Senescent cells: an emerging target for diseases of ageing

Targeting cellular senescence: A promising approach in respiratory diseases

Cellular senescence serves as a significant tumor suppression mechanism in mammals. Cellular senescence is induced in response to various stressors and acts as a safeguard against the uncontrolled proliferation of damaged cells that could lead to malignant transformation. Senescent cells also exhibit a distinctive feature known as the senescence-associated secretory phenotype (SASP), wherein they secrete a range of bioactive molecules, including pro-inflammatory cytokines, growth factors, and proteases. These SASP components have both local and systemic effects, influencing the surrounding microenvironment and distant tissues, and have been implicated in the processes of tissue aging and the development of chronic diseases. Recent studies utilizing senolysis models have shed light on the potential therapeutic implications of targeting senescent cells. The targeting of senescent cell may alleviate the detrimental effects associated with cellular senescence and its SASP components. Senolytics have shown promise in preclinical studies for treating age-related pathologies and chronic diseases, including cancer, cardiovascular disorders, and neurodegenerative conditions. Respiratory diseases have emerged as a significant global health concern, responsible for a considerable number of deaths worldwide. Extensive research conducted in both human subjects and animal models has demonstrated the involvement of cellular senescence in the pathogenesis of respiratory diseases. Chronic pulmonary conditions such as chronic obstructive pulmonary disease and idiopathic pulmonary fibrosis have been linked to the accumulation of senescent cells. This review aims to present the findings from research on respiratory diseases that have utilized systems targeting senescent cells and to identify potential therapeutic strategies for the clinical management of these conditions. Geriatr Gerontol Int 2024; 24: 60-66.

Extracellular vesicles from human urine-derived stem cells delay aging through the transfer of PLAU and TIMP1

Aging increases the risks of various diseases and the vulnerability to death. Cellular senescence is a hallmark of aging that contributes greatly to aging and aging-related diseases. This study demonstrates that extracellular vesicles from human urine-derived stem cells (USC-EVs) efficiently inhibit cellular senescence in vitro and in vivo. The intravenous injection of USC-EVs improves cognitive function, increases physical fitness and bone quality, and alleviates aging-related structural changes in different organs of senescence-accelerated mice and natural aging mice. The anti-aging effects of USC-EVs are not obviously affected by the USC donors' ages, genders, or health status. Proteomic analysis reveals that USC-EVs are enriched with plasminogen activator urokinase (PLAU) and tissue inhibitor of metalloproteinases 1 (TIMP1). These two proteins contribute importantly to the anti-senescent effects of USC-EVs associated with the inhibition of matrix metalloproteinases, cyclin-dependent kinase inhibitor 2A (P16INK4a), and cyclin-dependent kinase inhibitor 1A (P21cip1). These findings suggest a great potential of autologous USC-EVs as a promising anti-aging agent by transferring PLAU and TIMP1 proteins.

Resolvin D1 suppresses macrophage senescence and splenic fibrosis in aged mice

Aging is associated with systemic, non-resolving inflammation and the accumulation of senescent cells. The resolution of inflammation (or inflammation-resolution) is in part mediated by the balance between specialized pro-resolving mediators (SPMs) and pro-inflammatory leukotrienes (LTs). Aged mice (i.e. 2 years of age) exhibit a significant decrease in the SPM:LT ratio in specific organs including the spleen, which suggests that this organ may exhibit heightened inflammation and may be particularly amenable to SPM therapy. Previous studies have shown that resolvin D1 (RvD1) is decreased in spleens of aged mice compared with young controls. Therefore, we asked whether treatment of RvD1 in aged mice would impact markers of cellular senescence in splenic macrophages, and downstream effects on splenic fibrosis, a hallmark of splenic aging. We found that in aged mice, both zymosan-elicited and splenic macrophages showed an increase in mRNA expression of inflammatory and eicosanoid biosynthesis genes and a dysregulation of genes involved in the cell cycle. Injections with RvD1 reversed these changes. Importantly, RvD1 also decreased splenic fibrosis, a hallmark of splenic aging. Our findings suggest that RvD1 treatment may limit several features of aging, including senescence and fibrosis in spleens from aged mice. Summary Aging is associated with systemic, low grade, non-resolving inflammation. The resolution of inflammation is in part mediated by the balance between specialized pro-resolving mediators (SPMs) and pro-inflammatory lipid mediators, like leukotrienes (LTs). A hallmark of aging is the accumulation of senescent cells that promote low grade inflammation by secreting pro-inflammatory cytokines and lipid mediators. Splenic macrophages contribute to systemic aging, and spleens of aged mice demonstrate decreased levels of the SPM called resolvin D1 (RvD1). Whether addition of RvD1 is protective in spleens of aged mice is unknown and is focus of this study. RvD1 treatment to aged mice led to decreased mRNA expression of markers of cellular senescence and inflammation in splenic macrophages compared with age-matched vehicle controls. Moreover, RvD1 decreased splenic fibrosis, which occurs due to persistent low-grade inflammation in aging. Promoting inflammation resolution with RvD1 thus limits macrophage senescence, pro-inflammatory signals and established splenic fibrosis in aging.

Senescence-regulatory factors as novel circulating biomarkers and therapeutic targets in regenerative medicine for osteoarthritis

Recent discoveries reveal that the chronic presence of senescent cells in osteoarticular tissues provides a focal point of disease development for osteoarthritis (OA). Nevertheless, senescence-regulatory factors associated with OA still need to be identified. Furthermore, few diagnostic- and prognostic-validated biochemical markers (biomarkers) are currently used in clinics to evaluate OA patients. In the future, alongside imaging and clinical examination, detecting senescence-regulatory biomarkers in patient fluids could become a prospective method for disease: diagnosis, monitoring, progression and prognosis following treatment. This review summarizes a group of circulating OA biomarkers recently linked to senescence onset. Remarkably, these factors identified in proteomics, metabolomic and microRNA studies could also have deleterious or protective roles in osteoarticular tissue homeostasis. In addition, we discuss their potentially innovative modulation in combination with senotherapeutic approaches, for long-lasting OA treatment.

Circular RNAs: Regulators of endothelial cell dysfunction in atherosclerosis

Endothelial cell (EC) dysfunction is associated with atherosclerosis. Circular RNAs (circRNAs) are covalently closed loops formed by back-splicing, are highly expressed in a tissue-specific or cell-specific manner, and regulate ECs mainly through miRNAs (mircoRNAs) or protein sponges. This review describes the regulatory mechanisms and physiological functions of circRNAs, as well as the differential expression of circRNAs in aberrant ECs. This review focuses on their roles in inflammation, proliferation, migration, angiogenesis, apoptosis, senescence, and autophagy in ECs from the perspective of signaling pathways, such as nuclear factor κB (NF-κB), nucleotide-binding domain, leucine-rich-repeat family, pyrin-domain-containing 3 (NLRP3)/caspase-1, Janus kinase/signal transducer and activator of transcription (JAK/STAT), and phosphoinositide-3 kinase/protein kinase B (PI3K/Akt). Finally, we address the issues and recent advances in circRNAs as well as circRNA-mediated regulation of ECs to improve our understanding of the molecular mechanisms underlying the progression of atherosclerosis and provide a reference for studies on circRNAs that regulate EC dysfunction and thus affect atherosclerosis.

Role of astrocyte senescence regulated by the non- canonical autophagy in the neuroinflammation associated to cerebral malaria

BACKGROUND

Cerebral malaria (CM) is a fatal neuroinflammatory syndrome caused (in humans) by the protozoa Plasmodium (P.) falciparum. Glial cell activation is one of the mechanisms that contributes to neuroinflammation in CM.

RESULT

By studying a mouse model of CM (caused by P. berghei ANKA), we describe that the induction of autophagy promoted p21-dependent senescence in astrocytes and that CXCL-10 was part of the senescence-associated secretory phenotype. Furthermore, p21 expression was observed in post-mortem brain and peripheral blood samples from patients with CM. Lastly, we found that the depletion of senescent astrocytes with senolytic drugs abrogated inflammation and protected mice from CM.

CONCLUSION

Our data provide evidence for a novel mechanism through which astrocytes could be involved in the neuropathophysiology of CM. p21 gene expression in blood cell and an elevated plasma CXCL-10 concentration could be valuable biomarkers of CM in humans. In the end, we believe senolytic drugs shall open up new avenues to develop newer treatment options.

Senescence-Targeted and NAD+-Dependent SIRT1-Activated Nanoplatform to Counteract Stem Cell Senescence for Promoting Aged Bone Regeneration

Age-related bone defects are a leading cause of disability and mortality in elderly individuals, and targeted therapy to delay the senescence of bone marrow-derived mesenchymal stem cells (MSCs) has emerged as a promising strategy to rejuvenate bone regeneration in aged scenarios. More specifically, activating the nicotinamide adenine dinucleotide (NAD+)-dependent sirtuin 1 (SIRT1) pathway is demonstrated to effectively counteract MSC senescence and thus promote osteogenesis. Herein, based on an inventively identified senescent MSC-specific surface marker Kremen1, a senescence-targeted and NAD+ dependent SIRT1 activated nanoplatform is fabricated with a dual delivery of resveratrol (RSV) (SIRT1 promoter) and nicotinamide riboside (NR, NAD+ precursor). This targeting nanoplatform exhibits a strong affinity for senescent MSCs through conjugation with anti-Kremen1 antibodies and enables specifically responsive release of NR and RSV in lysosomes via senescence-associated β-galactosidase-stimulated enzymatic hydrolysis of the hydrophilic chain. Furthermore, this nanoplatform performs well in promoting aged bone formation both in vitro and in vivo by boosting NAD+, activating SIRT1, and delaying MSC senescence. For the first time, a novel senescent MSC-specific surface marker is identified and aged bone repair is rejuvenated by delaying senescence of MSCs using an active targeting platform. This discovery opens up new insights for nanotherapeutics aimed at age-related diseases.

Microglia in brain aging: An overview of recent basic science and clinical research developments

Aging is characterized by progressive degeneration of tissues and organs, and it is positively associated with an increased mortality rate. The brain, as one of the most significantly affected organs, experiences age-related changes, including abnormal neuronal activity, dysfunctional calcium homeostasis, dysregulated mitochondrial function, and increased levels of reactive oxygen species. These changes collectively contribute to cognitive deterioration. Aging is also a key risk factor for neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease. For many years, neurodegenerative disease investigations have primarily focused on neurons, with less attention given to microglial cells. However, recently, microglial homeostasis has emerged as an important mediator in neurological disease pathogenesis. Here, we provide an overview of brain aging from the perspective of the microglia. In doing so, we present the current knowledge on the correlation between brain aging and the microglia, summarize recent progress of investigations about the microglia in normal aging, Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, and then discuss the correlation between the senescent microglia and the brain, which will culminate with a presentation of the molecular complexity involved in the microglia in brain aging with suggestions for healthy aging.

Emerging role of senescent microglia in brain aging-related neurodegenerative diseases

Brain aging is a recognized risk factor for neurodegenerative diseases like Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease), but the intricate interplay between brain aging and the pathogenesis of these conditions remains inadequately understood. Cellular senescence is considered to contribute to cellular dysfunction and inflammaging. According to the threshold theory of senescent cell accumulation, the vulnerability to neurodegenerative diseases is associated with the rates of senescent cell generation and clearance within the brain. Given the role of microglia in eliminating senescent cells, the accumulation of senescent microglia may lead to the acceleration of brain aging, contributing to inflammaging and increased vulnerability to neurodegenerative diseases. In this review, we propose the idea that the senescence of microglia, which is notably vulnerable to aging, could potentially serve as a central catalyst in the progression of neurodegenerative diseases. The senescent microglia are emerging as a promising target for mitigating neurodegenerative diseases.

Navigating the nexus among thigh volume, myokine, and immunocytes in older adults with sarcopenia: A retrospective analysis in a male cohort

BACKGROUND

This study investigated the association among thigh volume features, interleukin (IL)-6, and immunocytes in the context of the older people with sarcopenia.

MATERIALS AND METHODS

This study comprised a cohort of 437 older males diagnosed with sarcopenia, and their average age of 70.41 ± 4.86 years. This study involved conducting correlation and multiple linear regression analyses to investigate the connections between thigh volume, IL-6, and immunocytes.

RESULTS

Total thigh volume (TTV) showed positive connections with thigh muscle volume (TMV), natural killer (NK) cells, and CD8 + T cells. TMV had negative associations with thigh fat volume (TFV) and IL6 but displayed positive connections with other factors. IL-6 had adverse associations with all the other variables except for TFV. NK cells showed significant positive relations with all adaptive immune cells, though showing not TFV and IL-6. The CD3+ T cells, CD4+ T cells, CD8+ T cells, and CD19+ B cells exhibited positive correlations with each other including NK cells, though showing not TFV and IL-6. In the regression analysis, TMV exhibited significant positive effects on NK cells (β = 0.304), CD3+ T cells (β = 0.182), CD4+ T cells (β = 0.109), CD8+ T cells (β = 0.226), and CD19+ B cells (β = 0.197). On the other hand, IL-6 had significant negative effects on NK cells (β = -0.292), CD3+ T cells (β = -0.352), CD4+ T cells (β = -0.184), CD8+ T cells (β = -0.387), and CD19+ B cells (β = -0.366).

CONCLUSIONS

This study found that there existed a direct association among thigh muscle with sarcopenia, myokine, and immunocytes.

SIMPLE SUMMARY

The aging process involves the immune system playing a vital role in sarcopenia development, and it is thought that myokines released by skeletal myocytes. However, the exact relationship between TMV, myokines, and immunocytes in older male adults affected by sarcopenia remains unclear. This study found that myokines observed in sarcopenia showed a negative correlation with immunocytes, while muscle mass had a positive correlation with immunocytes. In the meantime, this research delved into the use of a regression model to examine how TMV and myokines individually contribute to explaining the presence of innate and adaptive immunocytes in older individuals with sarcopenia.

Determining the feasibility of characterising cellular senescence in human skeletal muscle and exploring associations with muscle morphology and physical function at different ages: findings from the MASS_Lifecourse Study

Cellular senescence may be associated with morphological changes in skeletal muscle and changes in physical function with age although there have been few human studies. We aimed to determine the feasibility of characterising cellular senescence in skeletal muscle and explored sex-specific associations between markers of cellular senescence, muscle morphology, and physical function in participants from the MASS_Lifecourse Study. Senescence markers (p16, TAF (Telomere-Associated DNA Damage Foci), HMGB1 (High Mobility Group Box 1), and Lamin B1) and morphological characteristics (fibre size, number, fibrosis, and centrally nucleated fibres) were assessed in muscle biopsies from 40 men and women (age range 47-84) using spatially-resolved methods (immunohistochemistry, immunofluorescence, and RNA and fluorescence in situ hybridisation). The associations between senescence, morphology, and physical function (muscle strength, mass, and physical performance) at different ages were explored. We found that most senescence markers and morphological characteristics were weakly associated with age in men but more strongly, although non-significantly, associated with age in women. Associations between senescence markers, morphology, and physical function were also stronger in women for HMGB1 and grip strength (r = 0.52); TAF, BMI, and muscle mass (r > 0.4); Lamin B1 and fibrosis (r =  - 0.5); fibre size and muscle mass (r ≥ 0.4); and gait speed (r =  - 0.5). However, these associations were non-significant. In conclusion, we have demonstrated that it is feasible to characterise cellular senescence in human skeletal muscle and to explore associations with morphology and physical function in women and men of different ages. The findings require replication in larger studies.

A homoeostatic switch causing glycerol-3-phosphate and phosphoethanolamine accumulation triggers senescence by rewiring lipid metabolism

Cellular senescence affects many physiological and pathological processes and is characterized by durable cell cycle arrest, an inflammatory secretory phenotype and metabolic reprogramming. Here, by using dynamic transcriptome and metabolome profiling in human fibroblasts with different subtypes of senescence, we show that a homoeostatic switch that results in glycerol-3-phosphate (G3P) and phosphoethanolamine (pEtN) accumulation links lipid metabolism to the senescence gene expression programme. Mechanistically, p53-dependent glycerol kinase activation and post-translational inactivation of phosphate cytidylyltransferase 2, ethanolamine regulate this metabolic switch, which promotes triglyceride accumulation in lipid droplets and induces the senescence gene expression programme. Conversely, G3P phosphatase and ethanolamine-phosphate phospho-lyase-based scavenging of G3P and pEtN acts in a senomorphic way by reducing G3P and pEtN accumulation. Collectively, our study ties G3P and pEtN accumulation to controlling lipid droplet biogenesis and phospholipid flux in senescent cells, providing a potential therapeutic avenue for targeting senescence and related pathophysiology.

The interaction between ageing and Alzheimer's disease: insights from the hallmarks of ageing

Ageing is a crucial risk factor for Alzheimer's disease (AD) and is characterised by systemic changes in both intracellular and extracellular microenvironments that affect the entire body instead of a single organ. Understanding the specific mechanisms underlying the role of ageing in disease development can facilitate the treatment of ageing-related diseases, such as AD. Signs of brain ageing have been observed in both AD patients and animal models. Alleviating the pathological changes caused by brain ageing can dramatically ameliorate the amyloid beta- and tau-induced neuropathological and memory impairments, indicating that ageing plays a crucial role in the pathophysiological process of AD. In this review, we summarize the impact of several age-related factors on AD and propose that preventing pathological changes caused by brain ageing is a promising strategy for improving cognitive health.

A review of the pathophysiological mechanisms of doxorubicin-induced cardiotoxicity and aging

The population of cancer survivors is rapidly increasing due to improving healthcare. However, cancer therapies often have long-term side effects. One example is cancer therapy-related cardiac dysfunction (CTRCD) caused by doxorubicin: up to 9% of the cancer patients treated with this drug develop heart failure at a later stage. In recent years, doxorubicin-induced cardiotoxicity has been associated with an accelerated aging phenotype and cellular senescence in the heart. In this review we explain the evidence of an accelerated aging phenotype in the doxorubicin-treated heart by comparing it to healthy aged hearts, and shed light on treatment strategies that are proposed in pre-clinical settings. We will discuss the accelerated aging phenotype and the impact it could have in the clinic and future research.

Macrophage migration inhibitory factor reversed senescent phenotype in human chondrocytes in vitro

BACKGROUND

The senescence of chondrocytes, which is closely linked to the development of osteoarthritis (OA), has been found to be influenced by the inflammatory environment of joint cavity. However, there remains a lack of comprehensive understanding regarding the specific mechanisms through which cytokine impacts chondrocytes senescence.

PURPOSE

To investigate the effects of MIF on the chondrocytes senescence and explore the underlying mechanism.

METHODS

Human cytokine array and ELISA were used for the level of MIF in synovium fluid. CCK-8 was used for chondrocytes viability. IF, WB, SA-β-gal staining and flow cytometry were used for the chondrogenic, apoptotic and senescent phenotype of chondrocytes.

RESULTS

The level of MIF was significantly increased in OA patients. MIF significantly reversed the senescent phenotype induced by LPS pretreatment in human chondrocytes. MIF significantly enhanced the expression of Col II, SOX9, and ACAN in LPS pre-treated human chondrocytes. Furthermore, MIF significantly inhibited the apoptosis of LPS-induced senescent chondrocytes.

CONCLUSION

Increased level of MIF in osteoarthritic joint cavity might effectively suppress the senescent phenotype and simultaneously improve the chondrogenic phenotype in chondrocytes, the underlying mechanism was likely to be independent of apoptosis.

Screening of Biomarkers Associated with Osteoarthritis Aging Genes and Immune Correlation Studies

Purpose

Osteoarthritis (OA) is a joint disease with a long and slow course, which is one of the major causes of disability in middle and old-aged people. This study was dedicated to excavating the cellular senescence-associated biomarkers of OA.

Methods

The Gene Expression Omnibus (GEO) database was searched and five datasets pertaining to OA were obtained. After removing the batch effect, the GSE55235, GSE55457, GSE82107, and GSE12021 datasets were integrated together for screening of the candidate genes by differential analysis and weighted gene co-expression network analysis (WGCNA). Next, those genes were further filtered by machine learning algorithms to obtain cellular senescence-associated biomarkers of OA. Subsequently, enrichment analyses based on those biomarkers were conducted, and we profiled the infiltration levels of 22 types immune cells with the ERSORT algorithm. A lncRNA-miRNA-mRNA regulatory and drug-gene network were constructed. Finally, we validated the senescence-associated biomarkers at both in vivo and in vitro levels.

Results

Five genes (BCL6, MCL1, SLC16A7, PIM1, and EPHA3) were authenticated as cellular senescence-associated biomarkers in OA. ROC curves demonstrated the reliable capacity of the five genes as a whole to discriminate OA samples from normal samples. The nomogram diagnostic model based on 5 genes proved to be a reliable predictor of OA. Single-gene GSEA results pointed to the involvement of the five biomarkers in immune-related pathways and oxidative phosphorylation in the development of OA. Immune infiltration analysis manifested that the five genes were significantly correlated with differential immune cells. Subsequently, a lncRNA-miRNA-mRNA network and gene-drug network containing were generated based on five cellular senescence-associated biomarkers in OA.

Conclusion

A foundation for understanding the pathophysiology of OA and new insights into OA diagnosis and treatment were provided by the identification of five genes, namely BCL6, MCL1, SLC16A7, PIM1, and EPHA3, as biomarkers associated with cellular senescence in OA.

Tumor cell senescence-induced macrophage CD73 expression is a critical metabolic immune checkpoint in the aging tumor microenvironment

Background: The role of senescent cells in the tumor microenvironment (TME) is usually bilateral, and diverse therapeutic approaches, such as radiotherapy and chemotherapy, can induce cellular senescence. Cellular interactions are widespread in the TME, and tumor cells reprogram immune cells metabolically by producing metabolites. However, how senescent cells remodel the metabolism of TME remains unclear. This study aimed to explore precise targets to enhance senescent cells-induced anti-tumor immunity from a metabolic perspective. Methods: The in vivo senescence model was induced by 8 Gy×3 radiotherapy or cisplatin chemotherapy, and the in vitro model was induced by 10 Gy-irradiation or cisplatin treatment. Metabonomic analysis and ELISA assay on tumor interstitial fluid were performed for metabolites screening. Marker expression and immune cell infiltration in the TME were analyzed by flow cytometry. Cell co-culture system and senescence-conditioned medium were used for crosstalk validation in vitro. RNA sequencing and rescue experiments were conducted for mechanism excavation. Immunofluorescence staining and single-cell transcriptome profiling analysis were performed for clinical validation. Results: We innovatively reveal the metabolic landscape of the senescent TME, characterized with the elevation of adenosine. It is attributed to the senescent tumor cell-induced CD73 upregulation of tumor-associated macrophages (TAMs). CD73 expression in TAMs is evoked by SASP-related pro-inflammatory cytokines, especially IL-6, and regulated by JAK/STAT3 pathway. Consistently, a positive correlation between tumor cells senescence and TAMs CD73 expression is identified in lung cancer clinical specimens and databases. Lastly, blocking CD73 in a senescent background suppresses tumors and activates CD8+ T cell-mediated antitumor immunity. Conclusions: TAMs expressed CD73 contributes significantly to the adenosine accumulation in the senescent TME, suggesting targeting CD73 is a novel synergistic anti-tumor strategy in the aging microenvironment.

Therapy-induced normal tissue damage promotes breast cancer metastasis

Disseminated tumor cells frequently exhibit a period of dormancy, rendering them chemotherapy insensitive; conversely, the systemic delivery of chemotherapies can result in normal tissue damage. Using multiple mouse and human breast cancer models, we demonstrate that prior chemotherapy administration enhances metastatic colonization and outgrowth. In vitro, chemotherapy-treated fibroblasts display a pro-tumorigenic senescence-associated secretory phenotype (SASP) and are effectively eliminated by targeting the anti-apoptotic protein BCL-xL. In vivo, chemotherapy treatment induces SASP expression in normal tissues; however, the accumulation of senescent cells is limited, and BCL-xL inhibitors are unable to reduce chemotherapy-enhanced metastasis. This likely reflects that chemotherapy-exposed stromal cells do not enter a BCL-xL-dependent phenotype or switch their dependency to other anti-apoptotic BCL-2 family members. This study highlights the role of the metastatic microenvironment in controlling outgrowth of disseminated tumor cells and the need to identify additional approaches to limit the pro-tumorigenic effects of therapy-induced normal tissue damage.

The Role of Sensory Nerves in Dental Pulp Homeostasis: Histological Changes and Cellular Consequences after Sensory Denervation

Homeostatic maintenance is essential for pulp function. Disrupting pulp homeostasis may lead to pulp degeneration, such as fibrosis and calcifications. Sensory nerves constitute a crucial component of the dental pulp. However, the precise involvement of sensory nerves in pulp homeostasis remains uncertain. In this study, we observed the short-term and long-term histological changes in the dental pulp after inferior alveolar nerve transection. Additionally, we cultured primary dental pulp cells (DPCs) from the innervated and denervated groups and compared indicators of cellular senescence and cellular function. The results revealed that pulp fibrosis occurred at 2 w after the operation. Furthermore, the pulp area, as well as the height and width of the pulp cavity, showed accelerated reductions after sensory denervation. Notably, the pulp area at 16 w after the operation was comparable to that of 56 w old rats. Sensory denervation induced excessive extracellular matrix (ECM) deposition and increased predisposition to mineralization. Furthermore, sensory denervation promoted the senescence of DPCs. Denervated DPCs exhibited decelerated cell proliferation, arrest in the G2/M phase of the cell cycle, imbalance in the synthesis and degradation of ECM, and enhanced mineralization. These findings indicate that sensory nerves play an essential role in pulp homeostasis maintenance and dental pulp cell fate decisions, which may provide novel insights into the prevention of pulp degeneration.

Design and optimization of piperlongumine analogs as potent senolytics

Selective removal of senescent cells (SnCs) offers a promising therapeutic strategy to treat chronic and age-related diseases. Our prior investigations led to the discovery of piperlongumine (PL) and its derivatives as senolytic agents. In this study, our medicinal chemistry campaign on both the α,β-unsaturated δ-valerolactam ring and the phenyl ring of PL culminated in the identification of compound 24, which exhibited an impressive 50-fold enhancement in senolytic activity against senescent WI-38 fibroblasts compared to PL.

Detection and Elimination of Senescent Cells with a Self-Assembled Senescence-Associated β-Galactosidase-Activatable Nanophotosensitizer

Senescent cells have become an important therapeutic target for many age-related dysfunctions and diseases. We report herein a novel nanophotosensitizing system that is responsive to the senescence-associated β-galactosidase (β-gal) for selective detection and elimination of these cells. It involves a dimeric zinc(II) phthalocyanine linked to a β-galactose unit via a self-immolative linker. This compound can self-assemble in aqueous media, forming stable nanoscale particles in which the phthalocyanine units are stacked and self-quenched for fluorescence emission and singlet oxygen production. Upon internalization into senescent HeLa cells, these nanoparticles interact with the overproduced senescence-associated β-gal inside the cells to trigger the disassembly process through enzymatic cleavage of the glycosidic bonds, followed by self-immolation to release the photoactive monomeric phthalocyanine units. These senescent cells can then be lit up with fluorescence and eliminated through the photodynamic action upon light irradiation with a half-maximal inhibitory concentration of 0.06 μM.

Role of maraviroc and/or rapamycin in the liver of IL10 KO mice with frailty syndrome

Cellular senescence and low-grade inflammation favor the acceleration of aging. The liver is an essential metabolic organ because changes related to its function are related to age-related diseases. The objective of this study was to evaluate the effects of maraviroc (MVC) and/or rapamycin (RAPA) on liver tissue in an experimental model of frailty syndrome in mice, since MVC and RAPA are two molecules able to decrease CCR5 expression, which is overexpressed in patients with frailty. Methods: Eighty male homozygous IL10KO mice were randomly assigned to one of 4 groups (n = 20): i) IL10KO group; ii) MVC group, iii) RAPA group, and iv) MVC-RAPA group. Liver samples were analyzed. Gene expression quantification and western blotting were also performed. The proinflammatory cytokines IL-6 and IL-18 were decreased in MVC and MVC/RAPA groups, IL-12 was decreased in RAPA and MVC/RAPA groups and TNF-α was decreased in all therapeutic groups. P21 was decreased in RAPA and MVC/RAPA groups, Galactosidase beta-1, was also significantly reduced in all therapeutic groups, as were NF-kB1, NF-kB2 and STAT3. In all groups, mTOR and CCL5 were significantly reduced. CCR5 expression was decreased in the MVC and MVC/RAPA groups. Conclusion: MVC and RAPA may protect against some factors involved in liver aging. More studies will be necessary to verify their clinical applications.

Recent Advancement in Elimination Strategies and Potential Rejuvenation Targets of Senescence

Cellular senescence is a state of exiting the cell cycle, resisting apoptosis, and changing phenotype. Senescent cells (SCs) can be identified by large, distorted morphology and irreversible inability to replicate. In early development, senescence has beneficial roles like tissue patterning and wound healing, where SCs are cleared by the immune system. However, there is a steep rise in SC number as organisms age. The issue with SC accumulation stems from the loss of cellular function, alterations of the microenvironment, and secretions of pro-inflammatory molecules, consisting of cytokines, chemokines, matrix metalloproteinases (MMPs), interleukins, and extracellular matrix (ECM)-associated molecules. This secreted cocktail is referred to as the senescence-associated secretory phenotype (SASP), a hallmark of cellular senescence. The SASP promotes inflammation and displays a bystander effect where paracrine signaling turns proliferating cells into senescent states. To alleviate age-associated diseases, researchers have developed novel methods and techniques to selectively eliminate SCs in aged individuals. Although studies demonstrated that selectively killing SCs improves age-related disorders, there are drawbacks to SC removal. Considering favorable aspects of senescence in the body, this paper reviews recent advancements in elimination strategies and potential rejuvenation targets of senescence to bring researchers in the field up to date.

Branched-Chain Amino Acid Accumulation Fuels the Senescence-Associated Secretory Phenotype

The essential branched-chain amino acids (BCAAs) leucine, isoleucine, and valine play critical roles in protein synthesis and energy metabolism. Despite their widespread use as nutritional supplements, BCAAs' full effects on mammalian physiology remain uncertain due to the complexities of BCAA metabolic regulation. Here a novel mechanism linking intrinsic alterations in BCAA metabolism is identified to cellular senescence and the senescence-associated secretory phenotype (SASP), both of which contribute to organismal aging and inflammation-related diseases. Altered BCAA metabolism driving the SASP is mediated by robust activation of the BCAA transporters Solute Carrier Family 6 Members 14 and 15 as well as downregulation of the catabolic enzyme BCAA transaminase 1 during onset of cellular senescence, leading to highly elevated intracellular BCAA levels in senescent cells. This, in turn, activates the mammalian target of rapamycin complex 1 (mTORC1) to establish the full SASP program. Transgenic Drosophila models further indicate that orthologous BCAA regulators are involved in the induction of cellular senescence and age-related phenotypes in flies, suggesting evolutionary conservation of this metabolic pathway during aging. Finally, experimentally blocking BCAA accumulation attenuates the inflammatory response in a mouse senescence model, highlighting the therapeutic potential of modulating BCAA metabolism for the treatment of age-related and inflammatory diseases.

Nutrition, Immunity and Aging: Current Scenario and Future Perspectives in Neurodegenerative Diseases

Aging is a gradual decline of physiological function and tissue homeostasis and, in many instances, is related to increased (neuro)-degeneration, together with inflammation, becoming one of the most important risks for developing neurodegenerative diseases. Certain individual nutrients or foods in combination may counteract aging and associated neurodegenerative diseases by promoting a balance between the pro- and anti-inflammatory responses. Thus, nutrition could represent a powerful modulator of this fine balance, other than a modifiable risk factor to contrast inflammaging. This narrative review explores from a broad perspective the impact of nutrition on the hallmarks of aging and inflammation in Alzheimer's disease (AD), Parkinson's disease (PD) and Amyotrophic Lateral Sclerosis Syndrome (ALS), starting from nutrients up to single foods and complex dietary patterns.

Polyphenols and Diets as Current and Potential Nutrition Senotherapeutics in Alzheimer's Disease: Findings from Clinical Trials

Cellular senescence, a hallmark of aging, plays an important role in age-related conditions among older adults. Targeting senescent cells and its phenotype may provide a promising strategy to delay the onset or progression of Alzheimer's disease (AD). In this review article, we investigated efficacy and safety of nutrition senotherapy in AD, with a focus on the role of polyphenols as current and potential nutrition senotherapeutic agents, as well as relevant dietary patterns. Promising results with neuroprotective effects of senotherapeutic agents such as quercetin, resveratrol, Epigallocatechin-gallate, curcumin and fisetin were reported from preclinical studies. However, in-human trials remain limited, and findings were inconclusive. In future, nutrition senotherapeutic agents should be studied both individually and within dietary patterns, through the perspective of cellular senescence and AD. Further studies are warranted to investigate bioavailability, dosing regimen, long term effects of nutrition senotherapy and provide better understanding of the underlying mechanisms. Collaboration between researchers needs to be established, and methodological limitations of current studies should be addressed.

Protocatechuic aldehyde attenuates chondrocyte senescence via the regulation of PTEN-induced kinase 1/Parkin-mediated mitochondrial autophagy

This study aimed to investigate whether the beneficial effects of PCA on chondrocyte senescence are mediated through the regulation of mitophagy. Chondrocyte senescence plays a significant role in the development and progression of knee osteoarthritis (OA). The compound protocatechuic aldehyde (PCA), which is abundant in the roots of Salvia miltiorrhiza, has been reported to have antioxidant properties and the ability to protect against cellular senescence. To achieve this goal, a destabilization of the medial meniscus (DMM)-induced mouse OA model and a lipopolysaccharide (LPS)-induced chondrocyte senescence model were used, in combination with PINK1 gene knockdown or overexpression. After treatment with PCA, cellular senescence was assessed using Senescence-Associated β-Galactosidase (SA-β-Gal) staining, DNA damage was evaluated using Hosphorylation of the Ser-139 (γH2AX) staining, reactive oxygen species (ROS) levels were measured using Dichlorodihydrofluorescein diacetate (DCFH-DA) staining, mitochondrial membrane potential was determined using a 5,5',6,6'-TETRACHLORO-1,1',3,3'-*. TETRAETHYBENZIMIDA (JC-1) kit, and mitochondrial autophagy was examined using Mitophagy staining. Western blot analysis was also performed to detect changes in senescence-related proteins, PINK1/Parkin pathway proteins, and mitophagy-related proteins. Our results demonstrated that PCA effectively reduced chondrocyte senescence, increased the mitochondrial membrane potential, facilitated mitochondrial autophagy, and upregulated the PINK1/Parkin pathway. Furthermore, silencing PINK1 weakened the protective effects of PCA, whereas PINK1 overexpression enhanced the effects of PCA on LPS-induced chondrocytes. PCA attenuates chondrocyte senescence by regulating PINK1/Parkin-mediated mitochondrial autophagy, ultimately reducing cartilage degeneration.

Delaying Brain Aging or Decreasing Tau Levels as Strategies to Prevent Alzheimer's Disease: In Memoriam of Mark A. Smith

Aging is the main risk for neurodegenerative disorders like Alzheimer's disease. In this short review, I will comment on how delaying brain aging through the addition of Yamanaka Factors or small compounds that bind to the folate receptor alpha, which promote the expression of the Yamanaka Factors or by the decrease tau levels in brain cells from older subjects could serve as strategies to prevent Alzheimer's disease.

Regulation of cellular senescence by innate immunity

During the COVID-19 pandemic, the interplay between the processes of immunity and senescence is drawing more and more intensive attention. SARS-CoV-2 infection induces senescence in lung cells, failure to clear infected cells and increased presence of inflammatory factors could lead to a cytokine storm and acute respiratory disease syndrome (ARDS), which together with aging and age-associated disease lead to 70% of COVID-19-related deaths. Studies on how senescence initiates upon viral infection and how to restrict excessive accumulation of senescent cells to avoid harmful inflammation are crucially important. Senescence can induce innate immune signaling, and innate immunity can engage cell senescence. Here, we mainly review the innate immune pathways, such as cGAS-STING, TLRs, NF-κB, and NLRP3 inflammasome, participating in the senescence process. In these pathways, IFN-I and inflammatory factors play key roles. At the end of the review, we propose the strategies by which we can improve the immune function and reduce inflammation based on these findings.

scResolve: Recovering single cell expression profiles from multi-cellular spatial transcriptomics

Many popular spatial transcriptomics techniques lack single-cell resolution. Instead, these methods measure the collective gene expression for each location from a mixture of cells, potentially containing multiple cell types. Here, we developed scResolve, a method for recovering single-cell expression profiles from spatial transcriptomics measurements at multi-cellular resolution. scResolve accurately restores expression profiles of individual cells at their locations, which is unattainable from cell type deconvolution. Applications of scResolve on human breast cancer data and human lung disease data demonstrate that scResolve enables cell type-specific differential gene expression analysis between different tissue contexts and accurate identification of rare cell populations. The spatially resolved cellular-level expression profiles obtained through scResolve facilitate more flexible and precise spatial analysis that complements raw multi-cellular level analysis.

The effect of metformin on senescence of T lymphocytes

BACKGROUND

Immunosenescence occurs as people age, leading to an increased incidence of age-related diseases. The number of senescent T cells also rises with age. T cell senescence and immune response dysfunction can result in a decline in immune function, especially in anti-tumor immune responses. Metformin has been shown to have various beneficial effects on health, such as lowering blood sugar levels, reducing the risk of cancer development, and slowing down the aging process. However, the immunomodulatory effects of metformin on senescent T cells still need to be investigated.

METHODS

PBMCs isolation from different age population (n = 88); Flow Cytometry is applied to determine the phenotypic characterization of senescent T lymphocytes; intracellular staining is applied to determine the function of senescent T cells; Enzyme-Linked Immunosorbent Assay (ELISA) is employed to test the telomerase concentration. The RNA-seq analysis of gene expression associated with T cell senescence.

RESULTS

The middle-aged group had the highest proportion of senescent T cells. We found that metformin could decrease the number of CD8 + senescent T cells. Metformin affects the secretion of SASP, inhibiting the secretion of IFN-γ in CD8 + senescent T cells. Furthermore, metformin treatment restrained the production of the proinflammatory cytokine IL-6 in lymphocytes. Metformin had minimal effects on Granzyme B secretion in senescent T cells, but it promoted the production of TNF-α in senescent T cells. Additionally, metformin increased the concentration of telomerase and the frequency of undifferentiated T cells. The results of RNA-seq showed that metformin promoted the expression of genes related to stemness and telomerase activity, while inhibiting the expression of DNA damage-associated genes.

CONCLUSION

Our findings reveal that metformin could inhibit T cell senescence in terms of cell number, effector function, telomerase content and gene expression in middle-aged individuals, which may serve as a promising approach for preventing age-related diseases in this population.

Molecular Mechanisms and the Interplay of Important Chronic Obstructive Pulmonary Disease Biomarkers Reveals Novel Therapeutic Targets

Chronic Obstructive Pulmonary Disease (COPD) is a progressive, age-dependent, and unmet chronic inflammatory disease of the peripheral airways, leading to difficulty in exhalation. Several biomarkers have been tested in general towards the resolution for a long time, but no apparent success was achieved. Ongoing therapies of COPD have only symptomatic relief but no cure. Reactive oxygen species (ROS) are highly reactive species which include oxygen radicals and nonradical derivatives, and are the prominent players in COPD. They are produced as natural byproducts of cellular metabolism, but their levels can vary due to exposure to indoor air pollution, occupational pollution, and environmental pollutants such as cigarette smoke. In COPD, the lungs are continuously exposed to high levels of ROS thus leading to oxidative stress. ROS can cause damage to cells, proteins, lipids, and DNA which further contributes to the chronic inflammation in COPD and exacerbates the disease condition. Excessive ROS production can overwhelm cellular antioxidant systems and act as signaling molecules that regulate cellular processes, including antioxidant defense mechanisms involving glutathione and sirtuins which further leads to cellular apoptosis, cellular senescence, inflammation, and sarcopenia. In this review paper, we focused on COPD from different perspectives including potential markers and different cellular processes such as apoptosis, cellular senescence, inflammation, sirtuins, and sarcopenia, and tried to connect the dots between them so that novel therapeutic strategies to evaluate and target the possible underlying mechanisms in COPD could be explored.

The Role of Cellular Senescence in Cyclophosphamide-Induced Primary Ovarian Insufficiency

Young female cancer patients can develop chemotherapy-induced primary ovarian insufficiency (POI). Cyclophosphamide (Cy) is one of the most widely used chemotherapies and has the highest risk of damaging the ovaries. Recent studies elucidated the pivotal roles of cellular senescence, which is characterized by permanent cell growth arrest, in the pathologies of various diseases. Moreover, several promising senolytics, including dasatinib and quercetin (DQ), which remove senescent cells, are being developed. In the present study, we investigated whether cellular senescence is involved in Cy-induced POI and whether DQ treatment rescues Cy-induced ovarian damage. Expression of the cellular senescence markers p16, p21, p53, and γH2AX was upregulated in granulosa cells of POI mice and in human granulosa cells treated with Cy, which was abrogated by DQ treatment. The administration of Cy decreased the numbers of primordial and primary follicles, with a concomitant increase in the ratio of growing to dormant follicles, which was partially rescued by DQ. Moreover, DQ treatment significantly improved the response to ovulation induction and fertility in POI mice by extending reproductive life. Thus, cellular senescence plays critical roles in Cy-induced POI, and targeting senescent cells with senolytics, such as DQ, might be a promising strategy to protect against Cy-induced ovarian damage.

Senescence-associated secretory phenotypes in mesenchymal cells contribute to cytotoxic immune response in oral lichen planus

Oral lichen planus is a chronic inflammatory condition that adversely affects the oral mucosa; however, its etiology remains elusive. Consequently, therapeutic interventions for oral lichen planus are limited to symptomatic management. This study provides evidence of the accumulation of senescent mesenchymal cells, CD8 + T cells, and natural killer cells in patients with oral lichen planus. We profiled the patients' tissues using the National Center for Biotechnology Information Gene Expression Omnibus database and found that senescence-related genes were upregulated in these tissues by gene set enrichment analysis. Immunohistochemical analysis showed increased senescent mesenchymal cells in the subepithelial layer of patients with oral lichen planus. Single-cell RNA-seq data retrieved from the Gene Expression Omnibus database of patients with oral lichen planus revealed that mesenchymal cells were marked by the upregulation of senescence-related genes. Cell-cell communication analysis using CellChat showed that senescent mesenchymal cells significantly influenced CD8 + T cells and natural killer cells via CXCL12-CXCR4 signaling, which is known to activate and recruit CD8 + T cells and NK cells. Finally, in vitro assays demonstrated that the secretion of senescence-associated factors from mesenchymal cells stimulated the activation of T cells and natural killer cells and promoted epithelial cell senescence and cytotoxicity. These findings suggest that the accumulation of mesenchymal cells with senescence-associated secretory phenotype may be a key driver of oral lichen planus pathogenesis.

Traditional herbs: mechanisms to combat cellular senescence

Cellular senescence plays a very important role in the ageing of organisms and age-related diseases that increase with age, a process that involves physiological, structural, biochemical and molecular changes in cells. In recent years, it has been found that the active ingredients of herbs and their natural products can prevent and control cellular senescence by affecting telomerase activity, oxidative stress response, autophagy, mitochondrial disorders, DNA damage, inflammatory response, metabolism, intestinal flora, and other factors. In this paper, we review the research information on the prevention and control of cellular senescence in Chinese herbal medicine through computer searches of PubMed, Web of Science, Science Direct and CNKI databases.

Enzyme-responsive nanospheres target senescent cells for diabetic wound healing by employing chemodynamic therapy

Evidence indicates that prolonged low-level inflammation and elevated-glucose-induced oxidative stress in diabetic wounds can accelerate senescence. The accumulation of senescent cells, in turn, inhibits cellular proliferation and migration, aggravating the inflammatory response and oxidative stress, ultimately impeding wound healing. In this study, we exploited the heightened lysosomal β-galactosidase activity detected in senescent cells to develop an innovative drug delivery system by encapsulating Fe3O4 with galactose-modified poly (lactic-co-glycolic acid) (PLGA) (F@GP). We found that F@GP can selectively release Fe3O4 into senescent cells, inducing ferroptosis via the Fenton reaction in the presence of elevated intracellular H2O2 levels. This showed that F@GP administration can serve as a chemodynamic therapy to eliminate senescent cells and promote cell proliferation. Furthermore, the F@GP drug delivery system gradually released iron ions into the diabetic wound tissues, enhancing the attenuation of cellular senescence, stimulating cell proliferation, promoting re-epithelialization, and accelerating the healing of diabetic wounds in mice. Our groundbreaking approach unveiled the specific targeting of senescence by F@GP, demonstrating its profound effect on promoting the healing of diabetic wounds. This discovery underscores the therapeutic potential of F@GP in effectively addressing challenging cases of wound repair. STATEMENT OF SIGNIFICANCE: The development of galactose-modified PLGA nanoparticles loaded with Fe3O4 (F@GP) represents a significant therapeutic approach for the treatment of diabetic wounds. These nanoparticles exhibit remarkable potential in selectively targeting senescent cells, which accumulate in diabetic wound tissue, through an enzyme-responsive mechanism. By employing chemodynamic therapy, F@GP nanoparticles effectively eliminate senescent cells by releasing iron ions that mediate the Fenton reaction. This targeted approach holds great promise for promoting diabetic wound healing by selectively eliminating senescent cells, which play a crucial role in impairing the wound healing process. The innovative utilization of F@GP nanoparticles as a therapeutic intervention offers a novel and potentially transformative strategy for addressing the challenges associated with diabetic wound healing.

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.

Piezo1 transforms mechanical stress into pro senescence signals and promotes osteoarthritis severity

Osteoarthritis (OA) is a prevalent disease among elderly people and is often characterized by chronic joint pain and dysfunction. Recently, growing evidence of chondrocyte senescence in the pathogenesis of OA has been found, and targeting senescence has started to be recognized as a therapeutic approach for OA. Piezo1, a mechanosensitive Ca2+ channel, has been reported to be harmful in sensing abnormal mechanical overloading and leading to chondrocyte apoptosis. However, whether Piezo1 can transform mechanical signals into senescence signals has rarely been reported. In this study, we found that severe OA cartilage expressed more Piezo1 and the senescence markers p16 and p21. 24 h of periodic mechanical stress induced chondrocyte senescence in vitro. In addition, we demonstrated the pivotal role of Piezo1 in OA chondrocyte senescence induced by mechanical stress. Piezo1 sensed mechanical stress and promoted chondrocyte senescence via its Ca2+ channel ability. Moreover, Piezo1 promoted SASP factors production under mechanical stress, particularly in IL-6 and IL-1β. p38MAPK and NF-κB activation were two key pathways that responded to Piezo1 activation and promoted IL-6 and IL-1β production, respectively. Collectively, our study revealed a connection between abnormal mechanical stress and chondrocyte senescence, which was mediated by Piezo1.

Status of Research on Sestrin2 and Prospects for its Application in Therapeutic Strategies Targeting Myocardial Aging

Cardiac aging is accompanied by changes in the heart at the cellular and molecular levels, leading to alterations in cardiac structure and function. Given today's increasingly aging population, the decline in cardiac function caused by cardiac aging has a significant impact on quality of life. Antiaging therapies to slow the aging process and attenuate changes in cardiac structure and function have become an important research topic. Treatment with drugs, including metformin, spermidine, rapamycin, resveratrol, astaxanthin, Huolisu oral liquid, and sulforaphane, has been demonstrated be effective in delaying cardiac aging by stimulating autophagy, delaying ventricular remodeling, and reducing oxidative stress and the inflammatory response. Furthermore, caloric restriction has been shown to play an important role in delaying aging of the heart. Many studies in cardiac aging and cardiac aging-related models have demonstrated that Sestrin2 has antioxidant and anti-inflammatory effects, stimulates autophagy, delays aging, regulates mitochondrial function, and inhibits myocardial remodeling by regulation of relevant signaling pathways. Therefore, Sestrin2 is likely to become an important target for antimyocardial aging therapy.

Mechanisms underlying retardation of aging by dietary energy restriction

Moderate restriction of dietary energy intake, referred to here as dietary restriction (DR), delays aging and extends lifespan in experimental animals compared with a diet of ad libitum feeding (AL) control animals. Basic knowledge of the mechanisms underlying the effects of DR could be applicable to extending the healthspan in humans. This review highlights the importance of forkhead box O (FoxO) transcription factors downstream of the growth hormone-insulin-like growth factor 1 signaling in the effects of DR. Our lifespan studies in mice with heterozygous Foxo1 or Foxo3 gene knockout indicated differential roles of FoxO1 and FoxO3 in the tumor-inhibiting and life-extending effects of DR. Subsequent studies suggested a critical role of FoxO3 in metabolic and mitochondrial bioenergetic adaptation to DR. Our studies also verified hypothalamic neuropeptide Y (Npy) as a vital neuropeptide showing pleiotropic and sexually dimorphic effects for extending the healthspan in the context of nutritional availability. Npy was necessary for DR to exert its effects in male and female mice; meanwhile, under AL conditions, the loss of Npy prevented obesity and insulin resistance only in female mice. Overnutrition disrupts FoxO- and Npy-associated metabolic and mitochondrial bioenergetic adaptive processes, causing the acceleration of aging and related diseases.

Tissue Engineering of JAK Inhibitor-Loaded Hierarchically Biomimetic Nanostructural Scaffold Targeting Cellular Senescence for Aged Bone Defect Repair and Bone Remolding

Cell senescence or apoptosis contributes to self-failure and functional loss in specialized cells, leading to incapacity of the body to repair specific damages. Senescent bone marrow mesenchymal stem cells (BMSCs) lose their proliferative abilities and secrete senescence-associated secretory phenotype (SASP), hindering their participation in bone defect repair. Hence, the effective suppression of cell senescence is crucial to restore the self-repair capacity of body to treat bone defects. Since the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway is associated with SASP secretion, herein, a new strategy is proposed to inhibit this pathway to suppress SASP secretion and enhance osteoblast activity based on a novel hierarchically biomimetic nanostructural electrospun scaffold with JAK inhibitors (JAKi, Ruxolitinib) loaded. As validated by in vitro and in vivo experiments, the JAKi loaded scaffold reduces SASP expression effectively and alleviates senescent cell burden, creating a pro-regeneration microenvironment that enhances osteoblast function and mineralization activity as well as rejuvenating the bone repair capacity. These findings offer insights into the regulatory role of cellular senescence in bone aging and provide a new and effective strategy to treat age-related bone defects by delivery of JAKi to locally aging bone defect sites.

Mesenchymal stem cells with p38 mitogen-activated protein kinase interference ameliorate mouse ischemic stroke

Mesenchymal stem cells (MSCs) have been widely used in the treatment of ischemic stroke. However, factors such as high glucose, oxidative stress, and aging can lead to the reduced function of donor MSCs. The p38 mitogen-activated protein kinase (MAPK) signaling pathway is associated with various functions, such as cell proliferation, apoptosis, senescence, differentiation, and paracrine secretion. This study examined the hypothesis that the downregulation of p38 MAPK expression in MSCs improves the prognosis of mice with ischemic stroke. Lentiviral vector-mediated short hairpin RNA (shRNA) was constructed to downregulate the expression level of p38 MAPK in mouse bone marrow-derived MSCs. The growth cycle, apoptosis, and senescence of MSCs after infection were examined. A mouse model of ischemic stroke was constructed. After MSC transplantation, the recovery of neurological function in the mice was evaluated. Lentivirus-mediated shRNA significantly downregulated the mRNA and protein expression levels of p38 MAPK. The senescence of MSCs in the p38 MAPK downregulation group was significantly reduced, but the growth cycle and apoptosis did not significantly change. Compared with the control group, the infarct volume was reduced, and the neurological function and the axonal remodeling were improved in mice with ischemic stroke after transplantation of MSCs with downregulated p38 MAPK. Immunohistochemistry confirmed that in the p38 MAPK downregulation group, apoptotic cells were reduced, and the number of neuronal precursors and the formation of white matter myelin were increased. In conclusion, downregulation of p38 MAPK expression in MSCs improves the therapeutic effect in mice with ischemic stroke, an effect that may be related to a reduction in MSC senescence. This method is expected to improve the efficacy of MSCs in patients, especially in patients with underlying diseases such as diabetes, thus providing a basis for clinical individualized treatment for cerebral infarction.

Depletion of preexisting B-cell lymphoma 2-expressing senescent cells before vaccination impacts antigen-specific antitumor immune responses in old mice

The age-related decline in immunity reduces the effectiveness of vaccines in older adults. Immunosenescence is associated with chronic, low-grade inflammation, and the accumulation of senescent cells. The latter express Bcl-2 family members (providing resistance to cell death) and exhibit a pro-inflammatory, senescence-associated secretory phenotype (SASP). Preexisting senescent cells cause many aging-related disorders and therapeutic means of eliminating these cells have recently gained attention. The potential consequences of senescent cell removal on vaccine efficacy in older individuals are still ignored. We used the Bcl-2 family inhibitor ABT-263 to investigate the effects of pre-vaccination senolysis on immune responses in old mice. Two different ovalbumin (OVA)-containing vaccines (containing a saponin-based or a CpG oligodeoxynucleotide adjuvant) were tested. ABT-263 depleted senescent cells (apoptosis) and ablated the basal and lipopolysaccharide-induced production of SASP-related factors in old mice. Depletion of senescent cells prior to vaccination (prime/boost) had little effect on OVA-specific antibody and T-cell responses (slightly reduced and augmented, respectively). We then used a preclinical melanoma model to test the antitumor potential of senolysis before vaccination (prime with the vaccine and OVA boost by tumor cells). Surprisingly, ABT-263 treatment abrogated the vaccine's ability to protect against B16 melanoma growth in old animals, an effect associated with reduced antigen-specific T-cell responses. Some, but not all, of the effects were age-specific, which suggests that preexisting senescent cells were partly involved. Hence, depletion of senescent cells modifies immune responses to vaccines in some settings and caution should be taken when incorporating senolytics into vaccine-based cancer therapies.

The protective effects of Phoenixin-20 in tumor necrosis factor α (TNF-α)-induced cell senescence of rheumatoid arthritis fibroblast-like synoviocytes (FLS)

Rheumatoid arthritis (RA) is an age-related joint destruction disease that markedly impacts the normal life of patients. Currently, the clinical treatment strategies are far from satisfactory with severe side effects. Cellular senescence of fibroblast-like synoviocytes (FLS) has been reported to be involved in the pathological process of arthritis, which may provide an important research direction for RA treatment. Phoenixin-20 (PNX-20) is a peptide targeting G-protein-coupled receptor 173 (GPR173) with promising anti-inflammatory properties. Our study will probe into the function of PNX-20 on tumor necrosis factor α (TNF-α)- induced rheumatoid arthritis (RA) FLS cell senescence to provide a theoretical basis for treating RA with PNX-20. RA-FLSs were handled with 10 ng/mL TNF-α, followed by introducing Phoenixin-20 (10, 20 nM) or not for 7 days. Enhanced release of inflammatory cytokines, increased proportion of senescence-associated β-galactosidase (SA-β-gal) positive cells, and declined telomerase activity were all observed in TNF-α-treated RA-FLSs, accompanied by a noticeable decline in the p21 and p53 level, which were notably reversed by 10 and 20 nM PNX-20. Furthermore, the increased signal transducer and activator of transcription 6 (STAT6) level observed in TNF-α-treated RA-FLSs were signally repressed by PNX-20. Moreover, the impact of PNX-20 on TNF-α-induced cellular senescence in RA-FLSs was abrogated by the overexpression of STAT6. Collectively, PNX-20 protected the TNF-α-induced cell senescence in RA-FLSs by downregulating STAT6. Based on these findings, we speculate that PNX-20 might be a promising agent for the treatment of RA.

Local H2 release remodels senescence microenvironment for improved repair of injured bone

The senescence microenvironment, which causes persistent inflammation and loss of intrinsic regenerative abilities, is a main obstacle to effective tissue repair in elderly individuals. In this work, we find that local H2 supply can remodel the senescence microenvironment by anti-inflammation and anti-senescence effects in various senescent cells from skeletally mature bone. We construct a H2-releasing scaffold which can release high-dosage H2 (911 mL/g, up to 1 week) by electrospraying polyhydroxyalkanoate-encapsulated CaSi2 nanoparticles onto mesoporous bioactive glass. We demonstrate efficient remodeling of the microenvironment and enhanced repair of critical-size bone defects in an aged mouse model. Mechanistically, we reveal that local H2 release alters the microenvironment from pro-inflammation to anti-inflammation by senescent macrophages repolarization and secretome change. We also show that H2 alleviates the progression of aging/injury-superposed senescence, facilitates the recruitment of endogenous cells and the preservation of their regeneration capability, thereby creating a pro-regenerative microenvironment able to support bone defect regeneration.

Proceedings of the inaugural Dark Genome Symposium: November 2022

In November 2022 the first Dark Genome Symposium was held in Boston, USA. The meeting was hosted by Rome Therapeutics and Enara Bio, two biotechnology companies working on translating our growing understanding of this vast genetic landscape into therapies for human disease. The spirit and ambition of the meeting was one of shared knowledge, looking to strengthen the network of researchers engaged in the field. The meeting opened with a welcome from Rosana Kapeller and Kevin Pojasek followed by a first session of field defining talks from key academics in the space. A series of panels, bringing together academia and industry views, were then convened covering a wide range of pertinent topics. Finally, Richard Young and David Ting gave their views on the future direction and promise for patient impact inherent in the growing understanding of the Dark Genome.

Microgravity Effects and Aging Physiology: Similar Changes or Common Mechanisms?

Despite the use of countermeasures (including intense physical activity), cosmonauts and astronauts develop muscle atony and atrophy, cardiovascular system failure, osteopenia, etc. All these changes, reminiscent of age-related physiological changes, occur in a healthy person in microgravity quite quickly - within a few months. Adaptation to the lost of gravity leads to the symptoms of aging, which are compensated after returning to Earth. The prospect of interplanetary flights raises the question of gravity thresholds, below which the main physiological systems will decrease their functional potential, similar to aging, and affect life expectancy. An important role in the aging process belongs to the body's cellular reserve - progenitor cells, which are involved in physiological remodeling and regenerative/reparative processes of all physiological systems. With age, progenitor cell count and their regenerative potential decreases. Moreover, their paracrine profile becomes pro-inflammatory during replicative senescence, disrupting tissue homeostasis. Mesenchymal stem/stromal cells (MSCs) are mechanosensitive, and therefore deprivation of gravitational stimulus causes serious changes in their functional status. The review compares the cellular effects of microgravity and changes developing in senescent cells, including stromal precursors.

Application and prospect of the therapeutic strategy of inhibiting cellular senescence combined with pro-regenerative biomaterials in regenerative medicine

Complete regeneration of damaged tissues/organs has always been the ultimate challenge in regenerative medicine. Aging has long been considered the basis of age-related diseases, as senescent cells gradually accumulate in tissues with increasing age, tissues exhibit aging and normal physiological functions are inhibited. In recent years, in damaged tissues, scholars have found that the number of cells with features of cellular senescence continues to increase over time. The accumulation of senescent cells severely hinders the healing of damaged tissues. Furthermore, by clearing senescent cells or inhibiting the aging microenvironment, damaged tissues regained their original regenerative and repair capabilities. On the other hand, various biomaterials have been proved to have good biocompatibility and can effectively support cell regeneration after injury. Combining the two solutions, inhibiting the cellular senescence in damaged tissues and establishing a pro-regenerative environment through biomaterial technology gradually reveals a new, unexpected treatment strategy applied to the field of regenerative medicine. In this review, we first elucidate the main characteristics of senescent cells from morphological, functional and molecular levels, and discuss in detail the process of accumulation of senescent cells in tissues. Then, we will explore in depth how the accumulation of senescent cells after damage affects tissue repair and regeneration at different stages. Finally, we will turn to how to promote tissue regeneration and repair in the field of regenerative medicine by inhibiting cellular senescence combined with biomaterial technology. Our goal is to understand the relationship between cellular senescence and tissue regeneration through this new perspective, and provide valuable references for the development of new therapeutic strategies in the future.

Gcn5- and Bre1-mediated Set2 degradation promotes chronological aging of Saccharomyces cerevisiae

Loss of transcription-coupled histone H3 lysine 36 trimethylation (H3K36me3) contributes to shorter lifespans in eukaryotes. However, the molecular mechanism of the decline of H3K36me3 during aging remains poorly understood. Here, we report that the degradation of the methyltransferase Set2 is the cause of decreased H3K36me3 levels during chronological aging in budding yeast. We show that Set2 protein degradation during cellular senescence and chronological aging is mainly mediated by the ubiquitin-conjugating E2 enzyme Ubc3 and the E3 ligase Bre1. Lack of Bre1 or abolishment of the ubiquitination stabilizes Set2 protein, sustains H3K36me3 levels at the aging-related gene loci, and upregulates their gene expression, thus leading to extended chronological lifespan. We further illustrate that Gcn5-mediated Set2 acetylation is a prerequisite for Bre1-catalyzed Set2 polyubiquitination and proteolysis during aging. We propose that two sequential post-translational modifications regulate Set2 homeostasis, suggesting a potential strategy to target the Gcn5-Bre1-Set2 axis for intervention of longevity.