Significantly lengthened telomere in granulosa cells from women with polycystic ovarian syndrome (PCOS)

Leptin Modulates Ovarian Granulosa Cell Apoptosis by Regulating Telomerase Activity and Telomere Length in Polycystic Ovary Syndrome

Leptin (LEP) is implicated in the pathogenesis of polycystic ovary syndrome (PCOS). This study investigates the mechanism of LEP in PCOS. The baseline information of 80 PCOS patients and matched controls was analyzed, with serum and follicular fluid (FF) LEP and LEP receptor (LEPR) levels, telomerase activity, and relative telomere length (TL) measured. The correlation of FF LEP with telomerase activity and TL was analyzed. The viability and apoptosis of KGN cells (the ovarian granulosa cells) treated with gradient LEP were assessed. LEP-LEPR interaction was examined. LEPR, v-myc avian myelocytomatosis viral oncogene homolog (c-MYC), and telomerase reverse transcriptase (TERT) levels and c-MYC protein expression in the TERT promoter region were determined. Nuclear c-MYC translocation was detected. LEP was upregulated in sera and FF of PCOS patients. FF LEP positively correlated with telomerase activity and TL. Low-concentration LEP facilitated KGN cell proliferation, and high-concentration LEP dose-dependently suppressed cell proliferation, promoted apoptosis, upregulated LEPR, and increased telomerase activity and relative TL. LEP-LEPR interaction upregulated c-MYC and facilitated its nuclear accumulation. c-MYC enrichment in the TERT promoter region upregulated TERT, altering telomerase activity and TL and inducing cell apoptosis. Briefly, LEP/LEPR activates c-MYC, modulates TERT expression, and increases telomerase activity and TL, thus inducing ovarian granulosa cell apoptosis and participating in PCOS.

Association of polycystic ovary syndrome with endothelial health, cardiovascular risk, and cellular aging

OBJECTIVE

To study measures of endothelial health, cardiovascular risk, and cellular aging between patients with polycystic ovary syndrome (PCOS) and a reproductive age normative cohort.

DESIGN

Cross-sectional study.

SUBJECTS

Community-based patients with PCOS and a normative ovarian aging cohort as controls, aged ≤45 years at the time of evaluation.

EXPOSURE

Noninvasive measure of endothelial health measured by the EndoPAT reactive hyperemia index.

MAIN OUTCOME MEASURES

Reactive hyperemia index as measure of endothelial health. The secondary outcomes included Framingham score, telomere length, and mitochondrial deoxyribonucleic acid copy number from leukocyte cells.

RESULTS

Our cohort included 63 participants with PCOS and 130 non-PCOS participants. The mean age was significantly lower in the PCOS cohort (33.1; standard deviation, 4.7 years) than in the non-PCOS cohort (40.8; standard deviation, 2.9 years). In multivariable-adjusted models, we found that PCOS was significantly associated with endothelial dysfunction as both categorical (odds ratio for PCOS, 0.31; 95% confidence interval [CI], 0.10-0.97) and continuous (PCOS coefficient, -0.37; 95% CI, -0.69 to -0.05) outcomes. For secondary outcomes, PCOS status was not significantly associated with mitochondrial deoxyribonucleic acid (PCOS coefficient, -48.1; 95% CI, -175.0 to 78.9), telomere length (PCOS coefficient, 0.05; 95% CI, -0.05 to 0.15), Framingham score (PCOS coefficient, 0.002; 95% CI, -0.01 to 0.02), or metabolic syndrome (odds ratio for PCOS, 1.29; 95% CI, 0.31-5.44).

CONCLUSION

Our findings suggest that patients with PCOS have impaired endothelial function compared with non-PCOS patients, although measures of cellular aging and cardiovascular risk as measured by the Framingham score did not differ between the cohorts.

The mechanism of NF-κB-TERT feedback regulation of granulosa cell apoptosis in PCOS rats

Patients with Polycystic ovary syndrome (PCOS) have chronic low-grade ovarian inflammation. Inflammation can cause telomere dysfunction, and telomere and telomerase complex are also involved in regulating inflammation. However, the specific mechanisms of inflammatory signaling feedback and telomere-telomerase mutual regulation remain to be discovered. This study elucidates the role of Nuclear factor kappa-B (NF-κB)-Telomerase reverse transcriptase (TERT) feedback in PCOS granulosa cell apoptosis. Using letrozole and a high-fat diet, a PCOS rat model was established, along with a Lipopolysaccharide (LPS) -treated KGN cell inflammation model was established. NF-κB and TERT inhibitors (BAY 11-7082 and BIBR1532) were then administered to LPS-induced KGN cells. PCOS rats displayed disrupted estrous cycles, increased weight, elevated serum testosterone, cystic follicles, granulosa cell layer thinning, and reduced corpora lutea count (P are all less than 0.05). In PCOS rat ovaries, NF-κB, Interleukin-6 (IL-6), Tumor Necrosis Factor α (TNF-α), TERT, Bax, and Caspase-3 exhibited notable upregulation, while Bcl-2 decreased, with telomere elongation (P are all less than 0.05). There were significant correlations among NF-κB-related inflammatory factors, TERT and apoptotic factors, and they were positively correlated with Bax and Caspase-3, and negatively correlated with Bcl-2 (P are all less than 0.05). LPS-treated KGN cells demonstrated increased expression of inflammatory and pro-apoptotic factors, later restored post-treatment with NF-κB and TERT inhibitors (P are all less than 0.05). In conclusion, TERT may induce granulosa cell apoptosis by participating in the regulation of the NF-κB signaling pathway, thereby mediating the chronic inflammatory response of PCOS through downstream inflammatory factors IL-6 and TNF-α.

Telomeres and SIRT1 as Biomarkers of Gamete Oxidative Stress, Fertility, and Potential IVF Outcome

The number of infertile couples undergoing in vitro fertilisation (IVF) has increased significantly. The efficacy of this procedure is contingent upon a multitude of factors, including gamete quality. One factor influencing gamete quality is oxidative stress, which leads to telomere damage and accelerates cellular ageing. Identifying new biomarkers that can predict the success of assisted reproduction techniques is a current relevant area of research. In this review, we discuss the potential role of SIRT1, a protein known to protect against oxidative stress and telomeres, which are responsible for genome stability, as biomarkers of gamete quality and assisted reproduction technique outcomes.

Causal association between telomere length and female reproductive endocrine diseases: a univariable and multivariable Mendelian randomization analysis

BACKGROUND

The relationship between leukocyte telomere length (LTL) and female reproductive endocrine diseases has gained significant attention and research interest in recent years. However, there is still limited understanding of the exact impacts of LTL on these diseases. Therefore, the primary objective of this study was to investigate the genetic causal association between LTL and female reproductive endocrine diseases by employing Mendelian randomization (MR) analysis.

METHODS

Instruments for assessing genetic variation associated with exposure and outcome were derived from summary data of published genome-wide association studies (GWAS). Inverse-variance weighted (IVW) was utilized as the main analysis method to investigate the causal relationship between LTL and female reproductive endocrine diseases. The exposure data were obtained from the UK Biobanks GWAS dataset, comprising 472,174 participants of European ancestry. The outcome data were acquired from the FinnGen consortium, including abnormal uterine bleeding (menorrhagia and oligomenorrhea), endometriosis (ovarian endometrioma and adenomyosis), infertility, polycystic ovary syndrome (PCOS), premature ovarian insufficiency (POI) and premenstrual syndrome (PMS). Furthermore, to account for potential confounding factors such as smoking, alcohol consumption, insomnia, body mass index (BMI) and a history of pelvic inflammatory disease (PID), multivariable MR (MVMR) analysis was also conducted. Lastly, a series of pleiotropy tests and sensitivity analyses were performed to ensure the reliability and robustness of our findings. P < 0.0063 was considered to indicate statistically significant causality following Bonferroni correction.

RESULTS

Our univariable MR analysis demonstrated that longer LTL was causally associated with an increased risk of menorrhagia (IVW: odds ratio [OR]: 1.1803; 95% confidence interval [CI]: 1.0880-1.2804; P = 0.0001) and ovarian endometrioma (IVW: OR: 1.2946; 95%CI: 1.0970-1.5278; P = 0.0022) at the Bonferroni significance level. However, no significant correlation was observed between LTL and oligomenorrhea (IVW: OR: 1.0124; 95%CI: 0.7350-1.3946; P = 0.9398), adenomyosis (IVW: OR: 1.1978; 95%CI: 0.9983-1.4372; P = 0.0522), infertility (IVW: OR: 1.0735; 95%CI: 0.9671-1.1915; P = 0.1828), PCOS (IVW: OR: 1.0633; 95%CI: 0.7919-1.4278; P = 0.6829), POI (IVW: OR: 0.8971; 95%CI: 0.5644-1.4257; P = 0.6459) or PMS (IVW: OR: 0.7749; 95%CI: 0.4137-1.4513; P = 0.4256). Reverse MR analysis indicated that female reproductive endocrine diseases have no causal effect on LTL. MVMR analysis suggested that the causal effect of LTL on menorrhagia and ovarian endometrioma remained significant after accounting for smoking, alcohol consumption, insomnia, BMI and a history of PID. Pleiotropic and sensitivity analyses also showed robustness of our results.

CONCLUSION

The results of our bidirectional two-sample MR analysis revealed that genetically predicted longer LTL significantly increased the risk of menorrhagia and ovarian endometrioma, which is consistent with the findings from MVMR studies. However, we did not notice any significant effects of LTL on oligomenorrhea, adenomyosis, infertility, PCOS, POI or PMS. Additionally, reproductive endocrine disorders were found to have no impact on LTL. To enhance our understanding of the effect and underlying mechanism of LTL on female reproductive endocrine diseases, further large-scale studies are warranted in the future.

Chromosome ends and the theory of marginotomy: implications for reproduction

Telomeres are the protective structures located at the ends of linear chromosomes. They were first described in the 1930s, but their biology remained unexplored until the early 70s, when Alexey M. Olovnikov, a theoretical biologist, suggested that telomeres cannot be fully copied during DNA replication. He proposed a theory that linked this phenomenon with the limit of cell proliferation capacity and the "duration of life" (theory of marginotomy), and suggested a potential of telomere lenghthening for the prevention of aging (anti-marginotomy). The impact of proliferative telomere shortening on life expectancy was later confirmed. In humans, telomere shortening is counteracted by telomerase, an enzyme that is undetectable in most adult somatic cells, but present in cancer cells and adult and embryonic stem and germ cells. Although telomere length dynamics are different in male and female gametes during gametogenesis, telomere lengths are reset at the blastocyst stage, setting the initial length of the species. The role of the telomere pathway in reproduction has been explored for years, mainly because of increased infertility resulting from delayed childbearing. Short telomere length in ovarian somatic cells is associated to decreased fertility and higher aneuploidy rates in embryos. Consequently, there is a growing interest in telomere lengthening strategies, aimed at improving fertility. It has also been observed that lifestyle factors can affect telomere length and improve fertility outcomes. In this review, we discuss the implications of telomere theory in fertility, especially in oocytes, spermatozoa, and embryos, as well as therapies to enhance reproductive success.

Alteration of relative telomere length and telomerase reverse transcriptase expression in the granulosa cells of women during aging and assessment of in vitro fertilization outcomes

Telomere attrition plays a critical role in the reproductive aging process in humans. Telomere length (TL) is typically regulated by telomerase, the main component of which is telomerase reverse transcriptase (TERT). The aim of the present study was to investigate the changes of relative TL (RTL) and TERT expression in granulosa cells (GCs) during aging and its association with reproduction. Clinical data on the frozen‑thawed embryo transfer cycles of older (>35 year old) and younger (≤35 year old) women from a single center over a 3‑year period were retrospectively analyzed. Preimplantation genetic testing for chromosome aneuploidies in older women during the same period was also analyzed. Following the analysis of the data, several biological characteristics of senescent GCs were explored. In addition, a total of 160 women who were undergoing their first fresh cycle of in vitro fertilization (IVF) or intracytoplasmic sperm injection were included in the study. GCs were collected from all participants. The changes of RTL and TERT expression in GCs during aging were investigated using quantitative PCR and western blotting. The associations of RTL and TERT with IVF outcomes were also assessed. The clinical data demonstrated that the pregnancy and live birth rates of women aged >35 years were ~20% lower than those of women aged ≤35 years, and the number of embryos with aneuploidy was 7‑fold of that without euploidy in the older age group. An aging‑induced change in follicle stimulating hormone receptor expression was observed. A shorter TL and increased TERT expression were detected in the older women. A significant inverse correlation between the expression levels of TERT and oocyte yield was identified. However, no association of RTL and TERT with blastocyst formation rate and the probability of clinical pregnancy was detected. It may be concluded that RTL and TERT alterations in GCs are potential determinants of ovarian aging. TERT expression in GCs appears to be a potential biomarker for the prediction of ovarian response, which provides a novel strategy for the assessment of female fertility.

Significantly shortened telomere length and altered androgen receptor level in cumulus cells from women with polycystic ovary syndrome

OBJECTIVE

The aim of this study was to investigate the correlation between hormone receptor levels and telomere length (TL) in infertile women with and without polycystic ovary syndrome (PCOS).

MATERIALS AND METHODS

This prospective cohort study recruited a total of 431 cumulus oocyte complex (COC) from 88 infertile women between July 2012 and June 2014. The participants were divided into three groups: young age (<38 years, n = 42 and 227 COC), advanced age (≥38 years, n = 33 and 107 COC) and PCOS patients (n = 13 and 97 COC). Cumulus cells were collected from individual follicle during oocyte pick-up, and the mRNA levels of hormone receptors and TL were measured using real-time PCR.

RESULTS

The cumulus cells of PCOS patients demonstrated lower mRNA levels of LH receptor (75.57 ± 138.10 vs. 171.07 ± 317.68; p < 0.01) and androgen receptor (1.13 ± 1.52 vs. 4.08 ± 9.57; p < 0.01), as well as a shorter TL (2.39 ± 2.58 vs. 3.96 ± 4.72; p < 0.01) compared to those of the young age group. In the young age group, only androgen receptor mRNA level showed a significant association with TL (rho = 0.148, p = 0.026), while FSH receptor mRNA level was the only factor associated with TL (rho = 0.247, p = 0.015) in PCOS patients. For advanced-aged patients, no significant relationship was observed between hormone receptor mRNA levels and TL. Alternative splicing of androgen receptors was identified in some PCOS patients but not in young age controls.

CONCLUSION

The findings suggest that the androgen receptor level and function may be altered in the cumulus cells of PCOS patients, leading to a shorter TL in cumulus cells in PCOS patients.

Telomere Length and Telomerase Activity of Granulosa Cells and Follicular Fluid in Women Undergoing In Vitro Fertilization

This study aimed to evaluate the interrelationship between telomere length, telomerase activity and oxidative DNA damage in patients undergoing in vitro fertilization (IVF). This single-center, observational clinical study comprised 102 unselected, consecutive patients with various infertility diagnoses. Granulosa cells (GCs) and follicular fluid (FF) were analyzed simultaneously for telomere functions and for the marker of oxidative DNA damage, 8-hydroxy-2-deoxyguanosine (8-OHdG). An Absolute Human Telomere Lengths Quantification qPCR Assay kit and Telomerase Activity Quantification qPCR Assay kit (Nucleotestbio, Budapest, Hungary), as well as an 8-OHdG ELISA kit (Abbexa Ltd., Cambridge, United Kingdom) were used for analyses. Similar telomere lengths were found in GCs and FF, however telomerase activity was markedly depressed, while 8-OHdG levels were markedly elevated in FF compared with those in GCs (p < 0.01). Telomere lengths were independent of telomerase activity both in GCs and FF. However, GC 8-OHdG was inversely related to telomerase activity in GCs and FF (p < 0.05). Importantly, 8-OHdG levels both in GCs and FF had significant negative impact on the number of the retrieved and MII oocytes (p < 0.01), whereas FF 8-OHdG was negatively related further to the number of fertilized oocytes and blastocysts (p < 0.01). In conclusion, we could not confirm the direct association of telomere function and reproductive potential. However, oxidative DNA damage, as mainly reflected by 8-OHdG, adversely affected early markers of IVF outcome and clinical pregnancies.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Sperm telomeres, oxidative stress, and infertility

In brief

Oxidative stress is recognized as an underlying driving factor of both telomere dysfunction and human subfertility/infertility. This review briefly reassesses telomere integrity as a fertility biomarker before proposing a novel, mechanistic rationale for the role of oxidative stress in the seemingly paradoxical lengthening of sperm telomeres with aging.

Abstract

The maintenance of redox balance in the male reproductive tract is critical to sperm health and function. Physiological levels of reactive oxygen species (ROS) promote sperm capacitation, while excess ROS exposure, or depleted antioxidant defenses, yields a state of oxidative stress which disrupts their fertilizing capacity and DNA structural integrity. The guanine moiety is the most readily oxidized of the four DNA bases and gets converted to the mutagenic lesion 8-hydroxy-deoxyguanosine (8-OHdG). Numerous studies have also confirmed oxidative stress as a driving factor behind accelerated telomere shortening and dysfunction. Although a clear consensus has not been reached, clinical studies also appear to associate telomere integrity with fertility outcomes in the assisted reproductive technology setting. Intriguingly, while sperm cellular and molecular characteristics make them more susceptible to oxidative insult than any other cell type, they are also the only cell type in which telomere lengthening accompanies aging. This article focuses on the oxidative stress response pathways to propose a mechanism for the explanation of this apparent paradox.

Polycystic ovary syndrome and leukocyte telomere length: cross-sectional and longitudinal changes

OBJECTIVE

Telomeres are DNA-protein complexes that protect chromosome ends from DNA damage and are surrogate biomarkers of cellular aging. Current evidence, almost entirely from cross-sectional observations, supports negative associations between leukocyte telomere length (LTL) and adverse lifestyle factors and cardiometabolic risk factors. Polycystic ovary syndrome (PCOS), the most common gynecological endocrine disorder, is associated with inflammation and oxidative stress, both factors associated with accelerated telomere attrition. We therefore hypothesized that LTL would be shorter and decrease more rapidly in women with PCOS in comparison to a control population.

DESIGN

This is a population-based cohort study comprising women of Northern Finland Birth Cohort 1966, with clinical examinations at ages 31 and 46. The sample included self-reported PCOS (age 31, n = 190; age 46, n = 207) and referent women (age 31, n = 1054; age 46, n = 1324) with data on LTL.

METHODS

The association between LTL and PCOS at ages 31 and 46 was analyzed by linear regression models adjusted for BMI, smoking, alcohol consumption and socioeconomic status at the corresponding age.

RESULTS

Women with PCOS had similar mean LTL at ages 31 and 46 (P > 0.4 for both). The mean LTL change between ages 31 and 46 did not differ between groups (P = 0.19). However, we observed a significant LTL attrition between ages 31 and 46 in the reference population (P < 0.001), but not in women with PCOS (P = 0.96).

CONCLUSIONS

This finding may suggest a difference in the LTL attrition rate in women with PCOS, an unexpected finding that might affect their risk of age-related disease. Further research is needed to clarify the underlying mechanisms.

The effect of metformin treatment on leukocyte telomere length in patients with polycystic ovary syndrome: a prospective case-control study

PURPOSE

The study aimed to investigate the effect of metformin treatment on leukocyte telomere length (LTL) and the relationship of LTL with C-reactive protein (CRP), homocysteine, albumin, complete blood count, and HOMA-IR values in patients with polycystic ovary syndrome (PCOS).

MATERIAL AND METHOD

A prospective case-control study consisting of 30 women with PCOS and 30 healthy women without PCOS was performed. The relationship between clinical and laboratory parameters and LTL was analyzed. PCOS patients were treated with metformin (850 mg/day) for three months. Before treatment (BT) and after treatment (AT), each patient's LTL was evaluated and compared with the control group.

RESULTS

In the comparison between PCOS and control groups, the difference was significant for LTL, age, body mass index (BMI), and CRP (p = 0.002; p < 0.001; p = 0.001; p = 0.01, respectively). In PCOS patients, the difference between BT and AT, LTL was not statistically significant (BT: 6.06 ± 2.12; AT: 6.30 ± 1.93; p = 0.623; 95% C.I: - 1.22-0.74); however, the difference for weight was significant (BT: 83.78 ± 15.31; AT: 80.62 ± 15.40; p = 0.02; 95% CI: 1.34-4.99). The logistic regression model established by BMI (group 1: 21-24, group 2: 24-29, group 3: 29-34, group 4: > 34), age, and RDW, which predicted the PCOS group by affecting the LTL level, was statistically significant (p < 0.001/PPV = 96.3%; NPV = 88.5%). Each unit reduction in telomere length increased women's probability of PCOS by 0.4 times (p = 0.013; OR = 0.419, 95% CI: 0.211-0.835).

CONCLUSION

Although statistically insignificant, LTL increased after metformin use in PCOS patients, and the mean weight loss reduction was statistically significant. Telomere shortening increased the likelihood of PCOS 0.4 times.

Leukocyte telomere length in women with and without polycystic ovary syndrome: a systematic review and meta-analysis

AIM

To study the telomere length and the telomerase activity in women with and without polycystic ovary syndrome (PCOS).

METHODS

Relevant studies were searched from PubMed, Embase, and LILACS online databases and manual screening. The mean differences (MDs) or standardized MDs (SMDs) with their 95% confidence intervals (CIs) were calculated. The methodological quality of included studies was evaluated with the Newcastle-Ottawa Scale (NOS), and heterogeneity with the I² and Tau² statistics.

RESULTS

Six studies including 2109 non-pregnant women with (n = 1155) or without (n = 954) PCOS assessed leukocyte telomere length. There was a non-significant leukocyte telomere length difference (SMD = 0.25, 95% CI: -0.01, 0.51, p = .06, I² = 81%, Tau² = 0.08) comparing PCOS patients with the control group. Studied PCOS women were younger (MD = -1.39, 95% CI: -2.47, -0.31 years, I² = 83%), and had higher body mass index (BMI; MD = 3.66, 95% CI: 2.11, 5.20 kg/m², I² = 94%). There were significantly higher testosterone (SMD = 0.88, 95% CI: 0.65, 1.10) and luteinizing hormone levels (SMD = 0.60, 95% CI: 0.12, 1.08) in women with PCOS as compared to controls. There was a low risk of bias and there were not sufficient studies to meta-analyze other cell types.

CONCLUSIONS

Leukocyte telomere length did not differ between women with and without PCOS. Further studies with large sample sizes and including other outcomes are warranted to further substantiate the reported evidence.

Transcriptomic landscape of granulosa cells and peripheral blood mononuclear cells in women with PCOS compared to young poor responders and women with normal response

STUDY QUESTION

Are transcriptomic profiles altered in ovarian granulosa cells (GCs) and peripheral blood mononuclear cells (PBMNCs) of women with polycystic ovary syndrome (PCOS) compared to young poor responders (YPR) and women with normal response to ovarian stimulation?

SUMMARY ANSWER

RNA expression profiles in ovarian GCs and PBMNCs were significantly altered in patients with PCOS compared with normoresponder controls (CONT) and YPR.

WHAT IS KNOWN ALREADY

PCOS is characterised by a higher number of follicles at all developmental stages. During controlled ovarian hyperstimulation, PCOS women develop a larger number of follicles as a result of an exacerbated response, with an increased risk of ovarian hyperstimulation syndrome. Despite the number of developing follicles, they are often heterogeneous in both size and maturation stage, with compromised quality and retrieval of immature oocytes. Women with PCOS appear to have a longer reproductive lifespan, with a slightly higher menopausal age than the general population, in addition to having a higher antral follicular count. As a result, the ovarian follicular dynamics appear to differ significantly from those observed in women with poor ovarian response (POR) or diminished ovarian reserve.

STUDY DESIGN, SIZE, DURATION

Transcriptomic profiling with RNA-sequencing and validation using quantitative reverse transcription PCR (qRT-PCR). Women with PCOS (N = 20), YPR (N = 20) and CONT (N = 20). Five patients for each group were used for sequencing and 15 samples per group were used for validation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

PCOS was defined using the revised Rotterdam diagnostic criteria for PCOS. The YPR group included women <35 years old with <4 mature follicles (at least 15 mm) on the day of the trigger. According to internal data, this group represented the bottom 15th percentile of patients' responses in this age group. It was consistent with Patient-Oriented Strategies Encompassing Individualize D Oocyte Number (POSEIDON) criteria for POR (Group 3). The young CONT group included women <35 years without PCOS or anovulation, who developed >14 mature follicles (at least 15 mm on transvaginal ultrasound). According to internal data, a threshold of >14 mature follicles was established to represent the top 25% of patients in this age group in this clinic.

Overall, n = 60 GCs and PBMNCs samples were collected and processed for total RNA extraction. To define the transcriptomic cargo of GCs and PBMNCs, RNA-seq libraries were successfully prepared from samples and analysed by RNA-seq analysis. Differential gene expression analysis was used to compare RNA-seq results between different groups of samples. Ingenuity pathway analysis was used to perform Gene Ontology and pathways analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

In PBMNCs of PCOS, there were 65 differentially expressed genes (DEGs) compared to CONT, and 16 compared to YPR. In GCs of PCOS, 4 genes showed decreased expression compared to CONT, while 58 genes were differentially expressed compared to YPR. qRT-PCR analysis confirmed the findings of the RNA-seq. The functional enrichment analysis performed revealed that DEGs in GCs of PCOS compared to CONT and YPR were prevalently involved in protein ubiquitination, oxidative phosphorylation, mitochondrial dysfunction and sirtuin signaling pathways.

LARGE SCALE DATA

The data used in this study is partially available at Gene Ontology database.

LIMITATIONS, REASONS FOR CAUTION

The analysis in PBMNCs could be uninformative due to inter-individual variability among patients in the same study groups. Despite the fact that we considered this was the best approach for our study's novel, exploratory nature.

WIDER IMPLICATIONS OF THE FINDINGS

RNA expression profiles in ovarian GCs and PBMNCs were altered in patients with PCOS compared with CONT and YPR. GCs of PCOS patients showed altered expression of several genes involved in oxidative phosphorylation, mitochondrial function and sirtuin signaling pathways. This is the first study to show that the transcriptomic landscape in GCs is altered in PCOS compared to CONT and YPR.

STUDY FUNDING/COMPETING INTEREST(S)

This study was partially supported by grant PI18/00322 from Instituto de Salud Carlos III, and European Regional Development Fund (FEDER), ‘A way to make Europe’ awarded to S.H. M.C., S.H., S.T., L.R., M.R., I.R., A.P. and R.C. declare no conflict of interests concerning this research. E.S. is a consultant for and receives research funding from the Foundation for Embryonic Competence.

TRIAL REGISTRATION NUMBER

N/A.

Roles of Noncoding RNA in Reproduction

The World Health Organization predicts that infertility will be the third major health threat after cancer and cardiovascular disease, and will become a hot topic in medical research. Studies have shown that epigenetic changes are an important component of gametogenesis and related reproductive diseases. Epigenetic regulation of noncoding RNA (ncRNA) is appropriate and is a research hotspot in the biomedical field; these include long noncoding RNA (lncRNA), microRNA (miRNA), and PIWI-interacting RNA (piRNA). As vital members of the intracellular gene regulatory network, they affect various life activities of cells. LncRNA functions as a molecular bait, molecular signal and molecular scaffold in the body through molecular guidance. miRNAs are critical regulators of gene expression; they mainly control the stability or translation of their target mRNA after transcription. piRNA functions mainly through silencing genomic transposable elements and the post-transcriptional regulation of mRNAs in animal germ cells. Current studies have shown that these ncRNAs also play significant roles in the reproductive system and are involved in the regulation of essential cellular events in spermatogenesis and follicular development. The abnormal expression of ncRNA is closely linked to testicular germ cell tumors, poly cystic ovary syndrome and other diseases. This paper briefly presents the research on the reproductive process and reproductive diseases involving ncRNAs.

Insights into the Role of Telomeres in Human Embryological Parameters. Opinions Regarding IVF

Telomeres promote genome integrity by protecting chromosome ends from the activation of the DNA damage response and protecting chromosomes from the loss of coding sequences due to the end replication problem. Telomere length (TL) is progressively shortened as age progresses, thus resulting in cellular senescence. Therefore, TL is in strong adverse linear correlation with aging. Mounting evidence supports the notion that telomeres and male/female infertility are in a close relationship, posing the biology of telomeres as a hot topic in the era of human-assisted reproduction. Specifically, the length of sperm telomeres is gradually increasing as men get older, while the telomere length of the oocytes seems not to follow similar patterns with that of sperm. Nonetheless, the telomere length of the embryos during the cleavage stages seems to have a paternal origin, but the telomere length can be further extended by telomerase activity during the blastocyst stage. The latter has been proposed as a new molecular biomarker with strong predictive value regarding male infertility. As far as the role of telomeres in assisted reproduction, the data is limited but the length of telomeres in both gametes seems to be affected mainly by the cause of infertility rather than the assisted reproductive therapy (ART) procedure itself. The present review aims to shed more light into the role of telomeres in human embryological parameters, including gametes and embryos and also presents opinions regarding the association between telomeres and in vitro fertilization (IVF).

Short-Term Aerobic Exercise Did Not Change Telomere Length While It Reduced Testosterone Levels and Obesity Indexes in PCOS: A Randomized Controlled Clinical Trial Study

Metabolic and hormonal outcomes of polycystic ovary syndrome (PCOS) have implications on telomere biology and physical activity may prevent telomere erosion. We sought to observe the effects of continuous (CAT) and intermittent (IAT) aerobic training on telomere length, inflammatory biomarkers, and its correlation with metabolic, hormonal, and anthropometric parameters of PCOS. This randomized controlled clinical trial study included 87 PCOS randomly stratified according to body mass index (BMI) in CAT (n = 28), IAT (n = 29) and non-training control group (CG, n = 30). The exercises were carried out on a treadmill, three times per week for 16 weeks. The participants' anthropometric characteristics and biochemical and hormonal concentrations were measured before and after aerobic training or observation period, as the telomere length that was evaluated using quantitative real-time PCR. Four months of aerobic exercises (CAT or IAT) did not alter telomere length and inflammatory biomarkers in PCOS women. Obesity index as BMI and waist circumference (WC), and inflammatory biomarkers negatively affect telomeres. The hyper-andro-genism measured by testosterone levels was reduced after both exercises (CAT, p ≤ 0.001; IAT, p = 0.019). In particular, the CAT reduced WC (p = 0.045), hip circumference (p = 0.032), serum cholesterol (p ≤ 0.001), and low-density lipoprotein (p = 0.030). Whereas, the IAT decreased WC (p = 0.014), waist-to-hip ratio (p = 0.012), free androgen index (FAI) (p = 0.037). WC (p = 0.049) and body fat (p = 0.015) increased in the non-training group while total cholesterol was reduced (p = 0.010). Booth exercises reduced obesity indices and hyperandrogenism on PCOS women without changes in telomere length or inflammatory biomarkers.

Ovarian Telomerase and Female Fertility

Women's fertility is characterized both quantitatively and qualitatively mainly by the pool of ovarian follicles. Monthly, gonadotropins cause an intense multiplication of granulosa cells surrounding the oocyte. This step of follicular development requires a high proliferation ability for these cells. Telomere length plays a crucial role in the mitotic index of human cells. Hence, disrupting telomere homeostasis could directly affect women's fertility. Strongly expressed in ovaries, telomerase is the most effective factor to limit telomeric attrition and preserve ovarian reserve. Considering these facts, two situations of infertility could be correlated with the length of telomeres and ovarian telomerase activity: PolyCystic Ovary Syndrome (PCOS), which is associated with a high density of small antral follicles, and Premature Ovarian Failure (POF), which is associated with a premature decrease in ovarian reserve. Several authors have studied this topic, expecting to find long telomeres and strong telomerase activity in PCOS and short telomeres and low telomerase activity in POF patients. Although the results of these studies are contradictory, telomere length and the ovarian telomerase impact in women's fertility disorders appear obvious. In this context, our research perspectives aimed to explore the stimulation of ovarian telomerase to limit the decrease in the follicular pool while avoiding an increase in cancer risk.

N6-methyladenosine Demethylase FTO Induces the Dysfunctions of Ovarian Granulosa Cells by Upregulating Flotillin 2

Polycystic ovarian syndrome (PCOS) is often accompanied by overweight/obesity and insulin resistance. The dysfunctions of ovarian granulosa cells (GCs) are closely linked with the pathogenesis of PCOS. Fat mass and obesity-associated gene (FTO), an N6-methyladenosine (m6A) demethylase, has been reported to be implicated in the risks and insulin resistance of PCOS. However, the roles of FTO in the development of GCs along with its m6A-related regulatory mechanisms are poorly defined. Cell proliferative ability was detected by MTT assay. Cell apoptotic rate was measured via flow cytometry. Insulin resistance was assessed by GLUT4 transport potential. The mRNA and protein levels of FTO and flotillin 2 (FLOT2) were determined by RT-qPCR and western blot assays, respectively. FLOT2 was screened out to be a potential FTO target through differential expression analysis for the GSE95728 dataset and target prediction analysis by POSTAR2 and STARBASE databases. The interaction between FTO and FLOT2 was analyzed by RNA immunoprecipitation (RIP) assay. The effect of FTO upregulation on FLOT2 m6A level was measured by methylated RIP (meRIP) assay. FLOT2 mRNA stability was examined by actinomycin D assay. FTO overexpression facilitated cell proliferation, hindered cell apoptosis, and induced insulin resistance in GCs. FTO promoted FLOT2 expression by reducing m6A level on FLOT2 mRNA and increasing FLOT2 mRNA stability. FLOT2 loss weakened the effects of FTO overexpression on cell proliferation/apoptosis and insulin resistance in GCs. FTO induced the dysfunctions of GCs by upregulating FLOT2, suggesting that FTO/FLOT2 might play a role in the pathophysiology of PCOS.

Polycystic Ovary Syndrome: the Epigenetics Behind the Disease

Polycystic ovary syndrome (PCOS) is one of the most common endocrine disorders, affecting approximately 5-20% of women of reproductive age. PCOS is a multifactorial, complex, and heterogeneous disease, characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovaries, which may lead to impaired fertility. Besides the reproductive outcomes, multiple comorbidities, such as metabolic disturbances, insulin resistance, obesity, diabetes, and cardiovascular disease, are associated with PCOS. In addition to the clear genetic basis, epigenetic alterations may also play a central role in PCOS outcomes, as environmental and hormonal alterations directly affect clinical manifestations and PCOS development. Here, we highlighted the epigenetic modifications in the multiplicity of clinical manifestations, as well as environmental epigenetic disruptors, as intrauterine hormonal and metabolic alterations affecting embryo development and the adulthood lifestyle, which may contribute to PCOS development. Additionally, we also discussed the new approaches for future studies and potential epigenetic biomarkers for the treatment of associated comorbidities and improvement in quality of life of women with PCOS.

The Ameliorating Effects of Bushen Huatan Granules and Kunling Wan on Polycystic Ovary Syndrome Induced by Dehydroepiandrosterone in Rats

Aim

To investigate the effects of Bushen Huatan Granules (BHG) and Kunling Wan (KW), the two Chinese medicines, on the regulation of polycystic ovary syndrome (PCOS) and their underlying mechanisms.

Materials and Methods

PCOS rat model was established by subcutaneous injection of dehydroepiandrosterone (DHEA) (6 mg/100 g/day) for 20 days, followed by treatment with BHG (0.75, 1.49, and 2.99 g/kg) or KW (0.46, 0.91, and 1.82 g/kg) by gavage for 4 weeks. Estrous cycle was detected by vaginal smears. Follicles development was assessed by histology. Levels of testosterone and insulin in serum were tested by ELISA. Apoptosis of Granulosa cells (GCs) was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling staining. Pathways associated with apoptosis were detected with western blot. Pregnancy outcome was also assessed. GCs were pre-treated with 10^–5 M testosterone in vitro for 24 h, then incubated with serum from rats receiving BHG (1.49 g/kg) or KW (1.82 g/kg). The parameters concerning apoptosis, mitochondrial function and endoplasmic reticulum stress were assessed.

Results

Post-treatment with either BHG or KW ameliorated DHEA-induced irregular estrous cycles, follicles development abnormalities, increase of testosterone and insulin in serum, and the apoptosis of GCs. Post-treatment with BHG decreased the expression of cleaved caspase-9/caspase 9, release of cytochrome C from mitochondria, and mitochondria reactive oxygen species production, increased activities of complex I, II, IV of ovarian tissue. Post-treatment with KW decreased the levels of caspase-12, GRP78, C/EBP homologous protein, phosphorylation of IRE-I, x-box-binding protein 1s, as well as phosphorylation of proline-rich receptor-like protein kinase, phosphorylation of eukaryotic translation initiation factor 2α and ATF4 of ovarian tissue and GCs. Both BHG and KW ameliorated pregnancy outcome.

Conclusion

This study demonstrated BHG or KW as a potential strategy for treatment of PCOS induced by DHEA, and suggested that the beneficial role of the two medicines were mediated by different pathway with the effect of BHG being correlated with the regulation of mitochondria, while the effect of KW being attributable to protection of endoplasmic reticulum stress.

Decreased expression of TERT and telomeric proteins as human ovaries age may cause telomere shortening

OBJECTIVE

Telomeres are repetitive sequences localized at the ends of eukaryotic chromosomes comprising noncoding DNA and telomere-binding proteins. TRF1 and TRF2 both bind to the double-stranded telomeric DNA to regulate its length throughout the lifespan of eukaryotic cells. POT1 interacts with single-stranded telomeric DNA and contributes to protecting genomic integrity. Previous studies have shown that telomeres gradually shorten as ovaries age, coinciding with fertility loss. However, the molecular background of telomere shortening with ovarian aging is not fully understood.

METHODS

The present study aimed to determine the spatial and temporal expression levels of the TERT, TRF1, TRF2, and POT1 proteins in different groups of human ovaries: fetal (n = 11), early postnatal (n = 10), premenopausal (n = 12), and postmenopausal (n = 14). Also, the relative telomere signal intensity of each group was measured using the Q-FISH method.

RESULTS

We found that the telomere signal intensities decreased evenly and significantly from fetal to postmenopausal groups (P < 0.05). The TERT, TRF1, TRF2, and POT1 proteins were localized in the cytoplasmic and nuclear regions of the oocytes, granulosa and stromal cells. Furthermore, the expression levels of these proteins reduced significantly from fetal to postmenopausal groups (P < 0.05).

CONCLUSION

These findings suggest that decreased TERT and telomere-binding protein expression may underlie the telomere shortening of ovaries with age, which may be associated with female fertility loss. Further investigations are required to elicit the molecular mechanisms regulating the gradual decrease in the expression of TERT and telomere-binding proteins in human oocytes and granulosa cells during ovarian aging.

miR-206 serves an important role in polycystic ovary syndrome through modulating ovarian granulosa cell proliferation and apoptosis

An increasing number of studies have reported that microRNAs (miRNAs) have an important role in polycystic ovary syndrome (PCOS). Downregulation of miR-206 in patients with PCOS has been found, however, its specific role remains unclear. The present study aimed to investigate the roles of miR-206 in (PCOS) and to determine the underlying molecular mechanisms. Reverse transcription-quantitative PCR (RT-qPCR) was performed to analyze the expression levels of miR-206 in normal ovarian surface epithelial IOSE80 cells and human ovarian granulosa cell-like KGN cells. TargetScan was used to predict the target gene of miR-206, which was subsequently verified using a dual-luciferase reporter gene assay. The mRNA expression levels of cyclin D2 (CCND2) and the transfection efficiencies of the miR-206 mimic and CCDN2 overexpression plasmid were determined using RT-qPCR analysis. The protein expression levels of CCND2, cleaved-caspase-3 and pro-caspase-3 were analyzed using western blotting, and an MTT assay and flow cytometric analysis were used to evaluate the cell viability and levels of apoptosis, respectively, in the cells following transfection. Finally, the activity of caspase-3 was analyzed using a caspase-3 activity assay kit. The results of the present study revealed that the expression levels of miR-206 were downregulated in KGN cells compared with IOSE80 cells. CCND2 was predicted and verified to be a direct target gene of miR-206, and the mRNA and protein expression levels of CCND2 were discovered to be upregulated in KGN cells compared with IOSE80 cells. The miR-206 mimic and CCND2 overexpression plasmid significantly upregulated the expression levels of miR-206 and CCND2, respectively, in KGN cells. The miR-206 mimic also downregulated the expression levels of CCND2 in KGN cells, while this effect was reversed following the transfection with the CCND2 overexpression plasmid. Compared with the mimic control group, the miR-206 mimic significantly decreased the cell viability, induced the levels of apoptosis, increased the activity of caspase-3, upregulated cleaved-caspase-3 protein expression levels and downregulated pro-caspase-3 protein expression levels in KGN cells following transfection; these effects were reversed following the overexpression of CCND2. In conclusion, the findings of the present study suggested that miR-206 may serve an important role in PCOS through modulating ovarian granulosa cell viability and apoptosis.

Telomere Length Differently Associated to Obesity and Hyperandrogenism in Women With Polycystic Ovary Syndrome

BACKGROUND

Polycystic Ovary Syndrome (PCOS) often present metabolic disorders and hyperandrogenism (HA), facts that may influence the telomere length (TL).

AIMS

To compare the absolute TL (aTL) between women with PCOS and control women, and their association with the presence of obesity and HA parameters.

MATERIALS AND METHODS

The PCOS group included 170 unrelated women outpatients and the control group, 64 unrelated donor women. Anthropometric, biochemical-clinical parameters and androgen profile were determined. The PCOS patients were divided accordingly to the presence of obesity and androgenic condition. The aTL was determined from peripheral blood leukocytes by Real Time quantitative PCR.

RESULTS

Women with PCOS exhibited a significantly longer aTL than controls after age adjustment (p=0.001). A stepwise multivariate linear regression in PCOS women, showed that WC (waist circumference) contributed negatively (b=-0.17) while testosterone levels contributed positively (b=7.24) to aTL. The non-Obese PCOS (noOB-PCOS) presented the longest aTL when compared to controls (p=0.001). Meanwhile, the aTL was significantly higher in the hyperandrogenic PCOS phenotype (HA-PCOS) than in the controls (p=0.001) and non hyperandrogenic PCOS phenotype (NHA-PCOS) (p=0.04). Interestingly, when considering obesity and HA parameters in PCOS, HA exerts the major effect over the aTL as non-obese HA exhibited the lengthiest aTL (23.9 ± 13.13 Kbp). Conversely, the obese NHA patients showed the shortest aTL (16.5 ± 10.59 Kbp).

CONCLUSIONS

Whilst a shorter aTL could be related to the presence of obesity, a longer aTL would be associated with HA phenotype. These findings suggest a balance between the effect produced by the different metabolic and hormonal components, in PCOS women.

Glutathione-dependent enzymes in the follicular fluid of the first-retrieved oocyte and their impact on oocyte and embryos in polycystic ovary syndrome: A cross-sectional study

Background

Oxidative stress and GSH-dependent antioxidant system plays a key role in the pathogenesis of polycystic ovary syndrome (PCOS).

Objective

We compared glutathione peroxidase (GPx) and glutathione reductase activities and reduced glutathione (GSH) levels in serum and follicular fluid (FF) of the first-retrieved follicle and their impact on quality of oocyte and embryo in PCOS women undergoing IVF.

Materials and Methods

This cross sectional study was conducted on 80 pairs of blood samples and FF of the first-retrieved follicle from PCOS women, at the Infertility center of Ghadir Mother and Child Hospital. The mean activity of GPx and GR, also GSH levels in the serum and FF were compared to the quality of the first follicle and resultant embryo.

Results

Retrieved oocytes included 53 (66.25%) MII, 17 (21.25%) MI, and 10 (12.5%) germinal vesicles; after IVF 42 (52.50%) embryos with grade I and 11 (13.75%) with grade II were produced. The mean values for all three antioxidants were higher in the FF compared to serum (p < 0.001). Also all of the mean measured levels were significantly higher in the FF of the MII oocytes compared to that of oocytes with lower grades (p = 0.012, 0.006 and 0.012, respectively). The mean GPX activity and GSH levels were significantly higher in the serum (p = 0.016 and 0.012, respectively) and FF (p = 0.001 for both) of the high-quality grade I embryos.

Conclusion

GSH-dependent antioxidant system functions more efficiently in the FF of oocytes and embryos with higher quality.

Telomere length: lights and shadows on their role in human reproduction

Telomeres are repeated DNA sequences whose main function is to preserve genome stability, protecting chromosomes ends from shortening caused by progressive loss during each cell replication or DNA damage. Telomere length regulation is normally achieved by telomerase enzyme, whose activity is progressively shut off during embryonic differentiation in somatic tissues, whereas it is maintained in germ cells, activated lymphocytes, and certain types of stem cell populations. The maintenance of telomerase activity for a longer time is necessary for germ cells to delay telomere erosion, thus avoiding chromosome segregation defects that could contribute to aneuploid or unbalanced gametes. Over the last few years, telomere biology has become an important topic in the field of human reproduction, encouraging several studies to focus on the relation between telomere length and spermatogenesis and male fertility, embryo development and quality during assisted reproductive treatment, and female pathologies as polycystic ovary, premature ovarian insufficiency, and endometriosis. This review analyzes whether telomere length in germ cells is related to reproduction fitness, whether telomere length is related to pathologies associated with male and female fertility, and whether measurement of telomere length could represent a biomarker of germ cell and embryo quality. Telomere length could be considered a molecular marker of spermatogenesis and sperm quality and is somewhat related to male fertility potential. Fewer evidence, although promising, is available for oocytes, female (in)fertility, and embryo quality. The increasing evidence for a role of telomeres and telomere length in human reproduction, indeed, has expanded the historical view of considering them just a marker of aging. Telomere length might have in the future a prognostic potential in couple infertility, especially useful to select best germ cells with the greatest potential of fertilization.

Telomere Length and Telomerase Activity in Immature Oocytes and Cumulus Cells of Women with Polycystic Ovary Syndrome

Metaphase II oocytes (MII) from polycystic ovary syndrome (PCOS) frequently have impaired oocyte competence. Since telomere maintenance is important for folliculogenesis, oocyte maturation, and early embryonic development, we sought to verify the implications of PCOS on telomere length and telomerase activity in immature oocytes and cumulus cells. 43 PCOS and 67 control women were included, and anthropometric, biochemical, and hormonal characteristics were evaluated. The telomere length in germinal vesicle stage (GV) and in metaphase I (MI) oocytes, as well as in the cumulus cells of immature (CCI) and mature oocytes (CCM), and in leukocytes was measured by qPCR. The telomerase activity in reproductive cells was evaluated by the TRAPeze® XL Kit. The body mass index (p = 0.001), LH (p = 0.015), estradiol (p = 0.004), insulin (p = 0.002), testosterone (p < 0.0001), androstenedione (p = 0.001), free androgen index (p < 0.0001), and c-reactive protein (p = 0.003) were greater, while the FSH (p = 0.0002) was lower in the PCOS group. The telomere length in the CCI (p = 0.649) and CCM (p = 0.378) did not differ between the PCOS and the control groups. On the other hand, telomerase activity in the CCI (p = 0.003) and CCM (p = 0.022) was higher in the PCOS group. In the leukocyte's cells, the telomere length was reduced in the PCOS group (p = 0.025). In the GV and MI oocytes, no differences were observed in telomere length and telomerase activity between the groups. We showed that telomere length is not altered in reproductive cells from PCOS. However, higher telomerase activity in the CCI and CCM may be required for telomere length maintenance.

The association of female and male infertility with telomere length (Review)

Telomere length (TL) has long been associated with aging, as telomeres serve as protective caps of chromosomes, and are thus deeply involved in the preservation of genome integrity and are vital to cellular functions. Traditionally, a strong link connects aging and infertility in both sexes, with an earlier onset in females. Over the past decade, telomeres have attracted increasing attention due to the role they play in fertility. In this review, we investigated the potential positive or negative association between relative TL and different factors of female and male infertility. A systematic search of the PubMed database was conducted. Out of the 206 studies identified, 45 were reviewed as they fulfilled the criteria of validity and relevance. Following an analysis and a comparison of the study outcomes, several clear trends were observed. The majority of female infertility factors were associated with a shorter TL, with the exception of endometriosis, premature ovarian failure and clear cell carcinoma that were associated with a longer TL and polycystic ovary syndrome (PCOS), which revealed conflicting results among several studies, leading to ambiguous conclusions. Male infertility factors were associated with a shorter TL. Although this review can provide an outline of general trends in the association of TL with infertility factors, further epidemiological and original research studies are required to focus on investigating the basis of these varying lengths of telomeres.

Telomere length and telomerase activity during folliculogenesis in mammals

Telomeres are repetitive non-coding DNA sequences located at the ends of chromosomes in eukaryotic cells. Their most important function is to protect chromosome ends from being recognized as DNA damage. They are also implicated in meiosis and synapse formation. The length of telomeres inevitably shortens at the end of each round of DNA replication and, also, as a consequence of the exposure to oxidative stress and/or genotoxic agents. The enzyme telomerase contributes to telomere lengthening. It has been reported that telomerase is exclusively expressed in germ cells, granulosa cells, early embryos, stem cells, and various types of cancerous cells. Granulosa cells undergo many mitotic divisions and either granulosa cells or oocytes are exposed to a variety of genotoxic agents throughout folliculogenesis; thus, telomerase plays an important role in the maintenance of telomere length. In this review article, we have comprehensively evaluated the studies focusing on the regulation of telomerase expression and activity, as well as telomere length, during folliculogenesis from primordial to antral follicles, in several mammalian species including mice, bovines, and humans. Also, the possible relationships between female infertility caused by follicular development defects and alterations in the telomeres and/or telomerase activity are discussed.

Excessive nerve growth factor impairs bidirectional communication between the oocyte and cumulus cells resulting in reduced oocyte competence

BACKGROUND

Excessive nerve growth factor (NGF) is commonly found in the follicular fluid of patients with polycystic ovary syndrome (PCOS). Furthermore, oocytes from PCOS patients exhibit lower developmental competence. The purpose of this study was to explore the association between excessive NGF and low oocyte competence in vitro.

METHODS

Excessive NGF was added to mouse cumulus oocyte complexes (COCs) cultured in vitro to investigate meiotic maturation of the oocyte. After culture, mRNA expression levels of Pfkp and Ldha genes in cumulus cells (CCs) and Gdf9, Bmp15 and Fgf8 genes in oocytes, were determined by real-time quantitative polymerase chain reaction (qPCR). We also investigated the mRNA content of Pfkp and Ldha in CCs from PCOS and non-PCOS patients.

RESULTS

Excessive NGF significantly inhibited oocyte meiotic maturation. The inhibitory effect was mediated by the NGF high-affinity receptor, NTRK1. mRNA content of Pfkp and Ldha genes in CCs was significantly reduced by excessive NGF stimulation. Moreover, the expression levels of Gdf9, Bmp15 and Fgf8 were also decreased in oocytes, and was induced by excessive NGF-stimulated CCs. In addition, lower expression levels of Pfkp and Ldha in CCs were identified in Chinese PCOS patients with excessive NGF (PCOS, 22 ± 2.63 ng/ml, n = 13; non-PCOS, 7.18 ± 2.42 ng/ml, n = 9; p < 0.01) in the follicular fluid, suggesting a potential association between excessive NGF and decreased glycolysis in the CCs of women with PCOS.

CONCLUSIONS

Excessive NGF impairs bidirectional communication between oocyte and cumulus cells, which might be related to low oocyte competence.