Increasing p16INK4a expression decreases forebrain progenitors and neurogenesis during ageing

Restoration of neuronal progenitors by partial reprogramming in the aged neurogenic niche

Partial reprogramming (pulsed expression of reprogramming transcription factors) improves the function of several tissues in old mice. However, it remains largely unknown how partial reprogramming impacts the old brain. Here we use single-cell transcriptomics to systematically examine how partial reprogramming influences the subventricular zone neurogenic niche in aged mouse brains. Whole-body partial reprogramming mainly improves neuroblasts (cells committed to give rise to new neurons) in the old neurogenic niche, restoring neuroblast proportion to more youthful levels. Interestingly, targeting partial reprogramming specifically to the neurogenic niche also boosts the proportion of neuroblasts and their precursors (neural stem cells) in old mice and improves several molecular signatures of aging, suggesting that the beneficial effects of reprogramming are niche intrinsic. In old neural stem cell cultures, partial reprogramming cell autonomously restores the proportion of neuroblasts during differentiation and blunts some age-related transcriptomic changes. Importantly, partial reprogramming improves the production of new neurons in vitro and in old brains. Our work suggests that partial reprogramming could be used to rejuvenate the neurogenic niche and counter brain decline in old individuals.

Underlying Mechanisms and Treatment of Cellular Senescence-Induced Biological Barrier Interruption and Related Diseases

Given its increasing prevalence, aging is of great concern to researchers worldwide. Cellular senescence is a physiological or pathological cellular state caused by aging and a prominent risk factor for the interruption of the integrity and functionality of human biological barriers. Health barriers play an important role in maintaining microenvironmental homeostasis within the body. The senescence of barrier cells leads to barrier dysfunction and age-related diseases. Cellular senescence has been reported to be a key target for the prevention of age-related barrier diseases, including Alzheimer's disease, Parkinson's disease, age-related macular degeneration, diabetic retinopathy, and preeclampsia. Drugs such as metformin, dasatinib, quercetin, BCL-2 inhibitors, and rapamycin have been shown to intervene in cellular senescence and age-related diseases. In this review, we conclude that cellular senescence is involved in age-related biological barrier impairment. We further outline the cellular pathways and mechanisms underlying barrier impairment caused by cellular senescence and describe age-related barrier diseases associated with senescent cells. Finally, we summarize the currently used anti-senescence pharmacological interventions and discuss their therapeutic potential for preventing age-related barrier diseases.

Nucleoporin Seh1 controls murine neocortical development via transcriptional repression of p21 in neural stem cells

Mutations or dysregulation of nucleoporins (Nups) are strongly associated with neural developmental diseases, yet the underlying mechanisms remain poorly understood. Here, we show that depletion of Nup Seh1 in radial glial progenitors results in defective neural progenitor proliferation and differentiation that ultimately manifests in impaired neurogenesis and microcephaly. This loss of stem cell proliferation is not associated with defects in the nucleocytoplasmic transport. Rather, transcriptome analysis showed that ablation of Seh1 in neural stem cells derepresses the expression of p21, and knockdown of p21 partially restored self-renewal capacity. Mechanistically, Seh1 cooperates with the NuRD transcription repressor complex at the nuclear periphery to regulate p21 expression. Together, these findings identified that Nups regulate brain development by exerting a chromatin-associated role and affecting neural stem cell proliferation.

Transcriptional and epigenetic dysregulation impairs generation of proliferative neural stem and progenitor cells during brain aging

The decline in stem cell function during aging may affect the regenerative capacity of mammalian organisms; however, the gene regulatory mechanism underlying this decline remains unclear. Here we show that the aging of neural stem and progenitor cells (NSPCs) in the male mouse brain is characterized by a decrease in the generation efficacy of proliferative NSPCs rather than the changes in lineage specificity of NSPCs. We reveal that the downregulation of age-dependent genes in NSPCs drives cell aging by decreasing the population of actively proliferating NSPCs while increasing the expression of quiescence markers. We found that epigenetic deregulation of the MLL complex at promoters leads to transcriptional inactivation of age-dependent genes, highlighting the importance of the dynamic interaction between histone modifiers and gene regulatory elements in regulating transcriptional program of aging cells. Our study sheds light on the key intrinsic mechanisms driving stem cell aging through epigenetic regulators and identifies potential rejuvenation targets that could restore the function of aging stem cells.

Cellular senescence and frailty: a comprehensive insight into the causal links

Senescent cells may have a prominent role in driving inflammation and frailty. The impact of cellular senescence on frailty varies depending on the assessment tool used, as it is influenced by the criteria or items predominantly affected by senescent cells and the varying weights assigned to these items across different health domains. To address this challenge, we undertook a thorough review of all available studies involving gain- or loss-of-function experiments as well as interventions targeting senescent cells, focusing our attention on those studies that examined outcomes based on the individual frailty phenotype criteria or specific items used to calculate two humans (35 and 70 items) and one mouse (31 items) frailty indexes. Based on the calculation of a simple "evidence score," we found that the burden of senescent cells related to musculoskeletal and cerebral health has the strongest causal link to frailty. We deem that insight into these mechanisms may not only contribute to clarifying the role of cellular senescence in frailty but could additionally provide multiple therapeutic opportunities to help the future development of a desirable personalized therapy in these extremely heterogeneous patients.

CD133+ endothelial-like stem cells restore neovascularization and promote longevity in progeroid and naturally aged mice

The stem cell theory of aging dictates that a decline in the number and/or function of stem cells causes tissue degeneration and aging; however, it still lacks unequivocal experimental support. Here, using lineage tracing and single-cell transcriptomics, we identify a population of CD133+ bone marrow-derived endothelial-like cells (ELCs) as potential endothelial progenitor cells, which contribute to tubular structures in vitro and neovascularization in vivo. We demonstrate that supplementation with wild-type and young ELCs respectively restores neovascularization and extends lifespan in progeric and naturally aged mice. Mechanistically, we identify an upregulation of farnesyl diphosphate synthase (FDPS) in aged CD133+ ELCs-a key enzyme in isoprenoid biosynthesis. Overexpression of FDPS compromises the neovascularization capacity of CD133+ ELCs, whereas FDPS inhibition by pamidronate enhances neovascularization, improves health measures and extends lifespan in aged mice. These findings highlight stem cell-based strategies for the treatment of progeria and age-related pathologies.

Transcriptome analysis reveals genes associated with stem cell activation by physical exercise in the dentate gyrus of aged p16Ink4a knockout mice

Throughout adulthood neural stem cells divide in neurogenic niches-the dentate gyrus of the hippocampus and the subventricular zone-producing progenitor cells and new neurons. Stem cells self-renew, thus preserving their pool. Furthermore, the number of stem/progenitor cells in the neurogenic niches decreases with age. We have previously demonstrated that the cyclin-dependent kinase inhibitor p16Ink4a maintains, in aged mice, the pool of dentate gyrus stem cells by preventing their activation after a neurogenic stimulus such as exercise (running). We showed that, although p16Ink4a ablation by itself does not activate stem/progenitor cells, exercise strongly induced stem cell proliferation in p16Ink4a knockout dentate gyrus, but not in wild-type. As p16Ink4a regulates stem cell self-renewal during aging, we sought to profile the dentate gyrus transcriptome from p16Ink4a wild-type and knockout aged mice, either sedentary or running for 12 days. By pairwise comparisons of differentially expressed genes and by correlative analyses through the DESeq2 software, we identified genes regulated by p16Ink4a deletion, either without stimulus (running) added, or following running. The p16Ink4a knockout basic gene signature, i.e., in sedentary mice, involves upregulation of apoptotic, neuroinflammation- and synaptic activity-associated genes, suggesting a reactive cellular state. Conversely, another set of 106 genes we identified, whose differential expression specifically reflects the pattern of proliferative response of p16 knockout stem cells to running, are involved in processes that regulate stem cell activation, such as synaptic function, neurotransmitter metabolism, stem cell proliferation control, and reactive oxygen species level regulation. Moreover, we analyzed the regulation of these stem cell-specific genes after a second running stimulus. Surprisingly, the second running neither activated stem cell proliferation in the p16Ink4a knockout dentate gyrus nor changed the expression of these genes, confirming that they are correlated to the stem cell reactivity to stimulus, a process where they may play a role regulating stem cell activation.

Oxidative stress associated with spatial memory impairment and social olfactory deterioration in female mice reveals premature aging aroused by perinatal protein malnutrition

Early-life adversity, like perinatal protein malnutrition, increases the vulnerability to develop long-term alterations in brain structures and function. This study aimed to determine whether perinatal protein malnutrition predisposes to premature aging in a murine model and to assess the cellular and molecular mechanisms involved. To this end, mouse dams were fed either with a normal (NP, casein 20%) or a low-protein diet (LP, casein 8%) during gestation and lactation. Female offspring were evaluated at 2, 7 and 12 months of age. Positron emission tomography analysis showed alterations in the hippocampal CA3 region and the accessory olfactory bulb of LP mice during aging. Protein malnutrition impaired spatial memory, coinciding with higher levels of reactive oxygen species in the hippocampus and sirt7 upregulation. Protein malnutrition also led to higher senescence-associated β-galactosidase activity and p21 expression. LP-12-month-old mice showed a higher number of newborn neurons that did not complete the maturation process. The social-odor discrimination in LP mice was impaired along life. In the olfactory bulb of LP mice, the senescence marker p21 was upregulated, coinciding with a downregulation of Sirt2 and Sirt7. Also, LP-12-month-old mice showed a downregulation of catalase and glutathione peroxidase, and LP-2-month-old mice showed a higher number of newborn neurons in the subventricular zone, which then returned to normal values. Our results show that perinatal protein malnutrition causes long-term impairment in cognitive and olfactory skills through an accelerated senescence phenotype accompanied by an increase in oxidative stress and altered sirtuin expression in the hippocampus and olfactory bulb.

p16Ink4a, a marker of cellular senescence, is associated with renal disease in the B6.NZMSle1/Sle2/Sle3 mouse model of lupus

OBJECTIVES

Despite treatment, one-third of patients with lupus nephritis (LN) show a decline in renal function. Prognostic markers of poor outcome as well as novel therapeutic targets are therefore highly sought. We showed that p16INK4a, a marker of cellular senescence, is observed in baseline kidney biopsies from patients with LN, and is associated with renal disease. Here, we set out to assess for whether these findings are recapitulated in the B6.NZMSle1/Sle2/Sle3 (B6.Sle1.2.3) mouse model of spontaneous lupus.

METHODS

We evaluated the occurrence and time of onset of p16Ink4a staining by immunohistochemistry on kidney sections, and tested for its association with multiple renal and systemic disease parameters, fibrosis and CD8+ T cell infiltration, in two cohorts of B6.Sle1.2.3 mice.

RESULTS

The presence of p16Ink4a-positive cells in kidney was significantly associated with increased urine albumin/creatinine ratio, histopathological scores, CD8+ T cell infiltration and fibrosis, in both B6.Sle1.2.3 cohorts. In contrast, p16Ink4a staining was not associated with systemic disease parameters. A time course showed that systemic disease parameters as well as glomerular IgG deposits appeared in B6.Sle1.2.3 mice by 4 months of age; the appearance of p16Ink4a-positive cells occurred later, by 8 months of age, overlapping with renal disease.

CONCLUSION

We report, for the first time, the presence of p16Ink4a-positive cells, a marker of cellular senescence, in the B6.Sle1.2.3 kidney, and their association with renal disease severity. This provides a preclinical model in which to test for the role of cellular senescence in the pathogenesis of LN, as a potential kidney-intrinsic disease mechanism.

A 4D transcriptomic map for the evolution of multiple sclerosis-like lesions in the marmoset brain

Single-time-point histopathological studies on postmortem multiple sclerosis (MS) tissue fail to capture lesion evolution dynamics, posing challenges for therapy development targeting development and repair of focal inflammatory demyelination. To close this gap, we studied experimental autoimmune encephalitis (EAE) in the common marmoset, the most faithful animal model of these processes. Using MRI-informed RNA profiling, we analyzed ~600,000 single-nucleus and ~55,000 spatial transcriptomes, comparing them against EAE inoculation status, longitudinal radiological signals, and histopathological features. We categorized 5 groups of microenvironments pertinent to neural function, immune and glial responses, tissue destruction and repair, and regulatory network at brain borders. Exploring perilesional microenvironment diversity, we uncovered central roles of EAE-associated astrocytes, oligodendrocyte precursor cells, and ependyma in lesion formation and resolution. We pinpointed imaging and molecular features capturing the pathological trajectory of WM, offering potential for assessing treatment outcomes using marmoset as a platform.

From Youthful Vigor to Aging Decline: Unravelling the Intrinsic and Extrinsic Determinants of Hippocampal Neural Stem Cell Aging

Since Joseph Altman published his pioneering work demonstrating neurogenesis in the hippocampus of adult rats, the number of publications in this field increased exponentially. Today, we know that the adult hippocampus harbors a pool of adult neural stem cells (NSCs) that are the source of life-long neurogenesis and plasticity. The functions of these NSCs are regulated by extrinsic cues arising from neighboring cells and the systemic environment. However, this tight regulation is subject to imbalance with age, resulting in a decline in adult NSCs and neurogenesis, which contributes to the progressive deterioration of hippocampus-related cognitive functions. Despite extensive investigation, the mechanisms underlying this age-related decline in neurogenesis are only incompletely understood, but appear to include an increase in NSC quiescence, changes in differentiation patterns, and NSC exhaustion. In this review, we summarize recent work that has improved our knowledge of hippocampal NSC aging, focusing on NSC-intrinsic mechanisms as well as cellular and molecular changes in the niche and systemic environment that might be involved in the age-related decline in NSC functions. Additionally, we identify future directions that may advance our understanding of NSC aging and the concomitant loss of hippocampal neurogenesis and plasticity.

Electroconvulsive Therapy Reduces Protein Expression Level of EP300 and Improves Psychiatric Symptoms and Disturbance of Thought in Patients with Schizophrenia

Objective

Although electroconvulsive therapy (ECT) has been employed as an effective treatment strategy and to improve mental symptoms in schizophrenia (SCZ), its action mechanisms remain unclear. Our previous study found that some genes and biological pathways were closely related to ECT through genetic technology analysis, such as LTP pathway and EP300. This study combined with healthy controls and symptomatology analysis to further explore the changes of expression of EP300 protein in treatment and related symptoms of SCZ.

Methods

One hundred and one patients with SCZ and 45 healthy controls (HCs) were enrolled in this study. Patients with SCZ received acute courses of 6 times bilateral ECT. The peripheral blood of patients with SCZ (BECT: before ECT; AECT: after ECT) and the HCs was collected to calculate the changes of expression level of EP300 protein by enzyme-linked immunosorbent assay. The Positive and Negative Symptoms Scale (PANSS) was used to evaluate the severity of symptoms of SCZ patients and the efficiency of the ECT.

Results

There was a statistical difference of EP300 protein expression in patients with SCZ (BECT and AECT) (F = 114.5, p < 0.05). ECT reduced plasma expression level of EP300 protein in patients with SCZ, which was not statistically different from that in HCs (t = 4.47, p = 0.20). The change of the expression level of EP300 protein in patients with SCZ (BECT and AECT) has a positive correlation with reduction rate of positive symptoms (r = 0.228, p < 0.05) and disturbance of thought (r = 0.219, p < 0.05).

Conclusion

Our study suggests that the expression level of EP300 protein has a significant change in patients with SCZ treating with ECT, and EP300 may have some connections with positive symptoms and disturbance thought of patients with SCZ.

Cellular senescence and neurodegeneration

Advancing age is a major risk factor of Alzheimer's disease (AD). The worldwide prevalence of AD is approximately 50 million people, and this number is projected to increase substantially. The molecular mechanisms underlying the aging-associated susceptibility to cognitive impairment in AD are largely unknown. As a hallmark of aging, cellular senescence is a significant contributor to aging and age-related diseases including AD. Senescent neurons and glial cells have been detected to accumulate in the brains of AD patients and mouse models. Importantly, selective elimination of senescent cells ameliorates amyloid beta and tau pathologies and improves cognition in AD mouse models, indicating a critical role of cellular senescence in AD pathogenesis. Nonetheless, the mechanisms underlying when and how cellular senescence contributes to AD pathogenesis remain unclear. This review provides an overview of cellular senescence and discusses recent advances in the understanding of the impact of cellular senescence on AD pathogenesis, with brief discussions of the possible role of cellular senescence in other neurodegenerative diseases including Down syndrome, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis.

Fine-tuned rest: unveiling the regulatory landscape of adult quiescent neural stem cells

Cell quiescence is an essential mechanism that allows cells to temporarily halt proliferation while preserving the potential to resume it at a later time. The molecular mechanisms underlying cell quiescence are complex and involve the regulation of various signaling pathways, transcription factors and epigenetic modifications. The importance of unveiling the mechanisms regulating the quiescent state is undeniable, as its long-term maintenance is key to sustain tissue homeostasis throughout life. Neural stem cells (NSCs) are maintained in the subependymal zone (SEZ) niche of adult mammalian brains mostly as long-lasting quiescent cells, owing to multiple intrinsic and extrinsic cues that actively regulate this state. Differently from other non-proliferative states, quiescence is a reversible and tightly regulated condition that can re-activate to support the formation of new neurons throughout adult lifespan. Decoding its regulatory mechanisms in homeostasis and unveiling how it is modulated in the context of the aged brain or during tumorigenesis, could bring us closer to the development of new potential strategies to intervene in adult neurogenesis with therapeutic purposes. Starting with a general conceptualization of the quiescent state in different stem cell niches, we here review what we have learned about NSC quiescence in the SEZ, encompassing the experimental strategies used for its study, to end up discussing the modulation of quiescence in the context of a physiology or pathological NSC dysregulation.

Chromatin accessibility dynamics of neurogenic niche cells reveal defects in neural stem cell adhesion and migration during aging

The regenerative potential of brain stem cell niches deteriorates during aging. Yet the mechanisms underlying this decline are largely unknown. Here we characterize genome-wide chromatin accessibility of neurogenic niche cells in vivo during aging. Interestingly, chromatin accessibility at adhesion and migration genes decreases with age in quiescent neural stem cells (NSCs) but increases with age in activated (proliferative) NSCs. Quiescent and activated NSCs exhibit opposing adhesion behaviors during aging: quiescent NSCs become less adhesive, whereas activated NSCs become more adhesive. Old activated NSCs also show decreased migration in vitro and diminished mobilization out of the niche for neurogenesis in vivo. Using tension sensors, we find that aging increases force-producing adhesions in activated NSCs. Inhibiting the cytoskeletal-regulating kinase ROCK reduces these adhesions, restores migration in old activated NSCs in vitro, and boosts neurogenesis in vivo. These results have implications for restoring the migratory potential of NSCs and for improving neurogenesis in the aged brain.

Mitochondria in cell senescence: A Friend or Foe?

Cell senescence denotes cell growth arrest in response to continuous replication or stresses damaging DNA or mitochondria. Mounting research suggests that cell senescence attributes to aging-associated failing organ function and diseases. Conversely, it participates in embryonic tissue maturation, wound healing, tissue regeneration, and tumor suppression. The acute or chronic properties and microenvironment may explain the double faces of senescence. Senescent cells display unique characteristics. In particular, its mitochondria become elongated with altered metabolomes and dynamics. Accordingly, mitochondria reform their function to produce more reactive oxygen species at the cost of low ATP production. Meanwhile, destructed mitochondrial unfolded protein responses further break the delicate proteostasis fostering mitochondrial dysfunction. Additionally, the release of mitochondrial damage-associated molecular patterns, mitochondrial Ca²⁺ overload, and altered NAD⁺ level intertwine other cellular organelle strengthening senescence. These findings further intrigue researchers to develop anti-senescence interventions. Applying mitochondrial-targeted antioxidants reduces cell senescence and mitigates aging by restoring mitochondrial function and attenuating oxidative stress. Metformin and caloric restriction also manifest senescent rescuing effects by increasing mitochondria efficiency and alleviating oxidative damage. On the other hand, Bcl2 family protein inhibitors eradicate senescent cells by inducing apoptosis to facilitate cancer chemotherapy. This review describes the different aspects of mitochondrial changes in senescence and highlights the recent progress of some anti-senescence strategies.

Emerging epigenetic dynamics in gut-microglia brain axis: experimental and clinical implications for accelerated brain aging in schizophrenia

Brain aging, which involves a progressive loss of neuronal functions, has been reported to be premature in probands affected by schizophrenia (SCZ). Evidence shows that SCZ and accelerated aging are linked to changes in epigenetic clocks. Recent cross-sectional magnetic resonance imaging analyses have uncovered reduced brain reserves and connectivity in patients with SCZ compared to typically aging individuals. These data may indicate early abnormalities of neuronal function following cyto-architectural alterations in SCZ. The current mechanistic knowledge on brain aging, epigenetic changes, and their neuropsychiatric disease association remains incomplete. With this review, we explore and summarize evidence that the dynamics of gut-resident bacteria can modulate molecular brain function and contribute to age-related neurodegenerative disorders. It is known that environmental factors such as mode of birth, dietary habits, stress, pollution, and infections can modulate the microbiota system to regulate intrinsic neuronal activity and brain reserves through the vagus nerve and enteric nervous system. Microbiota-derived molecules can trigger continuous activation of the microglial sensome, groups of receptors and proteins that permit microglia to remodel the brain neurochemistry based on complex environmental activities. This remodeling causes aberrant brain plasticity as early as fetal developmental stages, and after the onset of first-episode psychosis. In the central nervous system, microglia, the resident immune surveillance cells, are involved in neurogenesis, phagocytosis of synapses and neurological dysfunction. Here, we review recent emerging experimental and clinical evidence regarding the gut-brain microglia axis involvement in SCZ pathology and etiology, the hypothesis of brain reserve and accelerated aging induced by dietary habits, stress, pollution, infections, and other factors. We also include in our review the possibilities and consequences of gut dysbiosis activities on microglial function and dysfunction, together with the effects of antipsychotics on the gut microbiome: therapeutic and adverse effects, role of fecal microbiota transplant and psychobiotics on microglial sensomes, brain reserves and SCZ-derived accelerated aging. We end the review with suggestions that may be applicable to the clinical setting. For example, we propose that psychobiotics might contribute to antipsychotic-induced therapeutic benefits or adverse effects, as well as reduce the aging process through the gut-brain microglia axis. Overall, we hope that this review will help increase the understanding of SCZ pathogenesis as related to chronobiology and the gut microbiome, as well as reveal new concepts that will serve as novel treatment targets for SCZ.

Epigenetic aging in adult neurogenesis

Neural stem cells (NSCs) in the hippocampus generate new neurons throughout life, which functionally contribute to cognitive flexibility and mood regulation. Yet adult hippocampal neurogenesis substantially declines with age and age-related impairments in NSC activity underlie this reduction. Particularly, increased NSC quiescence and consequently reduced NSC proliferation are considered to be major drivers of the low neurogenesis levels in the aged brain. Epigenetic regulators control the gene expression programs underlying NSC quiescence, proliferation and differentiation and are hence critical to the regulation of adult neurogenesis. Epigenetic alterations have also emerged as central hallmarks of aging, and recent studies suggest the deterioration of the NSC-specific epigenetic landscape as a driver of the age-dependent decline in adult neurogenesis. In this review, we summarize the recently accumulating evidence for a role of epigenetic dysregulation in NSC aging and propose perspectives for future research directions.

Inflammation and DNA damage: cause, effect or both

Inflammation is a biological response involving immune cells, blood vessels and mediators induced by endogenous and exogenous stimuli, such as pathogens, damaged cells or chemicals. Unresolved (chronic) inflammation is characterized by the secretion of cytokines that maintain inflammation and redox stress. Mitochondrial or nuclear redox imbalance induces DNA damage, which triggers the DNA damage response (DDR) that is orchestrated by ATM and ATR kinases, which modify gene expression and metabolism and, eventually, establish the senescent phenotype. DDR-mediated senescence is induced by the signalling proteins p53, p16 and p21, which arrest the cell cycle in G1 or G2 and promote cytokine secretion, producing the senescence-associated secretory phenotype. Senescence and inflammation phenotypes are intimately associated, but highly heterogeneous because they vary according to the cell type that is involved. The vicious cycle of inflammation, DNA damage and DDR-mediated senescence, along with the constitutive activation of the immune system, is the core of an evolutionarily conserved circuitry, which arrests the cell cycle to reduce the accumulation of mutations generated by DNA replication during redox stress caused by infection or inflammation. Evidence suggests that specific organ dysfunctions in apparently unrelated diseases of autoimmune, rheumatic, degenerative and vascular origins are caused by inflammation resulting from DNA damage-induced senescence.

Mechanisms underlying the effect of voluntary running on adult hippocampal neurogenesis

Adult hippocampal neurogenesis is important for preserving learning and memory-related cognitive functions. Physical exercise, especially voluntary running, is one of the strongest stimuli to promote neurogenesis and has beneficial effects on cognitive functions. Voluntary running promotes exit of neural stem cells (NSCs) from the quiescent stage, proliferation of NSCs and progenitors, survival of newborn cells, morphological development of immature neuron, and integration of new neurons into the hippocampal circuitry. However, the detailed mechanisms driving these changes remain unclear. In this review, we will summarize current knowledge with respect to molecular mechanisms underlying voluntary running-induced neurogenesis, highlighting recent genome-wide gene expression analyses. In addition, we will discuss new approaches and future directions for dissecting the complex cellular mechanisms driving change in adult-born new neurons in response to physical exercise.

Reduction, proliferation, and differentiation defects of stem cells over time: a consequence of selective accumulation of old centrioles in the stem cells?

BACKGROUND

All molecules, structures, cells in organisms are subjected to destruction during the process of vital activities. In the organisms of most multicellular animals and humans, the regeneration process always takes place: destruction of old cells and their replacement with the new. The replacement of cells happens even if the cells are in perfect condition. The sooner the organism destroys the cells that emerged a certain time ago and replaces them with the new (i.e., the higher is the regeneration tempo), the younger the organism is.

DISCUSSION

Stem cells are progenitor cells of the substituting young cells. Asymmetric division of a mother stem cell gives rise to one, analogous to the mother, daughter cell, and to a second daughter cell that takes the path of further differentiation. Despite such asymmetric divisions, the pool of stem cells diminishes in its quantity over time. Moreover, intervals between stem cell divisions increase. The combination of these two processes causes the decline of regeneration tempo and aging of the organism.

CONCLUSION

During asymmetric stem cell divisions daughter cells, with preserved potency of the stem cell, selectively conserve mother (old) centrioles. In contrast with molecules of nuclear DNA, reparations do not take place in centrioles. Hypothetically, old centrioles are more subjected to destruction than other structures of a cell-which makes centrioles potentially the main structure of aging.

Implications of Hypothalamic Neural Stem Cells on Aging and Obesity-Associated Cardiovascular Diseases

The hypothalamus, one of the major regulatory centers in the brain, controls various homeostatic processes, and hypothalamic neural stem cells (htNSCs) have been observed to interfere with hypothalamic mechanisms regulating aging. NSCs play a pivotal role in the repair and regeneration of brain cells during neurodegenerative diseases and rejuvenate the brain tissue microenvironment. The hypothalamus was recently observed to be involved in neuroinflammation mediated by cellular senescence. Cellular senescence, or systemic aging, is characterized by a progressive irreversible state of cell cycle arrest that causes physiological dysregulation in the body and it is evident in many neuroinflammatory conditions, including obesity. Upregulation of neuroinflammation and oxidative stress due to senescence has the potential to alter the functioning of NSCs. Various studies have substantiated the chances of obesity inducing accelerated aging. Therefore, it is essential to explore the potential effects of htNSC dysregulation in obesity and underlying pathways to develop strategies to address obesity-induced comorbidities associated with brain aging. This review will summarize hypothalamic neurogenesis associated with obesity and prospective NSC-based regenerative therapy for the treatment of obesity-induced cardiovascular conditions.

Adult hippocampal neurogenesis in Alzheimer's disease: A roadmap to clinical relevance

Adult hippocampal neurogenesis (AHN) drops sharply during early stages of Alzheimer's disease (AD), via unknown mechanisms, and correlates with cognitive status in AD patients. Understanding AHN regulation in AD could provide a framework for innovative pharmacological interventions. We here combine molecular, behavioral, and clinical data and critically discuss the multicellular complexity of the AHN niche in relation to AD pathophysiology. We further present a roadmap toward a better understanding of the role of AHN in AD by probing the promises and caveats of the latest technological advancements in the field and addressing the conceptual and methodological challenges ahead.

Interferon regulates neural stem cell function at all ages by orchestrating mTOR and cell cycle

Stem cells show intrinsic interferon signalling, which protects them from viral infections at all ages. In the ageing brain, interferon signalling also reduces the ability of stem cells to activate. Whether these functions are linked and at what time interferons start taking on a role in stem cell functioning is unknown. Additionally, the molecular link between interferons and activation in neural stem cells and how this relates to progenitor production is not well understood. Here we combine single-cell transcriptomics, RiboSeq and mathematical models of interferon to show that this pathway is important for proper stem cell function at all ages in mice. Interferon orchestrates cell cycle and mTOR activity to post-transcriptionally repress Sox2 and induces quiescence. The interferon response then decreases in the subsequent maturation states. Mathematical simulations indicate that this regulation is beneficial for the young and harmful for the old brain. Our study establishes molecular mechanisms of interferon in stem cells and interferons as genuine regulators of stem cell homeostasis and a potential therapeutic target to repair the ageing brain.

The Double-Edged Role of Extracellular Vesicles in the Hallmarks of Aging

The exponential growth in the elderly population and their associated socioeconomic burden have recently brought aging research into the spotlight. To integrate current knowledge and guide potential interventions, nine biochemical pathways are summarized under the term hallmarks of aging. These hallmarks are deeply inter-related and act together to drive the aging process. Altered intercellular communication is particularly relevant since it explains how damage at the cellular level translates into age-related loss of function at the organismal level. As the main effectors of intercellular communication, extracellular vesicles (EVs) might play a key role in the aggravation or mitigation of the hallmarks of aging. This review aims to summarize this role and to provide context for the multiple emerging EV-based gerotherapeutic strategies that are currently under study.

The Role of SOX Transcription Factors in Ageing and Age-Related Diseases

The quest for eternal youth and immortality is as old as humankind. Ageing is an inevitable physiological process accompanied by many functional declines that are driving factors for age-related diseases. Stem cell exhaustion is one of the major hallmarks of ageing. The SOX transcription factors play well-known roles in self-renewal and differentiation of both embryonic and adult stem cells. As a consequence of ageing, the repertoire of adult stem cells present in various organs steadily declines, and their dysfunction/death could lead to reduced regenerative potential and development of age-related diseases. Thus, restoring the function of aged stem cells, inducing their regenerative potential, and slowing down the ageing process are critical for improving the health span and, consequently, the lifespan of humans. Reprograming factors, including SOX family members, emerge as crucial players in rejuvenation. This review focuses on the roles of SOX transcription factors in stem cell exhaustion and age-related diseases, including neurodegenerative diseases, visual deterioration, chronic obstructive pulmonary disease, osteoporosis, and age-related cancers. A better understanding of the molecular mechanisms of ageing and the roles of SOX transcription factors in this process could open new avenues for developing novel strategies that will delay ageing and prevent age-related diseases.

Cellular Senescence and Ageing

Cellular senescence has become a subject of great interest within the ageing research field over the last 60 years, from the first observation in vitro by Leonard Hayflick and Paul Moorhead in 1961, to novel findings of phenotypic sub-types and senescence-like phenotype in post-mitotic cells. It has essential roles in wound healing, tumour suppression and the very first stages of human development, while causing widespread damage and dysfunction with age leading to a raft of age-related diseases. This chapter discusses these roles and their interlinking pathways, and how the observed accumulation of senescent cells with age has initiated a whole new field of ageing research, covering pathologies in the heart, liver, kidneys, muscles, brain and bone. This chapter will also examine how senescent cell accumulation presents in these different tissues, along with their roles in disease development. Finally, there is much focus on developing treatments for senescent cell accumulation in advanced age as a method of alleviating age-related disease. We will discuss here the various senolytic and senostatic treatment approaches and their successes and limitations, and the innovative new strategies being developed to address the differing effects of cellular senescence in ageing and disease.

Minoxidil Regulates Aging-Like Phenotypes in Rat Cortical Astrocytes In Vitro

Mainly due to the slanted focus on the mechanism and regulation of neuronal aging, research on astrocyte aging and its modulation during brain aging is scarce. In this study, we established aged astrocyte culture model by long-term culturing. Cellular senescence was confirmed through SA-β-gal staining as well as through the examination of morphological, molecular, and functional markers. RNA sequencing and functional analysis of astrocytes were performed to further investigate the detailed characteristics of the aged astrocyte model. Along with aged phenotypes, decreased astrocytic proliferation, migration, mitochondrial energetic function and support for neuronal survival and differentiation has been observed in aged astrocytes. In addition, increased expression of cytokines and chemokine-related factors including plasminogen activator inhibitor -1 (PAI-1) was observed in aged astrocytes. Using the RNA sequencing results, we searched potential drugs that can normalize the dysregulated gene expression pattern observed in long-term cultured aged astrocytes. Among several candidates, minoxidil, a pyrimidine-derived anti-hypertensive and anti-pattern hair loss drug, normalized the increased number of SA-β-gal positive cells and nuclear size in aged astrocytes. In addition, minoxidil restored up-regulated activity of PAI-1 and increased mitochondrial superoxide production in aged astrocytes. We concluded that long term culture of astrocytes can be used as a reliable model for the study of astrocyte senescence and minoxidil can be a plausible candidate for the regulation of brain aging.

Dietary restriction in senolysis and prevention and treatment of disease

Aging represents a key risk factor for a plethora of diseases. Targeting detrimental processes which occur during aging, especially before onset of age-related disease, could provide drastic improvements in healthspan. There is increasing evidence that dietary restriction (DR), including caloric restriction, fasting, or fasting-mimicking diets, extend both lifespan and healthspan. This has sparked interest in the use of dietary regimens as a non-pharmacological means to slow aging and prevent disease. Here, we review the current evidence on the molecular mechanisms underlying DR-induced health improvements, including removal of senescent cells, metabolic reprogramming, and epigenetic rejuvenation.

Aberrant activation of p53/p66Shc-mInsc axis increases asymmetric divisions and attenuates proliferation of aged mammary stem cells

Aging is accompanied by the progressive decline in tissue regenerative capacity and functions of resident stem cells (SCs). Underlying mechanisms, however, remain unclear. Here we show that, during chronological aging, self-renewing mitoses of mammary SCs (MaSCs) are preferentially asymmetric and that their progeny divides less frequently, leading to decreased number of MaSCs and reduced regenerative potential. Underlying mechanisms are investigated in the p66Shc-/- mouse, which exhibits several features of delayed aging, including reduced involution of the mammary gland (MG). p66Shc is a mitochondrial redox sensor that activates a specific p53 transcriptional program, in which the aging-associated p44 isoform of p53 plays a pivotal role. We report here that aged p66Shc-/- MaSCs show increased symmetric divisions, increased proliferation and increased regenerative potential, to an extent reminiscent of young wild-type (WT) MaSCs. Mechanistically, we demonstrate that p66Shc, together with p53: (i) accumulates in the aged MG, (ii) sustains expression of the cell polarity determinant mInscuteable and, concomitantly, (iii) down-regulates critical cell cycle genes (e.g.,: Cdk1 and Cyclin A). Accordingly, overexpression of p53/p44 increases asymmetric divisions and decreases proliferation of young WT MaSCs in a p66Shc-dependent manner and overexpression of mInsc restores WT-like levels of asymmetric divisions in aged p66Shc-/- MaSCs. Notably, deletion of p66Shc has negligible effects in young MaSCs and MG development. These results demonstrate that MG aging is due to aberrant activation of p66Shc, which induces p53/p44 signaling, leading to failure of symmetric divisions, decreased proliferation and reduced regenerative potential of MaSCs.

Androgens, aging, and prostate health

Due to late onset hypogonadism (LOH), there is an increased usage of testosterone replacement therapy (TRT) in the aging male population. Since prostate is a target organ for androgens and anti-androgenic strategies are used to treat and palliate benign prostate hyperplasia (BPH) and prostate cancer (PC), the prevalence of both increases with age, the possible influence of TRT on prostate health becomes highly relevant. The present review summarizes existing data on the associations between endogenous hormone concentrations and prostate growth and concludes that circulating concentrations of androgens do not appear to be associated with the risks of development of BPH or initiation or progression of PC. The explanation for these findings relates to an apparent insensitivity of prostatic tissue to changes of testosterone concentrations within the physiological range.

Frailty biomarkers under the perspective of geroscience: A narrative review

Cellular and molecular aging biomarkers might contribute to identify at-risk individuals for frailty before overt clinical manifestations appear. Although studies on the associations of aging biomarkers and frailty exist, no investigation has gathered this information using a structured framework for identifying aging biomarkers; as a result, the evidence on frailty and aging biomarkers is diffuse and incomplete. Therefore, this narrative review aimed to gather information on the associations of the hallmarks of aging and frailty under the perspective of geroscience. The literature on human studies on this topic is sparse and mainly composed of cross-sectional investigations performed in small study samples. The main putative aging biomarkers associated to frailty were: mitochondrial DNA copy number (genomic instability and mitochondrial dysfunction), telomere length (telomere attrition), global DNA methylation (epigenetic alterations), Hsp70 and Hsp72 (loss of proteostasis), IGF-1 and SIRT1 (deregulated nutrient-sensing), GDF-15 (mitochondrial dysfunction, cellular senescence and altered intercellular communication), CD4 + and CD8 + cell percentages (cellular senescence), circulating osteogenic progenitor (COP) cells (stem cell exhaustion), and IL-6, CRP and TNF-alpha (altered intercellular communication). IGF-1, SIRT1, GDF-15, IL-6, CRP and TNF-alpha presented more evidence among these biomarkers, highlighting the importance of inflammation and nutrient sensing on frailty. Further longitudinal studies investigating biomarkers across the hallmarks of aging would provide valuable information on this topic.

Impaired Mitochondria Promote Aging-Associated Sebaceous Gland Dysfunction and Pathology

Mitochondrial dysfunction is one of the hallmarks of aging. Changes in sebaceous gland (SG) function and sebum production have been reported during aging. This study shows the direct effects of mitochondrial dysfunction on SG morphology and function. A mitochondrial DNA (mtDNA) depleter mouse was used as a model for introducing mitochondrial dysfunction in the whole animal. The effects on skin SGs and modified SGs of the eyelid, lip, clitoral, and preputial glands were characterized. The mtDNA depleter mice showed gross morphologic and histopathologic changes in SGs associated with increased infiltration by mast cells, neutrophils, and polarized macrophages. Consistently, there was increased expression of proinflammatory cytokines. The inflammatory changes were associated with abnormal sebocyte accumulation of lipid, defective sebum delivery at the skin surface, and the up-regulation of key lipogenesis-regulating genes and androgen receptor. The mtDNA depleter mice expressed aging-associated senescent marker. Increased sebocyte proliferation and aberrant expression of stem cell markers were observed. These studies provide, for the first time, a causal link between mitochondrial dysfunction and abnormal sebocyte function within sebaceous and modified SGs throughout the whole body of the animal. They suggest that mtDNA depleter mouse may serve as a novel tool to develop targeted therapeutics to address SG disorders in aging humans.

Therapeutic Antiaging Strategies

Aging constitutes progressive physiological changes in an organism. These changes alter the normal biological functions, such as the ability to manage metabolic stress, and eventually lead to cellular senescence. The process itself is characterized by nine hallmarks: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. These hallmarks are risk factors for pathologies, such as cardiovascular diseases, neurodegenerative diseases, and cancer. Emerging evidence has been focused on examining the genetic pathways and biological processes in organisms surrounding these nine hallmarks. From here, the therapeutic approaches can be addressed in hopes of slowing the progression of aging. In this review, data have been collected on the hallmarks and their relative contributions to aging and supplemented with in vitro and in vivo antiaging research experiments. It is the intention of this article to highlight the most important antiaging strategies that researchers have proposed, including preventive measures, systemic therapeutic agents, and invasive procedures, that will promote healthy aging and increase human life expectancy with decreased side effects.

3-deazaadenosine (3DA) alleviates senescence to promote cellular fitness and cell therapy efficiency in mice

Cellular senescence is a stable type of cell cycle arrest triggered by different stresses. As such, senescence drives age-related diseases and curbs cellular replicative potential. Here, we show that 3-deazaadenosine (3DA), an S-adenosyl homocysteinase (AHCY) inhibitor, alleviates replicative and oncogene-induced senescence. 3DA-treated senescent cells showed reduced global Histone H3 Lysine 36 trimethylation (H3K36me3), an epigenetic modification that marks the bodies of actively transcribed genes. By integrating transcriptome and epigenome data, we demonstrate that 3DA treatment affects key factors of the senescence transcriptional program. Remarkably, 3DA treatment alleviated senescence and increased the proliferative and regenerative potential of muscle stem cells from very old mice in vitro and in vivo. Moreover, ex vivo 3DA treatment was sufficient to enhance the engraftment of human umbilical cord blood (UCB) cells in immunocompromised mice. Together, our results identify 3DA as a promising drug enhancing the efficiency of cellular therapies by restraining senescence.

Autophagy at the intersection of aging, senescence, and cancer

Autophagy is an evolutionarily conserved cellular process in which macromolecules undergo lysosomal degradation. It fulfills essential roles in quality controlling cellular constituents and in energy homeostasis. Basal autophagy is also widely accepted to provide a protective role in aging and aging-related disorders, and its decline with age might precipitate the onset of a variety of diseases. In this review, we discuss the role of basal autophagy in maintaining homeostasis, in part through the maintenance of stem cell populations and the prevention of cellular senescence. We also consider how stress-induced senescence, for example, during oncogene activation and in premalignant disease, might rely on autophagy, and the possibility that the age-associated decline in autophagy might promote tumour development through a variety of mechanisms. Ultimately, evidence suggests that autophagy is required for malignant cancer progression in a number of settings. Thus, autophagy appears to be tumour-suppressive during the early stages of tumorigenesis and tumour-promoting at later stages.

P16INK4A—More Than a Senescence Marker

Aging is a biological feature that is characterized by gradual degeneration of function in cells, tissues, organs, or an intact organism due to the accumulation of environmental factors and stresses with time. Several factors have been attributed to aging such as oxidative stress and augmented production or exposure to reactive oxygen species, inflammatory cytokines production, telomere shortening, DNA damage, and, importantly, the deposit of senescent cells. These are irreversibly mitotically inactive, yet metabolically active cells. The reason underlying their senescence lies within the extrinsic and the intrinsic arms. The extrinsic arm is mainly characterized by the expression and the secretory profile known as the senescence-associated secretory phenotype (SASP). The intrinsic arm results from the impact of several genes meant to regulate the cell cycle, such as tumor suppressor genes. P16^INK4A is a tumor suppressor and cell cycle regulator that has been linked to aging and senescence. Extensive research has revealed that p16 expression is significantly increased in senescent cells, as well as during natural aging or age-related pathologies. Based on this fact, p16 is considered as a specific biomarker for detecting senescent cells and aging. Other studies have found that p16 is not only a senescence marker, but also a protein with many functions outside of senescence and aging. In this paper, we discuss and shed light on several studies that show the different functions of p16 and provide insights in its role in several biological processes besides senescence and aging.

Potential Satellite Cell-Linked Biomarkers in Aging Skeletal Muscle Tissue: Proteomics and Proteogenomics to Monitor Sarcopenia

Sarcopenia (Sp) is the loss of skeletal muscle mass associated with aging which causes an involution of muscle function and strength. Satellite cells (Sc) are myogenic stem cells, which are activated by injury or stress, and repair muscle tissue. With advancing age, there is a decrease in the efficiency of the regenerative response of Sc. Diagnosis occurs with the Sp established by direct assessments of muscle. However, the detection of biomarkers in real-time biofluids by liquid biopsy could represent a step-change in the understanding of the molecular biology and heterogeneity of Sp. A total of 13 potential proteogenomic biomarkers of Sp by their physiological and biological interaction with Sc have been previously described in the literature. Increases in the expression of GDF11, PGC-1α, Sirt1, Pax7, Pax3, Myf5, MyoD, CD34, MyoG, and activation of Notch signaling stimulate Sc activity and proliferation, which could modulate and delay Sp progression. On the contrary, intensified expression of GDF8, p16INK4a, Mrf4, and activation of the Wnt pathway would contribute to early Sp development by directly inducing reduced and/or altered Sc function, which would attenuate the restorative capacity of skeletal muscle. Additionally, tissue biopsy remains an important diagnostic tool. Proteomic profiling of aged muscle tissues has shown shifts toward protein isoforms characteristic of a fast-to-slow transition process and an elevated number of oxidized proteins. In addition, a strong association between age and plasma values of growth differentiation factor 15 (GDF-15) has been described and serpin family A member 3 (serpin A3n) was more secreted by atrophied muscle cells. The identification of these new biomarkers holds the potential to change personalized medicine because it could predict in real time the course of Sp by monitoring its evolution and assessing responses to potential therapeutic strategies.

Inducible motor neuron differentiation of human induced pluripotent stem cells in vivo

OBJECTIVES

Transplantation of neural progenitor cells (NPCs) derived from human-induced pluripotent stem cells (hiPSCs) is one of the promising treatment strategies for motor neuron diseases (MNDs). However, the inefficiency in committed differentiation of NPCs in vivo limits its application. Here, we tried to establish a potential therapeutic strategy for MNDs by in vivo directional differentiation of hiPSCs engineered with motor neuron (MN) specific transcription factors and Tet-On system.

MATERIALS AND METHODS

We engineered hiPSCs with three MN-specific transcription factors and Tet-On system. The engineered cells were directly transplanted into immunodeficient mice through subcutaneous, intra-spinal cord and intracerebroventricular injections. Following doxycycline (Dox) induction, teratoma formation, and motor MN differentiation were evaluated.

RESULTS

We generated genetically engineered hiPSCs, in which the expression of Ngn2, Isl1, and Lhx3 was controlled by a drug-inducible transgenic system. These cells showed normal pluripotency and proliferative capacity, and were able to directionally differentiate into mature motor neurons (MNs) and NPCs with high efficiency in spinal cords and cerebral lateral ventricles under the induction of Dox. The grafts showed long-term survival in the recipient mice without formation of teratoma.

CONCLUSIONS

The induced mature MNs and NPCs were expected to replace the damaged endogenous MNs directly, and play a role of de novo stem cell stock for long-term neuron damage repair, respectively. Therefore, in vivo directional differentiation of the hiPSCs engineered with MN-specific transcription factors and Tet-On system via Dox induction could be a potential therapeutic strategy for MNDs with high efficacy and safety.

Mechanisms involved in hematopoietic stem cell aging

Hematopoietic stem cells (HSCs) undergo progressive functional decline over time due to both internal and external stressors, leading to aging of the hematopoietic system. A comprehensive understanding of the molecular mechanisms underlying HSC aging will be valuable in developing novel therapies for HSC rejuvenation and to prevent the onset of several age-associated diseases and hematological malignancies. This review considers the general causes of HSC aging that range from cell-intrinsic factors to cell-extrinsic factors. In particular, epigenetics and inflammation have been implicated in the linkage of HSC aging, clonality, and oncogenesis. The challenges in clarifying mechanisms of HSC aging have accelerated the development of therapeutic interventions to rejuvenate HSCs, the major goal of aging research; these details are also discussed in this review.

Role of low-dose radiation in senescence and aging: A beneficial perspective

Cellular senescence refers to the permanent arrest of cell cycle caused by intrinsic and/or extrinsic stressors including oncogene activation, irradiation, DNA damage, oxidative stress, and certain cytokines (including senescence associated secretory phenotype). Cellular senescence is an important factor in aging. Accumulation of senescent cells has been implicated in the causation of various age-related organ disorders, tissue dysfunction, and chronic diseases. It is widely accepted that the biological effects triggered by low-dose radiation (LDR) are different from those caused by high-dose radiation. Experimental evidence suggests that LDR may promote growth and development, enhance longevity, induce embryo production, and delay the progression of chronic diseases. The underlying mechanisms of these effects include modulation of immune response, stimulation of hematopoietic system, antioxidative effect, reduced DNA damage and improved ability for DNA damage repair. In this review, we discuss the possible mechanisms by which LDR prevents senescence and aging from the perspectives of inhibiting cellular senescence and promoting the removal of senescent cells. We review a wide broad of evidence about the beneficial impact of LDR in senescence and aging models (including cardiovascular diseases, neurological diseases, arthritis and osteoporosis, chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis) to highlight the potential value of LDR in preventing aging and age-related diseases. However, there is no consensus on the effect of LDR on human health, and several important aspects require further investigation.

Senescence: Pathogenic Driver in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is recognized as a disease of accelerated lung aging. Over the past two decades, mounting evidence suggests an accumulation of senescent cells within the lungs of patients with COPD that contributes to dysregulated tissue repair and the secretion of multiple inflammatory proteins, termed the senescence-associated secretory phenotype (SASP). Cellular senescence in COPD is linked to telomere dysfunction, DNA damage, and oxidative stress. This review gives an overview of the mechanistic contributions and pathologic consequences of cellular senescence in COPD and discusses potential therapeutic approaches targeting senescence-associated signaling in COPD.

Pin1-mediated regulation of articular cartilage stem/progenitor cell aging

Cartilage stem/progenitor cells (CSPCs) was recently isolated and identified from the cartilage tissue. CSPCs is essential for repair and regeneration of cartilage in osteoarthritis (OA). Aging is a primary risk factor for cartilage damage and joint OA. Although studies have confirmed the link between cell aging and OA, the underlying molecular mechanisms regulating CSPCs aging are not fully understood. In this study, we investigated the role of Pin1 in the aging of rat knee joint CSPCs. We isolated CSPCs from rat knee joints and demonstrated that, in long-term in vitro culture, Pin1 protein levels are significantly reduced. At the same time, expression of the senescence-related β-galactosidase and the senescence marker p16^INK4A were markedly elevated. In addition, Pin1 overexpression reversed the progression of cellular senescence, as evidenced by the down-regulation of senescence-related β-galactosidase, increased EdU positive cells and diminished levels of p16^INK4A. In contrast, Pin1 siRNA incorporation promoted CSPCs senescence. In addition, we also observed the distribution of cell cycles through flow cytometry and revealed that Pin1 deficiency results in cell cycle arrest in the G1 phase, suggesting severe lack of proliferation ability, a sign of cellular senescence. Collectively, these results validated that Pin1 is an essential regulator of CSPCs aging.

Neurogenesis in aging and age-related neurodegenerative diseases

Adult neurogenesis, the process by which neurons are generated in certain areas of the adult brain, declines in an age-dependent manner and is one potential target for extending cognitive healthspan. Aging is a major risk factor for neurodegenerative diseases and, as lifespans are increasing, these health challenges are becoming more prevalent. An age-associated loss in neural stem cell number and/or activity could cause this decline in brain function, so interventions that reverse aging in stem cells might increase the human cognitive healthspan. In this review, we describe the involvement of adult neurogenesis in neurodegenerative diseases and address the molecular mechanistic aspects of neurogenesis that involve some of the key aggregation-prone proteins in the brain (i.e., tau, Aβ, α-synuclein, …). We summarize the research pertaining to interventions that increase neurogenesis and regulate known targets in aging research, such as mTOR and sirtuins. Lastly, we share our outlook on restoring the levels of neurogenesis to physiological levels in elderly individuals and those with neurodegeneration. We suggest that modulating neurogenesis represents a potential target for interventions that could help in the fight against neurodegeneration and cognitive decline.

Aging of enteric neuromuscular systems in gastrointestinal tract

BACKGROUND

Aging is a complex biological process and associated with a progressive decline in functions of most organs including the gastrointestinal (GI) tract. Age-related GI motor disorders/dysfunctions include esophageal reflux, dysphagia, constipation, fecal incontinence, reduced compliance, and accommodation. Although the incidence and severity of these diseases and conditions increase with age, they are often underestimated due in part to nonspecific and variable symptoms and lack of sufficient medical attention. They negatively affect quality of life and predispose the elderly to other diseases, sarcopenia, and frailty. The mechanisms underlying aging-associated GI dysfunctions remain unclear, and there is limited data examining the effect of aging on GI motor functions. Many studies on aging-associated changes to cells within the tunica muscularis including enteric neurons, smooth muscles, and interstitial cells have proposed that cell loss and/or molecular changes may be involved in the pathogenesis of age-related GI motor disorders/dysfunctions. There is also evidence that the aging contributes to phenotypic changes in innate immune cells, which are physically and functionally linked to other cells in the tunica muscularis and can alter GI (patho) physiology. However, various patterns of changes have been reported, some of which are contradictory, indicating a need for additional work in this area.

PURPOSE

Although GI infection due to intestinal bacterial overgrowth, bleeding, and cancers are also important and common problems in the elderly patients, this mini-review focuses on data obtained from enteric neuromuscular aging research with the goal of better understanding the cellular and molecular mechanisms of enteric neuromuscular aging to enhance future therapy.

The hypothalamus for whole-body physiology: from metabolism to aging

Obesity and aging are two important epidemic factors for metabolic syndrome and many other health issues, which contribute to devastating diseases such as cardiovascular diseases, stroke and cancers. The brain plays a central role in controlling metabolic physiology in that it integrates information from other metabolic organs, sends regulatory projections and orchestrates the whole-body function. Emerging studies suggest that brain dysfunction in sensing various internal cues or processing external cues may have profound effects on metabolic and other physiological functions. This review highlights brain dysfunction linked to genetic mutations, sex, brain inflammation, microbiota, stress as causes for whole-body pathophysiology, arguing brain dysfunction as a root cause for the epidemic of aging and obesity-related disorders. We also speculate key issues that need to be addressed on how to reveal relevant brain dysfunction that underlines the development of these disorders and diseases in order to develop new treatment strategies against these health problems.

Four calcium signaling pathway-related genes were upregulated in microcystic adnexal carcinoma: transcriptome analysis and immunohistochemical validation

BACKGROUND

Microcystic adnexal carcinoma (MAC) is a skin cancer with challenges in diagnosis and management. This study was aimed to detect molecular alterations of MAC and guide its pathologic diagnosis and treatment.

METHODS

We performed transcriptome analysis on 5 MAC and 5 normal skin tissues, identified the differentially expressed genes, and verified them by immunohistochemistry.

RESULTS

Three hundred four differentially expressed genes (DEGs) in MAC were identified by next-generation transcriptome sequencing, among which 225 genes were upregulated and 79 genes were downregulated. Four genes of the calcium signaling pathway, including calcium voltage-gated channel subunit alpha 1 S (CACNA1S), ATPase sarcoplasmic/endoplasmic reticulum Ca2+ transporting 1 (ATP2A1), ryanodine receptor 1 (RYR1), and myosin light chain kinase 3 (MYLK3), were upregulated and then been verified by immunohistochemistry. The expression of CACNA1S, ATP2A1, RYR1, and MYLK3 was upregulated in MAC compared with normal sweat glands and syringoma tumor cells and was generally negative in trichoepithelioma and infundibulocystic type basal cell carcinoma.

CONCLUSIONS

The four genes of the calcium signaling pathway were upregulated in MAC at both RNA and protein levels. CACNA1S, ATP2A1, RYR1, and MYLK3 may be new diagnostic molecular markers and therapeutic targets for MAC.

Effects of Changes in Osmolarity on the Biological Activity of Human Normal Nucleus Pulposus Mesenchymal Stem Cells

The expansion and maintenance of the NPMSC (nucleus pulposus mesenchymal stem cell) phenotype are considered as potential therapeutic tools for clinical applications in intervertebral disc tissue engineering and regenerative medicine. However, the harsh microenvironment within the intervertebral disc is the main limitation of its regeneration. The osmolarity of the intervertebral disc is higher than that of other tissues, which has an important influence on the biological characteristics of NPMSCs. In this study, we observed the effect of different osmolarities on the biological characteristics of human normal NPMSCs cultured in vitro and explored the role of osmolarity in intervertebral disc degeneration. Our data demonstrated that the change in osmotic pressure has an important effect on the biological activity of NPMSCs, and this effect may occur through the P16^INK4A/Rb pathway. This study provides a theoretical basis for the future treatment of intervertebral disc degeneration.

Spatial transcriptomic analysis reveals inflammatory foci defined by senescent cells in the white matter, hippocampi and cortical grey matter in the aged mouse brain

There is strong evidence that aging is associated with an increased presence of senescent cells in the brain. The finding that treatment with senolytic drugs improves cognitive performance of aged laboratory mice suggests that increased cellular senescence is causally linked to age-related cognitive decline. The relationship between senescent cells and their relative locations within the brain is critical to understanding the pathology of age-related cognitive decline and dementia. To assess spatial distribution of cellular senescence in the aged mouse brain, spatially resolved whole transcriptome mRNA expression was analyzed in sections of brains derived from young (3 months old) and aged (28 months old) C57BL/6 mice while capturing histological information in the same tissue section. Using this spatial transcriptomics (ST)-based method, microdomains containing senescent cells were identified on the basis of their senescence-related gene expression profiles (i.e., expression of the senescence marker cyclin-dependent kinase inhibitor p16INK4A encoded by the Cdkn2a gene) and were mapped to different anatomical brain regions. We confirmed that brain aging is associated with increased cellular senescence in the white matter, the hippocampi and the cortical grey matter. Transcriptional analysis of the senescent cell-containing ST spots shows that presence of senescent cells is associated with a gene expression signature suggestive of neuroinflammation. GO enrichment analysis of differentially expressed genes in the outer region of senescent cell-containing ST spots ("neighboring ST spots") also identified functions related to microglia activation and neuroinflammation. In conclusion, senescent cells accumulate with age in the white matter, the hippocampi and cortical grey matter and likely contribute to the genesis of inflammatory foci in a paracrine manner.