigating the Effects

Ovarian endometrioma (OEM), a particularly severe form of endometriosis, is an oestrogen-dependent condition often associated with pain and infertility. The mechanisms by which OEM impairs fertility, particularly through its direct impact on oocyte-cumulus cell (CC) communication and related pathways, remain poorly understood. This study investigates the impact of OEM on oocyte-CC communication and explores melatonin's therapeutic potential. We used a mouse model of OEM and employed ovarian transcriptome and gene set enrichment analyses to identify disrupted gene pathways, alongside phalloidin staining for cytoskeletal analysis, gap junction coupling analysis for intercellular communication, and mitochondrial function assessments for cellular metabolism. Our results showed that OEM significantly impairs steroidogenesis and cumulus cell function, leading to increased apoptosis, disrupted transzonal projections (TZPs), and impaired antioxidant transfer to oocytes. This culminates in oxidative stress, mitochondrial dysfunction, and compromised ATP production. OEM oocytes also exhibited severe abnormalities, including DNA damage, maturation defects, spindle assembly disruptions, and increased aneuploidy. This study identifies disrupted TZPs as a key pathological feature in OEM and highlights melatonin's potential to restore intercellular communication, mitigate oxidative damage, and improve reproductive outcomes.

Transcriptional insights on the incomplete cytoplasmic maturation and developmental potential of oocytes cultured without granulosa cells in mice

BACKGROUND

Oocyte maturation is crucial for female fertility and embryonic development, encompassing nuclear and cytoplasmic maturation. Supportive cells of follicles, such as granulosa cells, are essential for oocyte growth and maturation. Oocytes can achieve nuclear maturation without granulosa cells during in vitro maturation (IVM). However, there is still a higher chance of incomplete cytoplasmic maturation for these oocytes with mature nuclei compared with oocytes cultured with granulosa cells. Oocytes with incomplete cytoplasmic maturation have lower fertilization rates and developmental potential than mature ones, although underlying mechanisms are poorly understood. Identifying key genes and signaling pathways associated with oocyte cytoplasmic maturation can help further elucidate the maturing process of oocytes and understand the impact of immature oocytes on embryonic development, throwing insights into the strategy to improve the success rate of assisted reproductive technologies.

RESULTS

Our study investigated murine oocytes maturing with and without granulosa cells. IVM without granulosa cells yielded oocytes with lower nuclear maturation rates than IVM with granulosa cells and in vivo maturation (IVO). Even though oocytes could achieve nuclear maturation without granulosa cells, they showed incomplete cytoplasmic maturation featuring higher levels of reactive oxygen species, lower mitochondrial density, and higher proportions of cells with abnormal distributions of cortical granules. Of note, oocytes with immature and mature cytoplasm had distinct transcriptional profiles. In the immature oocytes, we observed a deficient mRNA restoration of genes in crucial regulatory pathways of cellular growth and division, potentially affecting embryonic development. Differentially expressed genes (DEGs) between immature and mature oocytes were identified to be highly expressed in different pre-implantation stages, such as the MII oocyte, the 8-cell stage, and the ICM stage. Identified DEGs were enriched in key regulatory pathways of fertilization and embryonic development, such as energy and metabolic pathways. These observations indicated that the impeded development potential of oocytes with immature cytoplasm might be the result of abnormal gene expressions during oocyte maturation.

CONCLUSIONS

We show that granulosa cells are important for both nuclear and cytoplasmic maturation of oocytes. Abnormal gene expression in oocytes with incomplete cytoplasmic maturation may be associated with potential defects in fertilization and embryonic development.

Mitochondrial FIS1 level in cumulus cells correlates with morphological grades of human cleavage-stage embryos

PURPOSE

Advanced-age women have a lower good-quality embryo rate (GQER) compared to young women. However, GQER varies widely within the same age group, suggesting that factors beyond age influence embryo quality. Mitochondria regulate cellular metabolism through dynamic fission and fusion alterations. Specifically, cumulus cell (CC) mitochondria regulate not only the metabolism of CCs but also of adjacent oocytes. This study aims to investigate the relationship between CC mitochondrial dynamics and oocyte developmental potential post-fertilization.

METHODS

CCs were collected from 183 women aged 25-45 undergoing single sperm intracytoplasmic injection-embryo transfer treatments. Samples were stratified by age into young (< 35) and advanced age (≥ 35) groups. Each group was further subdivided into high and low subgroups based on day 3 GQER. Mitochondrial morphology, dynamics, fission-fusion gene expression, and mitochondrial functions were compared among groups and subgroups.

RESULTS

Consistent with the literature, data analysis from our laboratory revealed significant variances in GQER among individuals of the same age group. Morphological analysis suggested a negative correlation between GQER and mitochondrial length in CCs (P < 0.0001, r = - 0.38). Live-cell imaging showed that both fission and fusion frequencies of CC mitochondria in the advanced-age group were lower than those in the young group (P = 0.009, P = 0.01). Additionally, within the advanced-age group, CC mitochondria from the low GQER subgroup exhibited lower fission frequency and fission-fusion ratios compared to the high GQER subgroup (P = 0.04, P = 0.01). Consequently, GQER positively correlated with mitochondrial fission-fusion ratio in CCs (P = 0.01, r = 0.44). Notably, there were no significant differences in the expression of mitochondrial fusion-related proteins (OPA1, MFN1, and MFN2) between the advanced-age and young groups or among the subgroups. However, levels of fission proteins, including FIS1 and MFF, were significantly lower in the advanced-age group compared to the young group and in the low GQER subgroup compared to their high GQER counterparts. qPCR results further indicated that fis1 and mff mRNA levels in CCs were positively correlated with GQER (P < 0.0001, r = 0.55; P = 0.0025, r = 0.41). The CCs from the low GQER subgroup exhibit a higher level of mitochondrial dysfunction.

CONCLUSIONS

Mitochondrial morphology, fission-fusion balance, and fission-fusion gene expression in CCs influence early embryonic development, independent of age. Of these factors, the FIS1 level shows the most robust correlation with GQER.

PARL regulates porcine oocyte meiotic maturation by mediating mitochondrial activity

PARL is a rhomboid membrane protein that plays a crucial role in regulating the metabolism and maintaining the homeostasis of mitochondria which provide important energy and material reserves for oocyte maturation. However, the impact of PARL on oocyte maturation remains poorly understood. Here, we elucidated the pivotal role of PARL in oocyte maturation through its regulatory effects on mitochondrial activity. Specifically, our findings revealed that inhibiting PARL expression by interfering with RNA transcription in oocytes led to a substantial decrease in the rate of first polar body extrusion and early development of parthenogenetically activated embryos. Moreover, PARL deficiency disrupted mitochondrial distribution and activity, leading to the accumulation of ROS, abnormal distribution of CGs and actin, increased tubulin acetylation modification, disturbed spindle assembly and chromosome alignment, ultimately caused DNA damage in porcine oocytes at the metaphase II stage. Intriguingly, PARL deficiency did not cause occurrence of apoptosis in oocytes. Furthermore, our study highlighted that PARL deficiency caused the aberrant expression of genes associated with oocyte maturation, particularly those genes associated with mitochondrial function and DNA integrity. Collectively, these results demonstrate that the indispensable role of PARL in orchestrating porcine oocyte meiotic maturation though its modulation of mitochondrial activity.

Follicular metabolic dysfunction, oocyte aneuploidy and ovarian aging: a review

With the development of modern society and prolonged education, more women choose to delay their childbearing age, which greatly increases the number of women aged older than 35 years with childbearing needs. However, with increasing age, the quantity and quality of oocytes continue to fall, especially with increasing aneuploidy, which leads to a low in vitro fertilization (IVF) success rate, high abortion rate and high teratogenesis rate in assisted reproduction in women with advanced maternal age. In addition to genetics and epigenetics, follicular metabolism homeostasis is closely related to ovarian aging and oocyte aneuploidy. Glucose, lipid, and amino acid metabolism not only provide energy for follicle genesis but also regulate oocyte development and maturation. This review focuses on the relationships among follicular metabolism, oocyte aneuploidy, and ovarian aging and discusses potential therapeutic metabolites for ovarian aging.

Effect of BMP15 and GDF9 in the IVM medium on subsequent oocyte competence and embryo development of prepubertal goats

Oocyte-secreted factors (OSFs), such as BMP15 and GDF9, are soluble paracrine factors that drive cumulus cell differentiation and function, sustaining oocyte competence acquisition and embryo development. This study aimed to assess the effect of BMP15 and GDF9 on IVM medium of prepubertal goat oocytes. COCs were in vitro matured in absence (control group) or presence of 100 ng/mL of BMP15, GDF9, or both. To determine cumulus-oocyte communication, transzonal projections (TZP) density at 0h, 6h, 12h and 24h of IVM were evaluated. After IVM, mitochondrial activity, intracellular ROS and glutathione (GSH) levels, the epidermal growth factor receptor (EGFR) expression in oocytes and cumulus cells, and cumulus expansion were assessed. Blastocyst production and quality were evaluated after parthenogenetic activation (PA) and IVF. IVM supplementation with BMP15 increased the TZP density during the first 6 h of culture. After IVM, BMP15 increased mitochondrial activity, EGFR expression in oocytes and cumulus cells, and cumulus expansion compared to control, but ROS and GSH levels were similar to control. BMP15 improved blastocyst production following PA (15.5 % vs 6.3 %) and the number of cells in the blastocyst inner cell mass. No differences were observed on blastocyst production or quality following IVF. IVM supplementation with GDF9 did not improve results from control group in any parameters studied. Additionally, GDF9 in combination with BMP15 only improved mitochondrial activity and cumulus expansion over control. In conclusion, IVM medium supplementation with BMP15 (100 ng/ml) improves COCs quality parameters and PA-blastocyst production and quality of prepubertal goat oocytes. However, GDF9 (100 ng/mL) did not have any beneficial effect in this study and was possibly antagonistic to BMP15.

3-Nitropropionic acid exposure inhibits embryo development by disrupting mitochondrial function and inducing oxidative stress

3-Nitropropionic acid (3-NP) is a naturally occurring mycotoxin produced by various fungi and plants. Despite reports on its toxicity, the potential impact of 3-NP exposure on reproductive health remains elusive. To this end, we conducted an in vitro study to investigate the toxic effects of 3-NP on the developmental processes of mouse embryos. Our results suggested that exposure to 50 μM 3-NP resulted in significant pre-implantation developmental arrest , with most embryos arrested at the 2-cell stage, indicating disruption of normal development. Further analysis indicated that 3-NP exposure altered embryonic gene expression, disrupted zygotic genome activation and maternal gene degradation, and inhibited maternal-zygote transition. Moreover, it impaired mitochondrial dysfunction, causing dysfunctional cellular energy metabolism and elevated intracellular oxidative stress, culminating in increased DNA damage. Additionally, 3-NP exposure caused aberrant epigenetic modifications, particularly the upregulation of histone methylation levels, including elevated H3K27me3 and H3K9me3, which are strongly related to gene expression silencing. In summary, this study elucidates the in vitro toxic effects of 3-NP on mouse embryo development and highlights its potential adverse effects on female reproductive health.

Current status and hotspots of in vitro oocyte maturation: a bibliometric study of the past two decades

PURPOSE

In vitro maturation (IVM) of oocytes is a promising technique among assisted reproductive technologies. Although IVM has been used for many years, its efficiency is still relatively low compared to that of traditional in vitro fertilization (IVF) procedures. Therefore, we aimed to explore the hotspots and frontiers of IVM research over the past two decades and provide direction for IVM advancement.

METHODS

The articles and reviews related to IVM in the Web of Science Core Collection (WoSCC) were retrieved on June 03, 2024. Three bibliometric tools, VOSviewer 1.6.18 (2010), CiteSpace 6.1. R6 (2006), and Bibliometrix R package 4.1.0 (2017), were used to generate network maps and explore knowledge frontiers and trends. To uncover the latest research advancements and frontiers in the IVM field, we conducted an analysis of the entire IVM field, including all species. Given our focus on human IVM developments, we identified the leading countries, institutions, authors, and journals driving progress in human IVM.

RESULTS

A total of 5150 publications about IVM and 1534 publications in the specific context of human IVM were retrieved from the WoSCC. The number of publications on both overall IVM and human IVM fields has increased steadily. In human IVM, the United States (USA) and McGill University were the most prolific country and institution, respectively. Human Reproduction was both the most published in and the most cited journal in human IVM. Seang Lin, Tan was the most productive author, and Ri-Cheng, Chian's papers were the most cited in human IVM. Furthermore, five hotspot topics were summarized, namely, culture system, supplementation, cooperation in the ovarian follicle, gene expression, and oocyte cryopreservation.

CONCLUSIONS

Further studies could concentrate on the following topics: (1) the mechanisms involved in oocyte maturation in vivo and in vitro, especially in energy metabolism and intercellular communications; (2) the establishment of IVM culture systems, including standardization of the biphasic IVM culture system and supplementation; (3) the genetic differences between oocytes matured in vivo and in vitro; and (4) the mechanism of cryopreservation-inflicted damage and solutions to this challenge. For human IVM, it is necessary to precisely assess the developmental stages of oocytes and adjust the IVM process accordingly to develop tailored culture media. Concurrently, clinical trials are essential for evaluating the effectiveness and safety of IVM.

Supplementation with L-kynurenine during in vitro maturation improves bovine oocytes developmental competence through its antioxidative action

Oxidative stress impairs the developmental potential of oocytes during in vitro maturation (IVM). L-kynurenine (L-KYN), an endogenous metabolite, exhibits antioxidant, anti-inflammatory and neuroprotective effects. This work aimed to evaluate the potential effects of L-KYN on bovine oocyte IVM and its mechanisms. Different concentrations of L-KYN (0, 10, 50, 100, and 200 μmol/L) were supplemented to bovine oocyte IVM medium. Results shown a notable enhancement in the oocyte maturation rate and the subsequent zygote cleavage and blastocyst formation rate when the L-KYN concentration reached 100 μmol/L. Further analysis revealed that this treatment effectively down-regulated expression levels of genes to cumulus cell apoptosis (Bax and Caspase3), up-regulated expression levels of genes to cumulus cell expansion (HAS2, PTX3, and PTGS2) and oocyte antioxidant (GPX4 and CAT). L-KYN supplementation also effectively increased glutathione (GSH) levels, promoted oocytes mitochondrial activity, enhanced DNA repairability, deceased reactive oxygen species (ROS) levels, and reduced apoptosis. In conclusion, adding 100 μmol/L of L-KYN to IVM medium could enhance bovine oocyte quality and the subsequent embryonic development. L-KYN could be a potential antioxidant supplement for bovine oocyte maturation in vitro.

Decreased neurotensin induces ovulatory dysfunction via the NTSR1/ERK/EGR1 axis in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the predominant cause of subfertility in reproductive-aged women; however, its pathophysiology remains unknown. Neurotensin (NTS) is a member of the gut-brain peptide family and is involved in ovulation; its relationship with PCOS is unclear. Here, we found that NTS expression in ovarian granulosa cells and follicular fluids was markedly decreased in patients with PCOS. In the in vitro culture of cumulus-oocyte complexes, the neurotensin receptor 1 (NTSR1) antagonist SR48692 blocked cumulus expansion and oocyte meiotic maturation by inhibiting metabolic cooperation and damaging the mitochondrial structure in oocytes and surrounding cumulus cells. Furthermore, the ERK1/2-early growth response 1 pathway was found to be a key downstream mediator of NTS/NTSR1 in the ovulatory process. Animal studies showed that in vivo injection of SR48692 in mice reduced ovulation efficiency and contributed to irregular estrus cycles and polycystic ovary morphology. By contrast, NTS partially ameliorated the ovarian abnormalities in mice with dehydroepiandrosterone-induced PCOS. Our findings highlighted the critical role of NTS reduction and consequent abnormal NTSR1 signaling in the ovulatory dysfunction of PCOS, suggesting a potential strategy for PCOS treatment.

Downregulation of glucose-energy metabolism via AMPK signaling pathway in granulosa cells of diminished ovarian reserve patients

Glucose metabolism plays a crucial role in the function of granulosa cells (GCs) and the development of follicles. In cases of diminished ovarian reserve (DOR), alterations in these processes can impact female fertility. This study aims to investigate changes in glucose-energy metabolism in GCs of young DOR patients aged 20 to 35 years and their correlation with the onset and progression of DOR. 72 DOR cases and 75 women with normal ovarian reserve (NOR) as controls were included based on the POSEIDON and Bologna criteria. Samples of GCs and follicular fluid (FF) were collected for a comprehensive analysis involving transcriptomics, metabolomics, RT-qPCR, JC-1 staining, and flow cytometry. The study identified differentially expressed genes and metabolites in GCs of DOR and NOR groups, revealing 7 common pathways related to glucose-energy metabolism, along with 11 downregulated genes and 14 metabolites. Key substances in the glucose-energy metabolism pathway, such as succinate, lactate, NADP, ATP, and ADP, showed decreased levels, with the DOR group exhibiting a reduced ADP/ATP ratio. Downregulation of genes involved in glycolysis (HK, PGK, LDH1), the TCA cycle (CS), and gluconeogenesis (PCK) was observed, along with reduced glucose content and expression of glucose transporter genes (GLUT1 and GLUT3) in DOR GCs. Additionally, decreased AMPK pathway activity and impaired mitochondrial function in DOR suggest a connection between mitochondrial dysfunction and disrupted energy metabolism. Above all, the decline in glucose-energy metabolism in DOR is closely associated with its onset and progression. Reduced glucose uptake and impaired mitochondrial function in DOR GCs lead to internal energy imbalances, hindering the AMPK signaling pathway, limiting energy production and supply, and ultimately impacting follicle development and maturation.

New insights into the ovulatory process in the human ovary

BACKGROUND

Successful ovulation is essential for natural conception and fertility. Defects in the ovulatory process are associated with various conditions of infertility or subfertility in women. However, our understanding of the intra-ovarian biochemical mechanisms underlying this process in women has lagged compared to our understanding of animal models. This has been largely due to the limited availability of human ovarian samples that can be used to examine changes across the ovulatory period and delineate the underlying cellular/molecular mechanisms in women. Despite this challenge, steady progress has been made to improve our knowledge of the ovulatory process in women by: (i) collecting granulosa cells across the IVF interval, (ii) creating a novel approach to collecting follicular cells and tissues across the periovulatory period from normally cycling women, and (iii) developing unique in vitro models to examine the LH surge or hCG administration-induced ovulatory changes in gene expression, the regulatory mechanisms underlying the ovulatory changes, and the specific functions of the ovulatory factors.

OBJECTIVE AND RATIONALE

The objective of this review is to summarize findings generated using in vivo and in vitro models of human ovulation, with the goal of providing new insights into the mechanisms underlying the ovulatory process in women.

SEARCH METHODS

This review is based on the authors' own studies and a search of the relevant literature on human ovulation to date using PubMed search terms such as 'human ovulation EGF-signaling', 'human ovulation steroidogenesis', 'human ovulation transcription factor', 'human ovulation prostaglandin', 'human ovulation proteinase', 'human ovulation angiogenesis' 'human ovulation chemokine', 'human ovulatory disorder', 'human granulosa cell culture'. Our approach includes comparing the data from the authors' studies with the existing microarray or RNA-seq datasets generated using ovarian cells obtained throughout the ovulatory period from humans, monkeys, and mice.

OUTCOMES

Current findings from studies using in vivo and in vitro models demonstrate that the LH surge or hCG administration increases the expression of ovulatory mediators, including EGF-like factors, steroids, transcription factors, prostaglandins, proteolytic systems, and other autocrine and paracrine factors, similar to those observed in other animal models such as rodents, ruminants, and monkeys. However, the specific ovulatory factors induced, their expression pattern, and their regulatory mechanisms vary among different species. These species-specific differences stress the necessity of utilizing human samples to delineate the mechanisms underlying the ovulatory process in women.

WIDER IMPLICATIONS

The data from human ovulation in vivo and in vitro models have begun to fill the gaps in our understanding of the ovulatory process in women. Further efforts are needed to discover novel ovulatory factors. One approach to address these gaps is to improve existing in vitro models to more closely mimic in vivo ovulatory conditions in humans. This is critically important as the knowledge obtained from these human studies can be translated directly to aid in the diagnosis of ovulation-associated pathological conditions, for the development of more effective treatment to help women with anovulatory infertility or, conversely, to better manage ovulation for contraceptive purposes.

REGISTRATION NUMBER

N/A.

Ovarian stimulation protocols: impact on oocyte and endometrial quality and function

Ovarian stimulation (OS) truly is an art. There exists a myriad of protocols used to achieve the same goal: stimulating the ovaries to produce more than one mature oocyte to improve the chance of a live birth. However, considerable debate remains as to whether OS impacts oocyte and endometrial quality to affect in vitro fertilization outcomes. Although "more is better" has long been considered the best approach for oocyte retrieval, this review challenges that notion by examining the influence of stimulation on oocyte quality. Likewise, improved outcomes after frozen blastocyst transfer suggest that OS perturbs endometrial preparation and/or receptivity, although correlating changes with implantation success remains a challenge. Therefore, the focus of this review is to summarize our current understanding of perturbations in human oocyte quality and endometrial function induced by exogenous hormone administration. We highlight the need for further research to identify more appropriate markers of oocyte developmental competence as well as those that define the roles of the endometrium in the success of assisted reproductive technology.

Core fucosylation regulates the ovarian response via FSH receptor during follicular development

INTRODUCTION

Ovarian low response to follicle-stimulating hormone (FSH) causes infertility featuring hypergonadotropic hypogonadism, ovarian failure, and/or defective ovarian response.

OBJECTIVES

N-glycosylation is essential for FSH receptor (FSHR). Core fucosylation catalyzed by fucosyltransferase 8 (FUT8) is the most common N-glycosylation. Core fucosylation level changes between individuals and plays important roles in multiple physiological and pathological conditions. This study aims to elucidate the significance of FUT8 to modulate FSHR function in female fertility.

METHODS

Samples from patients classified as poor ovary responders (PORs) were detected with lectin blot and real-time PCR. Fut8 gene knockout (Fut8-/-) mice and FUT8-knockdown human granulosa cell line (KGN-KD) were established and in vitro fertilization (IVF) assay, western blot, molecular interaction, immunofluorescence and immunoprecipitation were applied.

RESULTS

Core fucosylation is indispensable for oocyte and follicular development. FSHR is a highly core-fucosylated glycoprotein. Loss of core fucosylation suppressed binding of FSHR to FSH, and attenuated FSHR downstream signaling in granulosa cells. Transcriptomic analysis revealed the downregulation of several transcripts crucial for oocyte meiotic progression and preimplantation development in Fut8-/- mice and in POR patients. Furthermore, loss of FUT8 inhibited the interaction between granulosa cells and oocytes, reduced transzonal projection (TZP) formation and caused poor developmental competence of oocytes after fertilization in vitro. While L-fucose administration increased the core fucosylation of FSHR, and its sensitivity to FSH.

CONCLUSION

This study first reveals a significant presence of core fucosylation in female fertility control. Decreased fucosylation on FSHR reduces the interaction of FSH-FSHR and subsequent signaling, which is a feature of the POR patients. Our results suggest that core fucosylation controls oocyte and follicular development via the FSH/FSHR pathway and is essential for female fertility in mammals.

Human oocyte capacitation culture: Essential step toward hormone-free assisted reproductive technology

Background

In vitro oocyte maturation (IVM) is not a novel concept; however, its wide-scale practice has been limited because of the lower clinical outcomes compared to conventional assisted reproductive technologies.

Methods

This comprehensive review addresses the significant advances made in oocyte in vitro maturation with the biphasic capacitation (CAPA)-IVM strategy applied to small ovarian antral follicles in humans over the last 10 years. CAPA-IVM consists of a prematuration phase wherein immature oocytes are temporarily meiotically arrested to gain competence before undergoing meiotic resumption.

Main findings

The integration of knowledge from basic research in animal models into clinical practice has led to a reevaluation of IVM for policystic ovary syndrome (PCOS) and onco-fertility patients. The introduction of meticulously conceived growth factors, hormonal supplements, and culture conditions led to an integrated biphasic CAPA-IVM system that promotes oocyte competence. A series of prospective randomized controlled studies validated the reproducible improvements in clinical outcomes and the safety of CAPA-IVM. So far, nearly 1000 babies have been born using this approach.

Conclusion

The use of CAPA-IVM in clinical studies has set the tone for major progress in the field and is achieving a safer, less expensive, and less emotionally loaded IVF experience, currently validated for PCOS patients.

Single-Cell RNA Sequencing Reveals That C5AR1 in Follicle Monocyte Cells Could Predict the Development of POI

Purpose

To investigate the follicle microenvironments of women with premature ovarian insufficiency (POI), with normal ovarian reserve function, and who are older (age >40 years) and to identify potential therapeutic targets.

Patients and Methods

In total, 9 women who underwent in vitro fertilization(IVF) or intracytoplasmic sperm injection(ICSI) were included in this study. The first punctured follicle of each patient was used. Single-cell RNA sequencing was subsequently performed to explore the characteristics of the follicle microenvironments of women with POI, with a normal ovarian reserve and who were older.

Results

In total, 87,323 cells were isolated and grouped into six clusters: T cells, B cells, neutrophils, basophils, mononuclear phagocytes (MPs), and granulosa cells. The study demonstrated that the POI samples had a smaller component ratio of MPs than did the other samples. The correlation between MPs and granulosa cells may lead to the development of POI. We found that the gene that was simultaneously downregulated in the POI group compared with the normal and older age groups was HLA-DRB5. Moreover, we observed that HLA-DRB5 was expressed mainly in monocytes. The temporal differentiation trajectory revealed that different monocytes play important roles in the beginning and end stages of differentiation. The C5AR1 gene is highly expressed in monocytes.

Conclusion

Our findings revealed that the interaction between monocytes and granulocytes may contribute to the development of POI. We found that POI lacked HLA-DRB5 expression and had impaired antigen processing and presentation activities. To a certain extent, C5AR1 could be used to predict the development of POI.

Efficacy and safety of dietary polyphenol administration as assessed by hormonal, glycolipid metabolism, inflammation and oxidative stress parameters in patients with PCOS: a meta-analysis and systematic review

BACKGROUND

The current knowledge about the efficacy and safety of dietary polyphenol administration in patients with polycystic ovarian syndrome (PCOS) is divergent.

OBJECTIVE

To evaluate the pooled efficacy and safety of dietary polyphenol administration in the treatment of patients with PCOS.

METHODS

The pubmed, Embase, Scopus, Cochrane Library, and Web of Science databases were searched for randomized controlled trials (RCTs) of dietary polyphenol administration for the treatment of PCOS. English-language RCTs involving adults with PCOS were thoroughly searched in electronic databases from the time of their establishment to May 2024. Random-effects models were used because heterogeneity was derived from differences in intervention materials and study duration, among other confounding factors. The effect sizes of the outcomes in the pooled analysis are expressed as weighted mean differences (WMDs) and 95% confidence intervals (CIs).

RESULTS

A total of 15 RCTs involving 934 patients were finally included. Compared with control treatments, dietary polyphenol administration significantly reduced luteinizing hormone (LH) (WMD: -0.85, 95% CI [-1.32 to -0.38], p = 0.00), and prolactin levels (WMD: -3.73, 95% CI [-6.73 to -0.74], p = 0.01). Dietary polyphenol administration significantly reduced insulin levels (WMD: -0.85, 95% CI [-1.32 to -0.38], p = 0.00). Regarding lipid metabolism, dietary polyphenol administration only reduced triglyceride levels (WMD: -8.96, 95% CI [-16.44 to -1.49], p = 0.02). Malondialdehyde (MDA) (WMD: -0.65, 95% CI [-0.68 to -0.62], p = 0.00), tumor necrosis factor (TNF-α) (WMD: -1.39, 95% CI [-2.41 to -0.37], p = 0.01) concentrations were significantly reduced by dietary polyphenol administration. None of the interventions significantly affected weight, body mass index (BMI), waist circumference (WC), homeostatic model-insulin resistance (HOMA-IR), fasting blood sugar (FBS), glycated hemoglobin (HBA1c), follicle-stimulating hormone (FSH), testosterone (T), dehydroepiandrosterone (DHEA), estradiol (E2), anti-Müllerian hormone (AMH), quantitative insulin-sensitivity check index (QUICKI), sex hormone-binding globulin (SHBG), total antioxidant capacity (TAC), C-peptide, C-reactive protein (CRP), high-density lipoprotein (HDL), low-density lipoprotein (LDL), cholesterol, cholesterol/HDL, acne score, thyroid-stimulating hormone (TSH), aspartate aminotransferase (AST), alanine aminotransferase (ALT) or alkaline phosphatase (ALP).

CONCLUSION

Dietary polyphenol administration was efficacious in patients with PCOS in our study. This review might provide new insight into the treatment of patients with PCOS and the potential of daily polyphenol supplementation in patients with PCOS. Nevertheless, these results must be interpreted carefully as a result of the heterogeneity and risk of bias among the studies and we expect that more high-quality RCTs evaluating the efficacy and safety of dietary polyphenol adnimistration in patients with PCOS will be conducted in the future.

SYSTEMATIC REVIEW REGISTRATION

CRD42024498494.

Enhancing oocyte in vitro maturation and quality by melatonin/bilirubin cationic nanoparticles: A promising strategy for assisted reproduction techniques

In assisted reproduction techniques, oocytes encounter elevated levels of reactive oxygen species (ROS) during in vitro maturation (IVM). Oxidative stress adversely affects oocyte quality, hampering their maturation, growth, and subsequent development. Thus, mitigating excessive ROS to safeguard less viable oocytes during IVM stands as a viable strategy. Numerous antioxidants have been explored for oocyte IVM, yielding considerable effects; however, several aspects, including solubility, stability, and safety, demand attention and resolution. In this study, we developed nanoparticles by self-assembling endogenous bilirubin and melatonin hormone coated with bilirubin-conjugated glycol chitosan (MB@GBn) to alleviate oxidative stress and enhance oocyte maturation. The optimized MB@GBn exhibited a uniform spherical shape, measuring 128 nm in particle size, with a PDI value of 0.1807 and a surface potential of +11.35 mV. The positively charged potential facilitated nanoparticle adherence to the oocyte surface through electrostatic interaction, allowing for functional action. In vitro studies demonstrated that MB@GB significantly enhanced the maturation of compromised oocytes. Further investigation revealed MB@GB's effectiveness in scavenging ROS, reducing intracellular calcium levels, and suppressing mitochondrial polarization. This study not only offers a novel perspective on nano drug delivery systems for biomedical applications but also presents an innovative strategy for enhancing oocyte IVM.

Comparison of the Mitophagy and Apoptosis Related Gene Expressions in Waste Embryo Culture Medium of Female Infertility Types

Mitochondria is an important organelle for the oocyte-to-embryo transition in the early embryonic development period. The oocyte uses mitochondria functionally and its mitochondrial DNA (mtDNA) content as the main energy source in the embryo development at the preimplantation stage. The aim of this study is to compare mitophagic, apoptotic and humanin gene expressions from the culture medium fluid in which embryos are developed and monitored among normoresponder (NOR), polycystic ovary syndrome (PCOS), young and older patients with poor ovarian reserve (POR). The study groups consisted of infertile patients who applied to the Bahçeci Umut IVF Center as NOR (Control), PCOS, POR-Advanced (POR-A) and POR-Young (POR-Y). After the isolation of total RNA from the collected samples, MFN1, MFN2, PINK1, PARKIN, SMN1, SMN2, p53 and Humanin gene expressions were determined by Real Time-PCR. The average age of only the POR-A was determined to be higher than the NOR (p < 0.001). The MFN1, SMN2 (p < 0.05), Humanin and p53 gene expressions (p < 0.001) increased, while PINK1 gene expression decreased (p < 0.05), in the POR-Y compared to the NOR. A decrease in MFN2, PARKIN (p < 0.05) and PINK1 gene expressions was determined in the PCOS compared to the NOR (p < 0.001). Furthermore, a decrease was observed in MFN2, PINK1 (p < 0.001) and Humanin gene expressions compared to the NOR (p < 0.05). The current data are the first in the literature determining the apoptotic and mitophagic status of the oocyte. The current results prove that waste embryo culture fluid may provide a non-invasive profile for important cellular parameters such as mitochondrial dysfunction in female infertility. The evaluation of significant cellular parameters can be performed much earlier without any intervention into the embryo.

Mitochondria: the epigenetic regulators of ovarian aging and longevity

Ovarian aging is a major health concern for women. Ovarian aging is associated with reduced health span and longevity. Mitochondrial dysfunction is one of the hallmarks of ovarian aging. In addition to providing oocytes with optimal energy, the mitochondria provide a co-substrate that drives epigenetic processes. Studies show epigenetic alterations, both nuclear and mitochondrial contribute to ovarian aging. Both, nuclear and mitochondrial genomes cross-talk with each other, resulting in two ways orchestrated anterograde and retrograde response that involves epigenetic changes in nuclear and mitochondrial compartments. Epigenetic alterations causing changes in metabolism impact ovarian function. Key mitochondrial co-substrate includes acetyl CoA, NAD+, ATP, and α-KG. Thus, enhancing mitochondrial function in aging ovaries may preserve ovarian function and can lead to ovarian longevity and reproductive and better health outcomes in women. This article describes the role of mitochondria-led epigenetics involved in ovarian aging and discusses strategies to restore epigenetic reprogramming in oocytes by preserving, protecting, or promoting mitochondrial function.

In vitro production of viable eggs from undeveloped oocytes in mouse preantral follicles by reconstructing granulosa cell-oocyte complexes†

In vitro culture of ungrown oocytes in preantral follicles is one of the intriguing subjects being pursued to produce viable eggs in assisted reproductive technology. Previous studies have succeeded in obtaining mature eggs after in vitro culture of preantral follicles, while denuded undeveloped oocytes, which are obtained occasionally when collecting preantral follicles, seem to be almost useless. Moreover, methods to culture them efficiently to produce viable eggs have not been established yet. The present study was conducted to demonstrate in vitro culture of mouse denuded undeveloped oocytes by reconstructing granulosa cell-oocyte complexes, and to analyze cellular communication in reconstructed granulosa cell-oocyte complexes. Single denuded undeveloped oocytes were aggregated with 1 × 104 granulosa cells in wells with U-shaped bottoms in a low-binding cell culture plate for 8 days under either 20% or 5% O2, and then the reconstructed granulosa cell-oocyte complexes formed were cultured on a collagen-coated culture membrane insert for 4 days under 5% O2. At day 8 of culture, the rates of reconstructed granulosa cell-oocyte complexes formation were significantly higher in the culture group under 5% O2 (64.9%) than that under 20% O2 (42.3%; P < 0.001); furthermore, the formation of transzonal projections was observed. After maturation and fertilization, we produced matured eggs and blastocysts at higher rates (>90% and 61.9%, respectively) in the group cultured under 5% O2. After transferring 126 two- to four-cell stage embryos, six live pups were obtained. This is the first report that demonstrates production of viable eggs after in vitro culture of denuded undeveloped oocytes from preantral follicles by reconstruction of granulosa cell-oocyte complexes.

Effect of lactose on the in vitro development of sheep secondary follicles

Considering that follicular development is an energy-dependent process, supplementation of the culture medium with energy substrates, such as lactose, would improve follicle viability and growth. Thus, the aim of this study was to evaluate the effect of lactose on morphology, development, glutathione (GSH) concentration, mitochondrial activity, DNA fragmentation, and meiotic resumption of oocytes from sheep secondary follicles cultured in vitro. Secondary follicles were isolated from the cortex of ovine ovaries and cultured individually for 18 days in α-MEM supplemented with bovine serum albumin (BSA), insulin, glutamine, hypoxanthine, transferrin, selenium and ascorbic acid (control medium: α-MEM+) or in α-MEM+ plus different concentrations of lactose (0.025, 0.05 and 0.1 M). After culture, some of the oocytes were subjected to TUNEL assay and in vitro maturation (IVM). Follicular morphology, glutathione (GSH) concentration and mitochondrial activity were evaluated at the end of the culture. At the day 18, the percentage of morphologically normal follicles was greater (P<0.05) in the treatment of 0.025 M lactose (92.5 %) compared to the control group (75.55 %). In addition, GSH concentrations increased (P<0.05) in treatment containing 0.025 M lactose compared to the other treatments. Furthermore, oocytes cultured in 0.025 M lactose had greater (P<0.05) mitochondrial activity levels than in α-MEM+ and 0.1 M lactose. The group α-MEM+ presented a increase of TUNEL-positive oocytes (35.09 %) compared to 0.025 lactose (9.09 %). The percentage of meiotic resumption was greater (P<0.05) in oocytes from secondary follicles cultured in 0.025 M lactose (54.5 %) than in α-MEM+ (45.5 %). In conclusion, 0.025 M lactose improved survival, GSH and active mitochondria levels and meiotic resumption of oocytes from in vitro cultured secondary follicles. Supplementation of the culture medium of preantral follicles with lactose can gradually provide energy to follicular cells, potentially enhancing the production of viable oocytes for biotechniques such as IVM and in vitro fertilization.

Methylmercury chloride inhibits meiotic maturation of mouse oocytes in vitro by disrupting the cytoskeleton

Methylmercury chloride (MMC) is a persistent heavy metal contaminant that can bioaccumulate in humans via the food chain, exerting detrimental effects on health. Nevertheless, the specific influence of MMC on oocyte meiotic maturation has yet to be elucidated. This research demonstrated that MMC exposure during the in vitro cultivation of mouse oocytes did not influence germinal vesicle breakdown but markedly decreased oocyte maturation rates. Subsequent analysis indicated that MMC exposure resulted in aberrant spindle morphology and disorganized chromosome alignment, alongside continuous activation of the spindle assembly checkpoint (SAC). However, MMC exposure didn't alter the localization pattern of microtubule-organizing center-associated proteins. MMC exposure considerably diminished the acetylation level of α-tubulin, signifying reduced microtubule stability. Additionally, MMC exposure disrupted the dynamic alterations of F-actin. MMC exposure didn't affect mitochondrial localization, mitochondrial membrane potential, adenosine triphosphate content or the concentrations of reactive oxygen species. Nonetheless, MMC exposure triggered DNA damage and modified histone modification levels. Consequently, the defects in oocyte maturation induced by MMC exposure can be attributed to impaired cytoskeleton dynamics and DNA damage. This study offers the first comprehensive elucidation of the negative impacts of MMC on oocyte maturation, highlighting the potential reproductive health risks associated with MMC exposure.

Flavopiridol inhibits oocyte maturation, reduces oocyte quality and blocks cumulus cell function

Flavopiridol (FP) is a plant-derived flavonoidis and used to treat cancers, fungal infections and inflammation-related diseases. However, it is not clear whether it has side effects on the female reproductive system. In this study, we aimed to investigate the toxic effects and potential underlying mechanisms of FP on oocyte maturation and cumulus cell expansion in mice. Cumulus-oocyte complexes (COCs) were cultured in vitro with FP of gradient concentration (50-1000 nM), according to the plasma concentration of FP in the clinical trial. The maturation rate and cumulus expansion index of oocytes were counted and studied by immunofluorescence staining, qRT-PCR, oocyte chromosome preparation and so on. The results showed that the FP-exposed COCs inhibited the oocyte maturation and cumulus cell expansion, leading to cell apoptosis in a dose dependent way. Oocytes exposed to 500 nM FP showed abnormalities in the spindle structure and chromosome arrangement, ultimately leading to the oocyte maturation arrest and aneuploidy. This may be due to the excessive oxidative stress caused by mitochondrial membrane potential damage and mislocalization. Therefore, when FP is used for cancer treatment, its side effects on the female reproductive system should be seriously considered.

Flavopiridol induces cell cycle arrest and apoptosis by interfering with CDK1 signaling pathway in human ovarian granulosa cells

Several clinical trials have been conducted to evaluate the use of flavopiridol (FP) to treat a variety of cancers, and almost all cancer drugs were found to be associated with toxicity and side effects. It is not clear whether the use of FP will affect the female reproductive system. Granulosa cells, as the important cells that constitute the follicle, play a crucial role in determining the reproductive ability of females. In this study, we investigated whether different concentrations of FP have a toxic effect on the growth of immortalized human ovarian granulosa cells. The results showed that FP had an inhibitory effect on cell proliferation at a level of nanomole concentration. FP reduced cell proliferation and induced apoptosis by inducing mitochondrial dysfunction and oxidative stress, as well as increasing BAX/BCL2 and pCDK1 levels. These results suggest that toxicity to the reproductive system should be considered when FP is used in clinical applications.

Cloning, bioinformatics analysis and expression of the cysteine dioxygenase type 1 (CDO1) gene in domestic yak

Introduction

The CDO1 gene is an important gene in the taurine synthesis pathway and has been observed to have high expression in ovaries of female mammals. This study aims to explore the conservation of CDO1 gene in domestic yaks, as well as to examine the fundamental characteristics of CDO1 gene and its expression in female yaks.

Methods

Ovarian samples were collected from yaks in the follicular phase, luteal phase and gestation period in this experiment, and their total RNA and protein were extracted. Then Polymerase Chain Reaction (PCR) and bioinformatics online software were used to clone and analyze the CDO1 gene. The relative expression of CDO1 in yak ovaries was detected by Quantitative Real-time PCR (RT-qPCR) and Western blotting. The distribution and localization of CDO1 protein in ovary were detected by immunohistochemistry.

Results

We have successfully cloned the coding region of CDO1 gene in yak. The results showed that the CDS region of CDO1 gene was 603 bp, encoding 200 amino acids, and was a relatively stable hydrophilic protein. CDO1 is relatively conservative in species evolution. The protein encoded by CDO1 gene does not have a signaling peptide or a transmembrane structure. It is a protein that is not involved in transmembrane transport and is mainly located in the cytoplasm. The secondary structure of the protein is dominated by the random coil. CDO1 is estimated to interact with 10 proteins. The results of RT-qPCR and Western blotting showed that the CDO1 gene exhibited the highest expression in the ovary during the luteal phase and the lowest expression in the ovary during the follicular phase (P < 0.01). The results of immunohistochemistry showed that CDO1 was mainly expressed in granular cells, theca cells and lutein cells of ovarian tissue.

Conclusion

These results suggest that the CDO1 gene has undergone minimal evolutionary changes during the course of animal evolution. The results provide a reference for further investigation of the function of CDO1 gene in reproduction and production in yaks.

Integrative Omics Reveals the Metabolic Patterns During Oocyte Growth

Well-controlled metabolism is associated with high-quality oocytes and optimal development of a healthy embryo. However, the metabolic framework that controls mammalian oocyte growth remains unknown. In the present study, we comprehensively depict the temporal metabolic dynamics of mouse oocytes during in vivo growth through the integrated analysis of metabolomics and proteomics. Many novel metabolic features are discovered during this process. Of note, glycolysis is enhanced, and oxidative phosphorylation capacity is reduced in the growing oocytes, presenting a Warburg-like metabolic program. For nucleotide biosynthesis, the salvage pathway is markedly activated during oocyte growth, whereas the de novo pathway is evidently suppressed. Fatty acid synthesis and channeling into phosphoinositides are specifically elevated in oocytes accompanying primordial follicle activation; nevertheless, fatty acid oxidation is reduced in these oocytes simultaneously. Our data establish the metabolic landscape during in vivo oocyte growth and serve as a broad resource for probing mammalian oocyte metabolism.

Multi-omics approach to reveal follicular metabolic changes and their effects on oocyte competence in PCOS patients

Background

Polycystic ovary syndrome (PCOS) is a common heterogeneous disorder linked with endocrine and metabolic disturbances. The underlying mechanism of PCOS, especially its effect on oocyte competence, remains unclear. The study aimed to identify abnormal follicular metabolic changes using a multi-omics approach in follicular fluid from PCOS patients and to determine their effects on oocyte competence.

Methods

A total of 36 women with PCOS and 35 women without PCOS who underwent in vitro fertilization and embryo transfer were included in the study. Cumulus cells and follicular fluid samples were collected. Follicular fluid samples underwent metabolomic analysis, while cumulus cell clusters from the same patients were assessed using transcriptomic analysis. Clinical information of patients and assisted reproductive technology (ART) results were recorded. Transcriptomics and metabolomics were integrated to identify disrupted pathways, and receiver operation characteristics (ROC) analysis was conducted to identify potential diagnostic biomarkers for PCOS. Pearson correlation analysis was conducted to assess the relationship between metabolites in follicular fluid and oocyte competence (fertilization and early embryo development potential).

Results

Through multi-omics analysis, we identified aberrantly expressed pathways at both transcriptional and metabolic levels, such as the citrate cycle (TCA cycle), oxidative phosphorylation, the cAMP signaling pathway, the mTOR signaling pathway, and steroid hormone biosynthesis. Ten candidate metabolites were identified based on metabolic profiling data from these altered pathways. Phytic acid, succinic acid, 2'-deoxyinosine triphosphate, and 4-trimethylammoniobutanoic acid in the follicular fluid exhibited high specificity and sensitivity in distinguishing PCOS. Among these metabolites, L-arginine showed a negative correlation with the 2PN fertilization rate and cleavage rate, while estrone sulfate showed a negative correlation with the high-quality embryo rate in the in-vitro fertilization (IVF) cycle.

Conclusions

We have conducted a preliminary study of a novel metabolic signature in women with PCOS using a multi-omics approach. The alterations in key metabolic pathways may enhance our understanding of the pathogenesis of PCOS.

The dose-dependent dual effects of alpha-ketoglutarate (AKG) on cumulus oocyte complexes during in vitro maturation

In this study, we reported for the first time the dose-dependent dual effects of Alpha-Ketoglutarate (AKG) on cumulus oocyte complexes (COCs) during in vitro maturation (IVM). AKG at appropriate concentration (30 µM) has beneficial effects on IVM. This includes improved cumulus expansion, oocyte quality, and embryo development. These effects are mediated through multiple underlying mechanisms. AKG reduced the excessive accumulation of reactive oxygen species (ROS) in cumulus cells, reduced the consumption of GSH and NADPH. Cumulus GSH and NADPH were transported to oocytes via gap junctions, thereby reducing the oxidative stress, apoptosis and maintaining the redox balance in oocytes. In addition, AKG improved the mitochondrial function by regulating the mitochondrial complex 1 related gene expression in oocytes to maintain mitochondrial membrane potential and ATP production. On the other hand, oocyte generated GDF9 could also be transported to cumulus cells to promote cumulus expansion. Conversely, a high concentration of AKG (750 µM) exerted adverse effects on IVM and suppressed the cumulus expansion as well as reduced the oocyte quality. The suppression of the cumulus expansion caused by high concentration of AKG could be rescued with GDF9 supplementation in COCs, indicating the critical role of GDF9 in IVM. The results provide valuable information on the variable effects of AKG at different concentrations on reproductive physiology.

De novo synthesis of monounsaturated fatty acids modulates exosome-mediated lipid export from human granulosa cells

BACKGROUND

Ovarian somatic cells support the maturation and fertility of oocytes. Metabolic desaturation of fatty acids in these cells has a positive paracrine impact on the maturation of oocytes. We hypothesized that the enzyme stearoyl-CoA desaturase 1 (SCD1) in granulosa cells regulates the lipid cargo of exosomes secreted from these cells by maintaining the balance between saturated and unsaturated lipids. We investigated the effect of SCD1 on exosome lipid content in a cumulus-granulosa cell model under physiologically relevant in vitro conditions.

METHODS

Non-luteinized human COV434 granulosa cells were subjected to treatment with an inhibitor of SCD1 (SCDinhib) alone, in combination with oleic acid, or under control conditions. Subsequently, the exosomes were isolated and characterized via nanoparticle tracking analysis, transmission electron microscopy, and Western blotting. We used liquid chromatography mass spectrometry to investigate the lipidomic profiles. We used quantitative PCR with TaqMan primers to assess the expression of genes involved in lipogenesis and control of cell cycle progression.

RESULTS

A trend toward exosome production was observed with a shift toward smaller exosome sizes in cells treated with SCD1inhib. This trend reached statistical significance when SCDinhib was combined with oleic acid supplementation. SCD1 inhibition led to the accumulation of saturated omega-6 lipids in exosomes. The latter effect was reversed by oleic acid supplementation, which also improved exosome production and suppressed the expression of fatty acid synthase and Cyclin D2.

CONCLUSION

These findings underscore the critical role of de novo fatty acid desaturation in the regulation of the export of specific lipids through exosomes, with potential implications for controlling intercellular communication within the ovary.

Potential mechanisms and therapeutic strategies for LPS-associated female fertility decline

As a major component of the outer membrane of Gram-negative bacteria, lipopolysaccharide (LPS) can be recognized by toll-like receptors (TLRs) and induce inflammation through MyD88 or the TIR domain-containing adapter-inducing interferon-β (TRIF) pathway. Previous studies have found that LPS-associated inflammatory/immune challenges were associated with ovarian dysfunction and reduced female fertility. However, the etiology and pathogenesis of female fertility decline associated with LPS are currently complex and multifaceted. In this review, PubMed was used to search for references on LPS and fertility decline so as to elucidate the potential mechanisms of LPS-associated female fertility decline and summarize therapeutic strategies that may improve LPS-associated fertility decline.

Impact of fluazuron on oocyte maturation: May the antiparasitic affect bovine reproduction?

Fluazuron is a novel veterinary pour-on antitick formulation which can be applied simultaneously with bovine reproduction management strategies. Considering the economic importance of the livestock industry in many countries, it is important to know whether antiparasitics such as fluazuron may cause embryonic loss. The aim of this study was to evaluate the toxicological effect of fluazuron on bovine oocytes during in vitro maturation. The best fluazuron concentrations were determined in a preliminary experiment on Chinese hamster ovary (CHO)-K1 cells and further used to compare fluazuron toxicity in both study models. Results of the annexin V and alkaline single cell gel electrophoresis assays demonstrated that fluazuron caused cytotoxicity and genotoxicity in bovine cumulus cells at all the concentrations tested (50, 75 and 100 μg fluazuron/mL). The evaluation of cortical granules and mitochondria distribution showed that cytoplasmic maturation was not affected by fluazuron treatment. However, a decrease in metaphase II + polar body, degenerate oocytes as well as disorganized chromatin in polar body were observed at all concentrations tested. Whereas the fertilization process was not altered by 50 μg/mL fluazuron, the embryo development rate decreased significantly. No significant differences were observed in any of the oxidative stress parameters assessed. This study contributes to a better understanding of fluazuron in bovines, suggesting that the antiparasitic may affect bovine reproduction and might cause embryo loss.

Long non-coding ribonucleic acid SNHG18 induced human granulosa cell apoptosis via disruption of glycolysis in ovarian aging

BACKGROUND

In-depth understanding of dynamic expression profiles of human granulosa cells (GCs) during follicular development will contribute to the diagnostic and targeted interventions for female infertility. However, genome-scale analysis of long non-coding ribonucleic acid (lncRNA) in GCs across diverse developmental stages is challenging. Meanwhile, further research is needed to determine how aberrant lncRNA expression participates in ovarian diseases.

METHODS

Granulosa cell-related lncRNAs data spanning five follicular development stages were retrieved and filtered from the NCBI dataset (GSE107746). Stage-specific lncRNA expression patterns and mRNA-lncRNA co-expression networks were identified with bioinformatic approaches. Subsequently, the expression pattern of SNHG18 was detected in GCs during ovarian aging. And SNHG18 siRNA or overexpression plasmids were transfected to SVOG cells in examining the regulatory roles of SNHG18 in GC proliferation and apoptosis. Moreover, whether PKCɛ/SNHG18 signaling take part in GC glycolysis via ENO1 were verified in SVOG cells.

RESULTS

We demonstrated that GC-related lncRNAs were specifically expressed across different developmental stages, and coordinated crucial biological functions like mitotic cell cycle and metabolic processes in the folliculogenesis. Thereafter, we noticed a strong correlation of PRKCE and SNHG18 expression in our analysis. With downregulated SNHG18 of GCs identified in the context of ovarian aging, SNHG18 knockdown could further induce cell apoptosis, retard cell proliferation and exacerbate DNA damage in SVOG cell. Moreover, downregulated PKCɛ/SNHG18 pathway interrupted the SVOG cell glycolysis by lowering the ENO1 expression.

CONCLUSIONS

Altogether, our results revealed that folliculogenesis-related lncRNA SNHG18 participated in the pathogenesis of ovarian aging, which may provide novel biomarkers for ovarian function and new insights for the infertility treatment.

Maturational competence of equine oocytes is associated with alterations in their 'cumulome'

Assisted reproductive technologies are an emerging field in equine reproduction, with species-dependent peculiarities, such as the low success rate of conventional IVF. Here, the 'cumulome' was related to the developmental capacity of its corresponding oocyte. Cumulus-oocyte complexes collected from slaughterhouse ovaries were individually matured, fertilized by ICSI, and cultured. After maturation, the cumulus was collected for proteomics analysis using label-free mass spectrometry (MS)-based protein profiling by nano-HPLC MS/MS and metabolomics analysis by UPLC-nanoESI MS. Overall, a total of 1671 proteins and 612 metabolites were included in the quantifiable 'cumulome'. According to the development of the corresponding oocytes, three groups were compared with each other: not matured (NM; n = 18), cleaved (CV; n = 15), and blastocyst (BL; n = 19). CV and BL were also analyzed together as the matured group (M; n = 34). The dataset revealed a closer connection within the two M groups and a more distinct separation from the NM group. Overrepresentation analysis detected enrichments related to energy metabolism as well as vesicular transport in the M group. Functional enrichment analysis found only the KEGG pathway 'oxidative phosphorylation' as significantly enriched in the NM group. A compound attributed to ATP was observed with significantly higher concentrations in the BL group compared with the NM group. Finally, in the NM group, proteins related to degradation of glycosaminoglycans were lower and components of cumulus extracellular matrix were higher compared to the other groups. In summary, the study revealed novel pathways associated with the maturational and developmental competence of oocytes.

Plasma Proteomics Analysis of Early Biomarkers for Predicting Female Fecundability: A Nested Case-Control Study

The present study aimed to identify and verify new plasma protein markers to predict the female fecundability level. A nested case-control study was conducted involving couples who participated in the Chinese National Free Preconception Check-up Project. Women who successfully conceive within one year were defined as the high fecundability group, and those unable to conceive were defined as the low fecundability group. In the training cohort, potential protein biomarkers were identified using proteomics technology and were further tested in a validation cohort by the Western blotting assay, enzyme-linked immunosorbent assay, and biochemical tests. Meanwhile, receiver operating characteristic curve analysis were used to evaluate the predictive value. Cox proportional hazard regression analyses were conducted to calculate hazard ratios; restricted cubic spline analysis was used to assess the linear relationship between the the protein level and hazard ratios for fecundability. Pyruvate, a key product of glycolysis, was significantly increased in the high fecundability group (P < 0.01) compared to the low fecundability group, and its area under the curve value was 0.68 (P < 0.05). There was a linear positive dose-response association between the pyruvate level and fecundability possibility (hazard ratios = 1.66, 95% CI: 1.07-2.59, p for trend = 0.025, nonlinearity, p-value = 0.2927).

Integrated ultrasensitive metabolomics and single-cell transcriptomics identify crucial regulators of sheep oocyte maturation and early embryo development in vitro

INTRODUCTION

Developmental competence of oocytes matured in vitro is limited due to a lack of complete understanding of metabolism and metabolic gene expression during oocyte maturation and embryo development. Conventional metabolic analysis requires a large number of samples and is not efficiently applicable in oocytes and early embryos, thereby posing challenges in identifying key metabolites and regulating their in vitro culture system.

OBJECTIVES

To enhance the developmental competence of sheep oocytes, this study aimed to identify and supplement essential metabolites that were deficient in the culture systems.

METHODS

The metabolic characteristics of oocytes and embryos were determined using ultrasensitive metabolomics analysis on trace samples and single-cell RNA-seq. By conducting integrated analyses of metabolites in cells (oocytes and embryos) and their developmental microenvironment (follicular fluid, oviductal fluid, and in vitro culture systems), we identified key missing metabolites in the in vitro culture systems. In order to assess the impact of these key missing metabolites on oocyte development competence, we performed in vitro culture experiments. Furthermore, omics analyses were employed to elucidate the underlying mechanisms.

RESULTS

Our findings demonstrated that betaine, carnitine and creatine were the key missing metabolites in vitro culture systems and supplementation of betaine and L-carnitine significantly improved the blastocyst formation rate (67.48% and 48.61%). Through in vitro culture experiments and omics analyses, we have discovered that L-carnitine had the potential to promote fatty acid oxidation, reduce lipid content and lipid peroxidation level, and regulate spindle morphological grade through fatty acid degradation pathway. Additionally, betaine may participate in methylation modification and osmotic pressure regulation, thereby potentially improving oocyte maturation and early embryo development in sheep.

CONCLUSION

Together, these analyses identified key metabolites that promote ovine oocyte maturation and early embryo development, while also providing a new viewpoint to improve clinical applications such as oocyte maturation or embryo culture.

Follicular fluid exosome-derived miR-339-5p enhances in vitro maturation of porcine oocytes via targeting SFPQ, a regulator of the ERK1/2 pathway

In this study, we aimed to investigate cytoplasmic maturation and miRNA expression of mature oocytes cultured in porcine follicular fluid exosomes. We also examined the effect of miR-339-5p on oocyte maturation. Twenty eight differentially expressed miRNAs were detected using miRNA-seq. We then transfected cumulus oocyte complexes with miR-339-5p mimics and inhibitor during culture. The results showed that exosomes increased endoplasmic reticulum levels and the amount of lipid droplets, and decreased ROS levels, lipid droplet size, and percentage of oocytes with abnormal cortical granule distribution. Overexpressing miR-339-5p significantly decreased cumulus expansion genes, oocyte maturation-related genes, target gene proline/glutamine-rich splicing factor (SFPQ), ERK1/2 phosphorylation levels, oocyte maturation rate, blastocyst rate, and lipid droplet number, but increased lipid droplet size and the ratio of oocytes with abnormal cortical granule distribution. Inhibiting miR-339-5p reversed the decrease observed during overexpression. Mitochondrial membrane potential and ROS levels did not differ significantly between groups. In summary, exosomes promote oocyte cytoplasmic maturation and miR-339-5p regulating ERK1/2 activity through SFPQ expression, thereby elevating oocyte maturation and blastocyst formation rate in vitro.

Granulosa cell metabolism at ovulation correlates with oocyte competence and is disrupted by obesity and aging

STUDY QUESTION

Is oocyte developmental competence associated with changes in granulosa cell (GC) metabolism?

SUMMARY ANSWER

GC metabolism is regulated by the LH surge, altered by obesity and reproductive aging, and, in women, specific metabolic profiles are associated with failed fertilization versus increased blastocyst development.

WHAT IS KNOWN ALREADY

The cellular environment in which an oocyte matures is critical to its future developmental competence. Metabolism is emerging as a potentially important factor; however, relative energy production profiles between GCs and cumulus cells and their use of differential substrates under normal in vivo ovulatory conditions are not well understood.

STUDY DESIGN, SIZE, DURATION

This study identified metabolic and substrate utilization profiles within ovarian cells in response to the LH surge, using mouse models and GCs of women undergoing gonadotropin-induced oocyte aspiration followed by IVF/ICSI.

PARTICIPANTS/MATERIALS, SETTING, METHODS

To comprehensively assess follicular energy metabolism, we used real-time metabolic analysis (Seahorse XFe96) to map energy metabolism dynamics (mitochondrial respiration, glycolysis, and fatty acid oxidation) in mouse GCs and cumulus-oocyte complexes (COCs) across a detailed time course in the lead up to ovulation. In parallel, the metabolic profile of GCs was measured in a cohort of 85 women undergoing IVF/ICSI (n = 21 with normal ovarian function; n = 64 with ovarian infertility) and correlated with clinical parameters and cycle outcomes.

MAIN RESULTS AND THE ROLE OF CHANCE

Our study reveals dynamic changes in GC energy metabolism in response to ovulatory LH, with mitochondrial respiration and glycolysis differentially affected by obesity versus aging, in both mice and women. High respiration in GCs is associated with failed fertilization (P < 0.05) in a subset of women, while glycolytic reserve and mitochondrial ATP production are correlated with on-time development at Day 3 (P < 0.05) and blastocyst formation (P < 0.01) respectively. These data provide new insights into the cellular mechanisms of infertility, by uncovering significant associations between metabolism within the ovarian follicle and oocyte developmental competence.

LIMITATIONS, REASONS FOR CAUTION

A larger prospective study is needed before the metabolic markers that were positively and negatively associated with oocyte quality can be used clinically to predict embryo outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

This study offers new insights into the importance of GC metabolism for subsequent embryonic development and highlights the potential for therapeutic strategies focused on optimizing mitochondrial metabolism to support embryonic development.

STUDY FUNDING/COMPETING INTEREST(S)

National Health and Medical Research Council (Australia). The authors have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Basal FSH values are positively associated with aneuploidy incidence in pre-advanced maternal age (AMA) but not in AMA patients

PURPOSE

To assess the impact of maternal age on the association between maternal basal FSH and aneuploidy.

METHODS

A retrospective study including data from 1749 blastocysts diagnosed as euploid or aneuploid by PGT-A (preimplantation genetic testing for aneuploidy). Aneuploidy incidence was compared between embryos from mothers with high vs. low basal FSH levels (above and below the group median, respectively) in total, pre-AMA (advanced maternal age; < 35 years, 198 embryos) and AMA (≥ 35 years, 1551 embryos) patient groups, separately. To control for the interference of potentially confounding variables, the association between aneuploidy and high basal FSH levels was assessed by multivariate logistic analysis in overall, pre-AMA and AMA patient groups.

RESULTS

Overall, aneuploidy rate was 9% higher (p = 0.02) in embryos from patients with high basal FSH (63.7%) compared to those with low basal FSH (58.4%). In the pre-AMA subgroup, aneuploidy incidence was 35% higher (p = 0.04) in embryos from patients with high basal FSH (53.5%) compared to those with low basal FSH (39.4%). Differently, aneuploidy occurrence did not vary between embryos from AMA patients with low (61.0%) and high (64.8%) basal FSH (p = 0.12). The multivariate analysis revealed that, in pre-AMA embryos, the association between aneuploidy occurrence and high basal FSH is independent of potential confounding variables (p = 0.04).

CONCLUSION

Maternal basal FSH values are associated with embryo aneuploidy in pre-AMA but not in AMA patients. The present findings suggest that basal FSH is a useful parameter to assess aneuploidy risk in pre-AMA patients and reinforce the hypothesis that excessive FSH signalling can predispose to oocyte meiotic errors.

β-resorcylic acid released by Limosilactobacillus reuteri protects against cisplatin-induced ovarian toxicity and infertility

Chemotherapy-induced premature ovarian insufficiency (CIPOI) triggers gonadotoxicity in women undergoing cancer treatment, leading to loss of ovarian reserves and subfertility, with no effective therapies available. In our study, fecal microbiota transplantation in a cisplatin-induced POI mouse model reveals that a dysbiotic gut microbiome negatively impacts ovarian health in CIPOI. Multi-omics analyses show a significant decrease in Limosilactobacillus reuteri and its catabolite, β-resorcylic acid , in the CIPOI group in comparison to healthy controls. Supplementation with L. reuteri or β-RA mitigates cisplatin-induced hormonal disruptions, morphological damages, and reductions in follicular reserve. Most importantly, β-RA pre-treatment effectively preserves oocyte function, embryonic development, and fetus health, thereby protecting against chemotherapy-induced subfertility. Our results provide evidence that β-RA suppresses the nuclear accumulation of sex-determining region Y-box 7, which in turn reduces Bcl-2-associated X activation and inhibits granulosa cell apoptosis. These findings highlight the therapeutic potential of targeting the gut-ovary axis for fertility preservation in CIPOI.

The epithelial Na+ channel (ENaC) in ovarian granulosa cells modulates Ca2+ mobilization and gonadotrophin signaling for estrogen homeostasis and female fertility

Ovarian granulosa cells are essential to gonadotrophin-regulated estrogen production, female cycle maintenance and fertility. The epithelial Na+ channel (ENaC) is associated with female fertility; however, whether and how it plays a role in ovarian cell function(s) remained unexplored. Here, we report patch-clamp and Na+ imaging detection of ENaC expression and channel activity in both human and mouse ovarian granulosa cells, which are promoted by pituitary gonadotrophins, follicle stimulating hormone (FSH) or luteinizing hormone (LH). Cre-recombinase- and CRISPR-Cas9-based granulosa-specific knockout of ENaC α subunit (Scnn1a) in mice resulted in failed estrogen elevation at early estrus, reduced number of corpus luteum, abnormally extended estrus phase, reduced litter size and subfertility in adult female mice. Further analysis using technologies including RNA sequencing and Ca2+ imaging revealed that pharmacological inhibition, shRNA-based knockdown or the knockout of ENaC diminished spontaneous or stimulated Ca2+ oscillations, lowered the capacity of intracellular Ca2+ stores and impaired FSH/LH-stimulated transcriptome changes for estrogen production in mouse and/or human granulosa cells. Together, these results have revealed a previously undefined role of ENaC in modulating gonadotrophin signaling in granulosa cells for estrogen homeostasis and thus female fertility.

Enhancing Oocyte Quality in Aging Mice: Insights from Mesenchymal Stem Cell Therapy and FOXO3a Signaling Pathway Activation

Ovarian aging reduced the quality of oocytes, resulting in age-related female infertility. It is reported that mesenchymal stem cells (MSCs) therapy can improve age-related ovarian function decline and the success rate of in vitro maturation (IVM) in assisted reproductive therapy. In order to investigate the effectiveness and mechanisms of MSCs to enhance oocyte quality of cumulus oocyte complexes (COCs) in advanced age, this study focus on the respective functional improvement of oocytes and granulosa cells (GCs) from aging mice and further to explore and verify the possible mechanisms. Here, we studied a popular but significant protein of follicular development, Forkhead box O-3a (FOXO3a), which is a transcription factor that mediates a variety of cellular processes, but the functions of which in regulating oocyte quality in MSCs therapy still remain inconclusive. In this study, the RNA-seq data of metaphase II (MII) oocytes and GCs isolated from COCs confirmed that, GCs of immature follicles show the most potential to be the targeted cells of bone marrow mesenchymal stem cells (BMSCs) by FOXO3a signaling pathway. Furthermore, we demonstrated the effectiveness of BMSCs co-culture with aging COCs to enhance oocyte quality and found its mechanism to function via ameliorating the biological function of GCs by alleviating FOXO3a levels. These results provide significant fundamental research on MSCs therapy on ovarian aging, as well as offering guidance for raising the success rate of assisted reproductive technology such IVM in clinical and non-clinical settings.

Changes in the transcriptomic profile of cumulus cells under the influence of cumulus-oocytes complex pre-incubation

Pre-incubation of the cumulus-oocyte complex (COCs) may lead to better function of cumulus cells (CCs) and higher oocyte quality by changing the transcriptomic profile of CCs. 140 cumulus cell samples were isolated from 12 participants and divided into two groups based on pre-incubation time. In the T0 group, the COCs were immediately dissected to separate the CCs from around the oocytes. In the T2 group, CCs were prepared after 2 h of incubation. Then, the transcriptomic profile of the CCs of the non pre-incubation group was compared to the 2-h pre-incubation group. Confirmation of RNA sequencing results was done via qRT‑PCR. The CCs transcriptome analysis showed 17 genes were downregulated and 22 genes upregulated in the T2 group compared to the T0 group. Also, the pathways related to ATP production (oxidative phosphorylation, electron transport chain, and Mitochondrial complex I assembly model OXPHOS system), TNF-alpha signaling pathway, and glucocorticoid receptor pathway increased in the T2 group compared to the T0 group. Also, the TGF-β pathway was decreased in the T2 group compared to the T0 group. This study showed that 2 h pre-incubation leads to changes in important pathways in CCs, which positively affects oocyte quality.

DNA methylation, but not microRNA expression, is affected by in vitro THC exposure in bovine granulosa cells

BACKGROUND

A global increase in cannabis use has led to questions about its effects on fertility. The rise in consumption amongst women of reproductive age is a growing concern, as this group is vulnerable in terms of reproductive health. Ample evidence suggests that the psychoactive component of cannabis, Δ9-Tetrahydrocannabinol (THC), interacts with the endocannabinoid system (ECS), that helps regulate mammalian reproduction. This study aimed to research the epigenetic effects of THC in bovine granulosa cells (GCs) by (1) investigating global DNA methylation via measuring 5-mC and 5-hmC levels; (2) measuring key methylation regulators, including the methylating enzymes DNMT1, DNMT3a, DNMT3b and the demethylases TDG and TET1/2/3; and (3) assessing fertility-associated miRNAs key in developmental competency, including miR-21, -155, -33b, -324 and -346.

METHODS

Bovine GCs were used as a translational model for reproductive toxicity in humans. To determine THC effects, GCs were isolated from Cumulus-Oocyte-Complexes (COCs) from bovine ovaries, cultured in vitro for 7 days, or until confluent, and cryopreserved at passage 1 (P1). For experimentation, cells were thawed, cultured until passage 2 (P2), serum restricted for 24-h and treated for 24-h in one of five groups: control, vehicle (1:1:18 ethanol: tween: saline) and three clinically relevant THC doses (0.032, 0.32 and 3.2 μM). Global methylation was assessed by measuring 5-mC and 5-hmC levels with flow cytometry. To assess mRNA and protein expression of methylation regulators and miRNA profiles, qPCR and Western Blotting were utilized. Shapiro-Wilk test was used to determine normality within datasets. One-way ANOVA was applied to determine statistical significance using GraphPad Prism 6.0.0.

RESULTS

Results indicate a significant decrease (p = 0.0435) in 5-mC levels following low THC exposure, while no changes were observed in 5-hmC levels. A significant increase in DNMT1 following high THC exposure at the RNA level (p < 0.05) and a significant increase following low THC exposure at the protein level (p = 0.0048) were also observed. No significant differences were observed in DNMT3a/3b, TDG, TET1/2/3 mRNAs or in any of the miRNAs analyzed.

CONCLUSIONS

This research suggests that THC mainly affects DNA methylation, but not miRNA profiles, ultimately altering gene expression and likely impairing oocyte competence, maturation, and fertilization potential.

Mitochondria of Porcine Oocytes Synthesize Melatonin, Which Improves Their In Vitro Maturation and Embryonic Development

The in vitro maturation efficiency of porcine oocytes is relatively low, and this limits the production of in vitro porcine embryos. Since melatonin is involved in mammalian reproductive physiology, in this study, we have explored whether endogenously produced melatonin can help in porcine oocyte in vitro maturation. We have found, for the first time in the literature, that mitochondria are the major sites for melatonin biosynthesis in porcine oocytes. This mitochondrially originated melatonin reduces ROS production and increases the activity of the mitochondrial respiratory electron transport chain, mitochondrial biogenesis, mitochondrial membrane potential, and ATP production. Therefore, melatonin improves the quality of oocytes and their in vitro maturation. In contrast, the reduced melatonin level caused by siRNA to knockdown AANAT (siAANAT) is associated with the abnormal distribution of mitochondria, decreasing the ATP level of porcine oocytes and inhibiting their in vitro maturation. These abnormalities can be rescued by melatonin supplementation. In addition, we found that siAANAT switches the mitochondrial oxidative phosphorylation to glycolysis, a Warburg effect. This metabolic alteration can also be corrected by melatonin supplementation. All these activities of melatonin appear to be mediated by its membrane receptors since the non-selective melatonin receptor antagonist Luzindole can blunt the effects of melatonin. Taken together, the mitochondria of porcine oocytes can synthesize melatonin and improve the quality of oocyte maturation. These results provide an insight from a novel aspect to study oocyte maturation under in vitro conditions.

Mitochondrial Morphology and Function Abnormality in Ovarian Granulosa Cells of Patients with Diminished Ovarian Reserve

In this study, we examined the changes in the mitochondrial structure and function in cumulus granulosa cells of patients with diminished ovarian reserve (DOR) to explore the causes and mechanisms of decreased mitochondrial quality. The mitochondrial ultrastructure was observed by transmission electron microscope, and the function was determined by detecting the ATP content, reactive oxygen species (ROS) levels, the number of mitochondria, and the mitochondrial membrane potential. The expression of ATP synthases in relation to mitochondrial function was analyzed. Additionally, protein immunoblotting was used to compare the expression levels of mitochondrial kinetic protein, the related channel protein in the two groups. Patients with DOR had abnormal granulosa cell morphology, increased mitochondrial abnormalities, decreased mitochondrial function, and disturbed mitochondrial dynamics. Additionally, the silent information regulator 1 (SIRT1)/phospho-AMP-activated protein kinase (P-AMPK)-peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) pathway expression was decreased, which was speculated to be associated with the decreased mitochondrial mass in the DOR group. The mitochondrial mass was decreased in granulosa cells of patients in the DOR group. The mitochondrial dysfunction observed in granulosa cells of patients in the DOR group may be associated with dysregulation of the SIRT1/P-AMPK-PGC-1α-mitochondrial transcription factor A (TFAM) pathway.

Preovulatory follicular fluid secretome added to in vitro maturation medium influences the metabolism of equine cumulus-oocyte complexes

BACKGROUND

In vitro embryo production is a highly demanded reproductive technology in horses, which requires the recovery (in vivo or post-mortem) and in vitro maturation (IVM) of oocytes. Oocytes subjected to IVM exhibit poor developmental competence compared to their in vivo counterparts, being this related to a suboptimal composition of commercial maturation media. The objective of this work was to study the effect of different concentrations of secretome obtained from equine preovulatory follicular fluid (FF) on cumulus-oocyte complexes (COCs) during IVM. COCs retrieved in vivo by ovum pick up (OPU) or post-mortem from a slaughterhouse (SLA) were subjected to IVM in the presence or absence of secretome (Control: 0 µg/ml, S20: 20 µg/ml or S40: 40 µg/ml). After IVM, the metabolome of the medium used for oocyte maturation prior (Pre-IVM) and after IVM (Post-IVM), COCs mRNA expression, and oocyte meiotic competence were analysed.

RESULTS

IVM leads to lactic acid production and an acetic acid consumption in COCs obtained from OPU and SLA. However, glucose consumption after IVM was higher in COCs from OPU when S40 was added (Control Pre-IVM vs. S40 Post-IVM: 117.24 ± 7.72 vs. 82.69 ± 4.24; Mean µM ± SEM; p < 0.05), while this was not observed in COCs from SLA. Likewise, secretome enhanced uptake of threonine (Control Pre-IVM vs. S20 Post-IVM vs. S40 Post-IVM: 4.93 ± 0.33 vs. 3.04 ± 0.25 vs. 2.84 ± 0.27; Mean µM ± SEM; p < 0.05) in COCs recovered by OPU. Regarding the relative mRNA expression of candidate genes related to metabolism, Lactate dehydrogenase A (LDHA) expression was significantly downregulated when secretome was added during IVM at 20-40 µg/ml in OPU-derived COCs (Control vs. S20 vs. S40: 1.77 ± 0.14 vs. 1 ± 0.25 vs. 1.23 ± 0.14; fold change ± SEM; p < 0.05), but not in SLA COCs.

CONCLUSIONS

The addition of secretome during in vitro maturation (IVM) affects the gene expression of LDHA, glucose metabolism, and amino acid turnover in equine cumulus-oocyte complexes (COCs), with diverging outcomes observed between COCs retrieved using ovum pick up (OPU) and slaughterhouse-derived COCs (SLA).