Formation of the ovarian follicular antrum and follicular fluid

Rejuvenation of aged oocyte through exposure to young follicular microenvironment

Reproductive aging is a major cause of fertility decline, attributed to decreased oocyte quantity and developmental potential. A possible cause is aging of the surrounding follicular somatic cells that support oocyte growth and development by providing nutrients and regulatory factors. Here, by creating chimeric follicles, whereby an oocyte from one follicle was transplanted into and cultured within another follicle whose native oocyte was removed, we show that young oocytes cultured in aged follicles exhibited impeded meiotic maturation and developmental potential, whereas aged oocytes cultured within young follicles were significantly improved in rates of maturation, blastocyst formation and live birth after in vitro fertilization and embryo implantation. This rejuvenation of aged oocytes was associated with enhanced interaction with somatic cells, transcriptomic and metabolomic remodeling, improved mitochondrial function and higher fidelity of meiotic chromosome segregation. These findings provide the basis for a future follicular somatic cell-based therapy to treat female infertility.

Exploring the potential of in vitro extracellular vesicle generation in reproductive biology

The interest in the growing field of extracellular vesicle (EV) research highlights their significance in intercellular signalling and the selective transfer of biological information between donor and recipient cells. EV studies have provided valuable insights into intercellular communication mechanisms, signal identification and their involvement in disease states, offering potential avenues for manipulating pathological conditions, detecting biomarkers and developing drug-delivery systems. While our understanding of EV functions in reproductive tissues has significantly progressed, exploring their potential as biomarkers for infertility, therapeutic interventions and enhancements in assisted reproductive technologies remains to be investigated. This knowledge gap stems partly from the difficulties associated with large-scale EV production relevant to clinical applications. Most existing studies on EV production rely on conventional 2D cell culture systems, characterized by suboptimal EV yields and a failure to replicate in vivo conditions. This results in the generation of EVs that differ from their in vivo counterparts. Hence, this review firstly delves into the importance of EVs in reproduction to then expand on current techniques for in vitro EV production, specifically examining diverse methods of culture and the potential of bioengineering technologies to establish innovative systems for enhanced EV production.

Transcriptomic profiling of the oocyte-cumulus-granulosa cell complex from estrogen receptor β knockout mice

OBJECTIVE

To study the role of estrogen receptor β in follicle development and maturation and the response to gonadotropin stimulation aiming at superovulation.

DESIGN

Experimental study and transcriptomic analysis.

SETTING

Karolinka Institutet, medical university.

ANIMAL(S)

Healthy wild-type (WT) and estrogen receptor β knockout (Esr2-KO) female mice undergoing superovulation at 4 weeks, 7 weeks, and 6 months of age.

INTERVENTION(S)

Not applicable.

MAIN OUTCOME MEASURE(S)

Oocyte yield after superovulation, transcriptomic profiling of cumulus-granulosa cell complexes and oocytes, and immunohistochemical analyses.

RESULT(S)

Superovulation of estrogen receptor β (ERβ) knockout mice resulted in reduced oocyte yield at 6 months of age compared with WT mice, but younger mice had similar yields. RNA-seq analysis of cumulus cells from superovulated WT and Esr2-KO mice identified genes and pathways associated with among others adhesion, proliferation, Wnt-signaling, and placed ERβ in bipotential granulosa cell cluster. Loss of ERβ increased expression of the other estrogen receptors Esr1 and Gper1.

CONCLUSION(S)

Our results show that ERβ has an important role in regulating ovulation in response to exogenous gonadotropins in 6-month-old mice, but not in younger mice. Our transcriptomic and immunohistochemical observations suggest a dysregulation of the granulosa cell communication and lack of tight coordination between granulosa cell replication and antrum expansion. A significant upregulation of other estrogen receptors may support a compensatory mechanism sustaining fertility during younger age in Esr2-KO mice.

Extracellular vesicles and their content in the context of polycystic ovarian syndrome and endometriosis: a review

Extracellular vesicles (EVs), particles enriched in bioactive molecules like proteins, nucleic acids, and lipids, are crucial mediators of intercellular communication and play key roles in various physiological and pathological processes. EVs have been shown to be involved in ovarian follicular function and to be altered in two prevalent gynecological disorders; polycystic ovarian syndrome (PCOS) and endometriosis.Ovarian follicles are complex microenvironments where folliculogenesis takes place with well-orchestrated interactions between granulosa cells, oocytes, and their surrounding stromal cells. Recent research unveiled the presence of EVs, including exosomes and microvesicles, in the follicular fluid (FFEVs), which constitutes part of the developing oocyte's microenvironment. In the context of PCOS, a multifaceted endocrine, reproductive, and metabolic disorder, studies have explored the dysregulation of these FFEVs and their cargo. Nine PCOS studies were included in this review and two miRNAs were commonly reported in two different studies, miR-379 and miR-200, both known to play a role in female reproduction. Studies have also demonstrated the potential use of EVs as diagnostic tools and treatment options.Endometriosis, another prevalent gynecological disorder characterized by ectopic growth of endometrial-like tissue, has also been linked to aberrant EV signaling. EVs in the peritoneal fluid of women with endometriosis carry molecules that modulate the immune response and promote the establishment and maintenance of endometriosis lesions. EVs derived from endometriosis lesions, serum and peritoneal fluid obtained from patients with endometriosis showed no commonly reported biomolecules between the eleven reviewed studies. Importantly, circulating EVs have been shown to be potential biomarkers, also reflecting the severity of the pathology.Understanding the interplay of EVs within human ovarian follicles may provide valuable insights into the pathophysiology of both PCOS and endometriosis. Targeting EV-mediated communication may open avenues for novel diagnostic and therapeutic approaches for these common gynecological disorders. More research is essential to unravel the mechanisms underlying EV involvement in folliculogenesis and its dysregulation in PCOS and endometriosis, ultimately leading to more effective and personalized interventions.

From follicle to blastocyst: microRNA-34c from follicular fluid-derived extracellular vesicles modulates blastocyst quality

BACKGROUND

Within the follicular fluid, extracellular vesicles (EVs) guide oocyte growth through their cargo microRNAs (miRNAs). Here, we investigated the role of EVs and their cargo miRNAs by linking the miRNAs found in EVs, derived from the fluid of an individual follicle, to the ability of its oocyte to become a blastocyst (competent) or not (non-competent).

METHODS

Bovine antral follicles were dissected, categorized as small (2-4 mm) or large (5-8 mm) and the corresponding oocytes were subjected to individual maturation, fertilization and embryo culture to the blastocyst stage. Follicular fluid was pooled in 4 groups (4 replicates) based on follicle size and competence of the corresponding oocyte to produce a blastocyst. Follicular fluid-derived EVs were isolated, characterized, and subjected to miRNA-sequencing (Illumina Miseq) to assess differential expression (DE) in the 4 groups. Functional validation of the effect of miR-34c on embryo development was performed by supplementation of mimics and inhibitors during in vitro maturation (IVM).

RESULTS

We identified 16 DE miRNAs linked to oocyte competence when follicular size was not considered. Within the large and small follicles, 46 DE miRNAs were driving blastocyst formation in each group. Comparison of EVs from competent small and large follicles revealed 90 DE miRNAs. Cell regulation, cell differentiation, cell cycle, and metabolic process regulation were the most enriched pathways targeted by the DE miRNAs from competent oocytes. We identified bta-miR-34c as the most abundant in follicular fluid containing competent oocytes. Supplementation of miR-34c mimic and inhibitor during IVM did not affect embryo development. However, blastocyst quality, as evidenced by higher cell numbers, was significantly improved following oocyte IVM in the presence of miR-34c mimics, while miR-34c inhibitors resulted in the opposite effect.

CONCLUSION

This study demonstrates the regulatory effect of miRNAs from follicular fluid-derived EVs on oocyte competence acquisition, providing a further basis for understanding the significance of miRNAs in oocyte maturation and embryonic development. Up-regulation of miR-34c in EVs from follicular fluid containing competent oocytes and the positive impact of miR-34c mimics added during IVM on the resulting blastocysts indicate its pivotal role in oocyte competence.

Follicular Fluid Metabolomics: Tool for Predicting IVF Outcomes of Different Infertility Causes

Infertility affects approximately 15% of couples at child-bearing ages and assisted reproductive technologies (ART), especially in vitro fertilization and embryo transfer (IVF-ET), provided infertile patients with an effective solution. The current paradox is that multiple embryo transfer that may leads to severe obstetric and perinatal complications seems to be the most valid measure to secure high success rate in the majority of clinic centers. Therefore, to avoid multiple transfer of embryos, it is urgent to explore biomarkers for IVF prognosis to select high-quality oocytes and embryos. Follicular fluid (FF), a typical biofluid constituted of the plasma effusion and granulosa-cell secretion, provides essential intracellular substances for oocytes maturation and its variation in composition reflects oocyte developmental competence and embryo viability. With the advances in metabolomics methodology, metabolomics, as an accurate and sensitive analyzing method, has been utilized to explore predictors in FF for ART success. Although FF metabolomics has provided a great possibility for screening markers with diagnostic and predictive value, its effectiveness is still doubted by some researchers. This may be resulted from the ignorance of the impact of sterility causes on the FF metabolomic profiles and thus its predictive ability might not be rightly illustrated. Therefore, in this review, we categorically demonstrate the study of FF metabolomics according to specific infertility causes, expecting to reveal the predicting value of metabolomics for IVF outcomes.

Glutathione peroxidase (GPX1) - Selenocysteine metabolism preserves the follicular fluid's (FF) redox homeostasis via IGF-1- NMD cascade in follicular ovarian cysts (FOCs)

Follicular ovarian cysts (FOCs) are characterized by follicles in the ovaries that are >20 mm in diameter and persist for >10 days without the corpus luteum, leading to anovulation, dysregulation of folliculogenesis and subfertility in humans and livestock species. Despite their clinical significance, the precise impact of FOCs on oocyte reserve, maturation, and quality still needs to be explored. While FOCs are observed in both human and livestock populations, they are notably prevalent in livestock species. Consequently, livestock species serve as valuable models for investigating the molecular intricacies of FOCs. Thus, in this study, using goat FOCs, we performed integrated proteomic, metabolomic and functional analyses to demonstrate that oocyte maturation is hampered due to increased reactive oxygen species (ROS) in FOCs follicular fluid (FF) via downregulation of glutathione peroxidase (GPX1), a critical antioxidant seleno enzyme required to negate oxidative stress. Notably, GPX1 reduction was positively correlated with the FF's decline of free selenium and selenocysteine metabolic enzymes, O-phosphoryl-tRNA (Sec) selenium transferase (SEPSECS) and selenocysteine lyase (SCLY) levels. Adding GPX1, selenocysteine, or selenium to the culture media rescued the oocyte maturation abnormalities caused by FOCs FF by down-regulating the ROS. Additionally, we demonstrate that substituting GPX1 regulator, Insulin-like growth factor-I (IGF-1) in the in vitro maturation media improved the oocyte maturation in the cystic FF by down-regulating the ROS activity via suppressing Non-sense-mediated decay (NMD) of GPX1. In contrast, inhibition of IGF-1R and the target of rapamycin complex 1 (mTORC1) hampered the oocyte maturation via NMD up-regulation. These findings imply that the GPX1 regulation via selenocysteine metabolism and the IGF-1-mediated NMD may be critical for the redox homeostasis of FF. We propose that GPX1 enhancers hold promise as therapeutics for enhancing the competence of FOCs oocytes. However, further in vivo studies are necessary to validate these findings observed in vitro.

Single-cell and spatiotemporal profile of ovulation in the mouse ovary

Ovulation is a spatiotemporally coordinated process that involves several tightly controlled events, including oocyte meiotic maturation, cumulus expansion, follicle wall rupture and repair, and ovarian stroma remodeling. To date, no studies have detailed the precise window of ovulation at single-cell resolution. Here, we performed parallel single-cell RNA-seq and spatial transcriptomics on paired mouse ovaries across an ovulation time course to map the spatiotemporal profile of ovarian cell types. We show that major ovarian cell types exhibit time-dependent transcriptional states enriched for distinct functions and have specific localization profiles within the ovary. We also identified gene markers for ovulation-dependent cell states and validated these using orthogonal methods. Finally, we performed cell-cell interaction analyses to identify ligand-receptor pairs that may drive ovulation, revealing previously unappreciated interactions. Taken together, our data provides a rich and comprehensive resource of murine ovulation that can be mined for discovery by the scientific community.

Berberine alleviates inflammation in polycystic ovary syndrome by inhibiting hyaluronan synthase 2 expression

BACKGROUND

Polycystic ovary syndrome (PCOS) is a heterogeneous metabolic and endocrine disorder that causes anovulatory infertility and abnormal folliculogenesis in women of reproductive age. Several studies have revealed inflammation in PCOS follicles, and recent evidence suggests that Berberine (BBR) effectively reduces inflammatory responses in PCOS, however, the underlying mechanisms remain unclear.

PURPOSE

To determine the underlying mechanisms by which BBR alleviates inflammation in PCOS.

STUDY DESIGN

Primary human GCs from healthy women and women with PCOS, and KGN cells were used for in vitro studies. ICR mice were used for in vivo studies.

METHODS

Gene expression was measured using RT-qPCR. HAS2, inflammatory cytokines, and serum hormones were assayed by ELISA. Protein expression profiles were assayed by Western blot. Chronic low-grade inflammatory mouse models were developed by intraperitoneal injection with LPS, and PCOS mouse models were established by subcutaneous intraperitoneal injection of DHEA. BBR and 4-MU were administered by gavage. Ovarian morphologic changes were evaluated using H&E staining. HAS2 expression in the ovary was assayed using Western blot and immunohistochemistry.

RESULTS

Our results confirmed that HAS2 expression and hyaluronan (HA) accumulation are closely associated with inflammatory responses in PCOS. Data obtained from in vitro studies showed that HAS2 and inflammatory genes (e.g., MCP-1, IL-1β, and IL-6) are significantly upregulated in PCOS samples and LPS-induced KGN cells compared to their control groups. In addition, these effects were reversed by blocking HAS2 expression or HA synthesis using BBR or 4-MU, respectively. Furthermore, HAS2 overexpression induces the expression of inflammatory genes in PCOS. These results were further confirmed in LPS- and DHEA-induced mouse models, where inflammatory genes were reduced by BBR or 4-MU, and ovarian morphology was restored.

CONCLUSIONS

Our results define previously unknown links between HAS2 and chronic low-grade inflammation in the follicles of women with PCOS. BBR exerts its anti-inflammatory effects by down-regulating HAS2. This study provides a novel therapeutic target for alleviating ovarian inflammation in women with PCOS.

Using Machine Learning to Construct the Blood-Follicle Distribution Models of Various Trace Elements and Explore the Transport-Related Pathways with Multiomics Data

Permeabilities of various trace elements (TEs) through the blood-follicle barrier (BFB) play an important role in oocyte development. However, it has not been comprehensively described as well as its involved biological pathways. Our study aimed to construct a blood-follicle distribution model of the concerned TEs and explore their related biological pathways. We finally included a total of 168 women from a cohort of in vitro fertilization-embryo transfer conducted in two reproductive centers in Beijing City and Shandong Province, China. The concentrations of 35 TEs in both serum and follicular fluid (FF) samples from the 168 women were measured, as well as the multiomics features of the metabolome, lipidome, and proteome in both plasma and FF samples. Multiomics features associated with the transfer efficiencies of TEs through the BFB were selected by using an elastic net model and further utilized for pathway analysis. Various machine learning (ML) models were built to predict the concentrations of TEs in FF. Overall, there are 21 TEs that exhibited three types of consistent BFB distribution characteristics between Beijing and Shandong centers. Among them, the concentrations of arsenic, manganese, nickel, tin, and bismuth in FF were higher than those in the serum with transfer efficiencies of 1.19-4.38, while a reverse trend was observed for the 15 TEs with transfer efficiencies of 0.076-0.905, e.g., mercury, germanium, selenium, antimony, and titanium. Lastly, cadmium was evenly distributed in the two compartments with transfer efficiencies of 0.998-1.056. Multiomics analysis showed that the enrichment of TEs was associated with the synthesis and action of steroid hormones and the glucose metabolism. Random forest model can provide the most accurate predictions of the concentrations of TEs in FF among the concerned ML models. In conclusion, the selective permeability through the BFB for various TEs may be significantly regulated by the steroid hormones and the glucose metabolism. Also, the concentrations of some TEs in FF can be well predicted by their serum levels with a random forest model.

GDF9His209GlnfsTer6/S428T and GDF9Q321X/S428T bi-allelic variants caused female subfertility with defective follicle enlargement

BACKGROUND

Antral follicles consist of an oocyte cumulus complex surrounding by somatic cells, including mural granulosa cells as the inner layer and theca cells as the outsider layer. The communications between oocytes and granulosa cells have been extensively explored in in vitro studies, however, the role of oocyte-derived factor GDF9 on in vivo antral follicle development remains elusive due to lack of an appropriate animal model. Clinically, the phenotype of GDF9 variants needs to be determined.

METHODS

Whole-exome sequencing (WES) was performed on two unrelated infertile women characterized by an early rise of estradiol level and defect in follicle enlargement. Besides, WES data on 1,039 women undergoing ART treatment were collected. A Gdf9Q308X/S415T mouse model was generated based on the variant found in one of the patients.

RESULTS

Two probands with bi-allelic GDF9 variants (GDF9His209GlnfsTer6/S428T, GDF9Q321X/S428T) and eight GDF9S428T heterozygotes with normal ovarian response were identified. In vitro experiments confirmed that these variants caused reduction of GDF9 secretion, and/or alleviation in BMP15 binding. Gdf9Q308X/S415T mouse model was constructed, which recapitulated the phenotypes in probands with abnormal estrogen secretion and defected follicle enlargement. Further experiments in mouse model showed an earlier expression of STAR in small antral follicles and decreased proliferative capacity in large antral follicles. In addition, RNA sequencing of granulosa cells revealed the transcriptomic profiles related to defective follicle enlargement in the Gdf9Q308X/S415T group. One of the downregulated genes, P4HA2 (a collagen related gene), was found to be stimulated by GDF9 protein, which partly explained the phenotype of defective follicle enlargement.

CONCLUSIONS

GDF9 bi-allelic variants contributed to the defect in antral follicle development. Oocyte itself participated in the regulation of follicle development through GDF9 paracrine effect, highlighting the essential role of oocyte-derived factors on ovarian response.

Differential expression of follicular fluid exosomal microRNA in women with diminished ovarian reserve

PURPOSE

Decreased ovarian reserve function is mainly characterized by female endocrine disorders and fertility decline. Follicular fluid (FF) exosomal microRNAs (miRNAs) have been shown to regulate the function of granulosa cells (GCs). The present study explored differentially expressed miRNAs (DEmiRNAs) in patients with diminished ovarian reserve (DOR).

METHODS

FF was collected from 12 DOR patients and 12 healthy controls. DEmiRNAs between the two groups were identified and analyzed using high-throughput sequencing technology and validated by real-time quantitative PCR (RT-qPCR).

RESULTS

A total of 592 DEmiRNAs were identified using high-throughput miRNA sequencing, of which 213 were significantly upregulated and 379 were significantly downregulated. The sequencing results were further validated by RT-qPCR. These DEmiRNA target genes were mainly involved in the cancer pathway, phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway, regulation of actin cytoskeleton signaling pathway, and biological processes related to protein binding, nucleoplasm, cytoplasm, and cell membrane.

CONCLUSION

FF exosomal miRNAs are significantly differentially expressed in DOR patients versus non-DOR patients, underscoring their crucial role in regulating the pathogenesis of DOR.

Follicular fluid aids cell adhesion, spreading in an age independent manner and shows an age-dependent effect on DNA damage in fallopian tube epithelial cells

Ovarian cancer (OC) is deadly, and likely arises from the fallopian tube epithelium (FTE). Despite the association of OC with ovulation, OC typically presents in post-menopausal women who are no longer ovulating. The goal of this study was to understand how ovulation and aging interact to impact OC progression from the FTE. Follicular fluid released during ovulation induces DNA damage in the FTE, however, the role of aging on FTE exposure to follicular fluid is unexplored. Follicular fluid samples were collected from 14 women and its effects on FTE cells was assessed. Follicular fluid caused DNA damage and lipid oxidation in an age-dependent manner, but instead induced cell proliferation in a dose-dependent manner, independent of age in FTE cells. Follicular fluid regardless of age disrupted FTE spheroid formation and stimulated attachment and growth on ultra-low attachment plates. Proteomics analysis of the adhesion proteins in the follicular fluid samples identified vitronectin, a glycoprotein responsible for FTE cell attachment and spreading.

Follicular Fluid-Derived Extracellular Vesicles Influence on In Vitro Maturation of Equine Oocyte: Impact on Cumulus Cell Viability, Expansion and Transcriptome

Cumulus cell (CC) expansion is pivotal for oocyte maturation, during which CCs release factors that initiate paracrine signaling within the follicular fluid (FF). The FF is abundant in extracellular vesicles (EVs) that facilitate intercellular communication. Although bovine and murine EVs can control cumulus expansion, these effects have not been observed in equines. This study aimed to assess the impact of FF-derived EVs (ffEVs) on equine CC expansion, viability, and transcriptome. Cumulus-oocyte complexes (COCs) that underwent in vitro maturation (IVM) in the presence (200 µg protein/mL) or absence (control) of ffEVs were assessed for cumulus expansion and viability. CCs were isolated after 12 h of IVM, followed by RNA extraction, cDNA library generation, and subsequent transcriptome analysis using next-generation sequencing. Confocal microscopy images illustrated the internalization of labeled ffEVs by CCs. Supplementation with ffEVs significantly enhanced cumulus expansion in both compacted (Cp, p < 0.0001) and expanded (Ex, p < 0.05) COCs, while viability increased in Cp groups (p < 0.01), but decreased in Ex groups (p < 0.05), compared to the controls. Although transcriptome analysis revealed a subtle effect on CC RNA profiles, differentially expressed genes encompassed processes (e.g., MAPK and Wnt signaling) potentially crucial for cumulus properties and, consequently, oocyte maturation.

Metabolome implies increased fatty acid utilization and histone methylation in the follicles from hyperandrogenic PCOS women

Well-balanced metabolism is essential for the high-quality of oocytes, and metabolic fluctuations of follicular microenvironment potentially encourage functional changes in follicle cells, ultimately impacting the developmental potential of oocytes. Here, the global metabolomic profiles of follicular fluid from PCOS women with ovarian hyperandrogenism and nonhyperandrogenism were depicted by untargeted metabolome and transcriptome. In parallel, functional methods were employed to evaluate the possible impact of dysregulated metabolites on oocyte and embryo development. Our findings demonstrated that PCOS women exhibited distinct metabolic features in follicles, such as the increase in fatty acid utilization and the downregulation in amino acid metabolism. And intrafollicular androgen levels were positively correlated with contents of multiple fatty acids, suggesting androgen as one of the contributing factors to the metabolic abnormalities in PCOS follicles. Moreover, we further demonstrated that elevated levels of α-linolenic acid and H3K27me3 could hinder oocyte maturation, fertilization, and early embryo development. Hopefully, our data serve as a broad resource on the metabolic abnormalities of PCOS follicles, and advances in the relevant knowledge will allow the identification of biomarkers that predict the progression of PCOS and its poor pregnancy outcomes.

Disturbed Follicular Microenvironment in Polycystic Ovary Syndrome: Relationship to Oocyte Quality and Infertility

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with infertility and poor reproductive outcomes. The follicular fluid (FF) microenvironment plays a crucial role in oocyte development. This review summarizes evidence elucidating the alterations in FF composition in PCOS. Various studies demonstrated a pronounced proinflammatory milieu in PCOS FF, characterized by increased levels of cytokines, including but not limited to interleukin-6 (IL-6), tumor necrosis factor α, C-reactive protein, and IL-1β, concomitant with a reduction in anti-inflammatory IL-10. T lymphocytes and antigen-presenting cells are dysregulated in PCOS FF. PCOS FF exhibit heightened reactive oxygen species production and the accumulation of lipid peroxidation byproducts, and impaired antioxidant defenses. Multiple microRNAs are dysregulated in PCOS FF, disrupting signaling critical to granulosa cell function. Proteomic analysis reveals changes in pathways related to immune responses, metabolic perturbations, angiogenesis, and hormone regulation. Metabolomics identify disturbances in glucose metabolism, amino acids, lipid profiles, and steroid levels with PCOS FF. Collectively, these pathological alterations may adversely affect oocyte quality, embryo development, and fertility outcomes. Further research on larger cohorts is needed to validate these findings and to forge the development of prognostic biomarkers of oocyte developmental competence within FF. Characterizing the follicular environment in PCOS is key to elucidating the mechanisms underlying subfertility in this challenging disorder.

Different Lengths of Diet Supplementation with 10% Flaxseed Alter the Hormonal Profile and the Follicular Fluid Fatty Acid Content of Fattening Gilts

The effect of 10% dietary flaxseed fed for 3 and 6 weeks on serum hormone levels of fattening gilts, the fatty acid (FA) follicular fluid (FF) composition of small and large antral follicles, and the steroidogenesis and IGF-I secretion by isolated small antral follicles and their response to regulatory hormones (LH, FSH, IGF-I) was studied using immunoassay and gas chromatography analyses. Both supplemental periods increased levels of P4 and IGF-I in blood serum. A shorter period inhibited steroidogenesis (P4, T, E2) and IGF-I secretion by small antral follicles, which was associated with decreased levels of monounsaturated FAs (MUFA) and preferred n-6 polyunsaturated FA (PUFA) metabolism. A longer period stimulated hormone secretion at elevated levels of saturated FAs (SFA) at the expense of MUFAs and PUFAs preferring the n-3 PUFA metabolism. Out of ovarian regulators, only LH and IGF-I were able to alter the secretion of steroids and IGF-I by small follicles of fattening pigs fed a basal diet. The effect of flaxseed on the secretion of follicular hormones after both supplemental periods was altered by all regulatory hormones in a dose-dependent manner. The level of SFAs and PUFAs in FF of large follicles increased with the length of flaxseed feeding, suggesting the suppression of ovulation.

Transcriptomic signature of luteinized cumulus cells of oocytes developing to live birth after women received intracytoplasmic sperm injection

OBJECTIVE

To compare the transcriptome of human cumulus cells (CCs) from oocytes with different outcomes (pregnancy yes/no, live birth [LB] yes/no), to identify noninvasive biomarkers for oocyte selection as well as new therapeutic targets to increase LB rates from assisted reproductive technologies (ART).

DESIGN

Retrospective observational study.

SETTINGS

This study was conducted at a University Hospital in Switzerland.

PATIENTS

Subfertile couples undergoing controlled ovarian superstimulation and intracytoplasmic sperm injection with subsequent unbiopsied embryo transfer below the female age of 43 years.

INTERVENTION(S)

RNA sequencing of CCs from oocytes results in a pregnancy, no pregnancy, LB, or no LB.

MAIN OUTCOME MEASURES

Differential gene expression (DEG) between CCs of oocytes results in "no pregnancy" vs. "pregnancy" and "pregnancy only" vs. "live birth."

RESULTS

Although RNA sequencing did not reveal DEGs when comparing the transcriptomic profiles of the groups "no pregnancy" with "pregnancy," we identified 139 DEGs by comparing "pregnancy only" with "live birth," of which 28 belonged to clusters relevant to successful ART outcomes (i.e., CTGF, SERPINE2, PCK1, HHIP, HS3ST, and BIRC5). A functional enrichment analysis revealed that the transcriptome of CCs associated with LB depicts pathways of extracellular matrix, inflammatory cascades leading to ovulation, cell patterning, proliferation, and differentiation, and silencing pathways leading to apoptosis.

CONCLUSION

We identified a CCs transcriptomic profile associated with LB after embryo transfer that, after further validation, could serve to predict successful ART outcomes. The definition of relevant pathways of CCs related to oocyte competency contributes to a broader understanding of the cumulus oocyte complex and helps identify further therapeutic targets for improving ART success.

Metabolic hormones are integral regulators of female reproductive health and function

The female reproductive system is strongly influenced by nutrition and energy balance. It is well known that food restriction or energy depletion can induce suppression of reproductive processes, while overnutrition is associated with reproductive dysfunction. However, the intricate mechanisms through which nutritional inputs and metabolic health are integrated into the coordination of reproduction are still being defined. In this review, we describe evidence for essential contributions by hormones that are responsive to food intake or fuel stores. Key metabolic hormones-including insulin, the incretins (glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1), growth hormone, ghrelin, leptin, and adiponectin-signal throughout the hypothalamic-pituitary-gonadal axis to support or suppress reproduction. We synthesize current knowledge on how these multifaceted hormones interact with the brain, pituitary, and ovaries to regulate functioning of the female reproductive system, incorporating in vitro and in vivo data from animal models and humans. Metabolic hormones are involved in orchestrating reproductive processes in healthy states, but some also play a significant role in the pathophysiology or treatment strategies of female reproductive disorders. Further understanding of the complex interrelationships between metabolic health and female reproductive function has important implications for improving women's health overall.

Overexpression of Pde4d in rat granulosa cells inhibits maturation and atresia of antral follicles to induce polycystic ovary

BACKGROUND

Follicle dysplasia can cause polycystic ovary syndrome, which can lead to anovulatory infertility. This study explored gene(s) that may contribute to polycystic ovary syndrome.

METHODS

Three animal models of polycystic ovary syndrome were created by treating 3-week-old rats respectively with estradiol valerate, testosterone propionate, or constant illumination for 8 weeks. Granulosa cells from the three disease groups and from healthy controls were transcriptionally profiled to identify differentially expressed genes. The phosphodiesterase-4d (Pde4d) was screened as the most promising candidate pathogenic gene. The Pde4d was overexpressed in rats via intrabursal infection with recombinant lentivirus to see the effect of Pde4d on ovarian morphology. The potential roles of the candidate gene and interactors of the encoded protein were explored using polymerase chain reaction, western blotting, transfection and co-immunoprecipitation.

RESULTS

All three rat models of polycystic ovary syndrome showed polycystic ovary phenotype. Seven promising candidate genes were obtained by transcriptomics and verifications. Pde4d was further investigated because it could trigger downstream signaling pathways. The Pde4d overexpression in rat ovary induced cystic follicles. It inhibited follicle maturation through a mechanism involving inhibition of cAMP-PKA-CREB signaling. The Pde4d also inhibited phosphorylation of c-Jun N-terminal kinase to reduce apoptosis in the ovary, through a mechanism involving interaction of its poly-proline domain with the protein POSH.

CONCLUSION

Upregulation of Pde4d may contribute to polycystic ovary syndrome by impeding follicle maturation and preventing apoptotic atresia.

Unique hyaluronan structure of expanded oocyte-cumulus extracellular matrix in ovarian follicles

In preovulatory follicles, after the endogenous gonadotropin surge, the oocyte-cumulus complexes (OCCs) produce hyaluronan (HA) in a process called "cumulus expansion". During this process, the heavy chains (HCs) of the serum-derived inter-alpha-trypsin inhibitor (IαI) family bind covalently to synthesized HA and form a unique structure of the expanded cumulus HA-rich extracellular matrix. Understanding the biochemical mechanism of the covalent linkage between HA and the HCs of the IαI family is one of the most significant discoveries in reproductive biology, since it explains basis of the cumulus expansion process running in parallel with the oocyte maturation, both essential for ovulation. Two recent studies have supported the above-mentioned findings: in the first, seven components of the extracellular matrix were detected by proteomic, evolutionary, and experimental analyses, and in the second, the essential role of serum in the process of cumulus expansion in vitro was confirmed. We have previously demonstrated the formation of unique structure of the covalent linkage of HA to HCs of IαI in the expanded gonadotropin-stimulated OCC, as well as interactions with several proteins produced by the cumulus cells: tumor necrosis factor-alpha-induced protein 6, pentraxin 3, and versican. Importantly, deletion of these genes in the mice produces female infertility due to defects in the oocyte-cumulus structure.

Expression of interleukin-1β and its receptor in human granulosa cells and their association with steroidogenesis

This study aimed to investigate whether interleukin 1β (IL-1β) and soluble IL-1 receptor 2 (sIL-1R2) are expressed in human granulosa cells (GCs) and relate to ovarian steroidogenesis. Ninety-six women undergoing in vitro fertilization (IVF) were recruited. RT-PCR and immunocytochemistry were used to detect mRNAs and proteins of IL-1β and IL-1R2, respectively. The steroidogenesis of primary cultured GCs was evaluated following treatment with either IL-1β alone or IL-1β and FSH in combination. There were positive correlations between serum IL-1β and serum progesterone (r = 0.220, p = 0.032) and follicular fluid (FF) estradiol (r = 0.242, p = 0.018). Additionally, serum and FF sIL-1R2 were negatively and positively correlated with FF estradiol (r = -0.376, p = 0.005) and FF progesterone (r = 0.434, p = 0.001), respectively. The mRNA and protein expression of IL-1β and IL-1R2 became evident in GCs. IL-1β alone significantly increased estradiol secretion from GCs, but in the presence of FSH, it could notably promote progesterone secretion in addition to estradiol. In conclusion, IL-1β and sIL-1R2 are expressed in human GCs and substantially contribute to ovarian steroidogenesis, suggesting that the IL-1β system may be a potential target for optimizing ovarian hyperstimulation and steroidogenesis in IVF cycles.

Associations between Phthalate Metabolite Concentrations in Follicular Fluid and Reproductive Outcomes among Women Undergoing in Vitro Fertilization/Intracytoplasmic Sperm Injection Treatment

BACKGROUND

Phthalates have been reported to impair fertility in various studies. However, evidence exploring the associations between phthalate metabolites in follicular fluid (FF) and reproductive outcomes is lacking.

OBJECTIVES

To investigate the associations between phthalate metabolite concentrations in FF and in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) outcomes among women recruited from a fertility clinic.

METHODS

We included 641 women undergoing IVF/ICSI treatment from December 2018 to January 2020. The levels of eight phthalate metabolites, including monoethyl phthalate (MEP), mono-isobutyl phthalate (MiBP), mono-n -butyl phthalate (MBP), monobenzyl phthalate (MBzP), mono(2-ethylhexyl) phthalate (MEHP), mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono(2-ethyl-5-carboxypentyl) phthalate (MECPP), were quantified in FF collected on the oocyte retrieval day. Associations between quartiles of individual phthalate metabolite concentrations and nine IVF/ICSI outcomes, including oocyte yield, mature oocyte number, two distinct pronuclei (2PN) zygote number, fertilization rate, blastocyst formation rate, implantation, clinical pregnancy, miscarriage, and live birth, were estimated with generalized linear models. The effects of phthalate mixtures on IVF/ICSI outcomes were assessed using Bayesian kernel machine regression (BKMR) models.

RESULTS

After adjusting for relevant confounders, elevated quartiles of MBzP, MEHHP, and MEHP in FF were inversely associated with the numbers of retrieved oocytes, mature oocytes, and 2PN zygotes (all p for trends < 0.10 ). In comparison with the lowest quartile, the highest quartile of molar sum of di(2-ethylhexyl) phthalate metabolites (Σ DEHP ) was associated with a reduction of 9.1% [95% confidence interval (CI): - 17.1 % , - 0.37 % ] and 10.3% (95% CI: - 18.8 % , - 0.94 % ) in yielded oocyte and mature oocyte numbers, respectively. Furthermore, the BKMR models revealed inverse associations between phthalate mixtures and the numbers of retrieved oocytes and mature oocytes. We generally found null results for implantation, clinical pregnancy, miscarriage, and live birth.

DISCUSSION

Certain phthalate metabolites in FF are inversely associated with the numbers of retrieved oocytes, mature oocytes, and 2PN zygotes among women undergoing IVF/ICSI treatment. https://doi.org/10.1289/EHP11998.

Peptidomic analysis of follicular fluid in patients with polycystic ovarian syndrome

Objective: The aim of this study was to analyze and compare the differential expression of peptides within the follicular fluid of polycystic ovary syndrome (PCOS) patients versus normal women by using peptidomics techniques. The underlying mechanisms involved in PCOS pathogenesis will be explored, together with screening and identification of potential functional peptides via bioinformatics analysis. Materials and methods: A total of 12 patients who underwent in vitro fertilization and embryo transfer (IVF-ET) at the Reproductive Medicine Center of Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine from 1 September 2022 to 1 November 2022 were included in this study. The follicular fluid of PCOS patients (n = 6) and normal women (n = 6) were collected. The presence and concentration differences of various peptides were detected by the LC-MS/MS method. GO and KEGG analysis were performed on the precursor proteins of the differentially-expressed peptides, and protein network interaction analysis was carried out to identify functionally-relevant peptides among the various peptides. Results: A variety of peptides within the follicular fluid of PCOS versus normal patients were detected by peptidomics techniques. Altogether, 843 upregulated peptides and 236 downregulated peptides were detected (absolute fold change ≥2 and p < 0.05). Of these, 718 (718 = 488 + 230) peptides were only detected in the PCOS group, while 205 (205 = 174 + 31) were only detected in the control group. Gene Ontology enrichment and pathway analysis were performed to characterize peptides through their precursor proteins. We identified 18 peptides from 7 precursor proteins associated with PCOS, and 4 peptide sequences were located in the functional domains of their corresponding precursor proteins. Conclusion: In this study, differences in the follicular development of PCOS versus normal patients were revealed from the polypeptidomics of follicular development, which thus provided new insights for future studies on the pathological mechanisms of PCOS development.

Midkine characterization in human ovaries: potential new variants in follicles

OBJECTIVE

To characterize the growth factor midkine (MDK) in the human ovary to determine whether MDK is produced locally within the ovary, examine whether different ovarian cell types are more likely to produce MDK, and determine whether there are any stage-specific variations during follicle growth. Previous studies have revealed that MDK potentially affects human follicle growth and oocyte maturation. Proteomic analyses in follicular fluid (FF) have identified MDK to functionally cluster together and follow a similar expression profile to that of well-known proteins involved in ovarian follicle development. Midkine has not yet been characterized in the human ovary.

DESIGN

Descriptive study.

SETTING

University Hospital.

PATIENTS

The study included samples from 121 patients: 71 patients (aged 17-37 years) who underwent ovarian tissue cryopreservation provided granulosa cells (GC), cumulus cells, ovarian cortex, medulla tissue, and FF from small antral follicles (SAF); and 50 patients (aged 20-35 years) receiving in vitro fertilization treatment provided FF from preovulatory follicles before and after induction of final follicle maturation.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

MDK relative gene expression was quantified using a real-time quantitative polymerase chain reaction in cumulus cells, GC, and medulla tissue. Additionally, immunostaining and western blotting assays were used to detect MDK protein in the ovarian cortex, which contains preantral follicles, SAF, and medulla tissue. Furthermore, enzyme-linked immunosorbent assay analyses were performed to measure the concentration of MDK in FF aspirated from SAF and preovulatory follicles both before and 36 hours after inducing the final maturation of follicles.

RESULTS

Immunostaining and reverse transcription-quantitative polymerase chain reaction revealed a more prominent expression of MDK in GC compared with other ovarian cell types. Intrafollicular MDK concentration was significantly higher in SAF compared with preovulatory follicles. In addition, different molecular weight species of MDK were detected using western blotting in various ovarian sample types: GC and FF samples presented primarily one band of approximately 15 kDa and an additional band of approximately 13 kDa, although other bands with higher molecular weight (between 30 and 38 kDa) were detected in medulla tissue.

CONCLUSIONS

This is the first time that MDK has been immunolocalized in human ovarian cells at the protein level and that potentially different MDK variants have been detected in human FF, GC, and ovarian medulla tissue. Future studies are needed to sequence and identify the different potential MDK variants found to determine their functional importance for ovary and oocyte competence.

Cumulus expansion is impaired with advanced reproductive age due to loss of matrix integrity and reduced hyaluronan

Reproductive aging is associated with ovulatory defects. Age-related ovarian fibrosis partially contributes to this phenotype as short-term treatment with anti-fibrotic compounds improves ovulation in reproductively old mice. However, age-dependent changes that are intrinsic to the follicle may also be relevant. In this study, we used a mouse model to demonstrate that reproductive aging is associated with impaired cumulus expansion which is accompanied by altered morphokinetic behavior of cumulus cells as assessed by time-lapse microscopy. The extracellular matrix integrity of expanded cumulus-oocyte complexes is compromised with advanced age as evidenced by increased penetration of fluorescent nanoparticles in a particle exclusion assay and larger open spaces on scanning electron microscopy. Reduced hyaluronan (HA) levels, decreased expression of genes encoding HA-associated proteins (e.g., Ptx3 and Tnfaip6), and increased expression of inflammatory genes and matrix metalloproteinases underlie this loss of matrix integrity. Importantly, HA levels are decreased with age in follicular fluid of women, indicative of conserved reproductive aging mechanisms. These findings provide novel mechanistic insights into how defects in cumulus expansion contribute to age-related infertility and may serve as a target to extend reproductive longevity.

Human follicular fluid elicits select dose- and age-dependent effects on mouse oocytes and cumulus-oocyte complexes in a heterologous in vitro maturation assay

Follicular fluid (FF) is a primary microenvironment of the oocyte within an antral follicle. Although several studies have defined the composition of human FF in normal physiology and determined how it is altered in disease states, the direct impacts of human FF on the oocyte are not well understood. The difficulty of obtaining suitable numbers of human oocytes for research makes addressing such a question challenging. Therefore, we used a heterologous model in which we cultured mouse oocytes in human FF. To determine whether FF has dose-dependent effects on gamete quality, we performed in vitro maturation of denuded oocytes from reproductively young mice (6-12 weeks) in 10%, 50%, or 100% FF from participants of mid-reproductive age (32-36 years). FF impacted meiotic competence in a dose-dependent manner, with concentrations >10% inhibiting meiotic progression and resulting in spindle and chromosome alignment defects. We previously demonstrated that human FF acquires a fibro-inflammatory cytokine signature with age. Thus, to determine whether exposure to an aging FF microenvironment contributes to the age-dependent decrease in gamete quality, we matured denuded oocytes and cumulus-oocyte complexes (COCs) in FF from reproductively young (28-30 years) and old (40-42 years) participants. FF decreased meiotic progression of COCs, but not oocytes, from reproductively young and old (9-12 months) mice in an age-dependent manner. Moreover, FF had modest age-dependent impacts on mitochondrial aggregation in denuded oocytes and cumulus layer expansion dynamics in COCs, which may influence fertilization or early embryo development. Overall, these findings demonstrate that acute human FF exposure can impact select markers of mouse oocyte quality in both dose- and age-dependent manners.

Common mechanisms of physiological and pathological rupture events in biology: novel insights into mammalian ovulation and beyond

Ovulation is a cyclical biological rupture event fundamental to fertilisation and endocrine function. During this process, the somatic support cells that surround the germ cell undergo a remodelling process that culminates in breakdown of the follicle wall and release of a mature egg. Ovulation is driven by known proteolytic and inflammatory pathways as well as structural alterations to the follicle vasculature and the fluid-filled antral cavity. Ovulation is one of several types of systematic remodelling that occur in the human body that can be described as rupture. Although ovulation is a physiological form of rupture, other types of rupture occur in the human body which can be pathological, physiological, or both. In this review, we use intracranial aneurysms and chorioamniotic membrane rupture as examples of rupture events that are pathological or both pathological and physiological, respectively, and compare these to the rupture process central to ovulation. Specifically, we compared existing transcriptomic profiles, immune cell functions, vascular modifications, and biomechanical forces to identify common processes that are conserved between rupture events. In our transcriptomic analysis, we found 12 differentially expressed genes in common among two different ovulation data sets and one intracranial aneurysm data set. We also found three genes that were differentially expressed in common for both ovulation data sets and one chorioamniotic membrane rupture data set. Combining analysis of all three data sets identified two genes (Angptl4 and Pfkfb4) that were upregulated across rupture systems. Some of the identified genes, such as Rgs2, Adam8, and Lox, have been characterised in multiple rupture contexts, including ovulation. Others, such as Glul, Baz1a, and Ddx3x, have not yet been characterised in the context of ovulation and warrant further investigation as potential novel regulators. We also identified overlapping functions of mast cells, macrophages, and T cells in the process of rupture. Each of these rupture systems share local vasoconstriction around the rupture site, smooth muscle contractions away from the site of rupture, and fluid shear forces that initially increase and then decrease to predispose one specific region to rupture. Experimental techniques developed to study these structural and biomechanical changes that underlie rupture, such as patient-derived microfluidic models and spatiotemporal transcriptomic analyses, have not yet been comprehensively translated to the study of ovulation. Review of the existing knowledge, transcriptomic data, and experimental techniques from studies of rupture in other biological systems yields a better understanding of the physiology of ovulation and identifies avenues for novel studies of ovulation with techniques and targets from the study of vascular biology and parturition.

Follicular Fluid-Derived Small Extracellular Vesicles Alleviate DHEA-Induced Granulosa Cell Apoptosis by Delivering LINC00092

Polycystic ovary syndrome (PCOS) is a perplexing condition in females of reproductive age. Dysplasia of ovarian granulosa cell (GC) is implicated in PCOS. Follicular fluid (FF)-extracellular vesicles (Evs) are important in cell-cell communication during follicular development. The current study elaborated on the function and mechanism of FF-Evs in the viability and apoptosis of GC cells in PCOS development. Human GC cells KGN were treated with dehydroepiandrosterone (DHEA) to mimic a PCOS-like condition in vitro, which were further co-cultured with the FF-derived Evs (FF-Evs). The FF-Evs treatment significantly reduced DHEA-induced apoptosis of KGN cells while promoting cell viability and migration. The lncRNA microarray analysis showed that FF-Evs mainly deliver LINC00092 into the KGN cells. Knockdown of LINC00092 negated the protective effect of FF-Evs against DHEA-induced damage on KGN cells. Moreover, by performing bioinformatics analyses and biotin-labeled RNA pull-down assay, we found that LINC00092 could bind to the RNA binding protein LIN28B and inhibit its binding to pre-microRNA-18-5p, which allowed biogenesis of pre-miR-18-5p and increased the expression of miR-18b-5p, a miRNA with known alleviating role in PCOS by suppressing the PTEN mRNA. Collectively, the present work demonstrates that FF-Evs can alleviate DHEA-induced GC damage by delivering LINC00092.

Ambient black carbon particles in human ovarian tissue and follicular fluid

Evidence indicates a link between exposure to ambient air pollution and decreased female fertility. The ability of air pollution particles to reach human ovarian tissue and follicles containing the oocytes in various maturation stages has not been studied before. Particulate translocation might be an essential step in explaining reproductive toxicity and assessing associated risks. Here, we analysed the presence of ambient black carbon particles in (i) follicular fluid samples collected during ovum pick-up from 20 women who underwent assisted reproductive technology treatment and (ii) adult human ovarian tissue from 5 individuals. Follicular fluid and ovarian tissue samples were screened for the presence of black carbon particles from ambient air pollution using white light generation by carbonaceous particles under femtosecond pulsed laser illumination. We detected black carbon particles in all follicular fluid (n = 20) and ovarian tissue (n = 5) samples. Black carbon particles from ambient air pollution can reach the ovaries and follicular fluid, directly exposing the ovarian reserve and maturing oocytes. Considering the known link between air pollution and decreased fertility, the impact of such exposure on oocyte quality, ovarian ageing and fertility needs to be clarified urgently.

Metabolomic analysis of follicular fluid from women with Hashimoto thyroiditis

Hashimoto thyroiditis is an autoimmune disease characterized by hypothyroidism and a high level of anti-thyroid autoantibodies. It has shown to negatively impact female fertility; however, the mechanisms are unclear. Ovarian follicular fluid appears to be the key to understanding how Hashimoto thyroiditis affecst fertility. Thus, we aimed to evaluated the metabolic profile of follicular fluid and antithyroid autoantibody levels in the context of Hashimoto thyroiditis. We collected follicular fluid from 61 patients, namely 38 women with thyroid autoantibody positivity and 23 women as negative controls, undergoing in vitro fertilization treatment. Follicular fluid samples were analyzed using metabolomics, and thyroid autoantibodies were measured. Fifteen metabolites with higher concentrations in the follicular fluid samples from Hashimoto thyroiditis were identified, comprising five possible affected pathways: the glycerophospholipid, arachidonic acid, linoleic acid, alpha-linolenic acid, and sphingolipid metabolism pathways. These pathways are known to regulate ovarian functions. In addition, antithyroglobulin antibody concentrations in both serum and follicular fluid were more than tenfold higher in women with Hashimoto thyroiditis than in controls. Our data showed that the metabolic profile of follicular fluid is altered in women with Hashimoto thyroiditis, suggesting a potential mechanistic explanation for the association of this disease with female infertility.

The FSH-mTOR-CNP signaling axis initiates follicular antrum formation by regulating tight junction, ion pumps, and aquaporins

The initial formation of the follicular antrum (iFFA) serves as a dividing line between gonadotropin-independent and gonadotropin-dependent folliculogenesis, enabling the follicle to sensitively respond to gonadotropins for its further development. However, the mechanism underlying iFFA remains elusive. Herein, we reported that iFFA is characterized by enhanced fluid absorption, energy consumption, secretion, and proliferation and shares a regulatory mechanism with blastula cavity formation. By use of bioinformatics analysis, follicular culture, RNA interference, and other techniques, we further demonstrated that the tight junction, ion pumps, and aquaporins are essential for follicular fluid accumulation during iFFA, as a deficiency of any one of these negatively impacts fluid accumulation and antrum formation. The intraovarian mammalian target of rapamycin-C-type natriuretic peptide pathway, activated by follicle-stimulating hormone, initiated iFFA by activating tight junction, ion pumps, and aquaporins. Building on this, we promoted iFFA by transiently activating mammalian target of rapamycin in cultured follicles and significantly increased oocyte yield. These findings represent a significant advancement in iFFA research, further enhancing our understanding of folliculogenesis in mammals.

Elevated cell-free mitochondria DNA level of patients with premature ovarian insufficiency

BACKGROUND

Premature ovarian insufficiency (POI) patients present with a chronic inflammatory state. Cell-free mitochondria DNA (cf-mtDNA) has been explored as a reliable biomarker for estimating the inflammation-related disorders, however, the cf-mtDNA levels in POI patients have never been measured. Therefore, in the presenting study, we aimed to evaluate the levels of cf-mtDNA in plasma and follicular fluid (FF) of POI patients and to determine a potential role of cf-mtDNA in predicting the disease progress and pregnancy outcomes.

METHODS

We collected plasma and FF samples from POI patients, biochemical POI (bPOI) patients and control women. Quantitative real-time PCR was used to measure the ratio of mitochondrial genome to nuclear genome of cf-DNAs extracted from the plasma and FF samples.

RESULTS

The plasma cf-mtDNA levels, including COX3, CYB, ND1 and mtDNA79, were significantly higher in overt POI patients than those in bPOI patients or control women. The plasma cf-mtDNA levels were weakly correlated with ovarian reserve, and could not be improved by regular hormone replacement therapy. The levels of cf-mtDNA in FF, rather than those in plasma, exhibited the potential to predict the pregnancy outcomes, although they were comparable among overt POI, bPOI and control groups.

CONCLUSIONS

The increased plasma cf-mtDNA levels in overt POI patients indicated its role in the progress of POI and the FF cf-mtDNA content may hold the value in predicting pregnancy outcomes of POI patients.

Obesity and PCOS radically alters the snRNA composition of follicular fluid extracellular vesicles

Introduction

The ovarian follicle consists of the oocyte, somatic cells, and follicular fluid (FF). Proper signalling between these compartments is required for optimal folliculogenesis. The association between polycystic ovarian syndrome (PCOS) and extracellular vesicular small non-coding RNAs (snRNAs) signatures in follicular fluid (FF) and how this relates to adiposity is unknown. The purpose of this study was to determine whether FF extracellular vesicle (FFEV)-derived snRNAs are differentially expressed (DE) between PCOS and non-PCOS subjects; and if these differences are vesicle-specific and/or adiposity-dependent.

Methods

FF and granulosa cells (GC) were collected from 35 patients matched by demographic and stimulation parameters. FFEVs were isolated and snRNA libraries were constructed, sequenced, and analyzed.

Results

miRNAs were the most abundant biotype present, with specific enrichment in exosomes (EX), whereas in GCs long non-coding RNAs were the most abundant biotype. In obese PCOS vs. lean PCOS, pathway analysis revealed target genes involved in cell survival and apoptosis, leukocyte differentiation and migration, JAK/STAT, and MAPK signalling. In obese PCOS FFEVs were selectively enriched (FFEVs vs. GCs) for miRNAs targeting p53 signalling, cell survival and apoptosis, FOXO, Hippo, TNF, and MAPK signalling.

Discussion

We provide comprehensive profiling of snRNAs in FFEVs and GCs of PCOS and non-PCOS patients, highlighting the effect of adiposity on these findings. We hypothesize that the selective packaging and release of miRNAs specifically targeting anti-apoptotic genes into the FF may be an attempt by the follicle to reduce the apoptotic pressure of the GCs and stave off premature apoptosis of the follicle observed in PCOS.

Effects of Follicular Fluid on Physiological Characteristics and Differentiation of Fallopian Tube Epithelial Cells Implicating for Ovarian Cancer Pathogenesis

The fallopian tube (FT) is an important reproductive organ in females. Ample evidence suggests that the distal end of FT is the original site of high-grade serous ovarian carcinoma (HGSC). FT may suffer from repeated injury and repair stimulated by follicular fluid (FF); however, this hypothesis has not been examined. In fact, the molecular mechanism of homeostasis, differentiation, and the transformation of fallopian tube epithelial cells (FTECs) resulting from the stimulation of FF are still enigmatic. In this study, we examined the effects of FF along with factors present in the FF on a variety of FTEC models, including primary cell culture, ALI (air-liquid interface) culture, and 3D organ spheroid culture. We found that FF plays a similar role to estrogen in promoting cell differentiation and organoid formation. Moreover, FF significantly promotes cell proliferation and induces cell injury and apoptosis in high concentrations. These observations may help us to investigate the mechanisms of the initiation of HGSC.

Dehydroepiandrosterone supplementation and the impact of follicular fluid metabolome and cytokinome profiles in poor ovarian responders

BACKGROUND

Poor ovarian responders (POR) are women undergoing in-vitro fertilization who respond poorly to ovarian stimulation, resulting in the retrieval of lower number of oocytes, and subsequently lower pregnancy rates. The follicular fluid (FF) provides a crucial microenvironment for the proper development of follicles and oocytes through tightly controlled metabolism and cell signaling. Androgens such as dehydroepiandrosterone (DHEA) have been proposed to alter the POR follicular microenvironment, but the impact DHEA imposes on the FF metabolome and cytokine profiles is unknown. Therefore, the objective of this study is to profile and identify metabolomic changes in the FF with DHEA supplementation in POR patients.

METHODS

FF samples collected from 52 POR patients who underwent IVF with DHEA supplementation (DHEA +) and without (DHEA-; controls) were analyzed using untargeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) metabolomics and a large-scale multiplex suspension immunoassay covering 65 cytokines, chemokines and growth factors. Multivariate statistical modelling by partial least squares-discriminant regression (PLSR) analysis was performed for revealing metabolome-scale differences. Further, differential metabolite analysis between the two groups was performed by PLSR β-coefficient regression analysis and Student's t-test.

RESULTS

Untargeted metabolomics identified 118 FF metabolites of diverse chemistries and concentrations which spanned three orders of magnitude. They include metabolic products highly associated with ovarian function - amino acids for regulating pH and osmolarity, lipids such fatty acids and cholesterols for oocyte maturation, and glucocorticoids for ovarian steroidogenesis. Four metabolites, namely, glycerophosphocholine, linoleic acid, progesterone, and valine were significantly lower in DHEA + relative to DHEA- (p < 0.05-0.005). The area under the curves of progesterone glycerophosphocholine, linoleic acid and valine are 0.711, 0.730, 0.785 and 0.818 (p < 0.05-0.01). In DHEA + patients, progesterone positively correlated with IGF-1 (Pearson r: 0.6757, p < 0.01); glycerophosphocholine negatively correlated with AMH (Pearson r: -0.5815; p < 0.05); linoleic acid correlated with estradiol and IGF-1 (Pearson r: 0.7016 and 0.8203, respectively; p < 0.01 for both). In DHEA- patients, valine negatively correlated with serum-free testosterone (Pearson r: -0.8774; p < 0.0001). Using the large-scale immunoassay of 45 cytokines, we observed significantly lower MCP1, IFNγ, LIF and VEGF-D levels in DHEA + relative to DHEA.

CONCLUSIONS

In POR patients, DHEA supplementation altered the FF metabolome and cytokine profile. The identified four FF metabolites that significantly changed with DHEA may provide information for titrating and monitoring individual DHEA supplementation.

CXC chemokines influence immune surveillance in immunological disorders: Polycystic ovary syndrome and endometriosis

Reproductive health is a worldwide challenge, but it is of particular significance to women during their reproductive age. Several female reproductive problems, including polycystic ovary syndrome (PCOS) and endometriosis, affect about 10 % of women and have a negative impact on their health, fertility, and quality of life. Small, chemotactic, and secreted cytokines are CXC chemokines. Both PCOS and endometriosis demonstrate dysregulation of CXC chemokines, which are critical to the development and progression of both diseases. Recent research has shown that both in humans and animals, CXC chemokines tend to cause inflammation. It has also been found that CXC chemokines are necessary for promoting angiogenesis and inflammatory responses. CXC chemokine overexpression is frequently associated with poor survival and prognosis. CXC chemokine levels in PCOS and endometriosis patients impact their circumstances significantly. Hence, CXC chemokines have significant potential as diagnostic and prognostic biomarkers and therapeutic targets. The molecular mechanisms through which CXC chemokines promote inflammation and the development of PCOS and endometriosis are currently unknown. This article will discuss the functions of CXC chemokines in the promotion, development, and therapy of PCOS and endometriosis, as well as future research directions. The current state and future prospects of CXC chemokine -based therapeutic strategies in the management of PCOS and endometriosis are also highlighted.

ADAMTS Proteases: Importance in Animal Reproduction

Many reproductive physiological processes, such as folliculogenesis, ovulation, implantation, and fertilization, require the synthesis, remodeling, and degradation of the extracellular matrix (ECM). The ADAMTS (A Disintegrin and Metalloproteinase with Thrombospondin Motifs) family genes code for key metalloproteinases in the remodeling process of different ECM. Several genes of this family encode for proteins with important functions in reproductive processes; in particular, ADAMTS1, 4, 5 and 9 are genes that are differentially expressed in cell types and the physiological stages of reproductive tissues. ADAMTS enzymes degrade proteoglycans in the ECM of the follicles so that the oocytes can be released and regulate follicle development during folliculogenesis, favoring the action of essential growth factors, such as FGF-2, FGF-7 and GDF-9. The transcriptional regulation of ADAMTS1 and 9 in preovulatory follicles occurs because of the gonadotropin surge in preovulatory follicles, via the progesterone/progesterone receptor complex. In addition, in the case of ADAMTS1, pathways involving protein kinase A (PKA), extracellular signal regulated protein kinase (ERK1/2) and the epidermal growth factor receptor (EGFR) might contribute to ECM regulation. Different Omic studies indicate the importance of genes of the ADAMTS family from a reproductive aspect. ADAMTS genes could serve as biomarkers for genetic improvement and contribute to enhance fertility and animal reproduction; however, more research related to these genes, the synthesis of proteins encoded by these genes, and regulation in farm animals is needed.

The mechanisms that control the preantral to early antral follicle transition and the strategies to have efficient culture systems to promote their growth in vitro

Preantral to early antral follicles transition is a complex process regulated by endocrine and paracrine factors, as well as by a precise interaction among oocyte, granulosa cells and theca cells. Understanding the mechanisms that regulate this step of folliculogenesis is important to improve in vitro culture systems, and opens new perspectives to use oocytes from preantral follicles for assisted reproductive technologies. Therefore, this review aims to discuss the endocrine and paracrine mechanisms that control granulosa cell proliferation and differentiation, formation of the antral cavity, estradiol production, atresia, and follicular fluid production during the transition from preantral to early antral follicles. The strategies that promote in vitro growth of preantral follicles are also discussed.

Dysregulation of steroid metabolome in follicular fluid links phthalate exposure to diminished ovarian reserve of childbearing-age women

The widespread use of phthalates (PAEs) has drawn increasing attention due to their endocrine disruption and reproductive toxicity, while the steroid metabolome is essential for follicular development. However, the mechanism by which PAE exposure affects ovarian reserve through the steroid metabolome remains unclear. This study recruited 264 childbearing-age women in Tianjin (China) from April 2019 to August 2020 in a cross-sectional design. Target metabolome analysis of 16 steroids was performed in follicular fluid (FF) to compare diminished ovarian reserve (DOR) against normal ovarian reserve (NOR) women and differential steroids were identified using binary logistic analyses. Further analysis of eleven PAE metabolites (mPAEs) in FF was conducted, and the retrieved oocyte number (RON) representing ovarian reserve was counted. Multiple linear regression and quantile-based g-computation (qgcomp) models were used to associate individual mPAEs and mPAE mixture with the DOR-related differential steroids in FF. Mediation analysis was used to discuss the mediating effect of DOR-related steroids on the association between mPAEs and RON. Androstenedione (A4), corticosterone (CORT), cortisol (COR) and cortisone were significantly down-regulated in FF from women with DOR. Nine mPAEs with detection frequencies greater than 60% and median concentrations of 0.02-4.86 ng/mL were incorporated into statistical models. Negative associations with COR and CORT were found for mono-ethyl phthalate (mEP), mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP), and mono-2-ethylhexyl phthalate (mEHP). A positive association with cortisone was found for mEOHP, mEHP, monobutyl phthalate (mBP), and mono (2-isobutyl) phthalate (miBP). The qgcomp and mediation analyses revealed that mEP and mEOHP not only significantly contributed to the decline of COR and CORT in the mixed exposure but also indirectly reduced RON through the mediating effects of COR and CORT. In conclusion, PAE exposure may decrease ovarian reserve by downregulating COR and CORT.

The vascular endothelial growth factor (VEGF) system as a key regulator of ovarian follicle angiogenesis and growth

The vascular endothelial growth factor-A (VEGFA) system is a complex set of proteins, with multiple isoforms and receptors, including both angiogenic (VEGFxxx, VEGFR2) and antiangiogenic members (VEGFxxxb, VEGFR1 and soluble forms of VEGFR). The members of the VEGF system affect the proliferation, survival, and migration of endothelial and nonendothelial cells and are involved in the regulation of follicular angiogenesis and development. The production of VEGF by secondary follicles stimulates preantral follicular development by directly affecting follicular cells and promoting the acquisition of the follicular vasculature and downstream antrum formation. Additionally, the pattern of expression of the components of the VEGF system may provide a proangiogenic milieu capable of triggering angiogenesis and stimulating follicular cells to promote antral follicle growth, whereas, during atresia, this milieu becomes antiangiogenic and blocks follicular development.

Molecular characterization of extracellular vesicles derived from follicular fluid of women with and without PCOS: integrating analysis of differential miRNAs and proteins reveals vital molecules involving in PCOS

PURPOSE

To elucidate the characterization of extracellular vesicles (EVs) in the follicular fluid-derived extracellular vesicles (FF-EVs) and discover critical molecules and signaling pathways associating with the etiology and pathobiology of PCOS, the differentially expressed miRNAs (DEmiRNAs) and differentially expressed proteins profiles (DEPs) were initially explored and combinedly analyzed.

METHODS

First, the miRNA and protein expression profiles of FF-EVs in PCOS patients and control patients were compared by RNA-sequencing and tandem mass tagging (TMT) proteomic methods. Subsequently, Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes were used to analyze the biological function of target genes of DEmiRNAs and DEPs. Finally, to discover the functional miRNA-target gene-protein interaction pairs involved in PCOS, DEmiRs target gene datasets and DEPs datasets were used integratedly.

RESULTS

A total of 6 DEmiRNAs and 32 DEPs were identified in FF-EVs in patients with PCOS. Bioinformatics analysis revealed that DEmiRNAs target genes are mainly involved in thiamine metabolism, insulin secretion, GnRH, and Apelin signaling pathway, which are closely related to the occurrence of PCOS. DEPs also closely related to hormone metabolism processes such as steroid hormone biosynthesis. In the analysis integrating DEmiRNAs target genes and DEPs, two molecules, GRAMD1B and STPLC2, attracted our attention that are closely associated with cholesterol transport and ceramide biosynthesis, respectively.

CONCLUSION

Dysregulated miRNAs and proteins in FF-EVs, mainly involving in hormone metabolism, insulin secretion, neurotransmitters regulation, adipokine expression, and secretion, may be closely related to PCOS. The effects of GRAMD1B and STPLC2 on PCOS deserve further study.

Role of functional fatty acids in modulation of reproductive potential in livestock

Fatty acids are not only widely known as energy sources, but also play important roles in many metabolic pathways. The significance of fatty acids in modulating the reproductive potential of livestock has received greater recognition in recent years. Functional fatty acids and their metabolites improve follicular development, oocyte maturation and embryo development, as well as endometrial receptivity and placental vascular development, through enhancing energy supply and precursors for the synthesis of their productive hormones, such as steroid hormones and prostaglandins. However, many studies are focused on the impacts of individual functional fatty acids in the reproductive cycle, lacking studies involved in deeper mechanisms and optimal fatty acid requirements for specific physiological stages. Therefore, an overall consideration of the combination and synergy of functional fatty acids and the establishment of optimal fatty acid requirement for specific stages is needed to improve reproductive potential in livestock.

Isolation of Extracellular Vesicles from Human Follicular Fluid: Size-Exclusion Chromatography versus Ultracentrifugation

Follicular fluid (FF) is the microenvironment where a growing oocyte develops. Intrafollicular communication ensures oocyte competence and is carried out through paracrine signaling, the exchange of molecules via gap junctions, and the trafficking of extracellular vesicles (EVs). The study of FF-derived EVs is important for both translational and fundamental research in the female reproductive field. This study aimed to compare the efficacy and purity of two EV isolation methods: size-exclusion chromatography (SEC) and ultracentrifugation (UC). EVs isolated using SEC and UC were compared regarding their size and concentration using dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA); protein contamination was assessed with microBCA; specific EV markers were detected with Western blot, and EV morphology was studied with transmission electron microscopy (TEM). Our results show that although both techniques isolated small EVs, a significantly increased yield in particle number was clear with UC compared with SEC. On the other hand, SEC generated purer EVs with fewer protein contaminants and aggregates. In conclusion, the selection of the most suited approach to isolate EVs must be conducted considering the degree of recovery, purity, and downstream application of the isolated EVs.

The Effects of the Follicle-Stimulating Hormone on Human Follicular Fluid-Derived Stromal Cells

The prevalence of infertility is getting higher over the years. The increasing age of first-time parents, although economically more desirable, can cause various biological problems from low natural conception rate to poor pregnancy outcomes. The growing demand for assisted reproductive technology procedures worldwide draws medical specialists' and scientists' attention to various elements which could lead to successful conception, such as follicular fluid (FF) and hormones. In this study, we analyzed the effects of exposure to follicle-stimulating hormone (FSH) on FF-derived stromal cells isolated from females admitted for treatment due to infertility, participating in assisted reproductive technologies procedures. We demonstrated that FF stromal cells are positive for mesenchymal stromal cell surface markers (CD90⁺, CD44⁺, CD166⁺) and showed that FSH has no impact on FF stromal cell morphology yet lowers proliferation rate. Using a real-time polymerase chain reaction method, we indicated that the expression of PTGS2 is significantly downregulated in FF sediment cells of patients who did not conceive; furthermore, we showed that FSH can affect the expression of ovarian follicle development and FSH response-related genes differentially depending on the length of exposure and that levels of ovulatory cascade genes differ in conceived and not-conceived patients' FF stromal cells. Using mass spectrometry analysis, we identified 97 proteins secreted by FF stromal cells. The identified proteins are related to stress response, positive regulation of apoptotic cell clearance and embryo implantation.

Biomechanical forces and signals operating in the ovary during folliculogenesis and their dysregulation: implications for fertility

BACKGROUND

Folliculogenesis occurs in the highly dynamic environment of the ovary. Follicle cyclic recruitment, neo-angiogenesis, spatial displacement, follicle atresia and ovulation stand out as major events resulting from the interplay between mechanical forces and molecular signals. Morphological and functional changes to the growing follicle and to the surrounding tissue are required to produce oocytes capable of supporting preimplantation development to the blastocyst stage.

OBJECTIVE AND RATIONALE

This review will summarize the ovarian morphological and functional context that contributes to follicle recruitment, growth and ovulation, as well as to the acquisition of oocyte developmental competence. We will describe the changes occurring during folliculogenesis to the ovarian extracellular matrix (ECM) and to the vasculature, their influence on the mechanical properties of the ovarian tissue, and, in turn, their influence on the regulation of signal transduction. Also, we will outline how their dysregulation might be associated with pathologies such as polycystic ovary syndrome (PCOS), endometriosis or premature ovarian insufficiency (POI). Finally, for each of these three pathologies, we will highlight therapeutic strategies attempting to correct the altered biomechanical context in order to restore fertility.

SEARCH METHODS

For each area discussed, a systematic bibliographical search was performed, without temporal limits, using PubMed Central, Web of Science and Scopus search engines employing the keywords extracellular matrix, mechanobiology, biomechanics, vasculature, angiogenesis or signalling pathway in combination with: ovary, oogenesis, oocyte, folliculogenesis, ovarian follicle, theca, granulosa, cumulus, follicular fluid, corpus luteum, meiosis, oocyte developmental competence, preimplantation, polycystic ovary syndrome, premature ovarian insufficiency or endometriosis.

OUTCOMES

Through search engines queries, we yielded a total of 37 368 papers that were further selected based on our focus on mammals and, specifically, on rodents, bovine, equine, ovine, primates and human, and also were trimmed around each specific topic of the review. After the elimination of duplicates, this selection process resulted in 628 papers, of which 287 were cited in the manuscript. Among these, 89.2% were published in the past 22 years, while the remaining 8.0%, 2.4% or 0.3% were published during the 1990s, 1980s or before, respectively. During folliculogenesis, changes occur to the ovarian ECM composition and organization that, together with vasculature modelling around the growing follicle, are aimed to sustain its recruitment and growth, and the maturation of the enclosed oocyte. These events define the scenario in which mechanical forces are key to the regulation of cascades of molecular signals. Alterations to this context determine impaired folliculogenesis and decreased oocyte developmental potential, as observed in pathological conditions which are causes of infertility, such as PCOS, endometriosis or POI.

WIDER IMPLICATIONS

The knowledge of these mechanisms and the rules that govern them lay a sound basis to explain how follicles recruitment and growth are modulated, and stimulate insights to develop, in clinical practice, strategies to improve follicular recruitment and oocyte competence, particularly for pathologies like PCOS, endometriosis and POI.

Follicular fluid extracellular vesicle miRNAs and ovarian aging

The decrease in the reproductive potential due to aging occurs as a gradual decline in the quantity and quality of the ovarian reserve, a phenomenon associated with risk of miscarriage, pregnancy loss, low ovarian stimulation, and oocyte abnormalities, such as chromosomal aneuploidies. Numerous studies have shown that the fertility potential of older women is decreased by changes to the cellular composition of the follicles. Additionally, a unique method of cellular communication has been identified which involves the release of extracellular vesicles (EVs) in various body fluids including follicular fluid (FF). The changing composition of EVs especially non-coding RNAs, such as miRNAs has been documented across a broad range of cell types during aging. Accordingly, alterations of miRNA cargo within FF-derived EVs due to increased age may serve as a potential predictor of oocyte quality. In this review we examine the relationship between FF EV miRNAs and ovarian aging.

Population structure, genetic diversity and prolificacy in pishan red sheep under an extreme desert environment

Extreme environmental conditions are a major challenge for livestock production. Changes in climate conditions, especially those that lead to extreme weather, can reduce livestock production. The screening of genes and molecular markers is of great significance to explore the genetic mechanism of sheep prolificacy traits in Taklimakan Desert environment. We selected healthy adult Pishan Red Sheep (PRS) and Qira Black Sheep (QR) which live in Taklimakan Desert environment, collected blood from jugular vein, extracted DNA, and prepared Illumina Ovine SNP50 chip. For PRS, linkage disequilibrium (LD) was calculated using the ovine SNP50 Beadchip and the effective population size (Ne) was estimated using SMC++. The genetic characteristics of PRS were analyzed by integrated haplotype score (iHS) and fixation index (F _ST ). The result showed that r ² of PRS was 0.233 ± 0.280 in the range of 0-10 Kb and decreased with increasing distances. SMC++ tested that the Ne of PRS remained at 236.99 in recent generations. 184 genes were screened out under iHS 1% threshold, and 1148 genes were screened out with F _ST under the 5% threshold, and 29 genes were obtained from the intersection of the two gene sets. In this study, the genetic characteristics of PRS and QR were compared by ovine genome chip, and the related excellent genes were searched, providing reference for the protection of sheep germplasm resources and molecular breeding in a desert environment.

High body energy reserve influences extracellular vesicles miRNA contents within the ovarian follicle

Aiming to evaluate the effects of increased body energy reserve (BER) in Nellore cows' reproductive efficiency, cows were fed with different nutritional plans to obtain animals with high BER (HBER; Ad libitum diet) and moderate BER (MBER: cows fed 70% of HBER group ingestion). To evaluate the BER, cows were weekly weighted and evaluated for subcutaneous fat thickness and insulin serum concentration along the experimental period. At the end of the experimental period, animals were submitted to estrous synchronization and artificial insemination. Animals were slaughtered approximately 120 h after ovulation induction and the reproductive tracts were collected for embryo recovery and samples collection. Cumulus-oocyte-complexes (COC) and follicular fluid were collected from 3-6 mm in diameter ovarian follicles to perform miRNA analysis of cumulus cells (CC) and extracellular vesicles from follicular fluid (EV FF). As expected, differences were observed among MBER and HBER groups for body weight, fat thickness, and insulin serum concentration. HBER animals showed lower ovulation and embryo recovery rates compared to MBER animals. Different miRNAs were found among CC and EV FF within groups, suggesting that the BER may influence follicular communication. This suggests that small follicles (3-6 mm diameter) are already under BER effects, which may be greater on later stages of follicular development.

Biomarkers identification in follicular fluid of women with OHSS by using UPLC-MS method

To figure out the differentially changed metabolites and disturbed pathways in follicular fluid (FF) of patients with OHSS in comparison to the control group undergoing in vitro fertilization (IVF), we conducted this metabolomic analysis between two groups, the OHSS group included 30 patients treated with oocyte retrieval and developed OHSS in the next 7-14 days, while another 30 patients without OHSS tendency were selected as the control group. The FF samples were obtained during the process of oocyte retrieval. FF samples were analyzed using ultra-high liquid chromatography-tandem mass spectrometry (UPLC-MS). The results identified a total of 59 differentially changed metabolites, including 33 decreased metabolites (P < 0.01) and 26 increased metabolites (P < 0.01) in FF of OHSS compared with the control group. 12 metabolites could be the most valuable biomarkers for OHSS based on ROC results. Our correlation analyses showed that deoxyinosine levels were found positively correlated with serum estradiol (E2) levels in OHSS patients, while L-isoleucine, pyruvic acid, maleamate, and arachidonic acid were found to be positively correlated with the number of retrieved oocytes. Furthermore, 4-hydroxyphenylacetaldehyde, deoxycorticosterone, creatinine, and creatine were found to be negatively associated with serum E2 levels, while 4-hydroxyphenylacetaldehyde, L-carnitine, isovaleric acid and L-2-hydroxyglutaric acid were negatively related with the number of oocytes retrieved in OHSS patients. Taken together, our study provides better identification of OHSS FF metabolic dynamics, suggesting the metabolic compounds can be used as valuable predictors or treatment targets of OHSS.