Clearance Of Senescent Cells Research Articles

Clearance of senescent cells enhances skin wound healing in type 2 diabetic mice.

Background: Diabetic foot ulcers (DFUs) pose a substantial healthcare challenge due to their high rates of morbidity, recurrence, disability, and mortality. Current DFU therapeutics continue to grapple with multiple limitations. Senescent cells (SnCs) have been found to have a beneficial effect on acute wound healing, however, their roles in chronic wounds, such as DFU, remain unclear. Methods and results: We collected skin, fat, and muscle samples from clinical patients with DFU and lower limb fractures. RNA-sequencing combined with qPCR analyses on these samples demonstrate a significant accumulation of SnCs at DFU, as indicated by higher senescence markers (e.g., p16 and p21) and a senescence-associated secretory phenotype (SASP). We constructed a type 2 diabetic model of db/db mice, fed with a high-fat diet (Db-HFD), which were wounded using a 6 mm punch to the dorsal skin. HFD slightly affected wound healing in wild-type (WT) mice, but high glucose significantly delayed wound healing in the Db-HFD mice. We injected the mice with a previously developed fluorescent probe (XZ1208), which allows the detection of SnCs in vivo, and observed a strong senescence signal at the wound site of the Db-HFD mice. Contrary to the beneficial effects of SnCs in acute wound healing, our results demonstrated that clearance of SnCs using the senolytic compound ABT263 significantly accelerated wound healing in Db-HFD mice. Conclusion: Collectively, these findings suggest that SnCs critically accumulate at wound sites, delaying the healing process in DFUs. Thus, targeting SnCs with senolytic therapy represents a promising approach for DFU treatment, potentially improving the quality of life for patients with DFUs.

Flavonoid 4,4′-dimethoxychalcone selectively eliminates senescent cells via activating ferritinophagy

Flavonoids are bioactive natural polyphenolic compounds with health benefits, including anti-tumor, anti-inflammatory and anti-aging effects. Our previous studies revealed that a flavonoid 4,4′-dimethoxychalcone (DMC) induced ferroptosis via inhibiting ferrochelatase (FECH). However, the effect of DMC on cellular senescence is unknown. In the present study, we found that DMC treatment selectively eliminated senescent cells, and DMC alone or a combination of DMC and quercetin or dasatinib showed high efficiency in the clearance of senescent cells. We identified FECH was highly expressed in senescent cells compared to non-senescent cells. Mechanistically, we found that DMC inhibited FECH and induced ferritinophagy, which led to an increase of labile iron pool, triggering ferroptosis of senescent cells. Importantly, we found that DMC treatment prevented hair loss, improved motor coordination, and reduced the expression of several senescence-associated secretory phenotype factors (IL-6, IL-1β, CXCL-10, and MMP12) in the liver of old mice. Collectively, we revealed that, through the induction of ferroptosis, DMC holds the promise as a new senolytics to prevent age-related pathologies.

IDENTIFYING SENOLYTIC TARGETS OF DIETARY FLAVONOIDS IN RENAL CELLS BY THERMAL PROTEOME PROFILING

Abstract Senescent cell accumulation is a known driver of aging and age-related pathologies. Clearance of senescent cells is a promising approach to increase longevity and reduce multiple age-related diseases in humans. Flavonoid compounds are present in fruits and vegetables, of which certain flavonoids (e.g., quercetin and fisetin) have demonstrated senolytic, or ‘senescent-cell-killing’, activity in culture and in mice. However, the cellular mechanism of senolysis and the efficacy of these compounds are not known in renal epithelial cells. Here, we combine flavonoid drug screening, targeted metabolomics, and thermal proteome profiling (TPP) with analysis by mass spectrometry (MS) to explore protein targets of senolytic drugs in senescent human renal cortical epithelial cells and human renal proximal tubular epithelial cells. Senescence was induced by exposure to ionizing radiation and the senescence phenotype was validated through a rigorous panel of senescence and viability markers. Proliferating and senescent renal epithelial cells were screened with a panel of 8 flavonoids to identify senolytic drugs and their concentrations for selectively killing senescent cells. Targeted MS assays were developed to assess intracellular drug uptake, a potential mechanism of senescent-specific killing. To identify protein targets of the senolytic flavonoids in senescent cells, we performed a variation of TPP in combination with liquid chromatography (LC)-MS/MS proteomics analysis, carefully controlling for non-senolytic interactions by excluding proteins bound by a non-senolytic flavonoid. The results of this study pave the way for the development of a more specific generation of senolytic compounds and identify novel candidate senolytic pathways engaged by dietary flavonoids.

Elimination of Senescent Osteocytes by Bone-Targeting Delivery of β-Galactose-Modified Maytansinoid Prevents Age-Related Bone Loss.

The accumulation of senescent cells in bone during aging contributes to senile osteoporosis, and clearance of senescent cells by senolytics could effectively alleviate bone loss. However, the applications of senolytics are limited due to their potential toxicities. Herein, small extracellular vesicles (sEVs) have been modified by incorporating bone-targeting peptide, specifically (AspSerSer)6, to encapsulate galactose-modified Maytansinoids (DM1). These modified vesicles are referred to as (AspSerSer)6-sEVs/DM1-Gal, and they have been designed to specifically clear the senescent osteocytes in bone tissue. In addition, the elevated activity of lysosomal β-galactosidase in senescent osteocytes, but not normal cells in bone tissue, could break down DM1-Gal to release free DM1 for selective elimination of senescent osteocytes. Mechanically, DM1 could disrupt tubulin polymerization, subsequently inducing senescent osteocytes apoptosis. Further, administration of bone-targeting senolytics to aged mice could alleviate aged-related bone loss without non-obvious toxicity. Overall, this bone-targeting senolytics could act as a novel candidate for specific clearance of senescent osteocytes, ameliorating age-related bone loss, with a promising therapeutic potential for senile osteoporosis.

Organogermanium, Ge-132, promotes the clearance of senescent red blood cells via macrophage-mediated phagocyte activation

Red blood cells (RBCs) are renewed in a cyclic manner. Aging RBCs are captured and degraded by phagocytic cells, and heme metabolic pigments are subsequently excreted in feces. We evaluated the effect of an organogermanium compound on RBC metabolism and found that the phagocytosis of RAW264.7 macrophage-like cells was increased by treatment with 3-(trihydroxygermyl)propanoic acid (THGP). Additionally, consumption of Ge-132 (a dehydrate polymer of THGP) changed the fecal color to bright yellow and increased the erythrocyte metabolic pigment levels and antioxidant activity in feces. These data suggest that Ge-132 may activate macrophages in the body and promote the degradation of aged RBCs. Furthermore, Ge-132 intake promoted not only increases in RBC degradation but also the induction of erythroblast differentiation in bone marrow cells. The normal hematocrit levels were maintained due to the maintenance of homeostasis, even though Ge-132 ingestion increased erythrocyte degradation. Therefore, Ge-132 enhances the degradation of senescent RBCs by macrophages. In turn, RBC production is increased to compensate for the amount of degradation, and RBC metabolism is increased.

Platelets mediate the clearance of senescent red blood cells by forming prophagocytic platelet-cell complexes

AbstractIn humans, ∼0.1% to 0.3% of circulating red blood cells (RBCs) are present as platelet-RBC (P-RBC) complexes, and it is 1% to 2% in mice. Excessive P-RBC complexes are found in diseases that compromise RBC health (eg, sickle cell disease and malaria) and contribute to pathogenesis. However, the physiological role of P-RBC complexes in healthy blood is unknown. As a result of damage accumulated over their lifetime, RBCs nearing senescence exhibit physiological and molecular changes akin to those in platelet-binding RBCs in sickle cell disease and malaria. Therefore, we hypothesized that RBCs nearing senescence are targets for platelet binding and P-RBC formation. Confirming this hypothesis, pulse-chase labeling studies in mice revealed an approximately tenfold increase in P-RBC complexes in the most chronologically aged RBC population compared with younger cells. When reintroduced into mice, these complexes were selectively cleared from the bloodstream (in preference to platelet-free RBC) through the reticuloendothelial system and erythrophagocytes in the spleen. As a corollary, patients without a spleen had higher levels of complexes in their bloodstream. When the platelet supply was artificially reduced in mice, fewer RBC complexes were formed, fewer erythrophagocytes were generated, and more senescent RBCs remained in circulation. Similar imbalances in complex levels and senescent RBC burden were observed in humans with immune thrombocytopenia (ITP). These findings indicate that platelets are important for binding and clearing senescent RBCs, and disruptions in platelet count or complex formation and clearance may negatively affect RBC homeostasis and may contribute to the known risk of thrombosis in ITP and after splenectomy.

Effects of senescence on the tumour microenvironment and response to therapy.

Cellular senescence is a state of durable cell arrest that has been identified both in vitro and in vivo. It is associated with profound changes in gene expression and a specific secretory profile that includes pro-inflammatory cytokines, growth factors and matrix-remodelling enzymes, referred to as the senescence-associated secretory phenotype (SASP). In cancer, senescence can have anti- or pro-tumour effects. On one hand, it can inhibit tumour progression in a cell autonomous manner. On the other hand, senescence can also promote tumour initiation, progression, metastatic dissemination and resistance to therapy in a paracrine manner. Therefore, despite efforts to target senescence as a potential strategy to inhibit tumour growth, senescent cancer and microenvironmental cells can eventually lead to uncontrolled proliferation and aggressive tumour phenotypes. This can happen either through overcoming senescence growth arrest or through SASP-mediated effects in adjacent tumour cells. This review will discuss how senescence affects the tumour microenvironment, including extracellular matrix remodelling, the immune system and the vascular compartment, to promote tumourigenesis, metastasis and resistance to DNA-damaging therapies. It will also discuss current approaches used in the field to target senescence: senolytics, improving the immune clearance of senescent cells and targeting the SASP.

Senolytic treatment reduces oxidative protein stress in an aging male murine model of post-traumatic osteoarthritis.

Senolytic drugs are designed to selectively clear senescent cells (SnCs) that accumulate with injury or aging. In a mouse model of osteoarthritis (OA), senolysis yields a pro-regenerative response, but the therapeutic benefit is reduced in aged mice. Increased oxidative stress is a hallmark of advanced age. Therefore, here we investigate whether senolytic treatment differentially affects joint oxidative load in young and aged animals. We find that senolysis by a p53/MDM2 interaction inhibitor, UBX0101, reduces protein oxidative modification in the aged arthritic knee joint. Mass spectrometry coupled with protein interaction network analysis and biophysical stability prediction of extracted joint proteins revealed divergent responses to senolysis between young and aged animals, broadly suggesting that knee regeneration and cellular stress programs are contrarily poised to respond as a function of age. These opposing responses include differing signatures of protein-by-protein oxidative modification and abundance change, disparate quantitative trends in modified protein network centrality, and contrasting patterns of oxidation-induced folding free energy perturbation between young and old. We develop a composite sensitivity score to identify specific key proteins in the proteomes of aged osteoarthritic joints, thereby nominating prospective therapeutic targets to complement senolytics.

Death-seq identifies regulators of cell death and senolytic therapies

Selectively ablating damaged cells is an evolving therapeutic approach for age-related disease. Current methods for genome-wide screens to identify genes whose deletion might promote the death of damaged or senescent cells are generally underpowered because of the short timescales of cell death as well as the difficulty of scaling non-dividing cells. Here, we establish "Death-seq," a positive-selection CRISPR screen optimized to identify enhancers and mechanisms of cell death. Our screens identified synergistic enhancers of cell death induced by the known senolytic ABT-263. The screen also identified inducers of cell death and senescent cell clearance in models of age-related diseases by a related compound, ABT-199, which alone is not senolytic but exhibits less toxicity than ABT-263. Death-seq enables the systematic screening of cell death pathways to uncover molecular mechanisms of regulated cell death subroutines and identifies drug targets for the treatment of diverse pathological states such as senescence, cancer, and fibrosis.

Cellular senescence primes liver fibrosis regression through Notch-EZH2.

Cellular senescence plays a pivotal role in wound healing. At the initiation of liver fibrosis regression, accumulated senescent cells were detected and genes of senescence were upregulated. Flow cytometry combined with single-cell RNA sequencing analyses revealed that most of senescent cells were liver nonparenchymal cells. Removing senescent cells by dasatinib and quercetin (DQ), alleviated hepatic cellular senescence, impeded fibrosis regression, and disrupted liver sinusoids. Clearance of senescent cells not only decreased senescent macrophages but also shrank the proportion of anti-inflammatory M2 macrophages through apoptotic pathway. Subsequently, macrophages were depleted by clodronate, which diminished hepatic senescent cells and impaired fibrosis regression. Mechanistically, the change of the epigenetic regulator enhancer of zeste homolog2 (EZH2) accompanied with the emergence of hepatic senescent cells while liver fibrosis regressed. Blocking EZH2 signaling by EPZ6438 reduced hepatic senescent cells and macrophages, decelerating liver fibrosis regression. Moreover, the promoter region of EZH2 was transcriptionally suppressed by Notch-Hes1 (hairy and enhancer of split 1) signaling. Disruption of Notch in macrophages using Lyz2 (lysozyme 2) Cre-RBP-J (recombination signal binding protein Jκ) f/f transgenic mice, enhanced hepatic cellular senescence, and facilitated fibrosis regression by upregulating EZH2 and blocking EZH2 abrogated the above effects caused by Notch deficiency. Ultimately, adopting Notch inhibitor Ly3039478 or exosome-mediated RBP-J decoy oligodeoxynucleotides accelerated liver fibrosis regression by augmenting hepatic cellular senescence.

Cellular Senescence Contributes to Large Elastic Artery Stiffening and Endothelial Dysfunction With Aging: Amelioration With Senolytic Treatment.

Here, we assessed the role of cellular senescence and the senescence associated secretory phenotype (SASP) in age-related aortic stiffening and endothelial dysfunction. We studied young (6-8 mo) and old (27-29 mo) p16-3MR mice, which allows for genetic-based clearance of senescent cells with ganciclovir (GCV). We also treated old C57BL/6N mice with the senolytic ABT-263. In old mice, GCV reduced aortic stiffness assessed by aortic pulse wave velocity (PWV; 477±10 vs. 382±7 cm/s, P<0.05) to young levels (old-GCV vs. young-vehicle, P=0.35); ABT-263 also reduced aortic PWV in old mice (446±9 to 356±11 cm/s, P<0.05). Aortic adventitial collagen was reduced by GCV (P<0.05) and ABT-263 (P=0.12) in old mice. To show an effect of the circulating SASP, we demonstrated that plasma exposure from Old-vehicle p16-3MR mice, but not from Old-GCV mice, induced aortic stiffening assessed ex vivo (elastic modulus; P<0.05). Plasma proteomics implicated glycolysis in circulating SASP-mediated aortic stiffening. In old p16-3MR mice, GCV increased endothelial function assessed via peak carotid artery endothelium-dependent dilation (EDD; Old-GCV, 94±1% vs. Old-vehicle, 84±2%, P<0.05) to young levels (Old-GCV vs. young-vehicle, P=0.98), and EDD was higher in old C57BL/6N mice treated with ABT-263 vs. vehicle (96±1% vs. 82±3%, P<0.05). Improvements in endothelial function were mediated by increased nitric oxide (NO) bioavailability (P<0.05) and reduced oxidative stress (P<0.05). Circulating SASP factors related to NO signaling were associated with greater NO-mediated EDD following senescent cell clearance. Cellular senescence and the SASP contribute to vascular aging and senolytics hold promise for improving age-related vascular function.

End-Stage Idiopathic Pulmonary Fibrosis Lung Microenvironment Promotes Impaired NK Activity.

Idiopathic pulmonary fibrosis (IPF) is a fibrotic age-related chronic lung disease characterized by the accumulation of senescent cells. Whether impaired immune response is responsible for the accumulation of senescent cells in the IPF lung remains unknown. In this study, we characterized the NK phenotype in IPF lungs via flow cytometry using 5-dodecanoylaminofluorescein di-β-d-galactopyranoside, markers of tissue residence, and chemokine receptors. The effect of the lung microenvironment was evaluated using lung fibroblast (LF) conditioned media (CM), and the bleomycin-induced pulmonary fibrosis mouse model was used to assess the invivo relationship between NK cells and the accumulation of senescent cells. We found that NK cells from the lower lobe of IPF patients exhibited immune-senescent and impaired CD57-NKG2A+ phenotype. We also observed that culture of NK cells from healthy donors in CM from IPF lower lobe lung fibroblasts induced a senescent-like phenotype and impaired cytotoxic capacity. There is an impaired NK recruitment by LF, and NKs presented decreased migration toward their CM. In addition, NK cell-depleted mice treated with bleomycin showed increased collagen deposition and accumulation of different populations of senescent cells compared with controls. The IPF lung microenvironment induces a dysfunctional NK phenotype limiting the clearance of lung senescent cells and the resolution of lung fibrosis. We propose that impaired NK activity could be one of the mechanisms responsible for perpetuating the accumulation of senescent cells in IPF lungs.

Clearance of defective muscle stem cells by senolytics restores myogenesis in myotonic dystrophy type 1

Muscle stem cells, the engine of muscle repair, are affected in myotonic dystrophy type 1 (DM1); however, the underlying molecular mechanism and the impact on the disease severity are still elusive. Here, we show using patients’ samples that muscle stem cells/myoblasts exhibit signs of cellular senescence in vitro and in situ. Single cell RNAseq uncovers a subset of senescent myoblasts expressing high levels of genes related to the senescence-associated secretory phenotype (SASP). We show that the levels of interleukin-6, a prominent SASP cytokine, in the serum of DM1 patients correlate with muscle weakness and functional capacity limitations. Drug screening revealed that the senolytic BCL-XL inhibitor (A1155463) can specifically remove senescent DM1 myoblasts by inducing their apoptosis. Clearance of senescent cells reduced the expression of SASP, which rescued the proliferation and differentiation capacity of DM1 myoblasts in vitro and enhanced their engraftment following transplantation in vivo. Altogether, this study identifies the pathogenic mechanism associated with muscle stem cell defects in DM1 and opens a therapeutic avenue that targets these defective cells to restore myogenesis.

P-349 Modelling the impact of acute and chronic decidual senescence on endometrial stemness in 3D assembloids

Abstract Study question Is de-differentiation of committed endometrial stromal and epithelial cells in response to decidual senescence involved in regulating stemness of cycling human endometrium? Summary answer Transient decidual senescence promotes endometrial tissue rejuvenation by reprogramming stromal and epithelial cells into progenitor stem-like cells whereas chronic senescence causes stem cell depletion. What is known already In wound healing, acute but not prolonged senescence, a cellular state characterised by permanent cell cycle arrest and production of a complex secretome rich in inflammatory mediators, ECM proteins and proteinases, growth factors and angiogenic modulators, has been shown to promote de-differentiation of committed cells into stem-like progenitors, thereby enhancing tissue regeneration upon immune clearance of senescent cells. Menstrual repair depends on endometrial progenitor cells but whether they represent stromal and epithelial cells that have de-differentiated in response to acute premenstrual decidual senescence is not known. Study design, size, duration Endometrial 'instant' assembloids, consisting of gland organoids and primary stromal cells in collagen hydrogels, were established from freshly isolated cells from mid-luteal endometrial biopsies. The assembloids were then subjected over 36 days to 4 cycles of decidualization, a process associated with acute inflammatory senescence, followed by hormonal withdrawal. To induce chronic senescence, assembloids were decidualized continuously for 14 days. Stemness of assembloids was assessed in undifferentiated and decidualized cultures at the end of each ‘cycle’. Participants/materials, setting, methods 'Instant' assembloids, which closely recapitulate native endometrium, were established in collagen hydrogels from 10 midluteal biopsies and subjected to cyclical or prolonged decidualization. Decidualization was monitored by RT-qPCR analysis, using epithelial and stromal cells isolated at regular timepoints. The level of stemness of stromal and epithelial cells was measured by colony-forming unit (CFU) and organoid formation efficacy (OFE) assays, respectively. Main results and the role of chance Repeated cycles of hormonal stimulation and withdrawal resulted in cyclical decidualization of instant assembloids, as characterised by the induction of decidual stromal (PRL, SCARA5 and DIO2) and epithelial (PAEP and SPP1) marker genes when compared to parallel undifferentiated assembloids. Cyclicity enabled cells to maintain a healthy state and preserved the structural integrity of the assembloids. Further, cyclical decidualization of assembloids enhanced CFU activity and OFE activity of stromal and epithelial cells, respectively, indicative of active de-differentiation of committed cells. By contrast, chronic senescence, as induced by a prolonged decidualization, resulted in stem cell depletion in both glandular and stromal compartments and progressive loss of structural integrity of assembloids. We observed a reduced expression of the decidual marker gene PRL and an enhanced expression of IGFBP1 representing the increased stress state of cells. Taken together, induction of acute decidual senescence resulted in a robust de-differentiation response and increased abundance of stromal and epithelial progenitor cells, whereas prolonged senescence caused stem cell exhaustion in both cellular compartments. Limitations, reasons for caution Although the cellular responses observed in our ‘instant’ assembloid model were robust, caution is warranted when extrapolating from in vitro observations. Further, although the ‘instant’ assembloid model enables co-culturing of endometrial endothelial and immune cells, current hydrogels greatly limit their migratory capacity. The mechanisms of cellular de-differentiation are incompletely understood. Wider implications of the findings Our findings indicate that the level of premenstrual decidual senescence in the superficial layer regulates stemness in the basal layer, thus ensuring inter-cycle endometrial homeostasis. Conversely, prolonged decidual senescence associated with clinical miscarriages may plausibly increase the risk of further pregnancy loss by depleting stemness of the regenerative basal layer. Trial registration number N/A

A short dasatinib and quercetin treatment is sufficient to reinstate potent adult neuroregenesis in the aged killifish

The young African turquoise killifish has a high regenerative capacity, but loses it with advancing age, adopting several aspects of the limited form of mammalian regeneration. We deployed a proteomic strategy to identify pathways that underpin the loss of regenerative power caused by aging. Cellular senescence stood out as a potential brake on successful neurorepair. We applied the senolytic cocktail Dasatinib and Quercetin (D + Q) to test clearance of chronic senescent cells from the aged killifish central nervous system (CNS) as well as rebooting the neurogenic output. Our results show that the entire aged killifish telencephalon holds a very high senescent cell burden, including the parenchyma and the neurogenic niches, which could be diminished by a short-term, late-onset D + Q treatment. Reactive proliferation of non-glial progenitors increased substantially and lead to restorative neurogenesis after traumatic brain injury. Our results provide a cellular mechanism for age-related regeneration resilience and a proof-of-concept of a potential therapy to revive the neurogenic potential in an already aged or diseased CNS.

#6095 TRANSGENIC INDUCTION OF EPITHELIAL SENESCENCE PROMOTES RENAL FIBROSIS INDEPENDENT OF INJURY

Abstract Background and Aims Chronic Kidney Disease (CKD) affects over 850 million people worldwide. Progressive renal fibrosis is a hallmark of CKD, irrespective of the initiating aetiology. Any episode of acute kidney injury (AKI) significantly increases the risk of development of CKD, even after apparent complete resolution of the initiating injury. This risk is exacerbated by age and pre-existing CKD. This implies that factors persist within damaged/aging kidneys which drive functional loss, impair complete repair and promote on-going fibrosis. Senescent cells (SCs) are metabolically active, permanently growth arrested cells produced in response to stress and DNA damage. SCs accumulate with age and persist at the sites of previous disease and injury. Their depletion in animal models is safe and extends organ function and healthspan. We have shown that pharmacological SC depletion in kidneys significantly improves kidney function and reduces fibrosis post injury. However, models of renal injury induce changes in multiple cell lineages, and pharmacological depletion is non-specific both in terms of cell lineage (i.e. epithelial vs mesenchymal vs leukocyte) and characteristics of senescent cell (i.e. acute vs chronic, primary vs secondary). We hypothesised that induction of epithelial senescence in the absence of other renal injuries is sufficient to initiate renal fibrosis. We developed a transgenic mouse allowing selective senescence induction in renal epithelia in the absence of injury, with tdTomato labelling of induced cells. Method By crossing existing strains, we produced a triple transgenic Pax8creERT2/mdm2flfl/tdTOMLSL mouse allowing conditional senescence induction by tamoxifen via mdm2 deletion in Pax8 expressing renal epithelia, alongside TdTomato expression. Levels of renal fibrosis, p21cip1 and TdTomato induction were quantified by picrosirius red staining, immunofluorescence and flow cytometry, with downstream image analysis on QuPath 0.3.2. CDKN1A gene expression was quantified by qPCR. Results Examination of kidneys and livers from young mice ± tamoxifen demonstrated that tdTomato induction was tissue specific and restricted to renal epithelia (Fig 1A-C). Administration of Tamoxifen resulted in increased expression of tdTomato and CDKN1A expression at day 7 in transgenic but not in WT mice. (Fig. 1C, 2 A-F). We observed a rapid induction of fibrosis in the first 7 days after tamoxifen induction in both young (Fig. 3A,C) and old mice (Fig 3C). This persists to day 42 (Fig. 3B). This demonstrated that epithelial senescence alone was sufficient to induce renal fibrosis in young mice, and exacerbate fibrosis in old mice. Further studies assessed the longer-term impact of acute senescence induction, with fibrosis stabilising in both young and old mice at 6 weeks post induction (Fig. 3D). Conclusion Using a novel transgenic mouse line, we demonstrate for the first time that induction of renal epithelial senescence in the absence of injury is sufficient to induce renal fibrosis in the early aftermath of SC induction. The evolution and/or clearance of senescent cells over time is the focus of on-going study and will be presented at the ERA.

Clearance of senescent cells reverts the cigarette smoke-induced lung senescence and airspace enlargement in p16-3MR mice.

Cigarette smoke (CS) leads to increased oxidative stress, inflammation, and exaggerated senescence, which are involved in the pathogenesis of chronic obstructive pulmonary disease (COPD). While the role of cellular senescence in COPD is known, it is not clear if the removal of senescent cells could alleviate the disease symptoms. To test this, we used the novel mouse model-p16-3MR, and studied the effect of ganciclovir (GCV)-mediated removal of senescent cells after chronic CS (3 months) and environmental tobacco smoke (ETS) (6 months) exposure to CS. Our results showed the reversal of CS-induced cellular senescence on the clearance of p16+ senesced cells by GCV treatment. Interestingly, the clearance of p16+ senescent cells via GCV led to a decrease in the neutrophil counts in the BALF of GCV-treated CS-exposed p16-3MR mice, as well as reversal of CS-mediated airspace enlargement in p16-3MR mice. Mice exposed to low dose ETS caused insignificant changes in the SA-β-Gal+ senescent cells and airspace enlargement. Overall, our data provideevidence for the role of lung cellular senescence on smoke exposure and clearance of senescent cells in p16-3MR mice in the reversal of COPD/emphysema pathology with a possibility of senolytics as therapeutic interventions in COPD.

Local senolysis in aged mice only partially replicates the benefits of systemic senolysis.

Clearance of senescent cells (SnCs) can prevent several age-related pathologies, including bone loss. However, the local versus systemic roles of SnCs in mediating tissue dysfunction remain unclear. Thus, we developed a mouse model (p16-LOX-ATTAC) that allowed for inducible SnC elimination (senolysis) in a cell-specific manner and compared the effects of local versus systemic senolysis during aging using bone as a prototype tissue. Specific removal of Sn osteocytes prevented age-related bone loss at the spine, but not the femur, by improving bone formation without affecting osteoclasts or marrow adipocytes. By contrast, systemic senolysis prevented bone loss at the spine and femur and not only improved bone formation, but also reduced osteoclast and marrow adipocyte numbers. Transplantation of SnCs into the peritoneal cavity of young mice caused bone loss and also induced senescence in distant host osteocytes. Collectively, our findings provide proof-of-concept evidence that local senolysis has health benefits in the context of aging, but, importantly, that local senolysis only partially replicates the benefits of systemic senolysis. Furthermore, we establish that SnCs, through their senescence-associated secretory phenotype (SASP), lead to senescence in distant cells. Therefore, our study indicates that optimizing senolytic drugs may require systemic instead of local SnC targeting to extend healthy aging.

Targeting senescent dermal fibroblasts responsible for hyperactive melanocytes in melasma

Targeting senescent dermal fibroblasts responsible for hyperactive melanocytes in melasma

Dasatinib Attenuates Fibrosis in Keloids by Decreasing Senescent Cell Burden

Keloids are skin tumours caused by aberrant growth of dermal fibroblasts. Cellular senescence contributes to aging and various pathological conditions, including cancer, atherosclerosis, and fibrotic diseases. However, the effects of cellular senescence and senolytic drugs on keloids remain largely unknown. This study investigated senescent fibroblasts in keloids and assessed the effects of dasatinib on these cells. Tissues acquired from keloid removal surgery were analysed for senescence-associated β-galactosidase-positive cells, p16 expression, and the effects of dasatinib treatment on keloids. Keloid tissue was xenotransplanted into mice, and the effect of intralesional dasatinib injection on keloid growth was observed. The results showed that the numbers of β-galactosidase-positive and p16-expressing cells were higher in the keloids compared with in the controls. Dasatinib induced selective clearance of senescent cells and decreased procollagen expression in cultured keloid fibroblasts. In this xenotransplant keloid mouse model, intralesional injection of dasatinib reduced gross keloid tissue weight and the expression of both procollagen and p16. In addition, dasatinib-treated keloid fibroblasts conditioned medium reduced procollagen and p16 expression in cultured keloid fibroblasts. In conclusion, these results suggest that an increased number of senescent fibroblasts may play an important role in the pathogenesis of keloids. Therefore, dasatinib could be an alternative treatment for patients with keloids.