Heparan sulfate proteoglycans regulate responses to oocyte paracrine signals in ovarian follicle morphogenesis

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

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

Transcriptomic profile of premature ovarian insufficiency with RNA-sequencing

Introduction

This study aimed to explore the transcriptomic profile of premature ovarian insufficiency (POI) by investigating alterations in gene expression.

Methods

A total of sixty-one women, comprising 31 individuals with POI in the POI group and 30 healthy women in the control group (HC group), aged between 24 and 40 years, were recruited for this study. The transcriptomic profiles of peripheral blood samples from all study subjects were analyzed using RNA-sequencing.

Results

The results revealed 39 differentially expressed genes in individuals with POI compared to healthy controls, with 10 upregulated and 29 downregulated genes. Correlation analysis highlighted the relationship between the expression of SLC25A39, CNIH3, and PDZK1IP1 and hormone levels. Additionally, an effective classification model was developed using SLC25A39, CNIH3, PDZK1IP1, SHISA4, and LOC389834. Functional enrichment analysis demonstrated the involvement of these differentially expressed genes in the "haptoglobin-hemoglobin complex," while KEGG pathway analysis indicated their participation in the "Proteoglycans in cancer" pathway.

Conclusion

The identified genes could play a crucial role in characterizing the genetic foundation of POI, potentially serving as valuable biomarkers for enhancing disease classification accuracy.

Application of specific ELISAs for BMP15 and GDF9 to cumulus cell extracts from infertile women

Bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) are oocyte-specific paracrine factors which regulate ovarian cumulus cell (CC) functions. This study aimed to investigate if BMP15 and GDF9 bound to CCs can be characterized, quantified, and show an association with IVF outcomes in infertile women. BMP15 and GDF9 ELISAs were validated and applied to discarded CC extracts. Pooled CCs from individual patients were collected from 120 (cohort 1; BMP15 only) and 81 infertility patients (cohort 2; BMP15 and GDF9) undergoing superovulation. BMP15 and GDF9 levels expressed per CC DNA were correlated with maternal age, clinical and embryology data. Total BMP15 and GDF9 were highly correlated with each other (r = 0.9, p < 0.001). The GDF9:BMP15 ratio was unrelated to oocyte number or age. BMP15/CC DNA and GDF9/CC DNA were unaffected by the type of superovulation and were not related to oocyte/embryo outcomes.

Current Trends on Bioengineering Approaches for Ovarian Microenvironment Reconstruction

Ovarian tissue has a unique microarchitecture and a complex cellular and molecular dynamics that are essential for follicular survival and development. Due to this great complexity, several factors may lead to ovarian insufficiency, and therefore to systemic metabolic disorders and female infertility. Techniques currently used in the reproductive clinic such as oocyte cryopreservation or even ovarian tissue transplant, although effective, have several limitations, which impair their wide application. In this scenario, mimetic ovarian tissue reconstruction comes as an innovative alternative to develop new methodologies for germ cells preservation and ovarian functions restoration. The ovarian extracellular matrix (ECM) is crucial for oocyte viability maintenance, once it acts actively in folliculogenesis. One of the key components of ovarian bioengineering is biomaterials application that mimics ECM and provides conditions for cell anchorage, proliferation, and differentiation. Therefore, this review aims at describing ovarian tissue engineering approaches and listing the main limitations of current methods for preservation and reestablishment of ovarian fertility. In addition, we describe the main elements that structure this study field, highlighting the main advances and the challenges to overcome to develop innovative methodologies to be applied in reproductive medicine. Impact Statement This review presents the main advances in the application of tissue bioengineering in the ovarian tissue reconstruction to develop innovative solutions for ovarian fertility reestablishment.

Evaluation of Intrafollicular Syndecan 1, Glypican 3, and Spermidine Levels in Women with Diminished Ovarian Reserve

We aimed to evaluate the levels of Spermidine, Syndecan 1, and Glypican 3 (GPC3) in the follicle fluid of women with diminished ovarian reserve (DOR) and to examine the relationship of these markers with the number of embryos and clinical pregnancy. A total of 27 women with DOR and 34 women with normal ovarian reserve who underwent in vitro fertilization procedure were included in this prospectively designed study. Spermidine, Syndecan 1, and GPC3 levels were studied in the follicle fluid samples taken from the women at the time of oocyte retrieval by ELISA method, and their relations with the cycle outcomes were examined. The mean age was found as 38.1 ± 7.4 years in the DOR group and 35.1 ± 5.2 years in the control group (p = 0.027). When adjusted for age and body mass index, while the median Spermidine level was significantly higher (p < 0.001), both Syndecan 1 (p < 0.001) and GPC3 (p = 0.006) were significantly lower in the DOR group compared with control group. The cut-off value of Spermidine for clinical pregnancy prediction was found as 74.08 ng/mL with 78.9% sensitivity and 57.1% specificity [OR: 5 (95% CI: 1.4-17.6); AUC: 0.621; p = 0.138], while it was 0.96 ng/mL with 84.2% sensitivity and 59.5% specificity [OR: 7.8 (95% CI: 2-31.1); AUC: 0.701; p = 0.004] for GP3 and 1.15 ng/mL with 78.9 sensitivity and 57.1% specificity [OR: 5 (95% CI: 1.4-17.6); AUC: 0.680; p = 0.009] for Syndecan 1. Intrafollicular spermidine, Syndecan 1, and GPC3 levels may have a role in ovarian aging. Further randomized controlled studies in a larger population are needed for the relationship of these markers with cycle and pregnancy outcomes.

Targeting of bone morphogenetic protein complexes to heparin/heparan sulfate glycosaminoglycans in bioactive conformation

Bone morphogenetic proteins (BMP) are powerful regulators of cellular processes such as proliferation, differentiation, and apoptosis. However, the specific molecular requirements controlling the bioavailability of BMPs in the extracellular matrix (ECM) are not yet fully understood. Our previous work showed that BMPs are targeted to the ECM as growth factor-prodomain (GF-PD) complexes (CPLXs) via specific interactions of their PDs. We showed that BMP-7 PD binding to the extracellular microfibril component fibrillin-1 renders the CPLXs from an open, bioactive V-shape into a closed, latent ring shape. Here, we show that specific PD interactions with heparin/heparan sulfate glycosaminoglycans (GAGs) allow to target and spatially concentrate BMP-7 and BMP-9 CPLXs in bioactive V-shape conformation. However, targeting to GAGs may be BMP specific, since BMP-10 GF and CPLX do not interact with heparin. Bioactivity assays on solid phase in combination with interaction studies showed that the BMP-7 PD protects the BMP-7 GF from inactivation by heparin. By using transmission electron microscopy, molecular docking, and site-directed mutagenesis, we determined the BMP-7 PD-binding site for heparin. Further, fine-mapping of the fibrillin-1-binding site within the BMP-7 PD and molecular modeling showed that both binding sites are mutually exclusive in the open V- versus closed ring-shape conformation. Together, our data suggest that targeting exquisite BMP PD-binding sites by extracellular protein and GAG scaffolds integrates BMP GF bioavailability in a contextual manner in development, postnatal life, and connective tissue disease.

Controlling BMP growth factor bioavailability: The extracellular matrix as multi skilled platform

Bone morphogenetic proteins (BMPs) belong to the TGF-β superfamily of signaling ligands which comprise a family of pluripotent cytokines regulating a multitude of cellular events. Although BMPs were originally discovered as potent factors extractable from bone matrix that are capable to induce ectopic bone formation in soft tissues, their mode of action has been mostly studied as soluble ligands in absence of the physiologically relevant cellular microenvironment. This micro milieu is defined by supramolecular networks of extracellular matrix (ECM) proteins that specifically target BMP ligands, present them to their cellular receptors, and allow their controlled release. Here we focus on functional interactions and mechanisms that were described to control BMP bioavailability in a spatio-temporal manner within the respective tissue context. Structural disturbance of the ECM architecture due to mutations in ECM proteins leads to dysregulated BMP signaling as underlying cause for connective tissue disease pathways. We will provide an overview about current mechanistic concepts of how aberrant BMP signaling drives connective tissue destruction in inherited and chronic diseases.

Extracellular vesicles and female reproduction

Extracellular vesicles (EVs) are nano-sized membrane bound complexes that have been identified as a mean for intercellular communication between cells and tissues both in physiological and pathological conditions. These vesicles contain numerous molecules involved in signal transduction including microRNAs, mRNAs, DNA, proteins, lipids, and cytokines and can affect the behavior of recipient cells. Female reproduction is dependent on extremely fine-tuned endocrine regulation, and EVs may represent an added layer that contributes to this regulation. This narrative review article provides an update on the research of the role of EVs in female reproduction including folliculogenesis, fertilization, embryo quality, and implantation. We also highlight potential pitfalls in typical EV studies and discuss gaps in the current literature.

Reporting on the Role of miRNAs and Affected Pathways on the Molecular Backbone of Ovarian Insufficiency: A Systematic Review and Critical Analysis Mapping of Future Research

Ovarian insufficiency is identified as a perplexing entity in the long list of pathologies impairing fertility dynamics. The three distinct classifications of ovarian insufficiency are poor ovarian response, premature ovarian insufficiency/failure, and advanced maternal age, sharing the common denominator of deteriorated ovarian reserve. Despite efforts to define clear lines among the three, the vast heterogeneity and overlap of clinical characteristics renders their diagnosis and management challenging. Lack of a consensus has prompted an empirically based management coupled by uncertainty from the clinicians' perspective. Profiling of patients in the era of precision medicine seems to be the way forward, while the necessity for a novel approach is underlined. Implicating miRNAs in the quest for patient profiling is promising in light of their fundamental role in cellular and gene expression regulation. To this end, the current study sets out to explore and compare the three pathophysiologies-from a molecular point of view-in order to enable profiling of patients in the context of in vitro fertilization treatment and enrich the data required to practice individualized medicine. Following a systematic investigation of literature, data referring to miRNAs were collected for each patient category based on five included studies. miRNA-target pairs were retrieved from the DIANA-TarBase repository and microT-CDS. Gene and miRNA annotations were derived from Ensembl and miRbase. A subsequent gene-set enrichment analysis of miRNA targets was performed for each category separately. A literature review on the most crucial of the detected pathways was performed to reveal their relevance to fertility deterioration. Results supported that all three pathophysiologies share a common ground regarding the affected pathways, naturally attributed to the common denominator of ovarian insufficiency. As evidenced, miRNAs could be employed to explore the fine lines and diverse nature of pathophysiology since they constitute invaluable biomarkers. Interestingly, it is the differentiation through miRNAs and not through the molecular affected pathways that corresponds to the three distinctive categories. Alarming discrepancies among publications were revealed, pertaining to employment of empirical and arbitrary criteria in categorizing the patients. Following bioinformatic analysis, the final step of the current study consisted of a critical analysis of the molecular data sourced, providing a clear and unique insight into the physiological mechanisms involved. It is our intention to contribute to mapping future research dedicated to ovarian insufficiency and to help researchers navigate the overwhelming information published in molecular studies.

Serum Concentrations of Oocyte-Secreted Factors BMP15 and GDF9 During IVF and in Women With Reproductive Pathologies

Oocyte-secreted factors bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) are critical for folliculogenesis and fertility. This study developed ELISAs for the measurement of BMP15 and GDF9 in serum and investigated their usefulness as biomarkers of female reproductive function. Serum samples were obtained from women undergoing infertility treatments (n = 154) and from perimenopausal and postmenopausal women (n = 28). Serum concentrations of BMP15 and GDF9 were analyzed in women relative to age, anti-Müllerian hormone, number of oocytes retrieved, and polycystic ovary syndrome (PCOS) after superovulation for in vitro fertilization. BMP15 and GDF9 immunoassays were validated for specificity, sensitivity (24 and 26 pg/mL, respectively), and reproducibility. BMP15 and GDF9 were detectable in 61% and 29% of women, respectively. BMP15 and GDF9 varied 64-fold and 15-fold, respectively, between women, but they did not change within subjects following ovarian stimulation with gonadotropins. Serum GDF9 concentration, but not BMP15 concentration, was associated with oocyte number retrieved in patients without PCOS (P = 0.018). GDF9 and BMP15 associations with oocyte number differed significantly (P < 0.05) with PCOS status. GDF9 concentrations were lower in poor responders (women with fewer than four oocytes retrieved or with cancelled cycles; P = 0.020). Serum BMP15, but not GDF9, was lower in women >55 years of age, compared with women of reproductive age (P < 0.01). This study develops and validates immunoassays to quantitate BMP15 and GDF9 in human serum and to correlate concentrations with female reproductive potential. Although assay sensitivities require improvement, this study demonstrates the diagnostic potential of oocyte-secreted BMP15 and GDF9 as serum biomarkers in reproductive medicine.

Mouse oocytes connect with granulosa cells by fusing with cell membranes and form a large complex during follicle development

Proper development and maturation of oocytes requires interaction with granulosa cells. Previous reports have indicated that mammalian oocytes connect with cumulus cells through gap junctions at the tip of transzonal projections that extend from the cells. Although the gap junctions between oocytes and transzonal projections provide a pathway through which small molecules (<1 kDa) can travel, it is unclear how molecules >1 kDa are transported between the oocytes and cumulus cells. In this study, we presented new connections between oocytes and granulosa cells. The green fluorescein protein Aequorea coerulescens green fluorescein protein (AcGFP1) localizing in oocyte cell membrane, 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate and dextran conjugates (10,000 MW) injected into the oocytes, which were unable to pass through gap junctions, were diffused from the oocytes into the surrounding granulosa cells through these connections. These connect an oocyte to the surrounding cumulus and granulosa cells by fusing with the cell membranes and forming a large complex during follicle development. Furthermore, we show two characteristics of these connections during follicle development—the localization of growth and differentiation factor-9 within the connections and the dynamics of the connections at ovulation. This article presents for the first time that mammalian oocytes directly connect to granulosa cells by fusing with the cell membrane, similar to that in Drosophila.

Identification of differential abundances of mRNA transcript in cumulus cells and CCND1 associated with yak oocyte developmental competence

The development of an accurate and noninvasive preselection process for competent oocytes is essential to achieve a highly efficient in vitro production (IVP) of embryos. Cumulus cells (CCs) have important functions in oocyte growth, development, maturation, and fertilization. It, therefore, is important to know if the quality of oocytes can be ascertained by assessment of gene expression of the surrounding CCs or not. The aim of this study was to identify differentially expressed genes in yak CCs from oocytes with varying developmental competences as possible biomarkers for distinguishing oocyte competence. The isolated CCs were pooled into immature and mature groups in accordance with the maturation outcome of oocytes. A total of 9516 genes were differentially expressed in the two CC categories (P <  0.05). With a minimum change of 2.5-fold, 45 up-regulated and 79 down-regulated genes were observed in CCs belonging to the mature group compared with those in the immature group (P <  0.01). These genes were primarily enriched for the cell cycle, meiosis, cell signaling, metabolism, and apoptosis. The selected candidate genes (CCND1, BMP15, GDF9, H19, KLF4, GPC1, SYCP3, and CTSB) were validated using quantitative real-time polymerase chain reaction (RT-qPCR) and there were expression patterns similar to those detected with transcriptome analysis. The CCs from fertilized oocytes arrested at the 2-cell (2-cell group), or 8-cell (8-cell group) stages or that developed into blastocysts (the blastocyst group) had a 1.5-, 1.8-, and 2.3-fold increase, respectively, in mRNA relative abundance of CCND1 compared with CCs from unfertilized oocytes (P <  0.05). The results with the RT-qPCR analysis confirmed that the relative abundance of CCND1 mRNA in CCs was associated with oocyte developmental competence. In conclusion, RNA-Seq is useful in extracting transcriptomes and selecting markers associated with oocyte developmental competence. Furthermore, the expression of the CCND1 gene in yak CCs can be used to preselect oocytes for IVP efficiency.

Cumulin and FSH Cooperate to Regulate Inhibin B and Activin B Production by Human Granulosa-Lutein Cells In Vitro

The oocyte-secreted factors bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) interact functionally, and it is hypothesized that this interaction may be mediated by formation of a GDF9:BMP15 heterodimer termed cumulin. GDF9 and BMP15 regulate folliculogenesis and ovulation rate and have been shown to regulate inhibin and activin, local regulators of folliculogenesis. The objective of this study was to determine whether cumulin regulates granulosa cell inhibin and activin production and whether this requires cooperation with FSH. Human granulosa-lutein (hGL) cells collected from patients undergoing in vitro fertilization were cultured with or without FSH with various forms of recombinant cumulin (native and cysteine mutants, with or without the prodomains), and cysteine mutant GDF9 or BMP15. Messenger RNA expression of the subunits of inhibins/activins (INHA, INHBA, INHBB) and secretion of inhibin A, inhibin B, and activin B were measured. Mature forms and proforms of cumulin stimulated comparable INHBB mRNA expression and secretion of inhibin B and activin B, whereas GDF9 or BMP15 exhibited no effect. Cumulin, but not GDF9 or BMP15, interacted synergistically with FSH to increase INHBB mRNA and inhibin B expression. FSH markedly stimulated INHA, which encodes the α subunit of inhibin A/B, and suppressed activin B. Cumulin with or without FSH did not significantly alter inhibin A. Together these data demonstrate that cumulin, but not GDF9 or BMP15, exerts paracrine control of FSH-induced regulation of inhibin B and activin B. The prodomains of cumulin may have a minimal role in its actions on granulosa cells.

Oocyte Aging: The Role of Cellular and Environmental Factors and Impact on Female Fertility

Female aging is one of the most important factors that impacts human reproduction. With aging, there is a natural decline in female fertility. The decrease in fertility is slow and steady in women aged 30-35 years; however, this decline is accelerated after the age of 35 due to decreases in the ovarian reserve and oocyte quality. Human oocyte aging is affected by different environmental factors, such as dietary habits and lifestyle. The ovarian microenvironment contributes to oocyte aging and longevity. The immediate oocyte microenvironment consists of the surrounding cells. Crosstalk between the oocyte and microenvironment is mediated by direct contact with surrounding cells, the extracellular matrix, and signalling molecules, including hormones, growth factors, and metabolic products. In this review, we highlight the different microenvironmental factors that accelerate human oocyte aging and decrease oocyte function. The ovarian microenvironment and the stress that is induced by environmental pollutants and a poor diet, along with other factors, impact oocyte quality and function and contribute to accelerated oocyte aging and diseases of infertility.

Decellularized human ovarian scaffold based on a sodium lauryl ester sulfate (SLES)-treated protocol, as a natural three-dimensional scaffold for construction of bioengineered ovaries

BACKGROUND

The increasing number of patients with ovarian insufficiency due to autoimmune disorders, genetic predisposition, or iatrogenic effects of treatment such as cancer therapies necessitates an urgent measure to find a safe and transplantable alternative ovary. A bioengineered ovary is one of the strategies on which the researchers have recently been working. An engineered ovary should be able to mimic the natural ovary aspects. Recent studies suggest that the decellularized organ-specific extracellular matrix-based scaffolds can serve as a native niche to bioengineering artificial organs. Therefore, we established a human decellularized ovarian scaffold based on a sodium lauryl ester sulfate (SLES)-treated process, as an optimized protocol.

METHODS

The human ovary samples were decellularized with 1% SLES for 48 h followed by DNase I in PBS for 24 h, and then thoroughly rinsed in PBS to remove the cell remnants and chemical reagents. Efficient cell removal was confirmed by DNA content analysis, hematoxylin and eosin, and Hoechst staining. Preservation assessment of the extracellular matrix structures was performed by immunohistochemistry, histological staining, and scanning electron microscopy. An MTT test was done to assess the in vitro scaffold's cytocompatibility, and finally in vivo studies were performed to evaluate the biocompatibility, bioactivity, and secretion functions of the ovarian grafts made of primary ovarian cells (POCs) on the decellularized scaffolds.

RESULTS

Evidence provided by SEM, histochemical, and immunohistochemical analyses showed that the ovarian extracellular matrix was preserved after decellularization. Moreover, MTT test indicated the suitable cytocompatibility of the scaffolds. The in vivo assessment showed that the POCs kept their viability and bioactivity, and reconstructed the primordial or primary follicle-like structures within the scaffolds after transplantation. Immunostaining characterized somatic cells that were capable of expressing steroid hormone receptors; also, as a marker of granulosa cell, inhibin-α immunostaining demonstrated these cells within the grafts. Additionally, hormone assessment showed that serum estradiol and progesterone levels were significantly higher in ovariectomized rats with ovarian cells-seeded grafts than those with or without decellularized scaffold grafts.

CONCLUSIONS

A human ovary-specific scaffold based on a SLES-decellularized protocol as a biomimicry of the natural ovarian niche can be an ideal scaffold used to reconstruct the ovary.

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

Ovulation is the appropriately timed release of a mature, developmentally competent oocyte from the ovary into the oviduct, where fertilization occurs. Importantly, ovulation is tightly linked with oocyte maturation, demonstrating the interdependency of these two parallel processes, both essential for female fertility. Initiated by pituitary gonadotropins, the ovulatory process is mediated by intrafollicular paracrine factors from the theca, mural, and cumulus granulosa cells, as well as the oocyte itself. The result is the induction of cumulus expansion, proteolysis, angiogenesis, inflammation, and smooth muscle contraction, which are each required for follicular rupture. These complex intercellular communication networks and the essential ovulatory genes have been well defined in mouse models and are highly conserved in primates, including humans. Importantly, recent discoveries in regulation of ovulation highlight new areas of investigation.

Molecular organization and mechanical properties of the hyaluronan matrix surrounding the mammalian oocyte

Successful ovulation and oocyte fertilization are essential prerequisites for the beginning of life in sexually reproducing animals. In mammalian fertilization, the relevance of the protein coat surrounding the oocyte plasma membrane, known as zona pellucida, has been widely recognized, while, until not too long ago, the general belief was that the cumulus oophorus, consisting of follicle cells embedded in a hyaluronan rich extracellular matrix, was not essential. This opinion was based on in vitro fertilization procedures, in which a large number of sperms are normally utilized and the oocyte can be fertilized even if depleted of cumulus cells. Conversely, in vivo, only very few sperm cells reach the fertilization site, arguing against the possibility of a coincidental encounter with the oocyte. In the last two decades, proteins required for HA organization in the cumulus extracellular matrix have been identified and the study of fertility in mice deprived of the corresponding genes have provided compelling evidence that this jelly-like coat is critical for fertilization. This review focuses on the advances in understanding the molecular interactions making the cumulus environment suitable for oocyte and sperm encounter. Most of the studies on the molecular characterization of the cumulus extracellular matrix have been performed in the mouse and we will refer essentially to findings obtained in this animal model.

Syndecan 1 represses cell growth and FSH responsiveness in human granulosa cells

Albeit devoid of intrinsic catalytic activity, the transmembrane heparan sulphate proteoglycan syndecan 1 plays critical roles in cellular processes such as extracellular matrix crosstalk, cytoskeletal organization, cell spreading, proliferation and differentiation. During the ovarian cycle, the expression of syndecan 1 in granulosa cells shows cyclic variation suggesting that it might fulfil specific roles in follicle development. To investigate its physiological roles on granulosa cells, syndecan 1 was overexpressed in human granulosa cell line KGN which retains features of granulosa cells from small antral follicle such as estradiol (E2) synthesis and low expression of functional FSH receptor (FSHR). We demonstrated that overexpression of syndecan 1 in immature granulosa cells (KGN-SDC1) induces a profound alteration in their intrinsic characteristics including enhanced spreading and attachment, both associated with a reduced growth rate. Flow cytometry analysis revealed that syndecan 1 overexpression increases the percentage of KGN cells in quiescent phase. This partial cell cycle exit is concordant with downregulated levels of CCND1 and CDK4 and upregulated expression of CDK inhibitor CDKN1A. In parallel both unstimulated and FSH-induced E2 synthesis are reduced in KGN-SDC1 through both repression of CYP19A1 and FSHR mRNA associated with decreased levels of potential regulators NR5A1 and ESR2. Additionally, we provide evidence that transient cAMP accumulation reduction in cells overexpressing syndecan 1 is accompanied by an increase in cAMP-hydrolysing PDE activity. Our results demonstrated that syndecan 1 might regulate differentiation of granulosa cells and follicular development by means of various mechanisms involving morphological changes, control of signalling pathways and alterations in gene expressions.

Free French abstract: A French translation of this abstract is freely available at http://www.reproduction-online.org/content/153/6/797/suppl/DC2

Heparin, Heparan Sulphate and the TGF-β Cytokine Superfamily

Of the circa 40 cytokines of the TGF-β superfamily, around a third are currently known to bind to heparin and heparan sulphate. This includes TGF-β1, TGF-β2, certain bone morphogenetic proteins (BMPs) and growth and differentiation factors (GDFs), as well as GDNF and two of its close homologues. Experimental studies of their heparin/HS binding sites reveal a diversity of locations around the shared cystine-knot protein fold. The activities of the TGF-β cytokines in controlling proliferation, differentiation and survival in a range of cell types are in part regulated by a number of specific, secreted BMP antagonist proteins. These vary in structure but seven belong to the CAN or DAN family, which shares the TGF-β type cystine-knot domain. Other antagonists are more distant members of the TGF-β superfamily. It is emerging that the majority, but not all, of the antagonists are also heparin binding proteins. Any future exploitation of the TGF-β cytokines in the therapy of chronic diseases will need to fully consider their interactions with glycosaminoglycans and the implications of this in terms of their bioavailability and biological activity.

Failure to launch: aberrant cumulus gene expression during oocyte in vitro maturation

In vitro maturation (IVM) offers significant benefits for human infertility treatment and animal breeding, but this potential is yet to be fully realised due to reduced oocyte developmental competence in comparison with in vivo matured oocytes. Cumulus cells occupy an essential position in determining oocyte developmental competence. Here we have examined the areas of deficient gene expression, as determined within microarrays primarily from cumulus cells of mouse COCs, but also other species, between in vivo matured and in vitro matured oocytes. By retrospectively analysing the literature, directed by focussing on downregulated genes, we provide an insight as to why the in vitro cumulus cells fail to support full oocyte potential and dissect molecular pathways that have important roles in oocyte competence. We conclude that the roles of epidermal growth factor signalling, the expanded extracellular matrix, cumulus cell metabolism and the immune system are critical deficiencies in cumulus cells of IVM COCs.

Growth Differentiation Factor 5-Mediated Enhancement of Chondrocyte Phenotype Is Inhibited by Heparin: Implications for the Use of Heparin in the Clinic and in Tissue Engineering Applications

The highly sulfated glycosaminoglycan (GAG) heparin is widely used in the clinic as an anticoagulant, and researchers are now using it to enhance stem cell expansion/differentiation protocols, as well as to improve the delivery of growth factors for tissue engineering (TE) strategies. Growth differentiation factor 5 (GDF5) belongs to the bone morphogenetic protein family of proteins and is vital for skeletal formation; however, its interaction with heparin and heparan sulfate (HS) has not been studied. We identify GDF5 as a novel heparin/HS binding protein and show that HS proteoglycans are vital in localizing GDF5 to the cell surface. Clinically relevant doses of heparin (≥10 nM), but not equivalent concentrations of HS, were found to inhibit GDF5's biological activity in both human mesenchymal stem/stromal cell-derived chondrocyte pellet cultures and the skeletal cell line ATDC5. We also found that heparin inhibited both GDF5 binding to cell surface HS and GDF5-induced induction of Smad 1/5/8 signaling. Furthermore, GDF5 significantly increased aggrecan gene expression in chondrocyte pellet cultures, without affecting collagen type X expression, making it a promising target for the TE of articular cartilage. Importantly, this study may explain the variable (and disappointing) results seen with heparin-loaded biomaterials for skeletal TE and the adverse skeletal effects reported in the clinic following long-term heparin treatment. Our results caution the use of heparin in the clinic and in TE applications, and prompt the transition to using more specific GAGs (e.g., HS derivatives), with better-defined structures and fewer off-target effects.

Identification of molecular markers for oocyte competence in bovine cumulus cells

Cumulus cells (CCs) have an important role during oocyte growth, competence acquisition, maturation, ovulation and fertilization. In an attempt to isolate potential biomarkers for bovine in vitro fertilization, we identified genes differentially expressed in bovine CCs from oocytes with different competence statuses, through microarray analysis. The model of follicle size, in which competent cumulus-oocyte complexes (COCs) were recovered from bigger follicles (≥8.0 mm in diameter) and less competent ones from smaller follicles (1-3 mm), was used. We identified 4178 genes that were differentially expressed (P < 0.05) in the two categories of CCs. The list was further enriched, through the use of a 2.5-fold change in gene expression as a cutoff value, to include 143 up-regulated and 80 down-regulated genes in CCs of competent COCs compared to incompetent COCs. These genes were screened according to their cellular roles, most of which were related to cell cycle, DNA repair, energy metabolism, metabolism of amino acids, cell signaling, meiosis, ovulation and inflammation. Three candidate genes up-regulated (FGF11, IGFBP4, SPRY1) and three down-regulated (ARHGAP22, COL18A1 and GPC4) in CCs from COCs of big follicles (≥8.1 mm) were selected for qPCR analysis. The selected genes showed the same expression patterns by qPCR and microarray analysis. These genes may be potential genetic markers that predict oocyte competence in in vitro fertilization routines.

Oocyte-dependent activation of MTOR in cumulus cells controls the development and survival of cumulus-oocyte complexes

Communication between oocytes and their companion somatic cells promotes the healthy development of ovarian follicles, which is crucial for producing oocytes that can be fertilized and are competent to support embryogenesis. However, how oocyte-derived signaling regulates these essential processes remains largely undefined. Here, we demonstrate that oocyte-derived paracrine factors, particularly GDF9 and GDF9-BMP15 heterodimer, promote the development and survival of cumulus-cell-oocyte complexes (COCs), partly by suppressing the expression of Ddit4l, a negative regulator of MTOR, and enabling the activation of MTOR signaling in cumulus cells. Cumulus cells expressed less Ddit4l mRNA and protein than mural granulosa cells, which is in striking contrast to the expression of phosphorylated RPS6 (a major downstream effector of MTOR). Knockdown of Ddit4l activated MTOR signaling in cumulus cells, whereas inhibition of MTOR in COCs compromised oocyte developmental competence and cumulus cell survival, with the latter likely to be attributable to specific changes in a subset of transcripts in the transcriptome of COCs. Therefore, oocyte suppression of Ddit4l expression allows for MTOR activation in cumulus cells, and this oocyte-dependent activation of MTOR signaling in cumulus cells controls the development and survival of COCs.

Growth and differentiation factor 9 promotes oocyte growth at the primary but not the early secondary stage in three-dimensional follicle culture

PURPOSE

Factors that differentially regulate oocyte and granulosa cell growth within the early preantral follicle and how these factors differ at each stage of follicle growth remain poorly understood. The aim of this study was to isolate and evaluate the effect of recombinant growth and differentiation factor 9 (GDF9) on oocyte and granulosa cell growth at the primary and early secondary stages of preantral follicle growth during in vitro culture.

METHODS

Primary stage follicles (diameters of 50-89 μm) and early secondary stage follicles (diameters of 90-120 μm) were isolated from immature mice, and individual, intact follicles were cultured in vitro in the presence and absence of recombinant GDF9. The effects of GDF9 on follicle growth were determined by the assessment of changes in the follicle volume during culture. The growth of the granulosa cell and oocyte compartments of the follicles was evaluated separately at each stage.

RESULTS

GDF9 significantly increased the growth of isolated follicles at both the primary and early secondary follicle stages. Independent evaluation of the granulosa cell and oocyte compartments revealed that, while GDF9 promoted granulosa cell growth at both stages of folliculogenesis, oocyte growth was stage specific. GDF9 promoted growth of the oocyte at the primary, but not the early secondary, follicle stage.

CONCLUSIONS

These findings demonstrate a stage-specific role for GDF9 in the regulation of oocyte and granulosa cell growth at the primary and early secondary stages of preantral follicle development.

Modifications of human growth differentiation factor 9 to improve the generation of embryos from low competence oocytes

Growth differentiation factor 9 (GDF9) is an oocyte-derived growth factor that plays a critical role in ovarian folliculogenesis and oocyte developmental competence and belongs to the TGF-β family of proteins. Recombinant human GDF9 (hGDF9) is secreted in a latent form, which in the case of the fully processed protein, has the proregion noncovalently associated with the mature region. In this study, we investigated a number of amino acid residues in the mature region of hGDF9 that are different from the corresponding residues in the mouse protein, which is not latent. We designed, expressed, and purified 4 forms of chimeric hGDF9 (M1-M4) that we found to be active in a granulosa cell bioassay. Using a porcine in vitro maturation model with inherent low developmental competence (yielding 10%-20% blastocysts), we tested the ability of the chimeric hGDF9 proteins to improve oocyte maturation and developmental competence. Interestingly, one of the chimeric proteins, M3, was able to significantly increase the level of embryo production using such low competence oocytes. Our molecular modeling studies suggest that in the case of hGDF9 the Gly(391)Arg mutation probably increases receptor binding affinity, thereby creating an active protein for granulosa cells in vitro. However, for an improvement in oocyte developmental competence, a second mutation (Ser(412)Pro), which potentially decreases the affinity of the mature region for the proregion, is also required.

Control of Oocyte Growth and Development by Intercellular Communication Within the Follicular Niche

In the mammalian ovary, each oocyte grows and develops within its own structural and developmental niche-the follicle. Together with the female germ cell in the follicle are somatic granulosa cells, specialized companion cells that surround the oocyte and provide support to it, and an outer layer of thecal cells that serve crucial roles including steroid synthesis. These follicular compartments function as a single physiological unit whose purpose is to produce a healthy egg, which upon ovulation can be fertilized and give rise to a healthy embryo, thus enabling the female germ cell to fulfill its reproductive potential. Beginning from the initial stage of follicle formation and until terminal differentiation at ovulation, oocyte and follicle growth depend absolutely on cooperation between the different cellular compartments. This cooperation synchronizes the initiation of oocyte growth with follicle activation. During growth, it enables metabolic support for the follicle-enclosed oocyte and allows the follicle to fulfill its steroidogenic potential. Near the end of the growth period, intra-follicular interactions prevent the precocious meiotic resumption of the oocyte and ensure its nuclear differentiation. Finally, cooperation enables the events of ovulation, including meiotic maturation of the oocyte and expansion of the cumulus granulosa cells. In this chapter, we discuss the cellular interactions that enable the growing follicle to produce a healthy oocyte, focusing on the communication between the germ cell and the surrounding granulosa cells.

Molecular markers for oocyte competence in bovine cumulus cells

This study aimed to quantify the expression of candidate genes in cumulus cells (CCs) from cumulus-oocyte complexes (COCs) with high and low potential for in vitro development up to the blastocyst stage. First, the effects of individual culture and biopsy on embryo development were evaluated. Individuals cultured using the well of the well system were compared with individuals cultured in 20 μL droplets (microdroplets) and those cultured in groups (control). Blastocyst rates were lower for the individual culture systems (P < 0.05; well of the well = 17.9%, n = 95; microdrop = 26.3%, n = 95) than for the control group (45.0%, n = 209). Second, the effects of biopsy on embryo production were compared between the control and microdroplet cultures, and no effects (P > 0.05) were observed for either group. Finally, the expression profiles of glypican 4 (GPC4), IGF4-binding protein, follicle-stimulating hormonereceptor, growth hormone receptor, epidermal growth factor receptor, fibroblast growth factor 11, solute carrier family 2 member 1, solute carrier family 2 member 3,sprouty homolog 1, versican, and keratin protein 8 in CCs obtained by biopsy were quantified by real-time polymerase chain reaction. Cumulus cells were categorized on the basis of the fates of the COCs: expanded blastocyst, cleaved and arrested, and uncleaved. The GPC4 gene was overexpressed (P = 0.007) in CCs from oocytes that formed embryos compared with those that produced cleaved and arrested embryos. We concluded that individual culture reduced blastocyst production; however, biopsy did not affect embryo development. The profile of GPC4 expression can be used as a marker to distinguish COCs with potential for embryo development from those with limited developmental potential.

Cumulin, an Oocyte-secreted Heterodimer of the Transforming Growth Factor-β Family, Is a Potent Activator of Granulosa Cells and Improves Oocyte Quality

Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are oocyte-specific growth factors with central roles in mammalian reproduction, regulating species-specific fecundity, ovarian follicular somatic cell differentiation, and oocyte quality. In the human, GDF9 is produced in a latent form, the mechanism of activation being an open question. Here, we produced a range of recombinant GDF9 and BMP15 variants, examined their in silico and physical interactions and their effects on ovarian granulosa cells (GC) and oocytes. We found that the potent synergistic actions of GDF9 and BMP15 on GC can be attributed to the formation of a heterodimer, which we have termed cumulin. Structural modeling of cumulin revealed a dimerization interface identical to homodimeric GDF9 and BMP15, indicating likely formation of a stable complex. This was confirmed by generation of recombinant heterodimeric complexes of pro/mature domains (pro-cumulin) and covalent mature domains (cumulin). Both pro-cumulin and cumulin exhibited highly potent bioactivity on GC, activating both SMAD2/3 and SMAD1/5/8 signaling pathways and promoting proliferation and expression of a set of genes associated with oocyte-regulated GC differentiation. Cumulin was more potent than pro-cumulin, pro-GDF9, pro-BMP15, or the two combined on GC. However, on cumulus-oocyte complexes, pro-cumulin was more effective than all other growth factors at notably improving oocyte quality as assessed by subsequent day 7 embryo development. Our results support a model of activation for human GDF9 dependent on cumulin formation through heterodimerization with BMP15. Oocyte-secreted cumulin is likely to be a central regulator of fertility in mono-ovular mammals.

Stem cells, progenitor cells, and lineage decisions in the ovary

Exploring stem cells in the mammalian ovary has unleashed a Pandora's box of new insights and questions. Recent evidence supports the existence of stem cells of a number of the different cell types within the ovary. The evidence for a stem cell model producing mural granulosa cells and cumulus cells is strong, despite a limited number of reports. The recent identification of a precursor granulosa cell, the gonadal ridge epithelial-like cell, is exciting and novel. The identification of female germline (oogonial) stem cells is still very new and is currently limited to just a few species. Their origins and physiological roles, if any, are unknown, and their potential to produce oocytes and contribute to follicle formation in vivo lacks robust evidence. The precursor of thecal cells remains elusive, and more compelling data are needed. Similarly, claims of very small embryonic-like cells are also preliminary. Surface epithelial cells originating from gonadal ridge epithelial-like cells and from the mesonephric epithelium at the hilum of the ovary have also been proposed. Another important issue is the role of the stroma in guiding the formation of the ovary, ovigerous cords, follicles, and surface epithelium. Immune cells may also play key roles in developmental patterning, given their critical roles in corpora lutea formation and regression. Thus, while the cellular biology of the ovary is extremely important for its major endocrine and fertility roles, there is much still to be discovered. This review draws together the current evidence and perspectives on this topic.

Oocyte expression, secretion and somatic cell interaction of mouse bone morphogenetic protein 15 during the peri-ovulatory period

Bone morphogenetic protein 15 (BMP15) is a key intraovarian growth factor regulating mammalian fertility, yet expression and localisation of different BMP15 protein forms within ovarian follicles around the time of the preovulatory LH surge remains unclear. Using immunoblotting and immunocytochemistry, the present study identified that post-translationally processed BMP15 proregion and mature proteins are increasingly expressed and localised with cumulus and granulosa cells from mice treated with pregnant mare’s serum gonadotropin (PMSG) + human chorionic gonadotrophin (hCG). However, this increased expression was absent in cumulus–oocyte complexes matured in vitro. Pull-down assays further revealed that the recombinant BMP15 proregion is capable of specific interaction with isolated granulosa cells. To verify an oocyte, and not somatic cell, origin of Bmp15 mRNA and coregulated growth differentiation factor 9 (Gdf9), in situ hybridisation and quantitative polymerase chain reaction results confirmed the exclusive oocyte localisation of Bmp15 and Gdf9, regardless of treatment or assay method. Relative oocyte expression levels of Bmp15 and Gdf9 decreased significantly after PMSG + hCG treatment; nevertheless, throughout all treatments, the Bmp15 : Gdf9 mRNA expression ratio remained unchanged. Together, these data provide evidence that the preovulatory LH surge leads to upregulation of several forms of BMP15 protein secreted by the oocyte for putative sequestration and/or interaction with ovarian follicular somatic cells.

Bone morphogenetic protein 15 in the pro-mature complex form enhances bovine oocyte developmental competence

Developmental competence of in vitro matured (IVM) oocytes needs to be improved and this can potentially be achieved by adding recombinant bone morphogenetic protein 15 (BMP15) or growth differentiation factor (GDF9) to IVM. The aim of this study was to determine the effect of a purified pro-mature complex form of recombinant human BMP15 versus the commercially available bioactive forms of BMP15 and GDF9 (both isolated mature regions) during IVM on bovine embryo development and metabolic activity. Bovine cumulus oocyte complexes (COCs) were matured in vitro in control medium or treated with 100 ng/ml pro-mature BMP15, mature BMP15 or mature GDF9 +/− FSH. Metabolic measures of glucose uptake and lactate production from COCs and autofluorescence of NAD(P)H, FAD and GSH were measured in oocytes after IVM. Following in vitro fertilisation and embryo culture, day 8 blastocysts were stained for cell numbers. COCs matured in medium +/− FSH containing pro-mature BMP15 displayed significantly improved blastocyst development (57.7±3.9%, 43.5±4.2%) compared to controls (43.3±2.4%, 28.9±3.7%) and to mature GDF9+FSH (36.1±3.0%). The mature form of BMP15 produced intermediate levels of blastocyst development; not significantly different to control or pro-mature BMP15 levels. Pro-mature BMP15 increased intra-oocyte NAD(P)H, and reduced glutathione (GSH) levels were increased by both forms of BMP15 in the absence of FSH. Exogenous BMP15 in its pro-mature form during IVM provides a functional source of oocyte-secreted factors to improve bovine blastocyst development. This form of BMP15 may prove useful for improving cattle and human artificial reproductive technologies.

Ovarian membrane-type matrix metalloproteinases: induction of MMP14 and MMP16 during the periovulatory period in the rat, macaque, and human

An intrafollicular increase in proteolytic activity drives ovulatory events. Surprisingly, the periovulatory expression profile of the membrane-type matrix metalloproteinases (MT-MMPs), unique proteases anchored to the cell surface, has not been extensively examined. Expression profiles of the MT-MMPs were investigated in ovarian tissue from well-characterized rat and macaque periovulatory models and naturally cycling women across the periovulatory period. Among the six known MT-MMPs, mRNA expression of Mmp14, Mmp16, and Mmp25 was increased after human chorionic gonadotropin (hCG) administration in rats. In human granulosa cells, mRNA expression of MMP14 and MMP16 increased following hCG treatment. In contrast, mRNA levels of MMP16 and MMP25 in human theca cells were unchanged before ovulation but declined by the postovulatory stage. In macaque granulosa cells, hCG increased mRNA for MMP16 but not MMP14. Immunoblotting showed that protein levels of MMP14 and MMP16 in rats increased, similar to their mRNA expression. In macaque granulosa cells, only the active form of the MMP14 protein increased after hCG, unlike its mRNA or the proprotein. By immunohistochemistry, both MMP14 and MMP16 localized to the different ovarian cell types in rats and humans. Treatment with hCG resulted in intense immunoreactivity of MMP14 and MMP16 proteins in the granulosa and theca cells. The present study shows that MMP14 and MMP16 are increased by hCG administration in the ovulating follicle, demonstrating that these MMPs are conserved among rats, macaques, and humans. These findings suggest that MT-MMPs could have an important role in promoting ovulation and remodeling of the ovulated follicle into the corpus luteum.

Characterization of the human cumulus cell transcriptome during final follicular maturation and ovulation

Cumulus expansion and oocyte maturation are central processes in ovulation. Knowledge gained from rodent and other mammalian models has revealed some of the molecular pathways associated with these processes. However, the equivalent pathways in humans have not been thoroughly studied and remain unidentified. Compact cumulus cells (CCs) from germinal vesicle cumulus oocyte complexes (COCs) were obtained from patients undergoing in vitro maturation (IVM) procedures. Expanded CCs from metaphase 2 COC were obtained from patients undergoing IVF/ICSI. Global transcriptome profiles of the samples were obtained using state-of-the-art RNA sequencing techniques. We identified 1746 differentially expressed (DE) genes between compact and expanded CCs. Most of these genes were involved in cellular growth and proliferation, cellular movement, cell cycle, cell-to-cell signaling and interaction, extracellular matrix and steroidogenesis. Out of the DE genes, we found 89 long noncoding RNAs, of which 12 are encoded within introns of genes known to be involved in granulosa cell processes. This suggests that unique noncoding RNA transcripts may contribute to the regulation of cumulus expansion and oocyte maturation. Using global transcriptome sequencing, we were able to generate a library of genes regulated during cumulus expansion and oocyte maturation processes. Analysis of these genes allowed us to identify important new genes and noncoding RNAs potentially involved in COC maturation and cumulus expansion. These results may increase our understanding of the process of oocyte maturation and could ultimately improve the efficacy of IVM treatment.

Age-associated differential microRNA levels in human follicular fluid reveal pathways potentially determining fertility and success of in vitro fertilization

Reproductive life span and fertility have been shown to depend on successful early folliculogenesis, which involves cell-to-cell communication and the concerted regulation of gene expression at both the oocyte and granulosa cell levels. Recently, micro RNAs (miRNAs) were identified as fine-tuners of gene expression. Here, we report that miRNAs can readily be detected within membrane-enclosed vesicles of human follicular fluid. MiRNA expression profiling of the follicular fluid of younger (<31 years) and older (>38 years) women revealed a set of four differentially expressed miRNAs. The predicted targets of these miRNAs are clearly enriched in genes involved in heparan-sulfate biosynthesis, extracellular matrix-receptor interaction, carbohydrate digestion and absorption, p53 signaling, and cytokine-cytokine-receptor interaction. Several of these pathways have been reported to be determinants of fertility, suggesting that this set of miRNAs and their respective targets should be evaluated in relation to reproductive aging and assisted reproduction.

Midkine and cytoplasmic maturation of mammalian oocytes in the context of ovarian follicle physiology

Midkine (MK) was originally characterized as a member of a distinct family of neurotrophic factors functioning in the CNS. However, it was later discovered that MK is abundantly expressed in ovarian follicles. Since then, the physiological roles of this molecule in the ovary have been steadily investigated. During the in vitro maturation (IVM) of oocytes MK was shown to promote the cytoplasmic maturation of oocytes, as indicated by post-fertilization development. This effect of MK could be mediated via its pro-survival (anti-apoptotic) effects on the cumulus-granulosa cells that surround oocytes. The oocyte competence-promoting effects of MK are discussed in the context of the recently discovered involvement of MK in the full maturation of ovarian follicles. MK was at the frontline of a new paradigm for neurotrophic factors as oocytetrophic factors. MK may promote the developmental competence of oocytes via common signalling molecules with the other neurotrophic factor(s). Alternatively or concomitantly, MK may also interact with various transmembrane molecules on cumulus-granulosa cells, which are important for ovarian follicle growth, dominance and differentiation, and act as a unique pro-survival factor in ovarian follicles, such that MK promotes oocyte competence. MK, along with other ovarian neurotrophic factors, may contribute to the optimization of the IVM system.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

Transcriptome profiling of granulosa cells of bovine ovarian follicles during growth from small to large antral sizes

Background

At later stages of folliculogenesis, the mammalian ovarian follicle contains layers of epithelial granulosa cells surrounding an antral cavity. During follicle development granulosa cells replicate, secrete hormones and support the growth of the oocyte. In cattle, the follicle needs to grow > 10 mm in diameter to allow an oocyte to ovulate, following which the granulosa cells cease dividing and differentiate into the specialised cells of the corpus luteum. To better understand the molecular basis of follicular growth and granulosa cell maturation, we undertook transcriptome profiling of granulosa cells from small (< 5 mm; n = 10) and large (> 10 mm, n = 4) healthy bovine follicles using Affymetrix microarrays (24,128 probe sets).

Results

Principal component analysis for the first two components and hierarchical clustering showed clustering into two groups, small and large, with the former being more heterogeneous. Size-frequency distributions of the coefficient of variation of the signal intensities of each probe set also revealed that small follicles were more heterogeneous than the large. IPA and GO enrichment analyses revealed that processes of axonal guidance, immune signalling and cell rearrangement were most affected in large follicles. The most important networks were associated with: (A) Notch, SLIT/ROBO and PI3K signalling, and (B) ITGB5 and extracellular matrix signalling through extracellular signal related kinases (ERKs). Upstream regulator genes which were predicted to be active in large follicles included STAT and XBP1. By comparison, developmental processes such as those stimulated by KIT, IHH and MEST were most active in small follicles. MGEA5 was identified as an upstream regulator in small follicles. It encodes an enzyme that modifies the activity of many target proteins, including those involved in energy sensing, by removal of N-acetylglucosamine from serine and threonine residues.

Conclusions

Our data suggest that as follicles enlarge more genes and/or pathways are activated than are inactivated, and gene expression becomes more uniform. These findings could be interpreted that either the cells in large follicles are more uniform in their gene expression, or that follicles are more uniform or a combination of both and that additional factors, such as LH, are additionally controlling the granulosa cells.

Regulation of acrosome reaction by Liprin α3, LAR and its ligands in mouse spermatozoa

Zona pellucida-based induction of acrosome reaction (AR) is a popular and well-accepted hypothesis. However, this hypothesis is being challenged in recent years and it has been proposed that the cumulus cells might be the site of AR. In our previous study, we reported the presence of a synaptic protein Liprin α3 on sperm acrosome, and proposed its role in AR. This study was designed to understand the role of Liprin α3 and its interacting proteins in regulation of AR. It is observed that the presence of anti-Liprin α3 antibody inhibits the process of AR. Colocalization experiments demonstrate the coexistence of leucocyte antigen related (LAR) protein, Rab-interacting molecule (RIM) and Liprin α3 on sperm acrosome thereby completing the identification of all the members of RIM/MUNC/Rab3A/liprinα complex required for membrane fusion. This study demonstrates the effect of LAR ligands such as Syndecans, Nidogens and LAR wedge domain peptide on AR. We could see an increase in AR in presence of these ligands. On the basis of these data, we speculate that in presence of ligands or wedge peptide, LAR undergoes dimerization leading to inhibition of phosphatase activity and increase in AR. The presence of one of the ligands Syndecan-1 on cumulus cells led us to hypothesize that it is Syndecan which induces AR in vivo and thus another site of AR could lie in cumulus.

A proteomic analysis of human follicular fluid: comparison between fertilized oocytes and non-fertilized oocytes in the same patient

PURPOSE

Human follicular fluid constitutes the microenvironment of follicles and includes various biological active proteins that can affect follicle growth and oocyte fertilization. Conducting proteomic evaluations of human follicular fluid may be helpful for identifying potential biomarkers possibly possessing a predictive value for oocyte quality and the success of in vitro fertilization.

METHOD

We performed proteomic profiling of human follicular fluids containing oocytes that were fertilized and resulted in pregnancy and follicular fluids containing oocytes that were not fertilized in the same patients undergoing intracytoplasmic sperm injection using the LTQ Orbitrap coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) analyses.

RESULTS

We identified a total of 503 proteins in human follicular fluids containing fertilized and non-fertilized oocytes obtained from 12 patients. We also found that 53 proteins exhibited significantly different spectral counts between the two groups, including heparan sulfate proteoglycan perlecan, which showed significant upregulation in the follicular fluids containing fertilized oocytes in comparison with that observed in the follicular fluids containing non-fertilized oocytes.

CONCLUSION

Our results suggest a possibility that proteins identified by LC/MS/MS in follicular fluid might not only be involved in folliculogenesis, but also function as biomarkers possessing predictive potential for oocyte maturation and the success of IVF when their expression levels are significantly different between fertilized and non-fertilized oocytes, although no distinctive biomarkers were identified in the current study.

Research resource: small RNA-seq of human granulosa cells reveals miRNAs in FSHR and aromatase genes

The granulosa cells in the mammalian ovarian follicle respond to gonadotropin signaling and are involved in the processes of folliculogenesis and oocyte maturation. Studies on gene expression and regulation in human granulosa cells are of interest due to their potential for estimating the oocyte viability and in vitro fertilization success. However, the posttranscriptional gene expression studies on micro-RNA (miRNA) level in the human ovary have been scarce. The current study determined the miRNA profile by deep sequencing of the 2 intrafollicular somatic cell types: mural and cumulus granulosa cells (MGCs and CGCs, respectively) isolated from women undergoing controlled ovarian stimulation and in vitro fertilization. Altogether, 936 annotated and 9 novel miRNAs were identified. Ninety of the annotated miRNAs were differentially expressed between MGCs and CGCs. Bioinformatic prediction revealed that TGFβ, ErbB signaling, and heparan sulfate biosynthesis were targeted by miRNAs in both granulosa cell populations, whereas extracellular matrix remodeling, Wnt, and neurotrophin signaling pathways were enriched among miRNA targets in MGCs. Two of the nine novel miRNAs found were of intronic origin: one from the aromatase and the other from the FSH receptor gene. The latter miRNA was predicted to target the activin signaling pathway. In addition to revealing the genome-wide miRNA signature in human granulosa cells, our results suggest that posttranscriptional regulation of gene expression by miRNAs could play an important role in the modification of gonadotropin signaling. miRNA expression studies could therefore lead to new prognostic markers in assisted reproductive technologies.

Rhesus monkey cumulus cells revert to a mural granulosa cell state after an ovulatory stimulus

Follicular somatic cells (mural granulosa cells and cumulus cells) and the oocyte communicate through paracrine interactions and through direct gap junctions between oocyte and cumulus cells. Considering that mural and cumulus cells arise through a common developmental pathway and that their differentiation is essential to reproductive success, understanding how these cells differ is a key aspect to understanding their critical functions. Changes in global gene expression before and after an ovulatory stimulus were compared between cumulus and mural granulosa cells to test the hypothesis that mural and cumulus cells are highly differentiated at the time of an ovulatory stimulus and further differentiate during the periovulatory interval. The transcriptomes of the two cell types were markedly different (>1500 genes) before an ovulatory hCG bolus but converged after ovulation to become completely overlapping. The predominant transition was for the cumulus cells to become more like mural cells after hCG. This indicates that the differentiated phenotype of the cumulus cell is not stable and irreversibly established but may rather be an ongoing physiological response to the oocyte.