Cell-free DNA and telomere length among women undergoing in vitro fertilization treatment

Telomere length of granulosa cells is positively associated with oocyte maturation and fertilization

RESEARCH QUESTION

Is it feasible to use the telomere length of granulosa cells as a biomarker for ovarian function and embryological outcomes during IVF?

DESIGN

This prospective cohort study included 240 patients undergoing their first IVF cycle between October 2022 and December 2022. The main outcomes were the associations between relative telomere length of granulosa cells, collected during oocyte retrieval, and ovarian reserve, ovarian response and embryological outcomes.

RESULTS

The mean ± SD relative telomere length was -5.35 ± 2.55. No significant relationships were found between telomere length and ovarian reserve and ovarian response. Telomere length was positively correlated with maturation rate (r = 0.386, P < 0.001) and fertilization rate (retrieved oocytes: r = 0.408, P < 0.001; matured oocytes: r = 0.203, P = 0.002). However, telomere length was not significantly correlated with oocyte retrieval or viable embryo rate. On multifactor linear regression, relative telomere length was associated with oocyte maturation rate (P < 0.001) and fertilization rate of matured oocytes (P = 0.011). The receiver operating characteristic curve of telomere length as a predictor of oocyte maturity showed that the area under the curve (AUC) was 0.719 (P < 0.001), while the AUC of telomere length as a predictor of fertilization (of matured oocytes) was 0.613 (P = 0.005).

CONCLUSION

Telomere length is correlated with embryological outcomes in IVF, mainly by affecting oocyte maturation and fertilization, rather than early embryo development. Telomere length alone cannot be used as a biomarker for ovarian reserve or ovarian response. When dealing with recurrent oocyte maturity or fertilization disorders, therapies oriented to lengthen telomeres or increase telomerase expression or function would facilitate cell division of granulosa cells, leading to higher oocyte maturation and fertilization rates.

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.

Evaluation of telomere length and telomerase activity on predicting in vitro fertilization treatment outcomes

The current article is a literature review aiming to provide an overview of the existing knowledge on the association between telomere length and telomerase activity and in vitro fertilization. Recently, telomeres have been used as an effective biomarker to determine biological age, which may differ from chronological age due to genetic, lifestyle, and environmental factors. Cellular senescence, along with other exogenous and mainly environmental factors, can enhance telomere wear, further shortening their ends and may also affect reproductive aging. IVF is a common fertility treatment caused by female reasons (age, ovulation disorders, damaged or blocked fallopian tubes, endometriosis), male reasons (low sperm quantity or quality), or unexplained infertility. A growing number of studies have proposed a relationship between telomere length and telomerase activity and IVF success and have suggested their use as candidate biomarkers for IVF outcome. Nevertheless, additional studies are necessary to be conducted, in order to clarify the possible implication of telomeres in IVF and to evaluate their possible role as valuable predictors of IVF result.

Cell-free DNA as a potential diagnostic biomarker in academic stress: A case-control study in young adults

Background

Stress is a pervasive issue in modern life, affecting both physical and mental health. Identifying biomarkers like cell-free DNA (cfDNA) could provide insights into stress response and help detect individuals at risk for stress-related disorders.

Objective

The aim of this study is to investigate the potential use of cfDNA as a diagnostic biomarker in individuals experiencing stress.

Methodology

A case-control analysis was conducted using convenient sampling on university participants (N = 285 cases, N = 500 controls) aged 18-24. The study assessed haematological and lipid profile parameters using the Sysmex XP-300TM automated analyzer and an automated biochemistry analyzer, and cfDNA was extracted using a standardized in house developed Phenol-Chloroform protocol and estimated using Agarose Gel Electrophoresis and Nanodrop. Statistical analysis was performed using SPSS ver. 21.0.

Results

The results indicated a significant difference between stressed individuals and healthy controls in demographic, haematological and biochemical parameters. Specifically, stressed cases had significantly higher levels of cholesterol, LDL cholesterol, triglycerides, glucose, VLDL cholesterol, and lower levels of HDL compared to healthy controls. Stressed cases also showed significantly elevated levels of circulating cfDNA relative to healthy controls.

Conclusion

These findings suggest that cfDNA may have potential as a diagnostic biomarker for stress.

Potential effects of assisted reproductive technology on telomere length and telomerase activity in human oocytes and early embryos

Telomeres are repetitive DNA sequences at eukaryotic chromosome ends and function in maintaining genome integrity and stability. These unique structures undergo shortening due to various factors including biological aging, consecutive DNA replication, oxidative stress, and genotoxic agents. Shortened telomeres can be lengthened by the enzyme telomerase and alternative lengthening of telomeres in germ cells, early embryos, stem cells, and activated lymphocytes. If telomeres reach to critical length, it may lead to genomic instability, chromosome segregation defects, aneuploidy, and apoptosis. These phenotypes also occur in the oocytes and early embryos, produced using assisted reproductive technologies (ARTs). Thus, a number of studies have examined the potential effects of ART applications such as ovarian stimulation, culture conditions, and cryopreservation procedures on telomeres. Herein, we comprehensively reviewed impacts of these applications on telomere length and telomerase activity in ART-derived oocytes and embryos. Further, we discussed use of these parameters in ART centers as a biomarker in determining oocyte and embryo quality.

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.

Telomere dysfunction in ageing and age-related diseases

Ageing organisms accumulate senescent cells that are thought to contribute to body dysfunction. Telomere shortening and damage are recognized causes of cellular senescence and ageing. Several human conditions associated with normal ageing are precipitated by accelerated telomere dysfunction. Here, we systematize a large body of evidence and propose a coherent perspective to recognize the broad contribution of telomeric dysfunction to human pathologies.

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).

Preconception leukocyte telomere length and pregnancy outcomes among women with demonstrated fecundity

STUDY QUESTION

Is preconception leukocyte telomere length associated with fecundability, pregnancy loss and live birth among women attempting natural conception with a history of 1-2 prior pregnancy losses?

SUMMARY ANSWER

Preconception leukocyte telomere length is not associated with fecundability, pregnancy loss or live birth.

WHAT IS KNOWN ALREADY

As women increasingly delay childbearing, accessible preconception biomarkers to predict pregnancy outcomes among women seeking natural conception could improve preconception counseling. Findings of small case-control or cross-sectional studies suggest that telomere attrition is associated with adverse pregnancy outcomes among women undergoing fertility treatment, but prospective studies in non-clinical populations are lacking.

STUDY DESIGN, SIZE, DURATION

Participants included 1228 women aged 18-40 years with a history of 1-2 prior pregnancy losses who were recruited at four university medical centers (2006-2012).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Preconception leukocyte telomere length was measured at baseline using PCR and reported as a ratio (T/S) in relation to population-specific standard reference DNA. Women were followed for up to six cycles while attempting to conceive. Associations of telomere length with fecundability, live birth and pregnancy loss were estimated using discrete Cox proportional hazards models and log-binomial models.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjustment for age, BMI, smoking and other factors, preconception telomere length was not associated with fecundability (Q4 vs Q1 FOR = 1.00; 95% CI = 0.79, 1.27), live birth (Q4 vs Q1 RR = 1.00; 95% CI = 0.85, 1.19), or pregnancy loss (Q4 vs Q1 RR = 1.12; 95% CI = 0.78, 1.62).

LIMITATIONS, REASONS FOR CAUTION

Telomere length was measured in leukocytes, which is an accessible tissue in women attempting natural conception but may not reflect telomere length in oocytes. Most women were younger than 35 years, limiting our ability to evaluate associations among older women. Participants had a history of 1-2 prior pregnancy losses; therefore, our findings may not be widely generalizable.

WIDER IMPLICATIONS OF THE FINDINGS

Despite prior research suggesting that telomere length may be associated with pregnancy outcomes among women seeking fertility treatment, our findings suggest that leukocyte telomere length is not a suitable biomarker of pregnancy establishment or maintenance among women attempting natural conception.

STUDY FUNDING/COMPETING INTEREST(S)

This research was supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (National Institutes of Health, Bethesda, MD, USA; contract numbers HHSN267200603423, HHSN267200603424 and HHSN267200603426). The authors have no conflicts of interest to disclose.

TRIAL REGISTRATION NUMBER

The trial was registered with ClinicalTrials.gov, number NCT00467363.

Reproductive aging and telomeres: Are women and men equally affected?

Successful reproduction is very important for individuals and for society. Currently, the human health span and lifespan are the object of intense and productive investigation with great achievements, compared to the last century. However, reproduction span does not progress concomitantly with lifespan. Reproductive organs age, decreasing the levels of sexual hormones, which are protectors of health through their action on several organs of the body. Thus, this is the starting point of the organismal decay and infertility. This starting point is easily detected in women. In men, it goes under the surface, undetected, but it goes, nevertheless. Regarding fertility, aging alters the hormonal equilibrium, decreases the potential of reproductive organs, diminishes the quality of the gametes and worsen the reproductive outcomes. All these events happen at a different pace and affecting different organs in women and men. The question is what molecular pathways are involved in reproductive aging and if there is a possible halting or even reversion of the aging events. Answers to all these points will be explained in the present review.

Circulating cell-free DNA (cfDNA) levels in BRCA1 and BRCA2 mutation carriers: A preliminary study

BACKGROUND

Female carriers of BRCA1 or BRCA2 germline mutations are at a substantially increased risk for developing breast and ovarian cancer. The lack of effective early detection schemes for ovarian cancer, mandate surgical removal of adnexa at age 35-40 years in these high-risk women. The role of circulating cell-free DNA (cfDNA) levels as a marker for early detection in high-risk women has rarely been reported.

OBJECTIVE

To quantify cfDNA levels in BRCA1BRCA2 carriers.

METHODS

Serum cfDNA levels, measured by direct fluorometric assay in cancer-free female BRCA1BRCA2 mutation carriers were compared with cancer-free controls recruited from among women undergoing breast biopsy or routine colonoscopy.

RESULTS

Overall, 10 BRCA1 (185delAG) and 10 BRCA2 (6174delT) mutation carriers, 20 breast biopsy controls, and 20 colonoscopy controls participated. cfDNA levels [Median (95% CI)], were 472 (317-589) ng/ml and 525 (339-621) ng/ml in breast biopsy and colonoscopy controls, respectively. Median levels of cfDNA in BRCA1 and BRCA2 mutation carriers combined were 921 (835-1087) ng/ml, significantly higher than in both controls (P< 0.0001).

CONCLUSIONS

cfDNA levels are significantly higher in BRCA1 and BRCA2 mutation carriers compared with non-carriers. This finding, if validated, may facilitate development of early detection breast/ovarian cancer biomarker in high-risk women.

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.

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.

Basal cortisol, cortisol reactivity, and telomere length: A systematic review and meta-analysis

The objective of the present study is to synthesize the existing empirical literature and perform a meta-analysis of published data on the relationship between cortisol and telomere length. We systematically searched studies that examined the relationship between cortisol and telomere length in humans on electronic databases and screened reference sections of included articles. Fourteen studies were included in the meta-analysis, with effect sizes being extracted for two cortisol measures: basal cortisol levels and cortisol reactivity to acute psychological stress. Results from random effects models showed that basal cortisol levels (13 effect sizes from 12 cross-sectional studies, N = 3675 participants) were not significantly correlated with telomere length (r =-0.05, 95% CI [-0.11, 0.02]). Further, results stratified by the specimen type for cortisol measurement (i.e., saliva, urine, blood) showed that none of the three basal cortisol level measures were correlated with telomere length. However, we found a statistically significant correlation between salivary cortisol reactivity to acute psychosocial stress (6 cross-sectional studies, N = 958 participants) and telomere length (r = -0.13, 95% CI [-0.23, -0.03]). Subgroup analyses revealed that correlations between salivary cortisol reactivity and telomere length were more evident in studies conducted among children (vs. adults) and in studies that included female participants only (vs. both genders). However, the small number of available studies limits the conclusions derived from subgroup analyses, and more studies are needed before moderator effects can be properly established. Overall, findings of this study support the existence of a relationship between cortisol reactivity and telomere shortening.

Cell-free DNA release under psychosocial and physical stress conditions

The understanding of mechanisms linking psychological stress to disease risk depend on reliable stress biomarkers. Circulating cell-free DNA (cfDNA) has emerged as a potential biomarker of cellular stress, aging, inflammatory processes, and cell death. Recent studies indicated that psychosocial stress and physical exercise might also influence its release. We compared the effects of acute psychosocial and physical exercise stress on cfDNA release by exposing 20 young, healthy men to both an acute psychosocial laboratory stressor and an acute physical exercise stressor. Venous blood and saliva samples were collected before and after stress exposure. Cell-free DNA was extracted from plasma and quantified by qPCR. Furthermore, cfDNA fragment length was analyzed and cfDNA methylation patterns were assayed across time. In addition, release of stress hormones and subjective stress responses were measured. Results showed a twofold increase of cfDNA after TSST and fivefold increase after exhaustive treadmill exercise, with an overabundance of shorter cfDNA fragments after physical exhaustion. Interestingly, cell-free mitochondrial DNA showed similar increase after both stress paradigms. Furthermore, cfDNA methylation signatures-used here as a marker for diverse cellular origin-were significantly different post stress tests. While DNA methylation decreased immediately after psychosocial stress, it increased after physical stress, suggesting different cellular sources of active DNA release. In summary, our results suggest stimulus and cell-specific regulation of cfDNA release. Whereas the functional role of stress-associated cfDNA release remains elusive, it might serve as a valuable biomarker in molecular stress research as a part of the psychophysiological stress response.