Human oocyte maturation in vitro is improved by co-culture with cumulus cells from mature oocytes

Upregulated let-7 expression in the follicular fluid of patients with endometriomas leads to dysfunction of granulosa cells through targeting of IGF1R

STUDY QUESTION

What molecular mechanisms underlie the decline in ovarian reserve as the number and quality of oocytes decrease in patients with ovarian endometriomas (OEM)?

SUMMARY ANSWER

Elevated expression of the let-7 micro(mi)RNAs in the follicular microenvironment of OEM-affected ovaries targets the expression of type 1 insulin-like growth factor receptor (IGF1R) in granulosa cell (GC) and disrupts their proliferation, steroid hormone secretion levels, adenosine triphosphate (ATP) energy metabolism, and reactive oxygen species (ROS) oxidative stress levels.

WHAT IS KNOWN ALREADY

Patients with OEM exhibit diminished ovarian reserve, characterized by reduced oocyte quantity and quality. Fibrotic changes in the ovarian tissue surrounding the OEM create a disruptive microenvironment for follicular growth and development.

STUDY DESIGN, SIZE, DURATION

This is a cross-sectional study aimed to elucidate the molecular mechanisms underlying the impact of OEM on follicular development. Initially, miRNA expression profiles in follicular fluid (FF) samples were sequenced from patients with infertility related to OEM (N = 3) and male factor (MF) infertility (N = 3), with the latter serving as the control group. Differentially expressed miRNAs were validated in additional samples from each group (N = 55 in OEM group and N = 45 in MF group) to confirm candidate miRNAs. The study also investigated indicators associated with GCs dysfunction in vitro on rat GCs. Subsequently, rat models of OEM were established through endometrial allogeneic transplantation, and fertility experiments were conducted to assess the let-7/IGF1R axis response to OEM in vivo. Patient samples were collected between May 2018 and April 2019, and the mechanistic study was conducted over the subsequent three years.

PARTICIPANTS/MATERIALS, SETTING, METHODS

FF and GC samples were obtained from infertile patients undergoing IVF treatment for OEM and MF related infertility. miRNA expression profiles in FF samples were analyzed using second-generation high-throughput sequencing technology, and candidate miRNAs were validated through quantitative PCR (qPCR). In the in vitro experiments conducted with rat GCs, cell proliferation was assessed using the CCK-8 assay, while steroid hormone concentrations were measured using chemiluminescence. ATP content was determined with an ATP assay kit, and levels of ROS were quantified using flow cytometry. A dual luciferase reporter gene assay was employed to identify the target gene of let-7 based on the construction of a IGF1R reporter gene plasmid using 293T cells. Western blotting was utilized to evaluate the expression of IGF1R in GCs, as well as its downstream proteins, and changes in signaling pathways following let-7 agomir/antagomir transfection and/or Igf1r silencing. In the in vivo OEM rat models, alterations in ovarian structure and cyst morphology were observed using hematoxylin and eosin staining. The expressions of let-7 and Igf1r in GCs were evaluated through qPCR, while variations in IGF1R expression were investigated with immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

The cohort of patients with ovarian OEM in this study exhibited significantly decreased antral follicle counts, oocyte retrieval numbers, and normal fertilization rates compared to the control group with MF. The expression of the let-7 miRNA family was markedly upregulated in the FF and GCs of OEM patients. Transfection of rat GCs with let-7 agonists diminished the functions of GCs, including disrupted cell proliferation, mitochondrial oxidative phosphorylation, and steroid hormone secretion, while transfection of rat GCs with let-7 antagonists caused the opposite effects. Luciferase reporter gene experiments confirmed that let-7 complementarily bound to the 3'-untranslated regions of IGF1R. Stimulation of let-7 expression in rat GCs led to a significant decrease in IGF1R expression, while inhibition of let-7 increased IGF1R expression. The expression of IGF1R in the GCs of OEM patients was also significantly reduced compared to MF patients. Silencing of Igf1r led to the dysfunction of GCs, similar to the effects of let-7 agonization, as demonstrated by the downregulation of key proteins involved in cell proliferation (CCND2 and CCND3) and oestradiol synthesis, as well as an increase in progesterone synthesis (StAR), while implicating the PI3K-Akt and MAPK signaling pathways. The antagonistic effect of let-7 on GCs was ineffective when Igf1r was silenced. Conversely, the agonistic effect of let-7 on GCs could be reversed by stimulation with the IGF1R ligand IGF-1. These findings suggested that let-7 regulated the proliferation, differentiation, and ATP synthesis of GCs through targeting IGF1R. The OEM rat model demonstrated alterations in ovarian morphology and structure, along with reduced fertility. Let-7 expression was significantly upregulated in GCs of OEM rats compared to normal rats, while Igf1r and IGF1R expression in pre-ovulatory follicular GCs were notably downregulated, supporting the notion that elevated let-7 expression in the follicular microenvironment of OEM inhibited IGF1R, leading to abnormal GC function and impacting fertility at the molecular level.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

The synthesis and secretion mechanisms of steroid hormones are intricate and complex. Some enzymes that regulate oestrogen synthesis also play a role in progesterone synthesis. Moreover, certain receptors can respond to multiple hormone signals. Therefore, in this study, the expression patterns of key enzymes such as CYP17A, CYP11A1, HSD3B2, StAR, and receptors including AR, LHCGR, FSHR, ESR2, might be influenced by various factors and might not demonstrate complete consistency.

WIDER IMPLICATIONS OF THE FINDINGS

Future research will concentrate on investigating the potential impact of ovarian stromal cells on the external microenvironment of follicle growth. Additionally, screening for small molecule drugs that target let-7 and IGF1R actions can be conducted to intervene and modify the ovarian microenvironment, ultimately enhancing ovarian function.

STUDY FUNDING/COMPETING INTEREST(S)

This study received funding from the National Natural Science Foundation of China (grant number 82301851 to L.B.S., grant numbers U23A20403 and U20A20349 to S.Y.Z., and grant number 82371637 to Y.D.D.) and the Natural Science Foundation of Zhejiang Province (grant LTGY23H040010 to F.Z.). The authors have no conflicts of interest to declare.

Current status and hotspots of in vitro oocyte maturation: a bibliometric study of the past two decades

PURPOSE

In vitro maturation (IVM) of oocytes is a promising technique among assisted reproductive technologies. Although IVM has been used for many years, its efficiency is still relatively low compared to that of traditional in vitro fertilization (IVF) procedures. Therefore, we aimed to explore the hotspots and frontiers of IVM research over the past two decades and provide direction for IVM advancement.

METHODS

The articles and reviews related to IVM in the Web of Science Core Collection (WoSCC) were retrieved on June 03, 2024. Three bibliometric tools, VOSviewer 1.6.18 (2010), CiteSpace 6.1. R6 (2006), and Bibliometrix R package 4.1.0 (2017), were used to generate network maps and explore knowledge frontiers and trends. To uncover the latest research advancements and frontiers in the IVM field, we conducted an analysis of the entire IVM field, including all species. Given our focus on human IVM developments, we identified the leading countries, institutions, authors, and journals driving progress in human IVM.

RESULTS

A total of 5150 publications about IVM and 1534 publications in the specific context of human IVM were retrieved from the WoSCC. The number of publications on both overall IVM and human IVM fields has increased steadily. In human IVM, the United States (USA) and McGill University were the most prolific country and institution, respectively. Human Reproduction was both the most published in and the most cited journal in human IVM. Seang Lin, Tan was the most productive author, and Ri-Cheng, Chian's papers were the most cited in human IVM. Furthermore, five hotspot topics were summarized, namely, culture system, supplementation, cooperation in the ovarian follicle, gene expression, and oocyte cryopreservation.

CONCLUSIONS

Further studies could concentrate on the following topics: (1) the mechanisms involved in oocyte maturation in vivo and in vitro, especially in energy metabolism and intercellular communications; (2) the establishment of IVM culture systems, including standardization of the biphasic IVM culture system and supplementation; (3) the genetic differences between oocytes matured in vivo and in vitro; and (4) the mechanism of cryopreservation-inflicted damage and solutions to this challenge. For human IVM, it is necessary to precisely assess the developmental stages of oocytes and adjust the IVM process accordingly to develop tailored culture media. Concurrently, clinical trials are essential for evaluating the effectiveness and safety of IVM.

The impact of low oocyte maturity ratio on blastocyst euploidy rate: a matched retrospective cohort study

OBJECTIVE

To investigate the association between a low oocyte maturity ratio from in vitro fertilization cycle and blastocyst euploidy.

METHODS

A total of 563 preimplantation genetic testing (PGT) cycles (PGT cycles with chromosomal structural rearrangements were excluded) were performed between January 2021 and November 2022 at our center (average oocyte maturity rate: 86.4% ± 14.6%). Among them, 93 PGT cycles were classified into the low oocyte maturity rate group (group A, < mean - 1 standard deviation [SD]), and 186 PGT cycles were grouped into the average oocyte maturity rate group (group B, mean ± 1 SD). Group B was 2:1 matched with group A. Embryological, blastocyst ploidy, and clinical outcomes were compared between the two groups.

RESULTS

The oocyte maturity (metaphase II [MII oocytes]), MII oocyte rate, and two pronuclei (2PN) rates were significantly lower in group A than in group B (5.2 ± 3.0 vs. 8.9 ± 5.0, P = 0.000; 61.6% vs. 93.0%, P = 0.000; 78.7% vs. 84.8%, P = 0.002, respectively). In group A, 106 of 236 blastocysts (44.9%) that underwent PGT for aneuploidy were euploid, which was not significantly different from the rate in group B (336/729, 46.1%, P = 0.753). However, euploid blastocysts were obtained only in 55 cycles in group A (55/93, 59.1%), which was lower than the rate in group B (145/186, 78.0%, P = 0.001). The clinical pregnancy rate in group B (73.9%) was higher than that in group A (58.0%) (P = 0.040).

CONCLUSION

Our results suggest that a low oocyte maturity ratio is not associated with blastocyst euploidy but is associated with fewer cycles with euploid blastocysts for transfer, lower 2PN rates, and lower clinical pregnancy rates.

New Approach to the Cryopreservation of GV Oocytes and Cumulus Cells through the Lens of Preserving the Intercellular Gap Junctions Based on the Bovine Model

Differences in structural and functional properties between oocytes and cumulus cells (CCs) may cause low vitrification efficiency for cumulus-oocyte complexes (COCs). We have suggested that the disconnection of CCs and oocytes in order to further cryopreservation in various ways will positively affect the viability after thawing, while further co-culture in vitro will contribute to the restoration of lost intercellular gap junctions. This study aimed to determine the optimal method of cryopreservation of the suspension of CCs to mature GV oocytes in vitro and to determine the level of mRNA expression of the genes (GJA1, GJA4; BCL2, BAX) and gene-specific epigenetic marks (DNMT3A) after cryopreservation and in vitro maturation (IVM) in various culture systems. We have shown that the slow freezing of CCs in microstraws preserved the largest number of viable cells with intact DNA compared with the methods of vitrification and slow freezing in microdroplets. Cryopreservation caused the upregulation of the genes Cx37 and Cx43 in the oocytes to restore gap junctions between cells. In conclusion, the presence of CCs in the co-culture system during IVM of oocytes played an important role in the regulation of the expression of the intercellular proteins Cx37 and Cx43, apoptotic changes, and oocyte methylation. Slow freezing in microstraws was considered to be an optimal method for cryopreservation of CCs.

NTRK2 Promotes Sheep Granulosa Cells Proliferation and Reproductive Hormone Secretion and Activates the PI3K/AKT Pathway

Neurotrophin receptor B (NTRK2), also named TRKB, belongs to the neurotrophic factor family. Previous studies have shown that NTRK2 is associated with high fertility in mammals. However, the molecular mechanism and regulatory pathway of this neurotrophic factor remain unclear. In this study, NTRK2 overexpression and NTRK2-siRNA were constructed to detect the effects of NTRK2 on the proliferation and hormone secretion of the ovarian granulosa cells (GCs) of sheep. We successfully isolated follicular phase granulosa cells in vitro from the ovaries of sheep in simultaneous estrus, and the immunofluorescence results confirmed that NTRK2 was expressed in the collected cells. Subsequently, the effect of NTRK2 on the proliferation of sheep granulosa cells was examined via cell transfection experiments. The results showed that the expression of CDK4 and CyclinD2 was significantly increased after NTRK2 overexpression, while the opposite trend was observed after the inhibition of NTRK2 expression (p < 0.05). The EdU and CCK-8 assays showed that the proliferation rate of sheep GCs was significantly increased after NTRK2 overexpression, while the opposite trend was observed after the inhibition of NTRK2 expression (p < 0.05). Moreover, NTRK2 significantly increased the expression of steroidogenesis-related genes, including steroidogenic acute regulatory protein (STAR) and hydroxy-δ-5-steroid dehydrogenase (HSD3B1), and cytochrome P450 family 19 subfamily A member 1 (CYP19A1). The ELISA results showed that the secretion levels of E2 and P4 significantly increased after NTRK2 overexpression, while the opposite trend was observed after the inhibition of NTRK2 expression (p < 0.05). Previous studies had confirmed that NTRK2 gene belongs to the PI3K-AKT signaling pathway and participates in the signaling of this pathway. This was demonstrated by protein-protein interaction analysis and NTRK2 belongs to the PI3K-AKT pathway. The modification of PI3K and AKT, markers of the PI3K-AKT pathway, via phosphorylation was increased after NTRK2 overexpression in the sheep GCs, while the opposite trend was observed after the inhibition of NTRK2 expression (p < 0.05). Overall, these results suggest that the NTRK2 gene regulates the proliferation of GCs and the secretion of steroid hormones in sheep, and that it influences the phosphorylation level of the PI3K/AKT signaling pathway. These findings provided a theoretical basis and new perspectives for exploring the regulation of NTRK2 gene in the development of ovine follicles.

Transcriptomic integrity of human oocytes used in ARTs: technical and intrinsic factor effects

BACKGROUND

Millions of children have been born throughout the world thanks to ARTs, the harmlessness of which has not yet been fully demonstrated. For years, efforts to evaluate the specific effects of ART have focused on the embryo; however, it is the oocyte quality that mainly dictates first and foremost the developmental potential of the future embryo. Ovarian stimulation, cryopreservation, and IVM are sometimes necessary steps to obtain a mature oocyte, but they could alter the appropriate expression of the oocyte genome. Additionally, it is likely that female infertility, environmental factors, and lifestyle have a significant influence on oocyte transcriptomic quality, which may interfere with the outcome of an ART attempt.

OBJECTIVE AND RATIONALE

The objective of this review is to identify transcriptomic changes in the human oocyte caused by interventions specific to ART but also intrinsic factors such as age, reproductive health issues, and lifestyle. We also provide recommendations for future good practices to be conducted when attempting ART.

SEARCH METHODS

An in-depth literature search was performed on PubMed to identify studies assessing the human oocyte transcriptome following ART interventions, or in the context of maternal aging, suboptimal lifestyle, or reproductive health issues.

OUTCOMES

ART success is susceptible to external factors, maternal aging, lifestyle factors (smoking, BMI), and infertility due to endometriosis or polycystic ovary syndrome. Indeed, all of these are likely to increase oxidative stress and alter mitochondrial processes in the foreground. Concerning ART techniques themselves, there is evidence that different ovarian stimulation regimens shape the oocyte transcriptome. The perturbation of processes related to the mitochondrion, oxidative phosphorylation, and metabolism is observed with IVM. Cryopreservation might dysregulate genes belonging to transcriptional regulation, ubiquitination, cell cycle, and oocyte growth pathways. For other ART laboratory factors such as temperature, oxygen tension, air pollution, and light, the evidence remains scarce. Focusing on genes involved in chromatin-based processes such as DNA methylation, heterochromatin modulation, histone modification, and chromatin remodeling complexes, but also genomic imprinting, we observed systematic dysregulation of such genes either after ART intervention or lifestyle exposure, as well as due to internal factors such as maternal aging and reproductive diseases. Alteration in the expression of such epigenetic regulators may be a common mechanism linked to adverse oocyte environments, explaining global transcriptomic modifications.

WIDER IMPLICATIONS

Many IVF factors and additional external factors have the potential to impair oocyte transcriptomic integrity, which might not be innocuous for the developing embryo. Fortunately, it is likely that such dysregulations can be minimized by adapting ART protocols or reducing adverse exposure.

Oocyte rescue in-vitro maturation does not adversely affect chromosome segregation during the first meiotic division

RESEARCH QUESTION

Does rescue in-vitro maturation (IVM) in the presence or absence of cumulus cells, affect the progress of meiosis I, compared with oocytes that mature in vivo?

DESIGN

This prospective study was conducted in a university-affiliated fertility centre. Ninety-five young oocyte donors (mean age 25.57 ± 4.47) with a normal karyotype and no known fertility problems were included. A total of 390 oocytes (116 mature metaphase II [MII] and 274 immature oocytes) were analysed. The immature oocytes underwent rescue IVM in the presence of cumulus cells (CC; IVM+CC; n = 137) or without them (IVM-CC; n = 137), and IVM rate was calculated. Chromosome copy number analysis using next-generation sequencing (NGS) was performed on all rescue IVM oocytes reaching MII as well as those that were mature at the time of initial denudation (in-vivo-matured oocytes [IVO]).

RESULTS

Maturation rates were similar in IVM+CC and IVM-CC oocytes (62.8 versus 71.5%, P = 0.16). Conclusive cytogenetic results were obtained from 65 MII oocytes from the IVM+CC group, 87 from the IVM-CC group, and 99 from the IVO group. Oocyte euploidy rates for the three groups were similar, at 75.4%, 83.9% and 80.8%, respectively (P = 0.42).

CONCLUSIONS

The results suggest that culture of germinal vesicle and metaphase I oocytes in the presence of cumulus cells does not improve rates of IVM. In general, the process of rescue IVM does not appear to alter the frequency of oocytes with a normal chromosome copy number.

Efficacy and safety of recombinant human granulocyte colony-stimulating factor in patients with poor ovarian response: protocol for a multicentre, randomised, controlled trial

INTRODUCTION

Approximately 17.5% of couples of reproductive age have experienced infertility. Women with a poor ovarian response (POR) must undergo in vitro fertilisation (IVF) and embryo transfer to achieve pregnancy. However, studies have reported a poor response to gonadotropin stimulation in women undergoing IVF-ET. Results from animal experiments suggest that granulocyte colony-stimulating factor (G-CSF) has a curative effect by protecting ovarian function, reducing follicle loss and delaying premature ovarian failure in rats caused by chemotherapy. Clinical studies on the therapeutic effect of G-CSF are deficient; therefore, this study will investigate its ability to improve ovum quality and maturity among women with POR undergoing IVF/intracytoplasmic sperm injection (ICSI).

METHODS AND ANALYSIS

This clinical, multicentre, triple-blind, placebo-controlled trial will employ balanced randomisation (1:1). The planned sample size is 312 participants (156 subjects in each group). A total of 312 patients with infertility undergoing IVF/ICSI will be recruited from four public hospitals in China. The participants will be randomly divided into an experimental group (G-CSF) and a placebo group (control). All patients will be treated by using the progestin-primed ovarian stimulation superovulation protocol. The primary outcome will be D3 embryo quality. The number of ova obtained, MII ova and transferable embryos will be inclusive in the secondary outcome.

ETHICS AND DISSEMINATION

To our knowledge, this is the first clinical trial to investigate the effect of G-CSF treatment timing and stimulation protocol in patients with POR in China. This study will provide new information about G-CSF efficacy among patients with POR undergoing IVF/ICSI and can help improve ovum quality and maturity. Clinical trials on this subject are deficient in China; therefore, a well-designed randomised trial is needed to determine the ability of G-CSF to improve ovum quality and maturity to facilitate conception among women with POR treated with IVF/ICSI.

TRIAL REGISTRATION NUMBER

ChiCTR2200062412.

Overview of Gene Expression Dynamics during Human Oogenesis/Folliculogenesis

The oocyte transcriptome follows a tightly controlled dynamic that leads the oocyte to grow and mature. This succession of distinct transcriptional states determines embryonic development prior to embryonic genome activation. However, these oocyte maternal mRNA regulatory events have yet to be decoded in humans. We reanalyzed human single-oocyte RNA-seq datasets previously published in the literature to decrypt the transcriptomic reshuffles ensuring that the oocyte is fully competent. We applied trajectory analysis (pseudotime) and a meta-analysis and uncovered the fundamental transcriptomic requirements of the oocyte at any moment of oogenesis until reaching the metaphase II stage (MII). We identified a bunch of genes showing significant variation in expression from primordial-to-antral follicle oocyte development and characterized their temporal regulation and their biological relevance. We also revealed the selective regulation of specific transcripts during the germinal vesicle-to-MII transition. Transcripts associated with energy production and mitochondrial functions were extensively downregulated, while those associated with cytoplasmic translation, histone modification, meiotic processes, and RNA processes were conserved. From the genes identified in this study, some appeared as sensitive to environmental factors such as maternal age, polycystic ovary syndrome, cryoconservation, and in vitro maturation. In the future, the atlas of transcriptomic changes described in this study will enable more precise identification of the transcripts responsible for follicular growth and oocyte maturation failures.

Three-dimensional architecture of granulosa cell derived from oocyte cumulus complex, revealed by FIB-SEM

The oocyte cumulus complex is mainly composed of an oocyte, the perivitelline space, zona pellucida and numerous granulosa cells. The cumulus granulosa cells (cGCs) provide a particularly important microenvironment for oocyte development, regulating its growth, maturation and meiosis. In this study, we studied the internal structures and cell-to-cell connections of mouse cGCs using focused ion beam scanning electron microscopy (FIB-SEM). We reconstructed three-dimensional models to display characteristic connections between the oocyte and cGCs, and to illustrate various main organelles in cGCs together with their interaction relationship. A special form of cilium identified in granulosa cell was never reported in previous literature.

FGF2, LIF, and IGF1 (FLI) supplementation during human in vitro maturation enhances markers of gamete competence

STUDY QUESTION

Does a chemically defined maturation medium supplemented with FGF2, LIF, and IGF1 (FLI) improve in vitro maturation (IVM) of cumulus-oocyte complexes (COCs) obtained from children, adolescents, and young adults undergoing ovarian tissue cryopreservation (OTC)?

SUMMARY ANSWER

Although FLI supplementation did not increase the incidence of oocyte meiotic maturation during human IVM, it significantly improved quality outcomes, including increased cumulus cell expansion and mitogen-activated protein kinase (MAPK) expression as well as enhanced transzonal projection retraction.

WHAT IS KNOWN ALREADY

During OTC, COCs, and denuded oocytes from small antral follicles are released into the processing media. Recovery and IVM of these COCs is emerging as a complementary technique to maximize the fertility preservation potential of the tissue. However, the success of IVM is low, especially in the pediatric population. Supplementation of IVM medium with FLI quadruples the efficiency of pig production through improved oocyte maturation, but whether a similar benefit occurs in humans has not been investigated.

STUDY DESIGN, SIZE, DURATION

This study enrolled 75 participants between January 2018 and December 2021 undergoing clinical fertility preservation through the Fertility & Hormone Preservation & Restoration Program at the Ann & Robert H. Lurie Children's Hospital of Chicago. Participants donated OTC media, accumulated during tissue processing, for research.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants who underwent OTC and include a pediatric population that encompassed children, adolescents, and young adults ≤22 years old. All participant COCs and denuded oocytes were recovered from media following ovarian tissue processing. IVM was then performed in either a standard medium (oocyte maturation medium) or one supplemented with FLI (FGF2; 40 ng/ml, LIF; 20 ng/ml, and IGF1; 20 ng/ml). IVM outcomes included meiotic progression, cumulus cell expansion, transzonal projection retraction, and detection of MAPK protein expression.

MAIN RESULTS AND THE ROLE OF CHANCE

The median age of participants was 6.3 years, with 65% of them classified as prepubertal by Tanner staging. Approximately 60% of participants had been exposed to chemotherapy and/or radiation prior to OTC. On average 4.7 ± 1 COCs and/or denuded oocytes per participant were recovered from the OTC media. COCs (N = 41) and denuded oocytes (N = 29) were used for IVM (42 h) in a standard or FLI-supplemented maturation medium. The incidence of meiotic maturation was similar between cohorts (COCs: 25.0% vs 28.6% metaphase II arrested eggs in Control vs FLI; denuded oocytes: 0% vs 5.3% in Control vs FLI). However, cumulus cell expansion was 1.9-fold greater in COCs matured in FLI-containing medium relative to Controls and transzonal projection retraction was more pronounced (2.45 ± 0.50 vs 1.16 ± 0.78 projections in Control vs FLIat 16 h). Additionally, MAPK expression was significantly higher in cumulus cells obtained from COCs matured in FLI medium for 16-18 h (chemiluminescence corrected area 621,678 vs 2,019,575 a.u., P = 0.03).

LIMITATIONS, REASONS FOR CAUTION

Our samples are from human participants who exhibited heterogeneity with respect to age, diagnosis, and previous treatment history. Future studies with larger sample sizes, including adult participants, are warranted to determine the mechanism by which FLI induces MAPK expression and activation. Moreover, studies that evaluate the developmental competence of eggs derived from FLI treatment, including assessment of embryos as outcome measures, will be required prior to clinical translation.

WIDER IMPLICATIONS OF THE FINDINGS

FLI supplementation may have a conserved beneficial effect on IVM for children, adolescents, and young adults spanning the agricultural setting to clinical fertility preservation.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Department of Obstetrics and Gynecology startup funds (F.E.D.), Department of Surgery Faculty Practice Plan Grant and the Fertility & Hormone Preservation & Restoration Program at the Ann & Robert H. Lurie Children's Hospital of Chicago (M.M.L. and E.E.R.). M.M.L. is a Gesualdo Foundation Research Scholar. Y.Y.'s research is supported by the internal research funds provided by Colorado Center of Reproductive Medicine. Y.Y., L.D.S., R.M.R., and R.S.P. have a patent pending for FLI. The remaining authors have no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Cumulus cell co-culture in media drops does not improve rescue in vitro maturation of vitrified-warmed immature oocytes

OBJECTIVE

To assess whether co-culture with vitrified-warmed cumulus cells (CCs) in media drops improves rescue in vitro maturation (IVM) of previously vitrified immature oocytes. Previous studies have shown improved rescue IVM of fresh immature oocytes when cocultured with CCs in a three-dimensional matrix. However, the scheduling and workload of embryologists would benefit from a simpler IVM approach, particularly in the setting of time-sensitive oncofertility oocyte cryopreservation (OC) cases. Although the yield of developmentally competent mature metaphase II (MII) oocytes is increased when rescue IVM is performed before cryopreservation, it is unknown whether maturation of previously vitrified immature oocytes is improved after coculture with CCs in a simple system not involving a three-dimensional matrix.

DESIGN

Randomized controlled trial.

SETTING

Academic hospital.

PATIENTS

A total of 320 (160 germinal vesicles [GVs] and 160 metaphase I [MI]) immature oocytes and autologous CC clumps were vitrified from patients who were undergoing planned OC or intracytoplasmic sperm injection from July 2020 until September 2021.

INTERVENTIONS

On warming, the oocytes were randomized to culture in IVM media with CCs (+CC) or without CCs (-CC). Germinal vesicles and MI oocytes were cultured in 25 μL (SAGE IVM medium) for 32 hours and 20-22 hours, respectively.

MAIN OUTCOME MEASURES

Oocytes with a polar body (MII) were randomized to confocal microscopy for analysis of spindle integrity and chromosomal alignment to assess nuclear maturity or to parthenogenetic activation to assess cytoplasmic maturity. Wilcoxon rank sum tests for continuous variables and the chi square or Fisher's exact test for categorical variables assessed statistical significance. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated.

RESULTS

Patient demographic characteristics were similar for both the GV and MI groups after randomization to +CC vs. -CC. No statistically significant differences were observed between +CC vs. -CC groups regarding the percentage of MII from either GV (42.5% [34/80] vs. 52.5% [42/80]; RR 0.81; 95% CI: 0.57-1.15]) or MI (76.3% [61/80]; vs. 72.5% [58/80]; RR 1.05; 95% CI: 0.88-1.26]) oocytes. An increased percentage of GV-matured MIIs underwent parthenogenetic activation in the +CC group (92.3% [12/13] vs. 70.8% [17/24]), but the difference was not statistically significant (RR 1.30; 95% CI: 0.97-1.75), whereas the activation rate was identical for MI-matured oocytes (74.3% [26/35] vs. 75.0% [18/24], CC+ vs. CC-; RR 0.99; 95% CI: 0.74-1.32). No significant differences were observed between +CC vs. -CC groups for cleavage of parthenotes from GV-matured oocytes (91.7% [11/12] vs. 82.4% [14/17]) or blastulation (0 for both) or for MI-matured oocytes (cleavage: 80.8% [21/26] vs. 94.4% [17/18]; blastulation: 0 [0/26] vs. 16.7% [3/18]). Further, no significant differences were observed between +CC vs. -CC for GV-matured oocytes regarding incidence of bipolar spindles (38.9% [7/18] vs. 33.3% [5/15]) or aligned chromosomes (22.2% [4/18] vs. 0.0 [0/15]); or for MI-matured oocytes (bipolar spindle: 38.9% [7/18] vs. 42.9% [2/28]); aligned chromosomes (35.3% [6/17] vs. 24.1% [7/29]).

CONCLUSIONS

Cumulus cell co-culture in this simple two-dimensional system does not improve rescue IVM of vitrified, warmed immature oocytes, at least by the markers assessed here. Further work is required to assess the efficacy of this system given its potential to provide flexibility in a busy, in vitro fertilization clinic.

From in vivo to in vitro: exploring the key molecular and cellular aspects of human female gametogenesis

Human oogenesis is a highly complex and not yet fully understood process due to ethical and technological barriers that limit studies in the field. In this context, replicating female gametogenesis in vitro would not only provide a solution for some infertility problems, but also be an excellent study model to better understand the biological mechanisms that determine the formation of the female germline. In this review, we explore the main cellular and molecular aspects involved in human oogenesis and folliculogenesis in vivo, from the specification of primordial germ cells (PGCs) to the formation of the mature oocyte. We also sought to describe the important bidirectional relationship between the germ cell and the follicular somatic cells. Finally, we address the main advances and different methodologies used in the search for obtaining cells of the female germline in vitro.

Advances in Oocyte Maturation In Vivo and In Vitro in Mammals

The quality and maturation of an oocyte not only play decisive roles in fertilization and embryo success, but also have long-term impacts on the later growth and development of the fetus. Female fertility declines with age, reflecting a decline in oocyte quantity. However, the meiosis of oocytes involves a complex and orderly regulatory process whose mechanisms have not yet been fully elucidated. This review therefore mainly focuses on the regulation mechanism of oocyte maturation, including folliculogenesis, oogenesis, and the interactions between granulosa cells and oocytes, plus in vitro technology and nuclear/cytoplasm maturation in oocytes. Additionally, we have reviewed advances made in the single-cell mRNA sequencing technology related to oocyte maturation in order to improve our understanding of the mechanism of oocyte maturation and to provide a theoretical basis for subsequent research into oocyte maturation.

Morphokinetic parameters of mouse oocyte meiotic maturation and cumulus expansion are not affected by reproductive age or ploidy status

INTRODUCTION

Morphokinetic analysis using a closed time-lapse monitoring system (EmbryoScope + ™) provides quantitative metrics of meiotic progression and cumulus expansion. The goal of this study was to use a physiologic aging mouse model, in which egg aneuploidy levels increase, to determine whether there are age-dependent differences in morphokinetic parameters of oocyte maturation.

METHODS

Denuded oocytes and intact cumulus-oocyte complexes (COCs) were isolated from reproductively young and old mice and in vitro matured in the EmbryoScope + ™. Morphokinetic parameters of meiotic progression and cumulus expansion were evaluated, compared between reproductively young and old mice, and correlated with egg ploidy status.

RESULTS

Oocytes from reproductively old mice were smaller than young counterparts in terms of GV area (446.42 ± 4.15 vs. 416.79 ± 5.24 µm2, p < 0.0001) and oocyte area (4195.71 ± 33.10 vs. 4081.62 ± 41.04 µm2, p < 0.05). In addition, the aneuploidy incidence was higher in eggs with advanced reproductive age (24-27% vs. 8-9%, p < 0.05). There were no differences in the morphokinetic parameters of oocyte maturation between oocytes from reproductively young and old mice with respect to time to germinal vesicle breakdown (GVBD) (1.03 ± 0.03 vs. 1.01 ± 0.04 h), polar body extrusion (PBE) (8.56 ± 0.11 vs. 8.52 ± 0.15 h), duration of meiosis I (7.58 ± 0.10 vs. 7.48 ± 0.11 h), and kinetics of cumulus expansion (0.093 ± 0.002 vs. 0.089 ± 0.003 µm/min). All morphokinetic parameters of oocyte maturation were similar between euploid and aneuploid eggs irrespective of age.

CONCLUSION

There is no association between age or ploidy and the morphokinetics of mouse oocyte in vitro maturation (IVM). Future studies are needed to evaluate whether there is an association between morphokinetic dynamics of mouse IVM and embryo developmental competence.

In vitro maturation of oocytes from stimulated IVF-ICSI cycles using autologous cumulus cell co-culture: A preliminary study

PURPOSE OF THE STUDY

In stimulated IVF-ICSI cycles, follicles at different stages of maturation can be aspirated during oocyte pickup. Nowadays, only mature oocytes (metaphase 2 stage) are used and immature oocytes (germinal vesicle and metaphase 1 stages), which are judged unfit for fertilization, are non-used at day 0. In our IVF center, the rate of immature oocytes recovered is around 25%. A significant number of this precious resource is therefore non-used every day in IVF laboratories. The objective of our study was to evaluate the competence of our in vitro maturation autologous coculture method on the maturation and developmental potential of immature oocytes obtained from stimulated IVF-ICSI cycles, in order to obtain additional embryos for the couple as a rescue system to increase the changes of cumulative pregnancy.

PATIENTS AND METHODS

This is a prospective study, carried out in the Reproductive Medicine and Biology Unit of the Amiens-Picardy University Hospital (France). It was included 14 couples, managed in IVF-ICSI in our center, from January to March 2020. Thirty-eight oocytes, identified as immature after cumulus-oocyte complexes (COC) stripping for ICSI, were placed in our in vitro maturation medium with the addition of autologous cumulus cells. Oocytes that had reached the metaphase II stage after a maximum of 36 hours of maturation were microinjected. The fertilization and embryonic development potential of the in vitro matured oocytes were compared to those of 148 in vivo matured "siblings" oocytes from the same oocyte retrieval, and then also compared to those of 127 in vivo matured oocytes from different patients (control group).

MAIN OUTCOME MEASURE(S)

Maturation rate, fertilization rate, early cleavage rate and developmental activity to blastulation rate.

SECOND OUTCOME MEASURE(S)

Embryo quality at cleavage and blastocyst stages, blastulation rate, and useful blastulation rate.

RESULTS

No significant difference was found in the main and secondary criteria of the study compared to the "siblings" in vivo matured oocytes from the same oocyte retrieval. However, a significant difference was obtained on the rate of early cleavage and useful blastulation when our cohort was compared to mature in vivo oocytes from different patients (control group).

CONCLUSION

This study has shown that after incubation in our in vitro maturation autologous cumulus cell co-culture with cumulus-oocyte cells, immature oocytes recovered during stimulated cycles can give rise to competent oocytes, i.e., capable of being fertilized, of cleaving, and of developing into embryos up to the blastocyst stage. Our study therefore seems to be in the direction of a favorable use of these immature oocytes obtained after stimulated IVF-ICSI cycles. The continuation of this study by including a larger number of oocytes is necessary in order to evaluate the real contribution of this technique in routine.

Effect of In Vitro Maturation of Human Oocytes Obtained After Controlled Ovarian Hormonal Stimulation on the Expression of Development- and Zona Pellucida-Related Genes and Their Interactions

In an in vitro fertilization program, approximately 10-15% of oocytes obtained after controlled ovarian stimulation are immature, with germinal vesicles (GVs). These oocytes are usually discarded in clinical practice; however, an in vitro maturation (IVM) procedure can be applied to mature them. There are scarce data in the literature on the effect of IVM on the expression of important development- and zona pellucida (ZP)-related genes in human oocytes; therefore, we wanted to determine this. One hundred nine human oocytes were collected from patients enrolled in an intracytoplasmic sperm injection program. The expression of the BMP4, GDF9, ZP1, ZP2, ZP3, and ZP4 genes was analyzed using RT-qPCR in oocytes matured in vitro with different reproductive hormones in the IVM medium (AMH, FSH + hCG, FSH + hCG + AMH), in in vivo matured oocytes and in immature oocytes with GVs. No statistically significant differences in the expression of selected genes in oocytes were observed among groups with different reproductive hormones in IVM medium. However, several interesting significant correlations were found between BMP4 and GDF9, and ZP1 and ZP4; between GDF9 and ZP1, and ZP2 and ZP4; and between ZP1 and ZP3 and ZP4 in the in vitro matured oocytes, while no such correlations were present in other groups of oocytes. The type of reproductive hormone in the maturation medium does not affect the expression of the analyzed genes in oocytes during the maturation process. However, the in vitro maturation procedure itself generated correlations among analyzed genes that were otherwise not present in in vivo matured and immature oocytes.

Effects of ABVD chemotherapy on ovarian function: epidemiology, hormonal dosages and ultrasound morphologic analyses in 270 patients with Hodgkin's disease

Introduction

Classical Hodgkin Lymphoma (HL) is a lymphoproliferative disease typically diagnosed in the young. The excellent results obtained with current treatment lead to long survival with age-related complications affecting patients' survival and quality of life. One issue affecting HL patients is infertility. This problem can be easily overcome in males with seminal liquid cryopreservation, however, in females it is more complex either in terms of the quality of the cryopreserved material or the patients' age at diagnosis. Moreover, not all chemo- or radio-therapies have the same negative impact on fertility.The main objectives of this study was to collect epidemiological information on HL patients involved in fertility preservation counseling and to analyze the impact of ABVD (adriamycin, bleomycin, vinblastine, and dacarbazine), the standard treatment for HL, on ovarian function, hormonal levels and ovarian and uterine tissue morphologies. Patterns of fertility preservation were also reported.

Methods

Data were obtained from 270 female patients at HL onset who were interested in fertility counseling prior to therapy initiation. Each patient was assessed at HL diagnosis for levels of Anti-Mullerian Hormone (AMH), Follicle Stimulating Hormone (FSH), and 17β-oestradiol (17β-oe), with additional assessments at 6 and 12 months after chemotherapy. Patients were evaluated with ultrasound scans to study the number of ovarian follicles and the degree of uterine thickness at the same timepoints.

Results

The average patient AMH level showed a statistically significant reduction at 6 months after chemotherapy (p=0.05) and by the 12 month time point returned to near pre-chemotherapy values. FSH and 17β-oe levels did not significantly vary throughout the study period. ABVD chemotherapy was associated with a significant reduction of both ovarian follicles and endometrial thickness at the 6 month time point followed by a recovery at the 12 time point in both ovaries. Different results were observed when patients changed treatment to a more intensive one.

Discussion

Based on the results from the hormonal measurements and the follicle echography, it appears that the toxic effect of ABVD on fertility is transient, whereas, in contrast, more intensive therapies may potentially be more harmful and long-lasting.

HDAC1 in the Ovarian Granulosa Cells of Tan Sheep Improves Cumulus Cell Expansion and Oocyte Maturation Independently of the EGF-like Growth Factors

Previous studies have shown that some of the histone deacetylases (HDACs) play diverse roles in the regulation of ovarian somatic cell development, oocyte maturation and early embryonic development in different species including sheep. This study aimed to clarify whether HDAC1 also played pivotal roles in regulating oocyte maturation in Tan sheep. The results showed that HDAC1 was expressed in the nuclei of both the granulosa cells and oocytes of the growing follicles in the Tan sheep's ovaries. However, the level of HDAC1 was unaffected by luteinizing hormone (LH) induction in cultured granulosa cells. Meanwhile, the specific inhibition of HDAC1 using pyroxamide did not induce significant changes in the expression levels of EGF-like growth factors in vitro, whereas both the cumulus expansion and oocyte maturation of the cultured cumulus oocyte complexes (COCs) were significantly inhibited by pyroxamide. Additionally, the numbers of histone acetylation sites (H4K5, H4K12, H3K14 and H3K9) in ovarian granulosa cells were significantly increased. In conclusion, a constant expression of HDAC1 in the growing follicles of Tan sheep may be pivotal for supporting oocyte growth and maturation, although its action may not be closely correlated with LH induction, nor does it directly affect the expression of the EGF-like factors. Our study implies that there may exist diverse functions of the respective HDACs in modulating female reproduction in sheep.

Study on the Influencing Mechanism of Human Chorionic Gonadotropin (hCG) on Oocyte Maturation in Patients with Polycystic Ovary Syndrome

The study was aimed at investigating the influence of human chorionic gonadotropin (hCG) hormone on oocyte maturation in the patients with polycystic ovary syndrome (PCOS). A total of 54 patients with PCOS who received in vitro maturation (IVM) treatment in the Cheeloo College of Medicine, Shandong University, were divided into two groups: one group who underwent hCG injections was the observation group (OG; n = 27) and other was the control group (CG; n = 27) with no hCG injection. The oocyte development and the expression of steroid hormone synthesis-related genes including gonadotropin-releasing hormone receptor (GnRHR), Conexin43, epidermal growth factor-related genes, luteinizing hormone/choriogonadotropin receptor (LHCGR), epiregulin (EREG), and vascular endothelial growth factor (VEGF) were examined. The human ovarian granulosa cell line (SVOG cells) and ovarian epithelial cell line (HOSEpiC cells) were employed to analyze the effect of hCG on the biological behaviour of cells. As a result, OG showed higher normal fertilization, cleavage, and high-qualified embryo rate than CG. Expression levels of GnRHR, Cx43, LHCGR, EREG, and VEGF were significantly elevated in granulosa cells in the OG group. Western blot revealed that phosphoinositide 3-kinase (PI3K), protein kinase B (AKT), and rapamycin (mTOR) proteins were decreased in granulosa cells under hCG intervention. A biological behaviour test indicated that the multiplication capacity of hCG-intervened SVOG and HOSEpiC was increased, while the apoptosis was decreased. In conclusion, hCG could accelerate follicular development and oocyte maturation by activating oocyte maturation genes in PCOS patients, which could significantly improve and popularize the application of IVM technology.

Ovarian Reserve and ART Outcomes in Blepharophimosis-Ptosis-Epicanthus Inversus Syndrome Patients With FOXL2 Mutations

Objective

To characterize the status of ovarian reserve and ART outcomes in BPES women and provide informative reference for clinical diagnosis and treatment.

Methods

Twenty-one women with BPES were screened for mutations in the FOXL2 gene and underwent assisted reproductive technology (ART) treatment. Indicators for ovarian reserve and ART outcomes were compared between patients with and without FOXL2 mutations. Additionally, ART outcomes were compared among patients with different subtypes of FOXL2 mutations.

Results

A total of 13 distinct heterozygous variants in the FOXL2 gene were identified in 80.95% of BPES women, including 4 novel mutations with plausible pathogenicity (c.173_175dup, c.481C>T, c.576del and c.675_714del). Compared to non-mutation group, patients with FOXL2 mutations had elevated levels of FSH (P=0.007), decreased AMH levels (P=0.012) and less AFC (P=0.015). They also had worse ART outcomes with large amount of Gn dosage (P=0.008), fewer oocytes (P=0.001), Day3 good quality embryos (P=0.001) and good quality blastocysts (P=0.037), and a higher cancellation rate (P=0.272). High heterogeneity of ART outcomes existed in BPES patients with different FOXL2 mutation types.

Conclusions

BPES patients with FOXL2 mutations had diminished ovarian reserve and adverse ART outcomes. The genotype-reproductive phenotype correlations were highly heterogeneous and cannot be generalized. Genetic counseling for fertility planning and preimplantation or prenatal genetic diagnosis to reduce offspring inheritance are recommended.

Comparative transcriptome analysis identifies important maternal molecules and associated biological pathways for pig and human mature oocytes

Recent researches reveal that during oocyte maturation, species-specific molecular profile exists, and has important functional roles. However, molecular differences between pig (a larger animal model for human reproduction) and human mature oocytes remain unknown. Here, by comparative transcriptome analyses of single cell RNA-seq data, we aimed to identify the common and unique maternal factors and associated biological processes between in vivo and in vitro matured pig oocytes, and between in vitro matured human and pig oocytes. Annotated protein coding mRNAs were identified in pig in vivo (11147) and in vitro (11997), and human in vitro (14491) MII oocytes, respectively. For in vivo and in vitro derived pig MII oocytes, 10551 annotated maternal mRNAs were common, mainly enriched in signaling pathways such as cell cycle, oocyte meiosis, microtubule cytoskeleton, MAPK, RNA processing/binding. Besides, in vivo (596) and in vitro (1446) pig MII-specific mRNAs and their involved signaling pathways (in vivo: Bmp, calcium-mediated signaling, PI3K-Akt; in vitro: growth factor activity, JAK-STAT, cytokine-cytokine receptor interaction, calcium signaling pathway) were also found. As for in vitro derived human and pig MII oocytes, 10285 annotated mRNAs were common, enriched in a variety of signaling pathways (cell cycle, oocyte meiosis, microtubule, AMPK, RNA splicing, protein serine/threonine kinase activity, etc). In vitro MII-specific mRNAs were found for humans (4206) and pigs (1712), which were also enriched in species-specific signaling pathways (humans: golgi related terms, transcription repressor and hormone activity; pigs: ATP biosynthetic process, G protein-coupled peptide receptor activity, animoacyl-tRNA biosynthesis), respectively. These findings improve our understanding on oocyte maturation, and also the limitations of pig model for human oocyte maturation and fertilization.

Fertilization, Oocyte Activation, Calcium Release and Epigenetic Remodelling: Lessons From Cancer Models

Oocyte activation deficiency (OAD) is the basis of Total Fertilisation Failure (TFF) and is attributed to mutations in the PLCζ gene—termed male factor infertility. This derives abnormal Ca²⁺ oscillations and could be the main cause of primary disruptions in the gene expression of Ca²⁺-related proteins. Epigenetic mechanisms are universally accepted as key regulators of gene expression. However, epigenetic dysregulations have not been considered as potential mechanisms of oocyte-borne OAD. Herein, we discuss changes in the DNA methylome during oogenesis and embryogenesis. We further highlight key pathways comprising the oocyte Ca²⁺ toolkit, which could be targets of epigenetic alterations, especially aberrations in DNA methylation. Considering that the vast majority of epigenetic modifications examined during fertilization revolve around alterations in DNA methylation, we aim in this article to associate Ca²⁺-specific mechanisms with these alterations. To strengthen this perspective, we bring evidence from cancer research on the intricate link between DNA methylation and Ca²⁺ signaling as cancer research has examined such questions in a lot more detail. From a therapeutic standpoint, if our hypothesis is proven to be correct, this will explain the cause of TFF in idiopathic cases and will open doors for novel therapeutic targets.

Changes in the Mitochondria-Related Nuclear Gene Expression Profile during Human Oocyte Maturation by the IVM Technique

To address which mitochondria-related nuclear differentially expressed genes (DEGs) and related pathways are altered during human oocyte maturation, single-cell analysis was performed in three oocyte states: in vivo matured (M-IVO), in vitro matured (M-IVT), and failed to mature in vitro (IM-IVT). There were 691 DEGs and 16 mitochondria-related DEGs in the comparison of M-IVT vs. IM-IVT oocytes, and 2281 DEGs and 160 mitochondria-related DEGs in the comparison of M-IVT vs. M-IVO oocytes, respectively. The GO and KEGG analyses showed that most of them were involved in pathways such as oxidative phosphorylation, pyruvate metabolism, peroxisome, and amino acid metabolism, i.e., valine, leucine, isoleucine, glycine, serine, and threonine metabolism or degradation. During the progress of oocyte maturation, the metabolic pathway, which derives the main source of ATP, shifted from glucose metabolism to pyruvate and fatty acid oxidation in order to maintain a low level of damaging reactive oxygen species (ROS) production. Although the immature oocytes could be cultured to a mature stage by an in vitro technique (IVM), there were still some differences in mitochondria-related regulations, which showed that the mitochondria were regulated by nuclear genes to compensate for their developmental needs. Meanwhile, the results indicated that the current IVM culture medium should be optimized to compensate for the special need for further development according to this disclosure, as it was a latent strategy to improve the effectiveness of the IVM procedure.

In vitro maturation of immature oocytes for fertility preservation in cancer patients compared to control patients with fertility problems in an in vitro fertilization program

Background

The aim of this study was to determine whether in vitro maturation (IVM) of immature oocytes after controlled hormonal stimulation of the ovaries could be important in cancer patients to improve their chances of conception in the future.

Patients and methods

After ovarian stimulation in cancer patients, the number of oocytes and their quality and maturity were compared to control patients with fertility problems in the in vitro fertilization (IVF) program. In both groups of patients, immature oocytes at the developmental stage of germinal vesicle were matured in vitro and the proportion of oocytes that matured in vitro was compared between groups. In a subset of women with fertility problems, intracytoplasmic sperm injection (ICSI) was performed on IVM oocytes to assess their ability to be fertilized and develop into an embryo compared to vivo matured oocytes in the same cycles and consider the procedure in cancer patients.

Results

In patients with different cancers, the disease did not affect the number and quality of retrieved oocytes. In cancer patients, there was even a significantly lower proportion of immature oocytes than in patients with fertility problems (30.0% vs. 43.6%; P < 0.05). However, in patients with cancer, fewer oocytes per patient matured in vitro than in patients with fertility problems (1.39 ± 1.04 vs. 2.48 ± 1.83; P < 0.05). After ICSI, the proportions of fertilized oocytes and fertilized oocytes developing into an embryo did not differ between oocytes matured in vitro and in vivo in the same cycles.

Conclusions

Oocyte IVM is proving to be a reliable procedure for resolving immature oocytes after controlled ovarian stimulation in cancer patients.

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.

Factors Influencing the In Vitro Maturation (IVM) of Human Oocyte

In vitro maturation (IVM) of oocytes is a promising assisted reproductive technology (ART) deemed as a simple and safe procedure. It is mainly used in patients with impaired oocyte maturation and in fertility preservation for women facing the risk of losing fertility. However, to date, it is still not widely used in clinical practice because of its underperformance. The influencing factors, such as biphasic IVM system, culture medium, and the supplementation, have a marked effect on the outcomes of oocyte IVM. However, the role of different culture media, supplements, and follicular priming regimens in oocyte IVM have yet to be fully clarified and deserve further investigation.

Acentriolar spindle assembly in mammalian female meiosis and the consequences of its perturbations on human reproduction

The purpose of meiosis is to generate developmentally competent, haploid gametes with the correct number of chromosomes. For reasons not completely understood, female meiosis is more prone to chromosome segregation errors than meiosis in males, leading to an abnormal number of chromosomes, or aneuploidy, in gametes. Meiotic spindles are the cellular machinery essential for the proper segregation of chromosomes. One unique feature of spindle structures in female meiosis is spindles poles that lack centrioles. The process of building a meiotic spindle without centrioles is complex and requires precise coordination of different structural components, assembly factors, motor proteins, and signaling molecules at specific times and locations to regulate each step. In this review, we discuss the basics of spindle formation during oocyte meiotic maturation focusing on mouse and human studies. Finally, we review different factors that could alter the process of spindle formation and its stability. We conclude with a discussion of how different assisted reproductive technologies (ART) could affect spindles and the consequences these perturbations may have for subsequent embryo development.

Developmental potential of immature human oocytes aspirated after controlled ovarian stimulation

PURPOSE

Intracytoplasmic sperm injection (ICSI) for initially immature oocytes that mature in vitro is controversial and practice varies widely. While it may increase the number of usable embryos, it may also be time-intensive and potentially low-yield. This study sought to elucidate which patients may benefit from ICSI of initially immature oocytes that matured in vitro.

METHODS

A retrospective study comparing fertilization, cleavage, blastulation, and embryo usage rates between sibling initially immature and mature oocytes that underwent ICSI between 2015 and 2019 was performed. Outcomes of initially immature oocytes were stratified by initial maturation stage, timing of progression to metaphase II (MII) in vitro, percentage of mature oocytes in the cycle, and female age.

RESULTS

Ten thousand eight hundred seventeen oocytes from 889 cycles were included. Of 3137 (29.0%) initially immature oocytes, 418 (13.3%) reached MII later on the day of retrieval (day 0) and 1493 (47.6%) on day 1. Overall, embryos originating from initially immature oocytes had lower cleavage and blastulation rates compared to those from initially mature oocytes (P<0.05, all groups). However, embryos from oocytes that matured later on day 0 comprised a unique subset that had clinically similar cleavage (75% vs 80%, RR 0.93, P=0.047) and blastulation rates (41% vs 50%, RR 0.81, P=0.024) compared to initially mature oocytes. Women with low percentages of mature oocytes in the cycle overall and women ≥40 in cleavage cycles derived the highest relative benefit from the use of immature oocytes.

CONCLUSION

ICSI of immature oocytes, particularly those that mature later on the day of retrieval, may improve numbers of usable embryos. This study supports routine reassessment of immature oocytes for progression to MII and ICSI on day 0. An additional reassessment on day 1 may also be of use in older women or those with low percentage of mature oocytes.

Granulosa cells affect in vitro maturation and subsequent parthenogenetic development of buffalo (Bubalus bubalis) oocytes

Granulosa cells (GCs) play a crucial role in follicular development and atresia. Previous studies have showed that GCs in the form of monolayer influenced in vitro maturation (IVM) of oocytes. However, the effects of GCs in the form of conditioned medium and monolayer on IVM and development competence of buffalo oocytes remain unclear. In the present study, we examined the impacts of GC-conditioned medium (GCCM) and monolayer GC on maturation efficiency and embryo development of buffalo oocytes after parthenogenetic activation (PA). Our results showed that GCCM that was collected on day 2 and added to IVM medium at a 20% proportional level (2 days and 20%) exerted significant negative effects on IVM rate (41.6% vs. 44.5%), but significantly enhanced embryo development (oocyte cleavage, 81.3% vs. 69.3%; blastocyst formation, 36.3% vs. 29.3%) of buffalo oocytes after PA compared with the control group. Furthermore, monolayer GC significantly reduced both maturation efficiency (40.2% vs. 44.5%) and embryo development (oocyte cleavage, 60.6% vs. 69.3%; blastocyst formation, 20.6% vs. 29.3%) of buffalo oocytes after PA compared to the control group. Our study indicated that GCs in the form of GCCM (2 days and 20%) and monolayer GC had different effects on IVM and subsequent parthenogenetic development of buffalo oocytes.

Single-cell multiomic analysis of in vivo and in vitro matured human oocytes

STUDY QUESTION

Are there any differences between in vivo (IVV) and in vitro (IVT) matured metaphase II (MII) oocytes at the molecular level?

SUMMARY ANSWER

Between IVV and IVT oocytes, 507 differentially expressed genes (DEGs) were identified; the non-CpG methylomes were significantly different, but the CpG methylomes and genomic copy number variations (CNVs) were similar.

WHAT IS KNOWN ALREADY

A previous study using microarray and single-cell RNA-seq analysis revealed that numerous genes were differentially expressed between IVV and IVT oocytes. Independent studies of DNA methylation profiling in human oocytes have revealed negative correlations between gene transcription and the DNA methylation level at gene promoter regions. No study has compared global CpG or non-CpG methylation between these two groups of oocytes. Although a high level of aneuploidy has been reported in MII oocytes, no direct comparison of IVV and IVT oocytes based on single-cell sequencing data has been performed.

STUDY DESIGN, SIZE, DURATION

We collected eight IVV oocytes from six patients and seven IVT oocytes from seven patients and then analysed each oocyte using the previously established single-cell triple omics sequencing (scTrioseq) analysis to determine associations among the transcriptome, DNA methylome and chromosome ploidy in the oocytes.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All IVV oocytes were donated by patients who received 150 IU gonadotropin per day from the third day of their menstrual cycle, followed by GnRH antagonist after 5 days of gonadotropin stimulation. All IVT oocytes were from immature oocytes which were donated by volunteers undergoing delivery by caesarean section then cultured in oocyte maturation medium containing 75 mIU/ml hMG for 24 to 48 h. Every single oocyte was analysed using the previously established single-cell multiomic sequencing analysis.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 507 genes differentially expressed between the IVV (n = 8) and IVT (n = 7) oocytes, even though their global transcriptome profiles were similar. The enriched genes in IVV oocytes were related to the cell cycle process while those in IVT oocytes were related to mitochondrial respiration biogenesis. Although the global CpG methylation of the two groups of oocytes was similar, the non-CpG methylation level in IVV oocytes was higher than that in IVT oocytes. A high aneuploidy ratio was found in both groups, but the aneuploidy did not affect transcription according to the correlation analysis.

LARGE-SCALE DATA

N/A.

LIMITATIONS AND REASONS FOR CAUTION

Due to the difficulty in collecting MII oocytes, especially IVV matured oocytes, the sample size was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings indicate that single-cell multiomic sequencing can be utilised to examine the similarity and differences between IVV and IVT matured MII oocytes.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Ministry of Science and Technology of China, National Key R&D Program of China (No. 2017YFC1001601). The donated oocytes were collected by Shanghai Tenth People's Hospital. The authors declare no competing interests.

Creating an Artificial 3-Dimensional Ovarian Follicle Culture System Using a Microfluidic System

We hypothesized that the creation of a 3-dimensional ovarian follicle, with embedded granulosa and theca cells, would better mimic the environment necessary to support early oocytes, both structurally and hormonally. Using a microfluidic system with controlled flow rates, 3-dimensional two-layer (core and shell) capsules were created. The core consists of murine granulosa cells in 0.8 mg/mL collagen + 0.05% alginate, while the shell is composed of murine theca cells suspended in 2% alginate. Somatic cell viability tests and hormonal assessments (estradiol, progesterone, and androstenedione) were performed on days 1, 6, 13, 20, and 27. Confocal microscopy confirmed appropriate compartmentalization of fluorescently-labeled murine granulosa cells to the inner capsule and theca cells to the outer shell. Greater than 78% of cells present in capsules were alive up to 27 days after collection. Artificially constructed ovarian follicles exhibited intact endocrine function as evidenced by the production of estradiol, progesterone, and androstenedione. Oocytes from primary and early secondary follicles were successfully encapsulated, which maintained size and cellular compartmentalization. This novel microfluidic system successfully encapsulated oocytes from primary and secondary follicles, recapitulating the two-compartment system necessary for the development of the mammalian oocyte. Importantly, this microfluidic system can be easily adapted for sterile, high throughput applications.

Meiosis Resumption of Immature Human Oocytes following Treatment with Calcium Ionophore In Vitro

Objective:

In vitro maturation (IVM) of human oocytes is used to induce meiosis progression in immature retrieved oocytes. Calcium (Ca2+) has a central role in oocyte physiology. Passage through meiosis phase to another phase is controlled by increasing intracellular Ca2+. Therefore, the current research was conducted to evaluate the role of calcium ionophore (CI) on human oocyte IVM.

Materials and Methods:

In this clinical trial study, immature human oocytes were obtained from 216 intracytoplasmic sperm injection (ICSI) cycles. After ovarian stimulation, germinal vesicle (GV) stage oocytes were collected and categorized into two groups: with and without 10 µM CI treatment. Next, oocyte nuclear maturation was assessed after 24–28 hours of culture. Real-time reverse transcription polymerase chain reaction (RT-PCR) was used to assess the transcript profile of several oocyte maturation-related genes (MAPK3, CCNB1, CDK1, and cyclin D1 [CCND1]) and apoptotic-related genes (BCL-2, BAX, and Caspase-3). Oocyte glutathione (GSH) and reactive oxygen species (ROS) levels were assessed using Cell Tracker Blue and 2’,7’-dichlorodihydrofluorescein diacetate (H2DCFDA) fluorescent dye staining. Oocyte spindle configuration and chromosome alignment were analysed by immunocytochemistry.

Results:

The metaphase II (MII) oocyte rate was higher in CI‐treated oocytes (73.53%) compared to the control (67.43%) group, but this difference was not statistically significant (P=0.13). The mRNA expression profile of oocyte maturation-related genes (MAPK3, CCNB1, CDK1, and CCND1) (P<0.05) and the anti-apoptotic BCL-2 gene was remarkably up-regulated after treatment with CI (P=0.001). The pro-apoptotic BAX and Caspase-3 relative expression levels did not change significantly. The CI‐treated oocyte cytoplasm had significantly higher GSH and lower ROS (P<0.05). There was no statistically significant difference in meiotic spindle assembly and chromosome alignment between CI treatment and the control group oocytes.

Conclusion:

The finding of the current study supports the role of CI in meiosis resumption of human oocytes. (Registration Number: IRCT20140707018381N4)

Improved maturation competence of ovarian tissue oocytes using a biphasic in vitro maturation system for patients with gynecological malignancy: a study on sibling oocytes

PURPOSE

To investigate the developmental competence of ovarian tissue oocytes from patients with gynecological tumors using a biphasic in vitro maturation system with capacitation (CAPA-IVM) in comparison with standard IVM.

METHODS

This sibling pilot study included 210 oocytes in 10 patients with gynecological malignancies. After ovariectomies, ovaries were cut into even halves and immature cumulus-oocyte complexes (COCs) were retrieved from the ovarian tissue. COCs were separately cultured in either a biphasic CAPA-IVM system for 53 h or in standard IVM for 48 h. After IVM, all COCs were denuded and mature oocytes were either vitrified (N=5) or used for ICSI (N=5). Embryos were cultured for 5-6 days and obtained blastocysts were vitrified.

RESULTS

Use of the CAPA-IVM system led to a higher meiotic maturation rate in ovarian tissue oocytes (OTO) compared to standard IVM (56 vs 35%, p=0.0045) and had a tendency to result in lower degeneration after IVM. Only the CAPA-IVM method supported blastocyst formation.

CONCLUSIONS

The biphasic in vitro maturation system improved the competence of OTO in comparison to the standard IVM method. The study suggests that fertility preservation programs could become more efficient using IVM after capacitation culture.

Increased Environment-Related Metabolism and Genetic Expression in the In Vitro Matured Mouse Oocytes by Transcriptome Analysis

Infertility in humans at their reproductive age is a world-wide problem. Oocyte in vitro maturation (IVM) is generally used in such cases to acquire the embryo in assisted reproductive technology (ART). However, the differences between an in vivo (IVO) and IVM culture environment in the RNA expression profile in oocytes, remains unclear. In this study, we compared the global RNA transcription pattern of oocytes from in vitro and in vivo maturation. Our results showed that 1,864 genes differentially expressed between the IVO and IVM oocytes. Among these, 1,638 genes were up-regulated, and 226 genes were down-regulated, and these changes were mainly divided into environmental adaption, metabolism, and genetic expression. Our detailed analysis showed that the expression of genes that belonged to metabolism-related processes such as energy metabolism, nucleotide metabolism, and carbohydrate metabolism was changed; and these genes also belonged to organismal systems including environmental adaptation and the circulatory system; moreover, we also found that the relative gene expression of genetic expression processes, such as protein synthesis, modification, and DNA replication and repair were also altered. In conclusion, our data suggests that in vitro maturation of mouse oocyte resulted in metabolism and genetic expression changes due to environmental changes compared with in vivo matured oocytes.

Human Oocytes Express Both ACE2 and BSG Genes and Corresponding Proteins: Is SARS-CoV-2 Infection Possible?

In addition to a number of scientific and medical questions about SARS-CoV-2 infection that still need to be answered, there is also the question of how this highly virulent virus and COVID-19 disease affect gametogenesis in humans. Even more important is the question of whether the virus can also enter and infect oocytes and possibly alter them in an unknown way, which could also affect the development and status of the human embryo. The answers to these questions are still poorly known, so we reviewed the human oocyte transcriptome and proteome obtained in our previous studies and found that human oocytes from the in vitro fertilization program expressed both the ACE2 and BSG genes and the corresponding ACE2 and BSG proteins. This means that human oocytes possess the molecular 'machinery' to facilitate SARS-CoV-2 entrance and infection. According to various studies, especially in animal models, different viruses can infect oocytes, so infection of the oocyte with SARS-Cov-2 cannot be completely ruled out. A hypothetical model of human oocyte infection with this virus has been proposed.

Theca cell-conditioned medium added to in vitro maturation enhances embryo developmental competence of buffalo (Bubalus bubalis) oocytes after parthenogenic activation

Theca cells (TCs) play a key role in follicular growth and atresia. TCs synthesize androgens that act as substrate for granulosa cells (GCs) aromatization to estrogens needed for oocyte maturation. However, the effects of TCs in the form of conditioned medium on in vitro maturation (IVM) and developmental competence of buffalo oocytes remain unclear. In the present study, we examined the impacts of TC-conditioned medium (TCCM) on maturation efficiency and embryo development of buffalo oocytes after parthenogenic activation (PA). Our results showed that TCCM that was collected on day 2 and added to IVM medium at a 20% proportional level (2 days & 20%) exerted no significant effect on IVM rate (43.06% vs. 44.71%), but significantly (p  < .05) enhanced embryo development (oocyte cleavage, 80.93% vs. 69.66%; blastocyst formation, 39.85% vs. 32.84%) of buffalo oocytes after PA compared with the control group. However, monolayer TC significantly (p < .05) promoted both maturation efficiency (48.84% vs. 44.53%) and embryo development (oocyte cleavage, 80.39% vs. 69.32%; blastocyst formation, 35.38% vs. 29.25%) of buffalo oocytes after PA compared to that in the control group. Furthermore, TCs secreted some testosterone into the conditioned medium, which significantly (p < .05) promoted the expression levels of oestrogen synthesis-related genes (CYP11A1, CYP19A1 and 17β-HSD) in buffalo cumulus-oocyte complexes (COCs). Our study indicated that TCCM (2 days & 20%) did not significantly affect IVM efficiency, but enhanced embryo developmental competence of oocytes after PA principally by stimulating the secretion of testosterone and facilitating estradiol synthesis of buffalo COCs.

Exposing Mouse Oocytes to MitoQ During In Vitro Maturation Improves Maturation and Developmental Competence

Background and Purpose:

Mitochondrion is the main indicator of oocyte quality and one of the components of oocyte, which is sensitive to oxidative damage during the maturation process. Mitoquinone mesylate (MitoQ) is a strong antioxidant targeting mitochondria as well as anti-apoptotic agent. However, the effect of MitoQ on the quality of oocytes during in vitro maturation (IVM) is still unknown.

Objectives:

This study investigated the possible effects of MitoQ on maturation and developmental competency in mice oocytes.

Materials and Methods:

The oocytes were collected at germinal vesicle stage from 6-8-week old female NMRI mice and then cultured in TCM-199 medium supplemented with 0, 0.01, 0.02 and 0.04 µM MitoQ. The sham group was treated with DMSO (0.01% v.v). Then intracellular Glutathione (GSH), reactive oxygen species (ROS) levels, mitochondria membrane potential (ΔΨm), as well as in vitro fertilization (IVF) rate in the 18-20 h matured oocytes and metaphase II (MII) oocytes (in vivo-control), were assessed.

Results:

The results showed that between three dose of MitoQ, the 0.02 µM significantly increased nuclear maturation rate, GSH level, fertilization rate and blastulation (92.6, 231.7, 90.19 and 81.66%, respectively) than the in vitro-control (71.14, 152, 78.84 and 73.50%, respectively) and more comparable to that of the in vivo matured oocytes (100, 243.5, 92.10 and 83%, respectively). Also, the mitochondria membrane potential in the 0.02 µM MitoQ was significantly higher compared with those in the other groups (4.4). However, the intracellular ROS level in 0.02 µM MitoQ was significantly decreased (38.72%) compared to in vitro-control (82.2%) and was similar to the in vivo-control (33.5%).

Conclusion:

The results indicated that supplementation of IVM medium with MitoQ (specially 0.02 µM) enhance maturation and fertilization rate. In conclusion, MitoQ might be considered as a novel component that could be added to IVM media.

Metabolic cooperation in the ovarian follicle

Granulosa cells (GCs) are somatic cells essential for establishing and maintaining bi-directional communication with the oocytes. This connection has a profound importance for the delivery of energy substrates, structural components and ions to the maturing oocyte through gap junctions. Cumulus cells, group of closely associated GCs, surround the oocyte and can diminished the effect of harmful environmental insults. Both GCs and oocytes prefer different energy substrates in their cellular metabolism: GCs are more glycolytic, whereas oocytes rely more on oxidative phosphorylation pathway. The interconnection of these cells is emphasized by the fact that GCs supply oocytes with intermediates produced in glycolysis. The number of GCs surrounding the oocyte and their age affect the energy status of oocytes. This review summarises available studies collaboration of cellular types in the ovarian follicle from the point of view of energy metabolism, signaling and protection of toxic insults. A deeper knowledge of the underlying mechanisms is crucial for better methods to prevent and treat infertility and to improve the technology of in vitro fertilization.