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Bisphenol A (BPA) is a well-known environmental endocrine disruptor that has detrimental effects on reproduction. This study aimed to investigate whether BPA exposure could disrupt the function of cumulus cells and influence oocyte maturation and development. Porcine oocytes at the germinal vesicle stage were exposed to BPA for 44 h. The results revealed that BPA exposure led to dysfunction in cumulus cells by inhibiting meiotic division, inducing endoplasmic reticulum stress, and disrupting steroid synthesis. Furthermore, BPA exposure significantly increased reactive oxygen species and caused abnormal distribution of mitochondria in the oocytes. Notably, matured oocytes in the MII stage from the BPA-exposed groups showed significantly reduced development to the blastocyst stage, along with increased autophagy and apoptosis. These findings suggest that cumulus-oocyte complexes are sensitive to BPA exposure during the germinal vesicle stage, and the toxic effects of BPA on cumulus cells can severely inhibit oocyte and parthenogenetic embryos development. [Display omitted] [ABSTRACT FROM AUTHOR]

Optimizing oocyte maturation and embryo culture media could enhance in vitro embryo production. The purpose of the present study was to investigate the role of supplementing one carbon metabolism (OCM) substrates and its cofactors (Cystine, Zinc, Betaine, B2, B3, B6, B12 and 5-methyltetrahydrofolate) in maturation and/or embryo culture media on the rate of blastocyst formation and pregnancy outcomes following the transfer of the resulting blastocysts in bovines. In the first experiment, 2537 bovine oocytes were recovered from slaughterhouse ovaries and then matured either in conventional maturation medium (IVM) or IVM supplemented with OCM substrates (Sup-IVM). After in vitro fertilization, the putative zygotes from each treatment (IVM or Sup-IVM) were cultured in the media either without (IVM/IVC or Sup-IVM/IVC) or with (IVM/Sup-IVC or Sup-IVM/Sup-IVC) OCM supplementation. The blastocyst rate, assessed on day 8, was significantly increased in Sup-IVM/IVC group (34.90 ± 2.52) as compared to IVM/IVC (17.06 ± 1.69; P = 0.0001) and Sup-IVM/Sup-IVC (20.29 ± 2.75; P = 0.004) and non-significantly as compared to IVM/Sup-IVC (24.86 ± 5.37). In the second experiment, non-matured bovine oocytes were collected by transvaginal ovum pick up after FSH stimulation, randomly allocated into IVM/IVC (n = 275) and Sup-IVM/IVC (n = 260) and the blastocysts achieved at day 7 were transferred in recipient cattle. The blastocyst rate was significantly higher in Sup-IVM/IVC group (38.85%) as compared to the IVM/IVC group (23.64%; P < 0.0001). After single embryo transfer, the supplemented blastocysts were at least as competent as non-supplemented ones with a non-significantly higher (20% vs. 14%) pregnancy rate and the advantage of several good quality blastocysts available for future use. In conclusion, optimizing the maturation medium with OCM substrates and its cofactors could enhance the formation of viable blastocysts with the potential to increase the cumulative birth rate in cattle. [ABSTRACT FROM AUTHOR]

Background: Although the Notch signaling pathway is known to play an important role in ovarian follicle development in mammals, whether it is involved in oocyte maturation remains unclear. Therefore, this study was performed to elucidate the existence and role of the Notch signaling pathway during oocyte maturation in a porcine model. Methods: Reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemical assays were used to determine the existence of Notch signaling pathway-related transcripts and proteins in porcine cumulus–oocyte complexes (COCs). In vitro maturation (IVM) and parthenogenetic activation of oocytes were employed to examine the effects of Notch signaling inhibition on meiotic progression and embryogenesis of COCs using RO4929097 (RO), an inhibitor of γ secretase. Various staining methods (TUNEL, Phalloidin-TRITC, MitoTracker, JC-1, BODIPY FL ATP, ER-Tracker, Fluo-3, and Rhod-2) and immunocytochemical and quantitative PCR assays were used to identify the effects of Notch signaling inhibition on meiotic progression, embryogenesis, cell cycle progression, spindle assembly, chromosome alignment, mitochondrial and endoplasmic reticulum distribution, and downstream pathway targets in COCs. Results: The RT-PCR and immunocytochemical analyses revealed the presence of Notch signaling-related receptors (NOTCH1–4) and ligands (JAG1 and 2 and DLL1, 3, and 4) at 0, 22, 28, and 44 h of IVM in the COCs. RO treatment during oocyte maturation markedly reduced meiotic maturation and embryogenesis, inhibiting the cell cycle progression, spindle assembly, and chromosome alignment processes that are important for meiotic maturation. Furthermore, RO significantly impaired the cellular distribution and functions of the mitochondria and endoplasmic reticula, which are important organelles for the cytoplasmic maturation of oocytes. Finally, the involvement of canonical Notch signaling in oocyte maturation was confirmed by the decreased expression of HES and HEY family transcripts and proteins in the RO-treated COCs. Conclusions: It was first demonstrated that Notch signaling pathway-related transcripts and proteins were expressed during the meiotic maturation of porcine COCs. Furthermore, the inhibition of Notch signaling during IVM revealed the essential role of this signaling pathway during oocyte maturation in pigs. [ABSTRACT FROM AUTHOR]

Objective To investigate the effects and mechanisms of melatonin (MT) on improving oocyte quality in mice exposed to benzophenone-3 (BP-3). Methods In this study, 6 ~ 12-week-old female ICR mice were cultured in vitro in M16 culture, 0.8 μmol/L BP-3 medium and 1 × 10−7 mol/L MT + 0.8 μmol/L BP-3 mixed culture. Female ICR mice were randomly segregated into three groups： control, BP-3, and BMT. The control group received 0.5 mL of purified water, the BP-3 group was administered 0.5 mL of a 0.8 μmol/L BP-3 solution, and the BMT group received 0.5 ml of a combination of 0.8 μmol/L BP-3 and 15 mg/kg MT solution via gavage once daily for four weeks, to facilitate in vivo experimentation. Subsequently, the oocyte maturity rate, transcription levels and protein expression levels of mitochondrial dynamics-related genes Mfn1, Opa1, Fis1 and Drp1, mitochondrial membrane potential and spindle morphology were detected in the three groups to explore the rescue effect of MT on the mitochondria of BP-3-exposed mice. Results Compared to the control group, MT treatment markedly enhanced the transcription and protein levels of the mitochondrial fusion genes Mfn1 and Opa1 in oocytes, while concurrently down-regulating the mRNA and protein levels of the mitochondrial fission genes Fis1 and Drp1. Additionally, the BMT group exhibited significantly lower levels of ROS and abnormal spindle morphology in their oocytes compared to the BP-3 group, yet their mitochondrial membrane potential was notably elevated. Conclusion Physiological concentration of BP-3 exposure was toxic for reproduction, but the addition of appropriate concentrations of MT could significantly improve the mitochondrial dynamics and developmental potential of oocytes in BP-3-exposed mice. [ABSTRACT FROM AUTHOR]

Objective: Methylenetetrahydrofolatereductase (MTHFR) is important for folate metabolism, which is involved in DNA synthesis and cell growth. However, the relationship between Maternal MTHFR polymorphisms and outcomes in assisted reproduction remains controversial. This is the first study to explore the effect of MTHFR polymorphisms on the embryological outcomes in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles in Korean patients with infertility. Materials and methods: This retrospective cohort study included 173 women who underwent MTHFR genotyping between July, 2021 and June, 2022. The embryologic outcomes of 301 IVF/ICSI cycles were compared between groups according to MTHFR polymorphisms using ANOVA and Chi-square test. Results: Oocyte maturation rates were 80.0%, 75.0%, and 71.4% for MTHFR 677CC, 677CT, and 677TT, respectively. Cleaved embryo formation and transplantable embryo rates were comparable across various maternal MTHFR 677 genotypes. Good-quality embryo (GQE) rate was higher for MTHFR 677CT than those for 677CC and 677TT (40.0% vs. 29.4%, p = 0.001 and 40.0% vs. 33.3%, p = 0.025, respectively). When analyzing the combined MTHFR genotypes, the oocyte maturation rate was significantly lower in 677TT than in 677CC 1298AA/677CC 1298AC and 677CC 1298CC/677CT 1298AA/677CT 1298AC (71.4% vs. 76.7%, p = 0.012 and 71.4% vs. 75.7%, p = 0.029, respectively). The MTHFR 677CC/1298CC, 677CT/1298AA, and 677CT/1298AC genotypes had the highest GQE rates. Conclusions: MTHFR 677TT genotype, which had the lowest enzymatic activity, had the lowest oocyte maturation rate. The combined MTHFR 677CC/1298CC, 677CT/1298AA, and 677CT/1298AC genotypes with intermediate enzyme activities had higher GQE rates. However, no differences were observed in the transplantable embryo rate between MTHFR genotypes. [ABSTRACT FROM AUTHOR]

Background: N6‐methyladenosine (m6A) modification is a widespread and reversible epigenetic alteration in eukaryotic mRNA, playing a pivotal role in various biological functions. Its significance in female reproductive development and associated diseases has recently become a focal point of research. Objective: This review aims to consolidate current knowledge of the role of m6A modification in female reproductive tissues, emphasizing its regulatory dynamics, functional significance, and implications in reproductive health and disease. Methods: A comprehensive analysis of recent studies focusing on m6A modification in ovarian development, oocyte maturation, embryo development, and the pathogenesis of reproductive diseases. Results: m6A modification exhibits dynamic regulation in female reproductive tissues, influencing key developmental stages and processes. It plays critical roles in ovarian development, oocyte maturation, and embryo development, underpinning essential aspects of reproductive health. m6A modification is intricately involved in the pathogenesis of several reproductive diseases, including polycystic ovary syndrome (PCOS), premature ovarian failure (POF), and endometriosis, offering insights into potential molecular mechanisms and therapeutic targets. Conclusion: The review highlights the crucial role of m6A modification in female reproductive development and related diseases. It underscores the need for further research to explore innovative diagnostic and therapeutic strategies for reproductive disorders, leveraging the insights gained from understanding m6A modification's impact on reproductive health. [ABSTRACT FROM AUTHOR]

Genetic anomalies in oocyte maturation present significant fertility and embryonic development challenges. This review explores the intricate mechanisms of nuclear and cytoplasmic maturation, emphasizing the genetic and molecular factors contributing to oocyte quality and competence. Chromosomal mutations, errors in segregation, genetic mutations in signaling pathways and meiosis-related genes, and epigenetic alterations are discussed as critical contributors to oocyte maturation defects. The role of mitochondrial defects, maternal mRNA dysregulation, and critical proteins such as NLRP14 and BMP6 are highlighted. Understanding these genetic factors is crucial for improving diagnostic approaches and therapeutic interventions in reproductive medicine, particularly for couples encountering recurrent in vitro fertilization failures. This review will explore how specific genetic mutations impact fertility treatments and reproductive success by examining the intricate oocyte maturation process. We will focus on genetic abnormalities that may disrupt the oocyte maturation pathway, discussing the underlying mechanisms involved and considering their potential clinical implications for enhancing fertility outcomes. [ABSTRACT FROM AUTHOR]

Objective: Cumulus cells respond to the effects of hormones and signalling molecules synthesised by the oocyte by changing their expression profile. In turn, cumulus cells control the growth and maturation of the oocyte. Therefore, analysis of the transcriptional profile of cumulus cells is likely to be one of the approaches for non-invasive prediction of oocyte quality in assisted reproductive technology programs. To evaluate the expression of selected genes in cumulus cells in women with primary and secondary types of infertility with positive and negative results of assisted reproductive technologies. Methods: 9 healthy donors and 19 patients undergoing infertility treatment with ART methods participated in the study. RNA was isolated from cumulus cells obtained during oocyte preparation for fertilisation, and cDNA was synthesised and used as a matrix for real-time PCR with primers for AREG, SCD4, PTGS, SCD5, HAS2, VCAN, STAR and two lncRNA genes (ANXA2P2, MALAT1). Results and Discussion: The genes of interest expression did not depend on the type of infertility but rather on the IVF attempt outcome. The panel of mRNA biomarkers (SDC4upAREGupMALAT1not changedANXA2P2not changed) was associated with poorer oocyte competence prognosis and SDC4not changedAREGdownMALAT1downANXA2P2down set of biomarkers was associated with better quality of oocytes. Conclusions: This non-invasive method can be used to access oocyte quality in patients with primary and secondary infertility. [ABSTRACT FROM AUTHOR]

Abstract Purpose Previous studies have suggested a link between serum progesterone levels on the day of the HCG trigger in IVF cycles and oocyte and embryo quality. This study aims to explore this relationship more thoroughly. Methods This study included 496 infertility patients at Moloud Infertility Treatment Center, Zahedan, Iran. Statistical methods were used to assess factors such as oocyte maturation and embryo quality, fertilization rate, BMI, and gonadotropin dosage. Results While an initial progesterone cutoff of 1.2 ng/ml was used to perform fundamental analysis, a more accurate cutoff of 1.54 ng/ml was identified, beyond which the average number of M1 oocytes significantly declined. A strong relationship was found between higher progesterone levels and a greater number of retrieved oocytes (p = 0.004), with M1 oocytes showing a similar relation. Also, BMI was significantly related to the quality of eight-cell grade B embryos (p = 0.006). However, no significant correlations were found between progesterone levels and other factors, including patient age (p = 0.327), fertilization rate (p = 0.603), or embryo quality at other stages. Conclusions The findings demonstrate that elevated progesterone level, particularly beyond the identified cutoff of 1.54 ng/ml, is a valuable clinical indicator of suboptimal IVF outcomes due to its negative impact on oocyte maturation.

Objective(s): To investigate the impact of Pentoxifylline (PTX) on the in vitro maturation (IVM) of mouse oocytes and its effect on oocyte quality. Materials and Methods: This experimental study involved culturing mouse oocytes in an IVM medium with varying PTX concentrations (0-100 µM). Post-culture, oocytes were assessed for nuclear and cytoplasmic maturation and quality indicators, including germinal vesicle breakdown (GVBD), first polar body extrusion (PB1E), cortical granules (CGs) distribution, spindle structure, chromosome alignment, and intracellular reactive oxygen species (ROS) levels. Results: Treatment with PTX at 10, 25, and 50 µM concentrations significantly enhanced the nuclear maturation rates of oocytes. The optimal concentration was found to be 10 µM, as it resulted in the most favorable cytoplasmic maturation, characterized by improved distribution of CGs, spindle structure, and chromosome alignment. Additionally, treatment with 10 µM PTX effectively reduced reactive oxygen species (ROS) levels. Conclusion: PTX supplementation at specific concentrations enhances mouse oocyte maturation and quality, potentially by facilitating CG distribution, spindle integrity, and chromosome alignment and by reducing ROS production. [ABSTRACT FROM AUTHOR]

Abstract Obesity has reached epidemic proportions in most parts of the world, and it is estimated that 1 billion people globally are trapped in an obesity pandemic, which has seriously compromised human health. Recently, there has been a flood of research into obesity as well as redox and lipid metabolism; however, our understanding of the pathways and specific molecular mechanisms by which obesity‐induced oxidative stress affects female reproductive function remains limited. In this review, we discuss how the obesity pandemic has led to lower female fertility. We focus on multiple facets of obesity‐mediated reproductive dysfunction, including follicular atresia, oocyte maturation, embryo implantation, reproductive aging, and discuss therapeutic interventions that have the potential to normalize reproductive function in obese females, such as targeting mitochondrial lipid metabolism and antioxidant pathways.

Abstract Background Oocytes, the largest cells in mammals, harbor numerous mitochondria within their cytoplasm. These highly dynamic organelles are crucial for providing energy resources and serving as central regulators during oogenesis. Mitochondrial dynamics ensure proper energy distribution for various cellular processes involved in oocyte maturation. Previous studies have used alterations in mitochondrial distribution as a biomarker to assess the oocyte health. However, there are discrepancies between studies regarding mitochondrial distribution profiles in healthy oocytes. Consequently, a comprehensive mitochondrial distribution profile in oocytes during maturation has not been fully characterized. Additionally, there is a lack of objective, quantitative methods to evaluate alterations in mitochondrial distribution profiles in oocytes. Methods This study aims to provide an in-depth overview of mitochondrial distribution profiles in mouse oocytes at different maturation stages: germinal vesicle (GV) stage, metaphase I (MI), and mature metaphase II (MII). Freshly collected mouse GV, MI and MII oocytes were stained with MitoTracker Red. Confocal microscopy was used to obtain images of mitochondrial distribution profiles in these oocytes. Using the Imaris software, we reconstructed three-dimensional (3D) surface renderings of each oocyte and quantitatively illustrated the mitochondrial distribution profiles. Results At the GV stage, mitochondria in oocytes were evenly distributed throughout the ooplasm. As oocytes progressed to MI and MII stages, mitochondria aggregated and formed clusters, the mean size of mitochondrial clusters and the proportions of clustered mitochondria increased along with the maturation of oocytes. Conclusions Our findings reveal that mitochondria in mouse oocytes are highly dynamic, undergoing significant reorganizations during oocyte maturation. We for the first time provided comprehensive mitochondrial distribution profiles in mouse oocytes at the GV, MI and MII stages. These mitochondrial distribution profiles were further quantitatively evaluated. Our methods provide an objective and standardized approach for evaluating alterations in mitochondrial dynamics, which can be used as biomarkers to monitor oocyte conditions during maturation.

The elucidation of oocyte maturation mechanisms is paramount for advancing embryo development within the scope of assisted reproductive technologies (ART). Both cytoplasmic and nuclear maturation represent intricate processes governed by tightly regulated cellular pathways, which are essential for ensuring the oocyte's competence for fertilization and subsequent embryogenesis. A comprehensive grasp of these mechanisms is vital, as the maturation stage of the oocyte significantly influences chromosomal integrity, spindle formation, and its ability to support the initial stages of embryonic development. By leveraging this knowledge, we can enhance in vitro fertilization (IVF) protocols, refining ovarian stimulation regimens and culture conditions to improve oocyte quality. This, in turn, has the potential to boost pregnancy rates and outcomes. Further research in this area will contribute to the development of novel interventions that aim to increase the efficacy of preimplantation embryonic development, offering new opportunities for individuals undergoing fertility treatments. [ABSTRACT FROM AUTHOR]

BACKGROUND Bisphenol A (BPA) is an endocrine disrupting chemical released from plastic materials, including food packaging and dental sealants, persisting in the environment and ubiquitously contaminating ecosystems and human populations. BPA can elicit an array of damaging health effects and, alarmingly, 'BPA-free' alternatives mirror these harmful effects. Bisphenol exposure can negatively impact female fertility, damaging both the ovary and oocytes therein. Such damage can diminish reproductive capacity, pregnancy success, and offspring health. Despite global government regulations in place to indicate 'safe' BPA exposure levels, these policies have not considered the effects of bisphenols on oocyte health. OBJECTIVE AND RATIONALE This scoping review was conducted to evaluate evidence on the effects of BPA and BPA alternatives on standardized parameters of oocyte health. In doing so, this review addresses a critical gap in the literature providing a comprehensive, up-to-date synthesis of the effects of bisphenols on oocyte health. SEARCH METHODS This scoping review was conducted in accordance with PRISMA guidelines. Four databases, Medline, Embase, Scopus, and Web of Science, were searched twice (23 February 2022 and 1 August 2023) to capture studies assessing mammalian oocyte health post-bisphenol exposure. Search terms regarding oocytes, ovarian follicles, and bisphenols were utilized to identify relevant studies. Manuscripts written in English and reporting the effect of any bisphenol on mammalian oocyte health from all years were included. Parameters for toxicological studies were evaluated, including the number of bisphenol concentrations/doses tested, dosing regimen, biological replicates and/or animal numbers, and statistical information (for human studies). Standardized parameters of oocyte health including follicle counts, oocyte yield, oocyte meiotic capacity, morphology of oocyte and cumulus cells, and oocyte meiotic spindle integrity were extracted across the studies. OUTCOMES After screening 3147 studies, 107 studies of either humans or mammalian animal models or humans were included. Of the in vitro exposure studies, 96.3% (26/27) and 94.1% (16/17) found at least one adverse effect on oocyte health using BPA or BPA alternatives (including BHPF, BPAF, BPB, BPF, and BPS), respectively. These included increased meiotic cell cycle arrest, altered morphology, and abnormal meiotic spindle/chromosomal alignment. In vivo , 85.7% (30/35) of studies on BPA and 92.3% (12/13) on BPA alternatives documented adverse effects on follicle development, morphology, or spindle/chromosome alignment. Importantly, these effects were recorded using levels below those deemed 'safe' for human exposure. Over half (11/21) of all human observational studies showed associations between higher urinary BPA levels and reduced antral follicle counts or oocyte yield in IVF patients. Recommendations are presented based on the identified shortcomings of the current evidence, incorporating elements of FDA requirements for future research in the field. WIDER IMPLICATIONS These data highlight the detrimental impacts of low-level BPA and BPA alternative exposure, contributing to poor oocyte quality and reduced fertility. These outcomes are valuable in promoting the revision of current policies and guidelines pertaining to BPA exposure internationally. This study serves as a valuable resource to scientists, providing key recommendations on study design, reporting elements, and endpoint measures to strengthen future studies. Ultimately, this review highlights oocyte health as a fundamentally important endpoint in reproductive toxicological studies, indicating an important direction for future research into endocrine disrupting chemicals to improve fertility outcomes. [ABSTRACT FROM AUTHOR]

Estrogen is a steroid hormone that plays a key role in regulating many physiological processes, such as follicle activation and development and oocyte maturation in mammals. Ca2+ is crucial in oogenesis, oocyte maturation, ovulation, and fertilization. However, the mechanism by which estrogen regulates Ca2+ during oocyte maturation in mice has not been reported. This study revealed that Ca2+ levels in oocytes significantly increase during the 4–12 h period in vitro. Oocytes treated with 0.1 µM estrogen and 1 µM G1, a G-protein-coupled estrogen receptor (GPER) agonist, showed significantly increased Ca2+ levels, while treatment with 1 µM G15, an antagonist of GPER, significantly decreased Ca2+ levels. Notably, estrogen regulates Ca2+ in oocytes through the GPER pathway and promotes the expression of the Ca2+-producing protein EPAC1. In addition, estrogen alleviates the inhibitory effect of the Ca2+ chelator BAPTA-AM during oocyte maturation by promoting Ca2+ production. Furthermore, estrogen can promote the expression of the mitochondrial generation-associated protein SIRT1 through the GPER pathway, alleviate mitochondrial oxidative damage caused by BAPTA-AM, and restore the mitochondrial membrane potential level. Collectively, this study demonstrates that estrogen can regulate Ca2+ through the GPER-EPAC1 pathway and promote the expression of SIRT1, which promotes oocyte mitochondrial function during oocyte maturation. [ABSTRACT FROM AUTHOR]

Endoplasmic reticulum (ER) stress interferes with developmental processes in oocyte maturation and embryo development. In vitro growth (IVG) is associated with low developmental competence, and ER stress during IVG culture may play a role. Therefore, this study aimed to examine the effect of tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, on the IVG of bovine oocytes to understand the role of ER stress. Oocyte-granulosa cell complexes (OGCs) were collected from early antral follicles (1.5–1.8 mm) and allowed to grow in vitro for 5 days at 38.5 °C in a humidified atmosphere containing 5 % CO 2. Basic growth culture medium was supplemented with TUDCA at various concentrations (0, 50, 100, 250, and 500 μM). After IVG, oocyte diameters were similar among groups, but the antrum formation rate tended to be higher in the TUDCA 100 μM group. The mRNA expression levels of ER stress-associated genes (PERK , ATF6 , ATF4 , CHOP , BAX , IRE1 , and XBP1) in OGCs were downregulated in the TUDCA 100 μM group than those in the control group. Moreover, the TUDCA 100 μM group exhibited reduced ROS production with higher GSH levels and improved in vitro -grown oocyte maturation compared with those in the control group. In contrast, no difference in the developmental competence of embryos following in vitro fertilization was observed between the control and TUDCA 100 μM groups. These results indicate that ER stress could impair IVG and subsequent maturation rate of bovine oocytes, and TUDCA could alleviate these detrimental effects. These outcomes might improve the quality of oocytes in IVG culture in assisted reproductive technology. • ER stress could impair oocyte development during in vitro (IVG) growth. • ER stress attenuation by TUDCA promotes antrum formation during in vitro growth. • TUDCA downregulates ER stress-associated gene expression in IVG. • TUDCA suppresses oxidative stress and improves subsequent maturation of IVG-grown oocytes. [ABSTRACT FROM AUTHOR]

Maternal cadmium exposure during pregnancy has been demonstrated to have detrimental effects on offspring development. However, the impact of maternal cadmium exposure on offspring oocytes remains largely unknown, and the underlying mechanisms are not fully understood. In this study, we found that maternal cadmium exposure during pregnancy resulted in selective alteration in epigenetic modifications of mouse oocytes in offspring, including a decrease in H3K4me2 and H4K12ac, as well as an increase in DNA methylation of H19. Although ROS levels and mitochondrial activity remain at normal levels, the DNA damage marker γH2AX was significantly increased and the DNA repair marker DNA-PKcs was remarkably decreased in offspring oocytes from maternal cadmium exposure. These alterations are responsible for the decrease in the quality of mouse oocytes in offspring induced by maternal cadmium exposure. As a result, the meiotic maturation of oocytes and subsequent early embryonic development are influenced by maternal cadmium exposure. RNA-seq results showed that maternal cadmium exposure elicits modifications in the expression of genes associated with metabolism, signal transduction, and endocrine regulation in offspring ovaries, which also contribute to the disorders of oocyte maturation and failures in early embryonic development. Our research provides direct evidence of transgenerational epigenetic inheritance of cadmium reproductive toxicity in mouse germ cells. [ABSTRACT FROM AUTHOR]

Background: Oocytes, the largest cells in mammals, harbor numerous mitochondria within their cytoplasm. These highly dynamic organelles are crucial for providing energy resources and serving as central regulators during oogenesis. Mitochondrial dynamics ensure proper energy distribution for various cellular processes involved in oocyte maturation. Previous studies have used alterations in mitochondrial distribution as a biomarker to assess the oocyte health. However, there are discrepancies between studies regarding mitochondrial distribution profiles in healthy oocytes. Consequently, a comprehensive mitochondrial distribution profile in oocytes during maturation has not been fully characterized. Additionally, there is a lack of objective, quantitative methods to evaluate alterations in mitochondrial distribution profiles in oocytes. Methods: This study aims to provide an in-depth overview of mitochondrial distribution profiles in mouse oocytes at different maturation stages: germinal vesicle (GV) stage, metaphase I (MI), and mature metaphase II (MII). Freshly collected mouse GV, MI and MII oocytes were stained with MitoTracker Red. Confocal microscopy was used to obtain images of mitochondrial distribution profiles in these oocytes. Using the Imaris software, we reconstructed three-dimensional (3D) surface renderings of each oocyte and quantitatively illustrated the mitochondrial distribution profiles. Results: At the GV stage, mitochondria in oocytes were evenly distributed throughout the ooplasm. As oocytes progressed to MI and MII stages, mitochondria aggregated and formed clusters, the mean size of mitochondrial clusters and the proportions of clustered mitochondria increased along with the maturation of oocytes. Conclusions: Our findings reveal that mitochondria in mouse oocytes are highly dynamic, undergoing significant reorganizations during oocyte maturation. We for the first time provided comprehensive mitochondrial distribution profiles in mouse oocytes at the GV, MI and MII stages. These mitochondrial distribution profiles were further quantitatively evaluated. Our methods provide an objective and standardized approach for evaluating alterations in mitochondrial dynamics, which can be used as biomarkers to monitor oocyte conditions during maturation. [ABSTRACT FROM AUTHOR]

The cytoplasmic lattices (CPLs) are fibrous structures of the mammalian oocyte cytoplasm that are needed to store ribosomes and maternal proteins in insoluble form to prevent their degradation, activation, and nuclear transfer. UHRF1 and the members of the subcortical maternal complex colocalize with the CPLs, and their deficiency results in lattice impairment. Mutations in the maternal effect genes Nlrp14 and Padi6 cause maturation defects and CPL deficiency in mouse oocytes, leading to lack of the CPL storage function and impaired cytoplasmic UHRF1 abundance, abnormal nuclear localization of DNMT1, and failure of epigenetic reprogramming, as well as defective zygotic genome activation and embryo development beyond the two-cell stage. Mouse mutants of CPL-associated proteins do not mimic human imprinting defects, suggesting species-specific differences. Oocyte maturation and preimplantation embryo development are critical to successful pregnancy outcomes and the correct establishment and maintenance of genomic imprinting. Thanks to novel technologies and omics studies in human patients and mouse models, the importance of the proteins associated with the cytoplasmic lattices (CPLs), highly abundant structures found in the cytoplasm of mammalian oocytes and preimplantation embryos, in the maternal to zygotic transition is becoming increasingly evident. This review highlights the recent discoveries on the role of these proteins in protein storage and other oocyte cytoplasmic processes, epigenetic reprogramming, and zygotic genome activation (ZGA). A better comprehension of these events may significantly improve clinical diagnosis and pave the way for targeted interventions aiming to correct or mitigate female fertility issues and genomic imprinting disorders. [ABSTRACT FROM AUTHOR]

Poor ovarian response (POR) patients often face the risk of not having enough competent oocytes. Then, aspirating small follicles could serve as a strategy to increase their number. Many efforts have been addressed to associate follicular size with oocyte competence, but results are controversial. Therefore, our study aimed to evaluate oocyte maturation and developmental competence, along with a non-invasive oocyte-maturation-related miRNA signature in oocytes retrieved from both large and small follicles. A total of 178 follicles, from 31 POR patients, were aspirated and measured on the day of ovarian puncture. Follicular diameters, oocyte collection, oocyte maturation, fertilization, blastocysts, and good-quality blastocyst rates were recorded. Simultaneously, follicular fluids were collected to quantify their miRNA expression. The efficacy of oocyte retrieval along with oocyte maturation, fertilization, and blastulation rates tended to increase with follicular size, but few significant differences were found. Despite there being significantly more collected oocytes from follicles > 11.5 mm compared to follicles ≤ 11.5 mm (p < 0.05), oocytes from the latter were also mature, with no significant differences in the miRNA signature, but only those > 13.5 mm demonstrated developmental competence. In conclusion, 11.5 mm follicles can produce mature oocytes, but only those larger than 13.5 mm yielded transferable embryos. [ABSTRACT FROM AUTHOR]

Introduction: Over the recent years, scientific community has increased its interest on solving problems of female fertility pathology. Many factors acting separately or in combination affect significantly the reproductive life of a woman. This review summarizes current evidence regarding the direct and/or indirect action of environmental factors and endocrine disrupting chemicals (EDCs; i.e. heavy metals, plasticizers, parabens, industrial chemicals, pesticides, or medications, by-products, anti-bacterial agents, perfluorochemicals) upon assisted and non-assisted female fertility, extracted from in vivo and in vitro animal and human published data. Transgenerational effects which could have been caused epigenetically by the action of EDCs have been raised. Methods: This narrative review englobes and describes data from in vitro and in vivo animal and human studies with regard to the action of environmental factors, which include EDCs, on female fertility following the questions for narrative reviews of the SANRA (a scale for the quality assessment of narrative review articles). The identification of the studies was done: through the PubMed Central and the PubMed of the MEDLINE, the Google Scholar database and the Cochrane Library database until December 2023 combining appropriate keywords ("specific environmental factors" including "EDCs" AND "specific negative fertility outcomes"); by manual scanning of references from selected articles and reviews focusing on these subjects. It includes references to EDCs-induced transgenerational effects. Results: From the reported evidence emerge negative or positive associations between specific environmental factors or EDCs and infertility outcomes such as infertility indices, disrupted maturation of the oocytes, anovulation, deranged transportation of the embryo and failure of implantation. Conclusion: The revealed adverse outcomes related to female fertility could be attributed to exposure to specific environmental factors such as temperature, climate, radiation, air pollutants, nutrition, toxic substances and EDCs. The recognition of fertility hazards related to the environment will permit the limitation of exposure to them, will improve female fertility and protect the health potential of future generations. [ABSTRACT FROM AUTHOR]

Decreased oocyte quality is a significant contributor to the decline in female fertility that accompanies aging in mammals. Oocytes rely on mRNA stores to support their survival and integrity during the protracted period of transcriptional dormancy as they await ovulation. However, the changes in mRNA levels and interactions that occur during porcine oocyte maturation and aging remain unclear. In this study, the mRNA expression profiles of porcine oocytes during the GV, MII, and aging (24 h after the MII stage) stages were explored by transcriptome sequencing to identify the key genes and pathways that affect oocyte maturation and postovulatory aging. The results showed that 10,929 genes were coexpressed in porcine oocytes during the GV stage, MII stage, and aging stage. In addition, 3037 genes were expressed only in the GV stage, 535 genes were expressed only in the MII stage, and 120 genes were expressed only in the aging stage. The correlation index between the GV and MII stages (0.535) was markedly lower than that between the MII and aging stages (0.942). A total of 3237 genes, which included 1408 upregulated and 1829 downregulated genes, were differentially expressed during porcine oocyte postovulatory aging (aging stage vs. MII stage). Key functional genes, including ATP2A1 , ATP2A3 , ATP2B2 , NDUFS1 , NDUFA2 , NDUFAF3 , SREBF1 , CYP11A1 , CYP3A29 , GPx4 , CCP110 , STMN1 , SPC25 , Sirt2 , SYCP3 , Fascin1/2 , PFN1 , Cofilin , Tmod3 , FLNA , LRKK2 , CHEK1/2 , DDB1/2 , DDIT4L , and TONSL , and key molecular pathways, such as the calcium signaling pathway, MAPK signaling pathway, TGF-β signaling pathway, PI3K/Akt signaling pathway, FoxO signaling pathway, gap junctions, and thermogenesis, were found in abundance during porcine postovulatory aging. These genes are mainly involved in the regulation of many biological processes, such as oxidative stress, calcium homeostasis, mitochondrial function, and lipid peroxidation, during porcine oocyte postovulatory aging. These results contribute to a more in-depth understanding of the biological changes, key regulatory genes and related biological pathways that are involved in oocyte aging and provide a theoretical basis for improving the efficiency of porcine embryo production in vitro and in vivo. • The biological activities of oocyte gradually weaken during postovulatory aging. • Redox homeostasis played crucial roles in oocyte postovulatory aging. • Calcium ion homeostasis played crucial roles in oocyte postovulatory aging. • Mitochondrial function played crucial roles in oocyte postovulatory aging. • Lipid metabolism played crucial roles in oocyte postovulatory aging. [ABSTRACT FROM AUTHOR]

Despite the cytotoxicity and embryotoxicity previously reported artesunate is a recommended drug to treat malaria for adults, children, and women in the first trimester of pregnancy. To address the putative effects of artesunate on female fertility and preimplantation embryo development, when the pregnancy is not detectable yet, artesunate was added to the oocyte in vitro maturation and in vitro embryo development of bovine. Briefly, in experiment 1 the cumulus-oocyte complexes (COCs) were in vitro matured for 18 h with 0.5, 1, or 2 µg/mL of artesunate or not (negative control) and then checked for nuclear maturation and subsequent embryo development. In experiment 2, the COCs were in vitro matured and fertilized without artesunate, which was added (0.5, 1, or 2 µg/mL) from the 1st to the 7th day of embryo culture along with a negative and a positive control group with doxorubicin. As a result, the use of artesunate on oocyte in vitro maturation did not differ from the negative control (p > 0.05) regarding nuclear maturation, cleavage, and blastocyst formation. Also, artesunate on in vitro embryo culture did not differ from negative control (p > 0.05) regarding cleavage and blastocyst formation, except for positive control, with doxorubicin (p < 0.05). In conclusion, under the conditions investigated, there was no evidence of artesunate toxicity on oocyte competence and the preimplantation period of in vitro embryo development in the bovine model, however, artesunate use still should be taken carefully as the outcome of implantation after oocytes and blastocysts exposure to artesunate remains unknown. HIGHLIGHTS: Artesunate added to in vitro maturation did not impair oocyte competence in bovine. Artesunate added to in vitro culture did not affect cleavage and blastocyst formation. No evidence of artesunate toxicity in oocytes and embryos of bovine was found. [ABSTRACT FROM AUTHOR]

Embryonic mortality in cattle is high, reaching 10–40 % in vivo and 60–70 % in vitro. Death of embryos involves reduced expression of genes related to embryonic viability, inhibition of DNA repair and increased DNA damage. In follicular granulosa cells, FGF18 from the theca layer increases apoptosis and DNA damage, so we hypothesized that FGF18 may also affect the oocyte and contribute to early embryonic death. The aims of this study were to identify the effects of FGF18 on cumulus expansion, oocyte maturation and embryo development from cleavage to blastocyst stage using a conventional bovine in vitro embryo production system using ovaries of abattoir origin. Addition of FGF18 during in-vitro maturation did not affect FSH-induced cumulus expansion or rates of nuclear maturation. When FGF18 was present in the culture system, rates of cleavage were not affected however, blastocyst and expanded blastocyst development was substantially inhibited (P < 0.05), indicating a delay of blastulation. The number of phosphorylated histone H2AFX foci per nucleus, a marker of DNA damage, was higher in cleavage-stage embryos cultured with FGF18 than in those from control group (P < 0.05). Furthermore, FGF18 decreased accumulation of PTGS2 and IFNT2 mRNA in blastocysts. In conclusion, these novel findings suggest that FGF18 plays a role in the regulation of embryonic death during the early stages of development by impairing DNA double-strand break repair and expression of genes associated with embryo viability and maternal recognition of pregnancy during the progression from oocyte to expanded blastocysts. • FGF18 had no effect on cumulus expansion, oocyte nuclear maturation, or embryo development from cleavage stage. • FGF18 added during IVM increased DNA double-strand breaks in cleavage-stage embryos. • FGF18 impaired development to the blastocyst and expanded blastocyst stages. • FGF18 added during embryo culture reduced abundance of PTGS2 mRNA, an embryo viability marker, and mRNA encoding IFNT2, a protein responsible for maternal recognition of pregnancy. [ABSTRACT FROM AUTHOR]

Simple Summary: Lampreys are a group of about 40 species found all over the world. One representative of this group is the river lamprey, which spends its larvae life initially in fresh water and then in the sea. For spawning, which is the end of their last migration, they return to fresh water. The spawning migration period lasts many months, during which the lampreys do not eat and many changes occur in their bodies. However, knowledge of these processes and their dynamics has not been studied and described, and this is the basis for preparing programs for the restitution of lampreys and their artificial reproduction under controlled conditions. This paper describes the changes occurring during spawning migration in female river lampreys, including the development of ovaries, changes in the liver, and atrophy of the digestive system. More than 40 species of lampreys (Petromyzontiformes) are known worldwide. Some of them are parasitic and feed on the blood of fish or other aquatic animals. Lampreys spawn once in their lifetime, after which they die. One of the representatives of the ichthyofauna of European rivers is the river lamprey, Lampetra fluviatilis. The river lamprey is now an endangered species due to loss and degradation of their habitats. The present study investigated gonadal development without hormonal stimulation in female river lampreys during puberty under controlled conditions for a period of seven months. Female river lampreys were kept in conditions that mimicked the natural environment. During the November–May period, samples were taken monthly to determine the extent of gonadal development and gastrointestinal and liver changes using histological examination. From the results obtained, the dynamical changes were determined for the following: gonadosomatic index (GSI; %), hepatosomatic index (his; %), and digestivesomatic index (DSI; %). With the gonadal development of female lampreys, an increase in GSI (7–23%; November–May) and a decrease in DSI (0.4–0.1%; November–May) histological changes were observed in the gonads (oocyte development), intestines (over time, decreased lipid vacuoles and enterocyte apoptosis), and in the liver (decreased lipid vacuoles and hepatocyte apoptosis over time) and in the digestive system resulting from its degradation. Also, it was observed that there was a change in the color of the liver to green in April. This study demonstrated the key role of the liver in the oocyte maturation process in this species. [ABSTRACT FROM AUTHOR]

G‐protein‐coupled receptor kinase 2 (GRK2) interacts with Gβγ and Gαq, subunits of G‐protein alpha, to regulate cell signalling. The second messenger inositol trisphosphate, produced by activated Gαq, promotes calcium release from the endoplasmic reticulum (ER) and regulates maturation‐promoting factor (MPF) activity. This study aimed to investigate the role of GRK2 in MPF activity during the meiotic maturation of porcine oocytes. A specific inhibitor of GRK2 (βi) was used in this study. The present study showed that GRK2 inhibition increased the percentage of oocyte arrest at the metaphase I (MI) stage (control: 13.84 ± 0.95%; βi: 31.30 ± 4.18%), which resulted in the reduction of the maturation rate (control: 80.36 ± 1.94%; βi: 65.40 ± 1.14%). The level of phospho‐GRK2 decreased in the treated group, suggesting that GRK2 activity was reduced upon GRK2 inhibition. Furthermore, the addition of βi decreased Ca2+ release from the ER. The protein levels of cyclin B and cyclin‐dependent kinase 1 were higher in the treatment group than those in the control group, indicating that GRK2 inhibition prevented a decrease in MPF activity. Collectively, GRK2 inhibition induced meiotic arrest at the MI stage in porcine oocytes by preventing a decrease in MPF activity, suggesting that GRK2 is essential for oocyte meiotic maturation in pigs. [ABSTRACT FROM AUTHOR]

Gellan gum (GG) is a soft, tractable, and natural polysaccharide substrate used for cell incubation. In this study, we examined the effects of GG on porcine oocyte maturation. Cumulus cells and oocyte complexes (COCs) were collected from slaughterhouse-derived porcine ovaries and cultured on plastic plates containing 0.05% or 0.1% GG gels. The 0.1% GG gel improved the maturation rate and quality of blastocysts, as determined by the total cell number and the rate of abnormally condensed nuclei. GG gels have antioxidant abilities and oocytes cultured on GG gels (0.05% and 0.1%) have reduced reactive oxygen species (ROS) content. Furthermore, GG gels (0.05% and 0.1%) increased F-actin formation, whereas treatment of oocytes with H2O2 reduced F-actin levels. GG gels increased the ATP content in oocytes but did not affect the mitochondrial DNA copy number or mitochondrial membrane potential. In addition, the medium cultured on 0.05% GG increased the glucose consumption of COCs. In conclusion, GG gel reduced ROS content, increased energy content, and improved subsequent embryonic development in pigs. [ABSTRACT FROM AUTHOR]

Abstract Background Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development. Methods PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level. Results The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence. Conclusions The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol.

Abstract Sphingosine‐1‐phosphate (S1P), a lipid messenger, propagates its signals by interacting with its intracellular targets or is transported to autocrine/paracrine to activate its cell surface receptors. In the female reproductive system, the homeostasis of S1P plays an important role in ovarian follicular development. Our recent studies show that S1P emerges as a functional mediator of LH‐EGFR signaling from cumulus cells to oocytes: elevating calcium levels in cumulus cells to induce oocyte meiotic maturation, and activating Akt/mTOR cascade reaction to promote oocyte developmental competence. Thus, S1P might be applied to promote oocyte maturation in animals and humans.

Background: Post-ovulatory aging (POA) of oocytes is related to a decrease in the quality and quantity of oocytes caused by aging. Previous studies on the characteristics of POA have investigated injury to early embryonic developmental ability, but no information is available on its effects on mitochondrial fission and mitophagy-related responses. In this study, we aimed to elucidate the molecular mechanisms underlying mitochondrial fission and mitophagy in in vitro maturation (IVM) oocytes and a POA model based on RNA sequencing analysis. Methods: The POA model was obtained through an additional 24 h culture following the IVM of matured oocytes. NMN treatment was administered at a concentration of 25 μM during the oocyte culture process. We conducted MitoTracker staining and Western blot experiments to confirm changes in mitochondrial function between the IVM and POA groups. Additionally, comparative transcriptome analysis was performed to identify differentially expressed genes and associated changes in mitochondrial dynamics between porcine IVM and POA model oocytes. Results: In total, 32 common genes of apoptosis and 42 mitochondrial fission and function uniquely expressed genes were detected (≥ 1.5-fold change) in POA and porcine metaphase II oocytes, respectively. Functional analyses of mitochondrial fission, oxidative stress, mitophagy, autophagy, and cellular apoptosis were observed as the major changes in regulated biological processes for oocyte quality and maturation ability compared with the POA model. Additionally, we revealed that the activation of NAD+ by nicotinamide mononucleotide not only partly improved oocyte quality but also mitochondrial fission and mitophagy activation in the POA porcine model. Conclusions: In summary, our data indicate that mitochondrial fission and function play roles in controlling oxidative stress, mitophagy, and apoptosis during maturation in POA porcine oocytes. Additionally, we found that NAD+ biosynthesis is an important pathway that mediates the effects of DRP1-derived mitochondrial morphology, dynamic balance, and mitophagy in the POA model.

Calcium (Ca2+) is a second messenger for many signal pathways, and changes in intracellular Ca2+ concentration ([Ca2+]i) are an important signaling mechanism in the oocyte maturation, activation, fertilization, function regulation of granulosa and cumulus cells and offspring development. Ca2+ oscillations occur during oocyte maturation and fertilization, which are maintained by Ca2+ stores and extracellular Ca2+ ([Ca2+]e). Abnormalities in Ca2+ signaling can affect the release of the first polar body, the first meiotic division, and chromosome and spindle morphology. Well-studied aspects of Ca2+ signaling in the oocyte are oocyte activation and fertilization. Oocyte activation, driven by sperm-specific phospholipase PLCz, is initiated by concerted intracellular patterns of Ca2+ release, termed Ca2+ oscillations. Ca2+ oscillations persist for a long time during fertilization and are coordinately engaged by a variety of Ca2+ channels, pumps, regulatory proteins and their partners. Calcium signaling also regulates granulosa and cumulus cells’ function, which further affects oocyte maturation and fertilization outcome. Clinically, there are several physical and chemical options for treating fertilization failure through oocyte activation. Additionally, various exogenous compounds or drugs can cause ovarian dysfunction and female infertility by inducing abnormal Ca2+ signaling or Ca2+ dyshomeostasis in oocytes and granulosa cells. Therefore, the reproductive health risks caused by adverse stresses should arouse our attention. This review will systematically summarize the latest research progress on the aforementioned aspects and propose further research directions on calcium signaling in female reproduction. [ABSTRACT FROM AUTHOR]

Promyelocytic leukemia (PML) nuclear bodies (PML-NBs) are core–shell-type membrane-less organelles typically found in the nucleus of mammalian somatic cells but are absent in mouse oocytes. Here, we deliberately induced the assembly of PML-NBs by injecting mRNA encoding human PML protein (hPML VI -sfGFP) into oocytes and investigated their impact on fertilization in which oocyte/embryos undergo multiple types of stresses. Following nuclear membrane breakdown, preassembled hPML VI -sfGFP mRNA-derived PML-NBs (hmdPML-NBs) persisted in the cytoplasm of oocytes, forming less-soluble debris, particularly under stress. Parthenogenetic embryos that successfully formed pronuclei were capable of removing preassembled hmdPML-NBs from the cytoplasm while forming new hmdPML-NBs in the pronucleus. These observations highlight the beneficial aspect of the PML-NB-free nucleoplasmic environment and suggest that the ability to eliminate unnecessary materials in the cytoplasm of metaphase oocytes serves as a potential indicator of the oocyte quality. [ABSTRACT FROM AUTHOR]

Improvement in vitro maturation culture conditions has been achieved by mimicking in vivo culture environments such as the follicular fluid. Acetic acid is an energy substrate that is abundantly present in the follicular fluid but has not been considered in vitro maturation. This study examined the effects of acetic acid on oocyte quality during nuclear maturation. Cumulus cells and oocyte complexes were collected from the porcine antral follicles of gilt ovaries and matured with 0, 0.1 or 1 mmol/L of acetic acid. After 44 h of in vitro maturation, the energy status, mitochondrial quality and function and embryonic developmental rate following parthenogenetic activation were determined. RNA-sequencing and protein expression analyses were conducted to predict the effects of acetic acid. Supplementation of the in vitro maturation medium with acetic acid (1 mmol/L) improved embryonic development. Oocytes matured with acetic acid had low adenosine triphosphate and lipid contents, mitochondrial membrane potential and reactive oxygen species levels. RNA-sequencing revealed differential expression of genes associated with the adenosine monophosphate-activated protein kinase signalling pathway. Immunostaining revealed that acetic acid increased the levels of phospho-adenosine monophosphate-activated protein kinase, phospho-acetyl-coenzyme A carboxylase, and sirtuin 1 and decreased those of fatty acid synthase and acetyl-coenzyme A synthetase 1. In summary, the use of acetic acid during oocyte maturation improved oocyte developmental ability and metabolism by altering mitochondrial activity and lipid metabolism. • Supplementation of acetic acid during in vitro maturation increases embryonic development in pigs. In brief: Despite its abundance in follicular fluid, acetic acid has not been considered in oocyte maturation. The present study demonstrated that acetic acid treatment during oocyte maturation improves embryonic development and induces metabolic changes. [ABSTRACT FROM AUTHOR]

Background: Assisted Reproductive Technologies (ARTs) have been validated in human and animal to solve reproductive problems such as infertility, aging, genetic selection/amplification and diseases. The persistent gap in ART biomedical applications lies in recapitulating the early stage of ovarian folliculogenesis, thus providing protocols to drive the large reserve of immature follicles towards the gonadotropin-dependent phase. Tissue engineering is becoming a concrete solution to potentially recapitulate ovarian structure, mostly relying on the use of autologous early follicles on natural or synthetic scaffolds. Based on these premises, the present study has been designed to validate the use of the ovarian bioinspired patterned electrospun fibrous scaffolds fabricated with poly(ε-caprolactone) (PCL) for multiple preantral (PA) follicle development. Methods: PA follicles isolated from lamb ovaries were cultured on PCL scaffold adopting a validated single-follicle protocol (Ctrl) or simulating a multiple-follicle condition by reproducing an artificial ovary engrafted with 5 or 10 PA (AO5PA and AO10PA). The incubations were protracted for 14 and 18 days before assessing scaffold-based microenvironment suitability to assist in vitro folliculogenesis (ivF) and oogenesis at morphological and functional level. Results: The ivF outcomes demonstrated that PCL-scaffolds generate an appropriate biomimetic ovarian microenvironment supporting the transition of multiple PA follicles towards early antral (EA) stage by supporting follicle growth and steroidogenic activation. PCL-multiple bioengineering ivF (AO10PA) performed in long term generated, in addition, the greatest percentage of highly specialized gametes by enhancing meiotic competence, large chromatin remodeling and parthenogenetic developmental competence. Conclusions: The study showcased the proof of concept for a next-generation ART use of PCL-patterned scaffold aimed to generate transplantable artificial ovary engrafted with autologous early-stage follicles or to advance ivF technologies holding a 3D bioinspired matrix promoting a physiological long-term multiple PA follicle protocol. [ABSTRACT FROM AUTHOR]

In animal assisted reproductive technology, the production of high-quality oocytes is crucial. The yak, having lived in the Qinghai-Tibet Plateau for an extended period, has reproductive cells that are regulated by hypoxia-inducible factor 1α (HIF-1α). This study aimed to investigate the impact of HIF-1α on yak oocyte maturation and early embryonic development in vitro through the regulation of autophagy. The in vitro maturation process of yak oocytes involved the addition of the HIF-1α inducer DFOM and the inhibitor LW6 to examine their effects on yak oocyte maturation, early embryonic development, cell autophagy, cytochrome P450s (CYP450s) enzyme expression, and cumulus diffusion factors. The findings revealed that DFOM significantly upregulated the expression of HIF-1α, resulting in increased the cumulus diffusion area, elevated first polar body expulsion rate of oocytes, enhanced mitochondrial and actin levels, decreased ROS production, and reduced early apoptosis levels of oocytes. Moreover, DFOM promoted the expression of autophagy-related proteins, CYP450s enzymes, and cumulus diffusion factors, thereby enhancing oocyte maturation and early embryonic development. Conversely, LW6 exhibited opposite effects. The inhibition of autophagy levels with 3-MA during DFOM treatment yielded similar outcomes. Furthermore, reducing autophagy led to increased apoptosis levels at all stages of early embryonic development, as well as a significant decrease in total cell number and ICM/TE ratio of blastocysts. Studies have shown that during the in vitro maturation of yak oocytes, HIF-1α can affect the cumulus expansion area of oocytes by regulating autophagy, the first polar body excretion rate, mitochondrial level, actin level, ROS and early apoptosis level, the CYP450s enzyme, and the expression of cumulus expansion factors, thereby improving the in vitro maturation and early embryonic development of yak oocytes. These findings offer valuable insights into the reproductive regulation mechanism of yaks in hypoxic environments and suggest potential strategies for the advancement of yak assisted reproductive technology. [ABSTRACT FROM AUTHOR]

Anti-Müllerian hormone (AMH) is a key paracrine/autocrine factor regulating folliculogenesis in the postnatal ovary. As antral follicles mature to the preovulatory stage, AMH production tends to be limited to cumulus cells. Therefore, the present study investigated the role of cumulus cell-derived AMH in supporting maturation and competence of the enclosed oocyte. Cumulus-oocyte complexes (COCs) were isolated from antral follicles of rhesus macaque ovaries for in vitro maturation with or without AMH depletion. Oocyte meiotic status and embryo cleavage after in vitro fertilization were assessed. In vitro maturation with AMH depletion was also performed using COCs from antral follicles of human ovarian tissue. Oocyte maturation and morphology were evaluated. The direct AMH action on mural granulosa cells of the preovulatory follicle was further assessed using human granulosa cells cultured with or without AMH supplementation. More macaque COCs produced metaphase II oocytes with AMH depletion than those of the control culture. However, preimplantation embryonic development after in vitro fertilization was comparable between oocytes derived from COCs cultured with AMH depletion and controls. Oocytes resumed meiosis in human COCs cultured with AMH depletion and exhibited a typical spindle structure. The confluency and cell number decreased in granulosa cells cultured with AMH supplementation relative to the control culture. AMH treatment did not induce cell death in cultured human granulosa cells. Data suggest that reduced AMH action in COCs could be beneficial for oocyte maturation. Cumulus cell-derived AMH is not essential for supporting oocyte competence or mural granulosa cell viability. [ABSTRACT FROM AUTHOR]