Ovarian Telomerase and Female Fertility

A Molecular Perspective and Role of NAD+ in Ovarian Aging

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

The crosstalk between telomeres and DNA repair mechanisms: an overview to mammalian somatic cells, germ cells, and preimplantation embryos

Telomeres are located at the ends of linear chromosomes and play a critical role in maintaining genomic stability by preventing premature activation of DNA repair mechanisms. Because of exposure to various genotoxic agents, telomeres can undergo shortening and genetic changes. In mammalian cells, the basic DNA repair mechanisms, including base excision repair, nucleotide excision repair, double-strand break repair, and mismatch repair, function in repairing potential damages in telomeres. If these damages are not repaired correctly in time, the unfavorable results such as apoptosis, cell cycle arrest, and cancerous transition may occur. During lifespan, mammalian somatic cells, male and female germ cells, and preimplantation embryos experience a number of telomeric damages. Herein, we comprehensively reviewed the crosstalk between telomeres and the DNA repair mechanisms in the somatic cells, germ cells, and embryos. Infertility development resulting from possible defects in this crosstalk is also discussed in the light of existing studies.

Aging and oocyte competence: A molecular cell perspective

Follicular microenvironment is paramount in the acquisition of oocyte competence, which is dependent on two interconnected and interdependent processes: nuclear and cytoplasmic maturation. Extensive research conducted in human and model systems has provided evidence that those processes are disturbed with female aging. In fact, advanced maternal age (AMA) is associated with a lower chance of pregnancy and live birth, explained by the age-related decline in oocyte quality/competence. This decline has largely been attributed to mitochondria, essential for oocyte maturation, fertilization, and embryo development; with mitochondrial dysfunction leading to oxidative stress, responsible for nuclear and mitochondrial damage, suboptimal intracellular energy levels, calcium disturbance, and meiotic spindle alterations, that may result in oocyte aneuploidy. Nuclear-related mechanisms that justify increased oocyte aneuploidy include deoxyribonucleic acid (DNA) damage, loss of chromosomal cohesion, spindle assembly checkpoint dysfunction, meiotic recombination errors, and telomere attrition. On the other hand, age-dependent cytoplasmic maturation failure is related to mitochondrial dysfunction, altered mitochondrial biogenesis, altered mitochondrial morphology, distribution, activity, and dynamics, dysmorphic smooth endoplasmic reticulum and calcium disturbance, and alterations in the cytoskeleton. Furthermore, reproductive somatic cells also experience the effects of aging, including mitochondrial dysfunction and DNA damage, compromising the crosstalk between granulosa/cumulus cells and oocytes, also affected by a loss of gap junctions. Old oocytes seem therefore to mature in an altered microenvironment, with changes in metabolites, ribonucleic acid (RNA), proteins, and lipids. Overall, understanding the mechanisms implicated in the loss of oocyte quality will allow the establishment of emerging biomarkers and potential therapeutic anti-aging strategies. This article is categorized under: Reproductive System Diseases > Molecular and Cellular Physiology.

Multichannel Recovery Potential with Activated Autologous Intraovarian Platelet-Rich Plasma and Its Derivatives

Platelet-rich plasma (PRP) is an 'orthobiologic' with recognized roles in plastic surgery, musculoskeletal disorders, dentistry, dermatology, and more recently, 'ovarian rejuvenation'. Intraovarian PRP involves a complex secretome discharged after platelet activation, comprising multiple cytokine mediators delivered surgically to older or inactive ovarian tissue. Loss of oocyte meiotic fidelity and impaired fertilization accompanying advanced maternal age are already managed by IVF, but only with eggs provided by younger donors. However, if the observed effect of rectifying embryo ploidy error can be proven beyond case reports and small series, activated PRP (or its condensed plasma cytokines) would deliver a welcome therapeutic disruption that is difficult to overstate. Because shortcomings in ovarian function are presently addressed mainly by pharmacological approaches (i.e., via recombinant gonadotropins, GnRH analogs, or luteal support), autologous PRP would represent an unusual departure from these interventions. Given the diversity of platelet cargo proteins, the target response of intraovarian PRP is probably not confined to oocytes or follicles. For example, PRP manipulates signal networks driving improved perfusion, HOX regulation, N-glycan post-translational modification, adjustment of voltage-gated ion channels, telomere stabilization, optimization of SIRT3, and ribosome and mitochondria recovery in older oocytes. While multichannel signals operating on various pathways are not unique to reproductive biology, in intraovarian PRP this feature has received little study and may help explain why its standardization has been difficult. Against this background, our report examines the research themes considered most likely to shape clinical practice.

Endometriosis: Update of Pathophysiology, (Epi) Genetic and Environmental Involvement

Endometriosis is a chronic disease caused by ectopic endometrial tissue. Endometriotic implants induce inflammation, leading to chronic pain and impaired fertility. Characterized by their dependence on estradiol (via estrogen receptor β (ESRβ)) and their resistance to progesterone, endometriotic implants produce their own source of estradiol through active aromatase. Steroidogenic factor-1 (SF1) is a key transcription factor that promotes aromatase synthesis. The expression of SF1 and ESRβ is enhanced by the demethylation of their promoter in progenitor cells of the female reproductive system. High local concentrations of estrogen are involved in the chronic inflammatory environment favoring the implantation and development of endometriotic implants. Similar local conditions can promote, directly and indirectly, the appearance and development of genital cancer. Recently, certain components of the microbiota have been identified as potentially promoting a high level of estrogen in the blood. Many environmental factors are also suspected of increasing the estrogen concentration, especially prenatal exposure to estrogen-like endocrine disruptors such as DES and bisphenol A. Phthalates are also suspected of promoting endometriosis but throughmeans other than binding to estradiol receptors. The impact of dioxin or tobacco seems to be more controversial.

Telomere Length, a New Biomarker of Male (in)Fertility? A Systematic Review of the Literature

Male factors are suspected in around half cases of infertility, of which up to 40% are diagnosed as idiopathic. In the context of a continuously increased resort to ART and increased decline of semen parameters, it is of greatest interest to evaluate an additional potential biomarker of sperm quality. According to PRISMA guidelines, this systematic review of the literature selected studies evaluating telomere length in sperm and/or in leukocytes as a potential male fertility biomarker. Twenty-two publications (3168 participants) were included in this review of experimental evidence. For each study, authors determined if there was a correlation between telomere length and semen parameters or fertility outcomes. Of the 13 studies concerning sperm telomere length (STL) and semen parameters, ten found an association between short STL and altered parameters. Concerning the impact of STL on ART results, the data are conflicting. However, eight of the 13 included studies about fertility found significantly longer sperm telomeres in fertile men than in infertile men. In leukocytes, the seven studies reported conflicting findings. Shorter sperm telomeres appear to be associated with altered semen parameters or male infertility. Telomere length may be considered as a new molecular marker of spermatogenesis and sperm quality, and thus is related to male fertility potential. However, additional studies are needed to define the place of the STL in the assessment of individual fertility.

Effects of different doses of royal jelly on oxidative stress and telomerase enzyme in rats with Cadmium toxicity

Purpose: Cadmium (Cd) is a toxic metal that seriously threatens human health due to environmental pollution, is widely used in industry and agriculture, and causes oxidative stress and tissue damage. This study aims to examine the effect of royal jelly (RJ) on oxidative status and telomerase enzyme activity in tissue damage induced by Cd. Materials and Methods: The experimental design was made with 6 rats in each group. A total of 6 groups were created: control group, Cd group, 250 mg/kg RJ group, Cd + 250 mg/kg RJ group, 400 mg/kg RJ group, Cd + 400 mg/kg RJ group. In the study, total oxidant status and total antioxidant status in blood serum were investigated by colorimetric method, and telomerase enzyme activity in ovarian tissue was investigated by ELISA method. Results: Cd caused an increase in oxidative capacity (23.80 ± 2.4) and a significant decrease was determined after RJ applications compared to the control group. After RJ application, the best total antioxidant response was observed in the 250 mg/kg RJ and Cd + 250 mg/kg RJ groups. Cd significantly reduced telomerase enzyme activity (0.90 ± 0.13). RJ administered for treatment after Cd application increased telomerase levels up to the control level (1.40 ± 0.05). The best treatment response was observed in the Cd + 250 mg/kg RJ group (1.42 ± 0.05). Conclusion: Cd causes oxidative stress and that RJ may have curative effects by increasing the antioxidant capacity and telomerase enzyme activity RJ is a promising natural product and can contribute to recovery.

Special Issue: "Telomerase: Role in Health and Aging"

We would like to introduce the new volume: "Telomerase and Telomeres: Its Role in Health and Aging 2 [...].