Physiological factors underlying the formation of ovarian follicular fluid

Factors defining developmental competence of bovine oocytes collected for in vitro embryo production†

Despite the currently relatively low effectiveness of producing bovine embryos in vitro, there is a growing interest in applying this laboratory method in the field of reproduction. Many aspects of the procedure need to be improved. One of the main problems is the inferior developmental competence of in vitro matured oocytes that are collected using the ovum pick-up method. The mechanisms of oocyte capacitation and maturation, as well as the in vivo conditions in which they grow and mature, should be carefully analyzed. A deliberate application of the identified mechanisms and beneficial factors affecting the in vitro procedures seems to be essential for achieving higher developmental competence of the oocytes that are subjected to fertilization. The results may be improved by developing and employing a laboratory maturation protocol that corresponds with appropriate preparation of donors before the ovum pick-up, an optimized hormonal treatment program, the appropriate size of ovarian follicles at the time of aspiration, and a fine-tuned coasting period.

Fructose improves titanium dioxide nanoparticles induced alterations in developmental competence of mouse oocytes

AIMS

We investigated the effects of intraperitoneal injections of titanium dioxide nanoparticles (TiO2 NPs, 100 mg/kg) for 5 consecutive days on the developmental competence of murine oocytes. Furthermore, study the effects of TiO2 NPs on antioxidant and oxidative stress biomarkers, as well as their effects on expression of apoptotic and hypoxia inducing factor-1α (HIF1A) protein translation. Moreover, the possible ameliorating effects of intraperitoneal injections of fructose (2.75 mM/ml) was examined.

MATERIALS AND METHODS

Thirty sexually mature (8-12 weeks old; ~ 25 g body weight) female mice were used for the current study. The female mice were assigned randomly to three treatment groups: Group1 (G1) mice were injected intraperitoneal (ip) with deionized water for 5 consecutive days; Group 2 (G2) mice were injected ip with TiO2 NPs (100 mg/kg BW) for 5 consecutive days; Group 3 (G3) mice were injected ip with TiO2 NPs (100 mg/kg BW + fructose (2.75 mM) for 5 consecutive days.

RESULTS

Nano-titanium significantly decreased expression of GSH, GPx, and NO, expression of MDA and TAC increased. The rates of MI, MII, GVBD and degenerated oocytes were significantly less for nano-titanium treated mice, but the rate of activated oocytes was significantly greater than those in control oocytes. TiO2 NPs significantly increased expression of apoptotic genes (BAX, Caspase 3 and P53) and HIF1A. Intraperitoneal injection of fructose (2.75 mM/kg) significantly alleviated the detrimental effects of TiO2 NPs. Transmission electron microscopy indicated that fructose mitigated adverse effects of TiO2 NPs to alter the cell surface of murine oocytes.

CONCLUSION

Results of this study suggest that the i/p infusion of fructose for consecutive 5 days enhances development of murine oocytes and decreases toxic effects of TiO2 NPs through positive effects on oxidative and antioxidant biomarkers in cumulus-oocyte complexes and effects to inhibit TiO2-induced increases in expression of apoptotic and hypoxia inducing factors.

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.

Biochemical profiling of the follicular environment to predict oocyte competence in cattle

To identify markers of oocyte competence, we compared the biochemical characteristics of fluid and cells from follicles containing oocytes with different capacities to form an embryo. Follicles (5-6 mm) were dissected, and follicular fluid (FF), granulosa cells (GC), cumulus cells (CC) from immature and mature cumulus-oocyte-complexes (COC) were individually collected. The oocytes were matured, fertilized, and cultured individually until day 8 (D8) of development. On D8, the samples were grouped according to embryo production into those that gave rise to blastocysts (EMB) and those that did not reach the blastocyst stage (NEMB). In CCs from immature and mature COCs and GCs, expression of CASP3, SERPINE2, VCAN, LUM, FSHR, EGFR, PGR, and GHR genes was quantified. Cell-free DNA (cfDNA), progesterone, and estradiol concentrations in the FF were determined. Data were analyzed by Mann-Whitney U test (GraphPad Prism 9). GHR was highly expressed in immature CCs from the EMB group, whereas CASP3 was highly expressed in mature CCs from the NEMB group (P<0.05). During maturation, the expression of CASP3 and GHR genes increased only in the NEMB group. ART2 cfDNA was highly detected in FF of the NEMB compared to the EMB group. Progesterone concentration was similar between the groups, whereas estradiol concentration was higher (P<0.05) in the EMB than in the NEMB group. It was concluded that a higher level of GHR transcripts in immature CCs, lower CASP3 expression in CCs from matured COCs, lower levels of ART2, and higher estradiol concentrations in FF may indicate oocytes with greater potential for development.

Glucose and redox metabolism in meiotically blocked in vitro grown mouse antral follicles

PURPOSE

Glucose and redox metabolism characterization in mouse antral follicles with meiotically blocked oocytes, after in vitro follicle culture (IFC) from the early secondary stage.

METHODS

Following IFC (10 days), oocytes, corresponding cumulus (CC), and granulosa cells (GC) were collected from antral follicles: (i) on day 9-immature, germinal vesicle (GV) stage; (ii) on day 10, after hCG/EGF stimulation-mature, metaphase II (MII) stage and meiotically blocked (MB) immature GV stage. The metabolic profiles of all samples (GV, MII, and MB) were compared by measuring changes in metabolites involved in glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway (PPP), and redox activity via enzymatic spectrophotometric assays in each cell type.

RESULTS

Within MB follicles, GCs drive higher levels of glycolysis and lactic acid fermentation (LAF) while oocytes exert more PPP activity. MB-oocytes had significantly larger diameters compared to day 9 GVs. MB follicles revealed limited metabolic changes in the somatic compartment compared to their GV counterparts (before stimulation). MB-CCs showed increased aconitase and glucose-6-phosphate dehydrogenase activities with lower malate levels comparted to GV-CCs. MB and MII in vitro grown follicles displayed comparable metabolic profiles, suggesting culture induces metabolic exhaustion regardless of the maturation stage.

CONCLUSIONS

Current results suggest that in addition to impaired nuclear maturation, metabolic disruption is present in MB follicles. MB follicles either compensate with high levels of TCA cycle and PPP activities in CCs, or are unable to drive proper levels of aerobic metabolism, which might be due to the current culture conditions.

Increased serum IL-12 levels are associated with adverse IVF outcomes

Interleukin-12 (IL-12) is involved in the occurrence and development of many diseases, such as preeclampsia, intrauterine growth restriction, preterm labor, and recurrent pregnancy losses. This study aimed to determine whether a high serum level of IL-12 was associated with adverse in vitro fertilization (IVF) outcomes. Included infertile women with high serum IL-12 levels who underwent IVF cycles and infertile controls with pure tubal etiology. The impact of serum IL-12 on baseline and clinical characteristics, immune-related indicators, IVF laboratory, and pregnancy outcomes were compared. In addition, the correlation of follicular fluid IL-12 and serum IL-12 level and the role of IL-12 in apoptosis of granulosa cells (GCs) was investigated. Women with high serum IL-12 levels had lower numbers of retrieved oocytes, embryos, perfect and available embryos, lower rates of perfect and available embryos, and blastocyst formation. Additionally, significantly higher levels of serum Th1, Th2, and Th17-related cytokines were observed in women with high serum IL-12 levels than in the controls. Meanwhile, the follicular fluid IL-12 levels were positively correlated with serum IL-12 levels, and IL-12 promoted apoptosis of GCs in vitro. We concluded that women with serum high IL-12 levels may have adverse IVF outcomes, partly by promoting apoptosis of GCs. Therefore, early screening for cytokines, especially IL-12, and appropriate consultation for couples receiving IVF-ET should be considered. In addition, specific immune and inflammatory mechanisms associated with high serum IL-12 levels should be further explored.

Glucocorticoids and Their Receptor Isoforms: Roles in Female Reproduction, Pregnancy, and Foetal Development

Alterations in the hypothalamic-pituitary-adrenal (HPA) axis and associated changes in circulating levels of glucocorticoids are integral to an organism's response to stressful stimuli. Glucocorticoids acting via glucocorticoid receptors (GRs) play a role in fertility, reproduction, placental function, and foetal development. GRs are ubiquitously expressed throughout the female reproductive system and regulate normal reproductive function. Stress-induced glucocorticoids have been shown to inhibit reproduction and affect female gonadal function by suppressing the hypothalamic-pituitary-gonadal (HPG) axis at each level. Furthermore, during pregnancy, a mother's exposure to prenatal stress or external glucocorticoids can result in long-lasting alterations to the foetal HPA and neuroendocrine function. Several GR isoforms generated via alternative splicing or translation initiation from the GR gene have been identified in the mammalian ovary and uterus. The GR isoforms identified include the splice variants, GRα and GRβ, and GRγ and GR-P. Glucocorticoids can exert both stimulatory and inhibitory effects and both pro- and anti-inflammatory functions in the ovary, in vitro. In the placenta, thirteen GR isoforms have been identified in humans, guinea pigs, sheep, rats, and mice, indicating they are conserved across species and may be important in mediating a differential response to stress. Distinctive responses to glucocorticoids, differential birth outcomes in pregnancy complications, and sex-based variations in the response to stress could all potentially be dependent on a particular GR expression pattern. This comprehensive review provides an overview of the structure and function of the GR in relation to female fertility and reproduction and discusses the changes in the GR and glucocorticoid signalling during pregnancy. To generate this overview, an extensive non-systematic literature search was conducted across multiple databases, including PubMed, Web of Science, and Google Scholar, with a focus on original research articles, meta-analyses, and previous review papers addressing the subject. This review integrates the current understanding of GR variants and their roles in glucocorticoid signalling, reproduction, placental function, and foetal growth.

Progesterone and Androstenedione Are Important Follicular Fluid Factors Regulating Porcine Oocyte Maturation Quality

Oocytes matured in vitro are useful for assisted human and farm animal reproduction. However, the quality of in vitro matured oocytes is usually lower than that of in vivo matured oocytes, possibly due to the absence of some important signal regulators in vitro. In this study, untargeted metabolomics was used to detect the changes in the metabolites in the follicular fluid (FF) during in vivo pig oocyte maturation and in the culture medium during in vitro maturation. Our results showed that the total metabolite changing profile of the in vivo FF was different from that of the in vitro maturation medium, but the levels of 23 differentially expressed metabolites (DEMs) changed by following the same trend during both in vivo and in vitro pig oocyte maturation. These 23 metabolites may be important regulators of porcine oocyte maturation. We found that progesterone and androstenedione, two factors in the ovarian steroidogenesis pathway enriched from the DEMs, were upregulated in the FF during in vivo pig oocyte maturation. The levels of these two factors were 31 and 20 fold, respectively, and they were higher in the FF than in the culture medium at the oocyte mature stage. The supplementation of progesterone and androstenedione during in vitro maturation significantly improved the pig oocyte maturation rate and subsequent embryo developmental competence. Our finding suggests that a metabolic abnormality during in vitro pig oocyte maturation affects the quality of the matured oocytes. This study identified some important metabolites that regulate oocyte maturation and their developmental potential, which will be helpful to improve assisted animal and human reproduction.

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.

Perfluoroalkyl Acids in Follicular Fluid and Embryo Quality during IVF: A Prospective IVF Cohort in China

BACKGROUND

Perfluoroalkyl acids (PFAA) have been measured in ovarian follicular fluid from women using in vitro fertilization (IVF), although associations between follicular fluid PFAA and IVF outcomes have been inconsistent.

OBJECTIVES

We investigated the association between follicular fluid PFAA and embryo quality in women undergoing IVF.

METHODS

We prospectively enrolled 729 women undergoing IVF treatment in Guangxi province, China, from July 2018 to December 2018. We measured 32 PFAA, including branched isomers, in follicular fluid using ultra-performance liquid chromatography coupled to tandem mass spectrometry. We applied restricted cubic splines, linear regression, and log-binominal regression models to investigate associations between follicular fluid PFAA and embryo quality, adjusting for confounding variables and investigated oocyte maturity as an intervening variable using causal mediation analysis. We further estimated the overall effect of the PFAA mixture on outcomes using Bayesian kernel machine regression (BKMR).

RESULTS

We detected 8 of 32 measured PFAA in >85% of follicular fluid samples. Higher PFAA concentrations were associated with fewer high-quality embryos from IVF. The high-quality embryo rates at the 50th percentile of linear perfluoro-1-octanesulfonate acid (n-PFOS), all branched PFOS isomers (Br-PFOS) and linear perfluoro-n-octanoic acid (n-PFOA) were -6.34% [95% confidence interval (CI): -9.45, -3.32%], -16.78% (95% CI: -21.98, -11.58%) and -8.66% (95% CI: -11.88, -5.43%) lower, respectively, than the high quality embryo rates at the reference 10th percentile of PFAA. Oocyte maturity mediated 11.76% (95% CI: 3.18, 31.80%) and 14.28% (95% CI: 2.95, 31.27%) of the n-PFOS and n-PFOA associations, respectively. The results of the BKMR models showed a negative association between the PFAA mixture and the probability of high-quality embryos, with branched PFOS isomers having posterior inclusion probabilities of 1 and accounting for the majority of the association.

DISCUSSION

Exposure to higher PFAA concentrations in follicular fluid was associated with poorer embryo quality during IVF. Branched PFOS isomers may have a stronger effect than linear PFOS isomers. More studies are needed to confirm these findings and to directly estimate the effects on pregnancy and live-birth outcomes. https://doi.org/10.1289/EHP10857.

Adenovirus-mediated gene delivery restores fertility in congenitally infertile female mice

Oogenesis depends on close interactions between oocytes and granulosa cells. Abnormal signaling between these cell types can result in infertility. However, attempts to manipulate oocyte-granulosa cell interactions have had limited success, likely due to the blood-follicle barrier (BFB), which prevents the penetration of exogenous materials into ovarian follicles. Here, we used adenoviruses (AVs) to manipulate the oocyte-granulosa cell interactions. AVs penetrated the BFB and transduced granulosa cells through ovarian microinjection. Although AVs caused transient inflammation, they did not impair fertility in wild-type mice. Introduction of Kitl-expressing AVs into congenitally infertile Kitl^Sl-t/Kitl^Sl-t mutant mouse ovaries, which contained only primordial follicles because of a lack of Kitl expression, restored fertility through natural mating. The offspring showed no evidence of AV integration and exhibited normal genomic imprinting patterns for imprinted genes. These results demonstrate the usefulness of AVs for manipulating oogenesis and suggest the possibility of gene therapies for human female infertility.

Characterization of carbohydrate metabolism in in vivo and in vitro grown and matured mouse antral follicles

Establishing an ideal human follicle culture system for oncofertility patients relies mainly on animal models since donor tissue is scarce and often of suboptimal quality. The in vitro system developed in our laboratory supports the growth of prepubertal mouse secondary follicles up to mature oocytes. Given the importance of glucose in preparing the oocyte for proper maturation, a baseline characterization of follicle metabolism both in the culture system and in vivo was carried out. Markers of glucose-related pathways (glycolysis, tricarboxylic acid (TCA) cycle, pentose phosphate pathway (PPP), polyol pathway, hexosamine biosynthesis pathway (HBP)) as well as for the antioxidant capacity were measured in the different follicle cell types by both enzymatic activities (spectrophotometric detection) and gene expression (qPCR). This study confirmed that in vivo the somatic cells, mainly granulosa, exhibit intense glycolytic activity, while oocytes perform PPP. Throughout the final maturation step, oocytes in vivo and in vitro showed steady levels for all the key enzymes and metabolites. On the other hand, ovulation triggers a boost of pyruvate and lactate uptake in cumulus cells in vivo, consumes reduced nicotinamide adenine dinucleotide phosphate (NADPH) and increases TCA cycle and small molecules antioxidant capacity (SMAC) activities, while in vitro, the metabolic upregulation in all the studied pathways is limited. This altered metabolic pattern might be a consequence of cell exhaustion because of culture conditions, impeding cumulus cells to fulfil their role in providing proper support for acquiring oocyte competence. SUMMARY SENTENCE: In vitro cultured mouse follicles exhibit altered glycolytic activity and redox metabolism in the somatic compartment during meiotic maturation.

Adeno-associated-virus-mediated gene delivery to ovaries restores fertility in congenital infertile mice

Oocytes and granulosa cells closely interact with each other during follicular development, and a lack of appropriate signaling between them results in infertility. Attempts to manipulate oocyte microenvironment have been impeded by the impermeability of the blood-follicle barrier (BFB). To establish a strategy for manipulating oogenesis, we use adeno-associated viruses (AAVs), which have a unique ability of transcytosis. Microinjecting of AAVs into the ovarian stroma penetrates the BFB and achieves long-term gene expression. Introduction of an AAV carrying the mouse Kitl gene restores oogenesis in congenitally infertile KitlSl-t/KitlSl-t mutant mouse ovaries, which lack Kitl expression but contain only primordial follicles. Healthy offspring without AAV integration are born by natural mating. Therefore, AAV-mediated gene delivery not only provides a means for studying oocyte-granulosa interactions through the manipulation of the oocyte microenvironment but could also be a powerful method to treat female infertility resulting from somatic cell defects.

Comparison of MicroRNA Profiles in Extracellular Vesicles from Small and Large Goat Follicular Fluid

Simple Summary

Ovarian follicular development is associated with ovulation and is further related to litter size in goats. Extracellular vesicles (EVs) derived from miRNAs within follicular fluid undergo dynamic changes, and, together with follicle growth, may be considered as potential regulators of follicular development. However, the function and changes in EVs remain ambiguous. Here, we identified miRNA changes in EVs from small to large goat follicular fluid. Using bioinformatics tools, we demonstrated the existence of differentially expressed miRNAs in EVs from follicles of different sizes that are responsible for an altered biological effect. This study contributes to a better understanding of follicular development in goats.

Abstract

Extracellular vesicles (EVs), which exist in the follicular fluid of ruminant ovaries, are considered as cargo carriers for the transfer of biomolecules to recipient cells. However, the functions and changes in EVs in antral follicles remain ambiguous. In the present study, we isolated and characterized EVs from goat follicular fluid by means of differential ultracentrifugation and Western blotting of marker proteins. Bioinformatics tools were used to detect miRNA expression levels in EVs. Different miRNA expression patterns of EVs exist in small to large follicles. Thirteen differentially expressed miRNAs (seven upregulated and six downregulated) were identified and used for analysis. A total of 1948 predicted target genes of 13 miRNAs were mapped to signaling pathways, and three significantly enriched pathways (FoxO, MAPK, and PI3K-AKT signaling pathways) were involved in follicular development, as revealed by KEGG enrichment analysis. Our findings suggest that EVs in follicular fluid play biofunctional roles during follicular development in goats.

Spatiotemporal expression of aquaporin 9 is critical for the antral growth of mouse ovarian follicles†

Although a few aquaporins (AQPs) expressed in granulosa cells have been postulated to mediate fluid passage into the antrum, the specific expression of AQPs in different follicle cell types and stages and their roles have not been evaluated extensively. The spatiotemporal expression of aquaporin (Aqp) 7, 8, and 9 and the functional roles of Aqp9 in antral growth and ovulation were examined using a superovulation model and 3-dimensional follicle culture. Aqp9 was expressed at a high level in the rapid growth phase (24-48 h post equine chorionic gonadotropin (eCG) for superovulation induction) compared to Aqp7 (after human chorionic gonadotropin (hCG)) and Aqp8 (8-24 h post eCG and 24 h post hCG). A dramatic increase in the expression and localization of Aqp9 mRNA in theca cells was observed, as evaluated using quantitative reverse transcription-polymerase (RT-PCR) coupled with laser capture microdissection and immunohistochemistry. AQP9 was located primarily on the theca cells of the tertiary and preovulatory follicles but not on the ovulated follicles. In phloretin-treated mice, the diameter of the preovulatory follicles and the number of ovulated oocytes decreased. Consistent with these findings, knocking down Aqp9 expression with an Aqp9 siRNA inhibited follicle growth (0.28:1 = siRNA:control) and decreased the number of ovulated follicles (0.36:1 = siRNA:control) during in vitro growth and ovulation induction. Based on these results, the expression of AQPs is under the control of the physiological status, and AQP9 expression in theca during folliculogenesis is required for antral growth and ovulation in a tissue-specific and stage-dependent manner.

Correlation between Pre-Ovulatory Follicle Diameter and Follicular Fluid Metabolome Profiles in Lactating Beef Cows

Induced ovulation of small pre-ovulatory follicles reduced pregnancy rates, embryo survival, day seven embryo quality, and successful embryo cleavage in beef cows undergoing fixed-time artificial insemination. RNA-sequencing of oocytes and associated cumulus cells collected from pre-ovulatory follicles 23 h after gonadotropin-releasing hormone (GnRH) administration to induce the pre-ovulatory gonadotropin surge suggested reduced capacity for glucose metabolism in cumulus cells of follicles ≤11.7 mm. We hypothesized that the follicular fluid metabolome influences metabolic capacity of the cumulus-oocyte complex and contributes to reduced embryo cleavage and quality grade observed following induced ovulation of small follicles. Therefore, we performed a study to determine the correlation between pre-ovulatory follicle diameter and follicular fluid metabolome profiles in lactating beef cows (Angus, n = 130). We synchronized the development of a pre-ovulatory follicle and collected the follicular contents approximately 20 h after GnRH administration. We then performed ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) metabolomic studies on 43 follicular fluid samples and identified 38 metabolites within pre-ovulatory follicles of increasing size. We detected 18 metabolites with a significant, positive correlation to follicle diameter. Individual and pathway enrichment analysis of significantly correlated metabolites suggest that altered glucose and amino acid metabolism likely contribute to reduced developmental competence of oocytes when small pre-ovulatory follicles undergo induced ovulation.

Silica encapsulation of ZnO nanoparticles reduces their toxicity for cumulus cell-oocyte-complex expansion

Background

Metal oxide nanoparticles (NPs) are increasingly used in many industrial and biomedical applications, hence their impact on occupational and public health has become a concern. In recent years, interest on the effect that exposure to NPs may exert on human reproduction has grown, however data are still scant. In the present work, we investigated whether different metal oxide NPs interfere with mouse cumulus cell-oocyte complex (COC) expansion.

Methods

Mouse COCs from pre-ovulatory follicles were cultured in vitro in the presence of various concentrations of two types of TiO₂ NPs (JRC NM-103 and NM-104) and four types of ZnO NPs (JRC NM-110, NM-111, and in-house prepared uncoated and SiO₂-coated NPs) and the organization of a muco-elastic extracellular matrix by cumulus cells during the process named cumulus expansion was investigated.

Results

We show that COC expansion was not affected by the presence of both types of TiO₂ NPs at all tested doses, while ZnO NM-110 and NM-111 induced strong toxicity and inhibited COCs expansion at relatively low concentration. Medium conditioned by these NPs showed lower toxicity, suggesting that, beside ion release, inhibition of COC expansion also depends on NPs per se. To further elucidate this, we compared COC expansion in the presence of uncoated or SiO₂-coated NPs. Differently from the uncoated NPs, SiO₂-coated NPs underwent slower dissolution, were not internalized by the cells, and showed an overall lower toxicity. Gene expression analysis demonstrated that ZnO NPs, but not SiO₂-coated ZnO NPs, affected the expression of genes fundamental for COC expansion. Dosimetry analysis revealed that the delivered-to-cell mass fractions for both NPs was very low.

Conclusions

Altogether, these results suggest that chemical composition, dissolution, and cell internalization are all responsible for the adverse effects of the tested NPs and support the importance of a tailored, safer-by-design production of NPs to reduce toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00424-z.

Different expression and localization of aquaporin 7 and aquaporin 9 in granulosa cells, oocytes, and embryos of patients with polycystic ovary syndrome and the negatively correlated relationship with insulin regulation

OBJECTIVE

To investigate the expression of aquaporin 7 (AQP7) and aquaporin 9 (AQP9) in the granulosa cells of patients with polycystic ovary syndrome (PCOS) and healthy women and detect their localization in oocytes at the germinal vesicle (GV), metaphase I (MI), MII, embryo, and blastocyst stages and the in vitro response to insulin stimulation.

DESIGN

Randomized, assessor-blinded study.

SETTING

Reproductive medical center.

PATIENT(S)

A total of 40 women (aged 20-38 years) comprising 29 cases of primary infertility and 11 cases of secondary infertility, of whom 17 had an initial diagnosis of PCOS and three received a PCOS diagnosis after an infertility examination.

INTERVENTION(S)

Controlling different concentrations of insulin and different treatment times in cultures of normal human granulosa cells in vitro.

MAIN OUTCOME MEASURE(S)

Expression of AQP7 and AQP9 genes and proteins in granulosa cells detected by real-time quantitative polymerase chain reaction, and localization in oocytes at the GV, MI, MII, embryo, and blastocyst stages by Western blot, immunohistochemical, and immunofluorescence assays, and concentrations of insulin in follicular fluid by enzyme-linked immunosorbent assay.

RESULT(S)

The expression levels of the AQP7 mRNA and protein in the granulosa cells of patients with PCOS were higher than found in healthy controls. We found AQP7 protein expressed in human oocytes at GV, MI, MII, embryo, and blastocyst stages; it was mainly located in the nucleoplasm. In the PCOS group, the expression level of AQP9 mRNA and protein in granulosa cells was lower, and AQP9 protein was expressed in oocytes at the GV, MI, MII, embryo, and blastocyst stages; it was localized on the nuclear membrane. Compared with healthy women, the insulin expression in patients with PCOS was higher. In cultures of normal human granulosa cells in vitro, the expression of AQP7 and AQP9 mRNA and protein decreased with the increase in insulin concentration; expression statistically significantly decreased when the insulin concentration was 100 nmol/L, and after 6 to 24 hours of exposure the lowest expression levels were found at 12 hours.

CONCLUSION(S)

The different localization and expression of AQP7 and AQP9 between the two groups suggests that they might be involved in oocyte maturation and embryonic development through different regulatory pathways. The expression levels of AQP7 and AQP9 were negatively correlated with insulin regulation, suggesting that insulin might affect the maturation of PCOS follicles by changing AQP7 and AQP9 expression.

Toxic elements in follicular fluid adversely influence the likelihood of pregnancy and live birth in women undergoing IVF

STUDY QUESTION

Are follicular fluid (FF), arsenic (As), mercury (Hg), cadmium (Cd) and lead (Pb) concentrations associated with IVF outcomes among women undergoing IVF?

SUMMARY ANSWER

There was a non-linear association between higher FF Hg concentration and a lower likelihood of biochemical pregnancy and live birth. Higher FF Pb concentration was also associated with a lower probability of live birth.

WHAT IS KNOWN ALREADY

Previous research suggests that toxic elements may affect fertility among couples conceiving with and without assistance. However, the results have been inconsistent, possibly related in part to exposure misclassification. Very few studies have used ovarian FF to measure toxic elements, as it requires an invasive collection procedure, yet it may offer a more accurate estimate of a biologically effective dose than blood or urine.

STUDY DESIGN SIZE DURATION

This is a prospective study of 56 women undergoing IVF, from October 2015 to June 2017. FF was collected for analysis on the day of oocyte retrieval.

PARTICIPANTS/MATERIALS SETTING METHODS

As, Cd, Hg and Pb were determined in 197 FF specimens, using inductively coupled plasma tandem mass spectrometry. FF glutathione peroxidase, glutathione reductase, total glutathione-S-transferase, superoxide dismutase, arylesterase and paraoxonase (PON1p) activities were measured using kinetic enzyme assays.

MAIN RESULTS AND THE ROLE OF CHANCE

Non-linear associations were detected, in which the probabilities of biochemical pregnancy (P = 0.05) and live birth (P = 0.05) were lower in association with FF Hg greater than ∼0.51 µg/l Hg, adjusted for age, race, cigarette smoking and recent seafood consumption. Higher FF Pb was also associated with a lower likelihood of live birth (relative risk (RR) = 0.68, 95% CI: 0.46, 1.00; P = 0.05). We also found a suggestive, although imprecise, antagonizing mediating effect of PON1p activity on the association between FF Pb and live birth (-28.3%; 95% CI: -358%, 270%).

LIMITATIONS REASONS FOR CAUTION

The results should be interpreted judiciously given the limited sample size and difficulty accounting for correlated data in generalized additive models and mediation analyses. Additionally, women undergoing IVF are highly selected with respect to age and socioeconomic status, and so the generalizability of the results may be limited.

WIDER IMPLICATIONS OF THE FINDINGS

Overall, the results suggest that FF Hg was associated with a lower likelihood of biochemical pregnancy and live birth, with a potential threshold effect, and that higher FF Pb was associated with a lower probability of live birth. These results may help to guide clinical recommendations for limiting the exposure of patients to Hg and Pb and ultimately improve IVF success rates.

STUDY FUNDING/COMPETING INTERESTS

This work was funded in part by the National Institute of Environmental Health Sciences (NIEHS), grant number 1R56ES023886-01, to the University at Albany (M.S.B.), and in part by the National Institute of Environmental Health Sciences (NIEHS), grant number 1U2CES026542-01, to the Wadsworth Center (P.J.P.). The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

The follicular fluid metabolome differs according to the endometriosis phenotype

RESEARCH QUESTION

Is there a follicular fluid-specific metabolic profile in deep infiltrating endometriosis (DIE) depending on the presence of an associated ovarian endometrioma (OMA) that could lead to the identification of biomarkers for diagnosis and prognosis of the disease?

DESIGN

In this prospective cohort study, proton nuclear magnetic resonance (¹H-NMR) experiments were carried out on 50 follicular fluid samples from patients presenting with DIE, associated or not associated with an OMA, and 29 follicular fluid samples from patients with infertility caused by a tubal obstruction.

RESULTS

Concentrations of glucose, citrate, creatine and amino acids such as tyrosine and alanine were lower in women with DIE than control participants, whereas concentrations of lactate, pyruvate, lipids and ketone bodies were higher. Metabolic analysis revealed enhanced concentrations of glycerol and ketone bodies in patients with OMA, indicative of an activation of lipolysis followed by beta-oxidation. Concentrations of lactate and pyruvate were increased in patients without OMA, whereas the concentration of glucose was decreased, highlighting activation of the anaerobic glycolysis pathway. Differences in concentrations of amino acids such as threonine and glutamine were also statistically relevant in discriminating between the presence or absence of OMA.

CONCLUSIONS

Results indicate a mitochondrial dysregulation in endometriosis phenotypes, with a modified balance between anaerobic glycolysis and beta-oxidation in OMA phenotypes that could affect the fertility of women with endometriosis. As the composition of the follicular fluid has been shown to be correlated with oocyte development and outcome of implantation after fertilization, these findings may help explain the high level of infertility in these patients.

Seafood consumption is associated with higher follicular fluid arsenic (As) and mercury (Hg) concentrations in women undergoing in vitro fertilization (IVF)

Human exposure to non-essential toxic metals such as cadmium (Cd), mercury (Hg), and lead (Pb), and metalloids such as arsenic (As) commonly occurs through diet. Toxic trace element exposures have been reported in association with fertility and fecundity in epidemiologic studies even at low to moderate levels. While most previous studies employed blood and urine biomarkers of exposure, few have assessed toxic trace elements in ovarian follicular fluid (FF), which surrounds the developing oocyte and hence may better reflect concentrations potentially affecting reproductive outcomes. Our objective was to identify dietary predictors of FF toxic trace elements in n = 56 women (mean age: 38.3 years) undergoing in vitro fertilization (IVF) at the University of California at San Francisco. We determined As, Hg, Cd, and Pb in 197 FF specimens, collected on the day of oocyte retrieval, using inductively coupled plasma tandem mass spectrometry. A comprehensive food frequency questionnaire was used to assess the weekly and annual dietary "patterns" of participants. Consumption of specific seafood items and turkey were correlated with individual FF toxic trace elements. We also found that each unit higher seafood consumption in the past week dominated by mollusks, shrimp, and bass was associated with 60% higher FF As (95% confidence interval (CI): 25%, 105%) and FF Hg (95%CI: 7%, 136%) concentrations. Higher annual seafood consumption dominated by urchin, crab, and trout was associated with 16% higher FF As (95%CI: -2%, 38%) and 31% higher FF Hg (95%CI: 7%, 60%) concentrations per unit intake. No associations were noted between diet and Cd and Pb levels in FF. Overall, our results suggest that higher seafood consumption contributes to elevated levels of As and Hg in FF. These findings are consistent with previous IVF studies that assessed toxic trace element exposures in blood and urine. To our knowledge, this is the first study to report that diet might be a source of As, Hg, Cd, and Pb in FF.

Proteome changes of porcine follicular fluid during follicle development

Background

Ovarian follicular fluid influences follicle and oocyte growth, but the fluctuation of its protein content during folliculogenesis has not been comprehensively analyzed. Here we used a shotgun approach and bioinformatics analyses to investigate and compare the proteomes of porcine follicular fluid (pFF) obtained from small (< 4 mm), medium (4–6 mm) and large (> 6–12 mm) follicles.

Results

Follicular fluid samples containing highest estrogen levels were selected as non-atretic from small (SNA: 26.1 ± 15 ng/mL), medium (MNA: 162 ± 54 ng/mL), and large (LNA: 290 ± 37 ng/mL) follicles for proteomic analyses. We detected 1627, 1699, and 1756 proteins in SNA, MNA, and LNA samples, respectively. Nearly 60–63% of total proteins were specific to each sample, 11–13% were shared in pairwise comparisons, and 247 proteins were shared among all samples. Functional categorization indicated comparable gene ontology (GO) terms distribution per cellular component, molecular function, and biological process categories across samples; however, the ranking of highly significantly enriched GO terms per category revealed differences between samples. The patterns of protein-to-protein interactions varied throughout follicle development, and proteins such as serine protease inhibitor, clade E (SERPINE); plasminogen activator, urokinase (PLAU); and plasminogen activator, urokinase receptor (PLAUR) appeared stage-specific to SNA, MNA, and LNA, respectively. The “complement and coagulation cascades” was the common major pathway. Besides, properdin and fibulin-1 were abundant proteins that appeared absent in LNA samples.

Conclusion

This study provides extensive and functional analyses of the pFF proteome changes during folliculogenesis and offers the potential for novel biomarker discovery in pFF for oocyte quality assessment.

S100-A9 protein in exosomes derived from follicular fluid promotes inflammation via activation of NF-κB pathway in polycystic ovary syndrome

Exosomes have recently emerged as key mediators of different physiological and pathological processes. However, there has been few report about proteomic analysis of exosomes derived from human follicular fluid and their association with the occurrence of PCOS. Herein, we used TMT‐tagged quantitative proteomic approach to identify proteomic profiles in exosomes derived from follicular fluid of PCOS patients and healthy controls. We identified 662 proteins in exosomes derived from human ovarian follicular fluid. Eighty‐six differently expressed proteins (P < .05) were found between PCOS and healthy women. The alterations in the proteomic profile were related to the inflammation process, reactive oxygen species metabolic process, cell migration and proliferation. Importantly, we observed that follicular fluid exosomes contain S100 calcium‐binding protein A9 (S100‐A9) protein. Exosome‐enriched S100‐A9 significantly enhanced inflammation and disrupted steroidogenesis via activation of nuclear factor kappa B (NF‐κB) signalling pathway. These data demonstrate that exosomal proteins are differentially expressed in follicular fluid during disease process, and some proteins may play important roles in the regulation of granulosa cell function. These results highlight the importance of exosomes as extracellular communicators in ovarian follicular development.

Metabolite profile and elemental determination of camel follicular fluid by GC-MS and ICP-MS

The objective of present study was to determine metabolite profile and inorganic elements of camel follicular fluids (FF) using "gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma mass spectrometry (ICP-MS)," respectively. Various metabolites were detected in camel FF by the proposed GC-MS technique. The major compounds detected were lactic acid (62.37%), linolenic acid (5.95%), myo-inositol (3.37%), hexadecanoic acid (3.19%), N-ethyl-N-vinylacetamide (3.15%), acetamide (2.89%), tetradecanoic acid (2.64%), and D-xylofuranose (2.25%). The proposed ICP-MS technique was validated in terms of linearity, precision, accuracy, and sensitivity. All quality control validation parameters were found to be satisfactory for the analysis of elements in camel FF. The proposed ICP-MS technique showed the presence of sixteen different elements (out of eighteen standards) in camel FF. Some elements such as Na, K, Ca, and Mg were obtained in higher amounts in camel FF. Overall, the results of this study indicated that the proposed GC-MS and ICP-MS techniques can be successfully applied for metabolite profile and element determination of biological fluids such as FF.

An overview on how cumulus cells interact with the oocyte in a condition with elevated NEFA levels in dairy cows

Metabolic stress in humans and animals is associated with impaired fertility. A major characteristic of metabolic stress is elevated levels of free fatty acids (NEFAs) in blood due to mobilization of body fat reserves. Dairy cows undergo a period of metabolic stress during the peri-calving period, the so-called negative energy balance (NEB) in the early weeks postpartum. At the time of NEB, both saturated and unsaturated NEFAs are mobilized to serve as an alternative energy supply for cells, however in particular saturated NEFAs can have a detrimental effect on somatic cells. Circulating NEFAs are also reflected in the follicular fluid of ovarian follicles and hence reach the cumulus-oocyte-complex (COC), which implies a potential risk for the developing oocyte. To this end, the current review focusses on the impact of NEFAs on the quality of the oocyte.

Effect of aquaporin 3 knockdown by RNA interference on antrum formation in sheep secondary follicles cultured in vitro

SummaryThe objectives were to develop an effective protocol for transfection of ovine secondary follicles and to assess the effect of attenuating aquaporin 3 (AQP3) using a small interfering RNA (siRNA-AQP3) on antrum formation and follicular growth in vitro. Various combinations of Lipofectamine® volumes (0.5, 0.75 or 1.0 µl), fluorescent oligonucleotide (BLOCK-iT ™) concentrations (3.18, 27.12 or 36.16 nM) and exposure times (12, 14, 16, 18 or 20 h) were tested. The BLOCK-iT™ was replaced by siRNA-AQP3 in the transfection complex. Ovine secondary follicles were isolated and cultured in vitro for 6 days using standard protocols. Follicles were transfected on day 0 or 3 or on both days (0 and 3) and then cultured for an additional 3 or 6 days. As revealed by the fluorescence signal, the Lipofectamine®/BLOCK-iT™ complex (0.75 µl + 27.12 nM by 12 h of incubation) crossed the basement membrane and granulosa cell and reached the oocytes. In general, the rate of intact follicles was higher and the rate of antrum formation was lower in transfected follicles compared with control follicles. In conclusion, ovine secondary follicles can be successfully transfected during in vitro culture, and siRNA-mediated attenuation of AQP3 gene reduced antrum formation of secondary follicles.

Oral propylene glycol modifies follicular fluid and gene expression profiles in cumulus-oocyte complexes and embryos in feed-restricted heifers

Dietary supplementation with propylene glycol (PG) increases in vitro production of high-quality embryos in feed-restricted heifers. The aim of the present study was to evaluate the effects of PG in feed-restricted heifers on follicular fluid insulin and insulin-like growth factor (IGF) 1 concentrations, expression of IGF system genes in oocytes and cumulus cells and the expression of selected genes in blastocysts. Feed-restricted (R) heifers were drenched with water or PG during induced oestrous cycles (400mL of PG or water/drench, daily drenching at 1600 hours for the first 9 days of the oestrous cycle). Ovum pick-up (OPU) was performed after superovulation to produce in vitro embryos and without superovulation to recover oocytes, cumulus cells and follicular fluid. OPU was also performed in a control group (not feed restricted and no drenching). Follicular fluid IGF1 concentrations were reduced by R, and PG restored IGF1 concentrations to those seen in the control group. In cumulus cells, expression of IGF1, IGF1 receptor (IGF1R) and IGF binding protein 4 (IGFBP4) was decreased in the R group, and fully (IGF1 and IGF1R) or partially (IGFBP4) restored to control levels by PG. Blastocyst perilipin 2 (PLIN2; also known as adipophilin), Bcl-2-associated X protein (BAX), SCL2A1 (facilitated glucose/fructose transporter GLUT1), aquaporin 3 (AQP3), DNA (cytosine-5)-methyltransferase 3A (DNMT3A) and heat shock 70-kDa protein 9 (HSPA9B) expression were decreased in R heifers; PG restored the expression of the last four genes to control levels. In conclusion, these results suggest that, during follicular growth, PG exerts epigenetic regulatory effects on gene expression in blastocyst stage embryos.

Increased Formation of Follicular Antrum in Aquaporin-8-Deficient Mice Is Due to Defective Proliferation and Migration, and Not Steroidogenesis of Granulosa Cells

Aquaporin-8 (AQP8) is a water channel protein expressed exclusively in granulosa cells (GCs) in mouse ovary. Our previous studies of AQP8-deficient (AQP8^-/-) mice demonstrated that AQP8 participates in folliculogenesis, including in the formation of follicles, ovulation, and atresia. However, its physiological function in formation of the antral follicle is still largely unknown. In the present study, we observed significantly increased numbers of antral follicles in AQP8^-/- ovaries as well as significantly increased follicular antrum formation in in vitro 3D culture of AQP8^-/- follicles. Functional detection of AQP8^-/- GCs indicated that cell proliferation is impaired with FSH treatment, and wound healing and Transwell migration are also impaired with or without FSH treatment, compared with that in WT. However, the biosynthesis of estradiol and progesterone as well as the mRNA levels of key steroidogenic enzyme genes (CYP19A1 and StAR) in AQP8^-/- GCs did not change, even with addition of FSH and/or testosterone. In order to estimate the influence of the impaired proliferation and migration on the density of GC mass, preantral follicles were injected with FITC-dextran, which distributes only in the intercellular space, and analyzed by confocal microscopy. The micrographs showed significantly higher transmission of fluorescence in AQP8^-/- follicles, suggesting increased intercellular space of GCs. Based on this evidence, we concluded that AQP8 deficiency leads to increased formation of follicular antra in vivo and in vitro, and the mechanism may be associated with increased intercellular space of GCs, which may be caused by defective proliferation and migration of GCs. This study may offer new insight into the molecular mechanisms of the formation of follicular antrum.

GDF9 and BMP15 induce development of antrum-like structures by bovine granulosa cells without oocytes

The role of oocytes in follicular antrum formation is not well understood. We examined the effect of oocyte-derived growth factors, growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), on the formation of antrum-like structures by cultured bovine oocyte-granulosa cell complexes (OGCs). OGCs containing growing oocytes (105‒115 µm in diameter) were collected from early antral follicles (1.2‒1.8 mm) and used to prepare oocytectomized complexes (OXCs) and granulosa cell complexes (GCs). The mRNAs of GDF9 and BMP15 were expressed in the oocytes, but not in the granulosa cells. The complexes were cultured for five days with or without GDF9 and BMP15 either alone or in combination. The OGCs maintained their complex integrity and developed antrum-like structure, whereas OXCs and GCs neither maintained their integrity nor developed any antrum-like structure without growth factors. GDF9 or BMP15 alone increased the integrity of these complexes and induced antrum-like structures in OXCs and GCs. Moreover, the combination of GDF9 and BMP15 was more potent for both phenomena in all types of complexes. In OXCs and GCs cultured without GDF9 and BMP15 or with BMP15 alone, outgrowing granulosa cells differentiated into fibroblast-like cells. The combination of GDF9 and BMP15 suppressed the appearance of fibroblast-like cells in OXCs and GCs during incubation. Instead, the granulosa cells appeared rhomboid and pebble-like in shape, similar to those in OGCs cultured without supplementation of GDF9 and BMP15. These results suggest that oocytes maintain complex integrity by preventing granulosa cell differentiation and participate in follicular antrum formation via GDF9 and BMP15.

Impact of Equine and Bovine Oocyte Maturation in Follicular Fluid From Young and Old Mares on Embryo Production in Vitro

Equine follicular fluid (FF) provides autocrine and paracrine factors from theca, granulosa, and cumulus cells, both reflecting and impacting oocyte and follicle maturation. We hypothesized that maturation of oocytes in FF from old versus young mares has a deleterious effect on oocyte maturation and their subsequent developmental potential. Follicular fluid was collected from the large, dominant follicle from young mares (4-13 years) or old mares (21-26 years) and classified as: (1) Noninduced follicular fluid (NFF), FF from noninduced follicle 33 ± 3 mm, or (2) Induced follicular fluid (IFF), FF collected ∼24 hours after administration of ovulation-inducing drugs when a follicle 33 ± 3 mm was observed. In experiment 1, immature equine oocytes were collected, matured in vitro for 30 ± 2 hours in 100% IFF, collected from young or old mares, with the addition of follicle stimulating hormone (5 mU/mL), then fertilized by intracytoplasmic sperm injection. In experiment 2, immature bovine oocytes were collected, matured in 100% IFF or NFF, collected from young mares or old mares, then fertilized via in vitro fertilization. In experiment 1, more blastocysts tended (P = .08) to be produced from equine oocytes that were matured in old versus young mare FF. In experiment 2, when IFF and NFF groups were combined, cleavage rates were higher (P = .001) when bovine oocytes were matured in FF from young than old mares. In contrast to our hypothesis, we observed no conclusive evidence that FF from old mares has a deleterious impact on oocytes and their early developmental potential.

Physiological mechanisms through which heat stress compromises reproduction in pigs

Seasonal variations in environmental temperatures impose added stress on domestic species bred for economically important production traits. These heat-mediated stressors vary on a seasonal, daily, or spatial scale, and negatively impact behavior and reduce feed intake and growth rate, which inevitably lead to reduced herd productivity. The seasonal infertility observed in domestic swine is primarily characterized by depressed reproductive performance, which manifests as delayed puberty onset, reduced farrowing rates, and extended weaning-to-estrus intervals. Understanding the effects of heat stress at the organismal, cellular, and molecular level is a prerequisite to identifying mitigation strategies that should reduce the economic burden of compromised reproduction. In this review, we discuss the effect of heat stress on an animal's ability to maintain homeostasis in multiple systems via several hypothalamic-pituitary-end organ axes. Additionally, we discuss our understanding of epigenetic programming and how hyperthermia experienced in utero influences industry-relevant postnatal phenotypes. Further, we highlight the recent recognized mechanisms by which distant tissues and organs may molecularly communicate via extracellular vesicles, a potentially novel mechanism contributing to the heat-stress response.

A Metabolomic Overview of Follicular Fluid in Cows

Follicular fluid (FF) protects the oocyte against proteolysis and extrusion during ovulation, providing an appropriate microenvironment that favors proper embryonic development; thereby, FF plays a key role in embryo quality. Being directly related to cattle breeding, studying FF is extremely important in livestock science to measure cattle fertility. This may eventually help to assess the quality of both meat and milk, products widely consumed worldwide. There is an important commercial interest in the evaluation and characterization of compounds present in the FF of livestock that present greater likelihood of pregnancy. Mass spectrometry is a great ally for this type of analysis and can provide quick and efficient screening for molecular markers in biological samples. The present study demonstrated the potential of high-resolution mass spectrometry in analyzing FF samples from two distinct groups of Nellore cows (Bos indicus): high and low fertility, as determined by the number of oocytes produced. We were able to delineate markers of interest for each group, which may ultimately be related to biochemical pathways that lead to higher or lower reproductive performance.

Differential Expression of miR-93 and miR-21 in Granulosa Cells and Follicular Fluid of Polycystic Ovary Syndrome Associating with Different Phenotypes

The heterogeneous and multifactorial essence of polycystic ovary syndrome (PCOS) renders a remarkable significance to microRNAs (miRNAs). Normo-androgenic (NA) and hyperandrogenic (HA) PCOS patients were compared with matched healthy women. Expression of miRNAs and TGFβ signaling genes was studied by qRT-PCR and western blotting. Effect of androgen on expression of miR-93 and miR-21 and involvement of androgen receptor were appraised. In granulosa cells (GCs), miR-93 and miR-21 showed significantly increased levels in HA patients compared to NA patients. On the contrary, follicular fluid (FF) levels of both miRNAs were significantly decreased in HA group compared to control women. No significant change in the expression of miRNAs in serum samples was detected. Furthermore, mRNA levels of SMAD7 and TGFBR2 were significantly downregulated in GCs of HA group compared to NA and control subjects. TGFBR2 protein level was significantly decreased in HA patients compared to controls. Free testosterone and free androgen index were positively correlated with expression of miR-93 and miR-21 in GCs of PCOS group. Our findings show distinct molecular signature of different subtypes of PCOS. Intermediary position of miRNAs as androgen responsive factors may play critical role in the pathogenesis of PCOS in hyperandrogenic condition.

Stress and the HPA Axis: Balancing Homeostasis and Fertility

An organism’s reproductive fitness is sensitive to the environment, integrating cues of resource availability, ecological factors, and hazards within its habitat. Events that challenge the environment of an organism activate the central stress response system, which is primarily mediated by the hypothalamic–pituitary–adrenal (HPA) axis. The regulatory functions of the HPA axis govern the cardiovascular and metabolic system, immune functions, behavior, and reproduction. Activation of the HPA axis by various stressors primarily inhibits reproductive function and is able to alter fetal development, imparting a biological record of stress experienced in utero. Clinical studies and experimental data indicate that stress signaling can mediate these effects through direct actions in the brain, gonads, and embryonic tissues. This review focuses on the mechanisms by which stress activation of the HPA axis impacts fertility and fetal development.

Gonadotrophin stimulation in IVF alters the immune cell profile in follicular fluid and the cytokine concentrations in follicular fluid and serum

Study question

Are the immune cell profiles and the cytokine concentrations in follicular fluid (FF) and serum at the preovulatory stage different in conventional exogenous gonadotrophin stimulated IVF (c-IVF) compared with natural cycle IVF (NC-IVF)?

Summary answer

The cell counts of CD45+ leucocytes and T cell subpopulations and the cytokine concentrations in FF and serum are different in c-IVF compared to NC-IVF.

What is known already

FF-derived cells are heterogeneous. Immune cells are involved in intra-ovarian processes and cytokines are required for normal follicular development. Gonadotrophins stimulate the regulatory intrafollicular system and influence the local distribution of immune cells and the intrafollicular release of cytokines. Administration of exogenous gonadotrophins may have a significant effect on this local regulatory system, which then in turn could influence oocyte quality.

Study design, size, duration

The study included 105 patients, 69 undergoing c-IVF and 36 undergoing NC-IVF. c-IVF was performed by exogenous ovarian stimulation with hMG and GnRH antagonists.

Participants/materials, setting, methods

FF samples were collected from the first dominant follicle in c-IVF without pooling and from single leading preovulatory follicles in NC-IVF. Three different approaches were used to analyze FF samples: (i) microscopic investigation of CD45+ leucocytes, (ii) fluorescence-activated cell sorting to determine CD19+ B cells and CD3+ T cells including T cell subpopulations (CD4+, CD8+), and (iii) evaluation of tumour necrosis factor-alpha (TNF-α), interferon-gamma (INF-γ), interleukins (IL)-2, -6, -8, -10 and vascular endothelial growth factor (VEGF) levels in matched FF and serum samples using the Bio-Plex® platform.

Main results and the role of chance

FF obtained from c-IVF contained proportionally more CD45+ leucocytes (P = 0.0384), but fewer CD8+ cytotoxic T cells than FF from NC-IVF. CD3+ T lymphocytes were the most common type of lymphocytes, and the number thereof was comparable in the two study groups. In c-IVF, serum VEGF levels were higher (P = 0.007) than in NC-IVF while FF contained marginally decreased concentrations of IL-8 in c-IVF in comparison to NC-IVF. The cytokine concentration gradient between FF and serum in c-IVF was 10-fold for IL-8 and 8-fold for VEGF and thereby markedly lower than in NC-IVF, where the differences were 32-fold and 30-fold, respectively. Strong positive correlations were determined between FF- IL-10 and FF- VEGF in c-IVF (r = 0.85, P < 0.0001) and in NC-IVF (r = 0.81, P < 0.0001).

Large scale data

N/A.

Limitations, reasons for caution

The ovulation of NC-IVF follicles was induced by the exogenous administration of hCG, which means that the environment did not fully correspond to the physiological situation.

Wider implications of the findings

The differences in the immune profile and the cytokine concentrations in c-IVF and NC-IVF follicles support the hypothesis that conventional ovarian stimulation affects indirectly and heterogeneously the intrafollicular milieu, and thereby possibly affects the oocyte quality and the IVF outcome. However, further studies are needed to confirm our findings and to refine stimulation protocols in the context of optimizing the intrafollicular environment during oocyte maturation.

Study funding/competing interest(s)

The study was supported by a research grant from IBSA Institut Biochimique SA and MSD Merck Sharp & Dohme GmbH. The authors are clinically involved in low dose mono-follicular stimulation and IVF-therapies, using gonadotrophins from all gonadotrophins distributors on the Swiss market, including Institut Biochimique SA and MSD Merck Sharp & Dohme GmbH.

Comparison of PUFA Profiles in the Blood and in Follicular Fluid and its Association with Follicular Dynamics after PGF2α Induced Luteolysis in Dairy Cows

The objectives of the present study were to examine the fatty acid (FA) profiles in serum and in the follicular fluid (FF) and the association between polyunsaturated fatty acid level (PUFA) and follicular growth dynamics following induced luteolysis in dairy cows. A total of 29 dairy cows (CL>25mm, follicle≈15mm) at d0 (start of the experiment) were submitted to ultrasound guided transvaginal follicular aspiration for FF collection from the largest follicle and were injected with 500 μg of cloprostenol. The cows were subdivided into Group A1 (n=11) and Group A2 (n=8) resuming follicular growth either from a secondary follicle less than or larger than 8.5mm, respectively, present at the moment of aspiration and Group A0 (n=10) not resuming follicular growth. Follicular development was monitored daily by ultrasonography until the next dominant follicle reached ≈15mm and was subsequently punctured in Group A1 and A2 (d1). Serum and FF samples for FA determination were taken at d0 from all cows and at d1 in Group A1 and A2. No differences were observed between the FA profile in serum nor in FF between sampling days. Regarding the PUFA levels, the serum linoleic acid (C18:2n6) levels at d0 and d1 were significantly higher than in FF, while alpha linolenic acid (C18:3n3) was lower in the serum than in FF, both at d0 and d1. At d0, a tendency for negative correlation between serum and the FF C18:2n6 with subsequent daily follicular growth rate was observed, while, at d1 there was a strong negative correlation between the serum C18:2n6 and daily growth rate (r=−0.71; p=0.0006). The present study revealed similarities of the FA profiles in the serum and in the FF and association between serum and FF PUFA content with the follicular dynamics after induced luteolysis.

Factors affecting folliculogenesis in ruminants

This review addresses the reasons for the lack of progress in the control of superovulation and highlights the importance of understanding the mechanisms underlying follicular development. The present inability to provide large numbers of viable embryos from selected females still restricts genetic improvement, whilst variability in ovarian response to hormones limit the present capacity for increasing reproductive efficiency.

Females are born with a large store of eggs which rapidly declines as puberty approaches. If these oocytes are normal then there is scope for increasing the reproductive potential of selected females. Oocytes must reach a certain size before they can complete all stages of development and the final changes that occur late in follicular development. It is likely that oocytes that do not produce specific factors at precise stages of development will not be viable. Hence, it is important to characterize oocyte secreted factors since there are potential indicators of oocyte quality.

The mechanisms that determine ovulation rate have still not been fully elucidated. Indeed follicular atresia, the process whereby follicles regress, is still not known. A better understanding of these processes should prove pivotal for the synchronization of follicular growth, for more precise oestrous synchronization and improved superovulatory response.

Nutrition can influence a whole range of reproductive parameters however, the pathways through which nutrition acts have not been fully elucidated. Metabolic hormones, particularly insulin and IGFs, appear to interact with gonadotrophins at the level of the gonads. Certainly gonadotropins provide the primary drive for the growth of follicles in the later stages of development and both insulin and IGF-1, possibly IGF-2, synergize with gonadotrophins to stimulate cell proliferation and hormone production. More research is required to determine the effects of other growth factors and their interaction with gonadotropins.

There is evidence, particularly from studies with rodents, that steroids can also modulate follicular growth and development, although information is very limited for ruminants. There may be a rôle for oestrogens in synchronizing follicular waves, to aid in oestrous synchronization regimes and for removing the dominant follicle to achieve improved superovulatory responses. However more information is required to determine whether these are feasible approaches.

Heritability for litter size is higher in sheep than in cattle. Exogenous gonadotropins are a commercially ineffective means of inducing twinning in sheep and cattle. Although there are differences in circulating gonadotropin concentrations, the mechanism(s) responsible for the high ovulation appear to reside essentially within the ovaries. The locus of the Booroola gene, a major gene for ovulation rate, has been established but not specifically identified. However sheep possessing major genes do provide extremely valuable models for investigating the mechanisms controlling ovulation rate, including a direct contrast to mono-ovulatory species such as cattle.

In conclusion, the relationship between oocyte quality, in both healthy follicles and those follicles destined for atresia, must be resolved before the future potential for increasing embryo yield can be predicted. In addition, a greater understanding of the factors affecting folliculogenesis in ruminants should ensure that the full benefits ensuing from the precise control of ovarian function are achieved. The improved use of artificial insemination and embryo transfer that would ensue from a greater understanding of the processes of folliculo genesis, coupled with the new technologies of genome and linkage mapping, should ensure a more rapid rate of genetic gain.

Intrafollicular interleukin-8, interleukin-12, and adrenomedullin are the promising prognostic markers of oocyte and embryo quality in women with endometriosis

PURPOSE

The study aimed to investigate key intrafollicular prognostic factors among various cytokines and angiogenic molecules for prediction of mature oocytes and good-quality embryos in women with endometriosis undergoing in vitro fertilization (IVF).

METHODS

Paired follicular fluid and serum samples were collected from 200 women with advanced stage endometriosis and 140 normal ovulating women during oocyte retrieval. The concentrations of cytokines (pro-inflammatory: IL-1β, TNF-α, IL-2, IL-8, IL-12, IFN-γ; anti-inflammatory: IL-4, IL-6, IL-10) and angiogenic molecules (vascular endothelial growth factor (VEGF), adrenomedullin, angiogenin) were determined in follicular fluid and serum using ELISA. Expression of these molecules was subjected to multivariate analysis for the identification of major predictive markers of oocyte and embryo quality. Receiver operating characteristic (ROC) curve was applied to determine the best cutoff point for the discrimination between mature and immature oocytes in these women.

RESULTS

Significant increases in levels of cytokines and angiogenic molecules were observed in women with endometriosis compared to controls (P < 0.001). From the validated partial least squares-discriminant analysis (PLS-DA) model, IL-8, IL-12, and adrenomedullin were identified as the most important factors contributing to endometriosis and were negatively associated with oocyte maturity and embryo quality.

CONCLUSION

The levels of IL-8, IL-12, and adrenomedullin may be good indicators of embryo and oocyte quality in endometriosis patients undergoing IVF. Further studies are necessary to ascertain the potential of these markers for oocyte and embryo developmental competence which may help improve the chances of a successful IVF in endometriosis patients.

MicroRNA Species in Follicular Fluid Associating With Polycystic Ovary Syndrome and Related Intermediary Phenotypes

CONTEXT

Polycystic ovary syndrome (PCOS) has a largely unknown etiology and presents with a clinical heterogeneous patient group. Small noncoding microRNA (miRNA) might prove promising as biomarker candidates for PCOS patient stratification. Altered miRNA expression profiles have been observed in few studies.

OBJECTIVE

The aim was to assess the miRNA expression profile in follicular fluid from PCOS patients and healthy, regularly cycling, matched controls.

DESIGN AND SETTING

Experimental case-control study including 49 PCOS women (19 of which were hyperandrogenic and 30 normo-androgenic) and 21 healthy matched women all undergoing in vitro fertilization treatment.

INTERVENTIONS AND MAIN OUTCOME

Anthropometric and relevant clinical baseline measurements were obtained. Relative expression of miRNA levels were estimated using miRNA quantitative PCR arrays and validated by quantitative RT-PCR. Correlation between miRNAs and clinical relevant measurements was estimated.

RESULTS

PCOS women, both normo-androgenic and hyperandrogenic, had decreased levels of miR-24-3p, -29a, -151-3p, and -574-3p compared with controls. Furthermore, miR-518f-3p was differentially expressed within the PCOS group with high levels observed in the hyperandrogenic group compared with the normo-androgenic PCOS patients. Serum levels of total and free T were positively correlated with miR-518f-3p in PCOS subjects (P = .001). Distinction between PCOS and controls could be made using miR-151-3p alone with an area under the curve of 0.91 or a combination of four selected miRNAs (area under the curve, 0.93). Bioinformatic target analysis points to an involvement of these miRNAs in biological pathways involving regulation of cell proliferation, extracellular matrix, and processes in intermediary metabolism.

CONCLUSION

Our study provides evidence that the miRNA expression profile in follicular fluid is altered in PCOS and indicates that specific follicular fluid miRNAs are associated with phenotypical traits of PCOS. An altered miRNA profile holds potentials for new methods of PCOS patient stratification and may contribute to and in part explain the heterogeneous nature found within PCOS women.

Extracellular Vesicles from Bovine Follicular Fluid Support Cumulus Expansion

Expansion of the cumulus complex surrounding the oocyte is critical for ovulation of a fertilizable egg. The ovulation-inducing surge of luteinizing hormone leads to an increased expression of genes such as prostaglandin-endoperoxide synthase 2 (Ptgs2), pentraxin-related protein 3 (Ptx3), and tumor necrosis factor alpha-induced protein 6 (Tnfaip6) that support cumulus expansion. Factors released by mural granulosa and cumulus granulosa cells into the follicular fluid induce paracrine signaling within the follicular compartment. The follicular fluid that separates these distinct granulosa cell types is an enriched fluid containing numerous proteins, nucleic acids, and other macromolecules. Extracellular vesicles (EVs) are also present; however, no physiologically relevant functions of follicular EVs have yet been demonstrated. In our study, the effect of follicular EVs on cumulus-oocyte complex (COC) expansion and relevant gene expression was assayed. Follicular EVs were isolated using ultracentrifugation from follicular fluid of small (3-5 mm) and large (>9 mm) antral bovine follicles, then characterized by nanoparticle tracking analysis, electron microscopy, and Western blot analysis. To test for bioactivity, mouse and bovine COCs were cultured with follicular EVs. Cumulus expansion and Ptgs2, Ptx3, and Tnfaip6 gene expression were measured following COC maturation culture. The results demonstrated that follicular EVs can support both measurable cumulus expansion and increased gene expression.

Biochemical and hormonal analysis of follicular fluid and serum of female dromedary camels (Camelus dromedarius) with different sized ovarian follicles

The current study aimed to compare some biochemical and hormonal constituents in follicular fluids and serum of female dromedary camels with different sized ovarian follicles. Therefore, follicular fluids from follicles sized 1.1-1.5cm (n=10), 1.6-2.1cm (n=10) and 2.2-2.5cm (n=10) and sera were harvested from 20 female camels. The concentrations of ascorbic acid, glucose, cholesterol and activities of acid phosphatase (ACP) and alkaline phosphatase (ALP) were not changed significantly neither in follicular fluids of all follicle sizes nor in sera of female camels with different sized follicles. The concentrations of estradiol-17β (E2) in the follicular fluid of follicles sized 2.2-2.5cm were significantly lower (P<0.01) than its corresponding value in follicular fluid of other follicle sizes. The concentrations of progesterone (P4), tri-iodothyronine (T3), thyroxin (T4), cortisol and insulin-like growth factor-1 (IGF-1) remained comparable in follicular fluids of all examined different sized follicles. The concentrations of E2, P4, T3, T4, cortisol and IGF-1 were similar in the serum of camels with different sized follicles. Interestingly, mean concentrations of P4 and IGF-1 in follicular fluids were higher than their corresponding values in sera of camels with different sized follicles and the mean concentrations of glucose, cholesterol, ALP and cortisol in sera were higher than their corresponding values in follicular fluids of the examined camels. With the exception of E2, there were no significant differences in biochemical and hormonal constituents between follicular fluids from different sized follicles.

Hemato-biochemical and hormonal profiles in post-partum water buffaloes (Bubalus bubalis)

Aim:

The objective of the present study was to compare serum as well as follicular fluid (FF) biochemical and hormonal profiles along with hematological parameters in postpartum estrus, anestrus, and cystic buffaloes.

Materials and Methods:

Postpartum buffaloes were selected in three different groups (within 40-60 days of parturition at estrus-Group-I, postpartum >90 days at anestrum-Group-II, and postpartum cystic buffaloes in Group III). The animals selected were examined for follicular wave dynamics by routine trans-rectal ultrasonography and FF was collected by transvaginal ultrasound-guided ovum pick up technique. All hematological and biochemical parameters were analyzed by automatic analyzers while hormonal profiles analyzed by commercially available ELISA kits.

Results:

In the present investigation, estrum and anestrum animal differ significantly in hemoglobin levels. Serum estradiol differs significantly in estrus and anestrus while no significant difference in progesterone concentration was noted among all three stages. The results of our study suggest that significant higher increase in total protein (TP), calcium and glucose values in estrum while urea, aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase significantly higher in anestrum animals.

Conclusion:

The conclusion of the present study is that TP and albumin, calcium, urea, glucose affects oocyte development and quality.

Physiological consequences of heat stress in pigs

Heat stress negatively influences the global pork industry and undermines genetic, nutritional, management and pharmaceutical advances in management, feed and reproductive efficiency. Specifically, heat stress-induced economic losses result from poor sow performance, reduced and inconsistent growth, decreased carcass quality, mortality, morbidity, and processing issues caused by less rigid adipose tissue (also known as flimsy fat). When environmental conditions exceed the pig’s thermal neutral zone, nutrients are diverted from product synthesis (meat, fetus, milk) to body temperature maintenance thereby compromising efficiency. Unfortunately, genetic selection for both increased litter size and leaner phenotypes decreases pigs’ tolerance to heat, as enhanced fetal development and protein accretion results in increased basal heat production. Additionally, research has demonstrated that in utero heat stress negatively and permanently alters post-natal body temperature and body composition and both variables represent an underappreciated consequence of heat stress. Advances in management (i.e. cooling systems) have partially alleviated the negative impacts of heat stress, but productivity continues to decline during the warm summer months. The detrimental effects of heat stress on animal welfare and production will likely become more of an issue in regions most affected by continued predictions for climate change, with some models forecasting extreme summer conditions in key animal-producing areas of the globe. Therefore, heat stress is likely one of the primary factors limiting profitable animal protein production and will certainly continue to compromise food security (especially in emerging countries) and regionalise pork production in developed countries. Thus, there is an urgent need to have a better understanding of how heat stress reduces animal productivity. Defining the biology of how heat stress jeopardises animal performance is critical in developing approaches (genetic, managerial, nutritional and pharmaceutical) to ameliorate current production issues and improve animal wellbeing and performance.

21-Hydroxylase-derived steroids in follicles of nonobese women undergoing ovarian stimulation for in vitro fertilization (IVF) positively correlate with lipid content of luteinized granulosa cells (LGCs) as a source of cholesterol for steroid synthesis

CONTEXT

Mineralocorticoid synthesis by the nonhuman primate periovulatory follicle enhances luteinization. Whether a similar event occurs in women undergoing in vitro fertilization (IVF) is unknown.

OBJECTIVE

The objective of the study was to determine whether human luteinized granulosa cells (LGCs) produce mineralocorticoids derived from 21-hydroxylase activity and also express mRNA for 21-hydroxylase and the mineralocorticoid receptor.

DESIGN

This was a prospective cohort study.

SETTING

The study was conducted at an academic center.

PATIENTS

LGC lipid content and follicle fluid (FF) hormone analysis was performed on 27 nonobese IVF women. LGCs from six additional nonobese IVF women were used for gene expression studies.

INTERVENTION

At oocyte retrieval, FF was aspirated from the first follicle (≥16 mm in size) of each ovary and pooled LGCs were collected.

MAIN OUTCOME MEASURES

FF steroid analysis was performed by liquid chromatography-tandem mass spectrometry. LGCs were stained with lipid fluorescent dye BODIPY FL C16 to estimate lipid content by confocal microscopy as a cholesterol source for steroidogenesis in vivo. Quantitative real-time PCR was performed using LGCs to detect 21-hydroxylase and mineralocorticoid receptor mRNA expression. Pearson correlation coefficients determined associations between FF steroid levels and LGC lipid content.

RESULTS

FF levels of the 21-hydroxylase-derived steroids, 11-deoxycorticosterone [DOC, 39.97, median (13.94-63.02) ng/mL] and 11-deoxycortisol [11DOC, 2.07 (0.69-5.01) ng/mL], along with the 21-hydroxylase precursor 17-hydroxyprogesterone [1268.21 (493.26-3558.39) ng/mL], positively correlated with LGC lipid content (84 ± 43 fluorescent units/sample) (P ≤ .05, all steroids). 21-Hydroxylase and mineralocorticoid receptor mRNA expression was detected in LGCs.

CONCLUSIONS

Human LGCs likely synthesize 21-hydroxylase-derived mineralocorticoids from cholesterol-containing lipid in vivo to promote postovulatory luteinization via mineralocorticoid receptor-mediated events.