The interrelationship between female reproductive aging and survival

Chronological and reproductive aging-associated changes in resistance to oxidative stress in post-reproductive female mice

Effort toward reproduction is often thought to negatively influence health and survival. Reproduction has been shown to influence metabolism, but the pathways and mechanisms have yet to be thoroughly elucidated. In the current experiments, our aim was to dissect the role of young and old ovarian tissues in the response to oxidative stress, through changes in liver oxidative stress response proteins. Liver proteins were analyzed in control mice at 4, 13, and 27 months of age and compared to 23-month-old mice which received young ovarian tissue transplants (intact or follicle-depleted) at 13 months of age. In control mice, of the 29 oxidative stress response proteins measured, 31% of the proteins decreased, 52% increased, and 17% were unchanged from 13 to 27 months. The greatest changes were seen during the period of reproductive failure, from 4 to 13 months of age. In transplanted mice, far more proteins were decreased from 13 to 23 months (93% in follicle-containing young ovary recipients; 62% in follicle-depleted young ovary recipients). Neither transplant group reflected changes seen in control mice between 13 and 27 months. Estradiol levels in transplant recipient mice were not increased compared with age-matched control mice. The current results suggest the presence of a germ cell- and estradiol-independent ovarian influence on aging-associated changes in the response to oxidative stress, which is manifest differently in reproductive-aged adults and post-reproductive-aged mice. The results presented here separate chronological and ovarian aging and the influence of estradiol in the response to aging-associated oxidative stress and support a novel, estradiol-independent role for the ovary in female health and survival.

Association between female-specific reproductive factors and leukocyte telomere length

STUDY QUESTION

What are the associations between female-specific reproductive factors and leukocyte telomere length (LTL)?

SUMMARY ANSWER

Early menarche, early menopause, short reproductive lifespan, early age at first birth, multiparity, and use of oral contraceptives (OCs) and hormone replacement therapy (HRT) were associated with shorter LTL.

WHAT IS KNOWN ALREADY

Reproductive factors have been associated with age-related diseases, but their associations with cellular aging, as indicated by LTL, are unclear.

STUDY DESIGN, SIZE, DURATION

This population-based study included 224 965 women aged 40-69 years from the UK Biobank between 2006 and 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women aged 40-69 were included. Female-specific reproductive factors, including age at menarche, age at natural menopause, reproductive lifespan, number of live births, age at first live birth, history of stillbirth, history of miscarriage, and use of OCs and HRT were self-reported. LTL was measured using a validated polymerase chain reaction method. Multiple linear regression and restricted cubic spline models were applied to explore the association between each reproductive factor and LTL.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjustment for potential confounders, early menarche (<12 years; percent change, per unit change in LTL Z score: -1.29%, 95% CI: -2.32%, -0.26%), early menopause (<45 years; percent change: -7.18%, 95% CI: -8.87%, -5.45%), short reproductive lifespan (<30 years; percent change: -6.10%, 95% CI: -8.14%, -4.01%), multiparity (percent change: -3.38%, 95% CI: -4.38%, -2.37%), early age at first live birth (<20 years; percent change: -4.46%, 95% CI: -6.00%, -2.90%), and use of OCs (percent change: -1.10%, 95% CI: -2.18%, -0.02%) and HRT (percent change: -3.72%, 95% CI: -4.63%, -2.80%) were all significantly associated with shorter LTL. However, no significant association was found for history of miscarriage and stillbirth. We observed nonlinear relationships of age at menarche, age at natural menopause, reproductive lifespan, and age at first live birth with LTL (Pnonlinear < 0.05).

LIMITATIONS, REASONS FOR CAUTION

Considering that the participants were predominantly of European ethnicity, the findings may not be generalizable to women of other ethnic backgrounds.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that early menarche, early menopause, short reproductive lifespan, early age at first birth, multiparity, and use of OCs and HRT were associated with shorter LTL, which has been linked to various chronic diseases. The accelerated shortening of telomeres may potentially contribute to the development of chronic diseases related to reproductive factors.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the National Natural Science Foundation of China (82003479, 82073660), Hubei Provincial Natural Science Foundation of China (2023AFB663), and the China Postdoctoral Science Foundation (2019M662646, 2020T130220). The authors have no competing interests to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Proteomic quantification of native and ECM-enriched mouse ovaries reveals an age-dependent fibro-inflammatory signature

The ovarian microenvironment becomes fibrotic and stiff with age, in part due to increased collagen and decreased hyaluronan. However, the extracellular matrix (ECM) is a complex network of hundreds of proteins, glycoproteins, and glycans which are highly tissue specific and undergo pronounced changes with age. To obtain an unbiased and comprehensive profile of age-associated alterations to the murine ovarian proteome and ECM, we used a label-free quantitative proteomic methodology. We validated conditions to enrich for the ECM prior to proteomic analysis. Following analysis by data-independent acquisition (DIA) and quantitative data processing, we observed that both native and ECM-enriched ovaries clustered separately based on age, indicating distinct age-dependent proteomic signatures. We identified a total of 4,721 proteins from both native and ECM-enriched ovaries, of which 383 proteins were significantly altered with advanced age, including 58 ECM proteins. Several ECM proteins upregulated with age have been associated with fibrosis in other organs, but to date their roles in ovarian fibrosis are unknown. Pathways regulating DNA metabolism and translation were downregulated with age, whereas pathways involved in ECM remodeling and immune response were upregulated. Interestingly, immune-related pathways were upregulated with age even in ECM-enriched ovaries, suggesting a novel interplay between the ECM and the immune system. Moreover, we identified putative markers of unique immune cell populations present in the ovary with age. These findings provide evidence from a proteomic perspective that the aging ovary provides a fibroinflammatory milieu, and our study suggests target proteins which may drive these age-associated phenotypes for future investigation.

Estradiol-independent restoration of T-cell function in post-reproductive females

Aging leads to a general decline in protective immunity. The most common age-associated effects are in seen T-cell mediated immune function. Adult mice whose immune systems show only moderate changes in T-cell subsets tend to live longer than age-matched siblings that display extensive T-cell subset aging. Importantly, at the time of reproductive decline, the increase in disease risks in women significantly outpace those of men. In female mice, there is a significant decline in central and peripheral naïve T-cell subsets at the time of reproductive failure. Available evidence indicates that this naïve T-cell decline is sensitive to ovarian function and can be reversed in post-reproductive females by transplantation of young ovaries. The restoration of naïve T-cell subsets due to ovarian transplantation was impressive compared with post-reproductive control mice, but represented only a partial recovery of what was lost from 6 months of age. Apparently, the influence of ovarian function on immune function may be an indirect effect, likely moderated by other physiological functions. Estradiol is significantly reduced in post-reproductive females, but was not increased in post-reproductive females that received new ovaries, suggesting an estradiol-independent, but ovarian-dependent influence on immune function. Further evidence for an estradiol-independent influence includes the restoration of immune function through the transplantation of young ovaries depleted of follicles and through the injection of isolated ovarian somatic cells into the senescent ovaries of old mice. While the restoration of naïve T-cell populations represents only a small part of the immune system, the ability to reverse this important functional parameter independent of estradiol may hold promise for the improvement of post-reproductive female immune health. Further studies of the non-reproductive influence of the ovary will be needed to elucidate the mechanisms of the relationship between the ovary and health.

Stem Cell-Based Therapeutic Strategies for Premature Ovarian Insufficiency and Infertility: A Focus on Aging

Reproductive aging is on the rise globally and inseparable from the entire aging process. An extreme form of reproductive aging is premature ovarian insufficiency (POI), which to date has mostly been of idiopathic etiology, thus hampering further clinical applications and associated with enormous socioeconomic and personal costs. In the field of reproduction, the important functional role of inflammation-induced ovarian deterioration and therapeutic strategies to prevent ovarian aging and increase its function are current research hotspots. This review discusses the general pathophysiology and relative causes of POI and comprehensively describes the association between the aging features of POI and infertility. Next, various preclinical studies of stem cell therapies with potential for POI treatment and their molecular mechanisms are described, with particular emphasis on the use of human induced pluripotent stem cell (hiPSC) technology in the current scenario. Finally, the progress made in the development of hiPSC technology as a POI research tool for engineering more mature and functional organoids suitable as an alternative therapy to restore infertility provides new insights into therapeutic vulnerability, and perspectives on this exciting research on stem cells and the derived exosomes towards more effective POI diagnosis and treatment are also discussed.

Aging and Mesenchymal Stem Cells: Basic Concepts, Challenges and Strategies

Aging and frailty are complex processes implicating multifactorial mechanisms, such as replicative senescence, oxidative stress, mitochondrial dysfunction, or autophagy disorder. All of these mechanisms drive dramatic changes in the tissue environment, such as senescence-associated secretory phenotype factors and inflamm-aging. Thus, there is a demand for new therapeutic strategies against the devastating effects of the aging and associated diseases. Mesenchymal stem cells (MSC) participate in a "galaxy" of tissue signals (proliferative, anti-inflammatory, and antioxidative stress, and proangiogenic, antitumor, antifibrotic, and antimicrobial effects) contributing to tissue homeostasis. However, MSC are also not immune to aging. Three strategies based on MSC have been proposed: remove, rejuvenate, or replace the senescent MSC. These strategies include the use of senolytic drugs, antioxidant agents and genetic engineering, or transplantation of younger MSC. Nevertheless, these strategies may have the drawback of the adverse effects of prolonged use of the different drugs used or, where appropriate, those of cell therapy. In this review, we propose the new strategy of "Exogenous Restitution of Intercellular Signalling of Stem Cells" (ERISSC). This concept is based on the potential use of secretome from MSC, which are composed of molecules such as growth factors, cytokines, and extracellular vesicles and have the same biological effects as their parent cells. To face this cell-free regenerative therapy challenge, we have to clarify key strategy aspects, such as establishing tools that allow us a more precise diagnosis of aging frailty in order to identify the therapeutic requirements adapted to each case, identify the ideal type of MSC in the context of the functional heterogeneity of these cellular populations, to optimize the mass production and standardization of the primary materials (cells) and their secretome-derived products, to establish the appropriate methods to validate the anti-aging effects and to determine the most appropriate route of administration for each case.

Aging-associated changes in motor function are ovarian somatic tissue-dependent, but germ cell and estradiol independent in post-reproductive female mice exposed to young ovarian tissue

A critical mediator of evolution is natural selection, which operates by the divergent reproductive success of individuals and results in conformity of an organism with its environment. Reproductive function has evolved to support germline transmission. In mammalian ovaries, this requires healthy, active gonad function, and follicle development. However, healthy follicles do not contribute to germline transmission in a dead animal. Therefore, support of the health and survival of the organism, in addition to fertility, must be considered as an integral part of reproductive function. Reproductive and chronological aging both impose a burden on health and increase disease rates. Tremors are a common movement disorder and are often correlated with increasing age. Muscle quality is diminished with age and these declines are gender-specific and are influenced by menopause. In the current experiments, we evaluated aging-associated and reproduction-influenced changes in motor function, utilizing changes in tremor amplitude and grip strength. Tremor amplitude was increased with aging in normal female mice. This increase in tremor amplitude was prevented in aged female mice that received ovarian tissue transplants, both in mice that received germ cell-containing or germ cell-depleted ovarian tissue. Grip strength was decreased with aging in normal female mice. This decrease in grip strength was prevented in aged female mice that received either germ cell-containing or germ cell-depleted tissue transplants. As expected, estradiol levels decreased with aging in normal female mice. Estradiol levels did not change with exposure to young ovarian tissues/cells. Surprisingly, estradiol levels were not increased in aged females that received ovaries from actively cycling, young donors. Overall, tremor amplitude and grip strength were negatively influenced by aging and positively influenced by exposure to young ovarian tissues/cells in aged female mice, and this positive influence was independent of ovarian germ cells and estradiol levels. These findings provide a strong incentive for further investigation of the influence of ovarian somatic tissue on health. In addition, changes in tremor amplitude may serve as an additional marker of biological age.

Chromosome Segregation in the Oocyte: What Goes Wrong during Aging

Human female fertility and reproductive lifespan decrease significantly with age, resulting in an extended post-reproductive period. The central dogma in human female reproduction contains two important aspects. One is the pool of oocytes in the human ovary (the ovarian reserve; approximately 10⁶ at birth), which diminishes throughout life until menopause around the age of 50 (approximately 10³ oocytes) in women. The second is the quality of oocytes, including the correctness of meiotic divisions, among other factors. Notably, the increased rate of sub- and infertility, aneuploidy, miscarriages, and birth defects are associated with advanced maternal age, especially in women above 35 years of age. This postponement is also relevant for human evolution; decades ago, the female aging-related fertility drop was not as important as it is today because women were having their children at a younger age. Spindle assembly is crucial for chromosome segregation during each cell division and oocyte maturation, making it an important event for euploidy. Consequently, aberrations in this segregation process, especially during the first meiotic division in human eggs, can lead to implantation failure or spontaneous abortion. Today, human reproductive medicine is also facing a high prevalence of aneuploidy, even in young females. However, the shift in the reproductive phase of humans and the strong increase in errors make the problem much more dramatic at later stages of the female reproductive phase. Aneuploidy in human eggs could be the result of the non-disjunction of entire chromosomes or sister chromatids during oocyte meiosis, but partial or segmental aneuploidies are also relevant. In this review, we intend to describe the relevance of the spindle apparatus during oocyte maturation for proper chromosome segregation in the context of maternal aging and the female reproductive lifespan.

Ovarian recovery via autologous platelet-rich plasma: New benchmarks for condensed cytokine applications to reverse reproductive aging

Health and life expectancy gains have pushed the overall number of menopausal patients to record levels. Because maternal age at first pregnancy also continues to rise, it is unsurprising that reduced birth rates are consistently reported across many populations. Both trends severely strain national demographics and present a socioeconomic challenge for which no satisfactory solution currently exists. Symptomatic menopause and infertility/miscarriage are met with standard therapies like hormone replacement therapy (HRT) and in vitro fertilization, respectively. Although these accepted interventions do supply some cover, both are expensive, low yield, and not without controversy. Meanwhile, ovarian steroid output and competent oocyte availability approach unrecoverable loss beyond age ~35 years, irrespective of treatment. Received wisdom holds that postnatal oogenesis in humans is impossible, a tenet which until recently encountered little serious confrontation. Reassessing this paradigm is overdue given proof‐of‐concept work on native sex steroid rejuvenation, de novo euploid oogenesis, ovulation, blastocyst development, fetal growth, and healthy term livebirths—all apparently possible with intraovarian insertion of platelet‐rich plasma (PRP). Discrete functional analysis of the full platelet‐derived cytokine array carried with PRP unfortunately for now, is incomplete. Here, selected platelet releasate constituents and measured effects are framed to address advances in wellness and women’s health. Emphasis is on cytokines best positioned to enable recovery of senescent ovarian function sufficient to suspend synthetic HRT dependency and/or permit egg retrieval and pregnancy. Whereas the chronicle of progress in other clinical fields does invite generalization of fresh platelet applications to reproductive endocrinology, basic mechanistic questions remain open.

Cell-Free Fat Extract Improves Ovarian Function and Fertility in Mice With Advanced Age

The reduction in the quantity and quality of oocytes is the major factor affecting fertility in women with advanced age, who tend to experience delayed childbearing and declined fertility rate. However, effective therapeutic strategies to combat this decrease in ovarian function are lacking in clinical practice. Thus, identifying a new method to rescue ovarian function and improve reproduction in natural age-related decline in fertility is necessary. Cell-free fat extract (CEFFE) has been verified to possess diverse active proteins exerting anti-aging and proliferation-promoting effects. Nonetheless, whether CEFFE can rescue the decline in aged-related ovarian function and improve the fertility of females with advanced age remains unclear. In this study, a natural aging mouse model, exhibiting similarities to the physiological changes of ovarian senescence, was used to observe the anti-aging effect of CEFFE on ovarian functions. We found that CEFFE, injected via the veins, could recover the levels of the sex hormone, increase angiogenesis and the number of growth follicles in the natural aging mice model. Moreover, CEFFE promoted the development of embryos and increased the litter size of aged mice. Transcriptome analysis of the aged mouse ovaries revealed that CEFFE treatment upregulated the expression of genes involved in the repair of DNA damage. And both in vivo and in vitro experiment proved that CEFFE improved the function of granulosa cells, including promoting proliferation, alleviating senescence, and rescuing DNA damage in aged granulosa cells. Collectively, our study implied that CEFFE improved the ovarian function and fertility of naturally aging mice by ameliorating the overall microenvironment of ovary, which provided a theoretical basis for new anti-aging therapeutic strategies for cell-free therapy in ovaries.