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STUDY QUESTION Are transcriptomic profiles altered in ovarian granulosa cells (GCs) and peripheral blood mononuclear cells (PBMNCs) of women with polycystic ovary syndrome (PCOS) compared to young poor responders (YPR) and women with normal response to ovarian stimulation? SUMMARY ANSWER RNA expression profiles in ovarian GCs and PBMNCs were significantly altered in patients with PCOS compared with normoresponder controls (CONT) and YPR. WHAT IS KNOWN ALREADY PCOS is characterised by a higher number of follicles at all developmental stages. During controlled ovarian hyperstimulation, PCOS women develop a larger number of follicles as a result of an exacerbated response, with an increased risk of ovarian hyperstimulation syndrome. Despite the number of developing follicles, they are often heterogeneous in both size and maturation stage, with compromised quality and retrieval of immature oocytes. Women with PCOS appear to have a longer reproductive lifespan, with a slightly higher menopausal age than the general population, in addition to having a higher antral follicular count. As a result, the ovarian follicular dynamics appear to differ significantly from those observed in women with poor ovarian response (POR) or diminished ovarian reserve. STUDY DESIGN, SIZE, DURATION Transcriptomic profiling with RNA-sequencing and validation using quantitative reverse transcription PCR (qRT-PCR). Women with PCOS (N = 20), YPR (N = 20) and CONT (N = 20). Five patients for each group were used for sequencing and 15 samples per group were used for validation. PARTICIPANTS/MATERIALS, SETTING, METHODS PCOS was defined using the revised Rotterdam diagnostic criteria for PCOS. The YPR group included women 14 mature follicles (at least 15 mm on transvaginal ultrasound). According to internal data, a threshold of >14 mature follicles was established to represent the top 25% of patients in this age group in this clinic. Overall, n = 60 GCs and PBMNCs samples were collected and processed for total RNA extraction. To define the transcriptomic cargo of GCs and PBMNCs, RNA-seq libraries were successfully prepared from samples and analysed by RNA-seq analysis. Differential gene expression analysis was used to compare RNA-seq results between different groups of samples. Ingenuity pathway analysis was used to perform Gene Ontology and pathways analyses. MAIN RESULTS AND THE ROLE OF CHANCE In PBMNCs of PCOS, there were 65 differentially expressed genes (DEGs) compared to CONT, and 16 compared to YPR. In GCs of PCOS, 4 genes showed decreased expression compared to CONT, while 58 genes were differentially expressed compared to YPR. qRT-PCR analysis confirmed the findings of the RNA-seq. The functional enrichment analysis performed revealed that DEGs in GCs of PCOS compared to CONT and YPR were prevalently involved in protein ubiquitination, oxidative phosphorylation, mitochondrial dysfunction and sirtuin signaling pathways. LARGE SCALE DATA The data used in this study is partially available at Gene Ontology database. LIMITATIONS, REASONS FOR CAUTION The analysis in PBMNCs could be uninformative due to inter-individual variability among patients in the same study groups. Despite the fact that we considered this was the best approach for our study's novel, exploratory nature. WIDER IMPLICATIONS OF THE FINDINGS RNA expression profiles in ovarian GCs and PBMNCs were altered in patients with PCOS compared with CONT and YPR. GCs of PCOS patients showed altered expression of several genes involved in oxidative phosphorylation, mitochondrial function and sirtuin signaling pathways. This is the first study to show that the transcriptomic landscape in GCs is altered in PCOS compared to CONT and YPR. STUDY FUNDING/COMPETING INTEREST(S) This study was partially supported by grant PI18/00322 from Instituto de Salud Carlos III, and European Regional Development Fund (FEDER), ‘A way to make Europe’ awarded to S.H. M.C., S.H., S.T., L.R., M.R., I.R., A.P. and R.C. declare no conflict of interests concerning this research. E.S. is a consultant for and receives research funding from the Foundation for Embryonic Competence. TRIAL REGISTRATION NUMBER N/A.

STUDY QUESTION Do embryos with different developmental competence exhibit different DNA methylation profiles at the blastocyst stage? SUMMARY ANSWER We established genome-wide DNA methylome analysis for embryo trophectoderm (TE) biopsy samples and our findings demonstrated correlation of methylation profile of trophectoderm with euploidy status and with maternal age, indicating that genome-wide methylation level might be negatively correlated with embryo quality. WHAT IS KNOWN ALREADY DNA methylation is a fundamental epigenetic regulatory mechanism that affects differentiation of cells into their future lineages during pre-implantation embryo development. Currently there is no established approach available to assess the epigenetic status of the human preimplantation embryo during routine IVF treatment. STUDY DESIGN, SIZE, DURATION In total, we collected trophectoderm biopsy samples from 30 randomly selected human blastocysts and conducted whole-genome bisulfite sequencing (WGBS) to evaluate their DNA methylation profile. Nested linear models were used to assess association between DNA methylation level and ploidy status (aneuploidy [n = 20] vs. euploidy [n = 10]), maternal age (29.4–42.5 years old), and time of blastulation (day 5 [n = 16] vs. day 6 [n = 14]), using embryo identity as a covariate. PARTICIPANTS/MATERIALS, SETTING, METHODS TE biopsy samples were obtained and submitted to bisulfite conversion. For WGBS, whole-genome sequencing libraries were then generated from the converted genome. An average of 75 million reads were obtained for each sample, and about 63% of the reads aligned to human reference. An average of 40 million reads used for the final analysis after the unconverted reads were filtered out. MAIN RESULTS AND THE ROLE OF CHANCE We revealed an increase of genome-wide DNA methylation level in aneuploid embryo TE biopsies compared to euploid embryos (25.4% ± 3.2% vs. 24.7% ± 3.2%, P LIMITATIONS, REASONS FOR CAUTION Though our results demonstrated a negative correlation of genome-wide methylation level and embryo quality, further WGBS analysis on a greater number of embryos and specific investigation of its correlation with implantation and live birth are needed before any practical use of this approach for evaluation of embryo competence. WIDER IMPLICATIONS OF THE FINDINGS This study revealed a change in genome-wide DNA methylation profile among embryos with different developmental potentials, reinforcing the critical role of DNA methylation in early development STUDY FUNDING/COMPETING INTEREST(S) No external funding was received for this study. Intramural funding was provided by the Foundation for Embryonic Competence (FEC). E.S. is a consultant for and receives research funding from the Foundation for Embryonic Competence; he is also co-founder and a shareholder of ACIS LLC and coholds patent US2019/055906 issued for utilizing electrical resistance measurement for assessing cell viability and cell membrane piercing. TRIAL REGISTRATION NUMBER N/A

STUDY QUESTION Is poor ovarian response associated with a change in predicted age based on a DNA methylation-derived age prediction model (the Horvath algorithm) in white blood cells (WBCs) or cumulus cells (CCs)? SUMMARY ANSWER In young women, poor ovarian response is associated with epigenetic age acceleration within WBC samples but is not associated with age-related changes in CC. WHAT IS KNOWN ALREADY The majority of human tissues follow predictable patterns of methylation which can be assessed throughout a person’s lifetime. DNA methylation patterns may serve as informative biomarkers of aging within various tissues. Horvath’s ‘epigenetic clock’, which is a DNA methylation-derived age prediction model, accurately predicts a subject’s true chronologic age when applied to WBC but not to CC. STUDY DESIGN, SIZE, DURATION A prospective cohort study was carried out involving 175 women undergoing ovarian stimulation between February 2017 and December 2018. Women were grouped according to a poor (≤5 oocytes retrieved) or good (>5 oocytes) response to ovarian stimulation. Those with polycystic ovary syndrome (PCOS) (n = 35) were placed in the good responder group. PARTICIPANTS/MATERIALS, SETTING, METHODS DNA methylation patterns from WBC and CC were assessed for infertile patients undergoing ovarian stimulation at a university-affiliated private practice. DNA was isolated from peripheral blood samples and CC. Bisulfite conversion was then performed and a DNA methylation array was utilized to measure DNA methylation levels throughout the genome. Likelihood ratio tests were utilized to assess the relationship between predicted age, chronologic age and ovarian response. MAIN RESULTS AND THE ROLE OF CHANCE The Horvath-predicted age for WBC samples was consistent with patients’ chronologic age. However, predicted age from analysis of CC was younger than chronologic age. In subgroup analysis of women less than 38 years of age, poor ovarian response was associated with an accelerated predicted age in WBC (P = 0.017). Poor ovarian response did not affect the Horvath-predicted age based on CC samples (P = 0.502). No alternative methylation-based calculation was identified to be predictive of age for CC. LIMITATIONS, REASONS FOR CAUTION To date, analyses of CC have failed to identify epigenetic changes that are predictive of the aging process within the ovary. Despite the poor predictive nature of both the Horvath model and the novel methylation-based age prediction model described here, it is possible that our efforts failed to identify appropriate sites which would result in a successful age-prediction model derived from the CC epigenome. Additionally, lower DNA input for CC samples compared to WBC samples was a methodological limitation. We acknowledge that a universally accepted definition of poor ovarian response is lacking. Furthermore, women with PCOS were included and therefore the group of good responders in the current study may not represent a population with entirely normal methylation profiles. WIDER IMPLICATIONS OF THE FINDINGS The process of ovarian and CC aging continues to be poorly understood. Women who demonstrate poor ovarian response to stimulation represent a common clinical challenge, so clarifying the exact biological changes that occur within the ovary over time is a worthwhile endeavor. The data from CC support a view that hormonally responsive tissues may possess distinct epigenetic aging patterns when compared with other tissue types. Future studies may be able to determine whether alternative DNA methylation sites can accurately predict chronologic age or ovarian response to stimulation from CC samples. Going forward, associations between epigenetic age acceleration and reproductive and general health consequences must also be clearly defined. STUDY FUNDING/COMPETING INTEREST(S) No external funding was obtained for the study and there are no conflicts of interest. TRIAL REGISTRATION NUMBER N/A.

Early embryonic development is characterized by drastic changes in chromatin structure that affects the accessibility of the chromatin. In human, the chromosome reorganization and its involvement in the first linage segregation are poorly characterized due to the difficulties in obtaining human embryonic material and limitation on low input technologies. In this study, we aimed to explore the chromatin remodeling pattern in human preimplantation embryos and gain insight into the epigenetic regulation of inner cell mass (ICM) and trophectoderm (TE) differentiation. We optimized ATAC-seq (an assay for transposase-accessible chromatin using sequencing) to analyze the chromatin accessibility landscape for low DNA input. Sixteen preimplantation human blastocysts frozen on Day 6 were used. Our data showed that ATAC peak distributions of the promoter regions (

Study question Is leukocyte telomere length (LTL) correlated with cumulus cells telomere length (CCTL) in an age-heterogeneous women population? Summary answer LTL showed a positive correlation with CCTL in the studied population. Hence, its potential value as indicator of ovarian age would deserve further evaluation. What is known already Progressive telomere shortening has been related to ovarian aging and genomic instability during early development. A positive correlation between short telomere length of the first polar body and aneuploidy rate has been reported. CCTL has shown to be a biomarker of oocyte and embryo quality, but its assessment is impractical. LTL has been proposed as a surrogate of TL of follicular cells, but telomere lengthening through folliculogenesis could be controlled by different mechanisms. Thus, we aimed to determine if LTL in an age-heterogeneous population is correlated with CCTL and therefore considered an accurate surrogate for telomere length in the ovary. Study design, size, duration In this prospective non-interventional cohort study, 35 egg donors and 17 women undergoing Preimplantation Genetic Testing for Aneuploidy (PGT-A) treatment were included during sixteen months. Following controlled ovarian stimulation determined by treating physicians, oocyte retrieval was performed 36 hours after final maturation induction. Cumulus cells (CC) for telomere length (TL) measurement were obtained after the pick-up and oocyte stripping. A blood sample was collected through peripheral venous access for LTL measurement. Participants/materials, setting, methods Genomic DNA of CC and leukocytes from the 52 subjects was isolated. Average delta cycle threshold (ΔCt) was determined using a SYBR green quantitative real-time PCR protocol for relative TL. For normalization of measurements, a Taqman assay for the multicopy gene Alu was performed. ΔCtL and ΔCtCC were compared by a paired t-test analysis and the fold change was calculated. Additionally, the association between them and patient age was analyzed by a Pearson correlation test. Main results and the role of chance Mean participant’s age was 29.94 ± 7.55 years and mean values for ΔCtL and ΔCtCC were 7.99 ± 0.53 and 7.46 ± 0.75, respectively. A positive significant correlation was found between age and ΔCt (ΔCtL: R2=0.71, p-value=5.18e–09; ΔCtCC: R2=0.47, p-value=0.00049). Since ΔCt values are inversely proportional to the amount of nucleic acids amplified and, therefore, to the telomere length, this correlation means that TL in both cell types decreases as women age. Additionally, ΔCtL was significantly higher than ΔCtCC (ΔCt fold change: 0.93, p-value=9e–07), meaning that CC showed significantly longer telomeres than leukocytes, thus supporting our previous published results in young egg donors. When analyzing the ΔCtL and ΔCtCC in these age-heterogeneous sample, a positive moderate and significant correlation was observed (R2=0.42, p-value=0.002). Thus, LTL could be suggested as a potential indicator of CCTL and therefore as a candidate for a biological marker of ovarian aging. Limitations, reasons for caution The sample size of this study was moderate and perhaps increasing the number of subjects might give additional strength to our findings. In addition, although relative telomere length allowed for adequate comparison between subjects, this method did not allow for absolute TL measurement. Wider implications of the findings: While reproductive implications of LTL measurement need to be further studied, our results support the potential usefulness of LTL measurement as an indicator of CCTL and ovarian aging when analyzing an age-heterogeneous population. Further, our findings suggest that CC could possess different mechanisms to cope against telomere length shortening. Trial registration number Not applicable

Transcription ceases upon stimulation of oocyte maturation and gene expression during oocyte maturation, fertilization, and early cleavage relies on translational activation of maternally derived mRNAs. Two key mechanisms that mediate translation of mRNAs in oocytes have been described in detail: cytoplasmic polyadenylation-dependent and -independent. Both of these mechanisms utilize specific protein complexes that interact with cis-acting sequences located on 3′-untranslated region (3′-UTR), and both involve embryonic poly(A) binding protein (EPAB), the predominant poly(A) binding protein during early development. While mechanistic details of these pathways have primarily been elucidated using the Xenopus model, their roles are conserved in mammals and targeted disruption of key regulators in mouse results in female infertility. Here, we provide a detailed account of the molecular mechanisms involved in translational activation during oocyte and early embryo development, and the role of EPAB in this process.

STUDY QUESTION Do infertile women aged

Embryonic poly(A)-binding protein (EPAB)-deficient mice are infertile due to defects in both the oocyte and the somatic cells of the ovary. Since EPAB is oocyte specific, the abnormalities in the somatic compartment of Epab−/− mice are likely due to factors inherent to the oocyte. Herein, we investigated whether oocyte–somatic communication is disrupted as a result of EPAB deficiency. We found that gap junctions are disrupted at the late preantral stage of folliculogenesis in Epab−/– mice and remain disrupted in cumulus-enclosed oocytes (COCs) from antral follicles. Consistent with the timing of gap junction dysfunction, F-actin staining of transzonal processes (TZPs) is lower in Epab−/− follicles at the late preantral stage and completely absent in Epab−/− COCs. Epab−/− oocytes express significantly lower levels of the junction protein E-cadherin, which is likely to be a contributing factor leading to premature TZP retraction. Overall, these results demonstrate that EPAB is important for oocyte–somatic communication by maintaining TZPs and gap junctions at the preantral stage of folliculogenesis.

Oocyte maturation is associated with suppression of transcriptional activity. Consequently, gene expression during oocyte maturation, fertilization and early embryo development, until zygotic genome activation (ZGA) is primarily regulated by translational activation of maternally derived mRNAs. Embryonic poly(A)-binding protein (EPAB) is the predominant poly(A)-binding protein in Xenopus, mouse and human oocytes and early embryos prior to ZGA. EPAB plays a key role in polyadenylation-dependent translational activation of mRNAs by stabilizing polyadenylated mRNAs and by stimulating their translation. Epab-knockout female mice are sterile, fail to generate mature oocytes and display impaired cumulus expansion and ovulation. Consistent with its role during gametogenesis and early embryo development, Xenopus and mouse Epab mRNA is expressed exclusively in oocytes and early embryos, and is undetectable following ZGA or in somatic tissues. Herein, we demonstrate that although EPAB is expressed in human somatic tissues, its transcripts largely consist of an alternatively spliced form lacking the first 58 bp of exon 8, which leads to the formation of a premature stop codon 6 amino acids downstream on exon 8, and omission of the functionally critical poly(A)-binding domain. Moreover, 8-cell and blastocyst stage human embryos also express only the alternatively spliced form of EPAB. On the other hand, the full-length form of EPAB mRNA is exclusively expressed in oocytes. In conclusion, in contrast with the transcriptional regulation in Xenopus and mouse, oocyte- and early embryo-specific expression of EPAB in human is regulated by a post-transcriptional mechanism.

Transcriptional silencing that begins with oocyte maturation persists during the initial mitotic divisions of the embryo. Gene expression during this period largely depends on the translational activation of maternal mRNAs by cytoplasmic polyadenylation and requires an embryonic poly(A) binding protein (EPAB). EPAB has been identified in Xenopus and mouse, where it is expressed exclusively in oocytes and early embryos until zygotic genome activation (ZGA) when it is replaced by the somatic cytoplasmic poly(A) binding protein (PABPC1). EPAB plays a central role in the regulation of maternal mRNA activation by preventing deadenylation and promoting translation. In this study, we identified and characterized the human EPAB ortholog. Human EPAB is a 619 amino acid protein with 77% identity and 84% similarity to mouse EPAB. Human EPAB mRNA is detected in ovaries, testes and several somatic tissues including pancreas, liver and thymus. Similar to the observations in Xenopus and mouse, human EPAB is the predominant poly(A) binding protein in immature (germinal vesicle) and mature (metaphase II) oocytes, and it is replaced by PABPC1 following ZGA, which occurs at 4- to 8-cell stage in human. Our findings suggest that the unique translational regulatory pathways that control gene expression during oogenesis and early embryo development may be common between model organisms and humans.

Shed menstrual endometrium is viable and has the ability to implant and grow in women, who eventually develop endometriosis. Many of the cell-to-cell or cell-to-extracellular matrix (ECM) connections are mediated by integrins. Monocyte chemotactic protein (MCP)-1, a potent chemotactic factor produced in many cell types, is elevated in the peritoneal fluid of women with endometriosis. In this study, we investigated whether endometrial stromal cell (ESC) adhesion itself induces the expression of MCP-1 and whether this process is integrin mediated. ESC were plated on Petri dishes and 24-well plates coated with fibronectin, laminin, collagen IV, poly-L-lysine, or mouse anti-human integrin beta(1) and beta(2) monoclonal antibodies. Adherence of ESC to various ECM substrates, except for poly-L-lysine, a non-integrin-dependent adhesion matrix, induced the expression of MCP-1 at both mRNA and protein levels. Engagement of beta(1)-containing integrins was associated with ESC adhesion and resulted in up-regulation of MCP-1 gene expression and protein secretion. Disruption of the actin cytoskeleton by treating ESC with cytochalasin D completely blocked the increase of MCP-1 induced in response to integrin activation. These findings indicate a novel mechanism of MCP-1 regulation. Cell adhesion to ECM is an important event that leads to stimulation of MCP-1 expression, and this process is mediated by integrins.

There is a cyclicity in the number of endometrial macrophages that is most likely secondary to changes in steroid hormone levels. One cytokine that controls macrophage migration is monocyte chemotactic protein-1 (MCP-1). In the endometrium, highest levels of MCP-1 are detected perimenstrually, when estrogen levels are low; however, when estrogen levels are high (around the time of ovulation), MCP-1 levels are lowest. We hypothesized that sex steroids may be involved in the regulation of macrophage migration by regulating MCP-1 expression. We investigated the regulation of MCP-1 expression in human endometrial stromal cells by estradiol 17β (E 2 ) and progestins. We found that MCP-1 mRNA levels decreased in response to E 2 (5 x 10 -8 M), with biphasic nadirs at 8 h and 24 h. MCP-1 protein production was also inhibited by E 2 in a concentration-dependent manner. Tamoxifen, an anti-estrogen, alone (10 -7 M) did not affect MCP-1 expression, but it reversed the E 2 -induced inhibition up to 80%. Progesterone (10 -7 M) alone slightly decreased MCP-1 levels, and the combination of E 2 and progesterone further decreased them, but that decrease was not different from that observed using E 2 treatment alone. In summary, we found that E 2 inhibits MCP-1 expression in endometrial stromal cells, and we speculate that E 2 may control endometrial macrophage migration by regulating MCP-1 expression.

Leukaemia inhibitory factor (LIF) is a 43 kDa glycoprotein with a remarkable range of biological actions in different tissue systems. LIF improves the rate of fertilization of mouse oocytes in vitro and up-regulates aromatase enzyme. We postulated that LIF may be an important modulator of ovarian function and may also improve embryo quality in humans. Follicular fluid samples from patients undergoing in-vitro fertilization (IVF) and embryo transfer (n = 123), from women undergoing ovarian stimulation (n = 4) and from women undergoing laparoscopy for tubal ligation during their follicular phase (n = 3) were used. Follicular fluid LIF, oestradiol, and progesterone were measured and embryo quality was assessed. Granulosa-lutein cells were cultured for 3 days in Ham's F-12:Dulbecco's modified Eagle's medium (DMEM). Ovarian stromal cells, isolated by enzymatic dispersion of ovarian tissue, were also cultured in the same medium. Following experimental treatments, LIF mRNA and protein concentrations were quantified. The concentration of LIF was 0.8 +/- 0.3 (mean +/- SEM) pg/ml in pre-human chorionic gonadotrophin (HCG) follicular fluid samples and 13.0 +/- 1.1 pg/ml in post-HCG follicular fluid samples (P0.05). LIF levels were undetectable in three follicular fluid samples obtained during unstimulated follicular phase. There was a correlation between follicular fluid LIF and follicular fluid oestradiol concentrations (r = 0.36; P = 0.0001) and the number of grade I embryos (r = 0.62; P = 0.01). LIF mRNA and the protein were expressed constitutively but in low amounts in the ovarian stromal cell cultures. The concentrations of LIF mRNA as well as protein were increased by interleukin (IL)-1alpha and tumour necrosis factor alpha (TNF alpha) in a time- and concentration-dependent manner. Purified granulosa-lutein cells expressed low amounts of LIF mRNA and protein which were not significantly increased by IL-1alpha or TNF alpha. Our findings suggest that HCG stimulates the expression of LIF in follicular fluid. Both granulosa-lutein and ovarian stromal cells express the LIF mRNA and produce the protein. Modulation of LIF in these cells may play an important role in the physiology of ovulation and early embryo development.