Transcriptome based identification of mouse cumulus cell markers that predict the developmental competence of their enclosed antral oocytes

Role of FBXL5 in redox homeostasis and spindle assembly during oocyte maturation in mice

As an E3 ubiquitin ligase, F-box and leucine-rich repeat protein 5 (FBXL5) participates in diverse biologic processes. However, the role of Fbxl5 in mouse oocyte meiotic maturation has not yet been fully elucidated. The present study revealed that mouse oocytes depleted of Fbxl5 were unable to complete meiosis, as Fbxl5 silencing led to oocyte meiotic failure with reduced rates of GVBD and polar body extrusion. In addition, Fbxl5 depletion induced aberrant mitochondrial dynamics as we noted the overproduction of reactive oxygen species (ROS) and the accumulation of phosphorylated γH2AX with Fbxl5 knockdown. We also found that Fbxl5-KD led to the abnormal accumulation of CITED2 proteins in mouse oocytes. Our in vitro ubiquitination assay showed that FBXL5 interacted with CITED2 and that it mediated the degradation of CITED2 protein through the ubiquitination-proteasome pathway. Collectively, our data revealed critical functions of FBXL5 in redox hemostasis and spindle assembly during mouse oocyte maturation.

Obese outbred mice only partially benefit from diet normalization or calorie restriction as preconception care interventions to improve metabolic health and oocyte quality

STUDY QUESTION

Can diet normalization or a calorie-restricted diet for 2 or 4 weeks be used as a preconception care intervention (PCCI) in Western-type diet-induced obese Swiss mice to restore metabolic health and oocyte quality?

SUMMARY ANSWER

Metabolic health and oocyte developmental competence was already significantly improved in the calorie-restricted group after 2 weeks, while obese mice that underwent diet normalization showed improved metabolic health after 2 weeks and improved oocyte quality after 4 weeks.

WHAT IS KNOWN ALREADY

Maternal obesity is linked with reduced metabolic health and oocyte quality; therefore, infertile obese women are advised to lose weight before conception to increase pregnancy chances. However, as there are no univocal guidelines and the specific impact on oocyte quality is not known, strategically designed studies are needed to provide fundamental insights in the importance of the type and duration of the dietary weight loss strategy for preconception metabolic health and oocyte quality.

STUDY DESIGN, SIZE, DURATION

Outbred female Swiss mice were fed a control (CTRL) or high-fat/high-sugar (HF/HS) diet. After 7 weeks, some of the HF mice were put on two different PCCIs, resulting in four treatment groups: (i) only control diet for up to 11 weeks (CTRL_CTRL), (ii) only HF diet for up to 11 weeks (HF_HF), (iii) switch at 7 weeks from an HF to an ad libitum control diet (HF_CTRL) and (iv) switch at 7 weeks from an HF to a 30% calorie-restricted control diet (HF_CR) for 2 or 4 weeks. Metabolic health and oocyte quality were assessed at 2 and 4 weeks after the start of the intervention (n = 8 mice/treatment/time point).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Changes in body weight were recorded. To study the impact on metabolic health, serum insulin, glucose, triglycerides, total cholesterol and alanine aminotransferase concentrations were measured, and glucose tolerance and insulin sensitivity were analyzed at PCCI Weeks 2 and 4. The quality of in vivo matured oocytes was evaluated by assessing intracellular lipid droplet content, mitochondrial activity and localization of active mitochondria, mitochondrial ultrastructure, cumulus cell targeted gene expression and oocyte in vitro developmental competence.

MAIN RESULTS AND THE ROLE OF CHANCE

Significant negative effects of an HF/HS diet on metabolic health and oocyte quality were confirmed (P < 0.05). HF_CTRL mice already showed restored body weight, serum lipid profile and glucose tolerance, similar to the CTRL_CTRL group after only 2 weeks of PCCI (P < 0.05 compared with HF_HF) while insulin sensitivity was not improved. Oocyte lipid droplet volume was reduced at PCCI Week 2 (P < 0.05 compared with HF_HF), while mitochondrial localization and activity were still aberrant. At PCCI Week 4, oocytes from HF_CTRL mice displayed significantly fewer mitochondrial ultrastructural abnormalities and improved mitochondrial activity (P < 0.05), while lipid content was again elevated. The in vitro developmental capacity of the oocytes was improved but did not reach the levels of the CTRL_CTRL mice. HF_CR mice completely restored cholesterol concentrations and insulin sensitivity already after 2 weeks. Other metabolic health parameters were only restored after 4 weeks of intervention with clear signs of fasting hypoglycemia. Although all mitochondrial parameters in HF_CR oocytes stayed aberrant, oocyte developmental competence in vitro was completely restored already after 2 weeks of intervention.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

In this study, we applied a relevant HF/HS Western-type diet to induce obesity in an outbred mouse model. Nevertheless, physiological differences should be considered when translating these results to the human setting. However, the in-depth study and follow-up of the metabolic health changes together with the strategic implementation of specific PCCI intervals (2 and 4 weeks) related to the duration of the mouse folliculogenesis (3 weeks), should aid in the extrapolation of our findings to the human setting.

WIDER IMPLICATIONS OF THE FINDINGS

Our study results with a specific focus on oocyte quality provide important fundamental insights to be considered when developing preconception care guidelines for obese metabolically compromised women wishing to become pregnant.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Flemish Research Fund (FWO-SB grant 1S25020N and FWO project G038619N). The authors declare there are no conflicts of interest.

BPA disrupts meiosis I in oogonia by acting on pathways including cell cycle regulation, meiosis initiation and spindle assembly

The negative in utero effects of bisphenol A (BPA) on female reproduction are of concern since the ovarian reserve of primordial follicles is constituted during the fetal period. This time-window is difficult to access, particularly in humans. Animal models and explant culture systems are, therefore, vital tools for investigating EDC impacts on primordial germ cells (PGCs). Here, we investigated the effects of BPA on prophase I meiosis in the fetal sheep ovary. We established an in vitro model of early gametogenesis through retinoic acid (RA)-induced differentiation of sheep PGCs that progressed through meiosis. Using this system, we demonstrated that BPA (3×10^-7 M & 3×10^-5M) exposure for 20 days disrupted meiotic initiation and completion in sheep oogonia and induced transcriptomic modifications of exposed explants. After exposure to the lowest concentrations of BPA (3×10^-7M), only 2 probes were significantly up-regulated corresponding to NR2F1 and TMEM167A transcripts. In contrast, after exposure to 3×10^-5M BPA, 446 probes were deregulated, 225 were down- and 221 were up-regulated following microarray analysis. Gene Ontology (GO) annotations of differentially expressed genes revealed that pathways mainly affected were involved in cell-cycle phase transition, meiosis and spindle assembly. Differences in key gene expression within each pathway were validated by qRT-PCR. This study provides a novel model for direct examination of the molecular pathways of environmental toxicants on early female gametogenesis and novel insights into the mechanisms by which BPA affects meiosis I. BPA exposure could thereby disrupt ovarian reserve formation by inhibiting meiotic progression of oocytes I and consequently by increasing atresia of primordial follicles containing defective oocytes.

Transcriptome profile of goat folliculogenesis reveals the interaction of oocyte and granulosa cell in correlation with different fertility population

To understand the molecular and genetic mechanisms related to the litter size in one species of two different populations (high litter size and low litter size), we performed RNA-seq for the oocytes and granulosa cells (GCs) at different developmental stages of follicle, and identified the interaction of genes from both sides of follicle (oocyte and GCs) and the ligand-receptor pairs from these two sides. Our data were very comprehensive to uncover the difference between these two populations regarding the folliculogenesis. First, we identified a set of potential genes in oocyte and GCs as the marker genes which can be used to determine the goat fertility capability and ovarian reserve ability. The data showed that GRHPR, GPR84, CYB5A and ERAL1 were highly expressed in oocyte while JUNB, SCN2A, MEGE8, ZEB2, EGR1and PRRC2A were highly expressed in GCs. We found more functional genes were expressed in oocytes and GCs in high fertility group (HL) than that in low fertility group (LL). We uncovered that ligand-receptor pairs in Notch signaling pathway and transforming growth factor-β (TGF-β) superfamily pathways played important roles in goat folliculogenesis for the different fertility population. Moreover, we discovered that the correlations of the gene expression in oocytes and GCs at different stages in the two populations HL and LL were different, too. All the data reflected the gene expression landscape in oocytes and GCs which was correlated well with the fertility capability.

Chromosome Missegregation in Single Human Oocytes Is Related to the Age and Gene Expression Profile

The growing trend for women to postpone childbearing has resulted in a dramatic increase in the incidence of aneuploid pregnancies. Despite the importance to human reproductive health, the events precipitating female age-related meiotic errors are poorly understood. To gain new insight into the molecular basis of age-related chromosome missegregation in human oocytes, we combined the transcriptome profiles of twenty single oocytes (derived from females divided into two groups according to age <35 and ≥35 years) with their chromosome status obtained by array comparative genomic hybridization (aCGH). Furthermore, we compared the transcription profile of the single oocyte with the surrounding cumulus cells (CCs). RNA-seq data showed differences in gene expression between young and old oocytes. Dysregulated genes play a role in important biological processes such as gene transcription regulation, cytoskeleton organization, pathways related to RNA maturation and translation. The comparison of the transcription profile of the oocyte and the corresponding CCs highlighted the differential expression of genes belonging to the G protein-coupled receptor superfamily. Finally, we detected the loss of a X chromosome in two oocytes derived from women belonging to the ≥35 years age group. These aneuploidies may be caused by the detriment of REEP4, an endoplasmic reticulum protein, in women aged ≥35 years. Here we gained new insight into the complex regulatory circuit between the oocyte and the surrounding CCs and uncovered a new putative molecular basis of age-related chromosome missegregation in human oocytes.

Cumulus cell pappalysin-1, luteinizing hormone/choriogonadotropin receptor, amphiregulin and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1 mRNA levels associate with oocyte developmental competence and embryo outcomes

PURPOSE

To determine whether a selected set of mRNA biomarkers expressed in individual cumulus granulosa cell (CC) masses show association with oocyte developmental competence, embryo ploidy status, and embryo outcomes.

METHODS

This prospective observational cohort pilot study assessed levels of mRNA biomarkers in 163 individual CC samples from 15 women stimulated in antagonist cycles. Nineteen mRNA biomarker levels were measured by real-time PCR and related to the development of their corresponding individually cultured oocytes and subsequent embryos, embryo ploidy status, and live birth outcomes.

RESULTS

PAPPA mRNA levels were significantly higher in CC from oocytes that led to euploid embryos resulting in live births and aneuploid embryos compared to immature oocytes by ANOVA. LHCGR mRNA levels were significantly higher in CC of oocytes resulting in embryos associated with live birth compared to immature oocytes and oocytes resulting in arrested embryos by ANOVA. Using a general linearized mixed model to assess ploidy status, CC HSD3B mRNA levels in oocytes producing euploid embryos were significantly lower than other oocyte outcomes, collectively. When transferred euploid embryos outcomes were analyzed by ANOVA, AREG mRNA levels were significantly lower and PAPPA mRNA levels significantly higher in CC from oocytes that produced live births compared to transferred embryos that did not form a pregnancy.

CONCLUSIONS

Collectively, PAPPA, LHCGR, and AREG mRNA levels in CC may be able to identify oocytes with the best odds of resulting in a live birth, and HSD3B1 mRNA levels may be able to identify oocytes capable of producing euploid embryos.

Differential gene expression analysis of human cumulus cells

Objective

This study was performed to explore the possibility that each oocyte and its surrounding cumulus cells might have different genetic expression patterns that could affect human reproduction.

Methods

Differential gene expression analysis was performed for 10 clusters of cumulus cells obtained from 10 cumulus-oocyte complexes from 10 patients. Same procedures related to oocyte maturation, microinjection, and microarray analyses were performed for each group of cumulus cells. Two differential gene expression analyses were performed: one for the outcome of clinical pregnancy and one for the outcome of live birth.

Results

Significant genes resulting from these analyses were selected and the top 20 affected pathways in each group were analyzed. Circadian entrainment is determined to be the most affected pathway for clinical pregnancy, and proteoglycans in cancer pathway is the most affected pathway for live birth. Circadian entrainment is also amongst the 12 pathways that are found to be in top 20 affected pathways for both outcomes, and has both lowest p-value and highest number of times found count.

Conclusion

Although further confirmatory studies are necessary, findings of this study suggest that these pathways, especially circadian entrainment in cumulus cells, may be essential for embryo development and pregnancy.

Transcriptome analysis of porcine immature oocytes and surrounding cumulus cells after vitrification and in vitro maturation

Cryopreservation impairs oocyte quality, which may be associated with abnormal gene expression. Currently, alteration of mRNA levels in vitrified porcine oocytes has not been well characterized. The aim of this study was to analyze transcriptome profiles with RNA sequencing (RNA-seq) in porcine immature oocytes and their surrounding cumulus cells (CCs) after vitrification and in vitro maturation (IVM). There were 19 upregulated and 18 downregulated genes differentially expressed in vitrified oocytes, with no significant GO enrichment or KEGG pathway identified for these genes. In addition, CCs derived from vitrified oocytes had 40 significantly upregulated and 100 significantly downregulated genes. In total, 7 GO terms were significantly enriched in molecular function and biological process, and only MAPK signaling pathway reached significant enrichment based on KEGG analysis. Moreover, selected differentially expressed genes had similar expression patterns through comparison between results from qRT-PCR and RNA-Seq. In conclusion, our data provided detailed information on mRNA transcriptomes in porcine immature oocytes and CCs after vitrification and IVM, which offered now insights regarding reduced developmental potential of the vitrified oocytes.

IVM of mouse fully grown germinal vesicle oocytes upon a feeder layer of selected cumulus cells enhances their developmental competence

In the ovary, acquisition of oocyte developmental competence depends on a bidirectional exchange between the gamete and its companion cumulus cells (CCs). In this study we investigated the contribution of CCs surrounding oocytes of known developmental competence or incompetence to the acquisition of oocyte developmental competence. To this end, feeder layers of CCs (FL-CCs) were prepared using CCs isolated either from: (1) developmentally competent mouse oocytes whose nucleolus was surrounded by a chromatin ring (FL-SN-CCs); or (2) developmentally incompetent mouse oocytes whose nucleolus was not surrounded by a chromatin ring (FL-NSN-CCs). Denuded, fully grown oocytes (DOs) were matured to the MII stage on either FL-SN-CCs or FL-NSN-CCs, inseminated with spermatozoa and cultured throughout preimplantation development. FL-SN-CCs significantly improved the acquisition of oocyte developmental competence, with a blastocyst development rate equal to that for maturation of intact cumulus-oocyte-complexes. In contrast, DOs matured on FL-NSN-CCs or in the absence of CCs exhibited developmental failure, with embryos arresting at either the 4-cell or morula stage. These results set a culture platform to further improve the protocols for the maturation of DOs and to unravel the molecules involved in the cross-talk between the gamete and its companion CCs during the germinal vesicle to MII transition.

SIRT1 induces resistance to apoptosis in human granulosa cells by activating the ERK pathway and inhibiting NF-κB signaling with anti-inflammatory functions

SIRT1, a member of the sirtuin family, has recently emerged as a vital molecule in controlling ovarian function. The aims of the present study were to investigate SIRT1 expression and analyze SIRT1-mediated apoptosis in human granulosa cells (GCs). Human ovarian tissues were subjected to immunohistochemistry for localization of SIRT1 expression. SIRT1 knockdown in a human ovarian GC tumor line (COV434) was achieved by small interfering RNA, and the relationship between apoptosis and SIRT1 was assessed by quantitative reverse transcription polymerase chain reaction and western blotting. We further detected SIRT1 expression in human luteinized GCs. Associations among SIRT1 knockdown, SIRT1 stimulation (resveratrol) and expression of ERK1/2 and apoptotic regulatory proteins were analyzed in cell lines and luteinized GCs. Resveratrol downregulated the levels of nuclear factor (NF)-κB/p65, but this inhibitory effect was attenuated by suppressing SIRT1 activity. The NF-κB/p65 inhibitor pyrrolidine dithiocarbamate achieved similar anti-apoptosis effects. These results suggest that SIRT1 might play an anti-apoptotic role in apoptosis processes in GCs, possibly by sensing and regulating the ERK1/2 pathway, which has important clinical implications. Thus, our study provides a mechanistic link, whereby activation of SIRT1 function might help to sustain human reproduction by maintaining GCs as well as oocytes, offering a novel approach for developing a new class of therapeutic anti-inflammatory agents.

Functional signaling and gene regulatory networks between the oocyte and the surrounding cumulus cells

Background

The maturation and successful acquisition of developmental competence by an oocyte, the female gamete, during folliculogenesis is highly dependent on molecular interactions with somatic cells. Most of the cellular interactions identified, thus far, are modulated by growth factors, ions or metabolites. We hypothesized that this interaction is also modulated at the transcriptional level, which leads to the formation of gene regulatory networks between the oocyte and cumulus cells. We tested this hypothesis by analyzing transcriptome data from single oocytes and the surrounding cumulus cells collected from antral follicles employing an analytical framework to determine interdependencies at the transcript level.

Results

We overlapped our transcriptome data with putative protein-protein interactions and identified hundreds of ligand-receptor pairs that can transduce paracrine signaling between an oocyte and cumulus cells. We determined that 499 ligand-encoding genes expressed in oocytes and cumulus cells are functionally associated with transcription regulation (FDR < 0.05). Ligand-encoding genes with specific expression in oocytes or cumulus cells were enriched for biological functions that are likely associated with the coordinated formation of transzonal projections from cumulus cells that reach the oocyte’s membrane. Thousands of gene pairs exhibit significant linear co-expression (absolute correlation > 0.85, FDR < 1.8 × 10^− 5) patterns between oocytes and cumulus cells. Hundreds of co-expressing genes showed clustering patterns associated with biological functions (FDR < 0.5) necessary for a coordinated function between the oocyte and cumulus cells during folliculogenesis (i.e. regulation of transcription, translation, apoptosis, cell differentiation and transport).

Conclusion

Our analyses revealed a complex and functional gene regulatory circuit between the oocyte and surrounding cumulus cells. The regulatory profile of each cumulus-oocyte complex is likely associated with the oocytes’ developmental potential to derive an embryo.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4738-2) contains supplementary material, which is available to authorized users.

CUMULUS CELL GENES AS POTENTIAL BIOMARKERS OF OOCYTE AND EMBRYO DEVELOPMENTAL COMPETENCE

Bogomoletz Institute of Physiology NASU, Ukraine, Kiev. The selection of embryos with high implantation potential is the most important task in assisted reproductive technology. Today, this selection is based on subjective morphological criteria such as growth rate, early cleavage, the degree of fragmentation, blastocyst formation. However, the morphological assessment alone does not accurately predict oocyte/early stage embryo competence. Thus, the development of an objective, accurate, fast and affordable tests to determine oocyte quality and embryo viability could increase the chance of a successful pregnancy and reduce the number of embryos to transfer. The advent of new technologies, the so-called OMIKS, has allowed to identify novel biomarkers that can be used in cycle of in vitro fertilization (IVF) for oocyte and / or embryo selection. During folliculogenesis oocyte plays a dominant role in regulation of cumulus (CC) and granulosa cell (GC) functions, and it is consequently believed that functions of GC and CC indirectly reflect oocyte’s competence. Cell functions and active cell processes are regulated through gene expression therefore, gene expression analysis in GC and/or CC could provide a non-invasive method for identification of the most competent oocytes and embryos. In cumulus cells, genes have been identified that characterize the oocyte ability to undergo meiotic maturation, successful fertilization and early embryonic development. Among them cyclooxygenase 2, gremlin 1 and hyaluronan synthase-2, which play an important roles during oocyte development, ovulation and fertilization. This article reviews the recent data regarding these genes as potential biomarkers for selection of oocytes and embryos in the IVF program.

A Neural Network-Based Identification of Developmentally Competent or Incompetent Mouse Fully-Grown Oocytes

Infertility clinics would benefit from the ability to select developmentally competent vs. incompetent oocytes using non-invasive procedures, thus improving the overall pregnancy outcome. We recently developed a classification method based on microscopic live observations of mouse oocytes during their in vitro maturation from the germinal vesicle (GV) to the metaphase II stage, followed by the analysis of the cytoplasmic movements occurring during this time-lapse period. Here, we present detailed protocols of this procedure. Oocytes are isolated from fully-grown antral follicles and cultured for 15 h inside a microscope equipped for time-lapse analysis at 37 °C and 5% CO2. Pictures are taken at 8 min intervals. The images are analyzed using the Particle Image Velocimetry (PIV) method that calculates, for each oocyte, the profile of Cytoplasmic Movement Velocities (CMVs) occurring throughout the culture period. Finally, the CMVs of each single oocyte are fed through a mathematical classification tool (Feed-forward Artificial Neural Network, FANN), which predicts the probability of a gamete to be developmentally competent or incompetent with an accuracy of 91.03%. This protocol, set up for the mouse, could now be tested on oocytes of other species, including humans.

Heterodimerization of the prostaglandin E2 receptor EP2 and the calcitonin receptor CTR

G protein-coupled receptors (GPCRs) have been found to form heterodimers and modulate or fine-tune the functions of GPCRs. However, the involvement of GPCR heterodimerization and its functional consequences in gonadal tissues, including granulosa cells, have been poorly investigated, mainly due to the lack of efficient method for identification of novel GPCR heterodimers. In this paper, we identified a novel GPCR heterodimer between prostaglandin E2 (PGE2) receptor 2 (EP2) and calcitonin (CT) receptor (CTR). High-resolution liquid chromatography (LC)-tandem mass spectrometry (MS/MS) of protease-digested EP2-coimmunoprecipitates detected protein fragments of CTR in an ovarian granulosa cell line, OV3121. Western blotting of EP2- and CTR-coimmunoprecipitates detected a specific band for EP2-CTR heterodimer. Specific heterodimerization between EP2 and CTR was also observed by fluorescence resonance energy transfer analysis in HEK293MSR cells expressing cyan- and yellow-fluorescent protein-fused EP2 and CTR, respectively. Collectively, these results provided evidence for heterodimerization between EP2 and CTR. Moreover, Ca²⁺ mobilization by CT was approximately 40% less potent in HEK293MSR cells expressing an EP2-CTR heterodimer, whereas cAMP production by EP2 or CT was not significantly altered compared with cells expressing EP2- or CTR alone. These functional analyses verified that CTR-mediated Ca²⁺ mobilization is specifically decreased via heterodimerization with EP2. Altogether, the present study suggests that a novel GPCR heterodimer, EP2-CTR, is involved in some functional regulation, and paves the way for investigation of novel biological roles of CTR and EP2 in various tissues.

FSH and LH receptors are differentially expressed in cumulus cells surrounding developmentally competent and incompetent mouse fully grown antral oocytes

Cumulus cells (CCs) maintain strict functional relationships with the enclosed antral oocyte and are thought to reflect its developmental competence. Several studies have described a correlation between CC gene expression and oocyte quality. Herein, we tested whether CC-specific FSH and LH receptors (FSHR and LHR, respectively) are differentially expressed in CCs enclosing developmentally competent or incompetent oocytes. To this end, mouse fully grown cumulus-oocyte complexes were isolated and their CCs and oocytes analysed separately. Based on their chromatin organisation, oocytes were classified as those with a surrounded nucleolus (SN) or a non-surrounded nucleolus (NSN), the former being developmentally competent, whereas the latter arrest at the 2-cell stage. The CCs were then analysed to compare the pattern of expression of the Fshr and Lhr genes and their proteins. Quantitative reverse transcription-polymerase chain reaction analysis revealed that only Lhr is significantly differentially expressed. Immunofluorescence analysis revealed that both FSHR and LHR proteins are significantly upregulated in CCs surrounding oocytes arrested at the 2-cell stage, reflecting their developmental incompetence.

Analysis of gene expression in granulosa cells post-maturation to evaluate oocyte culture systems in the domestic cat

Maturation of oocytes is a prerequisite for successful embryo development. The fertilization competence of in vivo derived oocytes is significantly higher than that of oocytes matured in vitro. Commonly evaluated morphological criteria for oocyte maturation do not reflect the complexity and quality of maturation processes. Oocytes and granulosa cells are communicating closely in a bidirectional way during follicular growth and maturation. Assessing the mRNA expression of specific genes in granulosa cells could be a non-invasive way to evaluate the conditions of in vitro oocyte maturation. The objective of this study was to elucidate the influence of two different FSH additives on the in vitro maturation rate and gene expression of cumulus-oocytes complexes in domestic cat. Feline oocytes were matured in a medium, supplemented with LH and 0.02 IU/ml porcine FSH versus 0.02 IU or 1.06 IU/ml human FSH. Granulosa cells were separated from oocytes directly after 24 hr of maturation or after additional 12 hr of in vitro fertilization. Gene expression levels were analysed by quantitative PCR for aromatase, antimullerian hormone, follicle stimulating hormone receptor (FSHR), luteinizing hormone/choriogonadotropin receptor (LHCGR) and prostaglandin E synthase. Neither oocyte maturation rate nor gene expression levels differed after 24 or 36 hr in all three groups. However, variations were discovered in correlations of expression levels, for instance for FSHR and LHCG, indicating differences in the fine-tuning of in vitro maturation processes under varying FSH supplementations. We suppose that correlation between gene expressions of selected genes suggests a superior maturation quality of feline oocytes.

Expression of the Bone Morphogenetic Protein-2 (BMP2) in the Human Cumulus Cells as a Biomarker of Oocytes and Embryo Quality

Background

The members of the transforming growth factor-B superfamily, as the bone morphogenetic proteins (BMPs) subfamily and anti-Müllerian hormone (AMH), play a role during follicular development, and the bone morphogenetic protein-2 (BMP2), AMH, and THY1 are expressed in ovaries.

Aim

This study was designed to define whether or not the expressions of these proteins in human cumulus cells (CCs) can be used as predictors of the oocyte and embryo competence.

Settings and Design

The study included nine female patients who were diagnosed as idiopathic infertility, aged 25-33 years (median 30 years) and underwent Assisted Reproductive Technologies.

Materials and Methods

The CCs from 60 oocyte-cumulus complexes obtained from the nine patients were evaluated with immunofluorescence staining in respect of BMPs, AMH and THY1 markers. The CCs surrounding the same oocytes were evaluated separately according to the oocyte and embryo quality.

Statistical Analysis

Quantitative data were statistically analyzed for differences using the two-sided Mann-Whitney U test (P < 0.05).

Results and Conclusions

Significant differences in immunofluorescence staining were observed in oocyte quality and embryo quality for the BMP2 only (P < 0.05). No significant differences were observed for AMH or CD90/THY1.

Conclusion

These results demonstrated that there is a significant difference in the expression of BMP2 in the CCs of good quality oocytes and subsequently a good embryo.

Differences in cumulus cell gene expression indicate the benefit of a pre-maturation step to improve in-vitro bovine embryo production

STUDY QUESTION

Does the gene expression profile of cumulus cells (CC) accompanying oocytes with different degrees of chromatin compaction within the germinal vesicle (GV) reflect the oocyte's quality and response in culture during in-vitro embryo production (IVP).

SUMMARY ANSWER

The transcriptomic profile of the CC is related to oocyte competence, setting the stage for the development of customized pre-maturation strategies to improve IVP.

WHAT IS KNOWN ALREADY

Oocytes complete the acquisition of their competence during antral follicle development. During this period, the chromatin configuration within the GV changes dynamically and is indicative of oocyte's developmental potential. The interactions between somatic and germ cells modulate chromatin morphology and function and are critical for acquisition of oocyte competence.

STUDY DESIGN, SIZE, DURATION

Bovine cumulus-oocyte complexes (COC) were isolated from 0.5 to 6 mm antral follicles. Surrounding CC were separated from the oocyte and classified as GV0, GV1, GV2 and GV3 according to the degree of the oocyte's chromatin compaction.

PARTICIPANTS/MATERIALS, SETTING, METHOD

RNA extracted from CC of each group was amplified and hybridized on a bovine embryo-specific 44 K Agilent slide. The CC_GV1, CC_GV2 and CC_GV3 classes were each hybridized against the CC_GV0 class, representing an early oocyte differentiation stage with poor development competence. The data were normalized and fold changes of the differentially expressed genes were determined. Microarray data were validated using quantitative RT-PCR on selected targets. Microarray data were further analyzed through: (i) between-group analysis (BGA), which classifies the samples according to their transcriptomic profiles; (ii) cluster analysis according to the expression profile of each gene; and (iii) Ingenuity Pathway Analysis (IPA) to study gene regulation patterns and predicted functions. Furthermore, CC of each GV group were cultured and apoptotic cells were assessed after 3 h by caspase analysis. Finally, based on the analysis of CC transcriptomic profiles and the relationship between morphological features of the COC and the oocyte chromatin configuration, a customized, stage-dependent oocyte pre-maturation (pre-IVM) system was used to improve oocyte developmental potential before IVM. For this, the blastocyst rate and quality were assessed after in-vitro maturation and fertilization of pre-matured oocytes.

MAIN RESULTS AND THE ROLE OF CHANCE

Overall, quantitative RT-PCR results of a subset of five selected genes were consistent with the microarray data. Clustering analysis generated 16 clusters representing the main profiles of transcription modulation. Of the 5571 significantly differentially expressed probes, the majority (25.49%) best fitted with cluster #6 (downregulation between CC_GV0 and CC_GV1 and stable low levels in successive groups). IPA identified the most relevant functions associated with each cluster. Genes included in cluster #1 were mostly related to biological processes such as 'cell cycle' and 'cell death and survival', whereas genes included in cluster #5 were mostly related to 'gene expression'. Interestingly, 'lipid metabolism' was the most significant function identified in clusters #6, #9 and #12. IPA of gene lists obtained from each contrast (i.e., CC_GV0 vs. CC_GV1; CC_GV0 vs. CC_GV2; CC_GV0 vs. CC_GV3) revealed that the main affected function in each contrast was 'cell death and survival'. Importantly, apoptosis was predicted to be inhibited in CC_GV1 and CC_GV2, but activated in CC_GV3. Caspase analysis indicated that a low percentage of CC_GV0 was prone to undergo apoptosis but apoptosis increased significantly in CC from oocytes with condensed chromatin, reaching a peak in CC_GV3 (P < 0.05). Finally, the tailored oocyte pre-maturation strategy, based on morphological features of the COC and the oocyte chromatin configuration, demonstrated that pre-IVM improved the developmental capability of oocytes at early stages of differentiation (GV1-enriched COC) but was detrimental for oocytes at more advanced stages of development (GV2 and GV3-enriched COC).

LARGE SCALE DATA

The data are available through the GEO series accession number GSE79886.

LIMITATIONS, REASONS FOR CAUTION

This study was conducted with bovine samples. Whether or not the results are applicable to human oocytes requests further elucidation. Embryo transfer experiments are required to determine whether the improvement in blastocyst rates in the tailored system leads to increased live birth rates.

WIDER IMPLICATIONS OF THE FINDINGS

The identification of multiple non-invasive biomarkers predictive of oocyte quality can greatly strengthen the pre-IVM approach aimed to improve IVM outcomes. These results have potentially important implications in treating human infertility and in developing breeding schemes for domestic mammals.

STUDY FUNDING/COMPETING INTERESTS

This work was supported in part by NSERC Strategic Network EmbryoGENE, Canada and in part by CIG-Marie Curie Actions-Reintegration Grants within the EU 7FP (n. 303640, 'Pro-Ovum'). The authors declare no potential conflict of interest.

Cited2 protein level in cumulus cells is a biomarker for human embryo quality and pregnancy outcome in one in vitro fertilization cycle

OBJECTIVE

To determine whether the levels of CBP/p300 interacting transactivator with ED-rich tail 2 (Cited2) protein in cumulus cells (CCs) derived from patients undergoing IVF related to infertility factors, embryo quality, and clinical outcomes in one IVF cycle.

DESIGN

Retrospective analysis of human CCs.

SETTING

Public hospital and university.

PATIENT(S)

A total of 103 (conventional) IVF patients and 32 intracytoplasmic sperm injection patients.

INTERVENTION(S)

All CCs from each patient's oocytes were considered as one sample. The patients were divided into two groups according to whether the Cited2/β-actin levels in their CCs were above or below the mean level detected for all patients.

MAIN OUTCOME MEASURE(S)

Embryo quality and clinical outcomes of IVF patients.

RESULT(S)

The oocytes derived from the group of patients whose CCs showed lower Cited2 levels displayed higher fertilization, transferable embryo, and implantation rates. Moreover, the patients in this group were more likely to have a successful pregnancy outcome. Among different infertility factors, a total of 78.6% of patients with polycystic ovary syndrome had a higher Cited2 level in CCs. Additionally, patients with a lower basal FSH level belonged to the higher Cited2 levels group. The expression of two genes (phosphoenolpyruvate carboxykinase 1 [PCK1] and progesterone receptor [PR]) and the glucose content in CCs were also markedly increased in CCs derived from patients with higher Cited2 levels.

CONCLUSION(S)

The present findings imply that Cited2 level in CCs is associated with polycystic ovary syndrome, embryo quality, and pregnancy outcome of IVF patients.

Genomic expression profiles in cumulus cells derived from germinal vesicle and MII mouse oocytes

Cumulus cells (CCs) are distinct from other granulosa cells and the mutual communication between CCs and oocytes is essential for the establishment of oocyte competence. In the present study we assessed genomic expression profiles in mouse CCs before and after oocyte maturation in vitro. Microarray analysis revealed significant changes in gene expression in CCs between the germinal vesicle (GV) and metaphase II (MII) stages, with 2615 upregulated and 2808 downregulated genes. Genes related to epidermal growth factor, extracellular matrix (Ptgs2, Ereg, Tnfaip6 and Efemp1), mitochondrial metabolism (Fdx1 and Aifm2), gap junctions and the cell cycle (Gja1, Gja4, Ccnd2, Ccna2 and Ccnb2) were highlighted as being differentially expressed between the two development stages. Real-time polymerase chain reaction confirmed the validity and reproducibility of the results for the selected differentially expressed genes. Similar expression patterns were identified by western blot analysis for some functional proteins, including EFEMP1, FDX1, GJA1 and CCND2, followed by immunofluorescence localisation. These genes may be potential biomarkers for oocyte developmental competence following fertilisation and will be investigated further in future studies.

Fertility preservation in women with cancer

Enhanced long-term survival rates of young women with cancer and advances in reproductive medicine and cryobiology have culminated in an increased interest in fertility preservation methods in girls and young women with cancer. Present data suggest that young patients with cancer should be referred for fertility preservation counselling quickly to help with their coping process. Although the clinical application of novel developments, including oocyte vitrification and oocyte maturation in vitro, has resulted in reasonable success rates in assisted reproduction programmes, experience with these techniques in the setting of fertility preservation is in its infancy. It is hoped that these and other approaches, some of which are still regarded as experimental (eg, ovarian tissue cryopreservation, pharmacological protection against gonadotoxic agents, in-vitro follicle growth, and follicle transplantation) will be optimised and become established within the next decade. Unravelling the complex mechanisms of activation and suppression of follicle growth will not only expand the care of thousands of women diagnosed with cancer, but also inform the care of millions of women confronted with reduced reproductive fitness because of ageing.

High-throughput analysis of ovarian granulosa cell transcriptome

The quality of follicular oocytes depends on interactions with surrounding granulosa cells. Development of molecular techniques and methods enables better understanding of processes underlying mammalian reproduction on cellular level. The success in reproductive biology and medicine in different species depends on reliable assessment of oocyte and embryo viability which presently mainly bases on embryo morphology. Although successful pregnancies have been achieved using this approach, its precision still should be improved and completed with other, more objective, and accurate assessment strategies. Global profiling of gene expression in follicular cumulus cells using microarrays is continuously leading to the establishment of new biomarkers which can be used to select oocytes with highest developmental potential. Even more potential applications and greater precision could be achieved using next generation sequencing (NGS) of granulosa and cumulus cell RNA (RNA-seq). However, due to the high cost, this method is not used as frequently as microarrays at the moment. In any case, high-throughput technologies offer the possibilities and advantages in ovarian somatic cell analysis on scale that has not been noted so far. The aim of this work is to present current directions and examples of global molecular profiling of granulosa cells and underline its impact on reproductive biology and medicine.

Semi-quantitative measurement of specific proteins in human cumulus cells using reverse phase protein array

BACKGROUND

The ability to predict the developmental and implantation ability of embryos remains a major goal in human assisted-reproductive technology (ART) and most ART laboratories use morphological criteria to evaluate the oocyte competence despite the poor predictive value of this analysis. Transcriptomic and proteomic approaches on somatic cells surrounding the oocyte (granulosa cells, cumulus cells [CCs]) have been proposed for the identification of biomarkers of oocyte competence. We propose to use a Reverse Phase Protein Array (RPPA) approach to investigate new potential biomarkers of oocyte competence in human CCs at the protein level, an approach that is already used in cancer research to identify biomarkers in clinical diagnostics.

METHODS

Antibodies targeting proteins of interest were validated for their utilisation in RPPA by measuring siRNA-mediated knockdown efficiency in HEK293 cells in parallel with Western blotting (WB) and RPPA from the same lysates. The proteins of interests were measured by RPPA across 13 individual human CCs from four patients undergoing intracytoplasmic sperm injection procedure.

RESULTS

The knockdown efficiency of VCL, RGS2 and SRC were measured in HEK293 cells by WB and by RPPA and were acceptable for VCL and SRC proteins. The antibodies targeting these proteins were used for their detection in human CCs by RPPA. The detection of protein VCL, SRC and ERK2 (by using an antibody already validated for RPPA) was then carried out on individual CCs and signals were detected for each individual sample. After normalisation by VCL, we showed that the level of expression of ERK2 was almost the same across the 13 individual CCs while the level of expression of SRC was different between the 13 individual CCs of the four patients and between the CCs from one individual patient.

CONCLUSIONS

The exquisite sensitivity of RPPA allowed detection of specific proteins in individual CCs. Although the validation of antibodies for RPPA is labour intensive, RRPA is a sensitive and quantitative technique allowing the detection of specific proteins from very small quantities of biological samples. RPPA may be of great interest in clinical diagnostics to predict the oocyte competence prior to transfer of the embryo using robust protein biomarkers expressed by CCs.