Reproductive Aging in Caenorhabditis elegans: From Molecules to Ecology

Genome-Wide Temporal Gene Expression Reveals a Post-Reproductive Shift in the Nematode Caenorhabditis briggsae

The nematodes Caenorhabditis briggsae and its well-known cousin Caenorhabditis elegans offer many features for comparative investigations of genetic pathways that affect physiological processes. Reproduction is one such process that directly impacts longevity due to its significant energetic demands. To study gene expression changes during reproductive and post-reproductive phases in both these nematodes, we conducted whole-genome transcriptome profiling at various adult stages. The results revealed that the majority of differentially expressed (DE) genes were downregulated during the reproductive period in both species. Interestingly, in C. briggsae, this trend reversed during post-reproduction, with three-quarters of the DE genes becoming upregulated. Additionally, a smaller set of DE genes showed an opposite expression trend, i.e. upregulation followed by post-reproductive downregulation. Overall, we termed this phenomenon the "post-reproductive shift". In contrast, the post-reproductive shift was much less pronounced in C. elegans. In C. briggsae, DE genes were enriched in processes related to the matrisome, muscle development and function during the reproductive period. Post-reproductive downregulated genes were enriched in DNA damage repair, stress response, and immune response. Additionally, terms related to fatty acid metabolism, catabolism, and transcriptional regulation exhibited complex patterns. Experimental manipulations in C. briggsae to affect their reproductive status predictably altered gene expression, providing in vivo support for the post-reproductive shift. Overall, our study reveals novel gene expression patterns during reproductive and post-reproductive changes in C. briggsae. The data provide a valuable resource for cross-sectional comparative studies in nematodes and other animal models to understand evolution of genetic pathways affecting reproduction and aging.

Network Pharmacology Combined with Experimental Validation to Investigate the Effects and Mechanisms of Aucubin on Aging-Related Muscle Atrophy

Aucubin (AU) is one of the main components of the traditional Chinese medicine Eucommia ulmoides Oliv (EU). This study investigated the effects of AU on aging-related skeletal muscle atrophy in vitro and in vivo. The results of network pharmacology revealed the potential therapeutic effects of AU on muscle atrophy. In vitro, AU effectively attenuated D-gal-induced cellular damage, reduced the number of senescence-associated β-galactosidase (SA-β-Gal)-positive cells, down-regulated the expression levels of muscle atrophy-related proteins Atrogin-1 and MuRF1, and improved myotube differentiation, thereby mitigating myotube atrophy. Notably, AU was found to attenuate oxidative stress and apoptosis in skeletal muscle cells by reducing ROS production, regulating Cleaved caspase3 and BAX/Bcl-2 expression in apoptotic pathways, and enhancing Sirt1 and PGC-1α signaling pathways. In vivo studies demonstrated that AU treatment extended the average lifespan of Caenorhabditis elegans (C. elegans), increased locomotor activity, improved body wall muscle mitochondrial content, and alleviated oxidative damage in C. elegans. These findings suggested that AU can ameliorate aging-related muscle atrophy and show significant potential in preventing and treating muscle atrophy.

Anti-aging activities of an ethanolic extract of Lycium ruthenicum in Caenorhabditis elegans based on metabonomic analysis

The fruits of Lycium ruthenicum Murr. (Solanaceae) are employed in ethnomedicine and used as a functional food. Their antioxidant, anti-aging, and hypolipidemic activities have been investigated in modern research. This study indicated that the ethanolic extract of the fruits of L. ruthenicum Murr. (LRM) improved oxidative and heat stress tolerance, reduced the accumulation of lipofuscin, and retarded the aging process in Caenorhabditis elegans (Rhabditidae). Furthermore, the pharyngeal pumping rate and body length decreased under LRM treatment. Moreover, metabolomic analysis and the DPClusO algorithm revealed that LRM regulated a series of lifespan-related pathways centered on glycine, serine, and threonine metabolism. These results suggest that LRM prolongs the lifespan of Caenorhabditis elegans via dietary restriction. Moreover, feruloyl putrescine, a kind of polyamine, was found in differential metabolites, which may be the metabolite of caffeoyl-spermidine in LRM. These findings from this exploratory study offer a new insight into the roles of L. ruthenicum in anti-aging activity as a functional food.

Synthetic Cathinones Induce Developmental Arrest, Reduce Reproductive Capacity, and Shorten Lifespan in the C. elegans Model

Drug abuse presents a significant global health challenge as the illicit drug market progresses from classic drugs to a growing prevalence of New Psychoactive Substances (NPS), particularly synthetic cathinones, which, although illegal, are often falsely marketed as safe and legal alternatives. The rapid increase in the use of these drugs complicates the assessment of their safety and effects on human health. However, they pose unique toxicological concerns that remain largely uncharacterized. This study investigated the toxic effects of three synthetic cathinones, namely, methylone, pentedrone, and 4-methylethcathinone (4-MEC), using the model organism C. elegans. We assessed the impact of these substances on animal survival, development, reproductive behavior, and longevity. Our results showed that short-term exposure (24 h) to concentrations of 5.0 mM or higher significantly reduced animal survival rates, while prolonged exposure (72 h) led to more pronounced toxicity, significantly reducing survival rates at concentrations as low as 1.0 mM. Moreover, sublethal concentrations resulted in developmental arrest. Additionally, pentedrone impaired reproductive capacity, while 4-MEC significantly shortened C. elegans lifespan. These findings highlight the urgent need for further investigation into the implications of synthetic cathinone use on human health through in vivo models as their prevalence in the illicit drug market continues to rise.

A Transition From Interindividual Uniformity to Diversity in Appearance and Transcriptional Features at Midlife in Caenorhabditis elegans

During embryogenesis, organisms function as a robust system that ensures uniformity within individuals, but they lose robustness and develop variations at advanced ages. However, when and how organisms lose this robustness remains largely elusive. Here, we identified a sharp transition from interindividual uniformity to diversity in the appearance and transcriptional features of age-matched Caenorhabditis elegans in midlife. Convolutional neural network analysis of individual appearance alterations revealed that the transition occurs in midlife, which coincides with the cessation of egg-laying activity and increased motility defects. This period represents the transition from the young state, marked by shared homogeneous features among same-age individuals, to the old state, marked by shared among old individuals. Transcriptional coherence within the age-matched individuals shows essentially the same transition, coinciding with the appearance features. These findings provide a new framework for understanding the aging trajectory in C. elegans, demonstrating the occurrence of the loss of robust control over appearance and transcriptional homeostasis in midlife.

Genetic variation in age-dependent attractiveness in a fish with a mixed mating system

Reproductive senescence is common across taxa and females often show a predictable decline in fecundity after maturity. Attending to these age-dependent cues could help males make optimal mate choice decisions. Here, we examined reproductive senescence and male mate choice in the androdioecious mangrove rivulus (Kryptolebias marmoratus), where self-fertilizing hermaphrodites exist with rare males. Hermaphrodites showed a strong decline in fecundity as they aged and genetic lineages varied in their fecundity at both young and old ages. Surprisingly, when given a simultaneous choice between genetically identical old and young hermaphrodites, males did not simply prefer younger hermaphrodites. Instead, male preference for younger versus older partners depended on the genetic lineage of the partners, resulting in a strong genotype × age interaction. For some genetic lineages, hermaphrodites were more attractive to males when younger, but for other genetic lineages, hermaphrodites were more attractive when older. Our results suggest that the genetic identity of the partner is key to how males weigh age-dependent changes in fecundity and that males are able to assess genetic variation in attractiveness over a partner's reproductive lifespan. Exploring how gamete viability and outcrossing are affected by age across genetic lineages could help us further understand these male preferences.

Cannabinoids and healthy ageing: the potential for extending healthspan and lifespan in preclinical models with an emphasis on Caenorhabditis elegans

There is a significant global upsurge in the number and proportion of older persons in the population. With this comes an increasing prevalence of age-related conditions which pose a major challenge to healthcare systems. The development of anti-ageing treatments may help meet this challenge by targeting the ageing process which is a common denominator to many health problems. Cannabis-like compounds (cannabinoids) are reported to improve quality of life and general well-being in human trials, and there is increasing preclinical research highlighting that they have anti-ageing activity. Moreover, preclinical evidence suggests that endogenous cannabinoids regulate ageing processes. Here, we review the anti-ageing effects of the cannabinoids in various model systems, including the most extensively studied nematode model, Caenorhabditis elegans. These studies highlight that the cannabinoids lengthen healthspan and lifespan, with emerging evidence that they may also hinder the development of cellular senescence. The non-psychoactive cannabinoid cannabidiol (CBD) shows particular promise, with mechanistic studies demonstrating it may work through autophagy induction and activation of antioxidative systems. Furthermore, CBD improves healthspan parameters such as diminishing age-related behavioural dysfunction in models of both healthy and accelerated ageing. Translation into mammalian systems provides an important next step. Moreover, looking beyond CBD, future studies could probe the multitude of other cannabis constituents for their anti-ageing activity.

Reduced insulin/IGF-1 signalling upregulates two anti-viral immune pathways, decreases viral load and increases survival under viral infection in C. elegans

Reduced insulin/IGF-1 signalling (rIIS) improves survival across diverse taxa and there is a growing interest in its role in regulating immune function. Whilst rIIS can improve anti-bacterial resistance, the consequences for anti-viral immunity are yet to be systematically examined. Here, we show that rIIS in adult Caenorhabditis elegans increases the expression of key genes in two different anti-viral immunity pathways, whilst reducing viral load in old age, increasing survival and reducing rate-of-senescence under infection by naturally occurring positive-sense single-stranded RNA Orsay virus. We found that both drh-1 in the anti-viral RNA interference (RNAi) pathway and cde-1 in the terminal uridylation-based degradation of viral RNA pathway were upregulated in early adulthood under rIIS and increased anti-viral resistance was not associated with reproductive costs. Remarkably, rIIS increased anti-viral gene expression only in infected worms, potentially to curb the costs of constitutively upregulated immunity. RNA viruses are found across taxa from plants to mammals and we demonstrate a novel role for rIIS in regulating resistance to viral infection. We therefore highlight this evolutionarily conserved signalling pathway as a promising therapeutic target to improve anti-viral immunity.

Life history in Caenorhabditis elegans: from molecular genetics to evolutionary ecology

Life history is defined by traits that reflect key components of fitness, especially those relating to reproduction and survival. Research in life history seeks to unravel the relationships among these traits and understand how life history strategies evolve to maximize fitness. As such, life history research integrates the study of the genetic and developmental mechanisms underlying trait determination with the evolutionary and ecological context of Darwinian fitness. As a leading model organism for molecular and developmental genetics, Caenorhabditis elegans is unmatched in the characterization of life history-related processes, including developmental timing and plasticity, reproductive behaviors, sex determination, stress tolerance, and aging. Building on recent studies of natural populations and ecology, the combination of C. elegans' historical research strengths with new insights into trait variation now positions it as a uniquely valuable model for life history research. In this review, we summarize the contributions of C. elegans and related species to life history and its evolution. We begin by reviewing the key characteristics of C. elegans life history, with an emphasis on its distinctive reproductive strategies and notable life cycle plasticity. Next, we explore intraspecific variation in life history traits and its underlying genetic architecture. Finally, we provide an overview of how C. elegans has guided research on major life history transitions both within the genus Caenorhabditis and across the broader phylum Nematoda. While C. elegans is relatively new to life history research, significant progress has been made by leveraging its distinctive biological traits, establishing it as a highly cross-disciplinary system for life history studies.

Strengths and limitations of the worm development and activity test (wDAT) as a chemical screening tool for developmental hazards

The worm Development and Activity Test (wDAT) measures C. elegans developmental milestone acquisition timing and stage-specific spontaneous locomotor activity (SLA). Previously, the wDAT identified developmental delays and SLA level changes in C. elegans with mammalian developmental toxicants arsenic, lead, and mercury. 5-fluorouracil (5FU), cyclophosphamide (CP), hydroxyurea (HU), and ribavirin (RV) are teratogens that also induce growth retardation in developing mammals. In at least some studies on each of these chemicals, fetal weight reductions were seen at mammalian exposures below those that had teratogenic effects, suggesting that screening for developmental delay in a small alternative whole-animal model could act as a general toxicity endpoint to identify chemicals for further testing for more specific adverse developmental outcomes. Consistent with mammalian developmental effects, 5FU, HU, and RV were associated with developmental delays with the wDAT. Exposures associated with developmental delay induced hypoactivity with 5FU and HU, but slight hyperactivity with RV. CP is a prodrug that requires bioactivation by cytochrome P450s for both therapeutic and toxic effects. CP tests as a false negative in several in vitro assays, and it was also a false negative with the wDAT. These results suggest that the wDAT has the potential to identify some developmental toxicants, and that a positive wDAT result with an unknown may warrant further testing in mammals. Further assessment with larger panels of positive and negative controls will help qualify the applicability and utility of this C. elegans wDAT assay within toxicity test batteries or weight of evidence approaches for developmental toxicity assessment.

Reproductive Toxicity and Multi/Transgenerational Effects of Emerging Pollutants on C. elegans

Emerging pollutants (EPs) are receiving increasing attention due to the threats they pose to the environment and human health. As EPs continue to emerge, risk assessment requires many model animals. Caenorhabditis elegans (C. elegans) has been an outstanding toxicological model organism due to its growth and development characteristics. Particularly, in studying the transgenerational influences of EPs, C. elegans has advantages in saving time and cost due to its short generation cycle. As infertility has become a major problem in human reproductive health, reproductive toxicities of EPs on contemporary nematodes and across generations of C. elegans were introduced in this review. Moreover, the underlying mechanisms involved in germ cell apoptosis, spermatogenesis, and epigenetic alteration were discussed. Future research opportunities and challenges are also discussed to expand our understanding of the reproductive influences of EPs.

Neuropeptide inactivation regulates egg-laying behavior to influence reproductive health in Caenorhabditis elegans

Neural communication requires both fast-acting neurotransmitters and neuromodulators that function on slower timescales to communicate. Endogenous bioactive peptides, often called "neuropeptides," comprise the largest and most diverse class of neuromodulators that mediate crosstalk between the brain and peripheral tissues to regulate physiology and behaviors conserved across the animal kingdom. Neuropeptide signaling can be terminated through receptor binding and internalization or degradation by extracellular enzymes called neuropeptidases. Inactivation by neuropeptidases can shape the dynamics of signaling in vivo by specifying both the duration of signaling and the anatomic path neuropeptides can travel before they are degraded. For most neuropeptides, the identity of the relevant inactivating peptidase(s) is unknown. Here, we established a screening platform in C. elegans utilizing mass spectrometry-based peptidomics to discover neuropeptidases and simultaneously profile the in vivo specificity of these enzymes against each of more than 250 endogenous peptides. We identified NEP-2, a worm ortholog of the mammalian peptidase neprilysin-2, and demonstrated that it regulates specific neuropeptides, including those in the egg-laying circuit. We found that NEP-2 is required in muscle cells to regulate signals from neurons to modulate both behavior and health in the reproductive system. Taken together, our results demonstrate that peptidases, which are an important node of regulation in neuropeptide signaling, affect the dynamics of signaling to impact behavior, physiology, and aging.

The C. elegans Myc-family of transcription factors coordinate a dynamic adaptive response to dietary restriction

Dietary restriction (DR), the process of decreasing overall food consumption over an extended period of time, has been shown to increase longevity across evolutionarily diverse species and delay the onset of age-associated diseases in humans. In Caenorhabditis elegans, the Myc-family transcription factors (TFs) MXL-2 (Mlx) and MML-1 (MondoA/ChREBP), which function as obligate heterodimers, and PHA-4 (orthologous to FOXA) are both necessary for the full physiological benefits of DR. However, the adaptive transcriptional response to DR and the role of MML-1::MXL-2 and PHA-4 remains elusive. We identified the transcriptional signature of C. elegans DR, using the eat-2 genetic model, and demonstrate broad changes in metabolic gene expression in eat-2 DR animals, which requires both mxl-2 and pha-4. While the requirement for these factors in DR gene expression overlaps, we found many of the DR genes exhibit an opposing change in relative gene expression in eat-2;mxl-2 animals compared to wild-type, which was not observed in eat-2 animals with pha-4 loss. Surprisingly, we discovered more than 2000 genes synthetically dysregulated in eat-2;mxl-2, out of which the promoters of down-regulated genes were substantially enriched for PQM-1 and ELT-1/3 GATA TF binding motifs. We further show functional deficiencies of the mxl-2 loss in DR outside of lifespan, as eat-2;mxl-2 animals exhibit substantially smaller brood sizes and lay a proportion of dead eggs, indicating that MML-1::MXL-2 has a role in maintaining the balance between resource allocation to the soma and to reproduction under conditions of chronic food scarcity. While eat-2 animals do not show a significantly different metabolic rate compared to wild-type, we also find that loss of mxl-2 in DR does not affect the rate of oxygen consumption in young animals. The gene expression signature of eat-2 mutant animals is consistent with optimization of energy utilization and resource allocation, rather than induction of canonical gene expression changes associated with acute metabolic stress, such as induction of autophagy after TORC1 inhibition. Consistently, eat-2 animals are not substantially resistant to stress, providing further support to the idea that chronic DR may benefit healthspan and lifespan through efficient use of limited resources rather than broad upregulation of stress responses, and also indicates that MML-1::MXL-2 and PHA-4 may have distinct roles in promotion of benefits in response to different pro-longevity stimuli.

NuRD chromatin remodeling is required to repair exogenous DSBs in the Caenorhabditis elegans germline

Organisms rely on coordinated networks of DNA repair pathways to protect genomes against toxic double-strand breaks (DSBs), particularly in germ cells. All repair mechanisms must successfully negotiate the local chromatin environment in order to access DNA. For example, nucleosomes can be repositioned by the highly conserved Nucleosome Remodeling and Deacetylase (NuRD) complex. In Caenorhabditis elegans, NuRD functions in the germline to repair DSBs - the loss of NuRD's ATPase subunit, LET-418/CHD4, prevents DSB resolution and therefore reduces fertility. In this study, we challenge germlines with exogenous DNA damage to better understand NuRD's role in repairing DSBs. We find that let-418 mutants are hypersensitive to cisplatin and hydroxyurea: exposure to either mutagen impedes DSB repair, generates aneuploid oocytes, and severely reduces fertility and embryonic survival. These defects resemble those seen when the Fanconi anemia (FA) DNA repair pathway is compromised, and we find that LET-418's activity is epistatic to that of the FA component FCD-2/FANCD2. We propose a model in which NuRD is recruited to the site of DNA lesions to remodel chromatin and allow access for FA pathway components. Together, these results implicate NuRD in the repair of both endogenous DSBs and exogenous DNA lesions to preserve genome integrity in developing germ cells.

Transcriptional drift in aging cells: A global decontroller

As cells age, they undergo a remarkable global change: In transcriptional drift, hundreds of genes become overexpressed while hundreds of others become underexpressed. Using archetype modeling and Gene Ontology analysis on data from aging Caenorhabditis elegans worms, we find that the up-regulated genes code for sensory proteins upstream of stress responses and down-regulated genes are growth- and metabolism-related. We observe similar trends within human fibroblasts, suggesting that this process is conserved in higher organisms. We propose a simple mechanistic model for how such global coordination of multiprotein expression levels may be achieved by the binding of a single factor that concentrates with age in C. elegans. A key implication is that a cell's own responses are part of its aging process, so unlike wear-and-tear processes, intervention might be able to modulate these effects.

Proteasome hyperactivation rewires the proteome enhancing stress resistance, proteostasis, lipid metabolism and ERAD in C. elegans

Proteasome dysfunction is implicated in the pathogenesis of neurodegenerative diseases and age-related proteinopathies. Using a C. elegans model, we demonstrate that 20S proteasome hyperactivation, facilitated by 20S gate-opening, accelerates the targeting of intrinsically disordered proteins. This leads to increased protein synthesis, extensive rewiring of the proteome and transcriptome, enhanced oxidative stress defense, accelerated lipid metabolism, and peroxisome proliferation. It also promotes ER-associated degradation (ERAD) of aggregation-prone proteins, such as alpha-1 antitrypsin (ATZ) and various lipoproteins. Notably, our results reveal that 20S proteasome hyperactivation suggests a novel role in ERAD with broad implications for proteostasis-related disorders, simultaneously affecting lipid homeostasis and peroxisome proliferation. Furthermore, the enhanced cellular capacity to mitigate proteostasis challenges, alongside unanticipated acceleration of lipid metabolism is expected to contribute to the longevity phenotype of this mutant. Remarkably, the mechanism of longevity induced by 20S gate opening appears unique, independent of known longevity and stress-resistance pathways. These results support the therapeutic potential of 20S proteasome activation in mitigating proteostasis-related disorders broadly and provide new insights into the complex interplay between proteasome activity, cellular health, and aging.

BMP signaling to pharyngeal muscle in the C. elegans response to a bacterial pathogen regulates anti-microbial peptide expression and pharyngeal pumping

Host response to pathogens recruits multiple tissues in part through conserved cell signaling pathways. In Caenorhabditis elegans, the bone morphogenetic protein (BMP) like DBL-1 signaling pathway has a role in the response to infection in addition to other roles in development and postdevelopmental functions. In the regulation of body size, the DBL-1 pathway acts through cell autonomous signal activation in the epidermis (hypodermis). We have now elucidated the tissues that respond to DBL-1 signaling upon exposure to two bacterial pathogens. The receptors and Smad signal transducers for DBL-1 are expressed in pharyngeal muscle, intestine, and epidermis. We demonstrate that expression of receptor-regulated Smad (R-Smad) gene sma-3 in the pharynx is sufficient to improve the impaired survival phenotype of sma-3 mutants and that expression of sma-3 in the intestine has no effect when exposing worms to bacterial infection of the intestine. We also show that two antimicrobial peptide genes - abf-2 and cnc-2 - are regulated by DBL-1 signaling through R-Smad SMA-3 activity in the pharynx. Finally, we show that pharyngeal pumping activity is reduced in sma-3 mutants and that other pharynx-defective mutants also have reduced survival on a bacterial pathogen. Our results identify the pharynx as a tissue that responds to BMP signaling to coordinate a systemic response to bacterial pathogens.

An organismal understanding of C. elegans innate immune responses, from pathogen recognition to multigenerational resistance

The nematode Caenorhabditis elegans has been a model for studying infection since the early 2000s and many major discoveries have been made regarding its innate immune responses. C. elegans has been found to utilize some key conserved aspects of immune responses and signaling, but new interesting features of innate immunity have also been discovered in the organism that might have broader implications in higher eukaryotes such as mammals. Some of the distinctive features of C. elegans innate immunity involve the mechanisms this bacterivore uses to detect infection and mount specific immune responses to different pathogens, despite lacking putative orthologs of many important innate immune components, including cellular immunity, the inflammasome, complement, or melanization. Even when orthologs of known immune factors exist, there appears to be an absence of canonical functions, most notably the lack of pattern recognition by its sole Toll-like receptor. Instead, recent research suggests that C. elegans senses infection by specific pathogens through contextual information, including unique products produced by the pathogen or infection-induced disruption of host physiology, similar to the proposed detection of patterns of pathogenesis in mammalian systems. Interestingly, C. elegans can also transfer information of past infection to their progeny, providing robust protection for their offspring in face of persisting pathogens, in part through the RNAi pathway as well as potential new mechanisms that remain to be elucidated. Altogether, some of these strategies employed by C. elegans share key conceptual features with vertebrate adaptive immunity, as the animal can differentiate specific microbial features, as well as propagate a form of immune memory to their offspring.

BMP signaling to pharyngeal muscle in the C. elegans response to a bacterial pathogen regulates anti-microbial peptide expression and pharyngeal pumping

Host response to pathogens recruits multiple tissues in part through conserved cell signaling pathways. In C. elegans, the bone morphogenetic protein (BMP) like DBL-1 signaling pathway has a role in the response to infection in addition to other roles in development and post-developmental functions. In the regulation of body size, the DBL-1 pathway acts through cell autonomous signal activation in the epidermis (hypodermis). We have now elucidated the tissues that respond to DBL-1 signaling upon exposure to two bacterial pathogens. The receptors and Smad signal transducers for DBL-1 are expressed in pharyngeal muscle, intestine, and epidermis. We demonstrate that expression of receptor-regulated Smad (R-Smad) gene sma-3 in the pharynx is sufficient to improve the impaired survival phenotype of sma-3 mutants and that expression of sma-3 in the intestine has no effect when exposing worms to bacterial infection of the intestine. We also show that two antimicrobial peptide genes - abf-2 and cnc-2 - are regulated by DBL-1 signaling through R-Smad SMA-3 activity in the pharynx. Finally, we show that pharyngeal pumping activity is reduced in sma-3 mutants and that other pharynx-defective mutants also have reduced survival on a bacterial pathogen. Our results identify the pharynx as a tissue that responds to BMP signaling to coordinate a systemic response to bacterial pathogens.

Considering Caenorhabditis elegans Aging on a Temporal and Tissue Scale: The Case of Insulin/IGF-1 Signaling

The aging process is inherently complex, involving multiple mechanisms that interact at different biological scales. The nematode Caenorhabditis elegans is a simple model organism that has played a pivotal role in aging research following the discovery of mutations extending lifespan. Longevity pathways identified in C. elegans were subsequently found to be conserved and regulate lifespan in multiple species. These pathways intersect with fundamental hallmarks of aging that include nutrient sensing, epigenetic alterations, proteostasis loss, and mitochondrial dysfunction. Here we summarize recent data obtained in C. elegans highlighting the importance of studying aging at both the tissue and temporal scale. We then focus on the neuromuscular system to illustrate the kinetics of changes that take place with age. We describe recently developed tools that enabled the dissection of the contribution of the insulin/IGF-1 receptor ortholog DAF-2 to the regulation of worm mobility in specific tissues and at different ages. We also discuss guidelines and potential pitfalls in the use of these new tools. We further highlight the opportunities that they present, especially when combined with recent transcriptomic data, to address and resolve the inherent complexity of aging. Understanding how different aging processes interact within and between tissues at different life stages could ultimately suggest potential intervention points for age-related diseases.

Aging disrupts spatiotemporal regulation of germline stem cells and niche integrity

A major factor driving stem cell decline is stem cell niche aging, but its molecular mechanism remains elusive. We use the Caenorhabditis elegans distal tip cell (DTC), the mesenchymal niche that employs Notch signaling to regulate germline stem cells (GSCs), as an in vivo niche aging model and delineate the molecular details of the DTC/niche aging process. Here, we demonstrate that a drastic decrease in C. elegans germline fecundity, which begins even in early adulthood, is mainly due to an age-induced disruption in spatial regulation of Notch-dependent transcription in the germline combined with a moderate reduction in Notch transcription at both tissue and cellular levels. Consequently, the Notch-responsive GSC pool shifts from the distal end of the gonad to a more proximal region, disrupting the distal-to-proximal germline polarity. We find that this GSC pool shift is due to a dislocation of the DTC/niche nucleus, which is associated with age-induced changes in the structure and morphology of the DTC/niche. Our findings reveal a critical link between physiological changes in the aging niche, their consequences in stem cell regulation, and germline tissue functions.

Icariin Improves Stress Resistance and Extends Lifespan in Caenorhabditis elegans through hsf-1 and daf-2-Driven Hormesis

Aging presents an increasingly significant challenge globally, driven by the growing proportion of individuals aged 60 and older. Currently, there is substantial research interest in pro-longevity interventions that target pivotal signaling pathways, aiming not only to extend lifespan but also to enhance healthspan. One particularly promising approach involves inducing a hormetic response through the utilization of natural compounds defined as hormetins. Various studies have introduced the flavonoid icariin as beneficial for age-related diseases such as cardiovascular and neurodegenerative conditions. To validate its potential pro-longevity properties, we employed Caenorhabditis elegans as an experimental platform. The accumulated results suggest that icariin extends the lifespan of C. elegans through modulation of the DAF-2, corresponding to the insulin/IGF-1 signaling pathway in humans. Additionally, we identified increased resistance to heat and oxidative stress, modulation of lipid metabolism, improved late-life healthspan, and an extended lifespan upon icariin treatment. Consequently, a model mechanism of action was provided for icariin that involves the modulation of various players within the stress-response network. Collectively, the obtained data reveal that icariin is a potential hormetic agent with geroprotective properties that merits future developments.

Mitochondrial GTP metabolism controls reproductive aging in C. elegans

Healthy mitochondria are critical for reproduction. During aging, both reproductive fitness and mitochondrial homeostasis decline. Mitochondrial metabolism and dynamics are key factors in supporting mitochondrial homeostasis. However, how they are coupled to control reproductive health remains unclear. We report that mitochondrial GTP (mtGTP) metabolism acts through mitochondrial dynamics factors to regulate reproductive aging. We discovered that germline-only inactivation of GTP- but not ATP-specific succinyl-CoA synthetase (SCS) promotes reproductive longevity in Caenorhabditis elegans. We further identified an age-associated increase in mitochondrial clustering surrounding oocyte nuclei, which is attenuated by GTP-specific SCS inactivation. Germline-only induction of mitochondrial fission factors sufficiently promotes mitochondrial dispersion and reproductive longevity. Moreover, we discovered that bacterial inputs affect mtGTP levels and dynamics factors to modulate reproductive aging. These results demonstrate the significance of mtGTP metabolism in regulating oocyte mitochondrial homeostasis and reproductive longevity and identify mitochondrial fission induction as an effective strategy to improve reproductive health.

Cadmium-induced reproductive toxicity combined with a correlation to the oogenesis process and competing endogenous RNA networks based on a Caenorhabditis elegans model

Accumulation of the heavy metal Cadmium (Cd) in the ovaries and placenta can affect the structure and function of these organs and induce female reproductive toxicity. This toxicity may be due to Cd's similarity to estrogen and its ability to disrupt endocrine systems. However, the exact molecular mechanism by which Cd causes reproductive toxicity at the transcriptome level remains poorly understood. Hence, this study aimed to observe Cd-induced reproductive damage at the gene level, scrutinize the repercussions of Cd exposure on oogenesis, and explicate the putative pathogenesis of Cd-induced oogenesis based on Caenorhabditis elegans (C. elegans) as an in vivo model. The results showed that Cd exposure significantly decreased the number of offspring and prolonged the reproductive span of C. elegans. Cd exposure also reduced the number of cells in mitosis and the pachytene and diakinesis stages of meiosis, thereby disrupting oogenesis. Combined with transcriptional sequencing and bioinformatics analysis, a total of 3167 DEmRNAs were identified. Regarding gene expression, cul-6, mum-2, and vang-1 were found to be related to Cd-induced reproductive toxicity, and their competing endogenous RNA networks were constructed. We observed that mutations of mom-2 and vang-1 in the Wnt pathway could induce susceptibility to Cd-caused meiosis injury. In conclusion, the results indicated that Cd could impair the oogenesis of C. elegans and the Wnt pathway might serve as a protective mechanism against Cd reproductive toxicity. These findings contribute to a better understanding of the damaging effects and molecular biological mechanisms of Cd on the human reproductive system.

The C. elegans Myc-family of transcription factors coordinate a dynamic adaptive response to dietary restriction

Dietary restriction (DR), the process of decreasing overall food consumption over an extended period of time, has been shown to increase longevity across evolutionarily diverse species and delay the onset of age-associated diseases in humans. In Caenorhabditis elegans, the Myc-family transcription factors (TFs) MXL-2 (Mlx) and MML-1 (MondoA/ChREBP), which function as obligate heterodimers, and PHA-4 (orthologous to forkhead box transcription factor A) are both necessary for the full physiological benefits of DR. However, the adaptive transcriptional response to DR and the role of MML-1::MXL-2 and PHA-4 remains elusive. We identified the transcriptional signature of C. elegans DR, using the eat-2 genetic model, and demonstrate broad changes in metabolic gene expression in eat-2 DR animals, which requires both mxl-2 and pha-4. While the requirement for these factors in DR gene expression overlaps, we found many of the DR genes exhibit an opposing change in relative gene expression in eat-2;mxl-2 animals compared to wild-type, which was not observed in eat-2 animals with pha-4 loss. We further show functional deficiencies of the mxl-2 loss in DR outside of lifespan, as eat-2;mxl-2 animals exhibit substantially smaller brood sizes and lay a proportion of dead eggs, indicating that MML-1::MXL-2 has a role in maintaining the balance between resource allocation to the soma and to reproduction under conditions of chronic food scarcity. While eat-2 animals do not show a significantly different metabolic rate compared to wild-type, we also find that loss of mxl-2 in DR does not affect the rate of oxygen consumption in young animals. The gene expression signature of eat-2 mutant animals is consistent with optimization of energy utilization and resource allocation, rather than induction of canonical gene expression changes associated with acute metabolic stress -such as induction of autophagy after TORC1 inhibition. Consistently, eat-2 animals are not substantially resistant to stress, providing further support to the idea that chronic DR may benefit healthspan and lifespan through efficient use of limited resources rather than broad upregulation of stress responses, and also indicates that MML-1::MXL-2 and PHA-4 may have different roles in promotion of benefits in response to different pro-longevity stimuli.

Regulation of defective mitochondrial DNA accumulation and transmission in C. elegans by the programmed cell death and aging pathways

The heteroplasmic state of eukaryotic cells allows for cryptic accumulation of defective mitochondrial genomes (mtDNA). 'Purifying selection' mechanisms operate to remove such dysfunctional mtDNAs. We found that activators of programmed cell death (PCD), including the CED-3 and CSP-1 caspases, the BH3-only protein CED-13, and PCD corpse engulfment factors, are required in C. elegans to attenuate germline abundance of a 3.1-kb mtDNA deletion mutation, uaDf5, which is normally stably maintained in heteroplasmy with wildtype mtDNA. In contrast, removal of CED-4/Apaf1 or a mutation in the CED-4-interacting prodomain of CED-3, do not increase accumulation of the defective mtDNA, suggesting induction of a non-canonical germline PCD mechanism or non-apoptotic action of the CED-13/caspase axis. We also found that the abundance of germline mtDNAuaDf5 reproducibly increases with age of the mothers. This effect is transmitted to the offspring of mothers, with only partial intergenerational removal of the defective mtDNA. In mutants with elevated mtDNAuaDf5 levels, this removal is enhanced in older mothers, suggesting an age-dependent mechanism of mtDNA quality control. Indeed, we found that both steady-state and age-dependent accumulation rates of uaDf5 are markedly decreased in long-lived, and increased in short-lived, mutants. These findings reveal that regulators of both PCD and the aging program are required for germline mtDNA quality control and its intergenerational transmission.

Microbes are potential key players in the evolution of life histories and aging in Caenorhabditis elegans

Microbes can have profound effects on host fitness and health and the appearance of late-onset diseases. Host-microbe interactions thus represent a major environmental context for healthy aging of the host and might also mediate trade-offs between life-history traits in the evolution of host senescence. Here, we have used the nematode Caenorhabditis elegans to study how host-microbe interactions may modulate the evolution of life histories and aging. We first characterized the effects of two non-pathogenic and one pathogenic Escherichia coli strains, together with the pathogenic Serratia marcescens DB11 strain, on population growth rates and survival of C. elegans from five different genetic backgrounds. We then focused on an outbred C. elegans population, to understand if microbe-specific effects on the reproductive schedule and in traits such as developmental rate and survival were also expressed in the presence of males and standing genetic variation, which could be relevant for the evolution of C. elegans and other nematode species in nature. Our results show that host-microbe interactions have a substantial host-genotype-dependent impact on the reproductive aging and survival of the nematode host. Although both pathogenic bacteria reduced host survival in comparison with benign strains, they differed in how they affected other host traits. Host fertility and population growth rate were affected by S. marcescens DB11 only during early adulthood, whereas this occurred at later ages with the pathogenic E. coli IAI1. In both cases, these effects were largely dependent on the host genotypes. Given such microbe-specific genotypic differences in host life history, we predict that the evolution of reproductive schedules and senescence might be critically contingent on host-microbe interactions in nature.

Ovarian aging in humans: potential strategies for extending reproductive lifespan

Ovarian reserve is a term used to estimate the total number of immature follicles present in the ovaries. Between birth and menopause, there is a progressive decrease in the number of ovarian follicles. Ovarian aging is a continuous physiological phenomenon, with menopause being the clinical mark of the end of ovarian function. Genetics, measured as family history for age at the onset of menopause, is the main determinant. However, physical activity, diet, and lifestyle are important factors that can influence the age of menopause. The low estrogen levels after natural or premature menopause increased the risk for several diseases, resulting in increased mortality risk. Besides that, the decreasing ovarian reserve is associated to reduced fertility. In women with infertility undergoing in vitro fertilization, reduced markers of ovarian reserve, including antral follicular count and anti-Mullerian hormone, are the main indicators of reduced chances of becoming pregnant. Therefore, it becomes clear that the ovarian reserve has a central role in women's life, affecting fertility early in life and overall health later in life. Based on this, the ideal strategy for delaying ovarian aging should have the following characteristics: (1) be initiated in the presence of good ovarian reserve; (2) maintained for a long period; (3) have an action on the dynamics of primordial follicles, controlling the rate of activation and atresia; and (4) safe use in pre-conception, pregnancy, and lactation. In this review, we therefore discuss some of these strategies and its feasibility for preventing a decline in the ovarian reserve.

Structured Docosahexaenoic Acid (DHA) Enhances Motility and Promotes the Antioxidant Capacity of Aged C. elegans

The human lifespan has increased over the past century; however, healthspans have not kept up with this trend, especially cognitive health. Among nutrients for brain function maintenance, long-chain omega-3 polyunsaturated fatty acids (ω-3 LCPUFA): DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) must be highlighted, particularly structured forms of EPA and DHA which were developed to improve bioavailability and bioactivity in comparison with conventional ω-3 supplements. This study aims to elucidate the effect of a structured triglyceride form of DHA (DHA-TG) on the healthspan of aged C. elegans. Using a thrashing assay, the nematodes were monitored at 4, 8, and 12 days of adulthood, and DHA-TG improved its motility at every age without affecting lifespan. In addition, the treatment promoted antioxidant capacity by enhancing the activity and expression of SOD (superoxide dismutase) in the nematodes. Lastly, as the effect of DHA-TG was lost in the DAF-16 mutant strain, it might be hypothesized that the effects of DHA need DAF-16/FOXO as an intermediary. In brief, DHA-TG exerted a healthspan-promoting effect resulting in both enhanced physical fitness and increased antioxidant defense in aged C. elegans. For the first time, an improvement in locomotive function in aged wild-type nematodes is described following DHA-TG treatment.

C. elegans ageing is accelerated by a self-destructive reproductive programme

In post-reproductive C. elegans, destructive somatic biomass repurposing supports production of yolk which, it was recently shown, is vented and can serve as a foodstuff for larval progeny. This is reminiscent of the suicidal reproductive effort (reproductive death) typical of semelparous organisms such as Pacific salmon. To explore the possibility that C. elegans exhibits reproductive death, we have compared sibling species pairs of the genera Caenorhabditis and Pristionchus with hermaphrodites and females. We report that yolk venting and constitutive, early pathology involving major anatomical changes occur only in hermaphrodites, which are also shorter lived. Moreover, only in hermaphrodites does germline removal suppress senescent pathology and markedly increase lifespan. This is consistent with the hypothesis that C. elegans exhibit reproductive death that is suppressed by germline ablation. If correct, this would imply a major difference in the ageing process between C. elegans and most higher organisms, and potentially explain the exceptional plasticity in C. elegans ageing.

Toward Gene-Correlated Spatially Resolved Metabolomics with Fingerprint Coherent Raman Imaging

Raman spectroscopy has long been known to provide sufficient information to discriminate distinct cell phenotypes. Underlying this discriminating capability is that Raman spectra provide an overall readout of the metabolic profiles that change with transcriptomic activity. Robustly associating Raman spectral changes with the regulation of specific signaling pathways may be possible, but the spectral signals of interest may be weak and vary somewhat among individuals. Establishing a Raman-to-transcriptome mapping will thus require tightly controlled and easily manipulated biological systems and high-throughput spectral acquisition. We attempt to meet these requirements using broadband coherent anti-Stokes Raman scattering (BCARS) microscopy to spatio-spectrally map the C. elegans hermaphrodite gonad in vivo at subcellular resolution. The C. elegans hermaphrodite gonad is an ideal model system with a sequential, continuous process of highly regulated spatiotemporal cellular events. We demonstrate that the BCARS spatio-spectral signatures correlate with gene expression profiles in the gonad, evincing that BCARS has potential as a spatially resolved omics surrogate.

Chlorogenic Acid of Cirsium japonicum Resists Oxidative Stress Caused by Aging and Prolongs Healthspan via SKN-1/Nrf2 and DAF-16/FOXO in Caenorhabditis elegans

To evaluate the value of Cirsium japonicum (CJ; thistle) as a material for functional foods, we studied the functional composition of cultivated CJ and the in vitro and in vivo antioxidant activity of the functional substance. The detected phenolics in farmed CJ were chlorogenic acid (CA), linarin (LIN), and pectolinarin (PLIN) by HPLC analysis. As a result of the antioxidant activity of CJ and its phenolics by DPPH and ABTS method, CA had shown the greatest antioxidant activity. We employed Caenorhabditis elegans to validate that in vitro effects of CA are shown in vivo. CA delayed reduction in pumping rate and progeny production during aging of C. elegans. Under both normal and oxidative stress conditions, CA reduced the production of reactive oxygen species (ROS) in worms and increased their lifespan. In particular, CA showed the reducing effect of ROS accumulation due to aging in aged worms (8 days old). To gain insight into the mechanism, we used skn-1/Nrf2 and daf-16/FOXO transformed worms. The CA effects (on catalase activity and lifespan extension) in the wild-type (WT) decreased in skn-1 and daf-16 mutants. In particular, CA strongly relied on daf-16 under mild oxidative condition and skn-1 under overall (from mild to strong) oxidative stress to reduce ROS and extend healthspan. Thus, we conclude that CA, a key bioactive phenolic of CJ, reduces ROS production and ultimately extends healthspan, and this effect is the result of actions of daf-16 or skn-1 at different stages depending on the degree of oxidation or aging. Our results suggest that CJ containing CA can be used as an antiaging material due to its antioxidant properties.

Targeting the "hallmarks of aging" to slow aging and treat age-related disease: fact or fiction?

Aging is a major risk factor for a number of chronic diseases, including neurodegenerative and cerebrovascular disorders. Aging processes have therefore been discussed as potential targets for the development of novel and broadly effective preventatives or therapeutics for age-related diseases, including those affecting the brain. Mechanisms thought to contribute to aging have been summarized under the term the "hallmarks of aging" and include a loss of proteostasis, mitochondrial dysfunction, altered nutrient sensing, telomere attrition, genomic instability, cellular senescence, stem cell exhaustion, epigenetic alterations and altered intercellular communication. We here examine key claims about the "hallmarks of aging". Our analysis reveals important weaknesses that preclude strong and definitive conclusions concerning a possible role of these processes in shaping organismal aging rate. Significant ambiguity arises from the overreliance on lifespan as a proxy marker for aging, the use of models with unclear relevance for organismal aging, and the use of study designs that do not allow to properly estimate intervention effects on aging rate. We also discuss future research directions that should be taken to clarify if and to what extent putative aging regulators do in fact interact with aging. These include multidimensional analytical frameworks as well as designs that facilitate the proper assessment of intervention effects on aging rate.

Maternal Gliadin Intake Reduces Oocyte Quality with Chromosomal Aberrations and Increases Embryonic Lethality through Oxidative Stress in a Caenorhabditis elegans Model

Oocyte quality is essential for reproductive capacity, but it rapidly declines with age. In addition to aging, maternal nutrition is a major concern in maintaining oocyte quality. Gliadin, a major component of gluten, causes gluten toxicity, which has been reported in a variety of gluten-related disorders. The basis of gluten toxicity in reproduction is being understood using simple animal models such as Caenorhabditis elegans. In this study, we examined the effects of gliadin peptide (GP; amino acids 151-170) intake on oocyte quality control in C. elegans. We found that GP intake impaired oocyte quality through chromosomal aberrations and mitochondrial oxidative stress, which was suppressed by antioxidant treatment. The reduced oocyte quality by GP intake consequently increased embryonic lethality. Furthermore, the expression of oxidative stress-responding genes prdx-3 and gst-4 was significantly increased by GP intake. The increased DAF-16 activity by GP intake suggests that DAF-16 is a possible transactivator of these antioxidant genes. Taken together, GP intake reduced reproductive capacity in C. elegans by decreasing oocyte quality and increasing embryonic lethality through mitochondrial oxidative stress.

Multigenerational downregulation of insulin/IGF-1 signaling in adulthood improves lineage survival, reproduction, and fitness in Caenorhabditis elegans supporting the developmental theory of ageing

Adulthood-only downregulation of insulin/IGF-1 signaling (IIS), an evolutionarily conserved pathway regulating resource allocation between somatic maintenance and reproduction, increases life span without fecundity cost in the nematode, Caenorhabditis elegans. However, long-term multigenerational effects of reduced IIS remain unexplored and are proposed to carry costs for offspring quality. To test this hypothesis, we ran a mutation accumulation (MA) experiment and downregulated IIS in half of the 400 MA lines by silencing daf-2 gene expression using RNA interference (RNAi) across 40 generations. Contrary to the prediction, adulthood-only daf-2 RNAi reduced extinction of MA lines both under UV-induced and spontaneous MA. Fitness of the surviving UV-induced MA lines was higher under daf-2 RNAi. Reduced IIS increased intergenerational F1 offspring fitness under UV stress but had no quantifiable transgenerational effects. Functional hrde-1 was required for the benefits of multigenerational daf-2 RNAi. Overall, we found net benefit to fitness from multigenerational reduction of IIS and the benefits became more apparent under stress. Because reduced daf-2 expression during development carries fitness costs, we suggest that our findings are best explained by the developmental theory of ageing, which maintains that the decline in the force of selection with age results in poorly regulated gene expression in adulthood.

Pollutants corrupt resilience pathways of aging in the nematode C. elegans

Delaying aging while prolonging health and lifespan is a major goal in aging research. One promising strategy is to focus on reducing negative interventions such as pollution and their accelerating effect on age-related degeneration and disease. Here, we used the short-lived model organism C. elegans to analyze whether two candidate pollutants corrupt general aging pathways. We show that the emergent pollutant silica nanoparticles (NPs) and the classic xenobiotic inorganic mercury reduce lifespan and cause a premature protein aggregation phenotype. Comparative mass spectrometry revealed that increased insolubility of proteins with important functions in proteostasis is a shared phenotype of intrinsic- and pollution-induced aging supporting the hypothesis that proteostasis is a central resilience pathway controlling lifespan and aging. The presented data demonstrate that pollutants corrupt intrinsic aging pathways. Reducing pollution is, therefore, an important step to increasing healthy aging and prolonging life expectancies on a population level in humans and animals.

Methylmercury exposure-induced reproductive effects are mediated by dopamine in Caenorhabditis elegans

Methylmercury (MeHg) is a neurotoxicant that exists in the natural environment, which level can be greatly increased because of human activity. MeHg exposures have the risk of being detrimental to the development of the nervous system. Studies on MeHg toxicity have largely focused on the mechanisms of its neurotoxicity following developmental exposures. Additionally, reproductive toxicity of developmental MeHg exposures has been noted in rodent models. The model organism Caenorhabditis elegans (C. elegans) is a self-fertilizing animal which has a short lifespan around 20 days. Most C. elegans are hermaphrodites that can generate both sperm and oocytes. To investigate the effects of developmental MeHg exposures on the reproduction in C. elegans, larvae stage 1 worms were exposed to MeHg (0, 0.01 or 0.05 μM) for 24 h. The laid eggs and oocytes were compared during each day at adult stages for 6 days. We showed that MeHg exposure significantly induced an increased number of eggs in day 1 adults without an effect on the timing of egg laying or the total number of eggs or oocytes over the 6-day period. The expression of dat-1 and cat-2 and dopamine levels were increased in worms exposed to MeHg. Supplementation with 100 μM dopamine recapitulated the effect of MeHg on the number of eggs present in day 1 adults. Furthermore, the effect of MeHg on the number of eggs was abrogated in the cat-2 mutant worms CB1112. The number of oocytes in the 6-day adult stages was decreased by MeHg in the dat-1 mutant RM2702. MeHg exposures did not change the mating rate or the number of offspring from mating. Combined, these novel findings show that developmental exposure to low levels of MeHg has limited effects on the reproduction in C. elegans. Furthermore, our data support a modulatory role of dopamine in MeHg-induced effects on reproduction in this model system.

3,3'-Diindolylmethane Supplementation Maintains Oocyte Quality by Reducing Oxidative Stress and CEP-1/p53-Mediated Regulation of Germ Cells in a Reproductively Aged Caenorhabditis elegans Model

In recent decades, maternal age at first birth has increased, as has the risk of infertility due to rapidly declining oocyte quality with age. Therefore, an understanding of female reproductive aging and the development of potential modulators to control oocyte quality are required. In this study, we investigated the effects of 3,3'-diindolylmethane (DIM), a natural metabolite of indole-3-cabinol found in cruciferous vegetables, on fertility in a Caenorhabditis elegans model. C. elegans fed DIM showed decreased mitochondrial dysfunction, oxidative stress, and chromosomal aberrations in aged oocytes, and thus reduced embryonic lethality, suggesting that DIM, a dietary natural antioxidant, improves oocyte quality. Furthermore, DIM supplementation maintained germ cell apoptosis (GCA) and germ cell proliferation (GCP) in a CEP-1/p53-dependent manner in a reproductively aged C. elegans germ line. DIM-induced GCA was mediated by the CEP-1-EGL-1 pathway without HUS-1 activation, suggesting that DIM-induced GCA is different from DNA damage-induced GCA in the C. elegans germ line. Taken together, we propose that DIM supplementation delays the onset of reproductive aging by maintaining the levels of GCP and GCA and oocyte quality in a reproductively aged C. elegans.

Reproductive Span of Caenorhabditis elegans Is Extended by Microbacterium sp

The reproductive span (RS) of organisms could be affected by different factors during their lifetime. In the model nematode, Caenorhabditis elegans, RS is affected by both genetic and environmental factors. However, none of the factors identified so far were related to environmental bacteria, which may incidentally appear anywhere in the habitats of C. elegans. We aimed to find environmental bacteria that could affect the RS of C. elegans and related species. We tested 109 bacterial isolates and found that Microbacterium sp. CFBb37 increased the RS and lifespan of C. elegans but reduced its brood size. We studied the effect of M. sp. CFBb37 on the RS of Caenorhabditis briggsae, Caenorhabditis tropicalis, and another Rhabditidae family species, Protorhabditis sp., and found similar trends of RS extension in all three cases, suggesting that this bacterial species may induce the extension of RS broadly among Caenorhabditis species and possibly for many other Rhabditidae. This work will facilitate future research on the mechanism underlying the bacterial extension of RS of nematodes and possibly other animals.

C. elegans as a model organism to study female reproductive health

Female reproductive health has been historically understudied and underfunded. Here, we present the advantages of using a free-living nematode, Caenorhabditis elegans, as an animal system to study fundamental aspects of female reproductive health. C. elegans is a powerful high-throughput model organism that shares key genetic and physiological similarities with humans. In this review, we highlight areas of pressing medical and biological importance in the 21st century within the context of female reproductive health. These include the decline in female reproductive capacity with increasing chronological age, reproductive dysfunction arising from toxic environmental insults, and cancers of the reproductive system. C. elegans has been instrumental in uncovering mechanistic insights underlying these processes, and has been valuable for developing and testing therapeutics to combat them. Adopting a convenient model organism such as C. elegans for studying reproductive health will encourage further research into this field, and broaden opportunities for making advancements into evolutionarily conserved mechanisms that control reproductive function.