Telomeres and genomic instability during early development

First prenatal case of jumping-like translocations: unraveling complex chromosomal rearrangements

Jumping translocations and jumping-like translocations constitute a rare category of complex chromosomal rearrangements, which are primarily observed in hematologic disorders and solid tumors. This study outlines a complex structural mosaic rearrangement involving a single recipient chromosome and three distinct donor chromosomes, with varying patterns of mosaicism observed across different cell lines. The rearrangement was confirmed by karyotyping, FISH, and array-CGH. These analyses revealed significant chromosomal duplications and deletions, which may contribute to the observed phenotypic abnormalities. Following characterization via various cytogenetic techniques, this rearrangement appears to be the first reported instance of a jumping-like translocation in prenatal constitutional genetics. This finding enables the formulation of hypotheses regarding the mechanisms underlying such intricate structural variants and their detection via contemporary genetic methods.

Ovarian stimulation protocols: impact on oocyte and endometrial quality and function

Ovarian stimulation (OS) truly is an art. There exists a myriad of protocols used to achieve the same goal: stimulating the ovaries to produce more than one mature oocyte to improve the chance of a live birth. However, considerable debate remains as to whether OS impacts oocyte and endometrial quality to affect in vitro fertilization outcomes. Although "more is better" has long been considered the best approach for oocyte retrieval, this review challenges that notion by examining the influence of stimulation on oocyte quality. Likewise, improved outcomes after frozen blastocyst transfer suggest that OS perturbs endometrial preparation and/or receptivity, although correlating changes with implantation success remains a challenge. Therefore, the focus of this review is to summarize our current understanding of perturbations in human oocyte quality and endometrial function induced by exogenous hormone administration. We highlight the need for further research to identify more appropriate markers of oocyte developmental competence as well as those that define the roles of the endometrium in the success of assisted reproductive technology.

Telomere Reprogramming and Cellular Metabolism: Is There a Link?

Telomeres-special DNA-protein structures at the ends of linear eukaryotic chromosomes-define the proliferation potential of cells. Extremely short telomeres promote a DNA damage response and cell death to eliminate cells that may have accumulated mutations after multiple divisions. However, telomere elongation is associated with the increased proliferative potential of specific cell types, such as stem and germ cells. This elongation can be permanent in these cells and is activated temporally during immune response activation and regeneration processes. The activation of telomere lengthening mechanisms is coupled with increased proliferation and the cells' need for energy and building resources. To obtain the necessary nutrients, cells are capable of finely regulating energy production and consumption, switching between catabolic and anabolic processes. In this review, we focused on the interconnection between metabolism programs and telomere lengthening mechanisms during programmed activation of proliferation, such as in germ cell maturation, early embryonic development, neoplastic lesion growth, and immune response activation. It is generally accepted that telomere disturbance influences biological processes and promotes dysfunctionality. Here, we propose that metabolic conditions within proliferating cells should be involved in regulating telomere lengthening mechanisms, and telomere length may serve as a marker of defects in cellular functionality. We propose that it is possible to reprogram metabolism in order to regulate the telomere length and proliferative activity of cells, which may be important for the development of approaches to regeneration, immune response modulation, and cancer therapy. However, further investigations in this area are necessary to improve the understanding and manipulation of the molecular mechanisms involved in the regulation of proliferation, metabolism, and aging.

Molecular mechanisms of aging and anti-aging strategies

Aging is a complex and multifaceted process involving a variety of interrelated molecular mechanisms and cellular systems. Phenotypically, the biological aging process is accompanied by a gradual loss of cellular function and the systemic deterioration of multiple tissues, resulting in susceptibility to aging-related diseases. Emerging evidence suggests that aging is closely associated with telomere attrition, DNA damage, mitochondrial dysfunction, loss of nicotinamide adenine dinucleotide levels, impaired macro-autophagy, stem cell exhaustion, inflammation, loss of protein balance, deregulated nutrient sensing, altered intercellular communication, and dysbiosis. These age-related changes may be alleviated by intervention strategies, such as calorie restriction, improved sleep quality, enhanced physical activity, and targeted longevity genes. In this review, we summarise the key historical progress in the exploration of important causes of aging and anti-aging strategies in recent decades, which provides a basis for further understanding of the reversibility of aging phenotypes, the application prospect of synthetic biotechnology in anti-aging therapy is also prospected.

Impact of telomere length and mitochondrial DNA copy number variants on survival of newborn cloned calves

An established technology to create cloned animals is through the use of somatic cell nuclear transfer (SCNT), in which reprogramming the somatic cell nucleus to a totipotent state by enucleated oocyte cytoplasm is a necessary process, including telomere length reprogramming. The limitation of this technology; however, is that the live birth rate of offspring produced through SCNT is significantly lower than that of IVF. Whether and how telomere length play a role in the development of cloned animals is not well understood. Only a few studies have evaluated this association in cloned mice, and fewer still in cloned cows. In this study, we investigated the difference in telomere length as well as the abundance of some selected molecules between newborn deceased cloned calves and normal cows of different ages either produced by SCNT or via natural conception, in order to evaluate the association between telomere length and abnormal development of cloned cows. The absolute telomere length and relative mitochondrial DNA (mtDNA) copy number were determined by real-time quantitative PCR (qPCR), telomere related gene abundance by reverse-transcription quantitative PCR (RT-qPCR), and senescence-associated β-galactosidase (SA-β-gal) expression by SA-β-gal staining. The results demonstrate that the newborn deceased SCNT calves had significantly shortened telomere lengths compared to newborn naturally conceived calves and newborn normal SCNT calves. Significantly lower mtDNA copy number, and significantly lower relative abundance of LMNB1 and TERT, higher relative abundance of CDKN1A, and aberrant SA-β-gal expression were observed in the newborn deceased SCNT calves, consistent with the change in telomere length. These results demonstrate that abnormal telomere shortening, lower mtDNA copy number and abnormal abundance of related genes were specific to newborn deceased SCNT calves, suggesting that abnormally short telomere length may be associated with abnormal development in the cloned calves.

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.

Advances in the study of the correlation between insulin resistance and infertility

This is a narrative review of the progress of research on the correlation between insulin resistance and infertility. Insulin resistance (IR) is not only involved in the development of various metabolic diseases, but also affects female reproductive function, and to some extent is closely related to female infertility. IR may increase the risk of female infertility by activating oxidative stress, interfering with energy metabolism, affecting oocyte development, embryo quality and endometrial tolerance, affecting hormone secretion and embryo implantation, as well as affecting assisted conception outcomes in infertile populations and reducing the success rate of assisted reproductive technology treatment in infertile populations. In addition, IR is closely associated with spontaneous abortion, gestational diabetes and other adverse pregnancies, and if not corrected in time, may increase the risk of obesity and metabolic diseases in the offspring in the long term. This article provides a review of the relationship between IR and infertility to provide new ideas for the treatment of infertility.

Telomere dynamics and reproduction

The oocyte, a long-lived, postmitotic cell, is the locus of reproductive aging in women. Female germ cells replicate only during fetal life and age throughout reproductive life. Mechanisms of oocyte aging include the accumulation of oxidative damage, mitochondrial dysfunction, and disruption of proteins, including cohesion. Nobel Laureate Bob Edwards also discovered a "production line" during oogonial replication in the mouse, wherein the last oocytes to ovulate in the adult-derived from the last oogonia to exit mitotic replication in the fetus. On the basis of this, we proposed a two-hit "telomere theory of reproductive aging" to integrate the myriad features of oocyte aging. The first hit was that oocytes remaining in older women traversed more cell cycles during fetal oogenesis. The second hit was that oocytes accumulated more environmental and endogenous oxidative damage throughout the life of the woman. Telomeres (Ts) could mediate both of these aspects of oocyte aging. Telomeres provide a "mitotic clock," with T attrition an inevitable consequence of cell division because of the end replication problem. Telomere's guanine-rich sequence renders them especially sensitive to oxidative damage, even in postmitotic cells. Telomerase, the reverse transcriptase that restores Ts, is better at maintaining than elongating T. Moreover, telomerase remains inactive during much of oogenesis and early development. Oocytes are left with short Ts, on the brink of viability. In support of this theory, mice with induced T attrition and women with naturally occurring telomeropathy suffer diminished ovarian reserve, abnormal embryo development, and infertility. In contrast, sperm are produced throughout the life of the male by a telomerase-active progenitor, spermatogonia, resulting in the longest Ts in the body. In mice, cleavage-stage embryos elongate Ts via "alternative lengthening of telomeres," a recombination-based mechanism rarely encountered outside of telomerase-deficient cancers. Many questions about Ts and reproduction are raised by these findings: does the "normal" T attrition observed in human oocytes contribute to their extraordinarily high rate of meiotic nondisjunction? Does recombination-based T elongation render embryos susceptible to mitotic nondisjunction (and mosaicism)? Can some features of Ts serve as markers of oocyte quality?

Factors associated with embryo mosaicism: a systematic review and meta-analysis

PURPOSE

Evaluate which factors are involved in the increased rate of mosaicism in embryos.

METHODS

A systematic review and meta-analysis was performed. After an exhaustive search of the literature, a total of seven papers were included in the analysis. In addition, data collected from IVF cycles performed in our fertility clinic were also analysed. Day of biopsy, embryo quality, maternal and paternal age and seminal quality were the chosen factors to be studied.

RESULTS

The results of the meta-analysis show that neither embryo quality nor seminal quality were related to mosaic embryo rate (OR: 1.09; 95% CI: 0.94-1.28 and OR: 1.10; 95% CI: 0.87-1.37, respectively). A positive association was observed for the variable "biopsy day" with embryos biopsied at day 6 or 7 having the highest rate of mosaicism (OR: 1.06; 95% CI: 1.01-1.11). In opposite to what happens with aneuploidy rate, which increases with maternal age, embryo mosaicism is higher in younger women (<34 years) rather than in older ones (≥34 years) (OR: 0.95; 95% CI: 0.92-0.98). However, for the "paternal age" factor, no association with mosaicism was found (OR: 1.04; 95% CI: 0.90-1.21).

CONCLUSIONS

With the present study, we can conclude that the factors related to the presence of mosaicism in embryos are the embryo biopsy day and maternal age. The rest of the studied factors showed no significant relationship with mosaicism. These results are of great importance as knowing the possible causes leading to mosaicism helps to improve the clinical results of reproductive treatments.

Associations between obesity, smoking behaviors, reproductive traits and spontaneous abortion: a univariable and multivariable Mendelian randomization study

Background

The correlation between potential risk factors such as obesity (leg fat percentage (left), arm fat percentage (left), waist circumference, body fat percentage, trunk fat percentage), smoking behaviors (past tobacco smoking, smoking initiation, smoking/smokers in household, current tobacco smoking) and reproductive traits (age first had sexual intercourse (AFS), age at menarche (AAM), and age at first birth (AFB)) have been linked to the occurrence of spontaneous abortion (SA). However, the causal associations between these factors and SA remain unclear.

Methods

We conducted univariable and multivariable Mendelian randomization (MR) analyses to evaluate the associations of obesity, smoking behavior and reproductive traits with SA. To select appropriate genetic instruments, we considered those that had reached the genome-wide significance level (P < 5 × 10-8) in their corresponding genome-wide association studies (GWAS) involving a large number of individuals (ranging from 29,346 to 1,232,091). SA was obtained from the FinnGen consortium, which provided summary-level data for 15,073 SA cases and 135,962 non-cases.

Results

Assessed individually using MR, the odds ratios (ORs) of SA were 0.728 (P = 4.3608×10-8), 1.063 (P = 0.0321), 0.926 (P = 9.4205×10-4), 1.141 (P = 7.9882×10-3), 5.154 (P = 0.0420), 1.220 (P = 0.0350), 1.228 (P = 0.0117), 0.795 (P = 0.0056), 1.126 (P = 0.0318), for one standard deviation (SD) increase in AFS, AAM, AFB, smoking initiation, smoking/smokers in household, arm fat percentage (left), leg fat percentage (left), waist circumference and body fat percentage, 0.925 (P = 0.4158) and 1.075 (P = 0.1479) for one SD increase in past tobacco smoking, trunk fat percentage for one SD increase in SA. In multivariable MR (MVMR), only AFS (OR = 0.802; P = 0.0250), smoking initiation (OR = 1.472, P = 0.0258), waist circumference (OR = 0.813, P = 0.0220) and leg fat percentage (left) (OR = 4.446, P = 0.043) retained a robust effect.

Conclusion

Smoking behaviors, reproductive traits and obesity-related anthropometric indicators are potential causal factors for SA. Higher leg fat percentage; smoking initiation; and lower waist circumference and AFS may increase the risk of SA. Understanding the causal relationship for SA may provide more information for SA intervention and prevention strategies.

Cohesin SMC1β promotes closed chromatin and controls TERRA expression at spermatocyte telomeres

Previous data showed that meiotic cohesin SMC1β protects spermatocyte telomeres from damage. The underlying reason, however, remained unknown as the expressions of telomerase and shelterin components were normal in Smc1β -/- spermatocytes. Here. we report that SMC1β restricts expression of the long noncoding RNA TERRA (telomeric repeat containing RNA) in spermatocytes. In somatic cell lines increased TERRA was reported to cause telomere damage through altering telomere chromatin structure. In Smc1β -/- spermatocytes, we observed strongly increased levels of TERRA which accumulate on damaged chromosomal ends, where enhanced R-loop formation was found. This suggested a more open chromatin configuration near telomeres in Smc1β -/- spermatocytes, which was confirmed by ATAC-seq. Telomere-distal regions were not affected by the absence of SMC1β but RNA-seq revealed increased transcriptional activity in telomere-proximal regions. Thus, SMC1β promotes closed chromatin specifically near telomeres and limits TERRA expression in spermatocytes.

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.

Telomeres cooperate in zygotic genome activation by affecting DUX4/Dux transcription

Zygotic genome activation (ZGA) is initiated once the genome chromatin state is organized in the newly formed zygote. Telomeres are specialized chromatin structures at the ends of chromosomes and are reset during early embryogenesis, while the details and significance of telomere changes in preimplantation embryos remain unclear. We demonstrated that the telomere length was shortened in the minor ZGA stage and significantly elongated in the major ZGA stage of human and mouse embryos. Expression of the ZGA pioneer factor DUX4/Dux was negatively correlated with the telomere length. ATAC sequencing data revealed that the chromatin accessibility peaks on the DUX4 promoter region (i.e., the subtelomere of chromosome 4q) were transiently augmented in human minor ZGA. Reduction of telomeric heterochromatin H3K9me3 in the telomeric region also synergistically activated DUX4 expression with p53 in human embryonic stem cells. We propose herein that telomeres regulate the expression of DUX4/Dux through chromatin remodeling and are thereby involved in ZGA.

Telomere attrition and genomic instability in unexplained recurrent pregnancy loss in humans: A preliminary study

Genome instability is defined as an elevated rate of DNA damage and mutations as a result of exposure to potential direct and indirect mutagens. This current investigation was designed to elucidate the genomic instability among couples experiencing unexplained recurrent pregnancy loss (uRPL). A cohort of 1272 individuals with history of unexplained RPL with normal karyotype was retrospectively screened for levels of intracellular ROS production, baseline genomic instability and telomere functionality. The experimental outcome was compared with 728 fertile control individuals. In this study, it was perceived that individuals with uRPL exhibited higher intracellular oxidative stress, along with higher basal levels of genomic instability as compared with the fertile controls. This observation elucidates the role of genomic instability as well as involvement of telomeres in cases of uRPL. It was also observed that higher oxidative stress might be associated with DNA damage and telomere dysfunction resulting in genomic instability among subjects with unexplained RPL. This study highlighted the assessment of genomic instability status in individuals experiencing uRPL.

Epigenomic and Other Evidence for Cannabis-Induced Aging Contextualized in a Synthetic Epidemiologic Overview of Cannabinoid-Related Teratogenesis and Cannabinoid-Related Carcinogenesis

BACKGROUND

Twelve separate streams of empirical data make a strong case for cannabis-induced accelerated aging including hormonal, mitochondriopathic, cardiovascular, hepatotoxic, immunological, genotoxic, epigenotoxic, disruption of chromosomal physiology, congenital anomalies, cancers including inheritable tumorigenesis, telomerase inhibition and elevated mortality.

METHODS

Results from a recently published longitudinal epigenomic screen were analyzed with regard to the results of recent large epidemiological studies of the causal impacts of cannabis. We also integrate theoretical syntheses with prior studies into these combined epigenomic and epidemiological results.

RESULTS

Cannabis dependence not only recapitulates many of the key features of aging, but is characterized by both age-defining and age-generating illnesses including immunomodulation, hepatic inflammation, many psychiatric syndromes with a neuroinflammatory basis, genotoxicity and epigenotoxicity. DNA breaks, chromosomal breakage-fusion-bridge morphologies and likely cycles, and altered intergenerational DNA methylation and disruption of both the histone and tubulin codes in the context of increased clinical congenital anomalies, cancers and heritable tumors imply widespread disruption of the genome and epigenome. Modern epigenomic clocks indicate that, in cannabis-dependent patients, cannabis advances cellular DNA methylation age by 25-30% at age 30 years. Data have implications not only for somatic but also stem cell and germ line tissues including post-fertilization zygotes. This effect is likely increases with the square of chronological age.

CONCLUSION

Recent epigenomic studies of cannabis exposure provide many explanations for the broad spectrum of cannabis-related teratogenicity and carcinogenicity and appear to account for many epidemiologically observed findings. Further research is indicated on the role of cannabinoids in the aging process both developmentally and longitudinally, from stem cell to germ cell to blastocystoids to embryoid bodies and beyond.

Ovarian aging: mechanisms and intervention strategies

Ovarian reserve is essential for fertility and influences healthy aging in women. Advanced maternal age correlates with the progressive loss of both the quantity and quality of oocytes. The molecular mechanisms and various contributing factors underlying ovarian aging have been uncovered. In this review, we highlight some of critical factors that impact oocyte quantity and quality during aging. Germ cell and follicle reserve at birth determines reproductive lifespan and timing the menopause in female mammals. Accelerated diminishing ovarian reserve leads to premature ovarian aging or insufficiency. Poor oocyte quality with increasing age could result from chromosomal cohesion deterioration and misaligned chromosomes, telomere shortening, DNA damage and associated genetic mutations, oxidative stress, mitochondrial dysfunction and epigenetic alteration. We also discuss the intervention strategies to delay ovarian aging. Both the efficacy of senotherapies by antioxidants against reproductive aging and mitochondrial therapy are discussed. Functional oocytes and ovarioids could be rejuvenated from pluripotent stem cells or somatic cells. We propose directions for future interventions. As couples increasingly begin delaying parenthood in life worldwide, understanding the molecular mechanisms during female reproductive aging and potential intervention strategies could benefit women in making earlier choices about their reproductive health.

Hormonal regulation of telomerase activity and hTERT expression in steroid-regulated tissues and cancer

Naturally, in somatic cells chromosome ends (telomeres) shorten during each cell division. This process ensures to limit proliferation of somatic cells to avoid malignant proliferation; however, it leads to proliferative senescence. Telomerase contains the reverse transcriptase TERT, which together with the TERC component, is responsible for protection of genome integrity by preventing shortening of telomeres through adding repetitive sequences. In addition, telomerase has non-telomeric function and supports growth factor independent growth. Unlike somatic cells, telomerase is detectable in stem cells, germ line cells, and cancer cells to support self-renewal and expansion. Elevated telomerase activity is reported in almost all of human cancers. Increased expression of hTERT gene or its reactivation is required for limitless cellular proliferation in immortal malignant cells. In hormonally regulated tissues as well as in prostate, breast and endometrial cancers, telomerase activity and hTERT expression are under control of steroid sex hormones and growth factors. Also, a number of hormones and growth factors are known to play a role in the carcinogenesis via regulation of hTERT levels or telomerase activity. Understanding the role of hormones in interaction with telomerase may help finding therapeutical targets for anticancer strategies. In this review, we outline the roles and functions of several steroid hormones and growth factors in telomerase regulation, particularly in hormone regulated cancers such as prostate, breast and endometrial cancer.

Impact of superovulation and in vitro fertilization on LINE-1 copy number and telomere length in C57BL/6 J mice blastocysts

OBJECTIVE

Millions of babies have been conceived by IVF, yet debate about its safety to offspring continues. We hypothesized that superovulation and in vitro fertilization (IVF) promote genomic changes, including altered telomere length (TL) and activation of the retrotransposon LINE-1 (L1), and tested this hypothesis in a mouse model.

MATERIAL AND METHODS

Experimental study analyzing TL and L1 copy number in C57BL/6 J mouse blastocysts in vivo produced from natural mating cycles (N), in vivo produced following superovulation (S), or in vitro produced following superovulation (IVF). We also examined the effects of prolonged culture on TL and L1 copy number in the IVF group comparing blastocysts cultured 96 h versus blastocysts cultured 120 h. TL and L1 copy number were measured by Real Time PCR.

RESULTS

TL in S (n = 77; Mean: 1.50 ± 1.15; p = 0.0007) and IVF (n = 82; Mean: 1.72 ± 1.44; p < 0.0001) exceeded that in N (n = 16; Mean: 0.61 ± 0.27). TL of blastocysts cultured 120 h (n = 15, Mean: 2.14 ± 1.05) was significantly longer than that of embryos cultured for 96 h (n = 67, Mean: 1.63 ± 1.50; p = 0.0414). L1 copy number of blastocysts cultured for 120 h (n = 15, Mean: 1.71 ± 1.49) exceeded that of embryos cultured for 96 h (n = 67, Mean: 0.95 ± 1.03; p = 0.0162).

CONCLUSIONS

Intriguingly ovarian stimulation, alone or followed by IVF, produced embryos with significantly longer telomeres compared to in vivo, natural cycle-produced embryos. The significance of this enriched telomere endowment for the health and longevity of offspring born from IVF merit future studies.

The role of cellular senescence in female reproductive aging and the potential for senotherapeutic interventions

BACKGROUND

Advanced maternal age is associated with decreased oocyte quantity and quality as well as uterine and placental dysfunctions. These changes lead to infertility, pregnancy complications and birth defects in the offspring. As the mean age of giving birth is increasing worldwide, prevention of age-associated infertility and pregnancy complications, along with the more frequent use of ART, become extremely important. Currently, significant research is being conducted to unravel the mechanisms underlying female reproductive aging. Among the potential mechanisms involved, recent evidence has suggested a contributing role for cellular senescence, a cellular state of irreversible growth arrest characterized by a hypersecretory and pro-inflammatory phenotype. Elucidating the role of senescence in female reproductive aging holds the potential for developing novel and less invasive therapeutic measures to prevent or even reverse female reproductive aging and increase offspring wellbeing.

OBJECTIVE AND RATIONALE

The review will summarize the positive and negative implications of cellular senescence in the pathophysiology of the female reproductive organs during aging and critically explore the use of novel senotherapeutics aiming to reverse and/or eliminate their detrimental effects. The focus will be on major senescence mechanisms of the ovaries, the uterus, and the placenta, as well as the potential and risks of using senotherapies that have been discovered in recent years.

SEARCH METHODS

Data for this review were identified by searches of MEDLINE, PubMed and Google Scholar. References from relevant articles using the search terms 'Cellular Senescence', 'Aging', 'Gestational age', 'Maternal Age', 'Anti-aging', 'Uterus', 'Pregnancy', 'Fertility', 'Infertility', 'Reproduction', 'Implant', 'Senolytic', 'Senostatic', 'Senotherapy' and 'Senotherapeutic' where selected. A total of 182 articles published in English between 2005 and 2020 were included, 27 of which focus on potential senotherapies for reproductive aging. Exclusion criteria were inclusion of the terms 'male' and 'plants'.

OUTCOMES

Aging is a major determinant of reproductive wellbeing. Cellular senescence is a basic aging mechanism, which can be exploited for therapeutic interventions. Within the last decade, several new strategies for the development and repurposing of drugs targeting senescent cells have emerged, such as modulators of the anti-inflammatory response, oxidative stress, DNA damage, and mitochondria and protein dysfunctions. Several studies of female reproductive aging and senotherapies have been discussed that show promising results for future interventions.

WIDER IMPLICATIONS

In most countries of the Organization for Economic Co-operation and Development, the average age at which women give birth is above 30 years. Currently, in countries such as the Netherlands, Australia, Spain, Finland, Germany and the UK, birth rates among 30- to 34-year-olds are now higher than in any other age groups. This review will provide new knowledge and scientific advancement on the senescence mechanisms during female reproductive aging, and benefit fundamental and clinical scientists and professionals in the areas of reproduction, cancer, immunobiology and fibrosis.

N6-Methyladenosine Methylation Regulator RBM15 is a Potential Prognostic Biomarker and Promotes Cell Proliferation in Pancreatic Adenocarcinoma

RNA binding motif protein 15 (RBM15) is a key regulatory factor involved in N6-methyladenosine (m6A) methylation. It has been reported that RBM15 plays an important role in the progress of laryngeal squamous cell carcinoma (LSCC), promoting LSCC migration and invasion. However, the role of RBM15 in human different cancers remains unknown. This study aims to analyze the prognostic value of RBM15, and to demonstrate the correlation between RBM15 expression and tumor immunity, as well as to provide clues for further mechanism research. The results showed that RBM15 was mutated or copy number varied in 25 types of cancer. RBM15 mRNA was abnormally up-regulated across various cancers. Survival analysis suggested high expression of RBM15 was associated with poor prognosis in many cancer types. Among these, it affected patients’ overall survival (OS) in 10 cancer types, disease-free interval (DFI) in 8 cancer types, progression-free interval (PFI) in 12 cancer types and disease-specific survival (DSS) in 7 cancer types. Importantly, in pancreatic adenocarcinoma (PAAD), overexpression of RBM15 is associated with patients’ OS, DFI, PFI, or DSS. In addition, RBM15 expression was positively correlated with immune infiltrating cells in kidney renal clear cell carcinoma (KIRC), brain lower grade glioma (LGG), and PAAD. Moreover, RBM15 expression showed a strong correlation with immune checkpoint markers in PAAD. Cell counting kit-8 (CCK-8) assay showed that knockdown of RBM15 significantly inhibited the proliferation of pancreatic cancer cells. PPI analysis showed USP10, USP24, SMG1, NRAS were closely connected with RBM15 alterations. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that many biological processes (BP), cellular components (CC), molecular functions (MF), cancer related pathways including “sister chromatid cohesion”, “peptidyl-serine phosphorylation”, “cell division”, “nucleoplasm”, “nucleus”, “protein binding”, “protein serine/threonine kinase activity”, “T cell receptor signaling pathway”, “Cell cycle” were regulated by RBM15 alterations. Taken together, pan-cancer analysis of RBM15 suggested it may be served as a prognostic biomarker and immunotherapeutic target for PAAD.

Genomic Instability and Cancer Risk Associated with Erroneous DNA Repair

Many cancers develop as a consequence of genomic instability, which induces genomic rearrangements and nucleotide mutations. Failure to correct DNA damage in DNA repair defective cells, such as in BRCA1 and BRCA2 mutated backgrounds, is directly associated with increased cancer risk. Genomic rearrangement is generally a consequence of erroneous repair of DNA double-strand breaks (DSBs), though paradoxically, many cancers develop in the absence of DNA repair defects. DNA repair systems are essential for cell survival, and in cancers deficient in one repair pathway, other pathways can become upregulated. In this review, we examine the current literature on genomic alterations in cancer cells and the association between these alterations and DNA repair pathway inactivation and upregulation.

CENP-V is required for proper chromosome segregation through interaction with spindle microtubules in mouse oocytes

Proper chromosome segregation is essential to avoid aneuploidy, yet this process fails with increasing age in mammalian oocytes. Here we report a role for the scarcely described protein CENP-V in oocyte spindle formation and chromosome segregation. We show that depending on the oocyte maturation state, CENP-V localizes to centromeres, to microtubule organizing centers, and to spindle microtubules. We find that Cenp-V-/- oocytes feature severe deficiencies, including metaphase I arrest, strongly reduced polar body extrusion, increased numbers of mis-aligned chromosomes and aneuploidy, multipolar spindles, unfocused spindle poles and loss of kinetochore spindle fibres. We also show that CENP-V protein binds, diffuses along, and bundles microtubules in vitro. The spindle assembly checkpoint arrests about half of metaphase I Cenp-V-/- oocytes from young adults only. This finding suggests checkpoint weakening in ageing oocytes, which mature despite carrying mis-aligned chromosomes. Thus, CENP-V is a microtubule bundling protein crucial to faithful oocyte meiosis, and Cenp-V-/- oocytes reveal age-dependent weakening of the spindle assembly checkpoint.

Pan-Cancer Analysis Reveals FH as a Potential Prognostic and Immunological Biomarker in Lung Adenocarcinoma

Fumarate hydratase (FH) is an important enzymatic component in the tricarboxylic acid cycle. Studies have reported that FH plays an important role in hereditary leiomyomatosis and renal cell cancer (HLRCC). However, the role of FH in human different cancers remains unknown. This study is aimed at analyzing the prognostic value of FH and demonstrating the correlation between FH expression and tumor immunity. Results showed that FH was mutated or copy number varied in 27 types of cancer. FH mRNA was abnormally upregulated across various cancers. Survival analysis suggested high expression of FH was associated with poor prognosis in many cancer types, including lung adenocarcinoma (LUAD). Additionally, FH expression was associated with immune infiltration, including B cells, CD4⁺ T cells, CD8⁺ T cells, neutrophils, macrophages, and dendritic cells, especially in liver hepatocellular carcinoma (LIHC), LUAD, and lung squamous cell carcinoma (LUSC). Moreover, FH expression showed a strong correlation with immune checkpoint markers in LUAD and testicular germ cell tumors (TGCT). These results indicate that FH is an immunotherapeutic target and a potential prognostic biomarker in LUAD.

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 Metaphase Chromosomes of Human Triploid Zygotes

The human lifespan is strongly influenced by telomere length (TL) which is defined in a zygote—when two highly specialised haploid cells form a new diploid organism. Although TL is a variable parameter, it fluctuates in a limited range. We aimed to establish the determining factors of TL in chromosomes of maternal and paternal origin in human triploid zygotes. Using Q-FISH, we examined TL in the metaphase chromosomes of 28 human triploid zygotes obtained from 22 couples. The chromosomes’ parental origin was identified immunocytochemically through weak DNA methylation and strong hydroxymethylation in the sperm-derived (paternal) chromosomes versus strong DNA methylation and weak hydroxymethylation in the oocyte-derived (maternal) ones. In 24 zygotes, one maternal and two paternal chromosome sets were identified, while the four remaining zygotes contained one paternal and two maternal sets. For each zygote, we compared mean relative TLs between parental chromosomes, identifying a significant difference in favour of the paternal chromosomes, which attests to a certain “imprinting” of these regions. Mean relative TLs in paternal or maternal chromosomes did not correlate with the respective parent’s age. Similarly, no correlation was observed between the mean relative TL and sperm quality parameters: concentration, progressive motility and normal morphology. Based on the comparison of TLs in chromosomes inherited from a single individual’s gametes with those in chromosomes inherited from different individuals’ gametes, we compared intraindividual (intercellular) and interindividual variability, obtaining significance in favour of the latter and thus validating the role of heredity in determining TL in zygotes. A comparison of the interchromatid TL differences across the chromosomes from sets of different parental origin with those from PHA-stimulated lymphocytes showed an absence of a significant difference between the maternal and paternal sets but a significant excess over the lymphocytes. Therefore, interchromatid TL differences are more pronounced in zygotes than in lymphocytes. To summarise, TL in human zygotes is determined both by heredity and parental origin; the input of other factors is possible within the individual’s reaction norm.

Oxidative stress, antioxidants, hormesis and calorie restriction: The current perspective in the biology of aging

Aging, in a large measure, has long been defined as the resultant of oxidative stress acting on the cells. The cellular machinery eventually malfunctions at the basic level by the damage from the processes of oxidation and the system starts slowing down because of intrinsic eroding. To understand the initial destruction at the cellular level spreading outward to affect tissues, organs and the organism, the relationship between molecular damage and oxidative stress is required to understand. Retarding the aging process is a matter of cumulatively decreasing the rate of oxidative damage to the cellular machinery. Along with the genetic reasons, the decrease of oxidative stress is somehow a matter of lifestyle and importantly of diet. In the current review, the theories of aging and the understanding of various levels of molecular damage by oxidative stress have been emphasized. A broader understanding of mechanisms of aging have been elaborated in terms of effects of oxidative at molecular, mitochondrial, cellular and organ levels. The antioxidants supplementation, hormesis and calorie restriction as the prominent anti-aging strategies have also been discussed. The relevance and the efficacy of the antiaging strategies at system level have also been presented.

Genetics of recurrent pregnancy loss: a review

PURPOSE OF REVIEW

Human reproduction is remarkably inefficient; with pregnancy loss occurring in 10-30% of clinically recognized pregnancies. Of those, 3-5% of couples experience recurrent pregnancy loss (RPL), more than 50% of who never receive an underlying diagnosis. Herein, we review evidence that genetic changes, including pathogenic variant(s) in highly penetrant genes, may provide an explanation for a proportion of couples with pregnancy loss.

RECENT FINDINGS

Genetic abnormalities that may predispose to pregnancy loss include chromosomal aneuploidy, copy number variants, single-gene changes and others. Although previously limited by the need for hypothesis-driven assessment, advancement of various molecular technologies have sheparded in the opportunity to identify molecular cause of highly heterogeneous conditions, including RPL. The identification of causative genetic aberrations associated with RPL demonstrates a promising area of further research.

SUMMARY

The journey of human development from a single-cell zygote to a term infant is complex process. Early research into copy number variants and highly penetrant single-gene changes may provide diagnosis for a proportion of couples with RPL as well as inform genes critical for early human development.

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.

In utero Exposure to Genotoxicants Leading to Genetic Mosaicism: An Overlooked Window of Susceptibility in Genetic Toxicology Testing?

In utero development represents a sensitive window for the induction of mutations. These mutations may subsequently expand clonally to populate entire organs or anatomical structures. Although not all adverse mutations will affect tissue structure or function, there is growing evidence that clonally expanded genetic mosaics contribute to various monogenic and complex diseases, including cancer. We posit that genetic mosaicism is an underestimated potential health problem that is not fully addressed in the current regulatory genotoxicity testing paradigm. Genotoxicity testing focuses exclusively on adult exposures and thus may not capture the complexity of genetic mosaicisms that contribute to human disease. Numerous studies have shown that conversion of genetic damage into mutations during early developmental exposures can result in much higher mutation burdens than equivalent exposures in adults in certain tissues. Therefore, we assert that analysis of genetic effects caused by in utero exposures should be considered in the current regulatory testing paradigm, which is possible by harmonization with current reproductive/developmental toxicology testing strategies. This is particularly important given the recent proposed paradigm change from simple hazard identification to quantitative mutagenicity assessment. Recent developments in sequencing technologies offer practical tools to detect mutations in any tissue or species. In addition to mutation frequency and spectrum, these technologies offer the opportunity to characterize the extent of genetic mosaicism following exposure to mutagens. Such integration of new methods with existing toxicology guideline studies offers the genetic toxicology community a way to modernize their testing paradigm and to improve risk assessment for vulnerable populations. Environ. Mol. Mutagen. 61:55-65, 2020. © 2019 The Authors. Environmental and Molecular Mutagenesis published by Wiley Periodicals, Inc. on behalf of Environmental Mutagen Society.

The deteriorating soma and the indispensable germline: gamete senescence and offspring fitness

The idea that there is an impenetrable barrier that separates the germline and soma has shaped much thinking in evolutionary biology and in many other disciplines. However, recent research has revealed that the so-called 'Weismann Barrier' is leaky, and that information is transferred from soma to germline. Moreover, the germline itself is now known to age, and to be influenced by an age-related deterioration of the soma that houses and protects it. This could reduce the likelihood of successful reproduction by old individuals, but also lead to long-term deleterious consequences for any offspring that they do produce (including a shortened lifespan). Here, we review the evidence from a diverse and multidisciplinary literature for senescence in the germline and its consequences; we also examine the underlying mechanisms responsible, emphasizing changes in mutation rate, telomere loss, and impaired mitochondrial function in gametes. We consider the effect on life-history evolution, particularly reproductive scheduling and mate choice. Throughout, we draw attention to unresolved issues, new questions to consider, and areas where more research is needed. We also highlight the need for a more comparative approach that would reveal the diversity of processes that organisms have evolved to slow or halt age-related germline deterioration.

The mechanisms and clinical application of mosaicism in preimplantation embryos

Embryos containing distinct cell lines are referred to as mosaic embryos, which are considered to be caused by mitotic errors in chromosome segregation during preimplantation development. As the accuracy and resolution of detection techniques improve, more and more mosaic embryos were identified recently. The impacts of mosaic embryos on survival and potential pregnancy outcome have been reported to be diverse in different studies. Because of the universality and clinical significance of mosaicism, it is essential to unravel the mechanisms and consequences with regard to this phenomenon in human pre- and post-implantation embryos. The purpose of this review is to explore the mechanisms, causes of mosaicism, and the development of pre- and post-implantation mosaic embryos in the light of recent emerging data, with the aim of providing new references for clinical applications.

Maternal body mass index affects embryo morphokinetics: a time-lapse study

PURPOSE

To assess the effect of body mass index (BMI) on morphokinetic parameters of human embryos evaluated with time-lapse technology during in vitro culture.

METHODS

A retrospective analysis of ART cycles utilizing time-lapse technology was undertaken to assess the potential impact of maternal BMI on morphokinetic and static morphological parameters of embryo development. The cohort of patients was divided into four groups: 593 embryos from 128 underweight women in group A; 5248 embryos from 1107 normal weight women in group B; 1053 embryos from 226 overweight women in group C; and 286 embryos from 67 obese women in group D.

RESULTS

After adjusting for maternal age, paternal age, and cause of infertility, time to reach five blastomeres (t5) and time to reach eight blastomeres (t8) were longer in obese women compared with normoweight women [50.84 h (46.31-55.29) vs. 49.24 h (45.69-53.22) and 57.89 h (51.60-65.94) vs. 55.66 h (50.89-62.89), adjusted p < 0.05 and adjusted p < 0.01, respectively]. In addition, t8 was also delayed in overweight compared with normoweight women [56.72 h (51.83-63.92) vs. 55.66 h (50.89-62.89), adjusted p < 0.01]. No significant differences were observed among groups with regard to embryo morphology and pregnancy rate. Miscarriage rate was higher in underweight compared with normoweight women (OR = 2.1; 95% CI 1.12-3.95, adjusted p < 0.05).

CONCLUSION

Assessment with time-lapse technology but not by classical static morphology evidences that maternal BMI affects embryo development. Maternal obesity and overweight are associated with slower embryo development.