New candidate genes to predict pregnancy outcome in single embryo transfer cycles when using cumulus cell gene expression

The Nrf2/ARE pathway as a potential target to ameliorate atrazine-induced endocrine disruption in granulosa cells

Atrazine (ATR) is widely used worldwide as a commercial herbicide, Diaminochlorotriazine (DACT) is the main metabolite of ATR in the organism. Both of them disrupt the production of steroids and induce abnormal reproductive development. The granulosa cells (GCs) are important for growth and reproduction of animals. However, the toxicity of ATR on the GCs of birds is not well clarified. To evaluate the effect of the environmental pollutant ATR on bird GCs. The quail GCs were allotted into 7 groups, C (The medium of M199), A20 (20 µM ATR), A100 (100 µM ATR), A250 (250 µM ATR), D20 (20 µM DACT), D100 (100 µM DACT) and D200 (200 µM DACT). The results demonstrated that ATR reduced the viability of GCs, disrupted mitochondrial structure (including mitochondrial cristae fragmentation and the mitochondrial morphology disappearance) and decreased mitochondrial membrane potential. Meanwhile, ATR interfered with the expression of key factors in the steroid synthesis pathway, inducing the secretion of the sex hormones E2 and P in GCs. which in turn induced apoptosis. Furthermore, the Nrf2/ARE pathway as a potential target to ameliorate ATR-induced endocrine disruption in GCs for proper reproductive functions. Our research provides a new perspective for understanding the effects of ATR on reproductive functions in birds.

Use of assisted reproductive technologies (ARTs) to shorten the generational interval in ruminants: current status and perspectives

The challenges posed by climate change and increasing world population are stimulating renewed efforts for improving the sustainability of animal production. To meet such challenges, the contribution of genomic selection approaches, in combination with assisted reproductive technologies (ARTs), to spreading and preserving animal genetics is essential. The largest increase in genetic gain can be achieved by shortening the generation interval. This review provides an overview of the current status and progress of advanced ARTs that could be applied to reduce the generation time in both female and male of domestic ruminants. In females, the use of juvenile in vitro embryo transfer (JIVET) enables to generate offspring after the transfer of in vitro produced embryos derived from oocytes of prepubertal genetically superior donors reducing the generational interval and acceleration genetic gain. The current challenge is increasing in vitro embryo production (IVEP) from prepubertal derived oocytes which is still low and variable. The two main factors limiting IVEP success are the intrinsic quality of prepubertal oocytes and the culture systems for in vitro maturation (IVM). In males, advancements in ARTs are providing new strategies to in vitro propagate spermatogonia and differentiate them into mature sperm or even to recapitulate the whole process of spermatogenesis from embryonic stem cells. Moreover, the successful use of immature cells, such as round spermatids, for intracytoplasmic injection (ROSI) and IVEP could allow to complete the entire process in few months. However, these approaches have been successfully applied to human and mouse whereas only a few studies have been published in ruminants and results are still controversial. This is also dependent on the efficiency of ROSI that is limited by the current isolation and selection protocols of round spermatids. In conclusion, the current efforts for improving these reproductive methodologies could lead toward a significant reduction of the generational interval in livestock animals that could have a considerable impact on agriculture sustainability.

When the Embryo Meets the Endometrium: Identifying the Features Required for Successful Embryo Implantation

Evaluation of the optimal number of embryos, their quality, and the precise timing for transfer are critical determinants in reproductive success, although still remaining one of the main challenges in assisted reproduction technologies (ART). Indeed, the success of in vitro fertilization (IVF) treatments relies on a multitude of events and factors involving both the endometrium and the embryo. Despite concerted efforts on both fronts, the overall success rates of IVF techniques continue to range between 25% and 30%. The role of the endometrium in implantation has been recently recognized, leading to the hypothesis that both the "soil" and the "seed" play a central role in a successful pregnancy. In this respect, identification of the molecular signature of endometrial receptivity together with the selection of the best embryo for transfer become crucial in ART. Currently, efforts have been made to develop accurate, predictive, and personalized tests to identify the window of implantation and the best quality embryo. However, the value of these tests is still debated, as conflicting results are reported in the literature. The purpose of this review is to summarize and critically report the available criteria to optimize the success of embryo transfer and to better understand current limitations and potential areas for improvement.

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

OBJECTIVE

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

DESIGN

Retrospective observational study.

SETTINGS

This study was conducted at a University Hospital in Switzerland.

PATIENTS

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

INTERVENTION(S)

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSION

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

Essential role of Mg2+ in mouse preimplantation embryo development revealed by TRPM7 chanzyme-deficient gametes

TRPM7 (transient receptor potential cation channel subfamily M member 7) is a chanzyme with channel and kinase domains essential for embryo development. Using gamete-specific Trpm7-null lines, we report that TRPM7-mediated Mg2+ influx is indispensable for reaching the blastocyst stage. TRPM7 is expressed dynamically from gametes to blastocysts; displays stage-specific localization on the plasma membrane, cytoplasm, and nucleus; and undergoes cleavage that produces C-terminal kinase fragments. TRPM7 underpins Mg2+ homeostasis, and excess Mg2+ but not Zn2+ or Ca2+ overcomes the arrest of Trpm7-null embryos; expressing Trpm7 mRNA restores development, but mutant versions fail or are partially rescued. Transcriptomic analyses of Trpm7-null embryos reveal an abundance of oxidative stress-pathway genes, confirmed by mitochondrial dysfunction, and a reduction in transcription factor networks essential for proliferation; Mg2+ supplementation corrects these defects. Hence, TRPM7 underpins Mg2+ homeostasis in preimplantation embryos, prevents oxidative stress, and promotes gene expression patterns necessary for developmental progression and cell-lineage specification.

Bioinformatic Analysis of Human Cumulus Cells to Unravel Cellular's Processes that Could Be Used to Establish Oocyte Quality Biomarkers with Clinical Application

Metadata analysis of public microarray datasets using bioinformatics tools has been successfully used in several biomedical fields in the search for biomarkers. In reproductive science, there is an urgent need for the establishment of oocyte quality biomarkers that could be used in the clinical environment to increase the chances of successful outcomes in treatment cycles. Adaptive cellular processes observed in cumulus oophorus cells reflect the conditions of the follicular microenvironment and may thus bring relevant information of oocyte's conditions. Here we analyzed human cumulus cells gene expression datasets in search of predictors of oocyte quality, a strategy which uncovered several cellular processes positively and negatively associated with embryo development and pregnancy potential. Secondly, the expression levels of genes that were present in the majority of processes observed were validated in house with clinical samples. Our data confirmed the association of the selected biomarkers with blastocyst formation and pregnancy potential rates, independently of patients' clinical characteristics such as diagnosis, age, BMI, and stimulation protocol applied. This study shows that bioinformatic analysis of cellular processes can be successfully used to elucidate possible oocyte quality biomarkers. Our data reinforces the need to consider clinical characteristics of patients when selecting relevant biomarkers to be used in the clinical environment and suggests a combination of positive (PTGS2) and negative (CYPB1) quality biomarkers as a robust strategy for a complementary oocyte selection tool, potentially increasing assisted reproduction success rates. Also, GPX4 expression as pregnancy potential biomarker is indicated here as a possibility for further investigations.

The human cumulus cell transcriptome provides poor predictive value for embryo transfer outcome

RESEARCH QUESTION

Is the transcriptome of cumulus cells a good predictor of the embryo's developmental competence?

DESIGN

Cumulus cells were collected from donor oocytes and their transcriptome was analysed by RNA sequencing analysis at >30 × 10⁶ reads in samples grouped according to the developmental potential of their enclosed oocyte: not able to develop to the blastocyst stage (Bl-), able to develop to the blastocyst stage but failing to establish a pregnancy (P-), or able to develop to the blastocyst stage and to establish a clinical pregnancy (P+).

RESULTS

The cumulus cell trancriptome was largely independent of the developmental potential as, using a false dscovery rate-adjusted P-value of <0.05, only 10, 11 and 5 genes were differentially expressed for the comparisons P+ versus P-, P+ versus Bl-, and P- versus Bl-, respectively, out of a total of 17,469 genes expressed. Between the differentially expressed genes, those showing little overlap between samples from different groups were CHAC1, up-regulated in the P- and P+ groups compared with the Bl- group, and CENPE, CD93, PECAM1 and HSPA1B, which showed the opposite expression pattern. Focusing on the pregnancy potential, only EPN3 was consistently downregulated in the P+ compared with the P- and Bl- groups.

CONCLUSIONS

The cumulus cell transcriptome is largely unrelated to the establishment of clinical pregnancy following embryo transfer, although the expression level of a subset of genes in cumulus cells may indicate the ability to develop to the blastocyst stage.

Association of ADAMTS proteoglycanases downregulation with IVF-ET outcomes in patients with polycystic ovary syndrome: a systematic review and meta-analysis

BACKGROUND

A disintegrin and metalloproteinase with thrombospondin-like motifs (ADAMTS) is involved in inflammation and fertility in women with polycystic ovary syndrome (PCOS). This study aims to assess the role of ADAMTS level in the outcomes of in vitro fertilization and embryo transfer (IVF-ET) in women with PCOS, using a meta-analytic approach.

METHODS

We systematically searched Web of Science, PubMed, EmBase, and the Cochrane library to identify potentially eligible studies from inception until December 2021. Study assess the role of ADAMTS levels in patients with PCOS was eligible in this study. The pooled effect estimates for the association between ADAMTS level and IVF-ET outcomes were calculated using the random-effects model.

RESULTS

Five studies involving a total of 181 patients, were selected for final analysis. We noted that ADAMTS-1 levels were positively correlated to oocyte maturity (r = 0.67; P = 0.004), oocyte recovery (r = 0.74; P = 0.006), and fertilization (r = 0.46; P = 0.041) rates. Moreover, ADAMTS-4 levels were positively correlated to oocyte recovery (r = 0.91; P = 0.001), and fertilization (r = 0.85; P = 0.017) rates. Furthermore, downregulation of ADAMTS-1, ADAMTS-4, ADAMTS-5, and ADAMTS-9 was associated with elevated follicle puncture (ADAMTS-1: weighted mean difference [WMD], 7.24, P < 0.001; ADAMTS-4: WMD, 7.20, P < 0.001; ADAMTS-5: WMD, 7.20, P < 0.001; ADAMTS-9: WMD, 6.38, P < 0.001), oocytes retrieval (ADAMTS-1: WMD, 1.61, P < 0.001; ADAMTS-4: WMD, 3.63, P = 0.004; ADAMTS-5: WMD, 3.63, P = 0.004; ADAMTS-9: WMD, 3.20, P = 0.006), and Germinal vesicle oocytes levels (ADAMTS-1: WMD, 2.89, P < 0.001; ADAMTS-4: WMD, 2.19, P < 0.001; ADAMTS-5: WMD, 2.19, P < 0.001; ADAMTS-9: WMD, 2.89, P < 0.001). Finally, the oocytes recovery rate, oocyte maturity rate, fertilization rate, cleavage rate, good-quality embryos rate, blastocyst formation rate, and clinical pregnancy rate were not affected by the downregulation of ADAMTS-1, ADAMTS-4, ADAMTS-5, and ADAMTS-9 (P > 0.05).

CONCLUSIONS

This study found that the outcomes of IVF-EF in patients with PCOS could be affected by ADAMTS-1 and ADAMTS-4; further large-scale prospective studies should be performed to verify these results.

CYP19A1 May Influence Lambing Traits in Goats by Regulating the Biological Function of Granulosa Cells

Simple Summary

Aromatase (CYP19A1), a member of the cytochrome family, is widely expressed in ovarian and granulosa cells and is primarily responsible for the conversion of androgens to estrogens. Increased expression of CYP19A1 in follicular granulosa cells has implications for cell proliferation, steroid hormone secretion, and the expression of related functional indicator genes. We hypothesize that CYP19A1 may indirectly influence lambing numbers in goats by regulating follicular cell growth and development, as well as ovarian ovulation.

Abstract

Abnormal expression of CYP19A1, a gene related to steroid hormone synthesis, causes steroid hormone disruption and leads to abnormal ovulation in granulosa cells. However, the exact mechanism of CYP19A1 regulation is unclear. In this study, we confirmed the localization of CYP19A1 in goat ovarian tissues using immunohistochemistry. Subsequently, we investigated the effects of CYP19A1 on granulosa cell proliferation, steroid hormone secretion, and expression of candidate genes for multiparous traits by overexpressing and silencing CYP19A1 in goat granulosa cells (GCs). The immunohistochemistry results showed that CYP19A1 was expressed in all types of follicular, luteal, and granulosa cells, with subcellular localization results revealing that CYP19A1 protein was mainly localized in the cytoplasm and nucleus. Overexpression of CYP19A1 significantly increased the mRNA levels of CYP19A1, FSHR, and INHBA, which are candidate genes for multiple birth traits in goats. It also promoted cell proliferation, PCNA and Cyclin E mRNA levels in granulosa cells, and secretion of estrogen and progesterone. However, it inhibited the mRNA levels of STAR, CYP11A1, and 3βSHD, which are genes related to steroid synthesis. Silencing CYP19A1 expression significantly reduced CYP19A1, FSHR, and INHBA mRNA levels in granulosa cells and inhibited granulosa cell proliferation and PCNA and Cyclin E mRNA levels. It also reduced estrogen and progesterone secretion but enhanced the mRNA levels of STAR, CYP11A1, and 3βSHD. CYP19A1 potentially influenced the lambing traits in goats by affecting granulosa cell proliferation, hormone secretion, and expression of candidate genes associated with traits for multiple births.

Non-invasive oocyte quality assessment

Oocyte quality is perhaps the most important limiting factor in female fertility; however, the current methods of determining oocyte competence are only marginally capable of predicting a successful pregnancy. We aim to review the predictive value of non-invasive techniques for the assessment of human oocytes and their related cells and biofluids that pertain to their developmental competence. Investigation of the proteome, transcriptome, and hormonal makeup of follicular fluid, as well as cumulus-oocyte complexes are currently underway; however, prospective randomized non-selection-controlled trials of the future are needed before determining their prognostic value. The biological significance of polar body morphology and genetics are still unknown and the subject of debate. The predictive utility of zygotic viscoelasticity for embryo development has been demonstrated, but similar studies performed on oocytes have yet to be conducted. Metabolic profiling of culture media using human oocytes are also limited and may require integration of automated, high-throughput targeted metabolomic assessments in real time with microfluidic platforms. Light exposure to oocytes can be detrimental to subsequent development and utilization of time-lapse imaging and morphometrics of oocytes is wanting. Polarized light, Raman microspectroscopy, and coherent anti-Stokes Raman scattering are a few novel imaging tools that may play a more important role in future oocyte assessment. Ultimately, the integration of chemistry, genomics, microfluidics, microscopy, physics, and other biomedical engineering technologies into the basic studies of oocyte biology, and in testing and perfecting practical solutions of oocyte evaluation, are the future for non-invasive assessment of oocytes.

Role of Granulosa Cells in the Aging Ovarian Landscape: A Focus on Mitochondrial and Metabolic Function

Mitochondria are at the intersection of aging and fertility, with research efforts centered largely on the role that these specialized organelles play in the relatively rapid decline in oocyte quality that occurs as females approach reproductive senescence. In addition to various roles in oocyte maturation, fertilization, and embryogenesis, mitochondria are critical to granulosa cell function. Herein, we provide a review of the literature pertaining to the role of mitochondria in granulosa cell function, with emphasis on how mitochondrial aging in granulosa cells may impact reproduction in female mammals.

Cumulus Cell DNA Damage as an Index of Human Oocyte Competence

The determination of oocyte quality is crucial for achieving effective syngamy post-sperm injection and embryonic development. Cumulus cells (CCs) have been proposed as biomarkers of oocyte quality because of their close bio-dynamic relationship with the oocyte. To determine the quality of the oocyte, CCs were sampled during oocyte preparation for ICSI to determine a CC DNA fragmentation index (CCDFI) of each individual oocyte using a variant of the chromatin dispersion test. One hundred and thirty oocytes were selected and studied from two Spanish fertility clinics, 90 of which were fertilized and developed to embryos. Significant differences were found between the CCDFI of unfertilized and fertilized oocytes (p < .001) and between the CCDFI of embryos that were discarded and those that developed suitable for transfer or cryopreservation (p < .001). Oocyte quality was negatively correlated with CCDFI (Spearman’s rho =  − 0.45; p < .001). Receiver operator characteristics curves (ROC) suggested that a cut-off value of 24% CCDFI was able to discriminate the capacity of the gametes to result in syngamy with a sensitivity and specificity of 75.6% and 65%, respectively. This cut-off supports the application of CCDFI as potential index for the evaluation of the reproductive potential of oocytes prior to fertilization.

Positive effects of amphiregulin on human oocyte maturation and its molecular drivers in patients with polycystic ovary syndrome

STUDY QUESTION

Does use of medium containing amphiregulin improve meiotic maturation efficiency in oocytes of women with polycystic ovary syndrome (PCOS) undergoing in vitro maturation (IVM) preceded by a capacitation culture step capacitation IVM (CAPA-IVM)?

SUMMARY ANSWER

Use of medium containing amphiregulin significantly increased the maturation rate from oocytes retrieved from follicles with diameters <6 or ≥6 mm pre-cultured in capacitation medium.

WHAT IS KNOWN ALREADY

Amphiregulin concentration in follicular fluid is correlated with human oocyte developmental competence. Amphiregulin added to the meiotic trigger has been shown to improve outcomes of IVM in a range of mammalian species.

STUDY DESIGN, SIZE, DURATION

This prospective, randomized cohort study included 30 patients and was conducted at an academic infertility centre in Vietnam from April to December 2019. Patients with PCOS were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

In the first stage, sibling oocytes from each patient (671 in total) were allocated in equal numbers to maturation in medium with (CAPA-AREG) or without (CAPA-Control) amphiregulin 100 ng/ml. After a maturation check and fertilization using intracytoplasmic sperm injection (ICSI), all good quality Day 3 embryos were vitrified. Cumulus cells (CCs) from both groups were collected at the moment of ICSI denudation and underwent a molecular analysis to quantify key transcripts of oocyte maturation and to relate these to early embryo development. On return for frozen embryo transfer (second stage), patients were randomized to have either CAPA-AREG or CAPA-Control embryo(s) implanted. Where no embryo(s) from the randomized group were available, embryo(s) from the other group were transferred. The primary endpoint of the study was meiotic maturation efficiency (proportion of metaphase II [MII] oocytes; maturation rate).

MAIN RESULTS AND THE ROLE OF CHANCE

In the per-patient analysis, the number of MII oocytes was significantly higher in the CAPA-AREG group versus the CAPA-Control group (median [interquartile range] 7.0 [5.3, 8.0] versus 6.0 [4.0, 7.0]; P = 0.01). When each oocyte was evaluated, the maturation rate was also significantly higher in the CAPA-AREG group versus the CAPA-Control group (67.6% versus 55.2%; relative risk [RR] 1.22 [95% confidence interval (CI) 1.08-1.38]; P = 0.001). No other IVM or embryology outcomes differed significantly between the two groups. Rates of clinical pregnancy (66.7% versus 42.9%; RR 1.56 [95% CI 0.77-3.14]), ongoing pregnancy (53.3% versus 28.6%; RR 1.87 [95% CI 0.72-4.85]) and live birth (46.7% versus 28.6%; RR 1.63 [95% CI 0.61-4.39]) were numerically higher in the patients who had CAPA-AREG versus CAPA-Control embryos implanted, but each fertility and obstetric outcome did not differ significantly between the groups. In the CAPA-AREG group, there were significant shifts in CC expression of genes involved in steroidogenesis (STAR, 3BHSD), the ovulatory cascade (DUSP16, EGFR, HAS2, PTGR2, PTGS2, RPS6KA2), redox and glucose metabolism (CAT, GPX1, SOD2, SLC2A1, LDHA) and transcription (NRF2). The expression of three genes (TRPM7, VCAN and JUN) in CCs showed a significant correlation with embryo quality.

LIMITATIONS, REASONS FOR CAUTION

This study included only Vietnamese women with PCOS, limiting the generalizability. Although 100 ng/ml amphiregulin addition to the maturation culture step significantly improved the MII rate, the sample size in this study was small, meaning that these findings should be considered as exploratory. Therefore, a larger patient cohort is needed to confirm whether the positive effects of amphiregulin translate into improved fertility outcomes in patients undergoing IVM.

WIDER IMPLICATIONS OF THE FINDINGS

Data from this study confirm the beneficial effects of amphiregulin during IVM with respect to the trigger of oocyte maturation. The gene expression findings in cumulus indicate that multiple pathways might contribute to these beneficial effects and confirm the key role of the epidermal growth factor system in the stepwise acquisition of human oocyte competence.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the Vietnam National Foundation for Science and Technology Development (NAFOSTED; grant number FWO.106-YS.2017.02) and by the Fund for Research Flanders (FWO; grant number G.OD97.18N). L.N.V. has received speaker and conference fees from Merck, grants, speaker and conference fees from Merck Sharpe and Dohme, and speaker, conference and scientific board fees from Ferring. T.M.H. has received speaker fees from Merck, Merck Sharp and Dohme and Ferring. J.S. reports speaker fees from Ferring Pharmaceuticals and Biomérieux Diagnostics and grants from FWO Flanders, is co-inventor on granted patents on CAPA-IVM methodologies in USA (US10392601B2), Europe (EP3234112B1) and Japan (JP 6806683 registered 08-12-2020) and is a co-shareholder of Lavima Fertility Inc., a spin-off company of the Vrije Universiteit Brussel (VUB, Brussels, Belgium). NA, TDP, AHL, MNHN, SR, FS, EA and UDTH report no financial relationships with any organizations that might have an interest in the submitted work in the previous three years, and no other relationships or activities that could appear to have influenced the submitted work.

TRIAL REGISTRATION NUMBER

NCT03915054.

Accompaniment of Time-Lapse Parameters and Cumulus Cell RNA-Sequencing in Embryo Evaluation

The aim of this study was to investigate the use of time-lapse morphokinetic parameters and cumulus cells transcriptomic profile to achieve a more accurate and non-invasive method in embryo evaluation. Two hundred embryos from 20 couples were evaluated based on morphokinetic characteristics using time-lapse. Embryos were divided into the high-quality, moderate-quality, and bad-quality groups. Non-fertilized oocytes were considered as the fourth group. T5 (time to five cells), S2 (time from three to four cells), and CC2 (time from two to three cells) were recorded. Also, the cumulus cells of the respective oocytes were divided into high-quality, moderate-quality, bad-quality, and non-fertilized groups based on the grading of the embryos. Then their transcriptomic profiles were analyzed by RNA-sequencing. Finally, the correlation between differentially expressed genes and embryo time-lapse parameters was investigated. T5 was the only timing that showed a statistically significant difference between high-quality group and other groups. RNA-sequencing results showed that 37 genes were downregulated and 106 genes were upregulated in moderate, bad-quality, and non-fertilized groups compared to high-quality group (q value < 0.05). These genes were involved in the main biological processes such as cell cycle, DNA repair, cell signaling and communication, transcription, and cell metabolism. Embryos graded in different groups showed different transcriptomic profiles in the related cumulus cells. Therefore, it seems that embryo selection using the combination of cytokinetics and cumulus cells gene expression can improve the accuracy of the embryo selection and pregnancy rate in ART clinics.

Upregulation of Low-Density Lipoprotein Receptor of the Steroidogenesis Pathway in the Cumulus Cells Is Associated with the Maturation of Oocytes and Achievement of Pregnancy

The maturation of the oocyte is influenced by cumulus cells (CCs) and associated with pregnancy rate, whereas the influencing factors have not been completely elucidated in the CCs. In this study, we identified new regulators of CCs for high-quality oocytes and successful pregnancies during assisted reproductive techniques. CCs were collected from cumulus–oocyte complexes (COCs) in young (≤33 years old) and old (≥40 years old) women undergoing intracytoplasmic sperm injection (ICSI) procedures. We screened for factors differentially expressed between young vs. old CCs and pregnancy vs. non-pregnancy using whole mRNA-seq-next-generation sequencing (NGS). We characterized the transcriptome of the CCs to identify factors critical for achieving pregnancy in IVF cycles. Women in the young and old pregnancy groups exhibited the up- and downregulation of multiple genes compared with the non-pregnancy groups, revealing the differential regulation of several specific genes involved in ovarian steroidogenesis in CCs. It was shown that the low-density lipoprotein (LDL) receptor to the steroidogenesis pathway was upregulated in CCs with higher maturity rates of oocytes in the pregnancy group. In conclusion, a higher pregnancy rate is related to the signaling pathway of steroidogenesis by the LDL receptor in infertile women undergoing IVF procedures.

The Function of Cumulus Cells in Oocyte Growth and Maturation and in Subsequent Ovulation and Fertilization

Cumulus cells (CCs) originating from undifferentiated granulosa cells (GCs) differentiate in mural granulosa cells (MGCs) and CCs during antrum formation in the follicle by the distribution of location. CCs are supporting cells of the oocyte that protect the oocyte from the microenvironment, which helps oocyte growth and maturation in the follicles. Bi-directional communications between an oocyte and CCs are necessary for the oocyte for the acquisition of maturation and early embryonic developmental competence following fertilization. Follicle-stimulation hormone (FSH) and luteinizing hormone (LH) surges lead to the synthesis of an extracellular matrix in CCs, and CCs undergo expansion to assist meiotic resumption of the oocyte. The function of CCs is involved in the completion of oocyte meiotic maturation and ovulation, fertilization, and subsequent early embryo development. Therefore, understanding the function of CCs during follicular development may be helpful for predicting oocyte quality and subsequent embryonic development competence, as well as pregnancy outcomes in the field of reproductive medicine and assisted reproductive technology (ART) for infertility treatment.

Cumulus cells of euploid versus whole chromosome 21 aneuploid embryos reveal differentially expressed genes

RESEARCH QUESTION

Can cumulus cells be used as a non-invasive target for the study of determinants of preimplantation embryo quality?

DESIGN

Cumulus cells were collected from monosomy 21, trisomy 21 and euploid embryos and subjected to RNA sequencing analysis and real-time polymerase chain reaction assays. The differential gene expression was analysed for different comparisons.

RESULTS

A total of 3122 genes in monosomy 21 cumulus cells and 19 genes in trisomy 21 cumulus cells were differentially expressed compared with euploid cumulus cells. Thirteen of these genes were differentially expressed in both monosomy and trisomy 21, compared with euploid, including disheveled segment polarity protein 2 (DVL2), cellular communication network factor 1 (CCN1/CYR61) and serum response factor (SRF), which have been previously implicated in embryo developmental competence. In addition, ingenuity pathway analysis revealed cell-cell contact function to be affected in both monosomy and trisomy 21 cumulus cells.

CONCLUSIONS

These findings support the use of cumulus cell gene expression analysis for the development of biomarkers evaluating oocyte quality for patients undergoing fertility preservation of oocytes.

Improved clinical outcomes after non-invasive oocyte selection and Day 3 eSET in ICSI patients

BACKGROUND

Non-invasive oocyte quality scoring, based on cumulus gene expression analysis, in combination with morphology scoring, can increase the clinical pregnancy (CPR) and live birth rates (LBR) in Day 3 eSET (elective single embryo transfer) ICSI patients. This was first investigated in a pilot study and is now confirmed in a large patient cohort of 633 patients. It was investigated whether CPR, LBR and time-to-pregnancy could be improved by analyzing the gene expression profile of three predictive genes in the cumulus cells, compared to patients with morphology-based embryo selection only.

METHODS

A large interventional, non-randomized, assessor-blinded cohort study with 633 ICSI patients was conducted in a tertiary fertility center. Non-PCOS patients, 22-39 years old, with good ovarian reserve, were stimulated with HP-hMG using a GnRH antagonist protocol and planned for fresh Day 3 eSET. The cumulus cells from individually denuded oocytes were ranked by a lab-developed cumulus cell test: qRT-PCR for three predictive genes (CAMK1D, EFNB2 and SASH1) and two control genes (UBC, B2M). The embryo selected for transfer was highest ranked from the pool of morphologically transferable Day 3 embryos. Patients in the control (n = 520) and experimental arm (n = 113) were compared for clinical pregnancy and live birth, using a weighted generalized linear model, and time-to-pregnancy using Kaplan-Meier curves.

RESULTS

The CPR was 61% in the experimental arm (n = 113) vs 29% in the control arm (n = 520, p < 0.0001). The LBR in the experimental arm (50%) was significantly higher than in the control arm (27%,p < 0.0001). Time-to-pregnancy was significantly shortened by 3 transfer cycles independent of the number of embryos available on Day 3 (Kaplan-Meier, p < 0.0001). Cumulus cell tested patients < 35 years (n = 65) or ≥ 35 years (n = 48) had a CPR of 62 and 60% respectively (ns). For cumulus cell tested patients with 2, 3-4, or > 4 transferable embryos, the CPR was 66, 52, and 67% (ns) respectively, and thus independent of the number of transferable embryos on Day 3.

CONCLUSIONS

This study provides further evidence of the clinical usefulness of the non-invasive cumulus cell test over time in a larger patient cohort.

TRIAL REGISTRATION

Clinicaltrials.gov, NCT03659786 / NCT02962466 (Registered 6Sep2018/11Nov2016, retrospectively registered.

Morphokinetic analysis of cleavage stage embryos and assessment of specific gene expression in cumulus cells independently predict human embryo development to expanded blastocyst: a preliminary study

To assess whether morphokinetic features at the cleavage stage together with specific gene expression in cumulus cells (CCs) may be used to predict whether human embryos are able to achieve the expanded blastocyst stage on day 5. Eighty-one embryos were cultured using the Geri plus® time-lapse system. Twenty-seven embryos progressing to the expanded blastocyst stage (BL group) were compared with thirty-five embryos showing developmental arrest (AR group) and nineteen reaching the stage of early or not fully expanded blastocyst (nBL group). The analyzed morphokinetic variables were pronuclear appearance (tPNa), pronuclear fading (tPNf), and completion of cleavage to two, three, four, and eight cells (t2, t3, t4, and t8). CCs were analyzed by RT-qPCR for bone morphogenetic protein 15 (BMP15), cytochrome c oxidase subunit II (COXII), ATP synthase subunit 6 (MT-ATP6), connexin 43 (Cx43), and heme oxygenase-1 (HO-1). Embryos of BL group showed a significantly faster kinetic. BMP15, COXII, and MT-ATP6 mRNA expression was significantly higher in CCs of BL group embryos, whereas Cx43 and HO-1 mRNA levels were higher in AR group. Kinetic parameters and gene expression were not significantly different between either the BL and nBL groups or the AR and nBL groups. ROC curves showed that the most predictive cut-offs were t2 < 26.25 for morphokinetics and COXII > 0.3 for gene expression. Multivariable logistic regression analysis showed that morphokinetic variables and gene expression were both valuable, independent predictors of embryo development to expanded blastocyst. Our results suggest the possibility of developing integrated prediction models for early embryo selection at the cleavage stage.

Mitochondrial Function in Modulating Human Granulosa Cell Steroidogenesis and Female Fertility

Ovarian follicle steroidogenesis associated with embryo quality results in a successful pregnancy. Each follicle consists of an oocyte surrounded by granulosa cells, which secrete several steroid and peptide hormones. Follicles harvested from women who conceived after assisted reproductive therapy (ART) had significantly higher estradiol levels in follicular fluids than the follicles from women who failed to conceive after ART. The higher follicular estradiol levels correlate well with successful fertilization following ART. Mitochondria are the central sites for steroid hormone biosynthesis. The first and rate-limiting step in the biosynthesis of steroid hormones occurs in the mitochondria of granulosa cells. In the present study, we hypothesized that the mitochondria in granulosa cells are critical for maintaining oocyte quality and fertility capacity. This study aims to clarify the relationship between mitochondrial function and granulosa cell steroidogenesis, and the relationship between hormone levels and fertility capacity. Sera, follicular fluids and granulosa cells were obtained from individuals undergoing IVF-ET treatment. The oocyte numbers, oocyte quality, fertilization rate, and pregnancy rate were also recorded. The patients who provided the granulosa cells were further classified into four groups: endometriosis, ovarian endometrioma, endometriosis without ovarian endometrioma, and polycystic ovary syndrome (PCOS); patients with other female factor infertility and male factor infertility were used as controls. We measured the levels of estradiol (E2) by radioimmunoassay. Concurrently, we analyzed the mitochondrial mass and membrane potential, and apoptosis by flow cytometry using nonyl acridine orange, TMRE, Annexin V-FITC and PI. Mitochondrial morphology was visualized by transfection with pLV-mitoDsRed. In addition, we assessed the protein levels of steroidogenic enzymes, steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) by Western blot. The results showed significantly decreased serum E2 and follicular E2 levels, and decreased IVF outcomes, in the patients with endometriosis. Reduced mitochondrial mass and decreased mitochondrial membrane potential were correlated with lower E2. Furthermore, a significant decrease in StAR and 3β-HSD was found in patients with ovarian endometrioma. The enzyme levels of StAR and 3β-HSD were highly correlated with E2 levels. Finally, elevated cumulus cell apoptosis was found in the patient group with ovarian endometrioma and PCOS. In conclusion, mitochondrial dysfunction of human granulosa cells may contribute to the decline of steroidogenesis, decreased fertilization rate, oocyte maturation rate, and oocyte quality, and it can ultimately jeopardize fertility.

An integrated investigation of oocyte developmental competence: expression of key genes in human cumulus cells, morphokinetics of early divisions, blastulation, and euploidy

PURPOSE

To investigate the association of cumulus cell (CC)-related expression of a selected cluster of key genes (PTGS2, CAMK1D, HAS2, STC1, and EFNB2) with embryo development to blastocyst.

METHODS

Exploratory study at a private clinic. Eighteen advanced maternal age patients were enrolled (37.3 ± 4.0 years). Seventy-five cumuli were collected, whose oocytes resulted in either developmental arrest (N = 33) or blastocyst formation (N = 42). The noninvasive CC gene expression was combined with time-lapse morphokinetic parameters and, for blastocysts, with qPCR-based aneuploidy testing on trophectoderm biopsies.

RESULTS

The detection rate was 100% for all transcripts, but STC1 (96%) and CAMK1D (89%). Among amplified assays, CC mean expression levels of CAMK1D, PTGS2, and HAS2 were higher from oocytes that developed to blastocyst. No difference in CC key gene expression was reported between euploid (N = 21) and aneuploid (N = 21) blastocysts. Some timings of early embryo development were faster in embryos developing to blastocyst (time of pronuclei appearance and fading, division to two- and four-cells, first and second cell cycles). However, the generalized linear models outlined increasing CAMK1D expression levels as the strongest parameter associated with oocytes' developmental potential from both a general (AUC = 0.78 among amplified samples) and an intrapatient perspectives (AUC = 0.9 among patients obtaining ≥ 2 zygotes from the cohort with different developmental outcomes).

CONCLUSIONS

CAMK1D level of expression in CCs associated with blastocyst development. If confirmed from larger studies in wider populations of patients, the investigation of CC key gene expression might suit IVF clinics not adopting blastocyst culture. Future investigations should clarify the role of CAMK1D in ovarian physiology and could provide novel insights on how oocytes gain competence during folliculogenesis.

Association between early embryo morphokinetics plus cumulus cell gene expression and assisted reproduction outcomes in polycystic ovary syndrome women

RESEARCH QUESTION

Can a combination of time-lapse morphokinetic parameters and cumulus cell gene expression in polycystic ovary syndrome (PCOS) women be used to predict assisted reproductive treatment outcome?

DESIGN

A total of 547 embryos from 100 intracytoplasmic sperm injection (ICSI) cycles were evaluated. Fifty women with PCOS and 50 women who were categorized as tubal factor infertility were recruited. Time-lapse records were annotated for time to pronuclear fading (tPNf), time to 2 to 8 cells (t2-t8), reverse cleavage, direct cleavage and also for the presence of multinucleation. Expression levels of three genes involved in mitotic divisions, diaphanous-related formin 2 (DIAPH2), nibrin (NBN) and NIMA-related protein kinase (NEK4), were measured in 100 associated cumulus cell samples using quantitative real-time polymerase chain reaction.

RESULTS

Expression of DIAPH2 and NBN was significantly higher in the embryos of PCOS patients that resulted in implantation, biochemical and clinical pregnancies as well as live birth compared with embryos that were negative for these outcomes (P <0.01). However, in the tubal factor group, NBN gene expression was significantly higher in embryos resulting in biochemical pregnancy, clinical pregnancy and live birth (P <0.01) only. Multivariate logistic regression analysis showed that tPNf together with DIAPH2 gene expression were independent prognostic factors of clinical pregnancy rate and live birth in both groups.

CONCLUSIONS

Some time-lapse embryo parameters may be related to cumulus gene expression and clinical outcome. Furthermore, the expressions of cumulus cell genes involved in mitotic divisions are significantly associated with ICSI outcome using Day 3 embryo transfer.

Assessment of Prostaglandin-Endoperoxide Synthase 2 and Versican gene expression profile from the cumulus cells: association with better in vitro fertilization outcomes

BACKGROUND

Current methods for determining superior embryo quality (morphological assessment) are unable to compensate for poor pregnancy outcomes. Due to the importance of the cumulus-oocyte complex and the value of cumulus cells (CCs) as markers of embryo health, we determined the association between the CCs gene expression of the Prostaglandin-Endoperoxide Synthase 2 (PTGS2) and Versican (VCAN) with pregnancy.

METHODS

One hundred forty-nine women, suffering from infertility and undergoing IVF, were included in this study (age: 29-46 years; BMI = 25.5 ± 5.0 kg/m²). Patients underwent a standard IVF protocol. CCs were isolated during oocyte retrieval, and their RNA was isolated using Trizol. The mRNA expression of PTGS2, VCAN, and L19 was measured by qPCR. The PVL index, (PTGS2 + VCAN)*L19_normalized, was determined for each oocyte. Clinical pregnancy was confirmed by β-hCG and the presence of a fetal heartbeat. Associations were determined by ROC curves or logistic regression.

RESULTS

There was no correlation between the PVL index and morphological scores. Using only single embryo transfers (SETs), we determined that the PVL index was associated with pregnancy (β-hCG: AUC = 0.87, 95%CI: 0.74-1.00) with an optimal cutoff value of 58.2. Using the complete cohort (consisting of SETs, and patients with 2, 3, or 4 embryos transferred), the presence of at least one embryo with a PVL index score ≥ 58.2 was associated with a greater probability of achieving pregnancy (β-hCG: odds ratio = 17.15, 95%CI: 6.82-43.18, p < 0.001).

CONCLUSION

Transferring at least one embryo with a PVL index score ≥ 58.2, generates a higher chance of achieving pregnancy.

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.

DHEA protects mitochondria against dual modes of apoptosis and necroptosis in human granulosa HO23 cells

Because ovarian granulosa cells are essential for oocyte maturation and development, we validated human granulosa HO23 cells to evaluate the ability of the DHEA to prevent cell death after starvation. The present study was aimed to investigate whether DHEA could protect against starvation-induced apoptosis and necroptosis in human oocyte granulosa HO23 cells. The starvation was induced by treatment of serum-free (SF) medium for 4 h in vitro Starvation-induced mitochondrial depolarization, cytochrome c release and caspase-3 activation were largely prevented by DHEA in HO23 cells. We found that treatment with DHEA can restore starvation-induced reactive oxygen species (ROS) generation and mitochondrial membrane potential imbalance. In addition, treatment of DHEA prevents cell death via upregulation of cytochrome c and downregulation of BAX in mitochondria. Most importantly, DHEA is ameliorated to mitochondrial function mediated through the decrease in mitochondrial ROS, maintained mitochondrial morphology, and enhancing the ability of cell proliferation and ROS scavenging. Our present data strongly indicate that DHEA reduces programmed cell death (apoptosis and necroptosis) in granulosa HO23 cells through multiple interactions with the mitochondrion-dependent programmed cell death pathway. Taken together, our data suggest that the presence of DHEA could be beneficial to protect human oocyte granulosa HO23 cells under in vitro culture conditions during various assisted reproductive technology (ART) programs.Free Chinese abstract: A Chinese translation of this abstract is freely available at http://www.reproduction-online.org/content/154/2/101/suppl/DC1.

Zona pellucida gene mRNA expression in human oocytes is related to oocyte maturity, zona inner layer retardance and fertilization competence

STUDY QUESTION

Do the mRNA expression levels of zona pellucida (ZP) genes, ZP1, 2, 3 and 4 in oocyte and cumulus cells (CC) reveal relevant information on the oocyte?

SUMMARY ANSWER

The ZP mRNA expression in human oocytes is related to oocyte maturity, zona inner layer (IL) retardance and fertilization capacity.

WHAT IS KNOWN ALREADY

ZP structure and birefringence provide useful information on oocyte cytoplasmic maturation, developmental competence for embryonic growth, blastocyst formation and pregnancy. In order to understand the molecular basis of morphological changes in the ZP, in the current study, the polarized light microscopy (PLM) approach was combined with analysis of the expression of the genes encoding ZP1, 2, 3 and 4, both in the oocytes and in the surrounding CC.

STUDY DESIGN, SIZE, DURATION

This is a retrospective study comprising 98 supernumerary human cumulus oocyte complexes (COC) [80 Metaphase II (MII), 10 Metaphase I (MI) and 8 germinal vesicle (GV)] obtained from 39 patients (median age 33.4 years, range 22-42) after controlled ovarian stimulation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Single oocytes and their corresponding CC were analysed. Oocytes were examined using PLM, and quantitative RT-PCR was performed for ZP1, 2, 3 and 4 in these individual oocytes and their CC. Ephrin-B2 (EFNB2) mRNA was measured in CC as a control. Presence of ZP3 protein in CC and oocytes was investigated using immunocytochemistry. Data were analysed using one-parametric and multivariate analysis and were corrected for the potential impact of patient and cycle characteristics.

MAIN RESULTS AND THE ROLE OF CHANCE

Oocytes contained ZP1/2/3 and 4 mRNA while in CC only ZP3 was quantifiable. Also ZP3 protein was detected in human CC. When comparing mature (MII) and immature oocytes (MI/GV) or their corresponding CC, ZP1/2 and 4 expression was lower in mature oocytes compared to the expression in immature oocytes (all P < 0.05) and ZP3 expression was lower in the CC of mature oocytes compared to the expression in CC of immature oocytes (P < 0.05). This coincided with a significantly smaller IL-ZP area and thickness in mature oocytes than in immature oocytes (all P < 0.05). In mature oocytes, IL-ZP retardance was significantly correlated with the expression of all four ZP mRNAs (all P < 0.05). The oocyte ZP3 expression was the main predictor of the fertilization capacity, next to IL-retardance and IL-thickness. Using stepwise regression analysis, IL-thickness combined with EFNB2 expression in CC and the patient's ovarian response resulted in a noninvasive oocyte fertilization prediction model.

LARGE SCALE DATA

Not applicable.

LIMITATIONS, REASONS FOR CAUTION

This is a retrospective study and the relation of oocyte mRNA levels to fertilization capacity is indirect as oocyte gene expression analysis required lysis of the oocyte.

WIDER IMPLICATIONS OF THE FINDINGS

Overall relations between PLM observations, mRNA expression changes and intrinsic oocyte competence were successfully documented. As such PLM and CC gene expression are confirmed as valuable noninvasive techniques to evaluate oocyte competence.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by University of Torino, Italy, WFWG UZ-Brussel and Agentschap voor Innovatie door Wetenschap en Technologie IWT 110680, Belgium. All authors declare that their participation in the study did not involve actual or potential conflicts of interests.

Cumulus cell transcriptome profiling is not predictive of live birth after in vitro fertilization: a paired analysis of euploid sibling blastocysts

OBJECTIVE

To compare the transcriptome of cumulus cells associated with a euploid embryo that resulted in live birth with that of a sibling euploid embryo without sustained implantation.

DESIGN

Paired analysis.

SETTING

Academic institution.

PATIENT(S)

Couples undergoing in vitro fertilization (IVF)/intracytoplasmic sperm injection with preimplantation genetic screening with female age ≤42 years and normal ovarian reserve.

INTERVENTION(S)

Transcriptome profiling of cumulus cells from sibling oocytes for correlation with live birth after euploid blastocyst transfer. Embryos were individually cultured to facilitate association with clinical outcomes. The cumulus cell transcriptome from the embryo resulting in live birth was compared with that of its sibling embryo without sustained implantation to investigate potential biomarkers that may aid in embryo selection.

MAIN OUTCOME MEASURE(S)

Differential gene expression in cumulus cells associated with a euploid embryo resulting in live birth and its sibling euploid embryo without sustained implantation using next-generation RNA sequencing (RNAseq).

RESULT(S)

Cumulus cell RNAseq of 34 samples (from 17 patients) generated an average of 10.4 ± 4 × 10⁶ reads per sample. A total of 132 differentially expressed genes between sibling embryos that resulted in a live birth and those that did not were identified (P<.05). However, after correcting for multiple testing none of the genes remained significantly differentially expressed (false discovery rate <.05).

CONCLUSION(S)

The RNAseq profiles were similar between cumulus cells associated with a euploid embryo resulting in live birth and its sibling embryo that did not sustain implantation. The cumulus cell transcriptome is not predictive of live birth within an individual patient's cohort of euploid embryos.

"Bone Development" Is an Ontology Group Upregulated in Porcine Oocytes Before In Vitro Maturation: A Microarray Approach

Mammalian cumulus-oocyte complexes (COCs) reach full developmental capability during folliculogenesis and oogenesis. It is well recognized that only gametes achieving MII stage after in vivo or in vitro maturation (IVM) are successfully fertilized by a single spermatozoon. Although the process of oocyte nuclear and/or cytoplasmic maturation in pigs is well determined, there exist many differences that promote these processes in vivo and in vitro. Therefore, this study aimed to investigate the differences in RNA expression profiles between porcine oocytes before and after IVM using microarray and real-time quantitative polymerase chain reaction (RT-qPCR) assays. Experiments were performed on oocytes isolated from 55 pubertal crossbred Landrace gilts. The oocytes were analyzed both before and after IVM and only Brilliant Cresyl Blue (BCB)-positive gametes were used for subsequent microarray analysis (Affymetrix) and RT-qPCR analysis. The microarray assay, which measures expression of 12,258 transcripts, revealed 419 differentially expressed transcripts in porcine oocytes, from which 379 were downregulated and 40 were upregulated before IVM compared to those analyzed after IVM. After DAVID analysis, we found eight different transcripts, including IHH, BMP1, WWTR1, CHRDL1, KLF10, EIF2AK3, MMP14, and STC1. Their expression is related to the "bone development" ontology group and was further subjected to hierarchical clusterization. Using RT-qPCR analysis, we confirmed the results of the microarray assay, showing increased expression of the eight genes in oocytes before IVM compared to oocytes after maturation in vitro. It has been suggested that "bone development" belongs to one ontological group involving genes substantially upregulated in porcine oocytes before IVM. We suggest that the gamete mRNA expression profile before IVM may comprise stored transcripts, which are templates for protein biosynthesis following fertilization. We also hypothesize that these mRNAs may be a specific "fingerprint" of folliculogenesis and oogenesis in pigs.

Effects of melatonin on maturation, histone acetylation, autophagy of porcine oocytes and subsequent embryonic development

Melatonin (MLT) is an endogenous hormone with roles in animal germ cell development. However, the effect of MLT on porcine oocyte maturation and its underlying mechanisms remain largely unknown. Here, we investigated the effects of exogenous MLT on oocyte maturation, histone acetylation, autophagy and subsequent embryonic development. We found that 1 nmol/L MLT supplemented in maturation medium was the optimal concentration to promote porcine oocyte maturation and subsequent developmental competence and quality of parthenogenetic embryos. Interestingly, the beneficial effects of 1 nmol/L MLT treatment on porcine oocyte maturation and embryo development were mainly attributed to the first half period of in vitro maturation. Simultaneously, MLT treatment could also improve maturation of small follicle-derived oocytes, morphologically poor (cumulus cell layer ≤1) and even artificially denuded oocytes and their subsequent embryo development. Furthermore, MLT treatment not only could decrease the levels of H3K27ac and H4K16ac in metaphase II (MII) oocytes, but also could increase the expression abundances of genes associated with cumulus cell expansion, meiotic maturation, histone acetylation and autophagy in cumulus cells or MII oocytes. These results indicate that MLT treatment can facilitate porcine oocyte maturation and subsequent embryonic development probably, through improvements in histone acetylation and autophagy in oocytes.

The Application of Dehydroepiandrosterone on Improving Mitochondrial Function and Reducing Apoptosis of Cumulus Cells in Poor Ovarian Responders

Poor ovarian responders (PORs) pose a great challenge for in vitro fertilization (IVF). Previous studies have suggested that dehydroepiandrosterone (DHEA) may improve IVF outcomes in PORs. The current study attempted to investigate the clinical benefits of DHEA in PORs and the possible mechanisms of DHEA on cumulus cells (CCs). This was a prospective study performed at one tertiary center from January 2015 to March 2016. A total of 131 women who underwent IVF treatment participated, including 59 normal ovarian responders (NORs) and 72 PORs. PORs were assigned to receive DHEA supplementation or not before the IVF cycle. For all patients, CCs were obtained after oocyte retrieval. In the CCs, mRNA expression of apoptosis-related genes and mitochondrial transcription factor A (TFAM) gene, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, mitochondrial dehydrogenase activity and mitochondrial mass were measured. The results indicated that PORs with DHEA supplementation produces a great number of top-quality embryos at day 3 and increased the number of transferred embryos and fertilization rate compared with those without DHEA supplementation. Additionally, supplementation with DHEA in PORs decreased DNA damage and apoptosis in CCs while enhancing the mitochondrial mass, mitochondrial dehydrogenase activity and TFAM expression in CCs. In conclusion, our results showed that the benefits of DHEA supplementation on IVF outcomes in PORs were significant, and the effects may be partially mediated by improving mitochondrial function and reducing apoptosis in CCs.

Granulosa cell biomarkers to predict pregnancy in ART: pieces to solve the puzzle

Cumulus and mural granulosa cells of the ovarian follicle surround and interact with the developing oocyte. These follicular cells reflect the oocyte's overall health and may indicate subsequent developmental competence of embryos. Biomarkers of granulosa cells associated with individual oocytes could potentially be used in assisted reproduction to indicate which embryos have the best chance of implanting in the uterus and completing gestation. In this review, we have performed a comprehensive assessment of the recent literature for human cumulus and mural granulosa cell mRNA biomarkers as they relate to pregnancy and live birth. A critical discussion of variables affecting granulosa gene expression profiles for in vitro fertilization patients, including patient demographics and ovarian stimulation regimens, is presented. Although studies with microarray data were evaluated, this synopsis focuses on expressed genes that have been validated by quantitative RT-PCR. Furthermore, we summarize the current published data that support or refute identified granulosa expressed genes as potential biomarkers of embryos that give rise to ongoing pregnancy and live birth. Finally, we review studies that offer predictive models for embryo selection for uterine transfer based on biomarkers that show differential gene expression.

[Biomarkers of the cumulus cells in medically assisted procreation: State-of-the-art]

The oocyte grows within a follicle composed of layers of somatic cells. It undergoes with the cumulus cells that form the innermost layer a dialogue that is critical for its maturation. Based on the assumption that the transcriptome of the cumulus cells reflects the physiology of the oocyte, it may prove a useful non-invasive tool in embryo selection to improve assisted reproduction outcomes. During the past decade, various studies have been conducted with the objective of identifying cumulus biomarker genes as prognosis tools for oocyte quality and competence. Remarkably no common biomarkers stand out among all these studies. In this review we perform a critical analysis of the literature in order to reveal some of the parameters that may account for these discrepancies, such as patients' inclusion criteria (maternal age, stimulation protocols), day of embryo transfer (day 3 or 5), outcome criteria (oocyte potential, embryo competence, pregnancy). Moreover there is a lack of standardization in the experimental designs used for RNA extraction and gene expression assessment (microarrays, RT-qPCR) and for the statistical analyses. In conclusion, critical analyses such as the present one are indispensable to pave the way for future searches of predictive biomarkers of pregnancy.

Competence Classification of Cumulus and Granulosa Cell Transcriptome in Embryos Matched by Morphology and Female Age

Objective

By focussing on differences in the mural granulosa cell (MGC) and cumulus cell (CC) transcriptomes from follicles resulting in competent (live birth) and non-competent (no pregnancy) oocytes the study aims on defining a competence classifier expression profile in the two cellular compartments. Design: A case-control study. Setting: University based facilities for clinical services and research. Patients: MGC and CC samples from 60 women undergoing IVF treatment following the long GnRH-agonist protocol were collected. Samples from 16 oocytes where live birth was achieved and 16 age- and embryo morphology matched incompetent oocytes were included in the study.

Methods

MGC and CC were isolated immediately after oocyte retrieval. From the 16 competent and non-competent follicles, mRNA was extracted and expression profile generated on the Human Gene 1.0 ST Affymetrix array. Live birth prediction analysis using machine learning algorithms (support vector machines) with performance estimation by leave-one-out cross validation and independent validation on an external data set.

Results

We defined a signature of 30 genes expressed in CC predictive of live birth. This live birth prediction model had an accuracy of 81%, a sensitivity of 0.83, a specificity of 0.80, a positive predictive value of 0.77, and a negative predictive value of 0.86. Receiver operating characteristic analysis found an area under the curve of 0.86, significantly greater than random chance. When applied on 3 external data sets with the end-point outcome measure of blastocyst formation, the signature resulted in 62%, 75% and 88% accuracy, respectively. The genes in the classifier are primarily connected to apoptosis and involvement in formation of extracellular matrix. We were not able to define a robust MGC classifier signature that could classify live birth with accuracy above random chance level.

Conclusion

We have developed a cumulus cell classifier, which showed a promising performance on external data. This suggests that the gene signature at least partly include genes that relates to competence in the developing blastocyst.

Gene expression of cumulus cells in women with poor ovarian response after dehydroepiandrosterone supplementation

OBJECTIVE

Our previous study showed the potential benefits of dehydroepiandrosterone (DHEA) supplementation in women with a poor ovarian response (POR). Because the connection between cumulus cells (CCs) and oocytes is a key step for oocyte maturation, we supposed that altered gene expression of CCs in women with POR after DHEA supplementation might favor oocyte maturation.

MATERIALS AND METHODS

Women with POR treated with flexible daily gonadotropin-releasing hormone antagonist in vitro fertilization (IVF) cycles at The Reproductive Center in Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan between January 2013 and October 2013 were enrolled for this prospective study. CCs were isolated during IVF before and after DHEA (CPH-Formulation, Oakdale, CA, USA) supplementation. Nine genes of isolated CCs, including hyaluronan synthase (HAS2), versican (VCAN), thrombospondin 1 (THBS1), runt-related transcription factor 2 (RUNX2), chromobox homolog 3 (CBX3), tripartite motif-containing 28 (TRIM28), B-cell lymphoma 2 (BCL2), BCL2-associated X protein (BAX), and ankyrin repeat domain 57 (ANKRD57), were compared.

RESULTS

There was a significant difference in the expression of genes in women with POR before and after DHEA supplementation (all p < 0.05). All genes related to extracellular matrix (ECM) formation, including HAS2, VCAN, and THBS1, were upregulated. By contrast, all genes involving cell development, differentiation, and apoptosis regulation were downregulated. Unknown function gene ANKRD57 was also downregulated after DHEA supplementation. Although expressions of both BCL2 and BAX were decreased in women with POR after DHEA supplementation compared to those before treatment, the ratio of BCL2 and BAX was significantly increased in women with POR after DHEA supplementation, suggesting that DHEA supplementation might activate the antiapoptosis process of CCs, which might be beneficial to the improvement of ovarian function in women with POR.

CONCLUSION

The study showed that DHEA therapy positively affected the gene expression of CCs in women with POR, and provided evidence to support the positive effect of DHEA supplementation on women with POR.

Cell-free DNA in Human Follicular Microenvironment: New Prognostic Biomarker to Predict in vitro Fertilization Outcomes

Cell-free DNA (cfDNA) fragments, detected in blood and in other biological fluids, are released from apoptotic and/or necrotic cells. CfDNA is currently used as biomarker for the detection of many diseases such as some cancers and gynecological and obstetrics disorders. In this study, we investigated if cfDNA levels in follicular fluid (FF) samples from in vitro fertilization (IVF) patients, could be related to their ovarian reserve status, controlled ovarian stimulation (COS) protocols and IVF outcomes. Therefore, 117 FF samples were collected from women (n = 117) undergoing IVF/Intra-cytoplasmic sperm injection (ICSI) procedure and cfDNA concentration was quantified by ALU-quantitative PCR. We found that cfDNA level was significantly higher in FF samples from patients with ovarian reserve disorders (low functional ovarian reserve or polycystic ovary syndrome) than from patients with normal ovarian reserve (2.7 ± 2.7 ng/μl versus 1.7 ± 2.3 ng/μl, respectively, p = 0.03). Likewise, FF cfDNA levels were significant more elevated in women who received long ovarian stimulation (> 10 days) or high total dose of gonadotropins (≥ 3000 IU/l) than in women who received short stimulation duration (7–10 days) or total dose of gonadotropins < 3000 IU/l (2.4 ± 2.8 ng/μl versus 1.5 ± 1.9 ng/μl, p = 0.008; 2.2 ± 2.3 ng/μl versus 1.5 ± 2.1 ng/μl, p = 0.01, respectively). Finally, FF cfDNA level was an independent and significant predictive factor for pregnancy outcome (adjusted odds ratio = 0.69 [0.5; 0.96], p = 0.03). In multivariate analysis, the Receiving Operator Curve (ROC) analysis showed that the performance of FF cfDNA in predicting clinical pregnancy reached 0.73 [0.66–0.87] with 88% specificity and 60% sensitivity. CfDNA might constitute a promising biomarker of follicular micro-environment quality which could be used to predict IVF prognosis and to enhance female infertility management.

Correlation of cumulus gene expression of GJA1, PRSS35, PTX3, and SERPINE2 with oocyte maturation, fertilization, and embryo development

BACKGROUND

GJA1 and PTX3 were proposed as gene markers for oocyte and embryo developmental competence, while SERPINE2 was reported to be associated with pregnancy outcome. PRSS35, which is exclusively expressed in the ovary, may be correlated with oocyte competence. This study was conducted to evaluate the correlation of cumulus GJA1, PRSS35, PTX3, and SERPINE2 gene expression levels with oocyte maturation, fertilization, and early embryo development.

METHODS

In total, 308 cumulus cell samples separated from individual cumulus-oocyte complex were obtained from 40 patients undergoing the intracytoplasmic sperm injection treatment procedure. Gene expression levels (mRNA levels) in cumulus cells were assessed using quantitative real-time polymerase chain reaction.

RESULTS

Gene expression levels of GJA1 and SERPINE2 in cumulus cells surrounding mature oocytes were significantly lower than those in cumulus cells enclosing immature oocytes. PRSS35 mRNA levels in cumulus cells of fertilized oocytes were significantly higher than those in cumulus cells of unfertilized oocytes. GJA1 and SERPINE2 seemed to express higher mRNA levels, while PRSS35 showed lower expression in cumulus cells of oocytes that developed into embryos with good morphology; however, the expression levels of all three genes and PTX3 showed no significant differences between embryos with good or poor morphology.

CONCLUSIONS

GJA1 and SERPINE2 represent potential gene markers associated with oocyte maturation. PRSS35 may be correlated with oocyte fertilization potential. However, GJA1, PRSS35, PTX3, and SERPINE2 may not be considered as marker genes for predicting embryo morphology.

Assessing embryo quality by combining non-invasive markers: early time-lapse parameters reflect gene expression in associated cumulus cells

STUDY QUESTION

Are there associations between early time-lapse parameters, expression of candidate embryo viability genes in cumulus cells and embryo quality on Day 5?

SUMMARY ANSWER

Early time-lapse parameters correlate to the expression levels of candidate embryo viability genes in cumulus cells but a combined analysis including both time-lapse and candidate gene expression did not identify significant predictors of embryo quality on Day 5.

WHAT IS KNOWN ALREADY

Recent evidence suggests that early time-lapse parameters are predictive of blastocyst development. Similarly, a number of candidate genes in cumulus cells have been identified as potential markers of embryo viability. Relationships between time-lapse parameters and candidate gene expression in cumulus cells have not been investigated, and a combined analysis of these markers has not been attempted in relation to embryo quality.

STUDY DESIGN, SIZE, DURATION

A total of 78 embryos obtained by ICSI from 22 patients were studied by time-lapse and measurement of cumulus cell gene expression of known markers of embryo viability. Time-lapse and cumulus cell gene expression data were assessed in relation to embryo quality on Day 5.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All women, aged 32-40 years, underwent ICSI treatment for male infertility. Embryos with annotatable time to pronuclear breakdown (tPNB), division to two cells (t2C), three cells (t3C), four cells (t4C) and five cells (t5C) were included in the study. Expression levels of 27 candidate genes for embryo viability were measured in 78 associated cumulus cell masses using quantitative real-time PCR.

MAIN RESULTS AND THE ROLE OF CHANCE

Cumulus cell expression of 11 candidate genes involved in energy metabolism (ATPase, H+ transporting, lysosomal 70 kDa, V1 subunit A (ATP6V1A), NADH dehydrogenase (ubiquinone) 1 alpha subcomplex, 1, 7.5 kDa (NDUFA1), lactate dehydrogenase A (LDHA), phosphofructokinase platelet (PFKP) and solute carrier family 2 member 4 (SLC2A4), mitochondrial biogenesis (DNA directed RNA polymerase, mitochondrial (POLRMT) and transcription factor A, mitochondrial (TFAM), signalling (prostaglandin-endoperoxide synthase 2), steroidogenesis (cytochrome P450, family 11, subfamily A, polypeptide 1 (CYP11A1) and cell stress (heat shock 70 kDa protein 5 (HSPA5) and peroxiredoxin 3 (PRDX3)) correlated to time-lapse parameters of the developing embryo, largely for t3C onwards (all P < 0.05). Expression of ATP synthase, H+ transporting, mitochondrial Fo complex, subunit E (ATP51), HSPA5, PFKP, PRDX3 and versican (VCAN) and the parameter t4C were also related to embryo quality on Day 5 (all P < 0.05). Ordinal logistic regression, where gene expression and time-lapse parameters were combined, did not identify any significant predictors of embryo quality on Day 5.

LIMITATIONS AND REASON FOR CAUTION

Data are from a preliminary study, limited by a small sample size and using more than one ovarian stimulation protocol. A possible limitation is that each follicle was treated as an independent observation, although a considerable fraction of embryos were from the same patient.

WIDER IMPLICATIONS OF THE FINDINGS

Results presented in this study suggest that some of the variation of time-lapse parameters may be related to cumulus cell gene expression and thus the ovarian microenvironment in which the oocyte developed. Although the current study did not identify significant predictors of embryo quality on Day 5, investigation in a larger cohort may determine whether cumulus cell gene expression and time-lapse parameters can be combined to predict embryo quality.

STUDY FUNDING/COMPETING INTERESTS

Funding was provided by Fertility Associates Ltd, the Auckland Medical Research Foundation and the University of Auckland. J.C.P. has a 0.5% shareholding in Fertility Associates. All other authors of this manuscript have nothing to declare and no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Maternal age and ovarian stimulation independently affect oocyte mtDNA copy number and cumulus cell gene expression in bovine clones

STUDY QUESTION

Does maternal ageing and ovarian stimulation alter mitochondrial DNA (mtDNA) copy number and gene expression of oocytes and cumulus cells from a novel bovine model for human IVF?

SUMMARY ANSWER

Oocytes collected from females with identical nuclear genetics show decreased mtDNA copy number and increased expression of an endoplasmic reticulum (ER) stress gene with repect to ovarian stimulation, whilst differences in the expression of genes involved in mitochondrial function, antioxidant protection and apoptosis were evident in relation to maternal ageing and the degree of ovarian stimulation in cumulus cells.

WHAT IS KNOWN ALREADY

Oocyte quality declines with advancing maternal age; however, the underlying mechanism, as well as the effects of ovarian stimulation are poorly understood. Human studies investigating these effects are often limited by differences in age and ovarian stimulation regimens within a patient cohort, as well as genetic and environmental variability.

STUDY DESIGN, SIZE, DURATION

A novel bovine cross-sectional maternal age model for human IVF was undertaken. Follicles were aspirated from young (3 years of age; n = 7 females) and old (10 years of age; n = 5 females) Holstein Freisian clones following multiple unstimulated, mild and standard ovarian stimulation cycles. These bovine cloned females were generated by the process of somatic cell nuclear transfer (SCNT) from the same founder and represent a homogeneous population with reduced genetic and environmental variability. Maternal age and ovarian stimulation effects were investigated in relation to mtDNA copy number, and the expression of 19 genes involved in mitochondrial function, antioxidant protection, oocyte-cumulus cell signalling and follicle development in both oocytes and cumulus cells.

MATERIALS, SETTING, METHODS

Young (3 years of age; n = 7 females) and old (10 years of age; n = 5 females) Holstein Freisian bovine clones were maintained as one herd. Stimulation cycles were based on the long GnRH agonist down-regulation regimen used in human fertility clinics. Follicle growth rates, numbers and diameters were monitored by ultrasonography and aspirated when the lead follicles were >14 mm in diameter. Follicle characteristics were analysed using a mixed model procedure. Quantitative PCR (qPCR) was used to determine mtDNA copy number and reverse transcriptase-qPCR (RT-qPCR) was used to measure gene expression in oocytes and cumulus cells.

MAIN RESULTS AND THE ROLE OF CHANCE

Method of ovarian stimulation (P = 0.04), but not maternal age (P > 0.1), was associated with a lower mtDNA copy number in oocytes. Neither factor affected mtDNA copy number in cumulus cells. In oocytes, maternal age had no effect on gene expression; however, ovarian stimulation in older females increased the expression of GRP78 (P = 0.02), a gene involved in ER stress. In cumulus cells, increasing maternal age was associated with the higher expression of genes involved in mitochondrial maintenance (TXN2 P = 0.008 and TFAM P = 0.03), whereas ovarian stimulation decreased the expression of genes involved in mitochondrial oxidative stress and apoptosis (TXN2 P = 0.002, PRDX3 P = 0.03 and BAX P = 0.03).

LIMITATIONS, REASON FOR CAUTION

The low number of oocyte and cumulus cell samples collected from the unstimulated cycles limited the analysis. Fertilization and developmental potential of the oocytes was not assessed because these were used for mtDNA and gene expression quantification.

WIDER IMPLICATIONS OF THE FINDINGS

Delineation of the independent effects of maternal age and ovarian stimulation regimen on mtDNA copy number gene expression in oocytes and cumulus cells was enabled by the removal of genetic and environmental variability in this bovine model for human IVF. Therefore, these extend upon previous knowledge and findings provide relevant insights that are applicable for improving human ovarian stimulation regimens.

STUDY FUNDING/COMPETING INTERESTS

Funding was provided by Fertility Associates and the University of Auckland. J.C.P. is a shareholder of Fertility Associates and M.P.G. received a fellowship from Fertility Associates. The other authors of this manuscript declare no conflict of interest that could be perceived as prejudicing the impartiality of the reported research.

No specific gene expression signature in human granulosa and cumulus cells for prediction of oocyte fertilisation and embryo implantation

In human IVF procedures objective and reliable biomarkers of oocyte and embryo quality are needed in order to increase the use of single embryo transfer (SET) and thus prevent multiple pregnancies. During folliculogenesis there is an intense bi-directional communication between oocyte and follicular cells. For this reason gene expression profile of follicular cells could be an important indicator and biomarker of oocyte and embryo quality. The objective of this study was to identify gene expression signature(s) in human granulosa (GC) and cumulus (CC) cells predictive of successful embryo implantation and oocyte fertilization. Forty-one patients were included in the study and individual GC and CC samples were collected; oocytes were cultivated separately, allowing a correlation with IVF outcome and elective SET was performed. Gene expression analysis was performed using microarrays, followed by a quantitative real-time PCR validation. After statistical analysis of microarray data, there were no significantly differentially expressed genes (FDR<0,05) between non-fertilized and fertilized oocytes and non-implanted and implanted embryos in either of the cell type. Furthermore, the results of quantitative real-time PCR were in consent with microarray data as there were no significant differences in gene expression of genes selected for validation. In conclusion, we did not find biomarkers for prediction of oocyte fertilization and embryo implantation in IVF procedures in the present study.

Proteomic analysis of human follicular fluid from fertile women

Background

Follicular fluid is a unique biological fluid in which the critical events of oocyte and follicular maturation and somatic cell-germ cell communication occur. Because of the intimate proximity of follicular fluid to the maturing oocyte, this fluid provides a unique window into the processes occurring during follicular maturation. A thorough identification of the specific components within follicular fluid may provide a better understanding of intrafollicular signaling, as well as reveal potential biomarkers of oocyte health for women undergoing assisted reproductive treatment. In this study, we used high and low pH HPLC peptide separations followed by mass spectrometry to perform a comprehensive proteomic analysis of human follicular fluid from healthy ovum donors. Next, using samples from a second set of patients, an isobaric mass tagging strategy for quantitative analysis was used to identify proteins with altered abundances after hCG treatment.

Results

A total of 742 follicular fluid proteins were identified in healthy ovum donors, including 413 that have not been previously reported. The proteins belong to diverse functional groups including insulin growth factor and insulin growth factor binding protein families, growth factor and related proteins, receptor signaling, defense/immunity, anti-apoptotic proteins, matrix metalloprotease related proteins, and complement activity. In a quantitative analysis, follicular fluid samples from age-matched women undergoing in vitro fertilization oocyte retrieval were compared and 17 follicular fluid proteins were found at significantly altered levels (p < 0.05) between pre-hCG and post-hCG samples. These proteins belong to a variety of functional processes, including protease inhibition, inflammation, and cell adhesion.

Conclusions

This database of FF proteins significantly extends the known protein components present during the peri-ovulatory period and provides a useful basis for future studies comparing follicular fluid proteomes in various fertility, disease, and environmental exposure conditions. We identified 17 differentially expressed proteins after hCG treatment and together these data showed the feasibility for defining biomarkers that illuminate how the ovarian follicle microenvironment is altered in various infertility-related conditions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12014-015-9077-6) contains supplementary material, which is available to authorized users.

Specific gene expression differences in cumulus cells as potential biomarkers of pregnancy

The development of an objective and accurate test that could help select embryos with the highest chance of achieving pregnancy in IVF procedures is an important goal of reproductive medicine. For this purpose, cumulus cell gene expression is being studied to find biomarkers of pregnancy. Several recent studies have proposed potential biomarkers of pregnancy expressed in cumulus cells; however, these have mostly not been validated on an independent set of samples. The aim of this study was to analyse the expression of EFNB2, RGS2 and VCAN genes proposed as biomarkers of pregnancy in cumulus cells by quantitative polymerase chain reaction. Gene expression was evaluated in 43 individual cumulus cell samples, derived from a highly homogenous group of 43 women. The same protocol for ovarian stimulation was used for all women, and elective single embryo transfer was performed. Expression levels of RGS2 and VCAN did not differ between cumulus cells of implanted and non-implanted embryos. EFNB2 showed borderline higher expression in cumulus cells of non-implanted embryos, which is contradictory to previous studies. Altogether, the results of previous studies in which EFNB2, RGS2 and VCAN were proposed as biomarkers of pregnancy could not be replicated in our set of cumulus cell samples.

The transcriptome of corona radiata cells from individual MІІ oocytes that after ICSI developed to embryos selected for transfer: PCOS women compared to healthy women

Background

Corona radiata cells (CRCs) refer to the fraction of cumulus cells just adjacent to the oocyte. The CRCs are closely connected to the oocyte throughout maturation and their gene expression profiles might reflect oocyte quality. Polycystic ovary syndrome (PCOS) is a common cause of infertility. It is controversial whether PCOS associate with diminished oocyte quality. The purpose of this study was to compare individual human CRC samples between PCOS patients and controls.

Methods

All patients were stimulated by the long gonadotropin-releasing hormone (GnRH) agonist protocol. The CRC samples originated from individual oocytes developing into embryos selected for transfer. CRCs were isolated in a two-step denudation procedure, separating outer cumulus cells from the inner CRCs. Extracted RNA was amplified and transcriptome profiling was performed with Human Agilent® arrays.

Results

The transcriptomes of CRCs showed no individual genes with significant differential expression between PCOS and controls, but gene set enrichment analysis identified several cell cycle- and DNA replication pathways overexpressed in PCOS CRCs (FDR < 0.05). Five of the genes contributing to the up-regulated cell cycle pathways in the PCOS CRCs were selected for qRT-PCR validation in ten PCOS and ten control CRC samples. qRT-PCR confirmed significant up-regulation in PCOS CRCs of cell cycle progression genes HIST1H4C (FC = 2.7), UBE2C (FC = 2.6) and cell cycle related transcription factor E2F4 (FC = 2.5).

Conclusion

The overexpression of cell cycle-related genes and cell cycle pathways in PCOS CRCs could indicate a disturbed or delayed final maturation and differentiation of the CRCs in response to the human chorionic gonadotropin (hCG) surge. However, this had no effect on the in vitro development of the corresponding embryos. Future studies are needed to clarify whether the up-regulated cell cycle pathways in PCOS CRCs have any clinical implications.

Electronic supplementary material

The online version of this article (doi:10.1186/s13048-014-0110-6) contains supplementary material, which is available to authorized users.

Viability of cumulus cells is associated with basal AMH levels in assisted reproduction

OBJECTIVE(S)

An interesting non-invasive approach to select embryos for transfer is analyzing the health state of somatic granulosa cells surrounding the oocyte addressing their mutual dependence. This prospective study was set up to analyse whether the DNA integrity of cumulus cells correlates with preimplantation development and basal AMH levels.

STUDY DESIGN

Therefore, 56 patients who gave written consent were enrolled. Sequential denudation of the cumulus-oocyte-complexes was performed in order to separate corona radiata from outer cumulus cells. DNA integrity of both cell types was analysed using a modified chromatin dispersion test.

RESULTS

The percentage of viable corona radiata cells per patient showed a linear correlation to blastulation (P<0.05). These innermost cells showed significantly lower rates of strand breaks (P<0.01) as compared to outer cumulus cells. Age-corrected AMH was significantly associated with the DNA integrity of outer cumulus cells (P<0.05).

CONCLUSION(S)

For the first time it could be shown that in fact clinical embryologists deal with two different entities of cumulus cells, inner and outer ones. It seems that any protective mechanism of the female gamete follows an outward gradient, so that negative effects, e.g. apoptosis, may impair outer cumulus cells first. Age-corrected AMH reflects quality of these outer cumulus cells.

KEYWORDS

AMH; Corona radiata cells; DNA fragmentation; Outer cumulus cells; SCD test.

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.

Sequential (hFSH + recFSH) vs homogenous (hFSH or recFSH alone) stimulation: clinical and biochemical (cumulus cell gene expression) aspects

FSH is a key hormone in the regulation of follicular development. Together with the EGF network, these molecules mediate oocyte maturation and competence in preparation for the action of LH. FSH isoforms regulate distinct biological pathways and have specific effects on granulosa cell function and maturation of the ovarian follicle. Their dynamic interactions occur during the follicular cycle; short-living forms are predominant in the pre-ovulatory phase, whereas long-acting molecules characterize the luteal-follicular transition. Recombinant FSH (rFSH) molecules have a reduced number of isoforms and are less acidic, with a shorter half-life. We have investigated sequential stimulation, comparing hFSH + rFSH, vs. rFSH alone and hFSH alone for the entire stimulation phase. Sequential stimulation leads to an E2 per MII oocyte ratio that is much lower than is seen during treatment with the two drugs individually. Although there is a positive tendency in favor of the sequential treatment, there was no significant difference in pregnancy rates, even taking frozen embryos into consideration. The cumulus cell transcriptome varies considerably between the treatments, although with no clear significance. When comparing pregnant vs. non-pregnant patients, in general a decrease in mRNA expression can be observed in the pregnant patients, especially in expression of folic acid receptor 1 and ovostatin 2. This indicates that material has been transferred from CC to the oocyte. However, a common observation in the literature is that variations in the transcriptome of the cumulus cells are highly dependent upon the patient genotype; the potential for applying this strategy as a basis for selecting embryos is, at the very least, questionable.

Identification of new ovulation-related genes in humans by comparing the transcriptome of granulosa cells before and after ovulation triggering in the same controlled ovarian stimulation cycle

STUDY QUESTION

Which genes and molecular mechanisms are involved in the human ovulatory cascade and final oocyte maturation?

SUMMARY ANSWER

Up-regulated genes in granulosa cells (GC) represented inflammation, angiogenesis, extracellular matrix, growth factors and genes previously associated with ovarian cancer, while down-regulated genes mainly represented cell cycle and proliferation.

WHAT IS KNOWN ALREADY

Radical changes occur in the follicle during final follicle maturation after the ovulatory trigger: these range from ensuring an optimal milieu for the oocyte in meiotic arrest to the release of a mature oocyte and remodeling into a corpus luteum. A wide range of mediators of final follicle maturation has been identified in rodents, non-human primates and cows.

STUDY DESIGN, SIZE, DURATION

Prospective cohort study including 24 women undergoing ovarian stimulation with the long gonadotrophin-releasing hormone agonist protocol during 2010-2012 at Holbæk Fertility Clinic. Nine paired samples of GC and 24 paired samples of follicular fluid (FF) were obtained before and after recombinant human chorionic gonadotrophin (rhCG) administration.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Nine paired (nine arrays before rhCG and nine arrays after rhCG) samples of GC mRNA were amplified and hybridized to Affymetrix Human Gene 1.0 ST GeneChip arrays, compared and bioinformatically analyzed. Eleven selected genes were validated by quantitative reverse transcriptase PCR. FF hormones were analyzed by enzyme-linked immunosorbent assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Eleven hundred and eighty-six genes were differentially expressed (>2-fold, P<0.0001, false discovery rate <0.0012) when comparing GC isolated before and 36 h after hCG, among those were genes known to be expressed at ovulation, i.e. ADAMTS1 and HAS2. Many new ovulation-related genes were revealed, such as CD24, ANKRD22, CLDN11 and FBXO32. FF estrogen, androstenedione and anti-Müllerian hormone decreased significantly while progesterone increased, accompanied by radical changes in the expression of steroidogenic genes (CYP17A, CYP19A, HSD11B1 and HSD11B2, StAR). Genes related to inflammation, angiogenesis, extracellular matrix formation, growth factors and cancer were up-regulated while cell cycle genes were massively down-regulated. Seventy-two genes previously described in connection with ovarian cancer were among the highly regulated genes. In silico analysis for top upstream regulators of the ovulatory trigger suggested--besides LH--TNF, IGF1, PGR, AR, EGR1 (early growth response 1), ERK1/2 (extracellular signal regulated kinase 1/2) and CDKN1A (cyclin-dependent kinase inhibitor 1A) as potential mediators of the LH/hCG response.

LIMITATIONS, REASONS FOR CAUTION

The present dataset was generated from women under hormonal stimulation. However, comparison with a macaque natural cycle whole follicle ovulation dataset revealed major overlap, supporting the idea that the ovulation-related genes found in this study are relevant in the human natural cycle.

WIDER IMPLICATIONS OF THE FINDINGS

These data will serve as a research resource for genes involved in human ovulation and final oocyte maturation. Ovulation-related genes might be good candidate biomarkers of follicle and oocyte health. Further, some of the ovulation-related genes may serve as future ovarian cancer biomarkers.

STUDY FUNDING/COMPETING INTEREST(S)

Grants from the Research Fund of Region Sjælland are gratefully acknowledged. None of the authors declared any conflict of interest.

TRIAL REGISTRATION NUMBER

Not applicable.

The transcriptome of follicular cells: biological insights and clinical implications for the treatment of infertility

BACKGROUND

Oocyte maturation is under strict regulatory control, not only from intrinsic cellular processes, but also extrinsic influences. While the oocyte is directly connected to the surrounding cumulus cells (CCs) via a network of gap junctions facilitating communication and exchange of molecules, it is also influenced by the greater follicular environment. In order to produce an oocyte capable of successfully transmitting the female genetic material and able to support the earliest stages of preimplantation development, cytoplasmic and nuclear maturation must be achieved. Granulosa and CCs play an essential role in the maturation and competence acquisition of the developing oocyte. The fact that these cells are closely associated with the oocyte, share the same microenvironment and can be easily collected during IVF procedures makes them attractive targets for basic research and the development of clinically relevant assays. Analysis of follicular cells is likely to reveal important information concerning the viability and genetic constitution of their associated oocyte, as well as increase our understanding of normal follicular processes and the impact of disorders or of medical interventions such as controlled ovarian stimulation (COS). This review summarizes results obtained during the investigation of granulosa and CCs, and considers the possibilities of using follicular cells as surrogate markers of stimulation response during IVF, oocyte/embryo competence and clinical outcome.

METHODS

In order to summarize the current knowledge obtained from the analysis of follicular cells, a thorough literature search was carried out. Relevant research articles published in English up to March 2013 were reviewed.

RESULTS

Multiple groups of genes expressed in follicular cells have been identified as possible indicators of ovulation, oocyte maturity, fertilization, chromosome status, ability to generate embryos capable of reaching the blastocyst stage of development, embryo morphology and the establishment of a pregnancy. However, there is a general lack of uniformity concerning groups of gene biomarkers among different studies.

CONCLUSIONS

Extensive investigation of genes and proteins of granulosa and CCs has provided a detailed insight into the follicular microenvironment surrounding oocytes. It was evident from the data reviewed that the gene expression of follicular cells influences and is influenced by the oocyte, affecting factors such as maturity, chromosomal constitution, viability and competence. However, a general lack of overlap among genes identified as potentially useful biomarkers suggests that the transcriptome of follicular cells could be affected by multiple intrinsic factors, having to do with the patient and possibly the aetiology of infertility, as well as extrinsic factors, such as hormonal stimulation. Further work is required in order to establish a universally applicable, non-invasive test for the determination of oocyte competence based upon follicular cell assessment.