Formation of the ovarian follicular antrum and follicular fluid

Comprehensive immune complexome analysis detects disease-specific immune complex antigens in seminal plasma and follicular fluids derived from infertile men and women

BACKGROUND

Autoimmune reactions and subsequent inflammation may underlie spermatogenic dysfunction and endometriosis-related infertility. The aim of this study is to identify disease-specific antigens in immune complexes (ICs) in seminal plasma (SP) and in follicular fluid (FF).

METHODS

Immune complexome analysis, in which nano-liquid chromatography-tandem mass spectrometry is employed to comprehensively identify antigens incorporated into ICs in biological fluids, was performed for specimens collected from infertile couples undergoing assisted reproduction. Forty-two male patients consisting of subjects with oligozoospermia (n = 6), asthenozoospermia (n = 8), and normal semen analysis (n = 28). Fifty-eight female patients consisting of subjects with ovarian endometriosis (n = 10) and control women without disease (n = 48).

RESULTS

Four disease-specific antigens were identified in subjects with oligozoospermia, while five disease-specific antigens were detected in subjects with asthenozoospermia, some of which are involved in sprematogenesis. Eight antigens were detected only in subjects with endometriosis.

CONCLUSION

Functional characteristics of disease-specific antigens were found to correspond to the pathogenesis of male and female infertility. The formation of ICs may contribute to spermatogenic dysfunction and endometriosis-related infertility via loss of function of the related proteins. Immune complexome analysis is expected to be a valuable tool for the investigation of novel diagnostic methods and treatment strategies for infertility.

Extracellular Vesicles in Human Oogenesis and Implantation

Reproduction, the ability to generate offspring, represents one of the most important biological processes, being essential for the conservation of the species. In mammals, it involves different cell types, tissues and organs, which, by several signaling molecules, coordinate the different events such as gametogenesis, fertilization and embryo development. In the last few years, the role of Extracellular Vesicles, as mediators of cell communication, has been investigated in every phase of these complex processes. Microvesicles and exosomes, identified in the fluid of ovarian follicles during egg maturation, are involved in communication between the developing oocyte and the somatic follicular cells. More recently, it has been demonstrated that, during implantation, Extracellular Vesicles could participate in the complex dialog between the embryo and maternal tissues. In this review, we will focus our attention on extracellular vesicles and their cargo in human female reproduction, mainly underlining the involvement of microRNAs in intercellular communication during the several phases of the reproductive process.

Role of PCSK9 in lipid metabolic disorders and ovarian dysfunction in polycystic ovary syndrome

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a critical role in the cholesterol metabolism by negatively regulating the low-density lipoprotein receptor (LDLR). Lipid metabolic and ovarian disorders are the common clinical manifestation of polycystic ovary syndrome (PCOS). Here, we intended to elucidate the role of PCSK9 in the pathogenesis of PCOS conducted on a human population in case-control design and animal part in an interventional study.

METHODS

We firstly investigated the serum levels of PCSK9 in 46 PCOS patients compared with 49 healthy women as controls, and then developed a PCOS mouse model induced by dehydroepiandrosterone (DHEA) and a high-fat diet (HFD) to determine the role of PCSK9 in abnormal lipid metabolism and ovarian dysfunction of PCOS in four groups (n = 40 per group): control, PCOS mice, PCOS plus alirocumab group, and PCOS plus vehicle group. The expression of PCSK9 in their serum, hepatic and ovarian tissues, serum lipid profiles and hormones were measured. Additionally, mRNA and protein expression levels of LDLR in hepatic and ovarian tissues, ovarian morphology and function were determined. Finally, we used freshly isolated theca-interstitial cells (TICs) and granulosa cells (GCs) from prepubertal normal mice to explore the effect of PCSK9 on LDL uptake of the cells.

RESULTS

Serum PCSK9 concentrations were higher in PCOS patients than normal controls (P < 0.05). The PCOS model mice exhibited significantly increased serum levels of total cholesterol (TC), LDL-C and high-density lipoprotein-cholesterol (HDL-C; P < 0.001, P < 0.001, P = 0.0004, respectively). Moreover, the serum PCSK9 protein level was significantly increased in PCOS mice (P = 0.0002), which positively correlated with serum LDL-C (r = 0.5279, P = 0.0004) and TC (r = 0.4151, P = 0.035). In both liver and ovary of PCOS mice, PCSK9 mRNA and protein levels were significantly increased (P < 0.05), but LDLR levels were significantly decreased (P < 0.05). Furthermore, alirocumab inhibiting PCSK9 partly increased in LDLR expression in both liver and ovary in PCOS mice, also ameliorated the lipid metabolic disorders and pathological changes of ovarian morphology and function and serum reproductive hormones but not in the PCOS plus vehicle group. In vitro experiment, recombinant PCSK9 decreased LDL uptake in TICs and GCs (P < 0.001, P = 0.0011, respectively), which were partly reversed by alirocumab (P < 0.001, P = 0.012, respectively).

CONCLUSION

Abnormal high expression of PCSK9 in the blood, liver and ovary may be involved in the pathogenesis of PCOS by affecting lipid metabolism and ovarian function, and the inhibition of PCSK9 may partly reverse the pathological changes of PCOS. Our research suggests a possibility of PCSK9 as a new attractive target for diagnosis and treatment of PCOS.

Understanding mechanisms of oocyte development by follicular fluid lipidomics

PURPOSE

The present study aimed to provide a non-invasive approach to studying mechanisms responsible for oocyte development.

METHODS

To this end, follicular fluid (FF) from 62 patients undergoing in vitro fertilization (IVF) cycles was split into two groups depending on the pregnancy outcome: pregnant (n = 28) and non-pregnant (n = 34) groups. Data were acquired by the MALDI-TOF mass spectrometry. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were applied to the data set. A ROC curve, to predict success rate, was constructed, and the lipids were attributed.

RESULTS

Six ions were differentially represented in FF of pregnant and non-pregnant patients, with an area under the curve of 0.962. Phosphatidic acid, phosphatidylglycerol, and triacylglycerol were hyper-represented in the pregnant group, while glucosylceramide was hyper-represented in the non-pregnant group. Enriched functions related to these lipids are steroidogenesis, cellular response, signal transduction, cell cycle, and activation of protein kinase C for the pregnant group and apoptosis inhibition for the non-pregnant group.

CONCLUSION

Human FF fingerprinting can both improve the understanding concerning mechanisms responsible for oocyte development and its effect on embryo implantation potential and assist in the management of IVF cycles.

The NADPH oxidase 4 is a major source of hydrogen peroxide in human granulosa-lutein and granulosa tumor cells

H₂O₂ is a reactive oxygen species (ROS), which can diffuse away from its site of generation and may act as a cell-to-cell signaling factor. The mechanisms responsible for the generation of H₂O₂ in human ovarian follicles and possible signaling role(s) of H₂O₂ are not well known. We identified a source of H₂O₂, the enzyme NADPH oxidase (NOX) 4, in isolated differentiated, in-vitro fertilisation-derived human granulosa-lutein cells (GCs), in proliferating human granulosa tumour cells (KGN), as well as in situ in cells of growing ovarian follicles. H₂O₂ was readily detected in the supernatant of cultured GCs and KGN cells. H₂O₂ levels were significantly lowered by the NOX4 blocker GKT137831, indicating a pronounced contribution of NOX4 to overall H₂O₂ generation by these cells. We provide evidence that extracellular H₂O₂ is taken up by GCs, which is facilitated by aquaporins (peroxiporins). We thus conclude that GC-derived H₂O₂ might act as autocrine/paracrine factor. Addition of H₂O₂ increased MAPK-phosphorylation in GCs. Moreover, reducing H₂O₂ production with GKT137831 slowed proliferation of KGN cells. Our results pinpoint NOX4 and H₂O₂ as physiological players in the regulation of GC functions.

Human β-defensin 1 in follicular fluid and semen: impact on fertility

PURPOSE

β-defensins are antimicrobial peptides expressed at mucosal level of male and female genito-urinary tract, where they exert protective functions against infections, possibly preserving human health and fertility. In our study, we investigated the possible involvement of β-defensins in female and male infertility in Italian infertile couples (i) evaluating the presence of human β-defensin 1 (hBD-1) in follicular fluid (FF) and its correlation with in vitro fertilization (IVF) outcomes; (ii) investigating the relationship between hBD-1 levels in semen and IVF outcomes (comprising correlation with sperm parameters); and (iii) exploring the effect of hBD-1 peptide on spermatozoa motility in vitro.

METHODS

A perspective observational analytic pilot study was conducted. hBD-1 concentration was measured with ELISA assay in FF and semen from 50 couples that underwent assisted procreation technique procedures due to infertility status. Moreover, hBD-1 exogenous peptide was administered to 29 normozoospermic semen and their motility was recorded.

RESULTS

hBD-1 was detected in FF and its levels were significantly higher in women with good fertilization rate (≥ 75%), respect to those with a poor fertilization rate (< 75%). The hBD-1 semen concentrations in oligo-asthenozoospermic subjects were significantly lower than that in normozoospermic men. Instead, hBD-1 level in sperm and FF not correlated with pregnancy rate. Finally, incubation of sperm with exogenous hBD-1 significantly increased progressive motility after 1 h and 24 h.

CONCLUSIONS

Being aware of the relatively small sample size and medium power, our results possibly suggest that hBD-1 could influence oocyte and sperm quality, and could improve, when exogenously added, sperm motility.

Urinary concentrations of phenols and phthalate metabolites reflect extracellular vesicle microRNA expression in follicular fluid

BACKGROUND

Phenols and phthalates are potential endocrine disrupting chemicals (EDCs) that are associated with adverse health outcomes. These EDCs dysregulate a number of biomolecules and pathways, including microRNAs. MicroRNAs can be carried in transport systems called extracellular vesicles (EVs) that are present in most biofluids. EVs in the follicular fluid, which fills the ovarian follicle and influences oocyte developmental competency, carry microRNAs (EV-miRNAs) that have been associated with In Vitro Fertilization (IVF) outcomes. However, it remains unclear whether EDCs affect EV-miRNAs in follicular fluid.

OBJECTIVES

This study sought to determine whether urinary concentrations of phenols and phthalates biomarkers are associated with EV-miRNAs expression in follicular fluid collected from women undergoing IVF treatment.

METHODS

This cross-sectional study included 130 women recruited between January 2014 and August 2016 in a tertiary university-affiliated hospital. Participants provided urine samples during ovarian stimulation and on the day of oocyte retrieval. We assessed urinary concentrations of five phenols, eight phthalate metabolites, and one phthalate alternative metabolite. EV-miRNAs were isolated from follicular fluid and their expression profiles were measured using the TaqMan Open Array® Human microRNA panel. We fitted multivariable linear regression models and principal component analysis to examine associations between individual and molar sums of exposure biomarkers and EV-miRNAs.

RESULTS

Of 754 miRNAs tested, we detected 133 EV-miRNAs in the microRNA array which expressed in at least 50% of the follicular fluid samples. After adjusting for multiple testing, we identified eight EV-miRNAs associated with individual phenols and phthalate metabolites, as well as molar ΣDEHP that met a q < 0.10 false-discovery rate (FDR) threshold. Hsa-miR-125b, hsa-miR-106b, hsa-miR-374a, and hsa-miR15b was associated with mono(2-ethylhexyl) phthalate concentrations, hsa-let-7c with concentrations mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-2-ethyl-5-oxohexyl phthalate (MEOHP), mono-2-ethyl-5-carboxypentyl phthalate (MECPP), and the sum of metabolites of di(2-ethylhexyl) phthalate, hsa-miR-24 with mono-n-butyl phthalate concentrations, hsa-miR-19a with cyclohexane-1,2-dicarboxylic acid monohydroxy isononyl ester (MHiNCH), and hsa-miR-375 with ethyl paraben concentrations. Using Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses, gene targets and pathways of these EV-miRNAs were predicted in silico and 17 KEGG FDR-significant pathways related to follicular development and oocyte competence were identified.

CONCLUSIONS

Our results show that urinary concentrations of select phenol and phthalate metabolites are correlated with altered EV-miRNAs expression in follicular fluid. These findings may provide insight regarding the molecular mechanisms underlying adverse effects of phenol and phthalate exposure on female fertility.

Follicle development as an orchestrated signaling network in a 3D organoid

The ovarian follicle is the structural and functional unit of the ovary, composed of the female gamete (the oocyte) and supportive somatic cells. Follicles are not only the source of a female's germ cell supply, but also secrete important hormones necessary for proper endocrine function. Folliculogenesis, the growth and maturation of the follicular unit, is a complex process governed by both intrafollicular crosstalk and pituitary-secreted hormones. While the later stages of this process are gonadotropin-dependent, early folliculogenesis appears to be controlled by the ovarian microenvironment and intrafollicular paracrine and autocrine signaling. In vitro follicle culture remains challenging because of the limited knowledge of growth factors and other cytokines influencing early follicle growth. Here we discuss the current state of knowledge on paracrine and autocrine signaling influencing primary follicles as they develop into the antral stage. Given the importance of intrafollicular signaling and the ovarian microenvironment, we reviewed the current engineering approaches for in vitro follicle culture, including 3D systems using natural hydrogels such as alginate and synthetic hydrogels such as poly(ethylene glycol). Our discussion is focused on what drives the proliferation of granulosa cells, development of the thecal layer, and antrum formation-three processes integral to follicle growth up to the antral stage. Further research in this area may reveal the mechanisms behind these complex signaling relationships within the follicle, leading to more successful and physiologically-relevant in vitro culture methods that will translate well to clinical applications.

Integrated Analysis of mRNA and miRNA Expression Profiles in the Ovary of Oryctolagus cuniculus in Response to Gonadotrophic Stimulation

Molecular mechanisms responsible for gonadotrophic control of ovarian follicle development and ovulation have not been fully delineated. In this study, prepubertal female rabbits were subjected to a combined PMSG/hCG treatment for the induction of follicle maturation and ovulation. Ovaries of 6 does at different time points during gonadotrophic stimulation were collected for histomorphological examination and genome-wide analysis of miRNA and mRNA transcriptomes, and the plasma were separated for detecting melatonin (MT), prostaglandin E₂ (PGE₂), estradiol (E₂), and progesterone (P₄) levels. The results suggested that PMSG promoted the development of the reproductive tract by decreasing plasma levels of E₂ and slightly increasing those of MT and PGE₂ and that hCG induced ovulation and corpus luteum formation by significantly increasing MT, PGE₂, and P₄ levels. At the transcriptomic level, a total of 1,122 differentially expressed genes (DEGs) and 12 DE miRNAs were identified using three-group comparisons. Meanwhile, pairwise comparisons revealed that 279 and 103 genes as well as 36 and 20 miRNAs were up- and down-regulated during PMSG-stimulated follicle development while 11 and 5 genes as well as 33 and 16 miRNAs were up- and down-regulated during hCG-induced luteinization. KEGG enrichment analysis of the DEGs derived from both three-group- and two-group comparisons as well as the predicted target genes of DE miRNAs highlighted the crucial roles of pathways involving tissue remodeling, energy metabolism, and regulation of cellular functions in mediating gonadotrophin-induced follicle maturation. Specifically, 3 genes including the matrix metallopeptidase 13 (MMP13), protein phosphatase 1 regulatory subunit 3C (PPP1R3C), and solute carrier family 2 member 12 (SLC2A12), together with 2 miRNAs including the miR-205-1 and miR-34c, were predicted to be the promising downstream targets of both PMSG and hCG. Significantly, the miRNA-mRNA interaction pairs containing top 10 up- and down-regulated mRNAs/miRNAs upon PMSG/hCG stimulation were established, and so were those involved in the PI3K-Akt, ECM-receptor interaction, and focal adhesion pathways during PMSG-induced follicle maturation. Finally, qRT-PCR analysis confirmed the results from RNA-Seq and Small RNA-Seq. Our work may contribute to a better understanding of the regulatory mechanisms of gonadotrophins on ovarian follicle development and ovulation.

Three-dimensional levitation culture improves in-vitro growth of secondary follicles in bovine model

RESEARCH QUESTION

Does a three-dimensional culture system based on magnetic levitation with nanoparticles assembly maintain the follicular structure and viability with adequate growth rates leading to oocyte maturation after long-term culture?

DESIGN

Randomized-controlled trial of treatments in a bovine model. Secondary follicles (n = 213) isolated from bovine ovaries were cultured in a two-dimensional system (two-dimensional control) or three-dimensional levitation system with different concentrations (three-dimensional 50 µl/ml, 100 µl/ml and 200 µl/ml) of magnetic nanoparticles. Follicular growth (diameter, daily growth and growth patterns), morphology (normal, degenerated and extruded follicles), antrum formation, oocyte viability and chromatin configuration were assessed.

RESULTS

Secondary follicles of three-dimensional 200-µl/ml treatment showed higher viability, antrum formation and lower degeneration rates than two-dimensional control. Also, follicles cultured in the three-dimensional 200-µl/ml treatment presented a most homogenous daily growth rate as shown by the lowest variance and standard deviation. Compared with the two-dimensional control, the proportion of non-growing and slow-growing follicles were 3.8-fold lower and 1.6-fold higher, respectively, in the three-dimensional 200-µl/ml treatment. After in-vitro maturation, the three-dimensional 200-µl/ml had a greater proportion of viable oocytes (1.7-fold) and meiotic resumption rates (2.4-fold) than the two-dimensional control treatment.

CONCLUSION

The three-dimensional levitation culture system improves the viability of in-vitro development of bovine secondary follicles, antrum formation and lower extrusion and degeneration rates and adequate growth rate leading to relevant oocyte viability and meiotic resumption after in-vitro maturation. This approach does not require a specific medium, and has the potential as an alternative method to in-vitro follicle culture in several species, including humans.

Supplementation of in vitro culture medium with FSH to grow follicles and mature oocytes can be replaced by extracts of Justicia insularis

The present study evaluated the effect of supplementing in vitro culture medium with J. insularis compared to FSH on isolated secondary follicles and in vitro maturation of oocytes from those follicles. Secondary follicles were isolated from sheep ovaries and individually cultured for 18 days in α-MEM⁺ (Control), α-MEM⁺ supplemented with 100 ng/mL recombinant bovine follicle stimulating hormone (FSH) or with 0.3, 1.25, or 2.5 mg/mL of J. insularis extract (JI0.3, JI1.25, and JI2.5, respectively). Culture medium collected every 2 days was used to measure ROS levels. At the end of the culture period, cumulus oocytes complex (COCs) were collected and matured in vitro. Follicular walls were used for mRNA quantitation. JI0.3 led to a higher (P < 0.05) percentages of intact follicles than other groups after 18 days of culture. While follicular diameter remained unchanged from Day 6 onwards with JI0.3 and FSH, percentages of antral cavity formation were higher (P < 0.05) with JI0.3 at Day 6 than in all other treatments. No differences were observed between controls and treatment groups regarding ROS levels and mRNA expression of genes. Viability of resulting oocytes was higher (P < 0.05) in JI0.3 compared to FSH. Interestingly, in control experiment, supplementation of maturation medium with JI0.3 led to higher (P < 0.05) percentages of metaphase II compared to controls. Although more validations will be needed, it seems that this natural extract could be used as a cheap and easily available alternative to commercial FSH.

Follicular fluid humanin concentration is related to ovarian reserve markers and clinical pregnancy after IVF-ICSI: a pilot study

RESEARCH QUESTION

Is humanin present in the human ovary and follicular fluid? What relationship exists between humanin concentration in the follicular fluid and ovarian reserve and clinical outcomes after IVF and intracytoplasmic sperm injection (ICSI)?

DESIGN

Follicular fluid samples were collected from 179 patients undergoing their first IVF or ICSI cycle during oocyte retrieval. Ovarian tissues were collected from two patients undergoing surgery for ovarian cysts. Ovarian humanin localization was analysed using immunofluorescence staining. Expression of humanin in granulosa cells was confirmed by reverse transcription polymerase chain reaction (RT-PCR) analysis. Follicular fluid humanin levels were evaluated with enzyme-linked immunosorbent assay. Relationships between follicular fluid humanin levels and ovarian reserve markers and clinical outcomes were analysed.

RESULTS

Strong humanin expression was found in the granulosa cells, oocytes and stromal cells of the ovary. Agarose gel electrophoresis of RT-PCR products showed rich humanin mRNA expression in human granulosa cells (119 bp). Follicular fluid humanin concentrations ranged from 86.40 to 417.60 pg/ml. They significantly correlated with FSH (r = -0.21; P < 0.01), LH (r = -0.18; P = 0.02), antral follicle count (r = 0.27; P < 0.01), anti-Müllerian hormone (r = 0.24; P = 0.03) and inhibin B (r = 0.46; P < 0.01) levels. Patients were subdivided into four groups according to follicular fluid humanin concentration quartiles (Q1-Q4). Patients in Q4 were more likely to achieve a pregnancy than Q1 (OR = 3.60; 95% CI 1.09 to 11.84).

CONCLUSIONS

Humanin concentration in the follicular fluid was positively associated with ovarian reserve and clinical pregnancy rate.

Extracellular microRNAs profile in human follicular fluid and IVF outcomes

Encapsulated microRNAs (i.e., miRNAs within the extracellular vesicles, i.e., EV-miRNAs) have been detected in follicular fluid in both animal and human studies and different profiles have been associated with IVF cycle characteristics. However, limited studies to date have investigated other IVF outcomes, including fertilization status and embryo quality on day three". In this cohort, we performed a cross-sectional analysis on 126 women who contributed follicular fluid from a single follicle during a single IVF cycle. One hundred and ninety-two EV-miRNAs were assessed by univariable fold-change and multivariable logistic regression analyses. Hsa-miR-92a and hsa-miR-130b, were over-expressed in follicular fluid samples from oocytes that failed to fertilize compared to those that were normally fertilized. Additionally, hsa-miR-888 was over-expressed and hsa-miR-214 and hsa-miR-454 were under-expressed in samples that resulted in impaired day-3 embryo quality compared to top-quality day-3 embryos. After adjusting for confounders as BMI, smoking and total motile sperm, associations of these EV-miRNAs remained significant. In-silico KEGG pathway analyses assigned the identified EV-miRNAs to pathways of follicular growth and development, cellular signaling, oocyte meiosis, and ovarian function. Our findings suggest that EV-miRNAs may play a role in pathways of ovarian function and follicle development, which could be essential for understanding the molecular mechanisms that could lead to a successful pregnancy and birth.

The effects and possible mechanisms of triclosan on steroidogenesis in primary rat granulosa cells

BACKGROUND

Triclosan (TCS) has been detected in human tissues. It can disrupt steroidogenesis in vivo. The study on the effects of TCS on ovarian granulosa cells was lacking.

METHODS

Primary rat granulosa cells (rGCs) were treated with TCS. Concentrations of estradiol (E₂), progesterone (P₄) in the cell culture supernatants were measured. Microarray was used to measure gene expression profiles. Pathway analysis was performed to identify signaling networks that linked differentially expressed genes (DEGs). Genes related with steroidogenesis were analyzed.

RESULTS

TCS increased E₂ and P₄ production. A total of 2006 DEGs were identified. Pathway analysis revealed that ovarian steroidogenesis pathway was upregulated. Both PCR and Western-blot demonstrated that the expressions of key genes involved in this pathway were significantly increased.

CONCLUSIONS

TCS co-administered with follicle-stimulating hormone (FSH) could increase E₂ and P₄ production in rGCs and up-regulate ovarian steroidogenesis pathway. StAR and aromatase protein were increased by TCS, while P450scc protein wasn't changed significantly.

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.

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.

Action mechanisms of n-3 polyunsaturated fatty acids on the oocyte maturation and developmental competence: Potential advantages and disadvantages

Infertility is a growing problem worldwide. Currently, in vitro fertilization (IVF) is widely performed to treat infertility. However, a high percentage of IVF cycles fails, due to the poor developmental potential of the retrieved oocyte to generate viable embryos. Fatty acid content of the follicular microenvironment can affect oocyte maturation and the subsequent developmental competence. Saturated and monounsaturated fatty acids are mainly used by follicle components as primary energy sources whereas polyunsaturated fatty acids (PUFAs) play a wide range of roles. A large body of evidence supports the beneficial effects of n-3 PUFAs in prevention, treatment, and amelioration of some pathophysiological conditions including heart diseases, cancer, diabetes, and psychological disorders. Nevertheless, current findings regarding the effects of n-3 PUFAs on reproductive outcomes in general and on oocyte quality more specifically are inconsistent. This review attempts to provide a comprehensive overview of potential molecular mechanisms by which n-3 PUFAs affect oocyte maturation and developmental competence, particularly in the setting of IVF and thereby aims to elucidate the reasons behind current discrepancies around this topic.

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.

The effect of ovarian reserve and receptor signalling on granulosa cell apoptosis during human follicle development

The poor oocyte quality in older women has previously been linked to the depletion of the ovarian reserve of primordial follicles and an increase in granulosal apoptosis. Granulosa cells were collected from 198 follicles and individually analysed by flow cytometry. In the young IVF patients, the level of apoptosis was inversely proportional to the expression of bone morphogenetic protein (BMPR1B) and follicle stimulating hormone (FSH) receptors. Conversely, in the older patients this relationship became dysregulated. In the older patients, at the time of preovulatory maturation, the reduced apoptosis reflects the poor mitogenic growth turnover rate of healthy follicles rather than the death rate in an atretic follicle. Restoring an optimum receptor density and down-regulation of receptors may improve oocyte quality and the pregnancy rate in older women.

Stage-specific follicular extracellular vesicle uptake and regulation of bovine granulosa cell proliferation

Follicular fluid within ovarian antral follicles contains numerous factors, which influence the development of a healthy oocyte including nucleic acids, steroids, proteins, and extracellular vesicles (EVs). Current evidence indicates that follicular EVs promote changes in cellular gene expression and support cumulus-oocyte complex expansion in vitro. In this study, we found EVs from different sized follicles differentially stimulate granulosa cell proliferation and this could be explained by both the differential contents associated, on or within the vesicles and by the preferential uptake of EVs dependent on follicle size from which they were isolated. Antibody array and inhibitor studies indicated that the Src, PI3K/Akt, and MAPK signaling pathways mediate the stimulatory effects of EVs on granulosa cell proliferation. This study demonstrates for the first time that EVs isolated from follicular fluid are capable of stimulating granulosa cell proliferation and that this stimulatory response is associated with the size of antral follicle from which the EVs originated. The study further also provides the first evidence that vesicles released by small antral follicles are preferentially taken up when compared to those isolated from large follicles, suggesting that vesicular surface proteins change during follicular maturation.

Biomechanics and mechanical signaling in the ovary: a systematic review

PURPOSE

Mammalian oogenesis and folliculogenesis share a dynamic connection that is critical for gamete development. For maintenance of quiescence or follicular activation, follicles must respond to soluble signals (growth factors and hormones) and physical stresses, including mechanical forces and osmotic shifts. Likewise, mechanical processes are involved in cortical tension and cell polarity in oocytes. Our objective was to examine the contribution and influence of biomechanical signaling in female mammalian gametogenesis.

METHODS

We performed a systematic review to assess and summarize the effects of mechanical signaling and mechanotransduction in oocyte maturation and folliculogenesis and to explore possible clinical applications. The review identified 2568 publications of which 122 met the inclusion criteria.

RESULTS

The integration of mechanical and cell signaling pathways in gametogenesis is complex. Follicular activation or quiescence are influenced by mechanical signaling through the Hippo and Akt pathways involving the yes-associated protein (YAP), transcriptional coactivator with PDZ-binding motif (TAZ), phosphatase and tensin homolog deleted from chromosome 10 (PTEN) gene, the mammalian target of rapamycin (mTOR), and forkhead box O3 (FOXO3) gene.

CONCLUSIONS

There is overwhelming evidence that mechanical signaling plays a crucial role in development of the ovary, follicle, and oocyte throughout gametogenesis. Emerging data suggest the complexities of mechanotransduction and the biomechanics of oocytes and follicles are integral to understanding of primary ovarian insufficiency, ovarian aging, polycystic ovary syndrome, and applications of fertility preservation.

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.

Presence of growth/differentiation factor-15 cytokine in human follicular fluid, granulosa cells, and oocytes

PURPOSE

The purpose of the study was to determine whether the GDF-15 is present in follicular fluid; to evaluate if there is a relation between follicular and serum levels of GDF-15 and fertility status of study subjects; and to test whether granulosa cells, oocytes, or both produce GDF-15.

METHODS

This study used follicular fluid (FF, serum, and oocytes obtained under informed consent from women undergoing oocyte retrieval for in vitro fertilization. It also used ovaries from deceased preterm newborns. Collection of FF and blood at the time of oocyte retrieval, ELISA and western blot were performed to determine levels and forms of GDF-15. Concentrations of GDF-15 in FF and serum, its expression in ovarian tissue, and secretion from granulosa cells were analyzed.

RESULTS

GDF-15 concentration in FF ranged from 35 to 572 ng/ml, as determined by ELISA. Western blot analysis revealed the GDF-15 pro-dimer only in FF. Both normal healthy and cancerous granulosa cells secreted GDF-15 into culture media. Primary oocytes displayed cytoplasmic GDF-15 positivity in immunostained newborn ovaries, and its expression was also observed in fully grown human oocytes.

CONCLUSIONS

To the best of our knowledge, this is the first documentation of cytokine GDF-15 presence in follicular fluid. Its concentration was not associated with donor/patient fertility status. Our data also show that GDF-15 is expressed and inducible in both normal healthy and cancerous granulosa cells, as well as in oocytes.

Inhibition of PDE3A sustains meiotic arrest and gap junction of bovine growing oocytes in in vitro growth culture

Bovine growing oocytes with a diameter of 105-115 μm from early antral follicles (1.2-1.8 mm) are able to resume meiosis, but lack the competence to mature to metaphase II. To confer full maturation competence onto the oocytes, culture systems which can support their growth and prevent their meiotic resumption during culture are needed. In this study, we cultured growing oocytes for 5 days to examine the effects of different phosphodiesterase (PDE) inhibitors on meiotic arrest and acquisition of full maturation competence of growing oocytes, and their gap junctional communication with cumulus cells. Growing oocyte-cumulus complexes (OCCs) were cultured with 3-isobutyl-1-methylxanthine (IBMX; broad-spectrum PDE inhibitor), rolipram (PDE4D inhibitor), cilostamide and milrinone (PDE3A inhibitors). The mean diameters of oocytes increased similarly in all groups. IBMX, cilostamide and milrinone induced antrum formation by OCCs and maintained meiotic arrest of oocytes during culture, whereas rolipram neither promoted antrum formation nor maintained oocyte meiotic arrest. Gap junctional communication between oocytes and cumulus cells was maintained by IBMX and cilostamide, but not by rolipram as judged by the transfer of injected lucifer yellow dye from oocytes to cumulus cells. In subsequent in vitro maturation, oocytes grown with IBMX, cilostamide and milrinone showed full maturation competence. These results suggest that PDE3A inhibition maintains the meiotic arrest of bovine growing oocytes and sustains their gap junctional communication with cumulus cells for 5 days, thereby contributing to their acquisition of full maturation competence.

Influence of follicular fluid and cumulus cells on oocyte quality: clinical implications

An equilibrium needs to be established by the cellular and acellular components of the ovarian follicle if developmental competence is to be acquired by the oocyte. Both cumulus cells (CCs) and follicular fluid (FF) are critical determinants for oocyte quality. Understanding how CCs and FF influence oocyte quality in the presence of deleterious systemic or pelvic conditions may impact clinical decisions in the course of managing infertility. Given that the functional integrities of FF and CCs are susceptible to concurrent pathological conditions, it is important to understand how pathophysiological factors influence natural fertility and the outcomes of pregnancy arising from the use of assisted reproduction technologies (ARTs). Accordingly, this review discusses the roles of CCs and FF in ensuring oocyte competence and present new insights on pathological conditions that may interfere with oocyte quality by altering the intrafollicular environment.

Involvement of Bone Morphogenetic Proteins (BMP) in the Regulation of Ovarian Function

Primordial germ cells migrate to the fetal gonads and proliferate during gestation to generate a fixed complement of primordial follicles, the so-called ovarian reserve. Primordial follicles comprise an oocyte arrested at the diplotene stage of meiosis, surrounded by a layer of pregranulosa cells. Activation of primordial follicles to grow beyond this arrested stage is of particular interest because, once activated, they are subjected to regulatory mechanisms involved in growth, selection, maturation, and ultimately, ovulation or atresia. The vast majority of follicles succumb to atresia and are permanently lost from the quiescent or growing pool of follicles. The bone morphogenetic proteins (BMPs), together with other intraovarian growth factors, are intimately involved in regulation of follicle recruitment, dominant follicle selection, ovulation, and atresia. Activation of primordial follicles appears to be a continuous process, and the number of small antral follicles at the beginning of the menstrual cycle provides an indirect indication of ovarian reserve. Continued antral follicle development during the follicular phase of the menstrual cycle is driven by follicle stimulating hormone (FSH) and luteinizing hormone (LH) in conjunction with many intraovarian growth factors and inhibitors interrelated in a complex web of regulatory balance. The BMP signaling system has a major intraovarian role in many species, including the human, in the generation of transcription factors that influence proliferation, steroidogenesis, cell differentiation, and maturation prior to ovulation, as well as formation of corpora lutea after ovulation. At the anterior pituitary level, BMPs also contribute to the regulation of gonadotrophin production.

The role of tight junction proteins in ovarian follicular development and ovarian cancer

Tight junctions (TJ) are protein structures that control the transport of water, ions and macromolecules across cell layers. Functions of the transmembrane TJ protein, occluding (OCLN) and the cytoplasmic TJ proteins, tight junction protein 1 (TJP1; also known as zona occludens protein-1), cingulin (CGN) and claudins (CLDN) are reviewed, and current evidence of their role in the ovarian function is reviewed. Abundance of OCLN, CLDNs and TJP1 mRNA changed during follicular growth. In vitro treatment with various growth factors known to affect ovarian folliculogenesis indicated that CGN, OCLN and TJP1 are hormonally regulated. The summarized studies indicate that expression of TJ proteins (i.e., OCLN, CLDN, TJP1 and CGN) changes with follicle size in a variety of vertebrate species but whether these changes in TJ proteins are increased or decreased depends on species and cell type. Evidence indicates that autocrine, paracrine and endocrine regulators, such as fibroblast growth factor-9, epidermal growth factor, androgens, tumor necrosis factor-α and glucocorticoids may modulate these TJ proteins. Additional evidence presented indicates that TJ proteins may be involved in ovarian cancer development in addition to normal follicular and luteal development. A model is proposed suggesting that hormonal downregulation of TJ proteins during ovarian follicular development could reduce barrier function (i.e., selective permeability of molecules between theca and granulosa cells) and allow for an increase in the volume of follicular fluid as well as allow additional serum factors into the follicle that may directly impact granulosa cell functions.

Proteomic analysis of follicular fluid in carriers and non-carriers of the Trio allele for high ovulation rate in cattle

This study was conducted to characterise differences in follicular fluid proteins between carriers and non-carriers of a bovine allele for high ovulation rate. A total of four non-carrier and five carrier females were used in an initial study with four and six additional non-carriers and carriers respectively used in a validation study. Emergence of the follicular wave was synchronised and the ovaries containing the dominant follicle(s) were extracted by ovariectomy for follicular fluid collection. A hexapeptide ligand library was used to overcome the masking effect of high-abundance proteins and to increase detection of low-abundance proteins in tandem mass spectrometry. After correcting for multiple comparisons, only two proteins, glia-derived nexin precursor (SERPINE2) and inhibin β B chain precursor (INHBB), were significantly differentially expressed (false-discovery rate <0.05). In a replicate study of analogous design differential expression was confirmed (P < 0.05). Joint analysis of results from the two studies indicated that three additional proteins were consistently differentially expressed between genotypes. For three of these five, previous studies have indicated that expression is increased by transforming growth factor-β–bone morphogenetic protein signalling; their reduction in follicular fluid from carrier animals is consistent with the ~9-fold overexpression of SMAD family member 6 (SMAD6) in carriers that is inhibitory to this pathway.

Three-dimensional Reconstruction of the Vascular Architecture of the Passive CLARITY-cleared Mouse Ovary

The ovary is the main organ of the female reproductive system and is essential for the production of female gametes and for controlling the endocrine system, but the complex structural relationships and three-dimensional (3D) vasculature architectures of the ovary are not well described. In order to visualize the 3D connections and architecture of blood vessels in the intact ovary, the first important step is to make the ovary optically clear. In order to avoid tissue shrinkage, we used the hydrogel fixation-based passive CLARITY (Clear Lipid-exchanged Acrylamide-hybridized Rigid Imaging/ Immunostaining/In situ-hybridization-compatible Tissue Hydrogel) protocol method to clear an intact ovary. Immunostaining, advanced multiphoton confocal microscopy, and 3D image-reconstructions were then used for the visualization of ovarian vessels and follicular capillaries. Using this approach, we showed a significant positive correlation (P <0.01) between the length of the follicular capillaries and volume of the follicular wall.

Regulation of follicle growth through hormonal factors and mechanical cues mediated by Hippo signaling pathway

The ovary is an interesting organ that shows major structural changes within a short period of time during each reproductive cycle. Follicle development is controlled by local paracrine and systemic endocrine factors. Many hormonal and molecular analyses have been conducted to find the mechanisms underlying structural changes in ovaries, However, exact mechanisms still remain to be determined. Recent development of mechanobiology facilitates the understanding on the contribution of physical forces and changes in the mechanical properties of cells and tissues to physiology and pathophysiology. The Hippo signaling pathway is one of the key players in mechanotransduction, providing an understanding of the molecular mechanisms by which cells sense and respond to mechanical signals to regulate cell proliferation and apoptosis for maintaining optimal organ sizes. Our group recently demonstrated the involvement of the Hippo signaling pathway in the regulation of ovarian follicle development. Fragmentation of ovarian cortex into small cubes changed cytoskeletal actin dynamics and induced disruption of the Hippo signaling pathway, leading to the production of CCN growth factors and anti-apoptotic BIRC. These factors, in turn, stimulated secondary follicle growth in vitro and in vivo. In this review, we summarized hormonal regulation of follicular structural changes and further focused on the role of Hippo signaling in the regulation of follicle development. We also suggest a new strategy of infertility treatments in patients with polycystic ovary syndrome and primary ovarian insufficiency based on mechanobiology.

Expression of miR-15a, miR-145, and miR-182 in granulosa-lutein cells, follicular fluid, and serum of women with polycystic ovary syndrome (PCOS)

PURPOSE

Polycystic ovary syndrome (PCOS) is one of the most common endocrinopathies that affects women in reproductive age. MicroRNAs (miRNAs) play crucial roles in normal function of female reproductive system and folliculogenesis. Deregulated expression of miRNAs in PCOS condition may be significantly implicated in the pathogenesis of PCOS. We determined relative expression of miR-15a, miR-145, and miR-182 in granulosa-lutein cells (GLCs), follicular fluid (FF), and serum of PCOS patients.

METHODS

Human subjects were divided into PCOS (n = 20) and control (n = 21) groups. GLCs, FF, and serum were isolated and stored. RNA isolation was performed and cDNA was reversely transcribed using specific stem-loop RT primers. Relative expression of miRNAs was calculated after normalization against U6 expression. Correlation of miRNAs' expression level with basic clinical features and predictive value of miRNAs in FF and serum were appraised.

RESULTS

Relative expression of miR-145 and miR-182 in GLCs was significantly decreased in PCOS, but miR-182 in FF of PCOS patients revealed up-regulated levels. Significant correlations between level of miRNAs in FF and serum and hormonal profile of subjects were observed. MiR-182 in FF showed a significant predictive value with AUC of 0.73, 76.4% sensitivity, and 70.5% specificity which was improved after combination of miR-182 and miR-145.

CONCLUSIONS

A significant dysregulation of miR-145 and miR-182 in GLCs of PCOS may indicate their involvement in pathogenesis of PCOS. Differential up-regulation of miR-182 in FF of PCOS patients with its promising predictive values for discrimination of PCOS reinforced the importance of studying miRNAs' profile in FF.

Expression of markers for germ cells and oocytes in cow dermal fibroblast treated with 5-azacytidine and cultured in differentiation medium containing BMP2, BMP4 or follicular fluid

This study aims to investigate the effect 5-azacytidine (5-Aza) during induction of pluripotency in bovine fibroblasts and to evaluate the effects of BMP2, BMP4 or follicular fluid in the differentiation of reprogrammed fibroblasts in primordial germ cells and oocytes. It also analysis the mRNA levels for OCT4, NANOG, REX, SOX2, VASA, DAZL, cKIT, SCP3, ZPA and GDF9 after culturing 5-Aza treated fibroblasts in the different tested medium. Dermal fibroblasts were cultured and exposed to 0.5, 1.0 or 2.0 μM of 5-Aza for 18 h, 36 h or 72 h. Then, the cells were cultured in DMEM/F12 supplemented with 10 ng/ml BMP2, 10 ng/ml BMP4 or 5% follicular fluid. After culture, morphological characteristics, viability and gene expression were evaluated by qPCR. Treatment of skin fibroblasts with 2.0 μM 5-Aza for 72 h significantly increased expression of mRNAs for SOX2, OCT4, NANOG and REX. The culture in medium supplemented with BMP2, BMP4 or follicular fluid for 7 or 14 days induced formation of oocyte-like cells, as well as the expression of markers for germ cells and oocyte. In conclusion, treatment of bovine skin-derived fibroblasts with 2.0 μM 5-Aza for 72 h induces the expression of pluripotency factors. Culturing these cells in differentiation medium supplemented with BMP2, BMP4 or follicular fluid induces morphological changes and promotes expression of markers for germ cells, meiosis and oocyte.

Glycosidases in porcine follicular fluid and their effect on zona pellucida-AWN 1 spermadhesin interaction

Oligosaccharide moieties on the surface of the oocyte belong to the key molecules that direct the course of fertilization and are subjected to changes during oocyte maturation in the follicle. In our study, we focused on the activities of five glycosidases in the fluids from porcine secondary and preovulatory follicles (α-l-fucosidase, α-d-galactosidase, β-d-galactosidase, β-D-N-acetylhexosaminidase, and α-d-mannosidase). All of them were detected active at neutral and acidic pH. However, changes in their activities associated with follicle development were observed only in the case of α-d-mannosidase, which was increased (P < 0.001), and β-d-galactosidase, which was decreased (P < 0.001) at neutral pH, and of α-d-galactosidase and β-N-acetylhexosaminidase, which were decreased (P < 0.0001) at the acidic pH. The comparison of glycosidases from follicular fluid and from blood plasma using red native electrophoresis revealed that most of the glycosidases are present in more than one isoenzyme form; some of them were detected mainly in the follicular fluid. Finally, we tested the effect of glycosidases on the interaction between zona pellucida and AWN 1 spermadhesin (putative sperm receptor of zona pellucida) and demonstrated that the effect of both β-d-galactosidase and to a lesser degree α-d-mannosidase led to a decrease in this interaction. We can hypothesize that these two glycosidases modulate the amount of zona pellucida oligosaccharide moieties and/or their structures for an optimal sperm binding in pigs.

Tracing and Characterizing the Development of Transplanted Female Germline Stem Cells In Vivo

It has long been believed that most female mammalian species lose the ability to generate oocytes in postnatal ovaries. Recent evidence has demonstrated the isolation and culture of female germline stem cells (FGSCs) from adult mice and humans. However, the process and mechanisms of FGSC differentiation in vivo following transplantation have not yet been studied. Here, we isolated and characterized FGSCs from a single EGFP-transgenic mouse, and traced the development and behavior of transplanted FGSCs (F-TFs) in vivo. Comparisons of folliculogenesis between recipients with FGSC transplantation and wild-type (WT) mice were performed by single follicle RNA-sequencing (RNA-seq). Results showed that FGSCs exhibited a homing ability and began to differentiate into early-stage oocytes only when they reached the edge of the ovarian cortex. The F-TFs restored function of premature ovarian failure (gdf9iCre; Pten^loxP/loxP genotype) and generated offspring. Furthermore, results demonstrated that the developmental mechanisms of follicles derived from F-TFs were similar to that of WT follicles. Weighted gene co-expression network analysis identified two potential sub-networks and core genes that played a critical role in follicular development. These findings provide a theoretical basis and lay a technology platform for specific or personalized medical treatment of ovarian failure or other ovarian diseases.

Expression of aquaporin 4 in the chicken ovary in relation to follicle development

In the mammalian ovary, aquaporins (AQPs) are thought to be involved in the regulation of fluid transport within the follicular wall and antrum formation. Data concerning the AQPs in the avian ovary is very limited. Therefore, the present study was designed to examine whether the AQP4 is present in the chicken ovary, and if so, what is its distribution in the ovarian compartment of the laying hen. Localization of AQP4 in the ovarian follicles at different stage of development was also investigated. After decapitation of hens the stroma with primordial follicles and white (1-4 mm), yellowish (4-8 mm), small yellow and the three largest yellow pre-ovulatory follicles F3-F1 (F3 < F2 < F1; 20-36 mm) were isolated from the ovary. The granulosa and theca layers were separated from the pre-ovulatory follicles. The AQP4 mRNA and protein were detected in all examined ovarian compartments by the real-time PCR and Western blot analyses, respectively. The relative expression of AQP4 was depended on follicular size and the layer of follicular wall. It was the lowest in the granulosa layer of pre-ovulatory follicles and the highest in the ovarian stroma as well as white and yellowish follicles. Along with approaching of the largest follicle to ovulation the gradual decrease in AQP4 protein level in the granulosa layer was observed. Immunoreactivity for AQP4 was present in the granulosa and theca cells (theca interna ≥ theca externa > granulosa). The obtained results suggest that AQP4 may take part in the regulation of water transport required for follicle development in the chicken ovary.

Non-coding RNAs in the Ovarian Follicle

The mammalian ovarian follicle is the complex reproductive unit comprising germ cell, somatic cells (Cumulus and Granulosa cells), and follicular fluid (FF): paracrine communication among the different cell types through FF ensures the development of a mature oocyte ready for fertilization. This paper is focused on non-coding RNAs in ovarian follicles and their predicted role in the pathways involved in oocyte growth and maturation. We determined the expression profiles of microRNAs in human oocytes and FF by high-throughput analysis and identified 267 microRNAs in FF and 176 in oocytes. Most of these were FF microRNAs, while 9 were oocyte specific. By bioinformatic analysis, independently performed on FF and oocyte microRNAs, we identified the most significant Biological Processes and the pathways regulated by their validated targets. We found many pathways shared between the two compartments and some specific for oocyte microRNAs. Moreover, we found 41 long non-coding RNAs able to interact with oocyte microRNAs and potentially involved in the regulation of folliculogenesis. These data are important in basic reproductive research and could also be useful for clinical applications. In fact, the characterization of non-coding RNAs in ovarian follicles could improve reproductive disease diagnosis, provide biomarkers of oocyte quality in Assisted Reproductive Treatment, and allow the development of therapies for infertility disorders.

Molecular evidence that follicle development is accelerated in vitro compared to in vivo

In this study, we systematically compared the morphological, functional and molecular characteristics of granulosa cells and oocytes obtained by a three-dimensional in vitro model of ovine ovarian follicular growth with those of follicles recovered in vivo. Preantral follicles of 200 µm diameter were recovered and cultured up to 950 µm over a 20-day period. Compared with in vivo follicles, the in vitro culture conditions maintained follicle survival, with no difference in the rate of atresia. However, the in vitro conditions induced a slight decrease in oocyte growth rate, delayed antrum formation and increased granulosa cell proliferation rate, accompanied by an increase and decrease in CCND2 and CDKN1A mRNA expression respectively. These changes were associated with advanced granulosa cell differentiation in early antral follicles larger than 400 µm diameter, regardless of the presence or absence of FSH, as indicated by an increase in estradiol secretion, together with decreased AMH secretion and expression, as well as increased expression of GJA1, CYP19A1, ESR1, ESR2, FSHR, INHA, INHBA, INHBB and FST. There was a decrease in the expression of oocyte-specific molecular markers GJA4, KIT, ZP3, WEE2 and BMP15 in vitro compared to that in vivo. Moreover, a higher percentage of the oocytes recovered from cultured follicles 550 to 950 µm in diameter was able to reach the metaphase II meiosis stage. Overall, this in vitro model of ovarian follicle development is characterized by accelerated follicular maturation, associated with improved developmental competence of the oocyte, compared to follicles recovered in vivo.

miRNA-mRNA network involved in folliculogenesis interactome: systems biology approach

At later phases of folliculogenesis, the mammalian ovarian follicle contains layers of granulosa cells surrounding an antral cavity. To better understand the molecular basis of follicular growth and granulosa cell maturation, we study transcriptome profiling of granulosa cells from small (<5 mm) and large (>10 mm) bovine follicles using simultaneous method of Affymetrix microarrays (24,128 probe sets) and RNA-Seq data sets. This study proposes a computational method to discover the functional miRNA-mRNA regulatory modules, that is, groups of miRNAs and their target mRNAs that are believed to take part cooperatively in post-transcriptional gene regulation under specific conditions. The reconstructed network was named Integrated miRNA-mRNA Bipartite Network. 277 genes and 6 key modules were disclosed through clustering for mRNA master list. The 66 genes are among the genes that belong to at least two modules. All these genes, being involved in at least one of the phenomena, namely cell survival, proliferation, metastasis and apoptosis, have an overexpression pattern (P < 0.01). For miRNA master list, a total of 172 sequences were differentially expressed (P < 0.01) between dominant (large) and each of subordinate (small) follicles. Within the follicle, these miRNAs were predominantly expressed in mural granulosa cells. Finally, predicted and validated targets of these miRNAs enriched in dominant (large) follicles were identified, which are mapped to signaling pathways involved in follicular cell proliferation, steroidogenesis, PI3K/AKT/mTOR and Ras/Raf/MEK/ERK. The identification of miRNAs and their target mRNAs and the construction of their regulatory networks may give new insights into biological procedures.

Altered expression of cytokines IL-1α, IL-6, IL-8 and TNF-α in bovine follicular persistence

In dairy cattle, cystic ovarian disease (COD) is an important cause of subfertility, and two of the main signs are ovulation failure and follicular persistence. The aim of this study was to examine the expression of the cytokines IL-1α, IL-6, IL-8 and TNF-α in ovarian follicular structures at different times of persistence in a model of follicular persistence induced by prolonged treatment with progesterone in dairy cows. Protein expression of IL-1α, IL-6, IL-8 and TNF-α was evaluated by immunohistochemistry. Additionally, IL-6 concentration in follicular fluid and serum was determined by ELISA. IL-1α, IL-6, IL-8 and TNF-α expression was increased in follicles with different persistence times in relation to the control dominant follicles, in granulosa cells. For IL-6, IL-8 and TNF-α, this increase was detected early (P0: expected time of ovulation and/or P5: 5 days of follicular persistence). Additionally, theca cells showed an increase in IL-6 in antral (groups P10 and P15) and persistent follicles (group P10) related to dominant follicles from the control group (p < 0.05). Serum concentration of IL-6 was higher in groups P5, P10 and P15 than in control cows (p < 0.05). The results show evidence that early development of COD in cows is concurrent with altered expression of these cytokines in different ovarian follicular structures and may contribute to the follicular persistence and endocrine changes found in cattle with follicular cysts.

Sheep Isolated Secondary Follicles Are Able to Produce Metaphase II Oocytes After Vitrification and Long-Term In Vitro Growth

The vitrification of preantral follicles followed by in vitro growth (IVG) could be valuable to produce fertilizable oocytes. However, the meiotic resumption rates of oocytes cultured from vitrified secondary follicles (SF) have been reported as suboptimal. This study aimed to verify two base media (alpha modification of minimum essential medium, α-MEM, and tissue culture medium 199, TCM199) on vitrified SF regarding different requirements during IVG. Sheep ovarian fragments were divided in six groups: (1) Fresh groups (Control α-MEM and TCM199): SF without vitrification; (2) Follicle-Vitrified (Follicle-Vit α-MEM and TCM199): SF vitrified after isolation; and (3) Tissue-Vitrified (Tissue-Vit α-MEM and TCM199): SF vitrified enclosed in ovarian fragments and, subsequently, isolated. The isolated SF were submitted to IVG for 18 days. Thereafter, the recovered cumulus-oocyte complexes (COCs) underwent in vitro maturation (IVM) and evaluation of chromatin configuration. Follicular granulosa cells were analyzed for their gene expression of Bax, Bcl2, and Connexins (CX) 37 and 43. COCs from in vivo antral follicles were used as in vivo control. Data were analyzed by analysis of variance, Tukey, and chi-square tests. Differences were considered significant if p-value is <0.05. Follicle-Vit groups had higher (p < 0.05) percentage of antrum formation compared with Tissue-Vit groups. Vitrification did not affect (p > 0.05) oocyte diameter postmaturation. Oocytes from Follicle-Vit in α-MEM reached metaphase II stage after IVM. Gene expression for CX37, CX43, and Bax was lower in Tissue-Vit groups. For Bcl2, the gene expression was the opposite. In conclusion, during IVG for 18 days, maximal oocyte meiotic resumption was not negatively impacted by vitrification and was greatest for isolated SF using α-MEM as a medium.

Androgen Stimulates Growth of Mouse Preantral Follicles In Vitro: Interaction With Follicle-Stimulating Hormone and With Growth Factors of the TGFβ Superfamily

Androgens are essential for the normal function of mature antral follicles but also have a role in the early stages of follicle development. Polycystic ovary syndrome (PCOS), the most common cause of anovulatory infertility, is characterized by androgen excess and aberrant follicle development that includes accelerated early follicle growth. We have examined the effects of testosterone and dihydrotestosterone (DHT) on development of isolated mouse preantral follicles in culture with the specific aim of investigating interaction with follicle-stimulating hormone (FSH), the steroidogenic pathway, and growth factors of the TGFβ superfamily that are known to have a role in early follicle development. Both testosterone and DHT stimulated follicle growth and augmented FSH-induced growth and increased the incidence of antrum formation among the granulosa cell layers of these preantral follicles after 72 hours in culture. Effects of both androgens were reversed by the androgen receptor antagonist flutamide. FSH receptor expression was increased in response to both testosterone and DHT, as was that of Star, whereas Cyp11a1 was down-regulated. The key androgen-induced changes in the TGFβ signaling pathway were down-regulation of Amh, Bmp15, and their receptors. Inhibition of Alk6 (Bmpr1b), a putative partner for Amhr2 and Bmpr2, by dorsomorphin resulted in augmentation of androgen-stimulated growth and modification of androgen-induced gene expression. Our findings point to varied effects of androgen on preantral follicle growth and function, including interaction with FSH-activated growth and steroidogenesis, and, importantly, implicate the intrafollicular TGFβ system as a key mediator of androgen action. These findings provide insight into abnormal early follicle development in PCOS.

Unexpected effect of the vehicle (grain ethanol) of homeopathic FSH on the in vitro survival and development of isolated ovine preantral follicles

The aims of this study were to investigate the effects of medium replacement system (experiment I) and of FSH presentations (homeopathic - FSH 6cH and allopathic FSH - rFSH; experiment II) on the in vitro development, hormone production and gene expression of isolated ovine preantral follicles cultured for 6 days. In experiment I, secondary follicles were cultured in the α-MEM+ supplemented with FSH 6cH (0.05 fg/ml) or recombinant bovine FSH (100 ng/ml) without/with daily medium addition. The homeopathic FSH treatments with/without medium addition improved (p < .05) follicular development compared to rFSH100 treatment without addition. FSH 6cH with addition showed the highest (p < .05) estradiol production. To verify whether the effects of homeopathic FSH were not due to its vehicle, experiment II was performed. The α-MEM+ was supplemented or not with alcohol (0.2% grain ethanol, v/v), FSH 6cH or rFSH100 with daily medium addition. Surprisingly, we found that all treatments improved follicular development compared to the α-MEM+ (p < .05). Moreover, homeopathic FSH was similar to the other treatments including its vehicle. In conclusion, its vehicle (ethanol) causes the effect of homeopathic FSH on in vitro development of isolated ovine preantral follicles.

Effects of exosome-like vesicles on cumulus expansion in pigs in vitro

Cell-secreted vesicles, such as exosomes, have recently been recognized as mediators of cell communication. A recent study in cattle showed the involvement of exosome-like vesicles in the control of cumulus expansion, a prerequisite process for normal ovulation; however, whether this is the case in other mammalian species is not known. Therefore, this study aimed to examine the presence of exosome-like vesicles in ovarian follicles and their effects on cumulus expansion in vitro in pigs. The presence of exosome-like vesicles in porcine follicular fluid (pFF) was confirmed by transmission electron microscopic observation, the detection of marker proteins, and RNA profiles specific to exosomes. Fluorescently labeled exosome-like vesicles isolated from pFF were incorporated into both cumulus and mural granulosa cells in vitro. Exosome-like vesicles were not capable of inducing cumulus expansion to a degree comparable to that induced by follicle-stimulating hormone (FSH). Moreover, exosome-like vesicles had no significant effects on the expression levels of transcripts required for the normal expansion process (HAS2, TNFAIP6, and PTGS2). Interestingly, FSH-induced expression of HAS2 and TNFAIP6 mRNA, but not of PTGS2 mRNA, was significantly increased by the presence of exosome-like vesicles; however, the degree of FSH-induced expansion was not affected. In addition, porcine exosome-like vesicles had no significant effects on the expansion of mouse cumulus-oocyte complexes. Collectively, the present results suggest that exosome-like vesicles are present in pFF, but they are not efficient in inducing cumulus expansion in pigs.

Regulation and roles of the hyaluronan system in mammalian reproduction

Hyaluronan (HA) is a non-sulphated glycosaminoglycan polymer naturally occurring in many tissues and fluids of mammals, including the reproductive system. Its biosynthesis by HA synthase (HAS1-3) and catabolism by hyaluronidases (HYALs) are affected by ovarian steroid hormones. Depending upon its molecular size, HA functions both as a structural component of tissues in the form of high-molecular-weight HA or as a signalling molecule in the form of small HA molecules or HA fragments with effects mediated through interaction with its specific cell-membrane receptors. HA is produced by oocytes and embryos and in various segments of the reproductive system. This review provides information about the expression and function of members of the HA system, including HAS, HYALs and HA receptors. We examine their role in various processes from folliculogenesis through oocyte maturation, fertilisation and early embryo development, to pregnancy and cervical dilation, as well as its application in assisted reproduction technologies. Particular emphasis has been placed upon the role of the HA system in pre-implantation embryo development and embryo implantation, for which we propose a hypothetical sequential model.