Identification of HSP90 inhibitors as a novel class of senolytics

Podocyte senescence: from molecular mechanisms to therapeutics

As an important component of the glomerular filtration membrane, the state of the podocytes is closely related to kidney function, they are also key cells involved in aging and play a central role in the damage caused by renal aging. Therefore, understanding the aging process of podocytes will allow us to understand their susceptibility to injury and identify targeted protective mechanisms. In fact, the process of physiological aging itself can induce podocyte senescence. Pathological stresses, such as oxidative stress, mitochondrial damage, secretion of senescence-associated secretory phenotype, reduced autophagy, oncogene activation, altered transcription factors, DNA damage response, and other factors, play a crucial role in inducing premature senescence and accelerating aging. Senescence-associated-β-galactosidase (SA-β-gal) is a marker of aging, and β-hydroxybutyric acid treatment can reduce SA-β-gal activity to alleviate cellular senescence and damage. In addition, CCAAT/enhancer-binding protein-α, transforming growth factor-β signaling, glycogen synthase kinase-3β, cycle-dependent kinase, programmed cell death protein 1, and plasminogen activator inhibitor-1 are closely related to aging. The absence or elevation of these factors can affect aging through different mechanisms. Podocyte injury is not an independent process, and injured podocytes interact with the surrounding epithelial cells or other kidney cells to mediate the injury or loss of podocytes. In this review, we discuss the manifestations, molecular mechanisms, biomarkers, and therapeutic drugs for podocyte senescence. We included elamipretide, lithium, calorie restriction, rapamycin; and emerging treatment strategies, such as gene and immune therapies. More importantly, we summarize how podocyte interact with other kidney cells.

Nordihydroguaiaretic acid microparticles are effective in the treatment of osteoarthritis

Several disease-modifying osteoarthritis (OA) drugs have emerged, but none have been approved for clinical use due to their systemic side effects, short half-life, and rapid clearance from the joints. Nordihydroguaiaretic acid (NDGA), a reactive oxygen species (ROS) scavenger and autophagy inducer, could be a potential treatment for OA. In this report, we show for the first time that sustained delivery of NDGA through polymeric microparticles maintains therapeutic concentrations of drug in the joint and ameliorates post-traumatic OA (PTOA) in a mouse model. In vitro treatment of oxidatively stressed primary chondrocytes from OA patients using NDGA-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles (NDGA-MP) inhibited 15-lipoxygenase, induced autophagy, prevented chondrosenescence, and sustained matrix production. In vivo intra-articular delivery of NDGA-MP was non-toxic and had prolonged retention time (up to 35 days) in murine knee joints. Intra-articular therapy using NDGA-MP effectively reduced cartilage damage and reduced pain in the surgery-induced PTOA mouse model. Our studies open new avenues to modulate the immune environment and treat post-traumatic OA using ROS quenchers and autophagy inducers.

Therapeutic targeting of senescent cells in the CNS

Senescent cells accumulate throughout the body with advanced age, diseases and chronic conditions. They negatively impact health and function of multiple systems, including the central nervous system (CNS). Therapies that target senescent cells, broadly referred to as senotherapeutics, recently emerged as potentially important treatment strategies for the CNS. Promising therapeutic approaches involve clearing senescent cells by disarming their pro-survival pathways with 'senolytics'; or dampening their toxic senescence-associated secretory phenotype (SASP) using 'senomorphics'. Following the pioneering discovery of first-generation senolytics dasatinib and quercetin, dozens of additional therapies have been identified, and several promising targets are under investigation. Although potentially transformative, senotherapies are still in early stages and require thorough testing to ensure reliable target engagement, specificity, safety and efficacy. The limited brain penetrance and potential toxic side effects of CNS-acting senotherapeutics pose challenges for drug development and translation to the clinic. This Review assesses the potential impact of senotherapeutics for neurological conditions by summarizing preclinical evidence, innovative methods for target and biomarker identification, academic and industry drug development pipelines and progress in clinical trials.

Hypoxia and aging: molecular mechanisms, diseases, and therapeutic targets

Aging is a complex biological process characterized by the gradual decline of cellular functions, increased susceptibility to diseases, and impaired stress responses. Hypoxia, defined as reduced oxygen availability, is a critical factor that influences aging through molecular pathways involving hypoxia-inducible factors (HIFs), oxidative stress, inflammation, and epigenetic modifications. This review explores the interconnected roles of hypoxia in aging, highlighting how hypoxic conditions exacerbate cellular damage, promote senescence, and contribute to age-related pathologies, including cardiovascular diseases, neurodegenerative disorders, cancer, metabolic dysfunctions, and pulmonary conditions. By examining the molecular mechanisms linking hypoxia to aging, we identify key pathways that serve as potential therapeutic targets. Emerging interventions such as HIF modulators, antioxidants, senolytics, and lifestyle modifications hold promise in mitigating the adverse effects of hypoxia on aging tissues. However, challenges such as the heterogeneity of aging, lack of reliable biomarkers, and safety concerns regarding hypoxia-targeted therapies remain. This review emphasizes the need for personalized approaches and advanced technologies to develop effective antiaging interventions. By integrating current knowledge, this review provides a comprehensive framework that underscores the importance of targeting hypoxia-induced pathways to enhance healthy aging and reduce the burden of age-related diseases.

Targeting senescent cells in atherosclerosis: Pathways to novel therapies

Targeting senescent cells has recently emerged as a promising strategy for treating age-related diseases, such as atherosclerosis, which significantly contributes to global cardiovascular morbidity and mortality. This review elucidates the role of senescent cells in the development of atherosclerosis, including persistently damaging DNA, inducing oxidative stress and secreting pro-inflammatory factors known as the senescence-associated secretory phenotype. Therapeutic approaches targeting senescent cells to mitigate atherosclerosis are summarized in this review, which include the development of senotherapeutics and immunotherapies. These therapies are designed to either remove these cells or suppress their deleterious effects. These emerging therapies hold potential to decelerate or even alleviate the progression of AS, paving the way for new avenues in cardiovascular research and treatment.

Aging, senescence, and cutaneous wound healing-a complex relationship

Cutaneous wound healing is a complex multi-step process that is highly controlled, ensuring efficient repair to damaged tissue and restoring tissue architecture. Multiple cell types play a critical role in wound healing, and perturbations in this can lead to non-healing wounds or scarring and fibrosis. Thus, the process is tightly regulated and controlled. Cellular senescence is defined as irreversible cell cycle arrest and is associated with various phenotypic changes and metabolic alterations and coupled to a secretory program. Its role in wound healing, at least in the acute setting, appears to help promote appropriate mechanisms leading to the complete restoration of tissue architecture. Opposing this is the role of senescence in chronic wounds where it can lead to either chronic non-healing wounds or fibrosis. Given the two opposing outcomes of wound healing in either acute or chronic settings, this has led to disparate views on the role of senescence in wound healing. This review aims to consolidate knowledge on the role of senescence and aging in wound healing, examining the nuances of the roles in the acute or chronic settings, and attempts to evaluate the modulation of this to promote efficient wound healing.

Identification of lipid senolytics targeting senescent cells through ferroptosis induction

Cellular senescence is a key driver of the aging process and contributes to tissue dysfunction and age-related pathologies. Senolytics have emerged as a promising therapeutic intervention to extend healthspan and treat age-related diseases. Through a senescent cell-based phenotypic drug screen, we identified a class of conjugated polyunsaturated fatty acids, specifically α-eleostearic acid and its methyl ester derivative, as novel senolytics that effectively killed a broad range of senescent cells, reduced tissue senescence, and extended healthspan in mice. Importantly, these novel lipids induced senolysis through ferroptosis, rather than apoptosis or necrosis, by exploiting elevated iron, cytosolic PUFAs and ROS levels in senescent cells. Mechanistic studies and computational analyses further revealed their key targets in the ferroptosis pathway, ACSL4, LPCAT3, and ALOX15, important for lipid-induced senolysis. This new class of ferroptosis-inducing lipid senolytics provides a novel approach to slow aging and treat age-related disease, targeting senescent cells that are primed for ferroptosis.

New Mitochondria-Targeted Fisetin Derivative Compromises Mitophagy and Limits Survival of Drug-Induced Senescent Breast Cancer Cells

Mitochondria are considered as promising targets for cancer treatment. In the present study, triphenyl phosphonium cationic group-conjugated fisetin (mito-fisetin) was synthesized, and its anticancer activity was investigated in several cellular models of estrogen receptor (ER)-positive breast cancer in vitro and in vivo in proliferating and tamoxifen-promoted senescent states. Mito-fisetin, when used at low micromolar concentrations, stimulated the dissipation of mitochondrial membrane potential and oxidative stress, and affected mitochondrial function, resulting in apoptosis induction in senescent breast cancer cells. Mito-fisetin-mediated cytotoxicity was due to increased levels of phosphorylated AMPK, decreased levels of AKT and HSP90, and impaired mitophagic response, as judged by the analysis of the markers of mitophagosome formation. Senescent breast cancer cells were found to be more sensitive to mito-fisetin treatment than proliferating ones. We postulate that mitochondrial targeting in the case of fisetin may be considered as a promising anticancer and senotherapeutic strategy to eliminate drug-resistant senescent breast cancer cells.

Advances in targeted therapies for age-related osteoarthritis: A comprehensive review of current research

Osteoarthritis (OA) is a common degenerative joint disease that disproportionately impacts the elderly population on a global scale. As aging is a significant risk factor for OA, there is a growing urgency to develop specific therapies that target the underlying mechanisms of aging associated with this condition. This summary seeks to offer a thorough introduction of ongoing research efforts aimed at developing therapies to combat senescence in the context of OA. Cellular senescence plays a pivotal role in both the deterioration of cartilage integrity and the perpetuation of chronic inflammation and tissue remodeling. Consequently, targeting SnCs has emerged as a promising therapeutic approach to alleviate symptoms and hinder the progression of OA. This review examines a range of approaches, including senolytic drugs targeting SnCs, senomorphics that modulate the senescence-associated secretory phenotype (SASP), and interventions that enhance immune system clearance of SnCs. Novel methodologies, such as utilizing novel materials for exosome delivery and administering anti-aging medications with precision, offer promising avenues for the precise treatment of OA. Accumulating evidence underscores the potential of targeting senescence in OA management, potentially facilitating the development of more effective and personalized therapeutic interventions.

The Gehan test identifies life-extending compounds overlooked by the log-rank test in the NIA Interventions Testing Program: Metformin, Enalapril, caffeic acid phenethyl ester, green tea extract, and 17-dimethylaminoethylamino-17-demethoxygeldanamycin hydrochloride

The National Institute on Aging Interventions Testing Program (ITP) has so far identified 12 compounds that extend the lifespan of genetically heterogeneous mice using the log-rank test. However, the log-rank test is relatively insensitive to any compound that does not uniformly reduce mortality across the lifespan. This test may thus miss compounds that only reduce mortality before midlife, for example, a plausible outcome if a compound only mitigates risk factors before midlife or if its efficacy is reduced at later ages. We therefore reanalyzed all data collected by the ITP from 2004-2022 using the Gehan test, which is more sensitive to mortality differences earlier in the life course and does not assume a uniformly reduced mortality hazard across the lifespan. The Gehan test identified 5 additional compounds, metformin, enalapril, 17-dimethylaminoethylamino-17-demethoxygeldanamycin hydrochloride (17-DMAG), caffeic acid phenethyl ester (CAPE), and green tea extract (GTE), which significantly increased survival but were previously missed by the log-rank test. Three (metformin, enalapril, and 17-DMAG) were only effective in males and two (CAPE and GTE) were only effective in females. In addition, 1,3-butanediol, which by log-rank analysis increased survival in females but not males, increased survival in males by the Gehan test. These results suggest that statistical tests sensitive to non-uniformity of drug efficacy across the lifespan should be included in the standard statistical testing protocol to minimize overlooking geroprotective interventions.

Cellular senescence: A novel therapeutic target for central nervous system diseases

The underlying mechanisms of diseases affecting the central nervous system (CNS) remain unclear, limiting the development of effective therapeutic strategies. Remarkably, cellular senescence, a biological phenomenon observed in cultured fibroblasts in vitro, is a crucial intrinsic mechanism that influences homeostasis of the brain microenvironment and contributes to the onset and progression of CNS diseases. Cellular senescence has been observed in disease models established in vitro and in vivo and in bodily fluids or tissue components from patients with CNS diseases. These findings highlight cellular senescence as a promising target for preventing and treating CNS diseases. Consequently, emerging novel therapies targeting senescent cells have exhibited promising therapeutic effects in preclinical and clinical studies on aging-related diseases. These innovative therapies can potentially delay brain cell loss and functional changes, improve the prognosis of CNS diseases, and provide alternative treatments for patients. In this study, we examined the relevant advancements in this field, particularly focusing on the targeting of senescent cells in the brain for the treatment of chronic neurodegenerative diseases (e.g., Alzheimer's disease, Parkinson's disease, and multiple sclerosis) and acute neurotraumatic insults (e.g., ischemic stroke, spinal cord injury, and traumatic brain injury).

Cutting-edge skin ageing research on tissue stem cell

In developed economies, the growing number of older individuals is a pressing issue. As a result, research progress into ageing has emphasized the significance of staying healthy in one's later years. Stem cells have a fundamental role to play in fostering diverse cell types and necessary processes for tissue repair and regeneration. Stem cells experience the effects of ageing over time, which is caused by their functional deterioration. Changes to stem cells, their niches and signals from other tissues they interact with are crucial factors in the ageing of stem cells. Progress in single-cell RNA sequencing (scRNA-seq) technology has greatly advanced stem cell research. This review examines the mechanisms of stem cell ageing, its impact on health and investigates the potential of stem cell therapy, with a special emphasis on the skin.

Identification of novel inhibitors of the transcriptional coactivator MRTF-A for HCC therapy

Myocardin-related transcription factor A (MRTF-A) is a coactivator of serum response factor (SRF), which regulates the expression of genes involved in cell proliferation, migration, and differentiation and has been implicated in hepatocellular carcinoma (HCC) progression. We recently established inhibition of the transcriptional activity of MRTF-A by NS8593 as a novel therapeutic approach for HCC therapy. NS8593 is a negative gating modulator of the transient receptor potential cation channel TRPM7. In this report, we identify an aminobenzimidazole that is highly potent in inhibiting TRPM7 and its interaction with RhoA, leading to decreased SRF transcriptional activity and enhanced nuclear export of MRTF-A, as determined by fluorescence loss in photobleaching (FLIP). This resulted in reduced expression of the MRTF/SRF target genes transforming growth factor β1 (TGF-β1) and tetraspanin 5 (TSPAN5), senescence induction, and growth arrest in HCC cells. Replacement of the tetraline core by a 3-aminophenyl substructure yielded inhibitor 10 with higher potency than inhibitor 5, and further structural modifications yielded highly potent inhibitors of SRF activity, 14 and 16. Both compounds were capable of inhibiting cell proliferation and inducing senescence in HCC cells with improved efficacy compared to NS8593. These inhibitors represent valuable tools for understanding the molecular basis of drug development targeting TRPM7 and MRTFs.

The Role of Molecular and Cellular Aging Pathways on Age-Related Hearing Loss

Aging, a complex process marked by molecular and cellular changes, inevitably influences tissue and organ homeostasis and leads to an increased onset or progression of many chronic diseases and conditions, one of which is age-related hearing loss (ARHL). ARHL, known as presbycusis, is characterized by the gradual and irreversible decline in auditory sensitivity, accompanied by the loss of auditory sensory cells and neurons, and the decline in auditory processing abilities associated with aging. The extended human lifespan achieved by modern medicine simultaneously exposes a rising prevalence of age-related conditions, with ARHL being one of the most significant. While our understanding of the molecular basis for aging has increased over the past three decades, a further understanding of the interrelationship between the key pathways controlling the aging process and the development of ARHL is needed to identify novel targets for the treatment of AHRL. The dysregulation of molecular pathways (AMPK, mTOR, insulin/IGF-1, and sirtuins) and cellular pathways (senescence, autophagy, and oxidative stress) have been shown to contribute to ARHL. However, the mechanistic basis for these pathways in the initiation and progression of ARHL needs to be clarified. Therefore, understanding how longevity pathways are associated with ARHL will directly influence the development of therapeutic strategies to treat or prevent ARHL. This review explores our current understanding of the molecular and cellular mechanisms of aging and hearing loss and their potential to provide new approaches for early diagnosis, prevention, and treatment of ARHL.

The dual role of cellular senescence in human tumor progression and therapy

Cellular senescence, one of the hallmarks of cancer, is characterized by cell cycle arrest and the loss of most normal cellular functions while acquiring a hypersecretory, proinflammatory phenotype. The function of senescent cells in cancer cells varies depending on the cellular conditions. Before the occurrence of cancer, senescent cells act as a barrier to prevent its development. But once cancer has occurred, senescent cells play a procancer role. However, few of the current studies have adequately explained the diversity of cellular senescence across cancers. Herein, we concluded the latest intrinsic mechanisms of cellular senescence in detail and emphasized the senescence-associated secretory phenotype as a key contributor to heterogeneity of senescent cells in tumor. We also discussed five kinds of inducers of cellular senescence and the advancement of senolytics in cancer, which are drugs that tend to clear senescent cells. Finally, we summarized the various effects of senescent cells in different cancers and manifested that their functions may be diametrically opposed under different circumstances. In short, this paper contributes to the understanding of the diversity of cellular senescence in cancers and provides novel insight for tumor therapy.

Senolytic Therapy Enabled by Senescent Cell-Sensitive Biomimetic Melanin Nano-Senolytics

Cellular senescence is a significant risk factor for aging and age-related diseases (ARD). The canonical senolytics Dasatinib and Quercetin (DQ) have shown promise in clearing senescent cells (SnCs); however, the lack of selectivity poses a challenge in achieving optimal outcomes. Despite the recent occurrence of nanomaterial-based approaches targeting SnCs, limited therapeutic effects, and potential toxicity still remain a major concern. Herein, a "double locks-like" nanoplatform is developed that integrated Galactan coating and mesoporous polydopamine to encase the senolytic drug DQ. By this way, DQ is only released in SnCs that are featured with higher levels of β-galactosidase (β-gal) and low PH. Additionally, the nanoparticles are equipped with 2,2,6,6-Tetramethylpiperidine-1-oxyl (Tempo) to gain enhanced photothermal converting potential. Consequently, the synthesized nanosenolytics demonstrate remarkable specificity and efficacy in eradicating SnCs, and accordingly reverse pulmonary fibrosis in mice without affecting normal tissues. Upon exposure of near-infrared (NIR) light, the nanoparticles demonstrate to efficiently remove senescent tumor cells inducted by chemotherapy, thereby hindering the outgrowth and metastasis or breast cancer. Collectively, the present study develops an "On/Off" switchable nanoplatform in response to SnCs, and produces a more safe, efficient, and feasible way to delay aging or alleviate age-associated diseases.

Senescence- and Immunity-Related Changes in the Central Nervous System: A Comprehensive Review

Senescence is a cellular state characterized by an irreversible halt in the cell cycle, accompanied by alterations in cell morphology, function, and secretion. Senescent cells release a plethora of inflammatory and growth factors, extracellular matrix proteins, and other bioactive substances, collectively known as the senescence-associated secretory phenotype (SASP). These excreted substances serve as crucial mediators of senescent tissues, while the secretion of SASP by senescent neurons and glial cells in the central nervous system modulates the activity of immune cells. Senescent immune cells also influence the physiological activities of various cells in the central nervous system. Further, the interaction between cellular senescence and immune regulation collectively affects the physiological and pathological processes of the central nervous system. Herein, we explore the role of senescence in the physiological and pathological processes underlying embryonic development, aging, degeneration, and injury of the central nervous system, through the immune response. Further, we elucidate the role of senescence in the physiological and pathological processes of the central nervous system, proposing a new theoretical foundation for treating central nervous system diseases.

Senescent endothelial cells: a potential target for diabetic retinopathy

Diabetic retinopathy (DR) is a diabetic complication that results in visual impairment and relevant retinal diseases. Current therapeutic strategies on DR primarily focus on antiangiogenic therapies, which particularly target vascular endothelial growth factor and its related signaling transduction. However, these therapies still have limitations due to the intricate pathogenesis of DR. Emerging studies have shown that premature senescence of endothelial cells (ECs) in a hyperglycemic environment is involved in the disease process of DR and plays multiple roles at different stages. Moreover, these surprising discoveries have driven the development of senotherapeutics and strategies targeting senescent endothelial cells (SECs), which present challenging but promising prospects in DR treatment. In this review, we focus on the inducers and mechanisms of EC senescence in the pathogenesis of DR and summarize the current research advances in the development of senotherapeutics and strategies that target SECs for DR treatment. Herein, we highlight the role played by key factors at different stages of EC senescence, which will be critical for facilitating the development of future innovative treatment strategies that target the different stages of senescence in DR.

Advances in Nanotherapy for Targeting Senescent Cells

Aging is an inevitable process in the human body, and cellular senescence refers to irreversible cell cycle arrest caused by external aging-promoting mechanisms. Moreover, as age increases, the accumulation of senescent cells limits both the health of the body and lifespan and even accelerates the occurrence and progression of age-related diseases. Therefore, it is crucial to delay the periodic irreversible arrest and continuous accumulation of senescent cells to address the issue of aging. The fundamental solution is targeted therapy focused on eliminating senescent cells or reducing the senescence-associated secretory phenotype. Over the past few decades, the remarkable development of nanomaterials has revolutionized clinical drug delivery pathways. Their unique optical, magnetic, and electrical properties effectively compensate for the shortcomings of traditional drugs, such as low stability and short half-life, thereby maximizing the bioavailability and minimizing the toxicity of drug delivery. This article provides an overview of how nanomedicine systems control drug release and achieve effective diagnosis. By presenting and analyzing recent advances in nanotherapy for targeting senescent cells, the underlying mechanisms of nanomedicine for senolytic and senomorphic therapy are clarified, providing great potential for targeting senescent cells.

Investigating the Effects of Chelidonic Acid on Oxidative Stress-Induced Premature Cellular Senescence in Human Skin Fibroblast Cells

This study investigated the effects of chelidonic acid (CA) on hydrogen peroxide (H2O2) induced cellular senescence in human skin fibroblast cells (BJ). Cellular senescence is a critical mechanism that is linked to age-related diseases and chronic conditions. CA, a γ-pyrone compound known for its broad pharmacological activity, was assessed for its potential to mitigate oxidative stress and alter senescence markers. A stress-induced premature senescence (SIPS) model was designed in BJ fibroblast cells using the oxidative stress agent H2O2. After this treatment, cells were treated with CA, and the potential effect of CA on senescence was evaluated using senescence-related β-galactosidase, 4',6-diamino-2-phenylindole (DAPI), acridine-orange staining (AO), comet assay, molecular docking assays, gene expression, and protein analysis. These results demonstrate that CA effectively reduces senescence markers, including senescence-associated β-galactosidase activity, DNA damage, lysosomal activity, and oxidative stress indicators such as malondialdehyde. Molecular docking revealed CA's potential interactions with critical proteins involved in senescence signalling pathways, suggesting mechanisms by which CA may exert its effects. Gene expression and protein analyses corroborated the observed anti-senescent effects, with CA modulating p16, p21, and pRB1 expressions and reducing oxidative stress markers. In conclusion, CA appeared to have senolytic and senomorphic potential in vitro, which could mitigate and reverse SIPS markers in BJ fibroblasts.

Mechanisms of Senescence and Anti-Senescence Strategies in the Skin

The skin is the layer of tissue that covers the largest part of the body in vertebrates, and its main function is to act as a protective barrier against external environmental factors, such as microorganisms, ultraviolet light and mechanical damage. Due to its important function, investigating the factors that lead to skin aging and age-related diseases, as well as understanding the biology of this process, is of high importance. Indeed, it has been reported that several external and internal stressors contribute to skin aging, similar to the aging of other tissues. Moreover, during aging, senescent cells accumulate in the skin and express senescence-associated factors, which act in a paracrine manner on neighboring healthy cells and tissues. In this review, we will present the factors that lead to skin aging and cellular senescence, as well as ways to study senescence in vitro and in vivo. We will further discuss the adverse effects of the accumulation of chronic senescent cells and therapeutic agents and tools to selectively target and eliminate them.

Senotherapy preserves resilience in aging

In aging societies, social and economic burdens of aging-related diseases are increasing significantly. Senotherapy, which targets aging by eliminating senescent cells (senolytics) or removing sources of chronic inflammation (senostatics), are proposed as novel strategies for aging-related diseases. Aged or frail people suffer a decline of tissue reserve capacity during aging. Resilience, which is much reduced in older people, is essential for recovery from diseases, stresses or crises. Impaired resilience is one of the reasons why aged people experience a gradual waning of their daily activity and an increase of multimorbidity. Calorie restriction results in senostatic alleviation of chronic inflammation, whereas senolytic drugs induce apoptosis of senescent cells, which exacerbate aging by excreting inflammatory factors. Thus, both senolytics and senostatics are expected to reduce sterile inflammation, originating from senescent cells. Geriatr Gerontol Int 2024; ••: ••-••.

Litopenaeus vannamei heat shock protein 90 (LvHSP90) interacts with white spot syndrome virus protein, WSSV322, to modulate hemocyte apoptosis during viral infection

As cellular chaperones, heat shock protein can facilitate viral infection in different steps of infection process. Previously, we have shown that the suppression of Litopenaeus vannamei (Lv)HSP90 not only results in a decline of white spot syndrome virus (WSSV) infection but also induces apoptosis in shrimp hemocyte cells. However, the mechanism underlying how LvHSP90 involved in WSSV infection remains largely unknown. In this study, a yeast two-hybrid assay and co-immunoprecipitation revealed that LvHSP90 interacts with the viral protein WSSV322 which function as an anti-apoptosis protein. Recombinant protein (r) LvHSP90 and rWSSV322 inhibited cycloheximide-induced hemocyte cell apoptosis in vitro. Co-silencing of LvHSP90 and WSSV322 in WSSV-infected shrimp led to a decrease in expression level of viral replication marker genes (VP28, ie-1) and WSSV copy number, while caspase 3/7 activity was noticeably induced. The number of apoptotic cells, confirmed by Hoechst 33342 staining assay and annexin V/PI staining, was significantly higher in LvHSP90 and WSSV322 co-silenced-shrimp than the control groups. Moreover, the co-silencing of LvHSP90 and WSSV322 triggered apoptosis by the mitochondrial pathway, resulting in the upregulation of pro-apoptotic protein expression (bax) and the downregulation of anti-apoptotic protein expression (bcl, Akt). This process also involved the release of cytochrome c (CytC) from the mitochondria and a decrease in mitochondrial membrane potential (MMP). These findings suggest that LvHSP90 interacts with WSSV322 to facilitate viral replication by inhibiting host apoptosis during WSSV infection.

HSP90 multi-functionality in cancer

The 90-kDa heat shock proteins (HSP90s) are molecular chaperones essential for folding, unfolding, degradation and activity of a wide range of client proteins. HSP90s and their cognate co-chaperones are subject to various post-translational modifications, functional consequences of which are not fully understood in cancer. Intracellular and extracellular HSP90 family members (HSP90α, HSP90β, GRP94 and TRAP1) promote cancer by sustaining various hallmarks of cancer, including cell death resistance, replicative immortality, tumor immunity, angiogenesis, invasion and metastasis. Given the importance of HSP90 in tumor progression, various inhibitors and HSP90-based vaccines were developed for the treatment of cancer. Further understanding of HSP90 functions in cancer may provide new opportunities and novel therapeutic strategies for the treatment of cancer.

Senescence in the bone marrow microenvironment: A driver in development of therapy-related myeloid neoplasms

Therapy-related myeloid neoplasms (t-MN) are a growing concern due to the continued use of cytotoxic therapies to treat malignancies. Cytotoxic therapies have been shown to drive therapy-induced senescence in normal tissues, including in the bone marrow microenvironment (BMME), which plays a crucial role in supporting normal hematopoiesis. This review examines recent work that focuses on the contribution of BMME senescence to t-MN pathogenesis, as well as offers a perspective on potential opportunities for therapeutic intervention.

Therapy-Induced Cellular Senescence: Potentiating Tumor Elimination or Driving Cancer Resistance and Recurrence?

Cellular senescence has been increasingly recognized as a hallmark of cancer, reflecting its association with aging and inflammation, its role as a response to deregulated proliferation and oncogenic stress, and its induction by cancer therapies. While therapy-induced senescence (TIS) has been linked to resistance, recurrence, metastasis, and normal tissue toxicity, TIS also has the potential to enhance therapy response and stimulate anti-tumor immunity. In this review, we examine the Jekyll and Hyde nature of senescent cells (SnCs), focusing on how their persistence while expressing the senescence-associated secretory phenotype (SASP) modulates the tumor microenvironment through autocrine and paracrine mechanisms. Through the SASP, SnCs can mediate both resistance and response to cancer therapies. To fulfill the unmet potential of cancer immunotherapy, we consider how SnCs may influence tumor inflammation and serve as an antigen source to potentiate anti-tumor immune response. This new perspective suggests treatment approaches based on TIS to enhance immune checkpoint blockade. Finally, we describe strategies for mitigating the detrimental effects of senescence, such as modulating the SASP or targeting SnC persistence, which may enhance the overall benefits of cancer treatment.

Skeletal phenotypes and molecular mechanisms in aging mice

Aging is an inevitable physiological process, often accompanied by age-related bone loss and subsequent bone-related diseases that pose serious health risks. Research on skeletal diseases caused by aging in humans is challenging due to lengthy study durations, difficulties in sampling, regional variability, and substantial investment. Consequently, mice are preferred for such studies due to their similar motor system structure and function to humans, ease of handling and care, low cost, and short generation time. In this review, we present a comprehensive overview of the characteristics, limitations, applicability, bone phenotypes, and treatment methods in naturally aging mice and prematurely aging mouse models (including SAMP6, POLG mutant, LMNA, SIRT6, ZMPSTE24, TFAM, ERCC1, WERNER, and KL/KL-deficient mice). We also summarize the molecular mechanisms of these aging mouse models, including cellular DNA damage response, senescence-related secretory phenotype, telomere shortening, oxidative stress, bone marrow mesenchymal stem cell (BMSC) abnormalities, and mitochondrial dysfunction. Overall, this review aims to enhance our understanding of the pathogenesis of aging-related bone diseases.

Exploring the Interplay between Cellular Senescence, Immunity, and Fibrosing Interstitial Lung Diseases: Challenges and Opportunities

Fibrosing interstitial lung diseases (ILDs) are characterized by the gradual and irreversible accumulation of scar tissue in the lung parenchyma. The role of the immune response in the pathogenesis of pulmonary fibrosis remains unclear. In recent years, substantial advancements have been made in our comprehension of the pathobiology driving fibrosing ILDs, particularly concerning various age-related cellular disturbances and immune mechanisms believed to contribute to an inadequate response to stress and increased susceptibility to lung fibrosis. Emerging studies emphasize cellular senescence as a key mechanism implicated in the pathobiology of age-related diseases, including pulmonary fibrosis. Cellular senescence, marked by antagonistic pleiotropy, and the complex interplay with immunity, are pivotal in comprehending many aspects of lung fibrosis. Here, we review progress in novel concepts in cellular senescence, its association with the dysregulation of the immune response, and the evidence underlining its detrimental role in fibrosing ILDs.

Cell senescence in liver diseases: pathological mechanism and theranostic opportunity

The liver is not oblivious to the passage of time, as ageing is a major risk factor for the development of acute and chronic liver diseases. Ageing produces alterations in all hepatic cells, affecting their phenotype and function and worsening the prognosis of liver disease. The ageing process also implies the accumulation of a cellular state characterized by a persistent proliferation arrest and a specific secretory phenotype named cellular senescence. Indeed, senescent cells have key roles in many physiological processes; however, their accumulation owing to ageing or pathological conditions contributes to the damage occurring in chronic diseases. The aim of this Review is to provide an updated description of the pathophysiological events in which hepatic senescent cells are involved and their role in liver disease progression. Finally, we discuss novel geroscience therapies that could be applied to prevent or improve liver diseases and age-mediated hepatic deregulations.

In the land of not-unhappiness: On the state-of-the-art of targeting aging and age-related diseases by biomedical research

The concept of the Land of Not-Unhappiness refers to the potential achievement of eliminating the pathologies of the aging process. To inform of how close we are to settling in the land, we summarize and review the achievements of research on anti-aging interventions over the last hundred years with a specific focus on strategies that slow down metabolism, compensate for aging-related losses, and target a broad range of age-related diseases. We critically evaluate the existing interventions labeled as "anti-aging," such as calorie restriction, exercise, stem cell administration, and senolytics, to provide a down-to-earth evaluation of their current applicability in counteracting aging. Throughout the text, we have maintained a light tone to make it accessible to non-experts in biogerontology, and provide a broad overview for those considering conducting studies, research, or seeking to understand the scientific basis of anti-aging medicine.

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.

Aging as a loss of morphostatic information: A developmental bioelectricity perspective

Maintaining order at the tissue level is crucial throughout the lifespan, as failure can lead to cancer and an accumulation of molecular and cellular disorders. Perhaps, the most consistent and pervasive result of these failures is aging, which is characterized by the progressive loss of function and decline in the ability to maintain anatomical homeostasis and reproduce. This leads to organ malfunction, diseases, and ultimately death. The traditional understanding of aging is that it is caused by the accumulation of molecular and cellular damage. In this article, we propose a complementary view of aging from the perspective of endogenous bioelectricity which has not yet been integrated into aging research. We propose a view of aging as a morphostasis defect, a loss of biophysical prepattern information, encoding anatomical setpoints used for dynamic tissue and organ homeostasis. We hypothesize that this is specifically driven by abrogation of the endogenous bioelectric signaling that normally harnesses individual cell behaviors toward the creation and upkeep of complex multicellular structures in vivo. Herein, we first describe bioelectricity as the physiological software of life, and then identify and discuss the links between bioelectricity and life extension strategies and age-related diseases. We develop a bridge between aging and regeneration via bioelectric signaling that suggests a research program for healthful longevity via morphoceuticals. Finally, we discuss the broader implications of the homologies between development, aging, cancer and regeneration and how morphoceuticals can be developed for aging.

Ageing microenvironment mediates lymphocyte carcinogenesis and lymphoma drug resistance: From mechanisms to clinical therapy (Review)

Cellular senescence has a complex role in lymphocyte carcinogenesis and drug resistance of lymphomas. Senescent lymphoma cells combine with immunocytes to create an ageing environment that can be reprogrammed with a senescence‑associated secretory phenotype, which gradually promotes therapeutic resistance. Certain signalling pathways, such as the NF‑κB, Wnt and PI3K/AKT/mTOR pathways, regulate the tumour ageing microenvironment and induce the proliferation and progression of lymphoma cells. Therefore, targeting senescence‑related enzymes or their signal transduction pathways may overcome radiotherapy or chemotherapy resistance and enhance the efficacy of relapsed/refractory lymphoma treatments. Mechanisms underlying drug resistance in lymphomas are complex. The ageing microenvironment is a novel factor that contributes to drug resistance in lymphomas. In terms of clinical translation, some senolytics have been used in clinical trials on patients with relapsed or refractory lymphoma. Combining immunotherapy with epigenetic drugs may achieve better therapeutic effects; however, senescent cells exhibit considerable heterogeneity and lymphoma has several subtypes. Extensive research is necessary to achieve the practical application of senolytics in relapsed or refractory lymphomas. This review summarises the mechanisms of senescence‑associated drug resistance in lymphoma, as well as emerging strategies using senolytics, to overcome therapeutic resistance in lymphoma.

Targeting CK2 eliminates senescent cells and prolongs lifespan in Zmpste24-deficient mice

Senescent cell clearance is emerging as a promising strategy for treating age-related diseases. Senolytics are small molecules that promote the clearance of senescent cells; however, senolytics are uncommon and their underlying mechanisms remain largely unknown. Here, we investigated whether genomic instability is a potential target for senolytic. We screened small-molecule kinase inhibitors involved in the DNA damage response (DDR) in Zmpste24-/- mouse embryonic fibroblasts, a progeroid model characterized with impaired DDR and DNA repair. 4,5,6,7-tetrabromo-2-azabenzamidazole (TBB), which specifically inhibits casein kinase 2 (CK2), was selected and discovered to preferentially trigger apoptosis in Zmpste24-/- cells. Mechanistically, inhibition of CK2 abolished the phosphorylation of heterochromatin protein 1α (HP1α), which retarded the dynamic HP1α dissociation from repressive histone mark H3K9me3 and its relocalization with γH2AX to DNA damage sites, suggesting that disrupting heterochromatin remodeling in the initiation of DDR accelerates apoptosis in senescent cells. Furthermore, feeding Zmpste24-deficient mice with TBB alleviated progeroid features and extended their lifespan. Our study identified TBB as a new class senolytic compound that can reduce age-related symptoms and prolong lifespan in progeroid mice.

Molecular mechanisms of aging and anti-aging strategies

Aging is a complex and multifaceted process involving a variety of interrelated molecular mechanisms and cellular systems. Phenotypically, the biological aging process is accompanied by a gradual loss of cellular function and the systemic deterioration of multiple tissues, resulting in susceptibility to aging-related diseases. Emerging evidence suggests that aging is closely associated with telomere attrition, DNA damage, mitochondrial dysfunction, loss of nicotinamide adenine dinucleotide levels, impaired macro-autophagy, stem cell exhaustion, inflammation, loss of protein balance, deregulated nutrient sensing, altered intercellular communication, and dysbiosis. These age-related changes may be alleviated by intervention strategies, such as calorie restriction, improved sleep quality, enhanced physical activity, and targeted longevity genes. In this review, we summarise the key historical progress in the exploration of important causes of aging and anti-aging strategies in recent decades, which provides a basis for further understanding of the reversibility of aging phenotypes, the application prospect of synthetic biotechnology in anti-aging therapy is also prospected.

The potential for senotherapy as a novel approach to extend life quality in veterinary medicine

Cellular senescence, a condition where cells undergo arrest and can assume an inflammatory phenotype, has been associated with initiation and perpetuation of inflammation driving multiple disease processes in rodent models and humans. Senescent cells secrete inflammatory cytokines, proteins, and matrix metalloproteinases, termed the senescence associated secretory phenotype (SASP), which accelerates the aging processes. In preclinical models, drug interventions termed "senotherapeutics" selectively clear senescent cells and represent a promising strategy to prevent or treat multiple age-related conditions in humans and veterinary species. In this review, we summarize the current available literature describing in vitro evidence for senotheraputic activity, preclinical models of disease, ongoing human clinical trials, and potential clinical applications in veterinary medicine. These promising data to date provide further justification for future studies identifying the most active senotherapeutic combinations, dosages, and routes of administration for use in veterinary medicine.

Selective Elimination of Senescent Cancer Cells by Galacto-Modified PROTACs

Although the selective and effective clearance of senescent cancer cells can improve cancer treatment, their development is confronted by many challenges. As part of efforts designed to overcome these problems, prodrugs, whose design is based on senescence-associated β-galactosidase (SA-β-gal), have been developed to selectively eliminate senescent cells. However, chemotherapies relying on targeted molecular inhibitors as senolytic drugs can induce drug resistance. In the current investigation, we devised a new strategy for selective degradation of target proteins in senescent cancer cells that utilizes a prodrug composed of the SA-β-gal substrate galactose (galacto) and the proteolysis-targeting chimeras (PROTACs) as senolytic agents. Prodrugs Gal-ARV-771 and Gal-MS99 were found to display senolytic indexes higher than those of ARV-771 and MS99. Significantly, results of in vivo studies utilizing a human lung A549 xenograft mouse model demonstrated that concomitant treatment with etoposide and Gal-ARV-771 leads to a significant inhibition of tumor growth without eliciting significant toxicity.

Focus on senescence: Clinical significance and practical applications

The older population is increasing worldwide, and life expectancy is continuously rising, predominantly thanks to medical and technological progress. Healthspan refers to the number of years an individual can live in good health. From a gerontological viewpoint, the mission is to extend the life spent in good health, promoting well-being and minimizing the impact of aging-related diseases to slow the aging process. Biologically, aging is a malleable process characterized by an intra- and inter-individual heterogeneous and dynamic balance between accumulating damage and repair mechanisms. Cellular senescence is a key component of this process, with senescent cells accumulating in different tissues and organs, leading to aging and age-related disease susceptibility over time. Removing senescent cells from the body or slowing down the burden rate has been proposed as an efficient way to reduce age-dependent deterioration. In animal models, senotherapeutic molecules can extend life expectancy and lifespan by either senolytic or senomorphic activity. Much research shows that dietary and physical activity-driven lifestyle interventions protect against senescence. This narrative review aims to summarize the current knowledge on targeting senescent cells to reduce the risk of age-related disease in animal models and their translational potential for humans. We focused on studies that have examined the potential role of senotherapeutics in slowing the aging process and modifying age-related disease burdens. The review concludes with a general discussion of the mechanisms underlying this unique trajectory and its implications for future research.

Metabolic pathways in immune senescence and inflammaging: Novel therapeutic strategy for chronic inflammatory lung diseases. An EAACI position paper from the Task Force for Immunopharmacology

The accumulation of senescent cells drives inflammaging and increases morbidity of chronic inflammatory lung diseases. Immune responses are built upon dynamic changes in cell metabolism that supply energy and substrates for cell proliferation, differentiation, and activation. Metabolic changes imposed by environmental stress and inflammation on immune cells and tissue microenvironment are thus chiefly involved in the pathophysiology of allergic and other immune-driven diseases. Altered cell metabolism is also a hallmark of cell senescence, a condition characterized by loss of proliferative activity in cells that remain metabolically active. Accelerated senescence can be triggered by acute or chronic stress and inflammatory responses. In contrast, replicative senescence occurs as part of the physiological aging process and has protective roles in cancer surveillance and wound healing. Importantly, cell senescence can also change or hamper response to diverse therapeutic treatments. Understanding the metabolic pathways of senescence in immune and structural cells is therefore critical to detect, prevent, or revert detrimental aspects of senescence-related immunopathology, by developing specific diagnostics and targeted therapies. In this paper, we review the main changes and metabolic alterations occurring in senescent immune cells (macrophages, B cells, T cells). Subsequently, we present the metabolic footprints described in translational studies in patients with chronic asthma and chronic obstructive pulmonary disease (COPD), and review the ongoing preclinical studies and clinical trials of therapeutic approaches aiming at targeting metabolic pathways to antagonize pathological senescence. Because this is a recently emerging field in allergy and clinical immunology, a better understanding of the metabolic profile of the complex landscape of cell senescence is needed. The progress achieved so far is already providing opportunities for new therapies, as well as for strategies aimed at disease prevention and supporting healthy aging.

Therapeutic strategies targeting cellular senescence for cancer and other diseases

Cellular senescence occurs in response to endogenous or exogenous stresses and is characterized by stable cell cycle arrest, alterations in nuclear morphology and secretion of proinflammatory factors, referred to as the senescence-associated secretory phenotype (SASP). An increase of senescent cells is associated with the development of several types of cancer and aging-related diseases. Therefore, senolytic agents that selectively remove senescent cells may offer opportunities for developing new therapeutic strategies against such cancers and aging-related diseases. This review outlines senescence inducers and the general characteristics of senescent cells. We also discuss the involvement of senescent cells in certain cancers and diseases. Finally, we describe a series of senolytic agents and their utilization in therapeutic strategies.

Revolutionizing Diabetic Foot Ulcer Care: The Senotherapeutic Approach

Diabetic foot ulcers (DFUs) are a prevalent and profoundly debilitating complication that afflicts individuals with diabetes mellitus (DM). These ulcers are associated with substantial morbidity, recurrence rates, disability, and mortality, imposing substantial economic, psychological, and medical burdens. Timely detection and intervention can mitigate the morbidity and disparities linked to DFU. Nevertheless, current therapeutic approaches for DFU continue to grapple with multifaceted limitations. A growing body of evidence emphasizes the crucial role of cellular senescence in the pathogenesis of chronic wounds. Interventions that try to delay cellular senescence, eliminate senescent cells (SnCs), or suppress the senescence-associated secretory phenotype (SASP) have shown promise for helping chronic wounds to heal. In this context, targeting cellular senescence emerges as a novel therapeutic strategy for DFU. In this comprehensive review, we look at the pathology and treatment of DFU in a systematic way. We also explain the growing importance of investigating SnCs in DFU and highlight the great potential of senotherapeutics that target SnCs in DFU treatment. The development of efficacious and safe senotherapeutics represents a pioneering therapeutic approach aimed at enhancing the quality of life for individuals affected by DFU.

A Conversation with ChatGPT on Contentious Issues in Senescence and Cancer Research

Artificial intelligence (AI) platforms, such as Generative Pretrained Transformer (ChatGPT), have achieved a high degree of popularity within the scientific community due to their utility in providing evidence-based reviews of the literature. However, the accuracy and reliability of the information output and the ability to provide critical analysis of the literature, especially with respect to highly controversial issues, has generally not been evaluated. In this work, we arranged a question/answer session with ChatGPT regarding several unresolved questions in the field of cancer research relating to therapy-induced senescence (TIS), including the topics of senescence reversibility, its connection to tumor dormancy, and the pharmacology of the newly emerging drug class of senolytics. ChatGPT generally provided responses consistent with the available literature, although occasionally overlooking essential components of the current understanding of the role of TIS in cancer biology and treatment. Although ChatGPT, and similar AI platforms, have utility in providing an accurate evidence-based review of the literature, their outputs should still be considered carefully, especially with respect to unresolved issues in tumor biology. SIGNIFICANCE STATEMENT: Artificial Intelligence platforms have provided great utility for researchers to investigate biomedical literature in a prompt manner. However, several issues arise when it comes to certain unresolved biological questions, especially in the cancer field. This work provided a discussion with ChatGPT regarding some of the yet-to-be-fully-elucidated conundrums of the role of therapy-induced senescence in cancer treatment and highlights the strengths and weaknesses in utilizing such platforms for analyzing the scientific literature on this topic.

Profiling microRNA expression during senescence and aging: mining for a diagnostic tool of senescent-cell burden

In the last decade cellular senescence, a hallmark of aging, has come into focus for pharmacologically targeting aging processes. Senolytics are one of these interventive strategies that have advanced into clinical trials, creating an unmet need for minimally invasive biomarkers of senescent cell load to identify patients at need for senotherapy. We created a landscape of miRNA and mRNA expression in five human cell types induced to senescence in-vitro and provide proof-of-principle evidence that miRNA expression can track senescence burden dynamically in-vivo using transgenic p21 high senescent cell clearance in HFD fed mice. Finally, we profiled miRNA expression in seven different tissues, total plasma, and plasma derived EVs of young and 25 months old mice. In a systematic analysis, we identified 22 candidate senomiRs with potential to serve as circulating biomarkers of senescence not only in rodents, but also in upcoming human clinical senolytic trials.

The senescence journey in cancer immunoediting

Cancer progression is continuously controlled by the immune system which can identify and destroy nascent tumor cells or inhibit metastatic spreading. However, the immune system and its deregulated activity in the tumor microenvironment can also promote tumor progression favoring the outgrowth of cancers capable of escaping immune control, in a process termed cancer immunoediting. This process, which has been classified into three phases, i.e. "elimination", "equilibrium" and "escape", is influenced by several cancer- and microenvironment-dependent factors. Senescence is a cellular program primed by cells in response to different pathophysiological stimuli, which is based on long-lasting cell cycle arrest and the secretion of numerous bioactive and inflammatory molecules. Because of this, cellular senescence is a potent immunomodulatory factor promptly recruiting immune cells and actively promoting tissue remodeling. In the context of cancer, these functions can lead to both cancer immunosurveillance and immunosuppression. In this review, the authors will discuss the role of senescence in cancer immunoediting, highlighting its context- and timing-dependent effects on the different three phases, describing how senescent cells promote immune cell recruitment for cancer cell elimination or sustain tumor microenvironment inflammation for immune escape. A potential contribution of senescent cells in cancer dormancy, as a mechanism of therapy resistance and cancer relapse, will be discussed with the final objective to unravel the immunotherapeutic implications of senescence modulation in cancer.

Insights into targeting cellular senescence with senolytic therapy: The journey from preclinical trials to clinical practice

Interconnected, fundamental aging processes are central to many illnesses and diseases. Cellular senescence is a mechanism that halts the cell cycle in response to harmful stimuli. Senescent cells (SnCs) can emerge at any point in life, and their persistence, along with the numerous proteins they secrete, can negatively affect tissue function. Interventions aimed at combating persistent SnCs, which can destroy tissues, have been used in preclinical models to delay, halt, or even reverse various diseases. Consequently, the development of small-molecule senolytic medicines designed to specifically eliminate SnCs has opened potential avenues for the prevention or treatment of multiple diseases and age-related issues in humans. In this review, we explore the most promising approaches for translating small-molecule senolytics and other interventions targeting senescence in clinical practice. This discussion highlights the rationale for considering SnCs as therapeutic targets for diseases affecting individuals of all ages.

Mesenchymal Stromal Cell Senescence Induced by Dnmt3a -Mutant Hematopoietic Cells is a Targetable Mechanism Driving Clonal Hematopoiesis and Initiation of Hematologic Malignancy

Clonal hematopoiesis (CH) can predispose to blood cancers due to enhanced fitness of mutant hematopoietic stem and progenitor cells (HSPCs), but the mechanisms driving this progression are not understood. We hypothesized that malignant progression is related to microenvironment-remodelling properties of CH-mutant HSPCs. Single-cell transcriptomic profiling of the bone marrow microenvironment in Dnmt3a R878H/+ mice revealed signatures of cellular senescence in mesenchymal stromal cells (MSCs). Dnmt3a R878H/+ HSPCs caused MSCs to upregulate the senescence markers SA-β-gal, BCL-2, BCL-xL, Cdkn1a (p21) and Cdkn2a (p16), ex vivo and in vivo . This effect was cell contact-independent and can be replicated by IL-6 or TNFα, which are produced by Dnmt3a R878H/+ HSPCs. Depletion of senescent MSCs in vivo reduced the fitness of Dnmt3a R878H/+ hematopoietic cells and the progression of CH to myeloid neoplasms using a sequentially inducible Dnmt3a ; Npm1 -mutant model. Thus, Dnmt3a -mutant HSPCs reprogram their microenvironment via senescence induction, creating a self-reinforcing niche favoring fitness and malignant progression.

Statement of Significance

Mesenchymal stromal cell senescence induced by Dnmt3a -mutant hematopoietic stem and progenitor cells drives clonal hematopoiesis and initiation of hematologic malignancy.

An in vivo screening platform identifies senolytic compounds that target p16INK4a+ fibroblasts in lung fibrosis

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.

Intervention treatment reducing cellular senescence inhibits tubulointerstitial fibrosis in diabetic mice following acute kidney injury

Senescence of kidney tubules leads to tubulointerstitial fibrosis (TIF). Proximal tubular epithelial cells undergo stress-induced senescence during diabetes and episodes of acute kidney injury (AKI), and combining these injuries promotes the progression of diabetic kidney disease (DKD). Since TIF is crucial to progression of DKD, we examined the therapeutic potential of targeting senescence with a senolytic drug (HSP90 inhibitor) and/or a senostatic drug (ASK1 inhibitor) in a model of TIF in which AKI is superimposed on diabetes. After 8 weeks of streptozotocin-induced diabetes, mice underwent bilateral clamping of renal pedicles to induce mild AKI, followed by 28 days of reperfusion. Groups of mice (n=10-12) received either vehicle, HSP90 inhibitor (alvespimycin), ASK1 inhibitor (GS-444217), or both treatments. Vehicle-treated mice displayed tubular injury at day 3 and extensive tubular cell senescence at day 10, which remained unresolved at day 28. Markers of senescence (Cdkn1a and Cdkn2a), inflammation (Cd68, Tnf, and Ccl2), and TIF (Col1a1, Col4a3, α-Sma/Acta2, and Tgfb1) were elevated at day 28, coinciding with renal function impairment. Treatment with alvespimycin alone reduced kidney senescence and levels of Col1a1, Acta2, Tgfb1, and Cd68; however, further treatment with GS-444217 also reduced Col4a3, Tnf, Ccl2, and renal function impairment. Senolytic therapy can inhibit TIF during DKD, but its effectiveness can be improved by follow-up treatment with a senostatic inhibitor, which has important implications for treating progressive DKD.

Mechanisms and therapeutic strategies for senescence-associated secretory phenotype in the intervertebral disc degeneration microenvironment

As a permanent state of cell cycle arrest, cellular senescence has become an important factor in aging and age-related diseases. As a central regulator of physiology and pathology associated with cellular senescence, the senescence associated secretory phenotype can create an inflammatory and catabolic environment through autocrine and paracrine ways, ultimately affecting tissue microstructure. As an age-related disease, the correlation between intervertebral disc degeneration and cellular senescence has been confirmed by many studies. Various pathological factors in the microenvironment of intervertebral disc degeneration promote senescent cells to produce and accumulate and express excessive senescence associated secretory phenotype. In this case, senescence associated secretory phenotype has received considerable attention as a potential target for delaying or treating disc degeneration. Therefore, we reviewed the latest research progress of senescence associated secretory phenotype, related regulatory mechanisms and intervertebral disc cell senescence treatment strategies. It is expected that further understanding of the underlying mechanism between cellular senescence pathology and intervertebral disc degeneration will help to formulate reasonable senescence regulation strategies, so as to achieve ideal therapeutic effects.

The translational potential of this article

Existing treatment strategies often fall short in addressing the challenge of repairing intervertebral disc Intervertebral disc degeneration（IVD） degeneration. The accumulation of senescent cells and the continuous release of senescence-associated secretory phenotype (SASP) perpetually impede disc homeostasis and hinder tissue regeneration. This impairment in repair capability presents a significant obstacle to the practical clinical implementation of strategies for intervertebral disc degeneration. As a result, we present a comprehensive overview of the latest advancements in research, the associated regulatory mechanisms, and strategies for treating SASP in IVD cells. This article aims to investigate effective interventions for delaying the onset and progression of age-related intervertebral disc degeneration. In an era where the aging population is becoming increasingly prominent, this endeavor holds paramount practical and translational significance.

Recent advances in senescence-associated secretory phenotype and osteoporosis

The worldwide elderly population is on the rise, and aging is a major osteoporosis risk factor. Senescent cells accumulation can have a detrimental effect the body as we age. The senescence-associated secretory phenotype (SASP), an essential cellular senescence hallmark, is an important mechanism connecting cellular senescence to osteoporosis. This review describes in detail the characteristics of SASPs and their regulatory agencies, and shed fresh light on how SASPs from different senescent cells contribute to osteoporosis development. Furthermore, we summarized various innovative therapy techniques that target SASPs to lower the burden of osteoporosis in the elderly and discussed the potential challenges of SASPs-based therapy for osteoporosis as a new clinical trial.