The Global Consortium for Reproductive Longevity and Equality (GCRLE) at the Buck Institute for Research on Aging, made possible by the Bia-Echo Foundation, announces its inaugural recipients of its GCRLE Scholar Awards. The 22 recipients comprise a global group who share a vision of advancing research to better understand the underlying causes of female reproductive aging. Grantees were selected by a Scientific Advisory Council composed of leaders in the fields of Aging and Reproductive Biology. Grantees range from early career scientists to established scholars in the field.
Senior Scholar Award Recipients
Holly Ingraham, PhD
Identifying Novel Drivers in Central Control of Female Reproduction
In this GCRLE-funded project, our main goal is to uncover novel hormone-responsive brain regions that coordinate and maximize reproductive fitness in female mice. As a senior investigator who has worked for 25 years to define sex-dependent mechanisms in the brain and gonads, it is apparent that a major obstacle to new discoveries in reproductive health is the narrow focus and siloed nature of our research area. In stark contrast to the phenomenal progress made in the central control of other processes, such as feeding, concepts as to how the female brain exerts control over ovarian function and optimizes reproduction have fundamentally remained unchanged for the last four decades. Indeed, nearly all studies published to date in this research space have narrowly focused on just a few of the many thousands of neurons subtypes in our brains. With the recent realization that there is an amazing degree of neuronal diversity in the brain, and that neuronal outputs are often different between males and females, we wish to ask whether new, sex-specific neurocircuits exist that are critically important for reproductive physiology.
This new GCRLE initiative provides an unparalleled opportunity to break down traditional barriers and foster discovery-based research that might eventually translate into novel therapeutic strategies to improve reproductive health in women. Building upon our knowledge of estrogen-responsive nodes in brain regions, we aim to identify neurons and signals in the brain that remodel the molecular workings of the ovary to optimize reproduction. In this proposal, we will test the hypothesis that the brain is a key player for reproductive success by directly or indirectly controlling egg quality, ovarian reserve, hormone levels, ovulation, and mating behaviors. This basic information will be foundational for forming a mechanistic understanding of reproductive aging, and importantly, for generating novel treatments for infertility.
Listen to Dr Ingraham present her research in Making Reproductive Longevity a Reality | Episode 2
Coleen Murphy, PhD
Defining a “Clock” for Female Reproductive Decline
Women begin to experience decreased fertility on average in the late 30s to mid-40s, preceding menopause by more than a decade; this decline in reproductive ability is marked by increased rates of infertility, miscarriages, and birth defects that arise from aneuploidies and generally decreased oocyte quality. The range of ages when such problems arise is quite broad (10-15 years), and varies highly from individual to individual. Currently it is not possible for a woman to know where she stands on this scale of age-related oocyte quality decline, as current measures of oocyte quality are both short-range and highly invasive. Here we propose the development of a non-invasive diagnostic that would predict age-related oocyte quality decline to identify changes that are reflected in aging of reproductive tissues, which will accelerate our ability to both study and treat reproductive aging.
The work proposed here will enable the analysis of underlying mechanisms that regulate reproductive aging, and provide women with information about their relative reproductive aging status; this will allow them to make more informed decisions about their reproductive lives, perhaps avoiding maternal age-related infertility, miscarriage, and birth defects. Additionally, a blood diagnostic will allow the development of drug treatments for maternal age-related decline. The ability to diagnose and eventually treat fertility problems early will lower maternal age-related birth defect rates and pregnancy complications.
Mary Zelinski, PhD
Interventions for Ovarian Aging
A woman’s capacity to produce eggs that are capable of being fertilized and carried to term in a healthy pregnancy is called ovarian reserve, and it diminishes with age. Immature eggs are stored inside the ovary in follicles, which have to be activated in order for a mature egg to be released each cycle. The number of women of advanced reproductive ages seeking to have a child has steadily increased; unfortunately, they have few follicles remaining in their ovaries from which to produce healthy eggs. Understanding the mechanisms that control the size of the ovarian reserve as well as the rate of follicle recruitment is paramount for preventing age-related reproductive decline.
Rapamycin is an approved drug that potently suppresses the immune system at high doses, and is approved for treating cancer and reducing the likelihood of rejection after organ transplantation. In rodent models lower doses of rapamycin can extend healthy lifespan as well as reproductive lifespan when administered to older animals. We will use a pre-clinical mammalian model of reproductive aging to test the hypothesis that chronic low dose rapamycin treatment beginning in mid-life may temporarily suppress follicle activation in older females, thereby allowing a greater pool of follicles from which healthy eggs can be obtained at advanced ages. If the rate of primordial follicle activation can be controlled, the potential to produce even a few high-quality eggs would significantly impact fertility in women of advanced reproductive age and improve overall health.
Listen to Dr Zelinski present her research in Making Reproductive Longevity a Reality | Episode 9
Junior Scholar Award Recipients
Bérénice Benayoun, PhD
Establishing new age-relevant mouse models of menopause
Menopause marks the shutdown of female sex-steroid hormones synthesis in humans and is often dismissed as the mere cessation of reproductive capacity. However, later age-at-menopause is a strong predictor for women’s health and longevity, with post-menopausal women being at much higher risk for many age-related diseases. With a mean menopause age of 51 years, women spend a large portion of their life in reproductive senescence. Although laboratory mice show decreased reproductive capacity with aging, they normally poorly recapitulate the process of menopause. Indeed, the most commonly used models of menopause in mice (such as ovariectomy) fail to recapitulate key aspects of human menopause. Further, the few studies that do investigate menopause usually use young animals, thus failing to model the menopausal state in an appropriately aged organism, when menopause would occur in humans.
We hypothesize that the development of complementary, age-relevant rodent models of menopause will help transform our understanding of female aging, and ultimately provide new therapeutic handles to improve women’s health. To address the current lack of well-characterized age-appropriate menopause models, we propose to characterize and compare the outcome of three independent potential models of menopause in rodents, all of which can be used to model menopause in middle-aged mice and with intact ovaries. First, we will characterize the dynamics of “menopause” onset in these animals and evaluate how the animals’ longer-term health is affected by ovarian failure at middle-age. Second, we will extensively characterize the cellular and molecular landscape of ovaries isolated from menopause and control animals using single cell RNA-sequencing. Molecular characterization and comparison across models will allow the identification of potential therapeutic targets. Successful completion of this project will lead to the characterization of novel, age-relevant rodent models of menopause, which will greatly facilitate the inclusion of the impact of menopause in basic studies of aging.
Listen to Dr Benayoun present her research in Making Reproductive Longevity a Reality | Episode 4
Lynae Brayboy, MD
Dysfunctional MDR-1 disrupts mitochondrial homeostasis in the oocyte
Infertility affects 186 million people worldwide, however the cause of one prevalent diagnosis of infertility-diminished ovarian reserve (DOR) (associated with decreased egg (oocyte) quantity and quality)-is unknown and often requires treatment with in vitro fertilization (IVF). One explanation is that egg dysfunction mediated by chronic metabolic stress and toxicity is caused by the loss of detoxification proteins known as multidrug resistance transporters (MDRs). My work seeks to understand how MDRs guard eggs from metabolic stress and toxicants which can lead to infertility and long-term health sequelae. Oocyte quality has been inextricably linked to mitochondrial function. My data show that MDR-1, expressed on both the oocyte and mitochondrial membranes is essential for mitochondrial health. I have additional data showing loss of MDR-1 function leads to poor quality oocytes. The long-term goal of this project is to understand the mechanism of MDR-1 function in oocyte mitochondria.
The overall objective is to test how MDR-1 loss leads to poor oocyte quality/embryo progression, abnormal mitochondrial physiology and DOR. We have a clinical need to understand the pathophysiology of DOR, perhaps the key lies in MDRs. This has led to my hypothesis that MDR-1 directs mitochondrial function and protects oocytes from metabolic stress. I will pursue the following project goals: 1) Investigate how MDR-1 dysfunction impacts oocyte quality and embryo progression The goal is to evaluate the effect of MDR-1 loss on egg quality, which involves two aspects: the capability of the egg to mature normally and provide healthy cellular infrastructure for embryo development. 2) Study how loss of MDR-1 leads to abnormal mitochondrial function in oocytes. Here I will test the contribution of MDR-1 loss on metabolic stress, mitochondrial activity and function in oocytes. 3) Examine how loss of MDR-1 contributes to DOR My aim is to understand the implication of MDR-1 loss on premature ovarian aging. Studying oocyte MDR-1 introduces a novel link between MDR-1 loss, mitochondrial dysfunction and poor oocyte quality leading to infertility. The overall impact will be insight into mechanisms of premature ovarian aging.
Listen to Dr Brayboy present her research in Making Reproductive Longevity a Reality | Episode 7
Ingrid Fetter-Pruneda, PhD
The molecular and cellular basis of high fecundity in social insects
A common trade-off in animals is that an increase in fecundity is associated with a decrease in longevity. This is not the case in social insects such as ants, bees and wasps, where the reproductives (queens) simultaneously have very high fecundity and very long lifespans. The queens of some species of ants, for example, can live up to 30 years while continuously laying eggs. Non-reproductive individuals have much shorter lifespans, from weeks to months, even though they share the same genes.
How and why social insect queens can have such high fecundity and be so long-lived at the same time remains to be answered. My project aims to find genes involved in high fecundity and long healthspan in ants by analyzing differences in gene expression in ovaries and endocrine tissues of longer- and shorter-lived individuals within and between species. We will characterize the function of these genes in an experimentally amenable ant species and in fruit flies, in which there are many molecular tools available. This will allow us to test and manipulate predicted fecundity and reproductive aging pathways in ants and other organisms to identify genes and pathways that could be conserved across species, which may accelerate the development of strategies to increase fecundity and prevent or delay ovarian aging.
Listen to Dr Fetter-Pruneda present her research in Making Reproductive Longevity a Reality | Episode 4
Amanda Kallen, MD
Ovarian Senescence as a Novel Driver of Female Reproductive Aging
The health risks of female reproductive aging are severe and include changes in neuroendocrine hormones, declining bone health and osteoporosis, cardiovascular disease, and cognitive decline. Therefore, women approaching menopause represent a unique group that appears to be at increased risk for long-term health effects. Moreover, human chronological life span has extended dramatically over the last century, while the timing of menopause has remained relatively constant. Thus, women will spend a larger portion of their lives in the post-menopausal period, and the incidence of these comorbidities will increase. In order to address the role that female reproductive aging plays in overall population health and longevity, it is critical to define these molecular processes which underpin the normal physiology of ovarian aging and the decline of ovarian function.
Cellular senescence, a response to cellular insult involving cellular arrest, is a key hallmark of aging in non-reproductive tissues. The senescence biomarker p16, a cyclin-dependent kinase inhibitor which enforces growth arrest, impairs organ function in tissues including kidney and heart and shortens healthy lifespan in mice. Elimination of p16-expressing senescent cells in mice attenuates age-related deterioration of these organs and extends lifespan. p16 is expressed in oocytes of primordial and early primary follicles of 8 week mice, and in follicles at all stages of maturity, with varying expression levels. Moreover, in a mouse model of ovarian failure induced by repetitive superovulation, p16 increased in GCs with successive ouvlations, suggesting that recurrent ovulation may promote senescence and ovarian aging via a p16-mediated pathway
However, the contribution of senescent cells to the naturally aging ovary - specifically, whether a critical accumulation of senescent cells in the ovary is detrimental to ovarian function - is unknown. In studies in which p16-expressing cells were globally eliminated and mouse lifespan was increased, the presence of senescent cells in the reproductive tract and the effect of their clearance on ovarian aging and reproductive lifespan was not evaluated. Therefore, in this proposal, we will utilize a mouse model of ovarian senescence to define the role of senescent cells, and the effect of their clearance, in the aging ovary. Because the ovary contains a heterogeneous population of cell types that critically contribute to follicular survival and whose age-related transcriptomes have not been characterized, we will then utilize human ovarian tissue to characterize the expression of senescence markers in individual ovarian cell types and create a comprehensive cellular atlas of the transcriptome of the ovarian aging. We expect our proposed Aims to generate highly impactful findings with translational relevance to ovarian aging, thus improving the long-term health of over half of the population.
Listen to Dr Kallen present her research in Making Reproductive Longevity a Reality | Episode 5
Pilot Award Recipients
Ivana Celic, PhD
LINE1 Retrotransposons in Female Reproductive Aging
Female reproductive life span is determined by the size of the oocyte pool and oocyte quality. In humans, female fertility starts to decline significantly in the 30s with more rapid loss after the age of 37, but still more than a decade earlier than the function of ovaries ceases and menopause starts. This age-related decline in fertility presents a significant burden on the female workforce, particularly in developing countries, where women often delay childbearing for career choices, only to face struggles with infertility later in life. Therefore, understanding molecular mechanisms affecting oocyte quality is essential for identifying potential therapeutic targets to treat infertility and extend female reproductive life span.
Genomic instability, mainly in the form of chromosomal segregation errors, is the major cause of age-related infertility. Long-lived cells like human oocytes are particularly susceptible to the cumulative effect of DNA damage. Mammalian genomes encode many copies of a potent endogenous mutagen called the LINE1 (L1) retrotransposon, that can cause genome instability and DNA damage. Because of its potentially deleterious effect on the stability of mammalian genomes, L1 expression and activity are tightly controlled and most tissues express undetectable levels of L1. One of the few cell types that express L1 under normal conditions are mammalian germ cells. The physiological role for L1 expression in germ cells is not well defined, but even in this cell type, L1 expression and activity must be tightly controlled. In the male germ line, loss of control of L1 expression leads to meiotic arrest and infertility. In female germ cells, increased expression of L1 correlates with increased oocyte death during fetal development. Although the amount of L1 expressed in aging ovaries has not been examined in detail, there is evidence that L1 expression levels are elevated in other organs of aged mice.
Given that the germ cell environment and the aging process are two cellular states that favor L1 expression, in this project, we will test the hypothesis that the aging process in ovaries allows expression of L1, leading to accumulation of DNA damage and contributing to genomic instability in aging oocytes.
Listen to Dr Celic present her research in Making Reproductive Longevity a Reality | Episode 3
Iain Cheeseman, PhD
Analyzing centromere rejuvenation during female reproductive aging
Female gametes, termed oocytes, are amongst the rarest cells in the human body, but are responsible for transmitting all heritable information from mother to progeny. At birth, human females are endowed with finite numbers of oocytes, which must exist in a paused state that can persist for decades into adulthood until they transformed into fertilization-competent eggs. This requirement for oocytes to persist indefinitely in a paused state, while being poised to re-enter and continue their division is a central challenge for maintaining developmental competency during female reproductive aging. Indeed, errors in oocyte cell division are a leading cause of the reduced fertility, miscarriages, and developmental disorders that increase markedly with reproductive age.
Our goal is to define the changes that occur to core cell division structures during female reproductive aging and to determine the basis for the molecular rejuvenation of these structures, with the ultimate goal of harnessing their rejuvenation to counteract the age-related changes in oocyte fidelity.
Listen to Dr Cheeseman present his research in Making Reproductive Longevity a Reality | Episode 6
Marco Conti, MD
mRNA translation program and oocyte aging
Women’s aging is associated with a decline in fertility that becomes evident already during the third decade of life. This decrease in fertility is becoming a major and urgent concern as women in developed countries are under socio-economic pressure to delay pregnancies. There is general consensus that the decline in fertility of aging women is caused by a decrease in both the number of eggs produced and their quality. Although egg number can be readily monitored in an ART clinic, reliable measurements of egg quality has remained elusive and is currently based mostly on subjective morphological criteria. Our laboratory is exploring and developing new means to quantify egg quality. Since the health of an egg is dependent on the accumulation of proteins necessary to support fertilization and prepare the egg for embryo development and pregnancy, we are investigating how gene expression required to produce proteins is regulated in the egg. Pursuing preliminary data that our lab has generated, we will test the hypothesis that protein production is disrupted with maternal aging. Using the mouse as an experimental model, we have devised new strategies to quantify gene expression in eggs and relate this function to egg quality. Taking advantage of these methods, we propose to generate a large cohort of aging mice as a source of eggs. We will use these mice to quantify gene expression and to define the molecular defects at the base of these age-related defects. The interpretation of the data generated and some measurements will rely on the support and will be done in coordination with scientists at the Buck Institute. Ultimately, we will be able to develop reliable biomarkers of egg quality that will pave the way to new strategies to prevent the decline in egg fitness associated with aging.
Listen to Dr Conti present his research in Making Reproductive Longevity a Reality | Episode 8
Arjumand Ghazi, PhD
Genetic & Chemical Modulation of Splicing to Combat Reproductive Senescence
The process of alternative splicing (AS) allows a cell to generate different types of RNA molecules from a single gene and underlies the staggering diversity of proteins seen in our cells. AS is widespread in all organisms and in humans up to 90% genes are predicted to undergo AS. Errors during splicing have been shown to lead to innumerable diseases including several cancers. Recently, defective AS has also been observed during aging in many species, including humans. Indeed, AS is emerging as a new hallmark of organismal aging. In many animals carrying mutant copies of splicing factors, proteins that bring about AS, defects have been observed within the germ cells i.e., cells that give rise to sperm and ova. Interestingly, genetic variants that change AS efficiency of genes in germ cells have been implicated in influencing the age of menopause in women.
However, the role of AS in reproductive aging has not been addressed systematically in any species. We propose to address this knowledge gap by investigating the mechanism by which a conserved splicing factor, TCER-1, retards reproductive senescence in the model organism C. elegans. Previously, we identified TCER-1 as a longevity-enhancing protein that is critical for reproductive health in C. elegans. Our recent, preliminary studies lead us to hypothesize that TCER-1 retards reproductive aging by regulating AS fidelity. We will test this hypothesis using a combination of genetic and molecular approaches, and investigate how TCER-1 prevents age-related reproductive decline. We will also explore chemicals that alter AS for their therapeutic prospects in delaying reproductive aging. The human counterpart of TCER-1, TCERG1, also regulates AS. Hence, these studies can potentially reveal knowledge of fundamental and clinical relevance to human reproductive longevity.
Listen to Dr Ghazi present her research in Making Reproductive Longevity a Reality | Episode 5
Polina Lishko, PhD
Endocannabinoid signaling in the mammalian ovary and reproductive longevity
The aging of the reproductive systems has broad implications on the well-being of the entire organism. Particularly, the onset of female reproductive aging contributes to the development of other age-associated dysfunctions, such as cardiovascular problems, osteoporosis, and muscular and neurological declines. These progressive deteriorations of physiological functions go hand in hand with the changes in bioactive lipid signaling, such as changes in the function of the endogenous cannabinoid system (ECS) and in the levels of circulating steroid hormones. Interestingly, it appears that the endocannabinoid and steroid systems are closely connected as sex steroid hormones have been found to regulate ECS. Recent research indicates that ECS is active in the ovaries, where it affects egg maturation. Several studies also indicate that the levels of endocannabinoids decrease during aging, while the activity of enzymes that break endocannabinoids down- increases. We recently characterized one of these enzymes, termed α/β hydrolase domain- containing protein 2 (ABHD2). Unlike any other enzymes in this family, ABHD2 brakes down endocannabinoids only when it is activated by steroid progesterone. Thus, due to its unusual functional properties as an unconventional progesterone receptor, ABHD2 links together two major signaling systems: endocannabinoids and sex steroids. Interestingly, ABHD2 is highly expressed in the ovarian stroma – the tissue with a well-established role in the ovarian aging. Our preliminary data indicate that the female Abhd2-deficient mice show delayed reproductive aging. Despite this aging phenotype, little is known about the role of ECS in the ovarian stroma and its contribution to age-related changes in the ovary.
Here, we propose to further investigate the role of ABHD2 in aging and elucidate the signaling pathways by which ABHD2 exerts its action, as well as determine the changes in bioactive lipid profiles that occur with age in the ovaries. The project will utilize transgenic mouse models, genome editing, state-of-the-art electrophysiology, imaging, and mass spectrometry approaches. Based on the exceptional evolutionary conservancy of ABHD2 we can successfully use the mouse as an animal model in our research. This proposal addresses two main questions of broad importance to the physiology of aging: 1) how endocannabinoid-steroid axis participates in ovarian aging, and 2) how this system could be modulated to address age-related disorders and extend the healthy lifespan. The outcome of this research may identify new molecular targets to develop successful methods to treat age-related disorders.
Listen to Dr Lishko present her research in Making Reproductive Longevity a Reality | Episode 2
Zita Santos, PhD, Carlos Ribeiro, PhD
Metabolic reprogramming, dietary nutrients and food cravings in ovary aging
As women age, they experience a decline in fertility as well as an increased risk of miscarriage and birth defects. Senescence is generally associated with physiologic and metabolic alterations. We hypothesise that changes in the ovarian metabolic programs drive reproductive senescence and that this phenomenon can be reduced using targeted dietary interventions. Drosophila melanogaster, has emerged as an important model organism to study metabolism, aging, reproduction and feeding behavior. Drosophila females also undergo a decrease in egg production and egg viability with age. Moreover, we have shown that the metabolic status of the fly germline is critical for fertility. The female germline undergoes a carbohydrate metabolic reprograming required for viable egg production, a process which concomitantly induces a potent sugar appetite. We will use this model organism to explore the prominent metabolic changes that occur during ovarian senescence. We propose to use a combination of single cell RNA sequencing and metabolomics to pinpoint changes in the expression of genes encoding metabolic pathway enzymes and in the abundance of related metabolites in the aging ovarian tissue. In parallel we will characterize the cellular outcomes of ovarian senescence and monitor the feeding behaviour of these animals. This will allow us to devise dietary stratagies to reverse the identified alterations and increase reproduction in old female flies. We believe that this is a powerful path to identify potentially reversible mechanisms underlying reproductive senescence.
Listen to Dr Ribeiro and Dr Santos present their research in Making Reproductive Longevity a Reality | Episode 3 and Episode 8
Yousin Suh, PhD
Genetic Control of Ovarian Aging in Humans
Ovarian aging influences diverse health outcomes in women including lifespan, cardiovascular disease, metabolic syndromes, neurodegenerative disorders and various types of cancer. Yet, the mechanisms behind this broad implication remain elusive. Family and twin studies have demonstrated a strong relationship between genetics and age at menopause. Identification of the genetic factors contributing to age at menopause will provide mechanistic insights into the biological processes underlying ovarian aging.
The work proposed is aimed at uncovering the molecular mechanisms underlying ovarian aging, informed by genetic factors associated with age at menopause in humans. Genome-wide association studies (GWAS) have identified common variants robustly associated with human traits, including age at menopause, and such knowledge is transforming our understanding of human biology. There is increasing evidence that the majority (>90%) of common variants associated with human traits occur in non-coding regions and are enriched in cell type-specific transcriptional regulatory regions, especially within enhancers specific to disease-relevant cell types, suggesting that they contribute to genetic risk by altering gene expression. We hypothesize that genetic variants associated with age at menopause contribute to ovarian aging by altering tissue- and cell-specific transcriptional regulatory programs. We propose a systematic multidisciplinary approach to investigate how menopause risk variants exert their effects on transcription programs by exploiting contemporary computational and experimental technologies.
The objective of this proposal is: 1) To use computational methods to identify a set of candidate causal regulatory variants in enhancers and their target genes that contribute to genetic factors influencing age at menopause, and to create models that can predict candidate genes and pathways of relevance to ovarian aging (Aim 1); 2) To define the ovarian cell types that causal regulatory variants act on by generating cell type-specific regulatory profiles in the ovary during aging (Aim 2); and 3) To experimentally validate the top candidate causal variants and their target genes by assessing the functional impacts of causal regulatory variants on gene expression and gene regulatory networks by using granulosa cell (GC) models differentiated from human embryonic stem cells (hESCs) that are genetically engineered to carry causal enhancer variants, in order to ascertain the causality and biological significance (Aim 3). By defining the age-related factors that drive pathogenic programs of gene expression, thereby predisposing women to reproductive aging, our approach will allow the identification of new intervention targets to maintain reproductive health and healthspan in our aging female population.
Postdoctoral Scholar Award Recipients
Cristina Quesada Candela, PhD
University of Pittsburgh
Proteasomal Targets Driving Meiotic Failure During Reproductive Aging
Reproductive aging is a major concern in our society as more women than ever postpone having children. Advance maternal age is associated with reduced fertility due to a dramatic decline of reproductive fitness beyond the mid-30s. The decline in oocyte quality is associated with defects that cause the wrong number of chromosomes to be partitioned into the developing eggs. Such errors lead to fetuses that have the incorrect number of chromosomes or are aneuploid, a major cause of pregnancy loss and developmental disabilities.
A growing body of evidence suggests that misfolded and damaged proteins accumulate with age and that proteasomal insufficiency itself drives the aging process. The proteasome is a multi-subunit complex that degrades proteins in a controlled and tightly regulated manner in the nucleus and cytoplasm of the cells. Data from our group and others have detected severe defects in chromosome segregation in mutants carrying a structurally compromised proteasome (Ahuja JS et al.,2017; Prasada Rao H.B.D et al., 2017). It has been shown that the proteasome is tethered to chromosomes during meiosis as part of an evolutionarily conserved mechanism for controlling protein dynamics at distinct chromosomal sites, like synaptonemal complex (SC) proteins. These studies suggest that altered stability of components of the SC, the chromosomes scaffold upon which it assembles, or its regulatory binding proteins are affected. For this reason, I am interested in identifying and characterizing proteasome targets relevant for homolog pairing and recombination that could drive meiotic failure in aged females.
Further knowledge of these proteasome targets would allow us to better understand the changes that occur during female reproductive aging and it will give us more tools to pursue reproductive longevity and equality.
Ana Milunovic Jevtic, PhD, DVM
The role of endocannabinoid hydrolase ABHD2 in the ovarian aging
The aging of reproductive systems has broad implications on the homeostasis of an entire organism, as it contributes to the development of other age-associated dysfunctions, such as cardiovascular problems, decrease in bone density, and muscular and neurological decline. Steroid hormones estrogen and progesterone together with gonadotropins are the essential regulators of female reproductive cycle and egg formation. Progesterone signals through either nuclear or membrane receptors and is well known for its role in pregnancy.
We have recently characterized a novel progesterone receptor, termed α/β hydrolase domain–containing protein 2 (ABHD2), that is highly expressed in the ovarian stroma. Our preliminary results suggest ABHD2 plays an important role in the formation of mature and fertile eggs as Abhd2-deficient mice produce a significantly higher number of fertile eggs than wild-type mice, and overall display delayed reproductive aging. Unlike other progesterone receptors, ABHD2 is an enzyme that regulates the levels of endogenous cannabinoid 2-arachidonoylglycerol (2-AG). Recent studies indicate that 2-AG levels decrease in the aging tissues, while the activity of 2-AG degrading enzymes increases. Our goal is to explore ABHD2 as a potential candidate to regulate reproductive aging. Additionally, ABHD2 may represent a necessary link between steroid and endocannabinoid systems which emphasizes its role in the regulation of female fertility.
Gul Soygur Kaya, PhD
How duration of meiotic prophase affects development and aging of oocytes
While life expectancy has increased remarkably, the age-related decline in female fertility remains a problem. As women age, the diminishing number of eggs and increased risk of having a child with an abnormal number of chromosomes (or aneuploidy, such as Down Syndrome) is compounded by social trends towards delaying childbirth. A major challenge to studying the egg is that critical events in its formation occur when a woman is still developing in her mother’s womb. The goal of this project is to use genetic engineering and imaging technologies in the laboratory mouse to connect the events in the early development of egg precursors to reproductive aging. A critical process in the formation of eggs during fetal life is the specialized cell division known as meiosis. Errors during the early stages of meiosis contribute to aneuploidy, but it remains unclear whether the increase in aneuploidy of eggs with maternal age results from pre-existing differences in eggs or accumulated damage over time. Although human egg development is asynchronous, it is not known whether the timing and length of meiosis has consequences for egg function and fertility. In mice, we discovered that the duration of early meiosis depends on the time of meiotic entrance, suggesting a connection between fetal development and the fidelity of meiosis.
Using tools we developed to mark cells in living mice, we will trace the fate of eggs from meiotic initiation in the fetus through aging, comparing fitness and metabolism between eggs with earlier and shorter meiosis and those with later and faster meiosis. This work will bridge the gap between fetal egg development and adult function, identifying molecular heterogeneity within the egg population associated with developmental differences could provide tools for predicting or augmenting egg quality during aging.
Listen to Dr Gul Soygur Kaya present her research in Making Reproductive Longevity a Reality | Episode 6
Min Hoo Kim, PhD
Elucidating causal effects of the microbiome on reproductive aging
Menopause is a key event in female aging that has significant impact on the overall well-being of the individual. Despite current understanding on the negative impacts of menopause, the underlying molecular mechanism and key factors that contribute to menopause progression are not fully understood. Cumulative studies have suggested a close functional relationship between the gut microbiome and ovarian function. The adult human gut microbiome is believed to be composed of approximately 10 to 100 trillion micro-organisms. With its numbers exceeding that of human cells by more than 10-folds, the microbiome is believed to have a more prominent effect on the host than previously perceived. For example, the human gut microbiome was shown to metabolize estrogen substrates, regulating the concentration of circulating estrogen in the bloodstream. Additionally, a study showed that transplantation of microbial species extracted from Polycystic Ovary Syndrome patients to mice induces significant ovarian dysfunction in the recipient mice. Although a bidirectional relationship between the microbiome and female reproductive function has been considered, a direct causal role has never been established.
The proposed study aims to elucidate the causal functions of the gut microbiome in ovarian aging. In order to characterize the effects of the microbiome on ovarian aging, microbial species from reproductively senescent intact females and from a mouse model of menopause (including pre-, peri- and post-“menopausal” states) will be collected. The collected microbial extracts will be transferred to young female mice with established regular estrus cycling. Changes in ovarian function, including serum hormone levels and histology, and to the microbiome, including metagenomics, will be regularly monitored and analyzed. Using the state-of-the-art microbiome analysis pipelines, specific metabolic pathways that participate in ovarian aging will be identified and characterized. The identification of molecular pathways underlying microbiome-driven female reproductive aging will not only contribute to our understanding of ovarian aging, but also has a great potential to drive novel therapeutic developments.
Listen to Dr Kim present her research in Making Reproductive Longevity a Reality | Episode 7
Seungsoo Kim, PhD
Integrative bioinformatic analysis of human ovarian aging and healthspan
The age at menopause has impacts on a broad range of health outcomes such as coronary heart disease, heart failure, type 2 diabetes, respiratory disease mortality, body mass index, bone mineral density, bone fracture, and various cancers. Multiple epidemiological studies reported that the late onset of menopause is significantly correlated with longer life expectancy. However, the biological mechanisms underlying the genetic contributions to female reproductive aging and age at menopause are still unknown. In this study, we hypothesize that genetic factors impacting age at menopause also influence risk for many age-related diseases, as well as longevity. By uncovering the shared genetic architectures between age at menopause and age-related diseases, we hope to identify common genes and pathways, revealing the genetic drivers underlying female reproductive aging. The main goals of this project are 1) to uncover phenotypic associations between age at menopause and longevity, healthspan, and age-related diseases, and 2) to determine the shared genetic architecture between these traits, identifying the underlying genes and pathways.
To achieve these goals, we propose to utilize population-scale trait and genetic data from the 500,000 participants of the UK Biobank, applying robust statistical approaches such as mixed linear models, polygenic risk scores, linkage disequilibrium score regression, and Mendelian randomization, to complete the following aims: In Aim 1, we will test for phenotypic associations between age at menopause and longevity, age-related diseases and healthspan. In Aim 2, we will determine the shared genetic structures of female reproductive aging, lifespan, healthspan, and age-related disease, and identify the underlying genes and pathways. By uncovering the shared genetic architecture between a major proxy for female reproductive aging, age at menopause, and complex traits such as age-related disease, we will be able to identify genetic drivers of female reproductive aging.
Olfat Malak, PhD
Role of sympathetic transmission in the regulation of ovarian aging
It is well appreciated that after the age of 30, women experience a lower chance of pregnancy accompanied by a sharp decline in egg quality. However, we know little about the mechanisms responsible for this age-dependent decline. Our proposal will address this unmet need by studying the role of neuronal innervation of the ovaries in the regulation of egg quality and ovarian longevity in aging mice. Ovaries and their vasculature are richly innervated by autonomic sympathetic neurons, and mounting evidence over the past decade in women and animal models suggests that aging is accompanied by an increase in sympathetic activity.
In addition, accumulating evidence in animal models indicates that metabolic conditions such as diabetes and high fat diet-induced obesity can compromise ovarian function and egg quality while increasing sympathetic drive. It is, therefore, conceivable, that interventions that could reduce sympathetic drive in old mice could have beneficial effects on the ovarian function and longevity. Despite these studies, the functional link between sympathetic activity and ovarian function is poorly understood, and we lack a mechanistic understanding of how this functional link is affected by aging or under chronic metabolic conditions. I propose to develop a model for studying the role of sympathetic transmission in the regulation of ovarian function. I hypothesize that genetic and/or pharmacological reduction in sympathetic transmission in old mice, or high fat diet- induced obese mice, can improve ovarian function and oocyte quality.
This proposal combines a genetic approach with imaging, electrophysiology and biochemistry in mice to investigate the consequence of genetic and/or pharmacological manipulation of sympathetic input in ovarian health and oocyte quality. Our proposed experiments will provide important insights into ovarian biology and will establish a novel paradigm for testing pharmacological and genetic interventions aimed at countering ovarian decline as a result of aging.
Farners Amargant i Riera, PhD
Targeting fibrosis and inflammation to extend reproductive longevity
Female reproductive aging refers to the loss of reproductive function that starts when women reach their mid-thirties and ends at menopause, resulting in infertility and hormonal perturbations. Medical advances have resulted in increased life expectancy; however, menopause still occurs at around age 50. After menopause, estrogen levels decrease, affecting the function of the reproductive system as well as downstream organs, such as the bones, the heart and the brain. The development of new approaches to delay reproductive aging will enhance reproductive longevity and delay general adverse health outcomes of aging. We recently discovered that the ovarian microenvironment or stroma in which oocytes develop changes with age. Specifically, collagen I/III accumulates, resulting in fibrosis. Concurrently, a pro-inflammatory milieu develops with a significant increase in pro-inflammatory cytokine production, including interleukin-6. These changes in the milieu likely influences oocyte quality.
Here we will test the hypothesis that targeting stromal fibrosis and inflammation can extend reproductive longevity, maintain endocrine function, and improve overall health outcomes. To test this hypothesis, we will establish a preclinical pipeline using mice to test whether anti-fibrotic and anti-inflammatory drugs can delay reproductive aging phenotypes. Beginning at 7 months, when fibrosis is first observed in the ovarian stroma, we will transplant an osmotic pump to continuously deliver a broad spectrum anti-fibrotic drug, an anti-inflammatory drug, or the combination of both directly to the ovary. The treatment will be performed for a total of 6-weeks, and mice in each experimental cohort will be analyzed at 0-, 2- and 4-months post-treatment to evaluate ovarian fibrosis and inflammation, reproductive longevity by analyzing the ovarian reserve, and bone mass density as a read out of overall health. This work has translational potential because fibrosis and inflammation are hallmarks of the aging ovarian microenvironment also in humans. Furthermore, it will establish a pre-clinical model to screen drugs which enhance reproductive longevity and overall health, which could be used in the future to test new therapeutic approaches.
Listen to Dr Amargant present her research in Making Reproductive Longevity a Reality | Episode 9
Zijing Zhang, PhD
The impact of ovarian macrophage population on mouse ovarian aging
For women, the ovary is a very important organ which produce not only eggs, but also hormones that regulate bodily functions. However, the ovary is quite “short-lived”, as its function starts to deteriorate early in life. This natural decline in ovarian functions, or ovarian aging, is a main cause behind the reduction of women’s fertility around the age of 35 and the loss of fertility at menopause around the age of 51. The ovary goes through a lot of changes over the course of aging. Previous studies in mice and human found marked signs of inflammation in ovaries from the old individuals, which point to altered immune cell activities in the ovary as the individual age. In line with these findings, our recent study revealed fundamental changes in several properties of the macrophages in the old ovaries. Macrophages are a major type of immune cells with a diverse of functions and behaviors in different settings. They are known to “swallow up” foreign bodies and cell debris, and produce many chemical signals that help coordinate other cells to protect the host and amend the damaged tissues. These functions not only serve to fight infections, but are also important for keeping normal tissues intact and healthy.
The proposed study aims to investigate how the changes in macrophage properties in the old ovaries affect the functions of the ovary. Using the mouse model, I will first examine how gene expression and chemical production differ between macrophages from the young and the old ovaries. Then I will test how the altered macrophage activities influence the growth, survival and hormone production capability of the ovarian follicles (egg with its supporting cells in the ovary). The proposed study represents a novel direction in the research on ovarian aging. Clarifying the role of macrophages in ovarian aging will inform the development of new treatment strategies that mitigate the effect of ovarian aging.