Oocyte aging underlies female reproductive aging: biological mechanisms and therapeutic strategies

HBimmCue: A Versatile Fluorescent Probe for Multi-Scale Imaging of Lipid Polarity and Membrane Order in Inner Mitochondrial Membrane

Mitochondrial membrane environmental dynamics are crucial for understanding function, yet high-resolution observation remains challenging. Here, HBimmCue is introduced as a fluorescent probe localized to inner mitochondrial membrane (IMM) that reports lipid polarity and membrane order changes, which correlate with cellular respiration levels. Using HBimmCue and fluorescence lifetime imaging microscopy (FLIM), IMM lipid heterogeneity is uncovered across scales, from nanoscale structures within individual mitochondria to mouse pre-implantation embryos. At the sub-organelle level, stimulated emission depletion (STED)-FLIM imaging highlights nanoscale polarity variations within the IMM. At the sub-cellular and cellular level, reduced IMM lipid polarity is observed in damaged mitochondria marked for lysosomal degradation and distinct IMM lipid distributions are identified in neurons and disease models. Additionally, metabolic dysfunction associated with oocytes aging and metabolic reprogramming from zygote to blastocyst is detected. Together, the work demonstrates the broad applicability of HBimmCue, offering a new paradigm for investigating lipid polarity and respiration level at multiple scales.

Microtubule Integrity Is Associated with Mitochondrial Function and Quality of Murine Preimplantation Embryos

Poor embryo quality is a major cause of poor clinical outcomes in assisted reproductive medicine, and there are no currently available interventions that can improve embryo quality. Mitochondria dysfunction is linked to low-quality female gametes and zygotes. Previously, microtubule integrity was also associated with mitochondrial function in oocytes. In the present study, we investigated the effects of the microtubule stabilizers (MTS) Taxol and Epothilone D (EpD) and the microtubule disturber (MTD) vinorelbine on mouse preimplantation embryo quality and pregnancy outcome compared with non-treatment controls. We prepared young BDF1 mice (7~9 weeks old) and cultured preimplantation embryos with MTS or MTD. Mitochondrial functional activity and embryo development ratios including pregnancy ratios were then assessed. MTS-treated embryos showed significantly increased mitochondrial membrane potentials and motility. Blastocyst formation was significantly higher in MTS-treated embryos than in MTD-treated embryos. Especially, MTS-treated embryos exhibited higher hatched blastocyte formation than untreated embryos. The number of offspring was significantly higher in surrogate mice transplanted with MTS-treated embryos. These findings demonstrated that the treatment of mouse preimplantation embryos with Taxol or EpD increased embryo development competence, which was associated with increased mitochondrial functional activity. Consistently, delivery ratios were significantly higher after transplantation with MTS-treated embryos than after transplantation with untreated embryos. These findings suggest that MTS could be used to supplement in vitro culture media to promote the recovery of poor-quality embryos.

Urolithin A Protects Porcine Oocytes from Artificially Induced Oxidative Stress Damage to Enhance Oocyte Maturation and Subsequent Embryo Development

Both the livestock and biomedical fields require a large supply of high-quality mature oocytes. However, the in vitro maturation (IVM) process often leads to an accumulation of reactive oxygen species (ROS), which can cause defects in oocyte meiosis and embryo development, ultimately compromising oocyte quality. Urolithin A (UA), known for its antioxidant properties, has not been thoroughly investigated for its potential to mitigate the negative effects of oxidative stress during the in vitro culturing of oocytes, and its underlying mechanism is not well understood. In this study, an in vitro oxidative stress model was established using porcine oocytes treated with H2O2, followed by exposure to varying concentrations of UA. The results revealed that 30 μM UA significantly improved both the quality of oocyte culture and the developmental potential of the resulting embryos. UA was found to enhance oocyte autophagy, reduce oxidative stress-induced mitochondrial damage, and restore mitochondrial function. Additionally, it lowered ROS and DNA damage levels in the oocytes, maintained proper spindle/chromosome alignment and actin cytoskeleton structure, promoted nuclear maturation, prevented abnormal cortical granule distribution, and supported oocyte cytoplasmic maturation. As a result, UA alleviated oxidative stress-induced defects in oocyte maturation and cumulus cell expansion, thereby improving the developmental potential and quality of parthenogenetic embryos. After supplementation with UA, pig parthenogenetic embryo pluripotency-related genes (Nanog and Sox2) and antiapoptotic genes (Bcl2) were upregulated, while proapoptotic genes (Bax) were downregulated. In conclusion, this study suggests that adding UA during IVM can effectively mitigate the adverse effects of oxidative stress on porcine oocytes, presenting a promising strategy for enhancing their developmental potential in vitro.

Mitochondrial FIS1 level in cumulus cells correlates with morphological grades of human cleavage-stage embryos

PURPOSE

Advanced-age women have a lower good-quality embryo rate (GQER) compared to young women. However, GQER varies widely within the same age group, suggesting that factors beyond age influence embryo quality. Mitochondria regulate cellular metabolism through dynamic fission and fusion alterations. Specifically, cumulus cell (CC) mitochondria regulate not only the metabolism of CCs but also of adjacent oocytes. This study aims to investigate the relationship between CC mitochondrial dynamics and oocyte developmental potential post-fertilization.

METHODS

CCs were collected from 183 women aged 25-45 undergoing single sperm intracytoplasmic injection-embryo transfer treatments. Samples were stratified by age into young (< 35) and advanced age (≥ 35) groups. Each group was further subdivided into high and low subgroups based on day 3 GQER. Mitochondrial morphology, dynamics, fission-fusion gene expression, and mitochondrial functions were compared among groups and subgroups.

RESULTS

Consistent with the literature, data analysis from our laboratory revealed significant variances in GQER among individuals of the same age group. Morphological analysis suggested a negative correlation between GQER and mitochondrial length in CCs (P < 0.0001, r = - 0.38). Live-cell imaging showed that both fission and fusion frequencies of CC mitochondria in the advanced-age group were lower than those in the young group (P = 0.009, P = 0.01). Additionally, within the advanced-age group, CC mitochondria from the low GQER subgroup exhibited lower fission frequency and fission-fusion ratios compared to the high GQER subgroup (P = 0.04, P = 0.01). Consequently, GQER positively correlated with mitochondrial fission-fusion ratio in CCs (P = 0.01, r = 0.44). Notably, there were no significant differences in the expression of mitochondrial fusion-related proteins (OPA1, MFN1, and MFN2) between the advanced-age and young groups or among the subgroups. However, levels of fission proteins, including FIS1 and MFF, were significantly lower in the advanced-age group compared to the young group and in the low GQER subgroup compared to their high GQER counterparts. qPCR results further indicated that fis1 and mff mRNA levels in CCs were positively correlated with GQER (P < 0.0001, r = 0.55; P = 0.0025, r = 0.41). The CCs from the low GQER subgroup exhibit a higher level of mitochondrial dysfunction.

CONCLUSIONS

Mitochondrial morphology, fission-fusion balance, and fission-fusion gene expression in CCs influence early embryonic development, independent of age. Of these factors, the FIS1 level shows the most robust correlation with GQER.

Paralichthys olivaceus egg extract improves porcine oocyte quality by decreasing oxidative stress

This study aimed to assess the influence of Paralichthys olivaceus egg extract (POEE) treatment on the maturation and development of porcine oocytes subjected to oxidative stress during in vitro maturation (IVM). POEE, notably rich in vitamin B9 (folic acid [FA]), was assessed alongside FA for antioxidant activity across various concentrations. In the 650 ppm POEE (650 POEE) group, there was a significant rise in glutathione (GSH) levels and an improved developmental rate in porcine oocytes experiencing oxidative stress during IVM. Treatment with 0.3 FA exhibited substantial reduction in ROS activity. Both 650 POEE and 0.3 FA groups demonstrated inhibited abnormal spindle organization and chromosomal misalignment, with increased blastocyst formation and decreased apoptotic cells. Treatment with 650 POEE elevated mRNA expression of development-related genes (SOX2, NANOG, and POU5F1). In conclusion, POEE effectively mitigates oxidative stress, enhances embryonic quality, and improves developmental potential in porcine oocytes on IVM.

Inhibition of ferroptosis counteracts the advanced maternal age-induced oocyte deterioration

Ferroptosis, a recently discovered form of programmed cell death triggered by the excessive accumulation of iron-dependent lipid peroxidation products, plays a critical role in the development of various diseases. However, whether it is involved in the age-related decline in oocyte quality remains unexplored. Here, we took advantage of nano-proteomics to uncover that reduced ferritin heavy chain (Fth1) level is a major cause leading to the occurrence of ferroptosis in aged oocytes. Specifically, induction of ferroptosis in young oocytes by its activators RSL3 and FAC, or knockdown of Fth1 all phenocopied the meiotic defects observed in aged oocytes, including failed oocyte meiotic maturation, aberrant cytoskeleton dynamics, as well as impaired mitochondrial function. Transcriptome analysis showed that knockdown of Fth1 affected meiosis-related and aging-related pathways in oocytes. Conversely, inhibition of ferroptosis by its inhibitors or expression of Fth1 improved the quality of aged oocytes. We also validated the effects of ferroptosis on the porcine oocyte quality in vitro. Altogether, we demonstrate the contribution of ferroptosis to the age-induced oocyte defects and evidence that inhibition of ferroptosis might be a feasible strategy to ameliorate the reproductive outcomes of female animals at an advanced age.

Diminished ovarian reserve is associated to euploidy rate: a single center study

Background

Reproductive success shows a well-documented decline with advancing maternal age, primarily due to chromosomal abnormalities (aneuploidies) in embryos. While ovarian reserve markers such as Anti-Müllerian Hormone (AMH) and Antral Follicle Count (AFC) traditionally serve as quantitative predictors of fertility, emerging evidence suggests they may also reflect oocyte quality, particularly in patients with Diminished Ovarian Reserve (DOR). The relationship between these biomarkers and embryo chromosomal status remains complex and poorly understood.

Methods

We conducted a retrospective analysis of in vitro fertilization (IVF) cycles performed between 2015 and 2022, involving 773 female patients who underwent IVF and pre-implantation genetic screening for aneuploidy (PGT-A). Our patient cohort was divided into two groups: Group 1, consisting of women who achieved at least one euploid embryo, and Group 2, comprising women who did not.

Results

The main outcome measures included the rate and number of euploid blastocysts and their correlation with ovarian reserve. Our results showed a statistically significant association between independent variables and embryo ploidy: AMH levels (OR 1.09; 95% CI 1.04-1.14, p<0.001), the age of the woman (OR 0.82; 95% CI 0.79-0.85, p<0.001), the number of oocytes retrieved (OR 1.050; 95% CI 1.01-1.08, p=0.05), and the fertilization rate (OR 6.69; 95% CI 2.67-16.77, p<0.001).

Conclusion

Our findings suggest that AMH levels are associated with embryo ploidy rate. These insights could enhance counseling practices in assisted reproductive technology (ART), offering patients a more detailed understanding of their infertility prognosis and the factors influencing IVF outcomes.

Culture media with antioxidants improved preimplantation embryo development and clinical outcomes of patients of advanced age

RESEARCH QUESTION

What are the clinical effects of using culture media supplemented with antioxidants (AOX) throughout the IVF process?

DESIGN

Prospective randomized single-centre study. Cumulus-oocyte complexes and semen samples collected from 127 treatment cycles were divided evenly between the study arm (culture media with AOX) and the control arm (culture media without AOX). The primary endpoint was the good-quality blastocyst (GQB) rate on day 5-6 per metaphase II (MII) oocyte.

RESULTS

Fertilization rate and day 5-6 blastocyst rate per MII oocyte differed significantly in favour of the study arm, whereas GQB rate did not. A subgroup analysis, stratified by maternal age, revealed significant improvements in the study arm for day 3 embryo development rate, day 5-6 blastocyst rate, GQB rate and blastocyst utilization rate for patients aged 35-40 years, while the impacts on these endpoints were much smaller in patients aged <35 years. Ninety-four single vitrified blastocyst transfers (SVBT) were performed in each arm. The blastocysts derived from the study arm showed better results of SVBT for patients aged 35-40 years, defined by embryo implantation rate, fetal heartbeat rate and live birth rate, whereas these variables did not differ significantly between the two arms when assessing the results for patients of all ages and patients aged <35 years.

CONCLUSIONS

Embryo development and SVBT outcomes of treatment cycles of patients aged 35-40 years improved significantly when using AOX-supplemented culture media throughout the IVF process.

Sod1 deficiency in mouse oocytes during in vitro maturation increases chromosome segregation errors with a reduced BUBR1 at kinetochore

Purpose

This study aimed to investigate the molecular mechanisms associated with chromosome segregation errors caused by intrinsic oxidative stress during in vitro oocyte maturation (IVM) using oocytes from Sod1-deficient (Sod1KO) mice.

Methods

Ovulated or in vitro matured cumulus-cells oocyte complexes (COCs) were collected from wild-type (WT) and Sod1KO mice and evaluated chromosome alignment, chromosome segregation, meiotic progression, and BUBR1 and REC8 protein expression levels.

Results

In 21% O2 IVM, the Sod1KO had significantly higher frequencies of chromosome misalignment and segregation errors compared to the WT, and they also reached Germinal Vesicle Break Down (GVBD) and M I stages peak earlier and showed a shorter M I stage residence time compared to the WT. These changes were associated with a decrease in the recruitment of BUBR1 to kinetochores at M I stage, but there were no differences in the expression of REC8 between the two genotypes. Furthermore, the addition of L-ascorbic acid (AsA) or N-acetyl-L-cysteine (NAC) during IVM reduced the frequency of chromosome segregation errors in Sod1KO oocytes.

Conclusions

Oxidative stress caused by Sod1 deficiency during IVM impairs the spindle assembly checkpoint function due to a decrease in the recruitment of BUBR1 to M I stage kinetochores, leading to abnormalities in meiotic progression and chromosome segregation.

Effect of aging on semen and embryonic developmental scores in assisted reproductive technology

Purpose

The effects of female aging on fertility have been extensively studied; however, this is not the case for aging males. Embryonic selection using time-lapse observations is helpful for successful embryo transfer; however, information on the effect of male aging on time-lapse is insufficient. We analyzed the impact of paternal aging on sperm characteristics, embryonic developmental kinetics, embryo evaluation score, and pregnancy outcomes.

Methods

We used data from patients treated at our clinic between January 2020 and December 2022. We evaluated the effects of aging in men and women on semen data, in vitro fertilization (IVF) results, developmental kinetics, embryo evaluation scores, and embryo transfer outcomes using a retrospective approach.

Results

Male aging adversely affected the semen characteristics. Although female aging had adverse effects on IVF, embryonic developmental kinetics, and embryo transfer outcomes, male aging did not have such a significant impact. Female aging decreased the iDAScore and Gardner criteria, whereas male aging did not affect the iDAScore.

Conclusions

Aging in males had a negative effect on semen data. Contrary to the impact of aging on women, aging in men did not have a significant effect on embryo and gestation rates following embryo transfer.

Exploring potential pathways from oxidative stress to ovarian aging

AIM

In developed nations, women have increasingly deferred childbearing, leading to a rise in demand for infertility treatments and the widespread use of assisted reproductive technologies. However, despite advancements in in vitro fertilization (IVF), live birth rates among women over 40 remain suboptimal. Mitochondrial dysfunction is widely recognized as a key factor in the processes driving the age-related deterioration in both the quantity and quality of oocytes. We aim to summarize current insights into ovarian aging, with a particular focus on pathways that impair mitochondrial function, and explore directions for future research.

METHODS

Electronic databases were searched for articles published up to June 30, 2024.

RESULTS

Ongoing ovulation, luteolysis, and menstruation trigger exogenous reactive oxygen species (ROS)-mediated oxidative stress that damages mitochondrial DNA. This, in turn, reduces nuclear gene expression, compromises mitochondrial oxidative phosphorylation, and diminishes adenosine 5' triphosphate production. Persistent endogenous ROS further exacerbate mitochondrial DNA damage and aneuploidy, ultimately causing irreversible chromosomal abnormalities, leading to oocyte aging.

CONCLUSIONS

We have delineated the pathway from oxidative stress to ovarian aging. Early detection and management of ovarian aging present challenges and opportunities to enhance IVF treatment strategies.

Impact of autologous mitochondrial transfer on obstetric and neonatal health of offspring: A small single-center case series

INTRODUCTION

A pilot study was carried out to test the efficacy of the autologous mitochondrial transfer therapy (AUGMENT) technique. No improvements in pregnancy rate, development, or embryo quality were observed in the AUGMENT-treated group versus the Control group in this study. The main objective of this research is to analyze whether AUGMENT technology did have any impact on the obstetric and perinatal outcomes of pregnancies and children resulting from treated oocytes.

METHODS

Follow up study of women with a livebirth who participated in a pilot randomized controlled trial in which sibling MII oocytes were randomly allocated to AUGMENT + intracytoplasmic sperm injection (ICSI) (AUGMENT group) or ICSI alone (control group). Preimplantation genetic testing for aneuploidy was performed in both groups. Pregnancy and neonatal outcomes of 14 women (15 pregnancies) and their 18 children were analyzed. The information was retrieved by reviewing the medical records or through questionnaires sent to the patients.

RESULTS

No differences were found in this small case series between the AUGMENT and control groups regarding the rate of gestational complications, birth defects, gestational age at delivery (271.4 ± 12.56 vs 278 ± 10.4 days), birthweight (3.1 ± 0.6 kg vs. 3.1 ± 0.4 kg) and neonatal outcome.

DISCUSSION

The few pregnancies achieved using AUGMENT oocyte therapy had similar outcomes than controls in this very small series. Our very preliminary data need to be confirmed in larger samples. The long term follow up of these children also needs to be analyzed.

Association of ambient air pollutant mixtures with IVF/ICSI-ET clinical pregnancy rates during critical exposure periods

STUDY QUESTION

Does exposure to a mixture of ambient air pollutants during specific exposure periods influence clinical pregnancy rates in women undergoing IVF/ICSI-embryo transfer (ET) cycles?

SUMMARY ANSWER

The specific exposure period from ET to the serum hCG test was identified as a critical exposure window as exposure to sulfur dioxide (SO2) or a combination of air pollutants was associated with a decreased likelihood of clinical pregnancy.

WHAT IS KNOWN ALREADY

Exposure to a single pollutant may impact pregnancy outcomes in women undergoing ART. However, in daily life, individuals often encounter mixed pollution, and limited research exists on the effects of mixed air pollutants and the specific exposure periods.

STUDY DESIGN SIZE DURATION

This retrospective cohort study involved infertile patients who underwent their initial IVF/ICSI-ET cycle at an assisted reproduction center between January 2020 and January 2023. Exclusions were applied for patients meeting specific criteria, such as no fresh ET, incomplete clinical and address information, residency outside the 17 cities in the Sichuan Basin, age over 45 years, use of donor semen, thin endometrium (<8 mm) and infertility factors unrelated to tubal or ovulation issues. In total, 5208 individuals were included in the study.

PARTICIPANTS/MATERIALS SETTING METHODS

Daily average levels of six air pollutants (fine particulate matter (PM2.5), inhalable particulate matter (PM10), SO2, nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3)) were acquired from air quality monitoring stations. The cumulative average levels of various pollutants were determined using the inverse distance weighting (IDW) method across four distinct exposure periods (Period 1: 90 days before oocyte retrieval; Period 2: oocyte retrieval to ET; Period 3: ET to serum hCG test; Period 4: 90 days before oocyte retrieval to serum hCG test). Single-pollutant logistic regression, two-pollutant logistic regression, Quantile g-computation (QG-C) regression, and Bayesian kernel machine regression (BKMR) were employed to evaluate the influence of pollutants on clinical pregnancy rates. Stratified analyses were executed to discern potentially vulnerable populations.

MAIN RESULTS AND THE ROLE OF CHANCE

The clinical pregnancy rate for participants during the study period was 54.53%. Single-pollutant logistic models indicated that for PM2.5 during specific exposure Period 1 (adjusted odds ratio [aOR] = 0.83, 95% CI: 0.70-0.99) and specific exposure Period 4 (aOR = 0.83, 95% CI: 0.69-0.98), and SO2 in specific exposure Period 3 (aOR = 0.92, 95% CI: 0.86-0.99), each interquartile range (IQR) increment exhibited an association with a decreased probability of clinical pregnancy. Consistent results were observed with dual air pollution models. In the multi-pollution analysis, QG-C indicated a 12% reduction in clinical pregnancy rates per IQR increment of mixed pollutants during specific exposure Period 3 (aOR = 0.89, 95% CI: 0.79-0.99). Among these pollutants, SO2 (33.40%) and NO2 (33.40%) contributed the most to the negative effects. The results from BKMR and QG-C were consistent. Stratified analysis revealed increased susceptibility to ambient air pollution among individuals who underwent transfer of two embryos, those with BMI ≥ 24 kg/m2 and those under 35 years old.

LIMITATIONS REASONS FOR CAUTION

Caution was advised in interpreting the results due to the retrospective nature of the study, which was prone to selection bias from non-random sampling. Smoking and alcohol, known confounding factors in IVF/ICSI-ET, were not accounted for. Only successful cycles that reached the hCG test were included, excluding a few patients who did not reach the ET stage. While IDW was used to estimate pollutant concentrations at residential addresses, data on participants' work locations and activity patterns were not collected, potentially affecting the accuracy of exposure prediction.

WIDER IMPLICATIONS OF THE FINDINGS

Exposure to a mixture of pollutants, spanning from ET to the serum hCG test (Period 3), appeared to be correlated with a diminished probability of achieving clinical pregnancy. This association suggested a potential impact of mixed pollutants on the interaction between embryos and the endometrium, as well as embryo implantation during this critical stage, potentially contributing to clinical pregnancy failure. This underscored the importance of providing women undergoing ART with comprehensive information to comprehend the potential environmental influences and motivating them to adopt suitable protective measures when feasible, thereby mitigating potential adverse effects of contaminants on reproductive health.

STUDY FUNDING/COMPETING INTERESTS

This work received support from the National Key Research and Development Program of China (No. 2023YFC2705900), the National Natural Science Foundation of China (Nos. 82171664, 81971391, 82171668), the Natural Science Foundation of Chongqing Municipality of China (Nos. CSTB2022NSCQ-LZX0062, CSTB2023TIAD-KPX0052) and the Foundation of State Key Laboratory of Ultrasound in Medicine and Engineering (No. 2021KFKT013). The authors report no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Anti-Müllerian hormone does not predict cumulative pregnancy rate in non-infertile women following four IUI cycles with donor sperm

PURPOSE

To evaluate the predictive value of serum AMH for clinical pregnancy in non-infertile population undergoing intrauterine insemination with donor sperm (ds-IUI).

METHODS

This multicenter prospective study (ClinicalTrials.gov ID: NCT06263192) recruited all non-infertile women undergoing ds-IUI from June 2020 to December 2022 in three different fertility clinics in Spain and Chile. Indications for ds-IUI included severe oligoasthenoteratozoospermia, female partner, or single status. Clinical pregnancy rates were compared between women with AMH ≥ 1.1 and < 1.1 ng/mL. The main outcome measure was the cumulative clinical pregnancy rate after up to 4 ds-IUI cycles.

RESULTS

A total of 458 ds-IUI cycles were performed among 245 patients, of whom 108 (44.08%) achieved clinical pregnancy within 4 cycles, 60.2% of these occurring in the first attempt and 84.2% after two attempts. We found no significant differences in AMH levels or other parameters (such as age, BMI, FSH, AFC) between women who became pregnant and those who did not. Cumulative pregnancy rates and logistic regression analysis revealed that AMH ≥ 1.1 ng/mL was not predictive of ds-IUI success. While a high positive correlation was observed between AFC and AMH (r = 0.67, p < 0.001), ROC curve analyses indicated that neither of these ovarian reserve markers accurately forecasts cumulative ds-IUI outcomes in non-infertile women.

CONCLUSIONS

The findings of this multicenter study suggest that AMH is not a reliable predictor of pregnancy in non-infertile women undergoing ds-IUI. Even women with low AMH levels can achieve successful pregnancy outcomes, supporting the notion that diminished ovarian reserve should not restrict access to ds-IUI treatments in eligible non-infertile women.

Analysis of determinants of infertility among women at <i>in vitro</i> fertilization clinic in Surabaya

In social life and global health, infertility is common. History of abdominal surgery, body mass index (BMI), endometriosis, menstrual history, and polycystic ovarian syndrome (PCOS) have not been fully explained as female infertility factors. This study examined infertility causes at ASHA in vitro fertilization Primasatya Husada Citra (PHC) Hospital Surabaya. This quantitative study was cross-sectional. In May-July 2023, 82 childbearing-age women with infertility issues visited the hospital and completed questionnaires. Description and analysis were performed using the Wilcoxon rank test to evaluate menstrual history, BMI, PCOS, endometriosis, and abdominal surgery history in relation to infertility. Infertility was statistically associated with abdominal surgery history (P=0.008), BMI (P=0.000), endometriosis diagnosis (P=0.000), and PCOS (P=0.000). Women with abdominal surgery, endometriosis, and PCOS had significant infertility. Women’s infertility can be caused by ovulation disorders, tubal and pelvic disorders, or uterine disorders, but one-third of cases are unexplained. Infertility treatment may benefit from addressing abdominal surgery history, BMI, endometriosis, and PCOS. Early intervention and targeted care based on these determinants may improve fertility outcomes and reduce unexplained infertility.

Single-cell proteomics reveals decreased abundance of proteostasis and meiosis proteins in advanced maternal age oocytes

Advanced maternal age is associated with a decline in oocyte quality, which often leads to reproductive failure in humans. However, the mechanisms behind this age-related decline remain unclear. To gain insights into this phenomenon, we applied plexDIA, a multiplexed data-independent acquisition, single-cell mass spectrometry method, to analyze the proteome of oocytes from both young women and women of advanced maternal age. Our findings primarily revealed distinct proteomic profiles between immature fully grown germinal vesicle and mature metaphase II oocytes. Importantly, we further show that a woman's age is associated with changes in her oocyte proteome. Specifically, when compared to oocytes obtained from young women, advanced maternal age oocytes exhibited lower levels of the proteasome and TRiC complex, as well as other key regulators of proteostasis and meiosis. This suggests that aging adversely affects the proteostasis and meiosis networks in human oocytes. The proteins identified in this study hold potential as targets for improving oocyte quality and may guide future studies into the molecular processes underlying oocyte aging.

Single-cell proteomics reveals decreased abundance of proteostasis and meiosis proteins in advanced maternal age oocytes

Advanced maternal age is associated with a decline in oocyte quality, which often leads to reproductive failure in humans. However, the mechanisms behind this age-related decline remain unclear. To gain insights into this phenomenon, we applied plexDIA, a multiplexed, single-cell mass spectrometry method, to analyze the proteome of oocytes from both young women and women of advanced maternal age. Our findings primarily revealed distinct proteomic profiles between immature fully grown germinal vesicle and mature metaphase II oocytes. Importantly, we further show that a woman's age is associated with changes in her oocyte proteome. Specifically, when compared to oocytes obtained from young women, advanced maternal age oocytes exhibited lower levels of the proteasome and TRiC complex, as well as other key regulators of proteostasis and meiosis. This suggests that aging adversely affects the proteostasis and meiosis networks in human oocytes. The proteins identified in this study hold potential as targets for improving oocyte quality and may guide future studies into the molecular processes underlying oocyte aging.

A Molecular Perspective and Role of NAD+ in Ovarian Aging

The decline in female fecundity is linked to advancing chronological age. The ovarian reserve diminishes in quantity and quality as women age, impacting reproductive efficiency and the aging process in the rest of the body. NAD+ is an essential coenzyme in cellular energy production, metabolism, cell signaling, and survival. It is involved in aging and is linked to various age-related conditions. Hallmarks associated with aging, diseases, and metabolic dysfunctions can significantly affect fertility by disturbing the delicate relationship between energy metabolism and female reproduction. Enzymes such as sirtuins, PARPs, and CD38 play essential roles in NAD+ biology, which actively consume NAD+ in their enzymatic activities. In recent years, NAD+ has gained much attention for its role in aging and age-related diseases like cancer, Alzheimer's, cardiovascular diseases, and neurodegenerative disorders, highlighting its involvement in various pathophysiological processes. However, its impact on female reproduction is not well understood. This review aims to bridge this knowledge gap by comprehensively exploring the complex interplay between NAD+ biology and female reproductive aging and providing valuable information that could help develop plans to improve women's reproductive health and prevent fertility issues.

The close relationship between oocyte aging and telomere shortening, and possible interventions for telomere protection

As women delay childbearing due to socioeconomic reasons, understanding molecular mechanisms decreasing oocyte quantity and quality during ovarian aging becomes increasingly important. The ovary undergoes biological aging at a higher pace when compared to other organs. As is known, telomeres play crucial roles in maintaining genomic integrity, and their shortening owing to increased reactive oxygen species, consecutive cellular divisions, genetic and epigenetic alterations is associated with loss of developmental competence of oocytes. Novel interventions such as antioxidant treatments and regulation of gene expression are being investigated to prevent or rescue telomere attrition and thereby oocyte aging. Herein, potential factors and molecular mechanisms causing telomere shortening in aging oocytes were comprehensively reviewed. For the purpose of extending reproductive lifespan, possible therapeutic interventions to protect telomere length were also discussed.

Automated Single-Sperm Selection Software (SiD) during ICSI: A Prospective Sibling Oocyte Evaluation

The computer-assisted program SiD was developed to assess and select sperm in real time based on motility characteristics. To date, there are limited studies examining the correlation between AI-assisted sperm selection and ICSI outcomes. To address this limit, a total of 646 sibling MII oocytes were randomly divided into two groups as follows: the ICSI group (n = 320): ICSI performed with sperm selected by the embryologist and the ICSI-SiD group (n = 326): ICSI performed with sperm selected using SiD software. Our results show a non-significant trend towards improved outcomes in the ICSI-SiD group across various biological parameters, including fertilization, cleavage, day 3 embryo development, blastocyst development, and quality on day 5. Similarly, we observed a non-significant increase in these outcomes when comparing both groups with sperm selection performed by a junior embryologist. Embryo development was monitored using a timelapse system. Some fertilization events happen significantly earlier when SiD is used for ICSI, but no significant difference was observed in the ICSI-SiD group for other timepoints. We observed comparable cumulative early and clinical pregnancy rates after ICSI-SiD. This preliminary investigation illustrated that employing the automated sperm selection software SiD leads to comparable biological outcomes, suggesting its efficacy in sperm selection.

Association of Follicular Fluid Antioxidants Activity with Aging and In Vitro Fertilization Outcome: A Cross-Sectional Study

BACKGROUND

This research was aimed at assessing the relationship between the follicular fluid (FF) antioxidants activity, aging and in vitro fertilization (IVF) outcome.

MATERIALS AND METHODS

The present cross-sectional study was carried out on 65 women undergoing IVF/intracytoplasmic sperm injection (IVF/ICSI) cycles due to unexplained infertility. Ovarian stimulation was performed using the long gonadotropin-releasing hormone (GnRH) agonist protocol. After ovum pickup, FF was collected and processed to measure the level of superoxide dismutase (SOD), catalase (CAT) activity, total antioxidant capacity (TAC) and glutathione (GSH). Day 3 after ICSI, fresh embryos were transferred and later, possible pregnancy was assessed. Patients participating in this study were divided into four groups on the basis of age and pregnancy outcome.

RESULTS

SOD activity was not significantly different between the groups (P=0.218). GSH in the group whose participants were aged ≤35 years and were pregnant was higher than that in other groups. CAT activity in groups with younger participants was higher compared to the other groups. The mean TAC was higher in groups with pregnant participants compared to the non-pregnant women. Correlation analysis showed that: GSH level had a significant negative correlation with age (P<0.001, R -0.55) and a significant positive correlation with pregnancy (P=0.015, R=0.30). CAT level also had a significant negative correlation with age (P<0.001, R=-0.42) and the level of TAC had a significant positive correlation with pregnancy (P<0.001, R=0.59).

CONCLUSION

According to our results, the levels of TAC, GSH and CAT in younger and pregnant women were higher compared with those undergoing ICSI cycles. Given the correlation of FF antioxidant activity with age and pregnancy, it is necessary to carry out more research on these compounds and the maintenance of pregnancy.

Factors associated with infertility among the Lebanese population: a cross-sectional study

The incidence of female infertility is growing worldwide and its rate varies across countries. . The goal of this study is to assess the rate of female infertility and identify its associated factors among Lebanese women. This cross-sectional study was conducted between January to May 2019, enrolling a total of 952 females. The mean age was 34.8 ± 8 years and the rate of infertility was 34.3%. The multivariable analysis taking presence vs absence of infertility as the dependent variable, showed that patients with advanced age (aOR = 1.04), endometriosis (aOR = 2.175) and polycystic ovarian syndrome (aOR = 1.41) were significantly associated with higher rate of infertility. On the other hand, having a college level of education compared to a school level was significantly associated with lower odds of infertility (aOR = 0.511). The study highlights that the rate of infertility is high in Lebanon and is mainly associated with various sociodemographic factors and disease states. The findings raise the need to establish awareness campaigns that focus on early diagnosis of infertility, control the associated factors, and treat underlying comorbid conditions.

Epigenetic aging of mammalian gametes

The process of aging refers to physiological changes that occur to an organism as time progresses and involves changes to DNA, proteins, metabolism, cells, and organs. Like the rest of the cells in the body, gametes age, and it is well established that there is a decline in reproductive capabilities in females and males with aging. One of the major pathways known to be involved in aging is epigenetic changes. The epigenome is the multitude of chemical modifications performed on DNA and chromatin that affect the ability of chromatin to be transcribed. In this review, we explore the effects of aging on female and male gametes with a focus on the epigenetic changes that occur in gametes throughout aging. Quality decline in oocytes occurs at a relatively early age. Epigenetic changes constitute an important part of oocyte aging. DNA methylation is reduced with age, along with reduced expression of DNA methyltransferases (DNMTs). Histone deacetylases (HDAC) expression is also reduced, and a loss of heterochromatin marks occurs with age. As a consequence of heterochromatin loss, retrotransposon expression is elevated, and aged oocytes suffer from DNA damage. In sperm, aging affects sperm number, motility and fecundity, and epigenetic changes may constitute a part of this process. 5 methyl-cytosine (5mC) methylation is elevated in sperm from aged men, but methylation on Long interspersed nuclear elements (LINE) elements is reduced. Di and trimethylation of histone 3 lysine 9 (H3K9me2/3) is reduced in sperm from aged men and trimethylation of histone 3 lysine 27 (H3K27me3) is elevated. The protamine makeup of sperm from aged men is also changed, with reduced protamine expression and a misbalanced ratio between protamine proteins protamine P1 and protamine P2. The study of epigenetic reproductive aging is recently gaining interest. The current status of the field suggests that many aspects of gamete epigenetic aging are still open for investigation. The clinical applications of these investigations have far-reaching consequences for fertility and sociological human behavior.

Mitigating Age-Related Ovarian Dysfunction with the Anti-Inflammatory Agent MIT-001

Ovarian aging is a major obstacle in assisted reproductive medicine because it leads to ovarian dysfunction in women of advanced age. Currently, there are no effective treatments to cure age-related ovarian dysfunction. In this study, we investigated the effect of MIT-001 on the function of aged ovaries. Young and old mice were utilized in this study. MIT-001 was intraperitoneally administered, and the number of follicles and oocytes was analyzed. Each group was then retrieved for RNA and protein isolation. Total RNA was subjected to mRNA next-generation sequencing. Protein extracts from ovarian lysates were used to evaluate various cytokine levels in the ovaries. MIT-001 enhanced follicles and the number of oocytes were compared with non-treated old mice. MIT-001 downregulated immune response-related transcripts and cytokines in the ovaries of old mice. MIT-001 modulates the immune complex responsible for generating inflammatory signals and has the potential to restore the function of old ovaries and improve female fertility.

Human embryos derived from first polar body nuclear transfer exhibit comparatively abnormal morphokinetics during development

OBJECTIVE

Reconstructed oocytes after polar body genome transfer constitute a potential therapeutic option for patients with a history of embryo fragmentation and advanced maternal age. However, the rescue of genetic material from the first polar body (PB1) through introduction into the donor cytoplasm is not yet ready for clinical application.

METHODS

Eighty-five oocytes were obtained following in vitro maturation (IVM) and divided into two groups: PB1 nuclear transfer (PB1NT; n=54) and control (n=31). Following enucleation and PB1 genomic transfer, PB1 fusion was assessed. Subsequently, all fused oocytes underwent intracytoplasmic sperm injection (ICSI) and were cultured in an incubator under a time-lapse monitoring system to evaluate fertilization, embryonic morphokinetic parameters, and cleavage patterns.

RESULTS

Following enucleation and fusion, 77.14% of oocytes survived, and 92.59% of polar bodies (PBs) fused. However, the normal fertilization rate was lower in the PB1NT group than in the control group (56.41% vs. 92%, p=0.002). No significant differences were observed in embryo kinetics between the groups, but a significant difference was detected in embryo developmental arrest after the four-cell stage, along with abnormal cleavage division in the PB1NT group. This was followed by significant between-group differences in the implantation potential rate and euploidy status. Most embryos in the PB1NT group had at least one abnormal cleavage division (93.3%, p=0.001).

CONCLUSION

Fresh PB1NT oocytes successfully produced normal zygotes following PB fusion and ICSI in IVM oocytes. However, this was accompanied by low efficiency in developing into cleavage embryos, along with an increase in abnormal cleavage patterns.

Screening for diminished ovarian reserve in Portugal: a cost-saving answer to shorten the fertility journey

Aim: Assess the budget impact of nationwide screening for diminished ovarian reserve (OR), via anti-Müllerian hormone (AMH) levels, to the Portugal National Health System (NHS). Patients & methods: The clinical journey was determined using literature and the family planning decision-making process/response using survey results. A panel of four local clinicians validated all assumptions/inputs. Results: Screening for OR led to an expected savings of € 9.4 million for the NHS, driven by a 24% reduction in medically assisted reproduction (MAR) use. When needed, referral for MAR was earlier and more women used first-line versus second-line techniques. The model estimated a 12% decrease in failure. Conclusion: This model shows AMH screening may allow more informed decisions, leading to a shorter fertility journey, more efficient use of treatments, and substantial cost-savings for the NHS.

Lovastatin, an Up-Regulator of Low-Density Lipoprotein Receptor, Enhances Follicular Development in Mouse Ovaries

Ovarian aging hampers in vitro fertilization in assisted reproductive medicine and has no cure. Lipoprotein metabolism is associated with ovarian aging. It remains unclear how to overcome poor follicular development with aging. Upregulation of the low-density lipoprotein receptor (LDLR) enhances oogenesis and follicular development in mouse ovaries. This study investigated whether upregulation of LDLR expression using lovastatin enhances ovarian activity in mice. We performed superovulation using a hormone and used lovastatin to upregulate LDLR. We histologically analyzed the functional activity of lovastatin-treated ovaries and investigated gene and protein expression of follicular development markers, using RT-qPCR and Western blotting. Histological analysis showed that lovastatin significantly increased the numbers of antral follicles and ovulated oocytes per ovary. The in vitro maturation rate was 10% higher for lovastatin-treated ovaries than for control ovaries. Relative LDLR expression was 40% higher in lovastatin-treated ovaries than in control ovaries. Lovastatin significantly increased steroidogenesis in ovaries and promoted the expression of follicular development marker genes such as anti-Mullerian hormone, Oct3/4, Nanog, and Sox2. In conclusion, lovastatin enhanced ovarian activity throughout follicular development. Therefore, we suggest that upregulation of LDLR may help to improve follicular development in clinical settings. Modulation of lipoprotein metabolism can be used with assisted reproductive technologies to overcome ovarian aging.

The ginsenoside Rh2 protects porcine oocytes against aging and oxidative stress by regulating SIRT1 expression and mitochondrial activity

Post-ovulatory aging, a major problem faced by oocytes cultured in vitro, causes oxidative damage and mitochondrial dysfunction in oocytes. The ginsenoside Rh2 is one of the main monomeric components of ginseng, but its effects on porcine oocytes are unknown. In the present study, in vitro aging (IVA) and accelerated induction of aging using H₂O₂ resulted in DNA damage and an increased incidence of abnormal spindle formation in porcine oocytes. Rh2 supplementation increased the antioxidant capacity, reduced the occurrence of early apoptosis, and improved the development of in vitro fertilized blastocysts. It also rescued the abnormal aggregation of mitochondria and the decrease of the mitochondrial membrane potential under mitochondrial dysfunction. Meanwhile, Rh2 enhanced mRNA expression of the anti-aging and mitochondrial biogenesis-related genes silent information regulator of transcription 1 (SIRT1) and peroxisome proliferator-activated receptor coactivator 1-α (PGC-1α), and the antioxidant gene superoxide dismutase 1 (SOD1). The protection of porcine oocytes against aging and oxidative stress by Rh2 was confirmed using the SIRT1-specific inhibitor EX-527. Our results reveal that Rh2 upregulates SIRT1/PGC-1α to enhance mitochondrial function in porcine oocytes and improve their quality. Our study indicates that Rh2 can be used to prevent mitochondrial dysfunction in oocytes.

Biphasic oxygen tension promotes the formation of transferable blastocysts in patients without euploid embryos in previous monophasic oxygen cycles

This study evaluated whether the concentration of biphasic O₂ (5-2%) promotes the formation of qualified blastocysts (QBs) and euploid blastocysts and the probability of cycles with transferable blastocysts. The paired experimental design included a total 90 patients (180 cycles) without euploid blastocysts in previous monophasic O₂ (5%) cycles were enrolled for an additional cycle of biphasic O₂ (5-2%). In the biphasic O₂ (5-2%) group, the QB rate (35.8%, 225/628) was significantly higher than that in the monophasic O₂ (5%) group (23.5%, 137/582; p < 0.001). In addition, the euploid blastocyst number (0.5 ± 0.8) and the percentage of cycles with transferable blastocysts were significantly higher in the biphasic O₂ (5-2%) group (57.8%, 52/90) than those in the monophasic O₂ (5%) group (0 and 35.6%, 32/90, respectively; p < 0.01). Multivariable regression analysis also indicated that the QB rate and the probability of cycles with transferable blastocysts correlated with O₂ tension (OR 1.535, 95% CI 1.325-1.777, and OR 3.191, 95% CI 1.638-5.679, respectively; p < 0.001). Biphasic O₂ culture can be used as an alternative strategy to increase the euploid QBs and the probability of cycles with transferable blastocysts in patients with a poor prognosis.

Kunling Wan improves oocyte quality by regulating the PKC/Keap1/Nrf2 pathway to inhibit oxidative damage caused by repeated controlled ovarian hyperstimulation

ETHNOPHARMACOLOGICAL RELEVANCE

Kunling Wan (KW) is a traditional Chinese medicine that is principally used for kidney deficiency, qi stagnation, and blood stasis, which are basic syndromes of infertility in China. KW can improve ovarian follicular development, ovarian function, and endometrial receptivity, which lead to improving pregnancy outcomes. Repeated controlled ovarian hyperstimulation (COH) reduces oocyte quality and results in a lower pregnancy rate. Whether KW has the potential to improve oocyte quality reduced by repeated COH has yet to be determined.

AIMS OF THE STUDY

The aim of this study wwas to evaluate the effect of KW on oocyte quality after damage due to repeated COH, and to investigate the mechanism(s) underlying the antioxidative protection of oocytes by mitochondria.

MATERIALS AND METHODS

Female Kunming mice were randomly divided into four groups: normal group, model (repeated COH) group, KW group, and N-acetylcysteine (NAC) group. We observed the morphology and quality of mitochondria, level of reactive oxygen species (ROS), and antioxidant enzymes activity of each group. Oocytes were treated with H2O2 and KW-containing serum, and we determined the antioxidant effects of KW on H2O2-treated oocytes and the mechanism involved in the regulation of Nrf2 in reducing oxidative damage.

RESULTS

Our results revealed that repeated COH caused oxidative damage and impaired oocyte mitochondrial function and structure, resulting in poor oocyte quality. KW pretreatment reduced oxidative damage by inhibiting ROS production and improving mitochondrial structure and function, thereby enhancing overall oocyte quality. In response to H2O2, KW activated the PKC/Keap1/Nrf2-signaling pathway and promoted the translocation of Nrf2 from the cytoplasm to the nucleus, which activated the expression of SOD and GSH-Px, and removed the excess ROS that caused the initial mitochondrial damage.

CONCLUSIONS

KW improved oocyte quality perturbed by repeated COH via reducing oxidative effects and improving mitochondrial function. The mechanism may be related to regulation of the PKC/Keap1/Nrf2 pathway in removing excess ROS.

Stem Cell-Based Therapeutic Strategies for Premature Ovarian Insufficiency and Infertility: A Focus on Aging

Reproductive aging is on the rise globally and inseparable from the entire aging process. An extreme form of reproductive aging is premature ovarian insufficiency (POI), which to date has mostly been of idiopathic etiology, thus hampering further clinical applications and associated with enormous socioeconomic and personal costs. In the field of reproduction, the important functional role of inflammation-induced ovarian deterioration and therapeutic strategies to prevent ovarian aging and increase its function are current research hotspots. This review discusses the general pathophysiology and relative causes of POI and comprehensively describes the association between the aging features of POI and infertility. Next, various preclinical studies of stem cell therapies with potential for POI treatment and their molecular mechanisms are described, with particular emphasis on the use of human induced pluripotent stem cell (hiPSC) technology in the current scenario. Finally, the progress made in the development of hiPSC technology as a POI research tool for engineering more mature and functional organoids suitable as an alternative therapy to restore infertility provides new insights into therapeutic vulnerability, and perspectives on this exciting research on stem cells and the derived exosomes towards more effective POI diagnosis and treatment are also discussed.

Metformin promotes in vitro maturation of oocytes from aged mice by attenuating mitochondrial oxidative stress via SIRT3-dependent SOD2ac

Human female fecundity decreases irreversibly as chronological age rises, adversely affecting oocyte quality, consequently worsening pregnancy outcomes and increasing the extent of birth defects. The first-line type 2 diabetes treatment metformin has been associated with delayed aging and reduction of oxidative stress; yet it remains unclear if metformin confers any benefits for oocytes from aged mice, particularly in the context of the assisted human reproductive technology (ART) known as in vitro maturation (IVM). Here, we found that adding metformin into the M16 culture medium of oocytes from aged mice significantly improved both oocyte maturation and early embryonic development. This study showed that metformin reduced the extent of meiotic defects and maintained a normal distribution of cortical granules (CGs). RNA-seq analysis of metformin-treated oocytes revealed genes apparently involved in the reduction of mitochondrial ROS. Further, the results supported that the metformin improved mitochondrial function, reduced apoptosis, increased the extent of autophagy, and reduced mitochondrial ROS via SIRT3-mediated acetylation status of SOD2K68 in oocytes from aged mice. Thus, this finding demonstrated a protective effect for metformin against the decreased quality of oocytes from aged mice to potentially improve ART success rates and illustrated a potential strategy to prevent or delay reproductive aging.

Importance of Antioxidant Supplementation during In Vitro Maturation of Mammalian Oocytes

The in vitro embryo production (IVEP) technique is widely used in the field of reproductive biology. In vitro maturation (IVM) is the first and most critical step of IVEP, during which, the oocyte is matured in an artificial maturation medium under strict laboratory conditions. Despite all of the progress in the field of IVEP, the quality of in vitro matured oocytes remains inferior to that of those matured in vivo. The accumulation of substantial amounts of reactive oxygen species (ROS) within oocytes during IVM has been regarded as one of the main factors altering oocyte quality. One of the most promising approaches to overcome ROS accumulation within oocytes is the supplementation of oocyte IVM medium with antioxidants. In this article, we discuss recent advancements depicting the adverse effects of ROS on mammalian oocytes. We also discuss the potential use of antioxidants and their effect on both oocyte quality and IVM rate.

Cellular senescence and senolytics: the path to the clinic

Interlinked and fundamental aging processes appear to be a root-cause contributor to many disorders and diseases. One such process is cellular senescence, which entails a state of cell cycle arrest in response to damaging stimuli. Senescent cells can arise throughout the lifespan and, if persistent, can have deleterious effects on tissue function due to the many proteins they secrete. In preclinical models, interventions targeting those senescent cells that are persistent and cause tissue damage have been shown to delay, prevent or alleviate multiple disorders. In line with this, the discovery of small-molecule senolytic drugs that selectively clear senescent cells has led to promising strategies for preventing or treating multiple diseases and age-related conditions in humans. In this Review, we outline the rationale for senescent cells as a therapeutic target for disorders across the lifespan and discuss the most promising strategies-including recent and ongoing clinical trials-for translating small-molecule senolytics and other senescence-targeting interventions into clinical use.

He's Yangchao Recipe Ameliorates Ovarian Oxidative Stress of Aging Mice under Consecutive Superovulation Involving JNK- And P53-Related Mechanism

Objective

To evaluate the effects of He's Yangchao Recipe (HSYC) on ameliorating ovarian oxidative stress of aging mice under consecutive superovulation.

Methods

An 8-month-old C57BL/6 female mouse was chosen to establish an aging model under ovarian hyperstimulation. Mice were randomly separated into four groups: R1 as the control group, R4 as the model group, NR4 with N-acetyl-L-cysteine (NAC) administration, and TR4 with HSYC administration. Oocyte collection, in vitro fertilization, and embryo culture were performed. The serum hormone levels were measured by enzyme-linked immunosorbent assays (ELISA); the reactive oxygen species (ROS) level of oocytes, the number of growing follicles, corpus luteum, ovulated oocytes, and developing embryos at each stage, along with the proportions of fragmented oocytes and abnormal mitochondria in granulosa cells (GCs) and the apoptosis rate of GCs were calculated; the mRNA and protein levels of JNK, P53, BAX were detected by real-time PCR and the Simple Western System.

Results

HSYC enhanced estradiol, progesterone, and inhibin-B levels and increased growing follicle and corpus luteum and ovulated egg counts compared to the R4 group (P < 0.05), whereas it decreased the proportions of fragmented oocytes (P < 0.01); Meanwhile, embryos from mice subjected to four superovulation cycles with HSYC treated had a higher hatching potential. The ROS level of oocytes is downregulated by HSYC (P < 0.01) and the percentage of abnormal mitochondrial in ovaries of the TR4 group was also significantly declined compared to the R4 group (P < 0.05); the most TUNEL-positive cells proportion was detected in the R4 group; nevertheless, HSYC effectively attenuated this detrimental effect (P < 0.05). The mRNA and protein expressions of JNK and P53 in ovary tissues were reduced in the TR4 group while these genes were upregulated by repeated superovulation (P < 0.05).

Conclusions

HSYC exerted promising effects on promoting the diminished ovarian reserve and decreased oocyte quality induced by both aging and consecutive ovarian superovulation, potentially via the ROS/JNK/p53 pathway.

Oocytes maintain ROS-free mitochondrial metabolism by suppressing complex I

Oocytes form before birth and remain viable for several decades before fertilization1. Although poor oocyte quality accounts for most female fertility problems, little is known about how oocytes maintain cellular fitness, or why their quality eventually declines with age2. Reactive oxygen species (ROS) produced as by-products of mitochondrial activity are associated with lower rates of fertilization and embryo survival3-5. Yet, how healthy oocytes balance essential mitochondrial activity with the production of ROS is unknown. Here we show that oocytes evade ROS by remodelling the mitochondrial electron transport chain through elimination of complex I. Combining live-cell imaging and proteomics in human and Xenopus oocytes, we find that early oocytes exhibit greatly reduced levels of complex I. This is accompanied by a highly active mitochondrial unfolded protein response, which is indicative of an imbalanced electron transport chain. Biochemical and functional assays confirm that complex I is neither assembled nor active in early oocytes. Thus, we report a physiological cell type without complex I in animals. Our findings also clarify why patients with complex-I-related hereditary mitochondrial diseases do not experience subfertility. Complex I suppression represents an evolutionarily conserved strategy that allows longevity while maintaining biological activity in long-lived oocytes.

Follicular Fluid: A Powerful Tool for the Understanding and Diagnosis of Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) represents one of the leading causes of anovulatory infertility and affects 5% to 20% of women worldwide. Until today, both the subsequent etiology and pathophysiology of PCOS remain unclear, and patients with PCOS that undergo assisted reproductive techniques (ART) might present a poor to exaggerated response, low oocyte quality, ovarian hyperstimulation syndrome, as well as changes in the follicular fluid metabolites pattern. These abnormalities originate a decrease of Metaphase II (MII) oocytes and decreased rates for fertilization, cleavage, implantation, blastocyst conversion, poor egg to follicle ratio, and increased miscarriages. Focus on obtaining high-quality embryos has been taken into more consideration over the years. Nowadays, the use of metabolomic analysis in the quantification of proteins and peptides in biological matrices might predict, with more accuracy, the success in assisted reproductive technology. In this article, we review the use of human follicular fluid as the matrix in metabolomic analysis for diagnostic and ART predictor of success for PCOS patients.

The association between age-related infertility and deoxyribonucleic acid (DNA) integrity parameters of granulosa cells and lymphocytes

This study aimed to investigate the association between deoxyribonucleic acid (DNA) integrity parameters and advanced maternal age (AMA)-related infertility. The granulosa cells and the lymphocytes obtained from 119 infertile women were recruited. Patients were divided into two groups: the AMA group (≥35 years, n = 26) and the non-AMA group (<35 years, n = 93). The tail length, tail moment and tail DNA percentage were evaluated as the DNA integrity parameters using comet assay. Infertility duration (p=.001), luteinising hormone (p=.01) and progesterone levels (p<.0001) were higher and smoking was more prevalent in the AMA group (p=.001). AMA group was stimulated with higher gonadotropin doses (p=.04) and had decreased anti-mullerian hormone levels (p<.0001). All of DNA integrity parameters were distributed homogenously between the groups; however, the tail length of lymphocytes was higher (p=.02) in the AMA group. Fertilisation was lower (p=.02), oocyte quality was tended to be poor (p=.03) and blastocyst transfer was lower in the AMA group (p=.03). Embryo quality was distributed homogenously between the groups. Implantation, clinical pregnancy and live birth rates were similar between the groups. Impact StatementWhat is already known on this subject? Advanced maternal age (AMA)-related infertility is associated with diminished ovarian reserve and alteration in follicular environment resulting in poor oocyte quality; however, the exact pathophysiologic mechanism is not clear.What do the results of this study add? Tail length, tail deoxyribonucleic acid (DNA) percentage, tail moment of granulosa cells were nonsignificantly higher in the AMA group compared to younger patients. All of the DNA integrity parameters of lymphocytes were nonsignificantly higher; however, only tail length of lymphocytes was statistically higher in the AMA group than the non-AMA group. A positive correlation was observed between DNA integrity parameters of lymphocytes and body mass index. There were no correlations between DNA integrity parameters of granulosa cells and lymphocyte and infertility duration, gonadotropin dose, duration of ovarian stimulation, oocyte score, embryo score, basal hormone levels and anti-mullerian hormone levels.What are the implications of these findings for clinical practice and/or further research? Our findings offer new insight for further understanding the role of granulosa cells in mediating the poor reproductive outcome of ageing patients. Understanding the mechanisms of ovarian ageing and poor oocyte quality in women with AMA may help to identify specific targets for improving oocyte quality with ageing.

A male pheromone that improves the quality of the oogenic germline

Pheromones exchanged by conspecifics are a major class of chemical signals that can alter behavior, physiology, and development. In particular, males and females communicate with potential mating partners via sex pheromones to promote reproductive success. Physiological and developmental mechanisms by which pheromones facilitate progeny production remain largely enigmatic. Here, we describe how a Caenorhabditis elegans male pheromone, ascr#10, improves the oogenic germline. Before most signs of aging become evident, C. elegans hermaphrodites start producing lower-quality gametes characterized by abnormal morphology, increased rates of chromosomal nondisjunction, and higher penetrance of deleterious alleles. We show that exposure to the male pheromone substantially ameliorates these defects and reduces embryonic lethality. ascr#10 stimulates proliferation of germline precursor cells in adult hermaphrodites. Coupled to the greater precursor supply is increased physiological germline cell death, which is required to improve oocyte quality in older mothers. The hermaphrodite germline is sensitive to the pheromone only during a time window, comparable in duration to a larval stage, in early adulthood. During this period, prereproductive adults assess the suitability of the environment for reproduction. Our results identify developmental events that occur in the oogenic germline in response to a male pheromone. They also suggest that the opposite effects of the pheromone on gamete quality and maternal longevity arise from competition over resource allocation between soma and the germline.

Jumonji Domain-containing Protein-3 (JMJD3/Kdm6b) Is Critical for Normal Ovarian Function and Female Fertility

In females, reproductive success is dependent on the expression of a number of genes regulated at different levels, one of which is through epigenetic modulation. How a specific epigenetic modification regulates gene expression and their downstream effect on ovarian function are important for understanding the female reproductive process. The trimethylation of histone3 at lysine27 (H3K27me3) is associated with gene repression. JMJD3 (or KDM6b), a jumonji domain-containing histone demethylase specifically catalyzes the demethylation of H3K27me3, that positively influences gene expression. This study reports that the expression of JMJD3 specifically in the ovarian granulosa cells (GCs) is critical for maintaining normal female fertility. Conditional deletion of Jmjd3 in the GCs results in a decreased number of total healthy follicles, disrupted estrous cycle, and increased follicular atresia culminating in subfertility and premature ovarian failure. At the molecular level, the depletion of Jmjd3 and RNA-seq analysis reveal that JMJD3 is essential for mitochondrial function. JMJD3-mediated reduction of H3K27me3 induces the expression of Lif (Leukemia inhibitory factor) and Ctnnb1 (β-catenin), that in turn regulate the expression of key mitochondrial genes critical for the electron transport chain. Moreover, mitochondrial DNA content is also significantly decreased in Jmjd3 null GCs. Additionally, we have uncovered that the expression of Jmjd3 in GCs decreases with age, both in mice and in humans. Thus, in summary, our studies highlight the critical role of JMJD3 in nuclear-mitochondrial genome coordination that is essential for maintaining normal ovarian function and female fertility and underscore a potential role of JMJD3 in female reproductive aging.

C. elegans as a model organism to study female reproductive health

Female reproductive health has been historically understudied and underfunded. Here, we present the advantages of using a free-living nematode, Caenorhabditis elegans, as an animal system to study fundamental aspects of female reproductive health. C. elegans is a powerful high-throughput model organism that shares key genetic and physiological similarities with humans. In this review, we highlight areas of pressing medical and biological importance in the 21st century within the context of female reproductive health. These include the decline in female reproductive capacity with increasing chronological age, reproductive dysfunction arising from toxic environmental insults, and cancers of the reproductive system. C. elegans has been instrumental in uncovering mechanistic insights underlying these processes, and has been valuable for developing and testing therapeutics to combat them. Adopting a convenient model organism such as C. elegans for studying reproductive health will encourage further research into this field, and broaden opportunities for making advancements into evolutionarily conserved mechanisms that control reproductive function.

Loss of heterochromatin and retrotransposon silencing as determinants in oocyte aging

Mammalian oocyte quality reduces with age. We show that prior to the occurrence of significant aneuploidy (9M in mouse), heterochromatin histone marks are lost, and oocyte maturation is impaired. This loss occurs in both constitutive and facultative heterochromatin marks but not in euchromatic active marks. We show that heterochromatin loss with age also occurs in human prophase I-arrested oocytes. Moreover, heterochromatin loss is accompanied in mouse oocytes by an increase in RNA processing and associated with an elevation in L1 and IAP retrotransposon expression and in DNA damage and DNA repair proteins nuclear localization. Artificial inhibition of the heterochromatin machinery in young oocytes causes an elevation in retrotransposon expression and oocyte maturation defects. Inhibiting retrotransposon reverse-transcriptase through azidothymidine (AZT) treatment in older oocytes partially rescues their maturation defects and activity of the DNA repair machinery. Moreover, activating the heterochromatin machinery via treatment with the SIRT1 activating molecule SRT-1720, or overexpression of Sirt1 or Ezh2 via plasmid electroporation into older oocytes causes an upregulation in constitutive heterochromatin, downregulation of retrotransposon expression, and elevated maturation rates. Collectively, our work demonstrates a significant process in oocyte aging, characterized by the loss of heterochromatin-associated chromatin marks and activation of specific retrotransposons, which cause DNA damage and impair oocyte maturation.

Age-associated changes in cumulus cells and follicular fluid: the local oocyte microenvironment as a determinant of gamete quality

The ovary is the first organ to age in humans with functional decline evident already in women in their early 30s. Reproductive aging is characterized by a decrease in oocyte quantity and quality, which is associated with an increase in infertility, spontaneous abortions, and birth defects. Reproductive aging also has implications for overall health due to decreased endocrinological output. Understanding the mechanisms underlying reproductive aging has significant societal implications as women globally are delaying childbearing and medical interventions have greatly increased the interval between menopause and total lifespan. Age-related changes inherent to the female gamete are well-characterized and include defects in chromosome and mitochondria structure, function, and regulation. More recently, it has been appreciated that the extra-follicular ovarian environment may have important direct or indirect impacts on the developing gamete, and age-dependent changes include increased fibrosis, inflammation, stiffness, and oxidative damage. The cumulus cells and follicular fluid that directly surround the oocyte during its final growth phase within the antral follicle represent additional critical local microenvironments. Here we systematically review the literature and evaluate the studies that investigated the age-related changes in cumulus cells and follicular fluid. Our findings demonstrate unique genetic, epigenetic, transcriptomic, and proteomic changes with associated metabolomic alterations, redox status imbalance, and increased apoptosis in the local oocyte microenvironment. We propose a model of how these changes interact, which may explain the rapid decline in gamete quality with age. We also review the limitations of published studies and highlight future research frontiers.

Analysis and quantification of female and male contributions to the first stages of embryonic kinetics: study from a time-lapse system

PURPOSE

The few studies that examined the effect of male and/or female features on early embryo development, notably using the time-lapse system (TL), reported conflicting results. This can be explained by the small number of studies using an adapted model.

METHODS

We used two original designs to study the female and male effects on embryo development: (1) based on embryos from donor oocytes (TL-DO), and (2) from donor sperm (TL-DS). Firstly, we analyzed the female and male similarities using an ad hoc intraclass correlation coefficient (ICC), then we completed the analysis with a multivariable model to assess the association between both male and female factors, and early embryo kinetics. A total of 572 mature oocytes (TL-DO: 293; TL-DS: 279), fertilized by intracytoplasmic sperm injection (ICSI) and incubated in a TL (Embryoscope®) were included from March 2013 to April 2019; 429 fertilized oocytes (TL-DO: 212; TL-DS: 217) were assessed. The timings of the first 48 h have been analyzed.

RESULTS

The similarities in the timings thought to be related to the female component were significant: (ICC in both DO-DS designs respectively: tPB2: 9-18%; tPNa: 16-21%; tPNf: 40-26%; t2: 38-24%; t3: 15-20%; t4: 21-32%). Comparatively, those related to male were lower. Surprisingly after multivariable analyses, no intrinsic female factors were clearly identified. However, in TL-DO design, oligozoospermia was associated with a tendency to longer timings, notably for tPB2 (p = 0.026).

CONCLUSION

This study quantifies the role of the oocyte in the first embryo cleavages, but without identified specific female factors. However, it also highlights that sperm may have an early embryonic effect.

Cell-Free Fat Extract Improves Ovarian Function and Fertility in Mice With Advanced Age

The reduction in the quantity and quality of oocytes is the major factor affecting fertility in women with advanced age, who tend to experience delayed childbearing and declined fertility rate. However, effective therapeutic strategies to combat this decrease in ovarian function are lacking in clinical practice. Thus, identifying a new method to rescue ovarian function and improve reproduction in natural age-related decline in fertility is necessary. Cell-free fat extract (CEFFE) has been verified to possess diverse active proteins exerting anti-aging and proliferation-promoting effects. Nonetheless, whether CEFFE can rescue the decline in aged-related ovarian function and improve the fertility of females with advanced age remains unclear. In this study, a natural aging mouse model, exhibiting similarities to the physiological changes of ovarian senescence, was used to observe the anti-aging effect of CEFFE on ovarian functions. We found that CEFFE, injected via the veins, could recover the levels of the sex hormone, increase angiogenesis and the number of growth follicles in the natural aging mice model. Moreover, CEFFE promoted the development of embryos and increased the litter size of aged mice. Transcriptome analysis of the aged mouse ovaries revealed that CEFFE treatment upregulated the expression of genes involved in the repair of DNA damage. And both in vivo and in vitro experiment proved that CEFFE improved the function of granulosa cells, including promoting proliferation, alleviating senescence, and rescuing DNA damage in aged granulosa cells. Collectively, our study implied that CEFFE improved the ovarian function and fertility of naturally aging mice by ameliorating the overall microenvironment of ovary, which provided a theoretical basis for new anti-aging therapeutic strategies for cell-free therapy in ovaries.

CDC26 is a key factor in human oocyte aging

STUDY QUESTION

Is CDC26 a key factor in human oocyte aging?

SUMMARY ANSWER

The lack of CDC26 disrupts the oocytes maturation process, leading to oocyte aging, but these defects could be partially rescued by overexpression of the CDC26 protein.

WHAT IS KNOWN ALREADY

Age-related oocyte aging is the main cause of female fertility decline. In mammalian oocytes, aberrant meiosis can cause chromosomal abnormalities that might lead to infertility and developmental disorders. CDC26 participates in the meiosis process.

STUDY DESIGN, SIZE, DURATION

Differential gene expression in young and old women oocytes were screened by single-cell RNA-seq technology, and the functions of differentially genes were verified on mouse oocytes. Finally, transfection technology was used to evaluate the effect of a differentially expressed gene in rescuing human oocyte from aging.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Discarded human oocytes were collected for single-cell RNA-seq, q-PCR and immunocytochemical analyses to screen for and identify differential gene expression. Female KM mice oocytes were collected for IVM of oocytes, q-PCR and immunocytochemical analyses to delineate the relationships between oocyte aging and differential gene expression. Additionally, recombinant lentiviral vectors encoding CDC26 were transfected into the germinal vesicle oocytes of older women, to investigate the effects of the CDC26 gene expression on oocyte development.

MAIN RESULTS AND THE ROLE OF CHANCE

Many genes were found to be differentially expressed in the oocytes of young versus old patients via RNA-seq technology. CDC26 mRNA and protein levels in aged oocytes were severely decreased, when compared with the levels observed in young oocytes. Moreover, aged oocytes lacking CDC26 were more prone to aneuploidy. These defects in aged oocytes could be partially rescued by overexpression of the CDC26 protein.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Our study delineated key steps in the oocyte aging process by identifying the key role of CDC26 in the progression of oocyte maturation. Future studies are required to address whether other signaling pathways play a role in regulating oocyte maturation via CDC26 and which genes are the direct molecular targets of CDC26.

WIDER IMPLICATIONS OF THE FINDINGS

Our results using in vitro systems for both mouse and human oocyte maturation provide a proof of principle that CDC26 may represent a novel therapeutic approach against maternal aging-related spindle and chromosomal abnormalities.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by grants from the National Natural Science Foundation of China (81571442 and 81170571), the outstanding Talent Project of Shanghai Municipal Commission of Health (XBR2011067) and Clinical Research and Cultivation Project in Shanghai Municipal Hospitals (SHDC12019X32). The authors declare no conflict of interest.

Stress Management during the Intracytoplasmic Sperm Injection Cycle May Slow Down First Embryo Cleavage and Accelerate Embryo Compaction: A Pilot Randomized Controlled Trial

INTRODUCTION

A firm consensus on the effectiveness of psychological interventions during infertility treatment has not been reached yet in terms of mental health and pregnancy rates. Moreover, the influence of these interventions on embryo cleavage kinetics has not been investigated.

OBJECTIVE

The aim of this work was to study whether stress management in couples undergoing an intracytoplasmic sperm injection (ICSI) cycle influences stress levels, mitochondrial DNA (mtDNA) levels in granulosa cells, and cleavage-stage embryos.

METHODS

Infertile couples were randomized into a treatment as usual (TAU) group (n = 30) and stress management program (SMP) group (n = 29) at the beginning of an ICSI cycle. Couples in the SMP group attended education and relaxation sessions at each visit to the clinic for folliculometry. The perceived stress scale (PSS) was used to assess stress levels at the beginning and end of the cycle. Moreover, mtDNA levels of granulosa cells and embryo morphokinetics were evaluated.

RESULTS

Post-intervention, women in the SMP group had significantly lower PSS scores than their initial PSS (p < 0.001; effect size, ES = 0.5) and than the final PSS of the TAU group (p = 0.02; ES = 0.09). Additionally, mtDNA levels were significantly lower in luteal granulosa cells of the SMP group than the TAU group (p = 0.02). An earlier time of pronuclei appearance (p = 0.03) and time to 2 cells (p = 0.015) and a faster time to full compaction (p = 0.045) were detected in the embryos of the SMP group compared with the TAU group.

CONCLUSION(S)

The implemented program may reduce stress levels, retard first embryo cleavage, and accelerate embryo compaction. Further studies with an active control group are needed to confirm these results.

Reproductive senescence impairs the energy metabolism of human luteinized granulosa cells

RESEARCH QUESTION

Female age is the single greatest factor influencing reproductive performance and granulosa cells are considered as potential biomarkers of oocyte quality. Is there an age effect on the energy metabolism of human mural granulosa cells?

DESIGN

Observational prospective cohort and experimental study including 127 women who had undergone IVF cycles. Women were allocated to two groups: a group of infertile patients aged over 38 years and a control group comprising oocyte donors aged less than 35 years. Individuals with pathologies that could impair fertility were excluded from both groups. Following oocyte retrieval, cumulus and granulosa cells were isolated and their bioenergetic properties (oxidative phosphorylation parameters, rate of aerobic glycolysis and adenine nucleotide concentrations) were analysed and compared.

RESULTS

Human mural luteinized granulosa and cumulus cells present high rates of aerobic glycolysis that cannot be increased further when mitochondrial ATP synthesis is inhibited. Addition of follicular fluid to the experimental media is necessary to reach the full respiratory capacity of the cells. Granulosa cells from aged women present lower mitochondrial respiration (12.8 ± 1.6 versus 11.2 ± 1.6 pmol O₂/min/mg; P = 0.046), although mitochondrial mass is not decreased, and lower aerobic glycolysis, than those from young donors (12.9 ± 1.3 versus 10.9 ± 0.5 mpH/min/mg; P = 0.009). The concurrent decrease in the two energy supply pathways leads to a decrease in the cellular energy charge (0.87 ± 0.01 versus 0.83 ± 0.02; P < 0.001).

CONCLUSIONS

Human mural luteinized granulosa cells exhibit a reduction in their energy metabolism as women age that is likely to influence female reproductive potential.

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

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