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A decline in mitochondrial function is a hallmark of aging and neurodegenerative diseases. It has been proposed that changes in mitochondrial morphology, including fragmentation of the tubular mitochondrial network, can lead to mitochondrial dysfunction, yet the mechanism of this loss of function is unclear. Most proteins contained within mitochondria are nuclear-encoded and must be properly targeted to the mitochondria. Here, we report that sustained mRNA localization and co-translational protein delivery leads to a heterogeneous protein distribution across fragmented mitochondria. We find that age-induced mitochondrial fragmentation drives a substantial increase in protein expression noise across fragments. Using a translational kinetic and molecular diffusion model, we find that protein expression noise is explained by the nature of stochastic compartmentalization and that co-translational protein delivery is the main contributor to increased heterogeneity. We observed that cells primarily reduce the variability in protein distribution by utilizing mitochondrial fission-fusion processes rather than relying on the mitophagy pathway. Furthermore, we are able to reduce the heterogeneity of the protein distribution by inhibiting co-translational protein targeting. This research lays the framework for a better understanding of the detrimental impact of mitochondrial fragmentation on the physiology of cells in aging and disease.

BackgroundRestraining or slowing ageing hallmarks at the cellular level have been proposed as a route to increased organismal lifespan and healthspan. Consequently, there is great interest in anti-ageing drug discovery. However, this currently requires laborious and lengthy longevity analysis. Here, we present a novel screening readout for the expedited discovery of compounds that restrain ageing of cell populations in vitro and enable extension of in vivo lifespan.MethodsUsing Illumina methylation arrays, we monitored DNA methylation changes accompanying long-term passaging of adult primary human cells in culture. This enabled us to develop, test, and validate the CellPopAge Clock, an epigenetic clock with underlying algorithm, unique among existing epigenetic clocks for its design to detect anti-ageing compounds in vitro. Additionally, we measured markers of senescence and performed longevity experiments in vivo in Drosophila, to further validate our approach to discover novel anti-ageing compounds. Finally, we bench mark our epigenetic clock with other available epigenetic clocks to consolidate its usefulness and specialisation for primary cells in culture.ResultsWe developed a novel epigenetic clock, the CellPopAge Clock, to accurately monitor the age of a population of adult human primary cells. We find that the CellPopAge Clock can detect decelerated passage-based ageing of human primary cells treated with rapamycin or trametinib, well-established longevity drugs. We then utilise the CellPopAge Clock as a screening tool for the identification of compounds which decelerate ageing of cell populations, uncovering novel anti-ageing drugs, torin2 and dactolisib (BEZ-235). We demonstrate that delayed epigenetic ageing in human primary cells treated with anti-ageing compounds is accompanied by a reduction in senescence and ageing biomarkers. Finally, we extend our screening platform in vivo by taking advantage of a specially formulated holidic medium for increased drug bioavailability in Drosophila. We show that the novel anti-ageing drugs, torin2 and dactolisib (BEZ-235), increase longevity in vivo.ConclusionsOur method expands the scope of CpG methylation profiling to accurately and rapidly detecting anti-ageing potential of drugs using human cells in vitro, and in vivo, providing a novel accelerated discovery platform to test sought after anti-ageing compounds and geroprotectors.

PURPOSE: Rexinoids, agonists of nuclear retinoid X receptor (RXR), have been used for the treatment of cancers and are well tolerated in both animals and humans. However, the usefulness of rexinoids in treatment of breast cancer remains unknown. This study examines the efficacy of IRX4204, a highly specific rexinoid, in breast cancer cell lines and preclinical models to identify a biomarker for response and potential mechanism of action. EXPERIMENTAL DESIGN: IRX4204 effects on breast cancer cell growth and viability were determined using cell lines, syngeneic mouse models, and primary patient-derived xenograft (PDX) tumors. In vitro assays of cell cycle, apoptosis, senescence, and lipid metabolism were used to uncover a potential mechanism of action. Standard anti-HER2 therapies were screened in combination with IRX4204 on a panel of breast cancer cell lines to determine drug synergy. RESULTS: IRX4204 significantly inhibits the growth of HER2-positive breast cancer cell lines, including trastuzumab and lapatinib-resistant JIMT-1 and HCC1954. Treatment with IRX4204 reduced tumor growth rate in the MMTV-ErbB2 mouse and HER2-positive PDX model by 49% and 44%, respectively. Mechanistic studies revealed IRX4204 modulates lipid metabolism and induces senescence of HER2-positive cells. In addition, IRX4204 demonstrates additivity and synergy with HER2-targeted mAbs, tyrosine kinase inhibitors, and antibody-drug conjugates. CONCLUSIONS: These findings identify HER2 as a biomarker for IRX4204 treatment response and demonstrate a novel use of RXR agonists to synergize with current anti-HER2 therapies. Furthermore, our results suggest that RXR agonists can be useful for the treatment of anti-HER2 resistant and metastatic HER2-positive breast cancer.

Dynamically organized chromatin complexes often involve multiplex chromatin interactions and sometimes chromatin-associated RNA1-3. Chromatin complex compositions change during cellular differentiation and ageing, and are expected to be highly heterogeneous among terminally differentiated single cells4-7. Here we introduce the multinucleic acid interaction mapping in single cells (MUSIC) technique for concurrent profiling of multiplex chromatin interactions, gene expression and RNA-chromatin associations within individual nuclei. When applied to 14 human frontal cortex samples from older donors, MUSIC delineated diverse cortical cell types and states. We observed that nuclei exhibiting fewer short-range chromatin interactions were correlated with both an older transcriptomic signature and Alzheimers disease pathology. Furthermore, the cell type exhibiting chromatin contacts between cis expression quantitative trait loci and a promoter tends to be that in which these cis expression quantitative trait loci specifically affect the expression of their target gene. In addition, female cortical cells exhibit highly heterogeneous interactions between XIST non-coding RNA and chromosome X, along with diverse spatial organizations of the X chromosomes. MUSIC presents a potent tool for exploration of chromatin architecture and transcription at cellular resolution in complex tissues.

The appearance of senescent cells in age-related diseases has spurred the search for compounds that can target senescent cells in tissues, termed senolytics. However, a major caveat with current senolytic screens is the use of cell lines as targets where senescence is induced in vitro, which does not necessarily reflect the identity and function of pathogenic senescent cells in vivo. Here, we developed a new pipeline leveraging a fluorescent murine reporter that allows for isolation and quantification of p16Ink4a+ cells in diseased tissues. By high-throughput screening in vitro, precision-cut lung slice (PCLS) screening ex vivo, and phenotypic screening in vivo, we identified a HSP90 inhibitor, XL888, as a potent senolytic in tissue fibrosis. XL888 treatment eliminated pathogenic p16Ink4a+ fibroblasts in a murine model of lung fibrosis and reduced fibrotic burden. Finally, XL888 preferentially targeted p16INK4a-hi human lung fibroblasts isolated from patients with idiopathic pulmonary fibrosis (IPF), and reduced p16INK4a+ fibroblasts from IPF PCLS ex vivo. This study provides proof of concept for a platform where p16INK4a+ cells are directly isolated from diseased tissues to identify compounds with in vivo and ex vivo efficacy in mice and humans, respectively, and provides a senolytic screening platform for other age-related diseases.

Age remains the central risk factor for many neurodegenerative diseases including Parkinson's disease, Alzheimer's disease and amyotrophic lateral sclerosis. Although the mechanisms of aging are complex, the age-related accumulation of senescent cells in neurodegeneration is well documented and their clearance can alleviate disease-related features in preclinical models. Senescence-like characteristics are observed in both neuronal and glial lineages, but their relative contribution to aging and neurodegeneration remains unclear. Human pluripotent stem cell-derived neurons provide an experimental model system to induce neuronal senescence. However, the extensive heterogeneity in the profile of senescent neurons and the methods to assess senescence remain major challenges. Here, we review the evidence of cellular senescence in neuronal aging and disease, discuss human pluripotent stem cell-based model systems used to investigate neuronal senescence and propose a panel of cellular and molecular hallmarks to characterize senescent neurons. Understanding the role of neuronal senescence may yield novel therapeutic opportunities in neurodegenerative disease.

Calorie restriction (CR) with adequate nutrient intake is a potential geroprotective intervention. To advance this concept in humans, we tested the hypothesis that moderate CR in healthy young-to-middle-aged individuals would reduce circulating biomarkers of cellular senescence, a fundamental mechanism of aging and aging-related conditions. Using plasma specimens from the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy (CALERIE™) phase 2 study, we found that CR significantly reduced the concentrations of several senescence biomarkers at 12 and 24 months compared to an ad libitum diet. Using machine learning, changes in biomarker concentrations emerged as important predictors of the change in HOMA-IR and insulin sensitivity index at 12 and 24 months, and the change in resting metabolic rate residual at 12 months. Finally, using adipose tissue RNA-sequencing data from a subset of participants, we observed a significant reduction in a senescence-focused gene set in response to CR at both 12 and 24 months compared to baseline. Our results advance the understanding of the effects of CR in humans and further support a link between cellular senescence and metabolic health.

Pulmonary arterial hypertension (PAH) is a devastating and progressive disease with limited treatment options. Endothelial dysfunction plays a central role in the development and progression of PAH, yet the underlying mechanisms are incompletely understood. The endosome-lysosome system is important to maintain cellular health, and the small GTPase RAB7 regulates many functions of this system. Here, we explored the role of RAB7 in endothelial cell (EC) function and lung vascular homeostasis. We found reduced expression of RAB7 in ECs from patients with PAH. Endothelial haploinsufficiency of RAB7 caused spontaneous pulmonary hypertension (PH) in mice. Silencing of RAB7 in ECs induced broad changes in gene expression revealed via RNA-Seq, and RAB7-silenced ECs showed impaired angiogenesis and expansion of a senescent cell fraction, combined with impaired endolysosomal trafficking and degradation, suggesting inhibition of autophagy at the predegradation level. Furthermore, mitochondrial membrane potential and oxidative phosphorylation were decreased, and glycolysis was enhanced. Treatment with the RAB7 activator ML-098 reduced established PH in rats with chronic hypoxia/SU5416. In conclusion, we demonstrate for the first time to our knowledge the fundamental impairment of EC function by loss of RAB7, causing PH, and show RAB7 activation to be a potential therapeutic strategy in a preclinical model of PH.

Understanding the mechanisms of the cellular aging processes is crucial for attempting to extend organismal lifespan and for studying age-related degenerative diseases. Yeast cells divide through budding, providing a classical biological model for studying cellular aging. With their powerful genetics, relatively short cell cycle, and well-established signaling pathways also found in animals, yeast cells offer valuable insights into the aging process. Recent experiments suggested the existence of two aging modes in yeast characterized by nucleolar and mitochondrial declines, respectively. By analyzing experimental data, this study shows that cells evolving into those two aging modes behave differently when they are young. While buds grow linearly in both modes, cells that consistently generate spherical buds throughout their lifespan demonstrate greater efficacy in controlling bud size and growth rate at young ages. A three-dimensional multiscale chemical-mechanical model was developed and used to suggest and test hypothesized impacts of aging on bud morphogenesis. Experimentally calibrated model simulations showed that during the early stage of budding, tubular bud shape in one aging mode could be generated by locally inserting new materials at the bud tip, a process guided by the polarized Cdc42 signal. Furthermore, the aspect ratio of the tubular bud could be stabilized during the late stage as observed in experiments in this work. The model simulation results suggest that the localization of new cell surface material insertion, regulated by chemical signal polarization, could be weakened due to cellular aging in yeast and other cell types, leading to the change and stabilization of the bud aspect ratio.

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.

The global loss of heterochromatin during ageing has been observed in eukaryotes from yeast to humans, and this has been proposed as one of the causes of ageing. However, the cause of this age-associated loss of heterochromatin has remained enigmatic. Here we show that heterochromatin markers, including histone H3K9 di/tri-methylation and HP1, decrease with age in muscle stem cells (MuSCs) as a consequence of the depletion of the methyl donor S-adenosylmethionine (SAM). We find that restoration of intracellular SAM in aged MuSCs restores heterochromatin content to youthful levels and rejuvenates age-associated features, including DNA damage accumulation, increased cell death, and defective muscle regeneration. SAM is not only a methyl group donor for transmethylation, but it is also an aminopropyl donor for polyamine synthesis. Excessive consumption of SAM in polyamine synthesis may reduce its availability for transmethylation. Consistent with this premise, we observe that perturbation of increased polyamine synthesis by inhibiting spermidine synthase restores intracellular SAM content and heterochromatin formation, leading to improvements in aged MuSC function and regenerative capacity in male and female mice. Together, our studies demonstrate a direct causal link between polyamine metabolism and epigenetic dysregulation during murine MuSC ageing.

Aging and cellular senescence are increasingly recognized as key contributors to pulmonary fibrosis. However, our understanding in the context of scleroderma-associated interstitial lung disease (SSc-ILD) is limited. To investigate, we leveraged previously established lung aging- and cell-specific senescence signatures to determine their presence and potential relevance to SSc-ILD. We performed a gene expression meta-analysis of lung tissues from 38 SSc-ILD and 18 healthy controls and found that markers (GDF15, COMP, and CDKN2A) and pathways (p53) of senescence were significantly increased in SSc-ILD. When probing the established aging and cellular senescence signatures, we found that epithelial and fibroblast senescence signatures had a 3.6- and 3.7-fold enrichment, respectively, in the lung tissue of SSc-ILD and that lung aging genes (CDKN2A, FRZB, PDE1A, and NAPI12) were increased in SSc-ILD. These signatures were also enriched in SSc skin and associated with degree of skin involvement (limited vs. diffuse cutaneous). To further support these findings, we examined telomere length (TL), a surrogate for aging, in the lung tissue and found that, independent of age, SSc-ILD had significantly shorter telomeres than controls in type II alveolar cells in the lung. TL in SSc-ILD was comparable to idiopathic pulmonary fibrosis, a disease of known aberrant aging. Taken together, this study provides novel insight into the possible mechanistic effects of accelerated aging and aberrant cellular senescence in SSc-ILD pathogenesis.

The nerve injury-induced protein 1 (NINJ1) and NINJ2 constitute a family of homophilic adhesion molecules and are involved in nerve regeneration. Previously, we showed that NINJ1 and p53 are mutually regulated and the NINJ1-p53 loop plays a critical role in p53-dependent tumor suppression. However, the biology of NINJ2 has not been well-explored. By using multiple in vitro cell lines and genetically engineered mouse embryo fibroblasts (MEFs), we showed that NINJ2 is induced by DNA damage in a p53-dependent manner. Moreover, we found that the loss of NINJ2 promotes p53 expression via mRNA translation and leads to growth suppression in wild-type p53-expressing MCF7 and Molt4 cells and premature senescence in MEFs in a wild-type p53-dependent manner. Interestingly, NINJ2 also regulates mutant p53 expression, and the loss of NINJ2 promotes cell growth and migration in mutant p53-expressing MIA-PaCa2 cells. Together, these data indicate that the mutual regulation between NINJ2 and p53 represents a negative feedback loop, and the NINJ2-p53 loop has opposing functions in wild-type p53-dependent growth suppression and mutant p53-dependent growth promotion.

Cellular senescence is an adverse factor in the development of pulmonary fibrosis (PF). Ginsenoside Rb1 has been found to inhibit both cellular senescence and PF. This study aimed to elucidate the molecular mechanisms by which ginsenoside Rb1 regulates cellular senescence and PF. A PF mouse model was established by Bleomycin (BLM) administration, and a cell model of senescence was constructed using MRC-5 cells treated with Adriamycin RD (ARD) administration. Hematoxylin and Eosin (HE) staining and Masson staining were employed to evaluate cellular structure and collagen fiber content. RT-qPCR and western blotting were used to detect mRNA and protein expression of the target genes. Enzyme-linked Immunosorbent Assay (ELISA) was applied to measure the protein concentration of IL-1β and IL-18. SA-β-gal staining was used to evaluate cellular senescence. Our results show that ginsenoside Rb1 effectively suppressed BLM-induced PF in mice. ARD administration to induce cellular senescence reduced NRF2, QKI, and SMAD7 expression in MRC-5 cells. By inducing NRF2 overexpression, ARD-induced cellular senescence and fibrosis in MRC-5 cells were relieved. Notably, NRF2 knockdown abolished the mitigating effects of ginsenoside Rb1 on ARD-induced cellular senescence and fibrosis in MRC-5 cells. Mechanistically, NRF2 increased SMAD7 mRNA stability through the transcriptional regulation of QKI. As expected, ginsenoside Rb1 alleviated ARD-induced senescence and fibrosis in MRC-5 cells by activating the NRF2/QKI/SMAD7 axis. Therefore, it was found that ginsenoside Rb1 mitigates cellular senescence and fibrosis during PF progression by activating the NRF2/QKI/SMAD7 axis. This study provides a potential therapeutic strategy for the treatment of PF and elucidates its mechanism of action. [ABSTRACT FROM AUTHOR]

Cellular senescence is a phenomenon distinguished by the halting of cellular division, typically triggered by DNA injury or numerous stress-inducing factors. Cellular senescence is implicated in various pathological and physiological processes and is a hallmark of aging. The presence of accumulated senescent cells, whether transiently (acute senescence) or persistently (chronic senescence) plays a dual role in various conditions such as natural kidney aging and different kidney disorders. Elevations in senescent cells and senescence-associated secretory phenotype (SASP) levels correlate with decreased kidney function, kidney ailments, and age-related conditions. Strategies involving senotherapeutic agents like senolytics, senomorphics, and senoinflammation have been devised to specifically target senescent cells. Mesenchymal stem cells (MSCs) and their secreted factors may also offer alternative approaches for anti-senescence interventions. The MSC-derived secretome compromises significant therapeutic benefits in kidney diseases by facilitating tissue repair via anti-inflammatory, anti-fibrosis, anti-apoptotic, and pro-angiogenesis effects, thereby improving kidney function and mitigating disease progression. Moreover, by promoting the clearance of senescent cells or modulating their secretory profiles, MSCs could potentially reverse some age-related declines in kidney function. This review article intends to shed light on the present discoveries concerning the role of cellular senescence in kidney aging and diseases. Furthermore, it outlines the role of senotherapeutics utilized to alleviate kidney damage and aging. It also highlights the possible impact of MSCs secretome on mitigating kidney injury and prolonging lifespan across various models of kidney diseases as a novel senotherapy. [ABSTRACT FROM AUTHOR]

Background: Cellular senescence is a key driver of decreased bone formation and osteoporosis. Leptin (LEP) has been implicated in cellular senescence and osteogenic differentiation. The aim of this study was to investigate the mechanisms by which LEP mediates cellular senescence and osteogenic differentiation. Methods: C3H10T1/2 cells were treated with etoposide to induce cellular senescence, which was assessed by β-galactosidase staining. Quantitative real-time PCR and western blotting were used to measure the levels of senescence markers p21 and p16, as well as osteogenic differentiation-related genes ALP, COL1A1, and RUNX2. Alkaline phosphatase (ALP) staining and alizarin red S staining were performed to evaluate osteogenic differentiation. The NF-κB pathway and O-GlcNAcylation were assessed by western blotting. Results: Etoposide treatment increased the number of senescent cells and the levels of p21 and p16, along with elevated LEP expression. These effects were reversed by LEP knockdown. Additionally, LEP knockdown increased ALP staining density and osteoblast mineralization nodules, as well as the mRNA and protein levels of ALP, COL1A1, and RUNX2, indicating that LEP knockdown promoted osteogenic differentiation in C3H10T1/2 cells. Mechanistically, LEP knockdown inactivated the NF-κB pathway by inhibiting the nuclear translocation of p65. Furthermore, OGT was found to promote O-GlcNAcylation of LEP at the S50 site. Conclusion: Our findings demonstrated that O-GlcNAcylation of LEP inactivated the NF-κB pathway by reducing LEP protein levels, thereby inhibiting cellular senescence and promoting osteogenic differentiation in C3H10T1/2 cells. This study may provide a novel therapeutic target for the treatment of osteoporosis. [ABSTRACT FROM AUTHOR]

Background: The androgen receptor (AR), a ligand-dependent transcription factor, plays a key role in regulating prostate cancer (PCa) growth. The novel bipolar androgen therapy (BAT) uses supraphysiological androgen levels (SAL) that suppresses growth of PCa cells and induces cellular senescence functioning as a tumor suppressive mechanism. The role of long non-coding RNAs (lncRNAs) in the regulation of SAL-mediated senescence remains unclear. This study focuses on the SAL-repressed lncRNA MIR503HG, examining its involvement in androgen-controlled cellular senescence in PCa. Methods: Transcriptome and ChIP-Seq analyses of PCa cells treated with SAL were conducted to identify SAL-downregulated lncRNAs. Expression levels of MIR503HG were analyzed in 691 PCa patient tumor samples, mouse xenograft tumors and treated patient-derived xenografts. Knockdown and overexpression experiments were performed to assess the role of MIR503HG in cellular senescence and proliferation using senescence-associated β-Gal assays, qRT-PCRs, and Western blotting. The activity of MIR503HG was confirmed in PCa tumor spheroids. Results: A large patient cohort analysis shows that MIR503HG is overexpressed in metastatic PCa and is associated with reduced patient survival, indicating its potential oncogenic role. Notably, SAL treatment suppresses MIR503HG expression across four different PCa cell lines and patient-derived xenografts but interestingly not in the senescence-resistant LNCaP Abl EnzaR cells. Functional assays reveal that MIR503HG promotes PCa cell proliferation and inhibits SAL-mediated cellular senescence, partly through miR-424-5p. Mechanistic analyses and rescue experiments indicate that MIR503HG regulates the AKT-p70S6K and the p15INK4b-pRb pathway. Reduced expression of MIR503HG by SAL or knockdown resulted in decreased BRCA2 levels suggesting a role in DNA repair mechanisms and potential implications for PARP inhibitor sensitivity by SAL used in BAT clinical trial. Conclusions: The lncRNA MIR503HG acts as an oncogenic regulator in PCa by repressing cellular senescence. SAL-induced suppression of MIR503HG enhances the tumor-suppressive effects of AR signaling, suggesting that MIR503HG could serve as a biomarker for BAT responsiveness and as a target for combination therapies with PARP inhibitors. [ABSTRACT FROM AUTHOR]

[Display omitted] Cellular senescence is involved in the progression of neurodegenerative diseases. Motor neurons exhibit senescence-like alterations in ALS. BRD7, identified as a regulatory factor associated with cellular senescence, its function in ALS remains unclear. This study aims to investigate the potential role and mechanisms of BRD7 in ALS. We analyzed RNA levels using qRT-PCR, protein levels through immunofluorescence and western blot, and apoptosis via TUNEL staining. Cell transfection was conducted for in vitro experiments. The level of β-galactosidase was measured by β-galactosidase activity detection kit. ALS motor neurons exhibited senescence-like alterations, characterized by increased activity of p53, p21, and β-galactosidase, as well as reduced lamin B1 staining. Additionally, the expression of BRD7 was upregulated and induced cellular senescence and apoptosis. Downregulation of BRD7 alleviates the cellular senescence by inhibiting p21 rather than p53. Knockdown of BRD7 inhibited p53 mitochondrial translocation, leading to reduced apoptosis. Our results suggest that BRD7 plays an important role in the survival of ALS motor neurons. BRD7 knockdown can reduce cellular senescence and apoptosis by inhibiting p21 and p53 mitochondrial translocation. [ABSTRACT FROM AUTHOR]

Traumatic brain injury (TBI) and stroke pose major health challenges, impacting millions of individuals globally. Once considered solely acute events, these neurological conditions are now recognized as enduring pathological processes with long-term consequences, including an increased susceptibility to neurodegeneration. However, effective strategies to counteract their devastating consequences are still lacking. Cellular senescence, marked by irreversible cell-cycle arrest, is emerging as a crucial factor in various neurodegenerative diseases. Recent research further reveals that cellular senescence may be a potential driver for secondary neurodegeneration following brain injury. Herein, we synthesize emerging evidence that TBI and stroke drive the accumulation of senescent cells in the brain. The rationale for targeting senescent cells as a therapeutic approach to combat neurodegeneration following TBI/stroke is outlined. From a translational perspective, we emphasize current knowledge and future directions of senolytic therapy for these neurological conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT Currently, there is no specific treatment for diabetes‐induced osteoporosis (DOP). Our study identified diabetes‐induced cellular senescence, marked by elevated activity of senescence‐associated β‐galactosidase. Targeting senescent cells holds promise for osteoporosis treatment. We demonstrated that scutellarin (SCU) effectively mitigated bone loss in DOP mice, and co‐treatment with SCU significantly reduced diabetes‐induced senescence in LepR+MSCs. Furthermore, our research highlighted the role of Nrf2 in SCU's anti‐senescence effects on bone. The deletion of Nrf2 impaired SCU's ability to alleviate DOP. Mechanistically, SCU enhances Ezh2 expression and increases H3K27me3 activity at the Keap1 promoter region, leading to Keap1 repression and enhanced Nrf2‐ARE signalling. Additionally, SCU notably inhibited cellular senescence and diabetes‐related osteoporosis, these effects were significantly reduced in Ezh2LepRcre conditional knockout models. These findings suggest that the Ezh2‐Nrf2 signalling axis is crucial for mediating SCU's beneficial effects in this context. Overall, our discoveries provide insights into the mechanisms underlying DOP and propose a potential preventive strategy for this condition. [ABSTRACT FROM AUTHOR]

Cellular senescence plays critical roles in aging, regeneration, and disease; yet, the ability to discern its contributions across various cell types to these biological processes remains limited. In this study, we generated an in vivo genetic toolbox consisting of three p16 Ink4a -related intersectional genetic systems, enabling pulse-chase tracing (Sn-pTracer), Cre-based tracing and ablation (Sn-cTracer), and gene manipulation combined with tracing (Sn-gTracer) of defined p16 Ink4a + cell types. Using liver injury and repair as an example, we found that macrophages and endothelial cells (ECs) represent distinct senescent cell populations with different fates and functions during liver fibrosis and repair. Notably, clearance of p16 Ink4a + macrophages significantly mitigates hepatocellular damage, whereas eliminating p16 Ink4a + ECs aggravates liver injury. Additionally, targeted reprogramming of p16 Ink4a + ECs through Kdr overexpression markedly reduces liver fibrosis. This study illuminates the functional diversity of p16 Ink4a + cells and offers insights for developing cell-type-specific senolytic therapies in the future. [Display omitted] • Intersectional genetics enables tracing, ablation, and manipulation of defined p16 Ink4a + cell types • Ablation of p16 Ink4a + macrophages ameliorates liver fibrosis • p16 Ink4a + endothelial cells play a reparative role in liver injury • Reprogramming of p16 Ink4a + endothelial cells ameliorates liver fibrosis A dual recombinase-mediated genetic system for cell-type-specific lineage tracing, ablation, and gene manipulation of senescent cells reveals distinct roles of senescence across cell types. [ABSTRACT FROM AUTHOR]

AbstractUrban aerosol particulate matter (UPM) is widespread in the environment, and its concentration continues to increase. Several recent studies have reported that UPM results in premature cellular senescence, but few studies have investigated the molecular basis of UPM-induced senescence in retinal pigment epithelial (RPE) cells. In this study, we primarily evaluated UPM-induced premature senescence and the protective function of nuclear factor erythroid 2-related factor 2 (Nrf2) in human RPE ARPE-19 cells. The findings indicated that UPM exposure substantially induced premature cellular senescence in ARPE-19 cells, as observed by increased β-galactosidase activity, expression levels of senescence-associated marker proteins, and senescence-associated phenotypes. Such UPM-induced senescence is associated with mitochondrial oxidative stress-mediated phosphatidylinositol 3’-kinase/Akt/Nrf2 downregulation. Sulforaphane-mediated Nrf2 activation Sulforaphane-mediated upregulation of phosphorylated Nrf2 suppressed the decrease in its target antioxidant gene, NAD(P)H quinone oxidoreductase 1, under UPM, which notably prevented ARPE-19 cells from UPM-induced cellular senescence. By contrast, Nrf2 knockdown exacerbated cellular senescence and promoted oxidative stress. Collectively, our results demonstrate the regulatory role of Nrf2 in UPM-induced senescence of RPE cells and suggest that Nrf2 is a potential molecular target. [ABSTRACT FROM AUTHOR]

BACKGROUND: The results of in vivo and in vitro studies showed that catalpol from Rehmannia glutinosa can significantly reduce the level of inflammatory indexes in the synovial tissue of rats with knee osteoarthritis, and meanwhile, it can delay the progression of knee osteoarthritis. But whether catalpol from Rehmannia glutinosa affects chondrocyte senescence and then delay the progression of knee osteoarthritis has not yet been clarified. OBJECTIVE: To investigate investigate whether catalpol from Rehmannia glutinosa could regulate ATDC5 chondrocyte senescence and the possible mechanisms. METHODS: ATDC5 chondrocytes were divided into blank group (0.1% bovine serum albumin), model group (0.1% bovine serum albumin+1 µmol/L adriamycin), low-dose catalpol group (0.1% bovine serum albumin+1 µmol/L adriamycin+20 µmol/L catalpol from Rehmannia glutinosa) and high-dose catalpol group (0.1% bovine serum albumin+1 µmol/L adriamycin+80 µmol/L catalpol from Rehmannia glutinosa). Adriamycin-induced ATDC5 chondrocyte senescence model was constructed, and the corresponding treatments were given according to the above groups. Cell counting kit-8 assay was used to detect the effects of catalpol from Rehmannia glutinosa on ATDC5 chondrocyte viability, and to screen the optimal concentration of catalpol from Rehmannia glutinosa. The senescence of ATDC5 chondrocytes in each group was detected by β-galactosidase staining after the corresponding treatments. Real-time fluorescence quantitative PCR and western blot were used to detect the mRNA and protein expression of P21, P53, type II collagen, matrix metalloproteinase 13, and interleukin-6. Immunofluorescence method was used to detect the expression of P21, P53 and type II collagen. Flow cytometry was used to detect apoptosis in each group. RESULTS AND CONCLUSION: ATDC5 chondrocytes were identified to be successfully induced and senescence model was induced. Catalpol from Rehmannia glutinosa at the concentrations of 0, 20, 40, and 80 µmol/L showed no significant effects on the cell viability, suggesting that catalpol from Rehmannia glutinosa is non-cytotoxic and can be used safely (P > 0.05); when the concentration was ≥ 100 µmol/L, the cell viability was reduced, suggesting that there may be cytotoxic. Therefore, 80 µmol/L was chosen as the high dose for subsequent experiments in this study. The percentage of positive cells in the model group was (86.93±2.18)%, which was significantly higher than that in the blank group [(17.32±0.72)%; P < 0.05]. Compared with the model group, the percentage of positive cells was significantly lower in the low- and high-dose catalpol groups [(57.28±1.73)% and (27.18±0.97)%, respectively; both P < 0.05]. Compared with the model group, the relative expression of P21, P53, matrix metalloproteinase 13, and interleukin-6 at mRNA and protein levels was significantly downregulated in the low- and high-dose catalpol groups, while the relative expression of type II collagen at mRNA and protein levels was significantly upregulated in both groups (P < 0.05), especially in the high-dose catalpol group (P < 0.05). Compared with the model group, the fluorescence intensities of P21 and P53 were significantly weakened in the low- and high-dose catalpol groups, while the fluorescence intensity of type II collagen was significantly enhanced in the low- and high-dose catalpol groups (P < 0.05), especially in the high-dose catalpol group (P < 0.05). The cell apoptosis detected by Annexin V/PI method showed that there was no significant difference between the model group and the blank group (P > 0.05); compared with the model group, the apoptotic index was significantly elevated in the low- and high-dose catalpol groups, especially in the high-dose catalpol group (P < 0.05). To conclude, catalpol from Rehmannia glutinosa can slow the progression of osteoarthritis by promoting apoptosis of senescent ATDC5 chondrocytes, further removing senescent ATDC5 chondrocytes, and decreasing the senescence-associated phenotypes. [ABSTRACT FROM AUTHOR]

Background: Senescence is recognized as a principal risk factor for cardiovascular diseases, with a significant association between the senescence of cardiomyocytes and inferior cardiac function. Furthermore, type 2 diabetes exacerbates this aging process. Sodium-glucose co-transporter 2 inhibitor (SGLT2i) has well-established cardiovascular benefits and, in recent years, has been posited to possess anti-aging properties. However, there are no reported data on their improvement of cardiomyocytes function through the alleviation of aging. Consequently, our study aims to investigate the mechanism by which SGLT2i exerts anti-aging and protective effects at the cardiac level through its action on the FOXO1-ANGPTL4 pathway. Methods: To elucidate the underlying functions and mechanisms, we established both in vivo and in vitro disease models, utilizing mice with diabetic cardiomyopathy (DCM) induced by type 2 diabetes mellitus (T2DM) through high-fat diet combined with streptozotocin (STZ) administration, and AC16 human cardiomyocyte cell subjected to stimulation with high glucose (HG) and palmitic acid (PA). These models were employed to assess the changes in the senescence phenotype of cardiomyocytes and cardiac function following treatment with SGLT2i. Concurrently, we identified ANGPTL4, a key factor contributing to senescence in DCM, using RNA sequencing (RNA-seq) technology and bioinformatics methods. We further clarified ANGPTL4 role in promoting pathological aging of cardiomyocytes induced by hyperglycemia and hyperlipidemia through knockdown and overexpression of the factor, as well as analyzed the impact of SGLT2i intervention on ANGPTL4 expression. Additionally, we utilized chromatin immunoprecipitation followed by quantitative real-time PCR (ChIP-qPCR) to confirm that FOXO1 is essential for the transcriptional activation of ANGPTL4. Results: The therapeutic intervention with SGLT2i alleviated the senescence phenotype in cardiomyocytes of the DCM mouse model constructed by high-fat feeding combined with STZ, as well as in the AC16 model stimulated by HG and PA, while also improving cardiac function in DCM mice. We observed that the knockdown of ANGPTL4, a key senescence-promoting factor in DCM identified through RNA-seq technology and bioinformatics, mitigated the senescence of cardiomyocytes, whereas overexpression of ANGPTL4 exacerbated it. Moreover, SGLT2i improved the senescence phenotype by suppressing the overexpression of ANGPTL4. In fact, we discovered that SGLT2i exert their effects by regulating the upstream transcription factor FOXO1 of ANGPTL4. Under conditions of hyperglycemia and hyperlipidemia, compared to the control group without FOXO1, the overexpression of FOXO1 in conjunction with SGLT2i intervention significantly reduced both ANGPTL4 mRNA and protein levels. This suggests that the FOXO1-ANGPTL4 axis may be a potential target for the cardioprotective effects of SGLT2i. Conclusions: Collectively, our study demonstrates that SGLT2i ameliorate the pathological aging of cardiomyocytes induced by a high glucose and high fat metabolic milieu by regulating the interaction between FOXO1 and ANGPTL4, thereby suppressing the transcriptional synthesis of the latter, and consequently restoring cardiac function. [ABSTRACT FROM AUTHOR]

Excessive exposure to ultraviolet radiation B (UVB) has been shown to contribute to the aging of human skin cells. Previous research has demonstrated that atorvastatin calcium (Ato) can mitigate the aging effects caused by chemotherapy drugs. However, it remains unclear whether Ato can alleviate skin aging induced by ultraviolet radiation. In this study, through in vitro experiments with Hacat cells, we found that Ato can significantly reduce the UVB-induced increased expression of age-related protein p16 and age-related gene p21, and also reduce the up-regulation of inflammatory factors such as IL-1 and IL-6. Besides, it can reduce the expression of metallomatrix protein (MMP1 and MMP9), and inhibit cell senescence and inflammatory damage. Similarly, we found that Ato can enhance skin collagen fiber reduction and collagen volume decrease, repair skin photoaging and damage induced by UVB rays, and speed up the rate at which the wounded location heals in vivo using Balb/c mice. In the mechanism, Ato markedly decreased the expression of p-p38, p-p65, p-mTOR in vivo and in vitro, suggesting that it may act on Mitogen-activated protein kinase (MAPK), Nuclear factor κB (NF- κB) and Mammalian target of rapamycin (mTOR) signaling pathways to produce above marked effects. In conclusion, Ato obviously relieved UVB-induced photoaging and damage, thus providing evidence for its potential in mitigating skin aging caused by ultraviolet radiation. [ABSTRACT FROM AUTHOR]

Senescent cells play a causative role in many diseases, and their elimination is a promising therapeutic strategy. Here, through a genome-wide CRISPR/Cas9 screen, we identify the gene PPIF, encoding the mitochondrial protein cyclophilin D (CypD), as a novel senolytic target. Cyclophilin D promotes the transient opening of the mitochondrial permeability transition pore (mPTP), which serves as a failsafe mechanism for calcium efflux. We show that senescent cells exhibit a high frequency of transient CypD/mPTP opening events, known as 'flickering'. Inhibition of CypD using genetic or pharmacologic tools, including cyclosporin A, leads to the toxic accumulation of mitochondrial Ca2+ and the death of senescent cells. Genetic or pharmacological inhibition of NCLX, another mitochondrial calcium efflux channel, also leads to senolysis, while inhibition of the main Ca2+ influx channel, MCU, prevents senolysis induced by CypD inhibition. We conclude that senescent cells are highly vulnerable to elevated mitochondrial Ca2+ ions, and that transient CypD/mPTP opening is a critical adaptation mechanism for the survival of senescent cells. Synopsis: Senescent cells present an excessive flux of Ca2+ from the ER into the mitochondria. This study shows that cyclophilin D increases the survival of senescent cells by mediating a transient opening of the mitochondrial permeability transition pore (mPTP). Cyclophilin D (CypD) is a novel senolytic target. Senescent cells rely on CypD-dependent mPTP flickering, a mechanism that effects matrix Ca2+ efflux. Genetic or pharmacological blockage of CypD or of mitochondrial Ca2+ efflux channel NCLX leads to preferential elimination of senescent cells. Reduction of mitochondrial Ca2+ influx in senescent cells via MCU reduces the toxicity of CypD inhibition. Senescent cells rely on cyclophilin D to allow the release of calcium overload from the mitochondrial matrix. [ABSTRACT FROM AUTHOR]

Purpose: Ischemia-reperfusion injury (IRI) is a major challenge in lung transplantation often causing graft dysfunction and chronic airway illnesses in recipients. To prevent potential transplant related complications, strict guidelines were put in place to choose viable donor lungs with minimal risk of IRI. These regulations deem most of the donor organs unfit for transplant which then are donated for research to understand the mechanisms of health and diseases in human. However, resected organs that are being transported undergo cold ischemia that can negatively affect the tissue architecture and other cellular functions under study. Thus, it is important to assess how cold ischemia time (CIT) affects the physiological mechanism. In this respect, we are interested in studying how CIT affects cellular senescence in normal aging and various pulmonary pathologies. We thus hypothesized that prolonged CIT exhibits cell-type specific changes in lung cellular senescence in mice. Methods: Lung lobes from C57BL/6J (n = 5–8) mice were harvested and stored in UW Belzer cold storage solution for 0, 4-, 9-, 12-, 24-, and 48-h CIT. Lung cellular senescence was determined using fluorescence (C12FdG) assay and co-immunolabelling was performed to identify changes in individual cell types. Results: We found a rapid decline in the overall lung cellular senescence after 4-h of CIT in our study. Co-immunolabelling revealed the endothelial cells to be most affected by cold ischemia, demonstrating significant decrease in the endothelial cell senescence immediately after harvest. Annexin V-PI staining further revealed a prominent increase in the number of necrotic cells at 4-h CIT, thus suggesting that most of the cells undergo cell death within a few hours of cold ischemic injury. Conclusions: We thus concluded that CIT significantly lowers the cellular senescence in lung tissues and must be considered as a confounding factor for mechanistic studies in the future. [ABSTRACT FROM AUTHOR]

An abdominal aortic aneurysm (AAA) is described as a gradual and localized permanent expansion of the aorta resulting from the weakening of the vascular wall. The key aspects of AAA's progression are high proteolysis of the structural elements of the vascular wall, the depletion of vascular smooth muscle cells (VSMCs), and a chronic immunoinflammatory response. The pathological mechanisms underpinning the development of an AAA are complex and still unknown. At present, there are no successful drug treatments available that can slow the progression of an AAA or prevent the rupture of the aneurysmal vascular wall. Recently, it has been suggested that endothelial cellular senescence may be involved in vascular aging and vascular aging diseases, but there is no clear correlation between cellular senescence and AAAs. Therefore, the aim of this study was to identify the presence of senescent cells on the vascular wall of aneurysmatic abdominal aortas and to correlate their distribution with the morphological markers of AAAs. Pathological and healthy segments of abdominal aortas were collected during repair surgery and immediately processed for histological and immunohistochemical analyses. Hematoxylin/eosin, Verhoeff–van Gieson, and Goldner's Masson trichrome staining procedures were carried out to investigate the morphological features related to the pathology. Immunohistochemical investigations for the p21cip1/waf1, p53, and NFkB markers were carried out to selectively identify positive cells in the vascular wall of the AAA samples related to cellular senescence and an inflammatory microenvironment. The results revealed the presence of a few senescent vascular cells on the aneurysmatic wall of the abdominal aortas, surrounded by a highly inflamed microenvironment that was highly expressed in the tunica media and adventitia of both pathological and healthy segments. Our data demonstrate the presence of senescent vascular cells in AAA samples, which could enhance the promotion of a high inflammatory vascular microenvironment, supporting the evolution of the pathology. Although this study was based on only two cases, the results highlight the importance of targeting cellular senescence to reduce an inflammatory microenvironment, which can support the progression of age-related diseases. [ABSTRACT FROM AUTHOR]

Senescent osteocytes are key contributors to age‐related bone loss and fragility; however, the impact of mechanobiological changes in these cells remains poorly understood. This study provides a novel analysis of these changes in primary osteocytes following irradiation‐induced senescence. By integrating subcellular mechanical measurements with gene expression analyses, we identified significant, time‐dependent alterations in the mechanical properties of senescent bone cells. Increases in classical markers such as SA‐β‐Gal activity and p16Ink4a expression levels confirmed the senescence status post‐irradiation. Our key findings include a time‐dependent increase in cytoskeletal Young's modulus and altered viscoelastic properties of the plasma membrane, affecting the contractility of primary osteocytes. Additionally, we observed a significant increase in Sclerostin (Sost) expression 21 days post‐irradiation. These biophysical changes may impair osteocyte mechanosensation and mechanotransduction, contributing to bone fragility. This is the first study to time‐map senescence‐associated mechanical changes in the osteocyte cytoskeleton. Our findings highlight the potential of biophysical markers as indicators of cellular senescence, providing more specificity than traditional, variable biomolecular markers. We believe these results may support biomechanical stimulation as a potential therapeutic strategy to rejuvenate aging osteocytes and enhance bone health. [ABSTRACT FROM AUTHOR]

GORAB is a key regulator of Golgi vesicle transport and protein glycanation. Loss of GORAB function in gerodermia osteodysplastica (GO) causes shortening of glycosaminoglycan chains, leading to extracellular matrix disorganization that results in wrinkled skin, osteoporosis and elevated TGF‐β signaling. In this study, we investigated the role of TGF‐β‐signaling, oxidative stress, and resulting cellular senescence in the osteoporosis phenotype of GO. Treatment of GorabPrx1 conditional knockouts with the TGF‐β neutralizing antibody 1D11 rescued the trabecular bone loss, indicating that TGF‐β overactivation causes osteoporosis in GO. Using an inducible knockout system, we demonstrated that TGF‐β dysregulation was not a cell‐intrinsic effect of GORAB inactivation, but a consequence of a disorganized extracellular matrix. Enhanced TGF‐β signaling caused elevated Nox4 expression in GorabPrx1 mutants and in GO patients' fibroblasts, resulting in overproduction of mitochondrial superoxide. The resulting oxidative stress was detected in GORAB null cells and also in wildtype bystander cells. The same effect was observed in zebrafish after TALEN‐mediated gorab inactivation, indicating that the pathway is evolutionarily conserved. Treating GorabPrx1 mutants with the antioxidant N‐acetylcysteine ameliorated the osteoporosis phenotype. TGF‐β induced oxidative stress coincided with accumulation of DNA damage and elevated expression of senescence markers. Inactivation of Cdkn2a in the GorabPrx1 rescued the osteoporosis phenotype. Reduced colony formation and altered subpopulations of bone marrow stromal cells were normalized upon inactivation of Cdkn2a, thus further demonstrating the relevance of cellular senescence in the pathogenesis. Our results shed light on the causative role of a TGF‐β‐Nox4‐senescence axis and therapeutic strategies for GO. [ABSTRACT FROM AUTHOR]

The accumulation of senescent cells is thought to play a crucial role in aging‐associated physiological decline and the pathogenesis of various age‐related pathologies. Targeting senescence‐associated cell surface molecules through immunotherapy emerges as a promising avenue for the selective removal of these cells. Despite its potential, a thorough characterization of senescence‐specific surface proteins remains to be achieved. Our study addresses this gap by conducting an extensive analysis of the cell surface proteome, or "surfaceome", in senescent cells, spanning various senescence induction regimes and encompassing both murine and human cell types. Utilizing quantitative mass spectrometry, we investigated enriched cell surface proteins across eight distinct models of senescence. Our results uncover significant changes in surfaceome expression profiles during senescence, highlighting extensive modifications in cell mechanics and extracellular matrix remodeling. Our research also reveals substantive heterogeneity of senescence, predominantly influenced by cell type and senescence inducer. A key discovery of our study is the identification of four unique cell surface proteins with extracellular epitopes. These proteins are expressed in senescent cells, absent or present at low levels in their proliferating counterparts, and notably upregulated in tissues from aged mice and an Alzheimer's disease mouse model. These proteins stand out as promising candidates for senotherapeutic targeting, offering potential pathways for the detection and strategic targeting of senescent cell populations in aging and age‐related diseases. [ABSTRACT FROM AUTHOR]

In recent years, there has been increasing attention towards understanding the relationship between age‐related alterations in the oral microbiota and age‐associated diseases, with reports emphasizing the significance of maintaining a balanced oral microbiota for host health. However, the precise mechanisms underlying age‐related changes in the oral microbiota remain elusive. We recently reported that cellular senescence of ileal germinal center (GC) B cells, triggered by the persistent presence of commensal bacteria, results in diminished IgA production with aging and subsequent alterations in the gut microbiota. Consequently, we hypothesize that a similar phenomenon may occur in the oral cavity, potentially contributing to age‐related changes in the oral microbiota. Examination of p16‐luc mice, wherein the expression of the senescent cell marker p16INK4a can be visualized, raised under specific pathogen‐free (SPF) or germ‐free (GF) conditions, indicated that, unlike ileal GC B cells, the accumulation of senescent cells in GC B cells of cervical lymph nodes increases with age regardless of the presence of commensal bacteria. Furthermore, longitudinal studies utilizing the same individual mice throughout their lifespan revealed concurrent age‐related alterations in the composition of the oral microbiota and a decline in salivary IgA secretion. Further investigation involving Rag1−/− mice transplanted with B cells from wild‐type or p16INK4a and p21Waf1/Cip1 ‐double knockout mice unveiled that B cell senescence leads to reduced IgA secretion and alteration of the oral microbiota. These findings advance our understanding of the mechanism of age‐associated changes in the oral microbiota and open up possibilities of their control. [ABSTRACT FROM AUTHOR]

Glucagon-like peptide-1 (GLP-1) receptor agonists are effective hypoglycemic agents for type 2 diabetes mellitus (T2DM). It was reported that T2DM was implicated in pancreatic β-cell senescence. Whether loxenatide regulates cellular senescence of pancreatic β-cells is to be investigated. Our results revealed that high glucose (HG)-induced cellular senescence and elevated expression of SASP factors inhibited cell proliferation and stimulated DNA damage, which were reversed by loxenatide treatment. In addition, HG induction resulted in promoted insulin secretion and insulin synthesis of pancreatic β-cells and loxenatide treatment further strengthened these influences. In addition, loxenatide could inactivate the PERK/eIF2α signaling pathway via decreasing the levels of p-PERK and p-eIF2α in HG-induced pancreatic β-cells. Furthermore, CCT020312, an activator of the PERK/eIF2α signaling pathway, abolished loxenatide-mediated inhibiting cellular senescence, elevating cell proliferation and improving DNA damage and enhancing insulin secretion of HG-induced pancreatic β-cells. In conclusion, our results indicated that loxenatide impeded cellular senescence, promoted cell proliferation, improved DNA damage, enhanced insulin secretion and insulin synthesis of HG-induced pancreatic β-cells through modulating the PERK/eIF2α signaling pathway. [ABSTRACT FROM AUTHOR]

T lymphocytes expressing CD57 and lacking costimulatory receptors CD27/CD28 have been reported to accumulate with aging, chronic infection, and cancer. These cells are described as senescent, with inability to proliferate but enhanced cytolytic and cytokine-producing capacity. However, robust functional studies on these cells taken directly from cancer patients are lacking. We isolated these T cells and their CD27/28+ counterparts from blood and tumor samples of 50 patients with previously untreated head and neck cancer. Functional studies confirmed that these cells have enhanced ability to degranulate and produce IFN-γ. They also retain the ability to proliferate, thus are not senescent. These data suggest that CD27/28-CD57+ CD8+ T cells are a subset of highly differentiated, CD45RA+ effector memory (TEMRA) cells with retained proliferative capacity. Patients with > 34% of these cells among CD8+ T cells in the blood had a higher rate of locoregional disease relapse, suggesting these cells may have prognostic significance. [ABSTRACT FROM AUTHOR]

Periodontal disease is the pathological outcome of the overwhelming inflammation in periodontal tissue. Cellular senescence has been associated with chronic inflammation in several diseases. However, the role of cellular senescence in the pathogenesis of periodontal disease remained unclear. This study aimed to investigate the role and the mechanism of cellular senescence in periodontal disease. Using single-cell RNA sequencing, we first found the upregulated level of cellular senescence in fibroblasts and endothelial cells from inflamed gingival tissue. Subsequently, human gingival fibroblasts isolated from healthy and inflamed gingival tissues were labeled as H-GFs and I-GFs, respectively. Compared to H-GFs, I-GFs exhibited a distinct cellular senescence phenotype, including an increased proportion of senescence-associated β-galactosidase (SA-β-gal) positive cells, enlarged cell morphology, and significant upregulation of p16INK4A expression. We further observed increased cellular reactive oxygen species (ROS) activity, mitochondrial ROS, and DNA damage of I-GFs. These phenotypes could be reversed by ROS scavenger NAC, which suggested the cause of cellular senescence in I-GFs. The migration and proliferation assay showed the decreased activity of I-GFs while the gene expression of senescence-associated secretory phenotype (SASP) factors such as IL-1β, IL-6, TGF-β, and IL-8 was all significantly increased. Finally, we found that supernatants of I-GF culture induced more neutrophil extracellular trap (NET) formation and drove macrophage polarization toward the CD86-positive M1 pro-inflammatory phenotype. Altogether, our findings implicate that, in the inflamed gingiva, human gingival fibroblasts acquire a senescent phenotype due to oxidative stress-induced DNA and mitochondrial damage, which in turn activate neutrophils and macrophages through the secretion of SASP factors. [ABSTRACT FROM AUTHOR]

Cellular senescence is a cell fate characterized by cell cycle arrest in response to genome-dependent and -independent cell stress and damage. Cellular senescence phenotypes vary depending on the type of cellular stress, cell type, and tissue background. Our review discusses the emerging molecular mechanisms regulating various senescence phenotypes, with an emphasis on the DNA damage response and cellular stress. There is no single biomarker of cellular senescence; therefore, we provide a comprehensive tool kit and guide highlighting novel machine learning and molecular biology-based assays that can detect cellular senescence features to complement established biomarkers of senescence. This review comprehensively examines the molecular biology and genetic origins of cellular senescence. We focus on various cellular stressors and pathways leading to senescence, including recent advances in the understanding of the genetic influences driving senescence, such as telomere attrition, chemotherapy-induced DNA damage, pathogens, oncogene activation, and cellular and metabolic stress. This review also highlights the complex interplay of various signaling and metabolic pathways involved in cellular senescence and provides insights into potential therapeutic targets for aging-related diseases. Furthermore, this review outlines future research directions to deepen our understanding of senescence biology and develop effective interventions targeting senescent cells (SnCs). [ABSTRACT FROM AUTHOR]

Purpose: To investigate the role of moderate doses of ionizing radiation-induced cellular senescence in mouse lung tissue and whole-body inflammation levels. Material and methods: Forty-two C57BL/6J mice were randomly divided into the control group, the 1, 3, and 7 days after 2 Gy irradiation group, and the 1, 3, and 7 days after 4 Gy irradiation group, with six mice in each group. The histopathology, cellular senescence, oxidative-antioxidant, DNA damage repair, and inflammation-related indicators of irradiated mice were examined. Results: Compared with the control group, the histopathological scores, the positive area of senescence-associated-β-galactosidase (SA-β-Gal) staining, and the mRNA levels of senescence-related genes in the lung tissues in all dose groups increased on 1, 3, and 7 days after irradiation. In peripheral blood, erythrocytes, leukocytes, platelets, hemoglobin, 8-hydroxydeoxyguanosine (8-OHdG), C-reactive protein, and other indicators showed a different trend in all dose groups. The levels of malondialdehyde(MDA), superoxide dismutase (SOD), glutathione (GSH), and 8-OHdG in the lung tissue showed different trends after 2 Gy and 4 Gy irradiation. The 8-Oxoguanine DNA glycosylase 1 (hOGG1) and O-6-methylguanine-DNA methyltransferase (MGMT) mRNA levels showed a trend of increasing and then decreasing. The levels of whole-body inflammation were significantly correlated with the levels of indicators related to cellular senescence and damage repair in the lung tissue of mice. Conclusions: The moderate doses of ionizing radiation induce oxidative stress, and DNA damage and increase DNA repair gene expression in mouse lung tissue. The lung tissue cellular senescence correlates with the level of whole-body inflammation. [ABSTRACT FROM AUTHOR]

Atherosclerosis is the pathological cause of atherosclerotic cardiovascular disease (ASCVD), which rapidly progresses during the cellular senescence. Sodium-glucose cotransporter 2 inhibitors (SGLT2is) reduce major cardiovascular events in patients with ASCVD and have potential antisenescence effects. Here, we investigate the effects of the SGLT2 inhibitor dapagliflozin on cellular senescence in atherosclerotic mice. Compared with ApoE−/− control mice treated with normal saline, those in the ApoE−/− dapagliflozin group, receiving intragastric dapagliflozin (0.1 mg kg−1 d−1) for 14 weeks, exhibited the reduction in the total aortic plaque area (48.8%±6.6% vs. 74.6%±8.0%, P<0.05), the decrease in the lipid core area ((0.019±0.0037) mm2vs. (0.032±0.0062) mm2, P<0.05) and in the percentage of senescent cells within the plaques (16.4%±3.7% vs. 30.7%±2.0%, P<0.01), while the increase in the thickness of the fibrous cap ((21.6±2.1) µm vs. (14.6±1.5) µm, P<0.01). Transcriptome sequencing of the aortic arch in the mice revealed the involvement of the PPARα and the fatty acid metabolic signaling pathways in dapagliflozin's mechanism of ameliorating cellular aging and plaque progression. In vitro, dapagliflozin inhibited the expression of PPARα and its downstream signal FABP4, by which the accumulation of senescent cells in human aortic smooth muscle cells (HASMCs) was reduced under high-fat conditions. This effect was accompanied by a reduction in the intracellular lipid content and alleviation of oxidative stress. However, these beneficial effects of dapagliflozin could be reversed by the PPARα overexpression. Bioinformatics analysis and molecular docking simulations revealed that dapagliflozin might exert its effects by directly interacting with the RXRA protein, thereby influencing the expression of the PPARα signaling pathway. In conclusion, the cellular senescence of aortic smooth muscle cells is potentially altered by dapagliflozin through the suppression of the RXRA-PPARα-FABP4 signaling pathway, resulting in a deceleration of atherosclerotic progression. [ABSTRACT FROM AUTHOR]

Rat dental pulp stem cells (DPSCs) can be used to elucidate mesenchymal stem cell (MSC) applications in regenerative medicine. However, information on rat DPSCs during long-term passage, which could lead to replicative senescence, is limited. In this study, we investigated the phenotypic changes in DPSCs after 3–26 passages (3P–26P). The results show that cell morphology and nuclear size increase proportionally with passage number. The phosphorylated histone H2A.X (γ-H2A.X) positive cells (indicating DNA damage) increased significantly earlier than the 4-Hydroxynonenal (4-HNE) stained cells (indicating an abundance of intracellular reactive oxygen species). Compared to the cells subjected to 3P and 5P, the cells subjected to 15P showed reduced proliferation despite being positive for Ki67. Furthermore, cell growth was completely arrested after 26P. The senescence markers, senescence-associated β-galactosidase (SA-β-gal) and p16, exhibited similar expression patterns that were not correlated with those of p21 and urokinase-type plasminogen activator receptor (uPAR). Nearly all cells expressed SA-β-gal and p16 after 26P, whereas only half expressed p21 and uPAR. These results will contribute to understanding the characteristics of DPSCs toward replicative senescence, which are applicable to elucidate mechanisms related to regenerative medicine and stem cell aging. [ABSTRACT FROM AUTHOR]

The mortality associated with acute lung injury (ALI) increases with age. Alveolar epithelial type II (AEII) cells are the progenitor cells of the alveolar epithelium and are crucial for repair after injury. We hypothesize that telomere dysfunction–mediated AEII cell senescence impairs regeneration and promotes the development of ALI. To discriminate between the impact of old age and AEII cell senescence in ALI, young (3 mo) and old (18 mo) Sftpc-Ai9 mice with surfactant protein c mediated tdTomato expression, and young Sftpc-Ai9-Trf1 mice with additional telomeric repeat-binding factor 1 (Trf1) knockout–mediated senescence in AEII cells were treated with 1 μg LPS per gram body weight (n = 9–11). Control mice received saline solution (n = 7). Mice were killed 4 or 7 days later. Lung mechanics, pulmonary inflammation, and proteomes were analyzed, and parenchymal injury, AEII cell proliferation and AEI cell differentiation rate were quantified using stereology. Old mice showed 55% mortality by Day 4, whereas all young mice survived. Pulmonary inflammation was most severe in old Sftpc-Ai9 mice, followed by Sftpc-Ai9-Trf1 mice. Young Sftpc-Ai9 mice recovered almost completely by Day 7, whereas Sftpc-Ai9-Trf1 mice still showed mild signs of injury. An expansion of AEII cells was measured only in young Sftpc-Ai9 mice at Day 7. Aging and telomere dysfunction–mediated senescence had no impact on AEI differentiation rate in controls, but the reduced number of AEII cells in Sftpc-Ai9-Trf1 mice also affected de novo differentiation after injury. In conclusion, telomere dysfunction– mediated AEII cell senescence promoted parenchymal inflammation in ALI, but did not enhance mortality like old age. Although the differentiation rate remained functional with old age and AEII cell senescence, AEII cell proliferative capacity was impaired in ALI, affecting the regenerative ability. [ABSTRACT FROM AUTHOR]

Senescent cells secrete a senescence‐associated secretory phenotype (SASP), which can induce senescence in neighboring cells. Human dermal papilla (DP) cells lose their original hair inductive properties when expanded in vitro, and rapidly accumulate senescent cells in culture. Protein and RNA‐seq analysis revealed an accumulation of DP‐specific SASP factors including IL‐6, IL‐8, MCP‐1, and TIMP‐2. We found that combined senolytic treatment of dasatinib and quercetin depleted senescent cells, and reversed SASP accumulation and SASP‐mediated repressive interactions in human DP culture, resulting in an increased Wnt‐active cell population. In hair reconstitution assays, senolytic‐depleted DP cells exhibited restored hair inductive properties by regenerating de novo hair follicles (HFs) compared to untreated DP cells. In 3D skin constructs, senolytic‐depleted DP cells enhanced inductive potential and hair lineage specific differentiation of keratinocytes. These data revealed that senolytic treatment of cultured human DP cells markedly increased their inductive potency in HF regeneration, providing a new rationale for clinical applications of senolytic treatment in combination with cell‐based therapies. [ABSTRACT FROM AUTHOR]