Can telomere shortening be the main indicator of non-viable fetus elimination?

Steady morphokinetic progression is an independent predictor of live birth: a descriptive reference for euploid embryos

STUDY QUESTION

Can modelling the longitudinal morphokinetic pattern of euploid embryos during time-lapse monitoring (TLM) be helpful for selecting embryos with the highest live birth potential?

SUMMARY ANSWER

Longitudinal reference ranges of morphokinetic development of euploid embryos have been identified, and embryos with steadier progression during TLM are associated with higher chances of live birth.

WHAT IS KNOWN ALREADY

TLM imaging is increasingly adopted by fertility clinics as an attempt to improve the ability of selecting embryos with the highest potential for implantation. Many markers of embryonic morphokinetics have been incorporated into decision algorithms for embryo (de)selection. However, longitudinal changes during this temporal process, and the impact of such changes on embryonic competence remain unknown. Aiming to model the reference ranges of morphokinetic development of euploid embryos and using it as a single longitudinal trajectory might provide an additive value to the blastocyst morphological grade in identifying highly competent embryos.

STUDY DESIGN SIZE DURATION

This observational, retrospective cohort study was performed in a single IVF clinic between October 2017 and June 2021 and included only autologous single euploid frozen embryo transfers (seFET).

PARTICIPANTS/MATERIALS SETTING METHODS

Reference ranges were developed from [hours post-insemination (hpi)] of the standard morphokinetic parameters of euploid embryos assessed as tPB2, tPNa, tPNf, t2-t9, tSC, tM, tSB, and tB. Variance in morphokinetic patterns was measured and reported as morphokinetic variance score (MVS). Nuclear errors (micronucleation, binucleation, and multinucleation) were annotated when present in at least one blastomere at the two- or four-cell stages. The blastocyst grade of expansion, trophectoderm (TE), and inner cell mass (ICM) were assessed immediately before biopsy using Gardner's criteria. Pre-implantation genetic diagnosis for aneuploidy (PGT-A) was performed by next-generation sequencing. All euploid embryos were singly transferred in a frozen transferred cycle and outcomes were assessed as live birth, pregnancy loss, or not pregnant. Association of MVS with live birth was investigated with regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

TLM data from 340 seFET blastocysts were included in the study, of which 189 (55.6%) resulted in a live birth. The median time for euploid embryos to reach blastulation was 109.9 hpi (95% CI: 98.8-121.0 hpi). The MVS was calculated from the variance in time taken for the embryo to reach all morphokinetic points and reflects the total morphokinetic variability it exhibits during its development. Embryos with more erratic kinetics, i.e. higher morphokinetic variance, had higher rates of pregnancy loss (P = 0.004) and no pregnancy (P < 0.001) compared to embryos with steadier morphokinetic patterns. In the multivariable analysis adjusting for ICM, TE grade, presence of nuclear errors, and time of blastulation, MVS was independently associated with live birth (odds ratio [OR]: 0.62, 95% CI: 0.46-0.84, P = 0.002) along with ICM quality. Live birth rate of embryos with the same ICM grading but different morphokinetic variance patterns differed significantly. Live birth rates of embryos exhibiting low MVS with ICM grades A, B, and C were 85%, 76%, and 67%, respectively. However, ICM grades A, B, and C embryos with high MVS had live birth rates of 65%, 48%, and 21% (P < 0.001). The addition of the MVS to embryo morphology score (ICM and TE grading) significantly improved the model's AUC value (0.67 vs 0.62, P = 0.015) and this finding persisted through repeat cross-validation (0.64 ± 0.08 vs 0.60 ± 0.07, P < 0.001).

LIMITATIONS REASONS FOR CAUTION

The exclusion of IVF cases limits, for now, the utility of the model to only ICSI-derived embryos. The utility of these reference ranges and the association of MVS with various clinical outcomes should be further investigated.

WIDER IMPLICATIONS OF THE FINDINGS

We have developed reference ranges for morphokinetic development of euploid embryos and a marker for measuring total morphokinetic variability exhibited by developed blastocysts. Longitudinal assessment of embryonic morphokinetics rather than static time points may provide more insight about which embryos have higher live birth potential. The developed reference ranges and MVS show an association with live birth that is independent of known morphological factors and could emerge as a valuable tool in prioritizing embryos for transfer.

STUDY FUNDING/COMPETING INTERESTS

This study received no external funding. The authors declare no conflicting interests.

TRIAL REGISTRATION NUMBER

N/A.

Blastocyst telomere length predicts successful implantation after frozen-thawed embryo transfer

STUDY QUESTION

Do embryos with longer telomere length (TL) at the blastocyst stage have a higher capacity to survive after frozen-thawed embryo transfer (FET)?

SUMMARY ANSWER

Digitally estimated TL using low-pass whole genome sequencing (WGS) data from the preimplantation genetic testing for aneuploidy (PGT-A) process demonstrates that blastocyst TL is the most essential factor associated with likelihood of implantation.

WHAT IS KNOWN ALREADY

The lifetime TL is established in the early cleavage cycles following fertilization through a recombination-based lengthening mechanism and starts erosion beyond the blastocyst stage. In addition, a telomerase-mediated slow erosion of TL in human fetuses has been observed from a gestational age of 6-11 weeks. Finally, an abnormal shortening of telomeres is likely involved in embryo loss during early development.

STUDY DESIGN SIZE DURATION

Blastocyst samples were obtained from patients who underwent PGT-A and FET in an IVF center from March 2015 to May 2018. Digitally estimated mitochondrial copy number (mtCN) and TL were used to study associations with the implantation potential of each embryo.

PARTICIPANTS/MATERIALS SETTING AND METHODS

In total, 965 blastocysts from 232 cycles (164 patients) were available to investigate the biological and clinical relevance of TL. A WGS-based workflow was applied to determine the ploidy of each embryo. Data from low-pass WGS-PGT-A were used to estimate the mtCN and TL for each embryo. Single-variant and multi-variant logistic regression, decision tree, and random forest models were applied to study various factors in association with the implantation potential of each embryo.

MAIN RESULTS AND THE ROLE OF CHANCE

Of the 965 blastocysts originally available, only 216 underwent FET. While mtCN from the transferred embryos is significantly associated with the ploidy call of each embryo, mtCN has no role in impacting IVF outcomes after an embryo transfer in these women. The results indicate that mtCN is a marker of embryo aneuploidy. On the other hand, digitally estimated TL is the most prominent univariant factor and showed a significant positive association with pregnancy outcomes (P < 0.01, odds ratio 79.1). We combined several maternal and embryo parameters to study the joint effects on successful implantation. The machine learning models, namely decision tree and random forest, were trained and yielded classification accuracy of 0.82 and 0.91, respectively. Taken together, these results support the vital role of TL in governing implantation potential, perhaps through the ability to control embryo survival after transfer.

LIMITATIONS REASONS FOR CAUTION

The small sample size limits our study as only 216 blastocysts were transferred. The number was further reduced to 153 blastocysts, where pregnancy outcomes could be accurately traced. The other limitation of this study is that all data were collected from a single IVF center. The uniform and controlled operation of IVF cycles in a single center may cause selection bias.

WIDER IMPLICATIONS OF THE FINDINGS

We present novel findings to show that digitally estimated TL at the blastocyst stage is a predictor of pregnancy capacity after a FET cycle. As elective single-embryo transfer has become the mainstream direction in reproductive medicine, prioritizing embryos based on their implantation potential is crucial for clinical infertility treatment in order to reduce twin pregnancy rate and the time to pregnancy in an IVF center. The AI-powered, random forest prediction model established in this study thus provides a way to improve clinical practice and optimize the chances for people with fertility problems to achieve parenthood.

STUDY FUNDING/COMPETING INTERESTS

This study was supported by a grant from the National Science and Technology Council, Taiwan (MOST 108-2321-B-006-013 -). There were no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Telomere Length in Human Spermatogenic Cells as a New Potential Predictor of Clinical Outcomes in ART Treatment with Intracytoplasmic Injection of Testicular Spermatozoa

Predicting the clinical outcomes of intracytoplasmic sperm injection (ICSI) cycles that use the testicular spermatozoa of azoospermic patients presents a challenge. Thus, the development of additional approaches to assessing the competence of a testicular-sperm-derived embryo without causing damage to gametes or the embryo is necessary. One of the key parameters in determining such developmental competence is telomere length (TL). We aimed to analyze TLs in spermatogenic cells from the testicular biopsy samples of azoospermic patients and determine how this parameter influences embryo competence for pre- and post-implantation development. Using Q-FISH, we studied the TL of the chromosomes in spermatogonia and spermatocytes I from the TESE biopsy samples of 30 azoospermic patients. An increase in TL was detected during the differentiation from spermatogonia to spermatocytes I. The patients' testicular spermatozoa were used in 37 ICSI cycles that resulted in 22 embryo transfers. Nine pregnancies resulted, of which, one was ectopic and eight ended in birth. The analysis of embryological outcomes revealed a dependence between embryo competence for development to the blastocyst stage and the TL in spermatogenic cells. The TLs in spermatogonia and spermatocytes I in the testicular biopsy samples were found to be higher in patients whose testicular sperm ICSI cycles resulted in a birth. Therefore, the length of telomeres in spermatogenic cells can be considered as a potential prognostic criterion in assessing the competence of testicular-sperm-derived embryos for pre- and post-implantation development. The results of this study provide the basis for the development of a laboratory test for the prediction of testicular sperm ICSI cycle outcomes.

Reduced telomere length in amniocytes: an early biomarker of abnormal fetal development?

Telomeres protect chromosome ends and control cell division and senescence. During organogenesis, telomeres need to be long enough to ensure the cell proliferation necessary at this stage of development. Previous studies have shown that telomere shortening is associated with growth retardation and congenital malformations. However, these studies were performed in newborns or postnatally, and data on telomere length (TL) during the prenatal period are still very limited. We measured TL using quantitative PCR in amniotic fluid (AF) and chorionic villi (CV) samples from 69 control fetuses with normal ultrasound (52 AF and 17 CV) and 213 fetuses (165 AF and 48 CV) with intrauterine growth retardation (IUGR) or congenital malformations diagnosed by ultrasound. The samples were collected by amniocentesis at the gestational age of 25.0 ± 5.4 weeks and by CV biopsy at 18.1 ± 6.3 weeks. In neither sample type was TL influenced by gestational age or fetal sex. In AF, a comparison of abnormal versus normal fetuses showed a significant telomere shortening in cases of IUGR (reduction of 34%, P < 10-6), single (29%, P < 10-6) and multiple (44%, P < 10-6) malformations. Similar TL shortening was also observed in CV from abnormal fetuses but to a lesser extent (25%, P = 0.0002; 18%, P = 0.016; 20%, P = 0.004, respectively). Telomere shortening was more pronounced in cases of multiple congenital anomalies than in fetuses with a single malformation, suggesting a correlation between TL and the severity of fetal phenotype. Thus, TL measurement in fetal samples during pregnancy could provide a novel predictive marker of pathological development.

[Telomere pathology in ontogenesis in patients with Turner syndrome]

According to present medical databases there many trials to provide in vivo researches in vivo to confirm/refute shortening process of telomeres among patients with Turner syndrome. Despite the successful clinical experience of providing such patients with Turner syndrome, a lot of omics (proteomic and metabolomic) aspects still stay unclear. Main disadvantages of most researches are small volume and minimized mathematical correlation with chronic disease (coronary heart disease, essential hypertension, cardiovascular malformations). Finally, organization of international prospective multi-centered researches in vivo including patients with mosaic cariotype and co-operation between physicians and biologists are optimal solutions for this present problem.

Telomere Shortening and Fusions: A Link to Aneuploidy in Early Human Embryo Development

Importance

It is known that oocytes undergo aging that is caused by exposure to an aged ovarian microenvironment. Telomere length in mouse and bovine oocytes declines with age, and age-associated telomere shortening in oocytes is considered a sign of poor development competency. Women with advanced age undergoing assisted reproductive technologies have poor outcomes because of increasing aneuploidy rates with age. Research has shown that aneuploidy is associated with DNA damage, reactive oxygen species, and telomere dysfunction.

Objective

In this review, we focus on the possible relationship between telomere dysfunction and aneuploidy in human early embryo development and several reproductive and perinatal outcomes, discussing the mechanism of aneuploidy caused by telomere shortening and fusion in human embryos.

Evidence Acquisition

We reviewed the current literature evidence concerning telomere dysfunction and aneuploidy in early human embryo development.

Results

Shorter telomeres in oocytes, leukocytes, and granulosa cells, related to aging in women, were associated with recurrent miscarriage, trisomy 21, ovarian insufficiency, and decreasing chance of in vitro fertilization success. Telomere length and telomerase activity in embryos have been related to the common genomic instability at the cleavage stage of human development. Complications of assisted reproductive technology pregnancies, such as miscarriage, birth defects, preterm births, and intrauterine growth restriction, also might result from telomere shortening as observed in oocytes, polar body, granulosa cells, and embryos.

Conclusions and Relevance

Telomere length clearly plays an important role in the development of the embryo and fetus, and the abnormal shortening of telomeres is likely involved in embryo loss during early human development. However, telomere fusion studies have yet to be performed in early human development.

Telomere Length in Chromosomally Normal and Abnormal Miscarriages and Ongoing Pregnancies and Its Association with 5-hydroxymethylcytosine Patterns

The present study investigates telomere length (TL) in dividing chorionic cytotrophoblast cells from karyotypically normal and abnormal first trimester miscarriages and ongoing pregnancies. Using Q-FISH, we measured relative TLs in the metaphase chromosomes of 61 chorionic villous samples. Relative TLs did not differ between karyotypically normal samples from miscarriages and those from ongoing pregnancies (p = 0.3739). However, among the karyotypically abnormal samples, relative TLs were significantly higher in ongoing pregnancies than in miscarriages (p < 0.0001). Relative TLs were also significantly higher in chorion samples from karyotypically abnormal ongoing pregnancies than in those from karyotypically normal ones (p = 0.0018) in contrast to miscarriages, where relative TL values were higher in the karyotypically normal samples (p = 0.002). In the karyotypically abnormal chorionic cytotrophoblast, the TL variance was significantly lower than in any other group (p < 0.05). Assessed by TL ratios between sister chromatids, interchromatid TL asymmetry demonstrated similar patterns across all of the chorion samples (p = 0.22) but significantly exceeded that in PHA-stimulated lymphocytes (p < 0.0001, p = 0.0003). The longer telomere was predominantly present in the hydroxymethylated sister chromatid in chromosomes featuring hemihydroxymethylation (containing 5-hydroxymethylcytosine in only one sister chromatid)-a typical sign of chorionic cytotrophoblast cells. Our results suggest that the phenomena of interchromatid TL asymmetry and its association to 5hmC patterns in chorionic cytotrophoblast, which are potentially linked to telomere lengthening through recombination, are inherent to the development programme. The TL differences in chorionic cytotrophoblast that are associated with karyotype and embryo viability seem to be determined by heredity rather than telomere elongation mechanisms. The inheritance of long telomeres by a karyotypically abnormal embryo promotes his development, whereas TL in karyotypically normal first-trimester embryos does not seem to have a considerable impact on developmental capacity.

Shorter telomere length of white blood cells is associated with higher rates of aneuploidy among infertile women undergoing in vitro fertilization

OBJECTIVE

To evaluate whether the telomere length of white blood cells (WBC) and cumulus cells (CC) in an infertile population is associated with ovarian and embryonic performance.

DESIGN

Prospective cohort study.

SETTING

Academic-affiliated private practice.

PATIENTS

A total of 175 infertile women undergoing in vitro fertilization (IVF) at a single center between July 2017 and December 2018.

INTERVENTIONS

On the day of oocyte retrieval, genomic DNA was isolated from WBC and CC samples. Telomere length assessment was performed for both tissue types using quantitative real-time polymerase chain reaction. Telomere lengths were normalized using an AluYa5 sequence as an endogenous control, and linear regressions were applied.

MAIN OUTCOME MEASURES

This study assessed the relationship between relative telomere length of WBC and CC samples and measures of ovarian and embryonic performance. Specifically, patient age, antimüllerian hormone (AMH) level, peak estradiol (E₂) level, number of oocytes retrieved, number of mature (MII) oocytes retrieved, blastulation rate, and aneuploidy rate were assessed.

RESULTS

There was a statistically significant relationship between WBC relative telomere length and patient age as well as rates of embryonic aneuploidy, with shorter WBC relative telomere length associated with increasing patient age (P<.01) and higher rates of aneuploidy (P=.01). No statistically significant relationships were observed between WBC relative telomere length and the other outcome measures. No significant associations were noted between CC relative telomere length and any outcomes assessed in this study.

CONCLUSION

The relationship between WBC relative telomere length and aneuploidy warrants further investigation, particularly because significant overlap exists between increasing maternal age and rates of embryonic aneuploidy.

Maternal stress or sleep during pregnancy are not reflected on telomere length of newborns

Telomeres play an important role in maintaining chromosomal integrity. With each cell division, telomeres are shortened and leukocyte telomere length (LTL) has therefore been considered a marker for biological age. LTL is associated with various lifetime stressors and health-related outcomes. Transgenerational effects have been implicated in newborns, with maternal stress, depression, and anxiety predicting shorter telomere length at birth, possibly reflecting the intrauterine growth environment. Previous studies, with relatively small sample sizes, have reported an effect of maternal stress, BMI, and depression during pregnancy on the LTL of newborns. Here, we attempted to replicate previous findings on prenatal stress and newborn LTL in a sample of 1405 infants using a qPCR-based method. In addition, previous research has been expanded by studying the relationship between maternal sleep quality and LTL. Maternal prenatal stress, anxiety, depression, BMI, and self-reported sleep quality were evaluated with self-reported questionnaires. Despite sufficient power to detect similar or even considerably smaller effects than those previously reported in the literature, we were unable to replicate the previous correlation between maternal stress, anxiety, depression, or sleep with LTL. We discuss several possible reasons for the discrepancies between our findings and those previously described.

Dynamics of Telomere Length and Telomerase Activity in the Human Fetal Liver at 5-12 Weeks of Gestation

Fetal stem cell- (FSC-) based therapy is a promising treatment option for many diseases. The differentiation potential of FSCs is greater than that in adult stem cells, and they are more tissue-specific and have lower immunogenicity and better intrinsic homing than embryonic ones. Embryonic stem cells have higher proliferative potential than FSCs but can cause teratomas. Therefore, an evaluation of this potential represents an important biomedical challenge. Since regulation of telomere length (TL) is one mechanism governing cellular proliferation, TL is a useful surrogate marker for cell replicative potential. The prenatal dynamics of TL, however, has never been comprehensively studied. In the present study, dynamics of TL and telomerase activity in the human fetal liver during 5–12 weeks of gestation is examined. Both TL and telomerase activity were positively correlated with week of gestation. For both parameters studied, the trend to increase was evident up to 10th week of gestation. After that, they reached a plateau and remained stable. These findings indicate that telomerase activity remains high during the fetal stage, suggesting high replicative capacity of FSCs and their considerable potential for transplantation therapies. These findings, however, are preliminary only due to small sample size and require further evaluation.