Suppression of the senescence-associated secretory phenotype (SASP) in human fibroblasts using small molecule inhibitors of p38 MAP kinase and MK2

Changing landscape of hematopoietic and mesenchymal cells and their interactions during aging and in age-related skeletal pathologies

Aging profoundly impacts mesenchymal and hematopoietic lineage cells, including their progenitors-the skeletal stem cells (SSCs) and hematopoietic stem cells (HSCs), respectively. SSCs are crucial for skeletal development, homeostasis, and regeneration, maintaining bone integrity by differentiating into osteoblasts, adipocytes, and other lineages that contribute to the bone marrow (BM) microenvironment. Meanwhile, HSCs sustain hematopoiesis and immune function. With aging, SSCs and HSCs undergo significant functional decline, partly driven by cellular senescence-a hallmark of aging characterized by irreversible growth arrest, secretion of pro-inflammatory factors (senescence associated secretory phenotype, SASP), and impaired regenerative potential. In SSCs, senescence skews lineage commitment toward adipogenesis at the expense of osteogenesis, contributing to increased bone marrow adiposity , reduced bone quality, and osteoporosis. Similarly, aged HSCs exhibit diminished self-renewal, biased differentiation, and heightened inflammation, compromising hematopoietic output and immune function. In this review, we examine the age-related cellular and molecular changes in SSCs and HSCs, their lineage decisions in the aging microenvironment, and the interplay between skeletal and hematopoietic compartments. We also discuss the role of senescence-driven alterations in BM homeostasis and how targeting cellular aging mechanisms may offer therapeutic strategies for mitigating age-related skeletal and hematopoietic decline.

Anti-senescence therapies: a new concept to address cardiovascular disease

Accumulation of senescent cells is an increasingly recognized factor in the development and progression of cardiovascular (CV) disease (CVD). Senescent cells of different types display a pro-inflammatory and matrix remodelling molecular programme, known as the 'senescence-associated secretory phenotype' (SASP), which has roots in (epi)genetic changes. Multiple therapeutic options (senolytics, anti-SASP senomorphics, and epigenetic reprogramming) that delete or ameliorate cellular senescence have recently emerged. Some drugs routinely used in the clinics also have anti-senescence effects. However, multiple challenges hinder the application of novel anti-senescence therapeutics in the clinical setting. Understanding the biology of cellular senescence, advantages and pitfalls of anti-senescence treatments, and patients who can profit from these interventions is necessary to introduce this novel therapeutic modality into the clinics. We provide a guide through the molecular machinery of senescent cells, systematize anti-senescence treatments, and propose a pathway towards senescence-adapted clinical trial design to aid future efforts.

Sex differences in middle-aged and old Wistar rats in response to long-term sulforaphane treatment for prevention of neuroinflammation, cognitive decline and brain senescence

The nervous system (NS) experiences morphological and functional changes during the aging process, where low-grade chronic inflammation, oxidative stress and senescence are key regulators. Sulforaphane (SFN) is an isothiocyanate that activates redox response and inhibits the inflammatory process, which could modify the pro-inflammatory components of senescent cells secretory phenotype (SASP). Here we aimed to determine if SFN long-term treatment was able to prevent age-associated damage in the NS of adult and old females and males Wistar rats. We evaluated cytokines and chemokines profile, senescent cells markers, and memory parameters of adult (15 m.o.) and old (21 m.o.) rats after three months of SFN treatment. Young rats (4 m.o.) were used as age controls. Differences between sexes were observed in the inflammatory profile. Our results showed that SFN-treatment diminished proinflammatory molecules, senescence markers and senescent cells number in brain cortex and hippocampus from males and females' adult rats, but no effects were observed in both sexes old groups compared with the same age control groups. SFN-dependent reduction in inflammatory and senescence parameters resulted in better scores in Barnes Maze Trial memory test when compared with same age non-treated group. Interestingly, adult females showed higher levels of proinflammatory cytokines and chemokines than adult males, which were prevented by SFN-treatment. No effects of SFN were observed in memory of old-treated groups.

The context-dependent effect of cellular senescence: From embryogenesis and wound healing to aging

Aging is characterized by a steady loss of physiological integrity, leading to impaired function and increased vulnerability to death. Cell senescence is a biological process that progresses with aging and is believed to be a key driver of age-related diseases. Senescence, a hallmark of aging, also demonstrates its beneficial physiological aspects as an anti-cancer, pro-regenerative, homeostatic, and developmental mechanism. A transitory response in which the senescent cells are quickly formed and cleared may promote tissue regeneration and organismal fitness. At the same time, senescence-related secretory phenotypes associated with extended senescence can have devastating effects. The fact that the interaction between senescent cells and their surroundings is very context-dependent may also help to explain this seemingly opposing pleiotropic function. Further, mitochondrial dysfunction is an often-unappreciated hallmark of cellular senescence and figures prominently in multiple feedback loops that induce and maintain the senescent phenotype. This review summarizes the mechanism of cellular senescence and the significance of acute senescence. We concisely introduced the context-dependent role of senescent cells and SASP, aspects of mitochondrial biology altered in the senescent cells, and their impact on the senescent phenotype. Finally, we conclude with recent therapeutic advancements targeting cellular senescence, focusing on acute injuries and age-associated diseases. Collectively, these insights provide a future roadmap for the role of senescence in organismal fitness and life span extension.

Prolonged Low-Dose Administration of FDA-Approved Drugs for Non-Cancer Conditions: A Review of Potential Targets in Cancer Cells

Though not specifically designed for cancer therapy, several FDA-approved drugs such as metformin, aspirin, and simvastatin have an effect in lowering the incidence of cancer. However, there is a great discrepancy between in vitro concentrations needed to eliminate cancer cells and the plasma concentration normally tolerated within the body. At present, there is no universal explanation for this discrepancy and several mechanisms have been proposed including targeting cancer stem cells (CSCs) or cellular senescence. CSCs are cells with the ability of self-renewal and differentiation known to be resistant to chemotherapy. Senescence is a response to damage and stress, characterized by permanent cell-cycle arrest and apoptotic resistance. Although, for both situations, there are few examples where low concentrations of the FDA-approved drugs were the most effective, there is no satisfactory data to support that either CSCs or cellular senescence are the target of these drugs. In this review, we concisely summarize the most used FDA-approved drugs for non-cancer conditions as well as their potential mechanisms of action in lowering cancer incidence. In addition, we propose that prolonged low-dose administration (PLDA) of specific FDA-approved drugs can be useful for effectively preventing metastasis formation in selected patients.

Recent Advances in Anti-Aging Therapeutic Strategies Targeting DNA Damage Response and Senescence-Associated Secretory Phenotype-Linked Signaling Cascade

Aging is considered the contributory accumulation of abruptions occurring through cell signaling cascades, which ultimately cause changes in physical functions, cell fate, and damage across all organ systems. DNA damage response (DDR) also occurs through telomere shortening, tumor formation, mitochondrial dysfunction, and so forth. Cellular aging occurs through cell cycle arrest, which is the result of extended DDR cascade signaling networks via MDC1, 53BP1, H2AX, ATM, ARF, P53, P13-Akt, BRAF, Sirtuins, NAD + , and so forth. These persistent cell cycle arrests initiated by DDR and other associated stress-induced signals promote a permanent state of cell cycle arrest called senescence-associated secretory phenotype (SASP). However, cellular aging gets accelerated with faulty DNA repair systems, and the produced senescent cells further generate various promoting contributors to age-related dysfunctional diseases including SASP. Any changes to these factors contribute to age-related disease development. Therefore, this review explores anti-aging factors targeting DDR and SASP regulation and their detailed signaling networks. In addition, it allows researchers to identify anti-aging targets and anti-aging therapeutic strategies based on identified and nonidentified targets.

Remodeling of tumor microenvironment by cellular senescence and immunosenescence in cervical cancer

Cellular senescence is a response to various stress signals, which is characterized by stable cell cycle arrest, alterations in cellular morphology, metabolic reprogramming and production of senescence-associated secretory phenotype (SASP). When it occurs in the immune system, it is called immunosenescence. Cervical cancer is a common gynecological malignancy, and cervical cancer screening is generally recommended before the age of 65. Elderly women (≥65 years) are more often diagnosed with advanced disease and have poorer prognosis compared to younger patients. Despite extensive research, the tumor microenvironment requires more in-depth exploration, particularly in elderly patients. In cervical cancer, senescent cells have a double-edged sword effect on tumor progression. Induction of preneoplastic cell senescence prevents tumor initiation, and several treatment approaches of cervical cancer act in part by inducing cancer cell senescence. However, senescent immune cell populations within the tumor microenvironment facilitate tumor development, recurrence, treatment resistance, etc. Amplification of beneficial effects and inhibition of aging-related pro-tumorigenic pathways contribute to improving antitumor effects. This review discusses senescent cancer and immune cells present in the tumor microenvironment of cervical cancer and how these senescent cells and their SASP remodel the tumor microenvironment, influence antitumor immunity and tumor initiation and development. Moreover, we discuss the significance of senotherapeutics that enable to eliminate senescent cells and prevent tumor progression and development through improving antitumor immunity and affecting the tumor microenvironment.

Suppressing the Aging Phenotype of Mesenchymal Stromal Cells: Are We Ready for Clinical Translation?

Mesenchymal stem/stromal cells (MSCs) are involved in the maintenance and regeneration of a large variety of tissues due to their stemness and multi-lineage differentiation capability. Harnessing these advantageous features, a flurry of clinical trials have focused on MSCs to treat different pathologies, but only few protocols have received regulatory approval so far. Among the various causes hindering MSCs' efficacy is the emergence of cellular senescence, which has been correlated with specific characteristics, such as morphological and epigenetic alterations, DNA damage, ROS production, mitochondrial dysfunction, telomere shortening, non-coding RNAs, loss of proteostasis, and a peculiar senescence-associated secretory phenotype. Several strategies have been investigated for delaying or even hopefully reverting the onset of senescence, as assessed by the senescent phenotype of MSCs. Here, the authors reviewed the most updated literature on the potential causes of senescence, with a particular emphasis on the current and future therapeutic approaches aimed at reverting senescence and/or extending the functional lifespan of stem cells.

The senescence-associated secretory phenotype and its physiological and pathological implications

Cellular senescence is a state of terminal growth arrest associated with the upregulation of different cell cycle inhibitors, mainly p16 and p21, structural and metabolic alterations, chronic DNA damage responses, and a hypersecretory state known as the senescence-associated secretory phenotype (SASP). The SASP is the major mediator of the paracrine effects of senescent cells in their tissue microenvironment and of various local and systemic biological functions. In this Review, we discuss the composition, dynamics and heterogeneity of the SASP as well as the mechanisms underlying its induction and regulation. We describe the various biological properties of the SASP, its beneficial and detrimental effects in different physiological and pathological settings, and its impact on overall health span. Finally, we discuss the use of the SASP as a biomarker and of SASP inhibitors as senomorphic interventions to treat cancer and other age-related conditions.

Cellular senescence in Alzheimer's disease: from physiology to pathology

Alzheimer's disease (AD) is one of the most common neurodegenerative disorders, characterized by the accumulation of Aβ and abnormal tau hyperphosphorylation. Despite substantial efforts in development of drugs targeting Aβ and tau pathologies, effective therapeutic strategies for AD remain elusive. Recent attention has been paid to the significant role of cellular senescence in AD progression. Mounting evidence suggests that interventions targeting cellular senescence hold promise in improving cognitive function and ameliorating hallmark pathologies in AD. This narrative review provides a comprehensive summary and discussion of the physiological roles, characteristics, biomarkers, and commonly employed in vivo and in vitro models of cellular senescence, with a particular focus on various cell types in the brain, including astrocytes, microglia, oligodendrocyte precursor cells, neurons, and endothelial cells. The review further delves into factors influencing cellular senescence in AD and emphasizes the significance of targeting cellular senescence as a promising approach for AD treatment, which includes the utilization of senolytics and senomorphics.

The Quest for Eternal Youth: Hallmarks of Aging and Rejuvenating Therapeutic Strategies

The impressive achievements made in the last century in extending the lifespan have led to a significant growth rate of elderly individuals in populations across the world and an exponential increase in the incidence of age-related conditions such as cardiovascular diseases, diabetes mellitus type 2, and neurodegenerative diseases. To date, geroscientists have identified 12 hallmarks of aging (genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, impaired macroautophagy, mitochondrial dysfunction, impaired nutrient sensing, cellular senescence, stem cell exhaustion, defective intercellular communication, chronic inflammation, and gut dysbiosis), intricately linked among each other, which can be targeted with senolytic or senomorphic drugs, as well as with more aggressive approaches such as cell-based therapies. To date, side effects seriously limit the use of these drugs. However, since rejuvenation is a dream of mankind, future research is expected to improve the tolerability of the available drugs and highlight novel strategies. In the meantime, the medical community, healthcare providers, and society should decide when to start these treatments and how to tailor them individually.

New insights into the role of cellular senescence and chronic wounds

Chronic or non-healing wounds, such as diabetic foot ulcers (DFUs), venous leg ulcers (VLUs), pressure ulcers (PUs) and wounds in the elderly etc., impose significant biological, social, and financial burdens on patients and their families. Despite ongoing efforts, effective treatments for these wounds remain elusive, costing the United States over US$25 billion annually. The wound healing process is notably slower in the elderly, partly due to cellular senescence, which plays a complex role in wound repair. High glucose levels, reactive oxygen species, and persistent inflammation are key factors that induce cellular senescence, contributing to chronic wound failure. This suggests that cellular senescence may not only drive age-related phenotypes and pathology but also be a key mediator of the decreased capacity for trauma repair. This review analyzes four aspects: characteristics of cellular senescence; cytotoxic stressors and related signaling pathways; the relationship between cellular senescence and typical chronic non-healing wounds; and current and future treatment strategies. In theory, anti-aging therapy may influence the process of chronic wound healing. However, the underlying molecular mechanism is not well understood. This review summarizes the relationship between cellular senescence and chronic wound healing to contribute to a better understanding of the mechanisms of chronic wound healing.

Convergent evolution of senescent fibroblasts in fibrosis and cancer with aging

Aging is associated with stereotyped changes in the tissue microenvironment that increase susceptibility to diseases of the elderly, including organ fibrosis and cancer. From a tissue perspective, fibrosis and cancer can both be viewed as non-healing wounds with pathogenic activation of tissue repair pathways in the stroma. If fibrosis and cancer represent an example of the convergent evolution of maladaptive stromal responses in distinct pathologies, what are the analogous cell types that might emerge in both diseases that share similarities in identity and function? In this review, we explore how senescent fibroblasts form a nexus that connects the aging organ with both fibrosis and cancer. The advent of single cell sequencing, coupled with improved detection of cell types with senescent traits in vivo, have allowed us to identify senescent fibroblasts with similar identities in both fibrosis and cancer that share pro-fibrotic programs. In addition to their ability to reorganize the extracellular matrix in diseased states, these pro-fibrotic senescent fibroblasts can also promote epithelial reprogramming and immune rewiring, which drive disease progression in fibrosis and cancer. Finally, the identification of common pathogenic cell types in fibrosis and cancer also presents a therapeutic opportunity to target both diseases with a shared approach.

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.

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).

Cellular senescence and metabolic reprogramming: Unraveling the intricate crosstalk in the immunosuppressive tumor microenvironment

The intrinsic oncogenic mechanisms and properties of the tumor microenvironment (TME) have been extensively investigated. Primary features of the TME include metabolic reprogramming, hypoxia, chronic inflammation, and tumor immunosuppression. Previous studies suggest that senescence-associated secretory phenotypes that mediate intercellular information exchange play a role in the dynamic evolution of the TME. Specifically, hypoxic adaptation, metabolic dysregulation, and phenotypic shifts in immune cells regulated by cellular senescence synergistically contribute to the development of an immunosuppressive microenvironment and chronic inflammation, thereby promoting the progression of tumor events. This review provides a comprehensive summary of the processes by which cellular senescence regulates the dynamic evolution of the tumor-adapted TME, with focus on the complex mechanisms underlying the relationship between senescence and changes in the biological functions of tumor cells. The available findings suggest that components of the TME collectively contribute to the progression of tumor events. The potential applications and challenges of targeted cellular senescence-based and combination therapies in clinical settings are further discussed within the context of advancing cellular senescence-related research.

Pharmacoinformatics-based identification of phytochemicals from Solanum torvum Swartz. fruits as potential inhibitors for MAPK14 protein

Plants and phytocompounds gained more attention because of their unrivalled variety of chemical diversity. In this view, the present study was executed to predict the anticancer potential of Solanum torvum Swartz. fruits derived phytocompounds against one of the breast cancer target proteins (MAPK14, PDB ID: 5ETA, resolution: 2.80 Å) through pharmacoinformatics-based screening and molecular dynamics simulation tools. Initially, a graph theoretical network approach was used to visualize the genes, enzymes, and proteins involved in the signalling pathway of breast cancer and identify the significant target protein (MAPK14). A total of thirty-three active compounds were selected from S. torvum sw. through the IMPPAT database, and their structures were drawn by Chemsketch software. The drug-like behaviours of the compounds were assessed through pharmacokinetics and physicochemical characterization studies. Five compounds, namely chlorogenin (-10.90 kcal × mol-1), corosolic acid (-10.80 kcal × mol-1), solaspigenin (-10.80 kcal × mol-1), paniculogenin (-10.70 kcal × mol-1), spirostane-3,6-dione (-10.70 kcal × mol-1) exhibited top binding score against MAPK14, these are higher than that of the standard drug (Doxorubicin) (-8.60 kcal × mol-1). Additionally, the five top-binding compounds revealed better drug-likeness traits and the lowest toxicity profiles. MD simulation studies confirmed the stability of the top five scored compounds with the MAPK14 binding pockets. According to these findings, the selected five compounds might be used as significant MAPK14 inhibitors and can be used as new medicines for the treatment of breast cancer.Communicated by Ramaswamy H. Sarma.

Biomarkers of Cellular Senescence and Aging: Current State-of-the-Art, Challenges and Future Perspectives

Population aging has increased the global prevalence of aging-related diseases, including cancer, sarcopenia, neurological disease, arthritis, and heart disease. Understanding aging, a fundamental biological process, has led to breakthroughs in several fields. Cellular senescence, evinced by flattened cell bodies, vacuole formation, and cytoplasmic granules, ubiquitously plays crucial roles in tissue remodeling, embryogenesis, and wound repair as well as in cancer therapy and aging. The lack of universal biomarkers for detecting and quantifying senescent cells, in vitro and in vivo, constitutes a major limitation. The applications and limitations of major senescence biomarkers, including senescence-associated β-galactosidase staining, telomere shortening, cell-cycle arrest, DNA methylation, and senescence-associated secreted phenotypes are discussed. Furthermore, explore senotherapeutic approaches for aging-associated diseases and cancer. In addition to the conventional biomarkers, this review highlighted the in vitro, in vivo, and disease models used for aging studies. Further, technologies from the current decade including multi-omics and computational methods used in the fields of senescence and aging are also discussed in this review. Understanding aging-associated biological processes by using cellular senescence biomarkers can enable therapeutic innovation and interventions to improve the quality of life of older adults.

Alterations of receptors and insulin-like growth factor binding proteins in senescent cells

The knowledge about cellular senescence expands dynamically, providing more and more conclusive evidence of its triggers, mechanisms, and consequences. Senescence-associated secretory phenotype (SASP), one of the most important functional traits of senescent cells, is responsible for a large extent of their context-dependent activity. Both SASP's components and signaling pathways are well-defined. A literature review shows, however, that a relatively underinvestigated aspect of senescent cell autocrine and paracrine activity is the change in the production of proteins responsible for the reception and transmission of SASP signals, i.e., receptors and binding proteins. For this reason, we present in this article the current state of knowledge regarding senescence-associated changes in cellular receptors and insulin-like growth factor binding proteins. We also discuss the role of these alterations in senescence induction and maintenance, pro-cancerogenic effects of senescent cells, and aging-related structural and functional malfunctions.

Cellular senescence and SASP in tumor progression and therapeutic opportunities

Cellular senescence (CS), a permanent and irreversible arrest of the cell cycle and proliferation leading to the degeneration of cellular structure and function, has been implicated in various key physiological and pathological processes, particularly in cancer. Initially, CS was recognized as a barrier to tumorigenesis, serving as an intrinsic defense mechanism to protect cells from malignant transformation. However, increasing evidence suggests that senescent cells can promote tumor progression to overt malignancy, primarily through a set of factors known as senescence-associated secretory phenotypes (SASPs), including chemokines, growth factors, cytokines, and stromal metalloproteinases. These factors significantly reshape the tumor microenvironment (TME), enabling tumors to evade immune destruction. Interestingly, some studies have also suggested that SASPs may impede tumor development by enhancing immunosurveillance. These opposing roles highlight the complexity and heterogeneity of CS and SASPs in diverse cancers. Consequently, there has been growing interest in pharmacological interventions targeting CS or SASPs in cancer therapy, such as senolytics and senomorphics, to either promote the clearance of senescent cells or mitigate the harmful effects of SASPs. In this review, we will interpret the concept of CS, delve into the role of SASPs in reshaping the TME, and summarize recent advances in anti-tumor strategies targeting CS or SASPs.

Crosstalk between the DNA damage response and cellular senescence drives aging and age-related diseases

Cellular senescence is a crucial process of irreversible cell-cycle arrest, in which cells remain alive, but permanently unable to proliferate in response to distinct types of stressors. Accumulating evidence suggests that DNA damage builds over time and triggers DNA damage response signaling, leading to cellular senescence. Cellular senescence serves as a platform for the perpetuation of inflammatory responses and is central to numerous age-related diseases. Defects in DNA repair genes or senescence can cause premature aging disease. Therapeutic approaches limiting DNA damage or senescence contribute to a rescued phenotype of longevity and neuroprotection, thus suggesting a mechanistic interaction between DNA damage and senescence. Here, we offer a unique perspective on the crosstalk between the DNA damage response pathway and senescence as well as their contribution to age-related diseases. We further summarize recent progress on the mechanisms and therapeutics of senescence, address existing challenges, and offering new insights and future directions in the senescence field.

Quercetin induces senolysis of doxorubicin-induced senescent fibroblasts by reducing autophagy, preventing their pro-tumour effect on osteosarcoma cells

Cellular senescence contributes to ageing and age-related diseases, and multiple therapeutic strategies are being developed to counteract it. Senolytic drugs are being tested in clinical trials to eliminate senescent cells selectively, but their effects and mechanisms are still unclear. Several studies reveal that the upregulation of senescence-associated secretory phenotype (SASP) factors in senescent cells is accompanied by increased autophagic activity to counteract the endoplasmic reticulum (ER) stress. Our study shows that Doxo-induced senescent fibroblasts yield several SASP factors and exhibit increased autophagy. Interestingly, Quercetin, a bioactive flavonoid, reduces autophagy, increases ER stress, and partially triggers senescent fibroblast death. Given the role of senescent cells in cancer progression, we tested the effect of conditioned media from untreated and quercetin-treated senescent fibroblasts on osteosarcoma cells to determine whether senolytic treatment affected tumour cell behaviour. We report that the partial senescent fibroblast clearance, achieved by quercetin, reduced osteosarcoma cell invasiveness, curbing the pro-tumour effects of senescent cells. The reduction of cell autophagic activity and increased ER stress, an undescribed effect of quercetin, emerges as a new vulnerability of Doxo-induced senescent fibroblasts and may provide a potential therapeutic target for cancer treatment, suggesting novel drug combinations as a promising strategy against the tumour.

Therapy-induced senescence through the redox lens

Therapy-induced senescent tumor cells have emerged as significant drivers of tumor recurrence and disease relapse. Interestingly, reactive oxygen species (ROS) production and its associated redox signaling networks are intertwined with initiation and establishment of therapy-induced senescence. Therapy-induced senescent cells influence neighboring cells and the tumor microenvironment via their bioactive secretome known as the senescence-associated secretory phenotype (SASP). The intracellular effects of ROS are dose and context-dependent. Under normal physiological conditions, ROS is involved in various signalling pathways and cellular processes important for maintenance of cellular homeostasis, such as redox balance, stress response, inflammatory signalling, cell proliferation and cell death among others. However excess ROS accompanied by a pro-oxidant microenvironment can engender oxidative DNA damage, triggering cellular senescence. In this review, we discuss the role of ROS and the redox state dynamics in fine-tuning homeostatic processes that drive therapy-induced cell fate towards senescence establishment, as well as their influence in stimulating inflammatory signalling and SASP production. We also offer insights into interventional strategies, specifically senotherapeutics, that could potentially leverage on modulation of redox and antioxidant pathways. Lastly, we evaluate possible implications of redox rewiring during escape from therapy-induced senescence, an emerging area of research. We envision that examining therapy-induced senescence through the redox lens, integrated with time-resolved single-cell RNA sequencing combined with spatiotemporal multi-omics, could further enhance our understanding of its functional heterogeneity. This could aid identification of targetable signalling nodes to reduce disease relapse, as well as inform strategies for development of broad-spectrum senotherapeutics. Overall, our review aims to delineate redox-driven mechanisms which contribute to the biology of therapy-induced senescence and beyond, while highlighting implications for tumor initiation and recurrence.

Senolytics and Senomorphics Targeting p38MAPK/NF-κB Pathway Protect Endothelial Cells from Oxidative Stress-Mediated Premature Senescence

Oxidative stress is a prominent causal factor in the premature senescence of microvascular endothelial cells and the ensuing blood-brain barrier (BBB) dysfunction. Through the exposure of an in vitro model of human BBB, composed of brain microvascular endothelial cells (BMECs), astrocytes, and pericytes to H2O2, this study examined whether a specific targeting of the p38MAPK/NF-κB pathway and/or senescent cells could delay oxidative stress-mediated EC senescence and protect the BBB. Enlarged BMECs, displaying higher β-galactosidase activity, γH2AX staining, p16 expression, and impaired tubulogenic capacity, were regarded as senescent. The BBB established with senescent BMECs had reduced transendothelial electrical resistance and increased paracellular flux, which are markers of BBB integrity and function, respectively. Premature senescence disrupted plasma-membrane localization of the tight junction protein, zonula occludens-1, and elevated basement membrane-degrading matrix metalloproteinase-2 activity and pro-inflammatory cytokine release. Inhibition of p38MAPK by BIRB796 and NF-κB by QNZ and the elimination of senescent cells by a combination of dasatinib and quercetin attenuated the effects of H2O2 on senescence markers; suppressed release of the pro-inflammatory cytokines interleukin-8, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1; restored tight junctional unity; and improved BBB function. In conclusion, therapeutic approaches that mitigate p38MAPK/NF-κB activity and senescent cell accumulation in the cerebrovasculature may successfully protect BBB from oxidative stress-induced BBB dysfunction.

Cellular Senescence and Inflammaging in the Bone: Pathways, Genetics, Anti-Aging Strategies and Interventions

Advancing age is associated with several age-related diseases (ARDs), with musculoskeletal conditions impacting millions of elderly people worldwide. With orthopedic conditions contributing towards considerable number of patients, a deeper understanding of bone aging is the need of the hour. One of the underlying factors of bone aging is cellular senescence and its associated senescence associated secretory phenotype (SASP). SASP comprises of pro-inflammatory markers, cytokines and chemokines that arrest cell growth and development. The accumulation of SASP over several years leads to chronic low-grade inflammation with advancing age, also known as inflammaging. The pathways and molecular mechanisms focused on bone senescence and inflammaging are currently limited but are increasingly being explored. Most of the genes, pathways and mechanisms involved in senescence and inflammaging coincide with those associated with cancer and other ARDs like osteoarthritis (OA). Thus, exploring these pathways using techniques like sequencing, identifying these factors and combatting them with the most suitable approach are crucial for healthy aging and the early detection of ARDs. Several approaches can be used to aid regeneration and reduce senescence in the bone. These may be pharmacological, non-pharmacological and lifestyle interventions. With increasing evidence towards the intricate relationship between aging, senescence, inflammation and ARDs, these approaches may also be used as anti-aging strategies for the aging bone marrow (BM).

Regulation of ENPP5, a senescence-associated secretory phenotype factor, prevents skin aging

Aging negatively affects the appearance and texture of the skin owing to the accumulation of senescent fibroblasts within the dermis. Senescent cells undergo abnormal remodeling of collagen and the extracellular matrix through an inflammatory histolytic senescence-associated secretory phenotype (SASP). Therefore, suppression of SASP in senescent cells is essential for the development of effective skin anti-aging therapies. Ectonucleotide pyrophosphatase/phosphodiesterase family member 5 (ENPP5), an extracellular signaling molecule, has been implicated in vascular aging and apoptosis; however, its role in SASP remains unclear. Therefore, this study aimed to investigate the role of ENPP5 in SASP and skin aging using molecular techniques. We investigated the effects of siRNA-mediated ENPP5 knockdown, human recombinant ENPP5 (rENPP5) treatment, and lentiviral overexpression of ENPP5 on SASP and aging in human skin fibroblasts. Additionally, we investigated the effect of siRNA-mediated ENPP5 knockdown on the skin of C57BL/6 mice. We found that ENPP5 was significantly expressed in replication-aged and otherwise DNA-damaged human skin fibroblasts and that treatment with human rENPP5 and lentiviral overexpression of ENPP5 promoted SASP and senescence. By contrast, siRNA-mediated knockdown of ENPP5 suppressed SASP and the expression of skin aging-related factors. Additionally, ENPP5 knockdown in mouse skin ameliorated the age-related reduction of subcutaneous adipose tissue, the panniculus carnosus muscle layer, and thinning of collagen fibers. Conclusively, these findings suggest that age-related changes may be prevented through the regulation of ENPP5 expression to suppress SASP in aging cells, contributing to the development of anti-aging treatments for the skin.

LXR/CD38 activation drives cholesterol-induced macrophage senescence and neurodegeneration via NAD+ depletion

Although dysregulated cholesterol metabolism predisposes aging tissues to inflammation and a plethora of diseases, the underlying molecular mechanism remains poorly defined. Here, we show that metabolic and genotoxic stresses, convergently acting through liver X nuclear receptor, upregulate CD38 to promote lysosomal cholesterol efflux, leading to nicotinamide adenine dinucleotide (NAD+) depletion in macrophages. Cholesterol-mediated NAD+ depletion induces macrophage senescence, promoting key features of age-related macular degeneration (AMD), including subretinal lipid deposition and neurodegeneration. NAD+ augmentation reverses cellular senescence and macrophage dysfunction, preventing the development of AMD phenotype. Genetic and pharmacological senolysis protect against the development of AMD and neurodegeneration. Subretinal administration of healthy macrophages promotes the clearance of senescent macrophages, reversing the AMD disease burden. Thus, NAD+ deficit induced by excess intracellular cholesterol is the converging mechanism of macrophage senescence and a causal process underlying age-related neurodegeneration.

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.

Cutaneous Redox Senescence

Our current understanding of skin cell senescence involves the role of environmental stressors (UV, O3, cigarette smoke, particulate matter, etc.), lifestyle (diet, exercise, etc.) as well as genetic factors (metabolic changes, hormonal, etc.). The common mechanism of action of these stressors is the disturbance of cellular redox balance characterized by increased free radicals and reactive oxygen species (ROS), and when these overload the intrinsic antioxidant defense system, it can lead to an oxidative stress cellular condition. The main redox mechanisms that activate cellular senescence in the skin involve (1) the oxidative damage of telomeres causing their shortening; (2) the oxidation of proteomes and DNA damage; (3) an a in lysosomal mass through the increased activity of resident enzymes such as senescence-associated β-galactosidase (SA-β-gal) as well as other proteins that are products of lysosomal activity; (4) and the increased expression of SASP, in particular pro-inflammatory cytokines transcriptionally regulated by NF-κB. However, the main targets of ROS on the skin are the proteome (oxi-proteome), followed by telomeres, nucleic acids (DNAs), lipids, proteins, and cytoplasmic organelles. As a result, cell cycle arrest pathways, lipid peroxidation, increased lysosomal content and dysfunctional mitochondria, and SASP synthesis occur. Furthermore, oxidative stress in skin cells increases the activity of p16INK4A and p53 as inhibitors of Rb and CDks, which are important for maintaining the cell cycle. p53 also promotes the inactivation of mTOR-mediated autophagic and apoptotic pathways, leading to senescence. However, these markers alone cannot establish the state of cellular senescence, and multiple analyses are encouraged for confirmation. An updated and more comprehensive approach to investigating skin senescence should include further assays of ox-inflammatory molecular pathways that can consolidate the understanding of cutaneous redox senescence.

Understanding cellular senescence: pathways involved, therapeutics and longevity aiding

A normal somatic cell undergoes cycles of finite cellular divisions. The presence of surveillance checkpoints arrests cell division in response to stress inducers: oxidative stress from excess free radicals, oncogene-induced abnormalities, genotoxic stress, and telomere attrition. When facing such stress when undergoing these damages, there is a brief pause in the cell cycle to enable repair mechanisms. Also, the nature of stress determines whether the cell goes for repair or permanent arrest. As the cells experience transient or permanent stress, they subsequently choose the quiescence or senescence stage, respectively. Quiescence is an essential stage that allows the arrested/damaged cells to go through appropriate repair mechanisms and then revert to the mainstream cell cycle. However, senescent cells are irreversible and accumulate with age, resulting in inflammation and various age-related disorders. In this review, we focus on senescence-associated pathways and therapeutics understanding cellular senescence as a cascade that leads to aging, while discussing the recent details on the molecular pathways involved in regulating senescence and the benefits of therapeutic strategies against accumulated senescent cells and their secretions.

New Possibilities for Evaluating the Development of Age-Related Pathologies Using the Dynamical Network Biomarkers Theory

Aging is the slowest process in a living organism. During this process, mortality rate increases exponentially due to the accumulation of damage at the cellular level. Cellular senescence is a well-established hallmark of aging, as well as a promising target for preventing aging and age-related diseases. However, mapping the senescent cells in tissues is extremely challenging, as their low abundance, lack of specific markers, and variability arise from heterogeneity. Hence, methodologies for identifying or predicting the development of senescent cells are necessary for achieving healthy aging. A new wave of bioinformatic methodologies based on mathematics/physics theories have been proposed to be applied to aging biology, which is altering the way we approach our understand of aging. Here, we discuss the dynamical network biomarkers (DNB) theory, which allows for the prediction of state transition in complex systems such as living organisms, as well as usage of Raman spectroscopy that offers a non-invasive and label-free imaging, and provide a perspective on potential applications for the study of aging.

The aged extracellular matrix and the profibrotic role of senescence-associated secretory phenotype

Idiopathic pulmonary fibrosis (IPF) is an irreversible and fatal lung disease that is primarily found in the elderly population, and several studies have demonstrated that aging is the major risk factor for IPF. IPF is characterized by the presence of apoptosis-resistant, senescent fibroblasts that generate an excessively stiff extracellular matrix (ECM). The ECM profoundly affects cellular functions and tissue homeostasis, and an aberrant ECM is closely associated with the development of lung fibrosis. Aging progressively alters ECM components and is associated with the accumulation of senescent cells that promote age-related tissue dysfunction through the expression of factors linked to a senescence-associated secretary phenotype (SASP). There is growing evidence that SASP factors affect various cell behaviors and influence ECM turnover in lung tissue through autocrine and/or paracrine signaling mechanisms. Since life expectancy is increasing worldwide, it is important to elucidate how aging affects ECM dynamics and turnover via SASP and thereby promotes lung fibrosis. In this review, we will focus on the molecular properties of SASP and its regulatory mechanisms. Furthermore, the pathophysiological process of ECM remodeling by SASP factors and the influence of an altered ECM from aged lungs on the development of lung fibrosis will be highlighted. Finally, recent attempts to target ECM alteration and senescent cells to modulate fibrosis will be introduced.NEW & NOTEWORTHY Aging is the most prominent nonmodifiable risk factor for various human diseases including Idiopathic pulmonary fibrosis. Aging progressively alters extracellular matrix components and is associated with the accumulation of senescent cells that promote age-related tissue dysfunction. In this review, we will discuss the pathological impact of aging and senescence on lung fibrosis via senescence-associated secretary phenotype factors and potential therapeutic approaches to limit the progression of lung fibrosis.

Senescence in cancer: Advances in detection and treatment modalities

Senescence is a form of irreversible cell cycle arrest. Senescence plays a dual role in cancer, as both a tumor suppressor by preventing the growth of damaged cells and a cancer promoter by creating an inflammatory milieu. Stress-induced premature senescence (SIPS) and replicative senescence are the two major sub-types of senescence. Senescence plays a dual role in cancer, depending on the context and kind of senescence involved. SIPS can cause cancer by nurturing an inflammatory environment, whereas replicative senescence may prevent cancer. Major pathways that are involved in senescence are the p53-p21, p16INK4A-Rb pathway along with mTOR, MAPK, and PI3K pathways. The lack of universal senescence markers makes it difficult to identify senescent cells in vivo. A combination of reliable detection methods of senescent cells in vivo is of utmost importance and will help in early detection and open new avenues for future treatment. New strategies that are being developed in order to tackle these shortcomings are in the field of fluorescent probes, nanoparticles, positron emission tomography probes, biosensors, and the detection of cell-free DNA from liquid biopsies. Along with detection, eradication of these senescent cells is also important to prevent cancer reoccurrence. Recently, the field of nano-senolytic and immunotherapy has also been emerging. This review provides up-to-date information on the various types of advancements made in the field of detection and treatment modalities for senescent cells that hold promise for the future treatment and prognosis of cancer, as well as their limitations and potential solutions.

Vascular Ageing: Mechanisms, Risk Factors, and Treatment Strategies

Ageing constitutes the biggest risk factor for poor health and adversely affects the integrity and function of all the cells, tissues, and organs in the human body. Vascular ageing, characterised by vascular stiffness, endothelial dysfunction, increased oxidative stress, chronic low-grade inflammation, and early-stage atherosclerosis, may trigger or exacerbate the development of age-related vascular diseases, which each year contribute to more than 3.8 million deaths in Europe alone and necessitate a better understanding of the mechanisms involved. To this end, a large number of recent preclinical and clinical studies have focused on the exponential accumulation of senescent cells in the vascular system and paid particular attention to the specific roles of senescence-associated secretory phenotype, proteostasis dysfunction, age-mediated modulation of certain microRNA (miRNAs), and the contribution of other major vascular risk factors, notably diabetes, hypertension, or smoking, to vascular ageing in the elderly. The data generated paved the way for the development of various senotherapeutic interventions, ranging from the application of synthetic or natural senolytics and senomorphics to attempt to modify lifestyle, control diet, and restrict calorie intake. However, specific guidelines, considering the severity and characteristics of vascular ageing, need to be established before widespread use of these agents. This review briefly discusses the molecular and cellular mechanisms of vascular ageing and summarises the efficacy of widely studied senotherapeutics in the context of vascular ageing.

The central role of DNA damage in immunosenescence

Ageing is the biggest risk factor for the development of multiple chronic diseases as well as increased infection susceptibility and severity of diseases such as influenza and COVID-19. This increased disease risk is linked to changes in immune function during ageing termed immunosenescence. Age-related loss of immune function, particularly in adaptive responses against pathogens and immunosurveillance against cancer, is accompanied by a paradoxical gain of function of some aspects of immunity such as elevated inflammation and increased incidence of autoimmunity. Of the many factors that contribute to immunosenescence, DNA damage is emerging as a key candidate. In this review, we discuss the evidence supporting the hypothesis that DNA damage may be a central driver of immunosenescence through senescence of both immune cells and cells of non-haematopoietic lineages. We explore why DNA damage accumulates during ageing in a major cell type, T cells, and how this may drive age-related immune dysfunction. We further propose that existing immunosenescence interventions may act, at least in part, by mitigating DNA damage and restoring DNA repair processes (which we term "genoprotection"). As such, we propose additional treatments on the basis of their evidence for genoprotection, and further suggest that this approach may provide a viable therapeutic strategy for improving immunity in older people.

Exploring the Communication of the SASP: Dynamic, Interactive, and Adaptive Effects on the Microenvironment

Cellular senescence is a complex cell state that can occur during physiological ageing or after exposure to stress signals, regardless of age. It is a dynamic process that continuously evolves in a context-dependent manner. Senescent cells interact with their microenvironment by producing a heterogenous and plastic secretome referred to as the senescence-associated secretory phenotype (SASP). Hence, understanding the cross-talk between SASP and the microenvironment can be challenging due to the complexity of signal exchanges. In this review, we first aim to update the definition of senescence and its associated biomarkers from its discovery to the present day. We detail the regulatory mechanisms involved in the expression of SASP at multiple levels and develop how SASP can orchestrate microenvironment modifications, by focusing on extracellular matrix modifications, neighboring cells' fate, and intercellular communications. We present hypotheses on how these microenvironmental events may affect dynamic changes in SASP composition in return. Finally, we discuss the various existing approaches to targeting SASP and clarify what is currently known about the biological effects of these modified SASPs on the cellular environment.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Targeting mTOR for Anti-Aging and Anti-Cancer Therapy

The balance between anabolism and catabolism is disrupted with aging, with the rate of anabolism being faster than that of catabolism. Therefore, mTOR, whose major function is to enhance anabolism and inhibit catabolism, has become a potential target of inhibition for anti-aging therapy. Interestingly, it was found that the downregulation of the mTOR signaling pathway had a lifespan-extending effect resembling calorie restriction. In addition, the mTOR signaling pathway promotes cell proliferation and has been regarded as a potential anti-cancer target. Rapamycin and rapalogs, such as everolimus, have proven to be effective in preventing certain tumor growth. Here, we reviewed the basic knowledge of mTOR signaling, including both mTORC1 and mTORC2. Then, for anti-aging, we cited a lot of evidence to discuss the role of targeting mTOR and its anti-aging mechanism. For cancer therapy, we also discussed the role of mTOR signaling in different types of cancers, including idiopathic pulmonary fibrosis, tumor immunity, etc. In short, we discussed the research progress and both the advantages and disadvantages of targeting mTOR in anti-aging and anti-cancer therapy. Hopefully, this review may promote more ideas to be generated for developing inhibitors of mTOR signaling to fight cancer and extend lifespan.

Advances in cellular senescence in idiopathic pulmonary fibrosis (Review)

Idiopathic pulmonary fibrosis (IPF) is a progressive, irreversible and fatal interstitial lung disease of unknown cause, with a median survival of 2-3 years. Its pathogenesis is unclear and there is currently no effective treatment for IPF. Approximately two-thirds of patients with IPF are >60 years old, with a mean age of 66 years, suggesting a link between aging and IPF. However, the mechanism by which aging promotes development of PF remains unclear. Senescence of alveolar epithelial cells and lung fibroblasts (LFs) and their senescence-associated secretion phenotype (SASP) may be involved in the occurrence and development of IPF. The present review focus on senescence of LFs and epithelial and stem cells, as well as SASP, the activation of profibrotic signaling pathways and potential treatments for pathogenesis of IPF.

Emerging Therapeutic Approaches to Target the Dark Side of Senescent Cells: New Hopes to Treat Aging as a Disease and to Delay Age-Related Pathologies

Life expectancy has drastically increased over the last few decades worldwide, with important social and medical burdens and costs. To stay healthy longer and to avoid chronic disease have become essential issues. Organismal aging is a complex process that involves progressive destruction of tissue functionality and loss of regenerative capacity. One of the most important aging hallmarks is cellular senescence, which is a stable state of cell cycle arrest that occurs in response to cumulated cell stresses and damages. Cellular senescence is a physiological mechanism that has both beneficial and detrimental consequences. Senescence limits tumorigenesis, lifelong tissue damage, and is involved in different biological processes, such as morphogenesis, regeneration, and wound healing. However, in the elderly, senescent cells increasingly accumulate in several organs and secrete a combination of senescence associated factors, contributing to the development of various age-related diseases, including cancer. Several studies have revealed major molecular pathways controlling the senescent phenotype, as well as the ones regulating its interactions with the immune system. Attenuating the senescence-associated secretory phenotype (SASP) or eliminating senescent cells have emerged as attractive strategies aiming to reverse or delay the onset of aging diseases. Here, we review current senotherapies designed to suppress the deleterious effect of SASP by senomorphics or to selectively kill senescent cells by "senolytics" or by immune system-based approaches. These recent investigations are promising as radical new controls of aging pathologies and associated multimorbidities.

Cellular rejuvenation: molecular mechanisms and potential therapeutic interventions for diseases

The ageing process is a systemic decline from cellular dysfunction to organ degeneration, with more predisposition to deteriorated disorders. Rejuvenation refers to giving aged cells or organisms more youthful characteristics through various techniques, such as cellular reprogramming and epigenetic regulation. The great leaps in cellular rejuvenation prove that ageing is not a one-way street, and many rejuvenative interventions have emerged to delay and even reverse the ageing process. Defining the mechanism by which roadblocks and signaling inputs influence complex ageing programs is essential for understanding and developing rejuvenative strategies. Here, we discuss the intrinsic and extrinsic factors that counteract cell rejuvenation, and the targeted cells and core mechanisms involved in this process. Then, we critically summarize the latest advances in state-of-art strategies of cellular rejuvenation. Various rejuvenation methods also provide insights for treating specific ageing-related diseases, including cellular reprogramming, the removal of senescence cells (SCs) and suppression of senescence-associated secretory phenotype (SASP), metabolic manipulation, stem cells-associated therapy, dietary restriction, immune rejuvenation and heterochronic transplantation, etc. The potential applications of rejuvenation therapy also extend to cancer treatment. Finally, we analyze in detail the therapeutic opportunities and challenges of rejuvenation technology. Deciphering rejuvenation interventions will provide further insights into anti-ageing and ageing-related disease treatment in clinical settings.

Involvement of p38 MAPK in Leydig cell aging and age-related decline in testosterone

Introduction

Age-related decline in testosterone is associated with Leydig cell aging with impaired testosterone synthesis in aging. Obesity accelerates the age-related decline in testosterone. However, the mechanisms underlying the Leydig cell aging and the effects of obesity on Leydig cell aging remain unclear.

Method

Natural aging mice and diet-induced obese mice were used to assess the process of testicular Leydig cell senescence with age or obesity. Bioinformatic analysis of the young and aged human testes was used to explore key genes related Leydig cell aging. Leydig cell-specific p38 MAPK knockout (p38LCKO) mice were used to further analyze the roles of p38 MAPK in Leydig cell aging. The levels of testosterone and steroidogenic enzymes, activity of p38 MAPK, aging status of Leydig cells, and oxidative stress and inflammation of testes or Leydig cells were detected by ELISA, immunoblotting, immunofluorescence, and senescence-associated β-galactosidase (SA-β-Gal) staining analysis, respectively.

Result

The serum testosterone level was significantly reduced in aged mice compared with young mice. In the testis of aged mice, the reduced mRNA and protein levels of LHCGR, SRB1, StAR, CYP11A1, and CYP17A1 and the elevated oxidative stress and inflammation were observed. KEGG analysis showed that MAPK pathway was changed in aged Leydig cells, and immunoblotting displayed that p38 MAPK was activated in aged Leydig cells. The intensity of SA-β-Gal staining on Leydig cells and the number of p21-postive Leydig cells in aged mice were more than those of young mice. Similar to aged mice, the testosterone-related indexes decreased, and the age-related indexes increased in the testicular Leydig cells of high fat diet (HFD) mice. Aged p38LCKO mice had higher levels of testosterone and steroidogenic enzymes than those of age-matched wild-type (WT) littermates, with reduced the intensity of SA-β-Gal staining and the expression of p21 protein.

Conclusion

Our study suggested that obesity was an important risk factor for Leydig cell aging. p38 MAPK was involved in Leydig cell aging induced by age and obesity. The inhibition of p38 MAPK could delay Leydig cell aging and alleviate decline in testosterone.

Targeting cellular senescence with senotherapeutics: senolytics and senomorphics

The concept of geroscience is that since ageing is the greatest risk factor for many diseases and conditions, targeting the ageing process itself will have the greatest impact on human health. Of the hallmarks of ageing, cellular senescence has emerged as a druggable therapeutic target for extending healthspan in model organisms. Cellular senescence is a cell state of irreversible proliferative arrest driven by different types of stress, including oncogene-induced stress. Many senescent cells (SnCs) develop a senescent-associated secretory phenotype (SASP) comprising pro-inflammatory cytokines, chemokines, proteases, bioactive lipids, inhibitory molecules, extracellular vesicles, metabolites, lipids and other factors, able to promote chronic inflammation and tissue dysfunction. SnCs up-regulate senescent cell anti-apoptotic pathways (SCAPs) that prevent them from dying despite the accumulation of damage to DNA and other organelles. These SCAPs and other pathways altered in SnCs represent therapeutic targets for the development of senotherapeutic drugs that induce selective cell death of SnCs, specifically termed senolytics or suppress markers of senescence, in particular the SASP, termed senomorphics. Here, we review the current state of the development of senolytics and senomorphics for the treatment of age-related diseases and disorders and extension of healthy longevity. In addition, the challenges of documenting senolytic and senomorphic activity in pre-clinical models and the current state of the clinical application of the different senotherapeutics will be discussed.

Heterogenous Differences in Cellular Senescent Phenotypes in Pre-Eclampsia and IUGR following Quantitative Assessment of Multiple Biomarkers of Senescence

Premature ageing of the placenta in pregnancy outcomes is associated with the persistent presence of oxidative stress and placental insufficiency reducing its functional capacity. In this study, we investigated cellular senescence phenotypes of pre-eclampsia and IUGR pregnancies by simultaneously measuring several biomarkers of senescence. Maternal plasma and placental samples were collected at term gestation from nulliparous women undergoing pre-labour elective caesarean section with pre-eclampsia without intrauterine growth restriction (PE; n = 5), pre-eclampsia associated with intrauterine growth restriction (n = 8), intrauterine growth restriction (IUGR < 10th centile; n = 6), and age-matched controls (n = 20). Placental absolute telomere length and senescence gene analysis was performed by RTqPCR. The expression of cyclin-dependent kinase inhibitors (p21 and p16) was determined by Western blot. Senescence-associated secretory phenotypes (SASPs) were evaluated in maternal plasma by multiplex ELISA assay. Placental expression of senescence-associated genes showed significant increases in CHEK1, PCNA, PTEN, CDKN2A, and CCNB-1 (p < 0.05) in pre-eclampsia, while TBX-2, PCNA, ATM, and CCNB-1 expression were evident (p < 0.05) and were significantly decreased in IUGR compared with controls. Placental p16 protein expression was significantly decreased in pre-eclampsia only compared with controls (p = 0.028). IL-6 was significantly increased in pre-eclampsia (0.54 pg/mL ± 0.271 vs. 0.3 pg/mL ± 0.102; p = 0.017) while IFN-γ was significantly increased in IUGR (4.6 pg/mL ± 2.2 vs. 2.17 pg/mL ± 0.8; p = 0.002) compared with controls. These results provide evidence of premature senescence in IUGR pregnancies, and while cell cycle checkpoint regulators are activated in pre-eclampsia, the cellular phenotype is one of cell repair and subsequent proliferation rather than progression to senescence. The heterogeneity of these cellular phenotypes highlights the complexity of characterising cellular senescence and may equally be indicative of the differing pathophysiological insults unique to each obstetric complication.

Therapeutic Opportunities Presented by Modulation of Cellular Senescence

Cellular senescence is a permanent state of growth arrest coupled with profound changes in phenotype that can be triggered by multiple extrinsic or intrinsic stimuli. Senescence is a process-level example of the evolution of ageing mechanisms through antagonistic pleiotropy and plays a primary role in tumour suppression, although evidence is mounting for its involvement in other fundamental physiological processes. Evidence from human premature ageing diseases and from transgenic mice in which it is possible to specifically delete senescent cells is consistent with a model in which the accumulation of senescent cells through the life course is responsible for later life chronic disease and impairment. The removal of senescent cells or their reversion to a phenotypically benign state is thus an important emerging goal of translational medicine.Modern bioinformatic approaches based on text mining have compiled co-mentions of cell senescence and age-related diseases allowing an impartial ranking of the impairments most closely associated with this process. Following this schema, the evidence for the involvement of senescence in several highly ranked pathologies is reviewed, alongside potential methods for the ablation of senescent cells or their reversion to their primary phenotype with polyphenolics or inhibitors of p38 MAP kinase. Lastly, the potential for senescence to act as a barrier to the development of bioartificial organs designed to treat some of these conditions is discussed.

Translating the Biology of Aging into New Therapeutics for Alzheimer's Disease: Senolytics

The recent FDA-approval for amyloid lowering therapies reflects an unwavering commitment from the Alzheimer's disease (AD) research community to identify treatments for this leading cause of dementia. The clinical benefits achieved by reducing amyloid, though modest, provide evidence that disease modification is possible. Expanding the same tenacity to interventions targeting upstream drivers of AD pathogenesis could significantly impact the disease course. Advanced age is the greatest risk factor for developing AD. Interventions targeting biological aging offer the possibility of disrupting a foundational cause of AD. Senescent cells accumulate with age and contribute to inflammation and age-related diseases like AD. Senolytic drugs that clear senescent cells improve healthy aging, halt AD disease progression in animal models and are undergoing clinical testing. This review explores the biology of aging, the role of senescent cells in AD pathology, and various senotherapeutic approaches such as senolytics, dampening the SASP (senescence associated secretory phenotype), senescence pathway inhibition, vaccines, and prodrugs. We highlight ongoing clinical trials evaluating the safety and efficacy of the most advanced senolytic approach, dasatinib and quercetin (D+Q), including an ongoing Phase II senolytic trial supported by the Alzheimer's Drug Discovery Foundation (ADDF). Challenges in the field of senotherapy for AD, including target engagement and biomarker development, are addressed. Ultimately, this research pursuit may lead to an effective treatment for AD and provide the field with another disease-modifying therapy to be used, alone or in combination, with other emerging treatment options.

Cellular Senescence in Hepatocellular Carcinoma: The Passenger or the Driver?

With the high morbidity and mortality, hepatocellular carcinoma (HCC) represents a major yet growing burden for our global community. The relapse-prone nature and drug resistance of HCC are regarded as the consequence of varying intracellular processes and extracellular interplay, which actively participate in tumor microenvironment remodeling. Amongst them, cellular senescence is regarded as a fail-safe program, leading to double-sword effects of both cell growth inhibition and tissue repair promotion. Particularly, cellular senescence serves a pivotal role in the progression of chronic inflammatory liver diseases, ultimately leading to carcinogenesis. Given the current challenges in improving the clinical management and outcome of HCC, senescence may exert striking potential in affecting anti-cancer strategies. In recent years, an increasing number of studies have emerged to investigate senescence-associated hepatocarcinogenesis and its derived therapies. In this review, we intend to provide an up-to-date understanding of liver cell senescence and its impacts on treatment modalities of HCC.

Stress signaler p38 mitogen-activated kinase activation: a cause for concern?

Oxidative stress (OS) induced activation of p38 mitogen-activated kinase (MAPK) and cell fate from p38 signaling was tested using the human fetal membrane's amnion epithelial cells (AEC). We created p38 KO AEC using the CRISPR/Cas9 approach and tested cell fate in response to OS on an AEC-free fetal membrane extracellular matrix (ECM). Screening using image CyTOF indicated OS causing epithelial-mesenchymal transition (EMT). Further testing revealed p38 deficiency prevented AEC senescence, EMT, cell migration, and inflammation. To functionally validate in vitro findings, fetal membrane-specific conditional KO (cKO) mice were developed by injecting Cre-recombinase encoded exosomes intra-amniotically into p38αloxP/loxP mice. Amnion membranes from p38 cKO mice had reduced senescence, EMT, and increased anti-inflammatory IL-10 compared with WT animals. Our study suggested that overwhelming activation of p38 in response to OS inducing risk exposures can have an adverse impact on cells, cause cell invasion, inflammation, and ECM degradation detrimental to tissue homeostasis.

The diseased kidney: aging and senescent immunology

Immunosenescence is the deterioration of the innate and adaptive immune systems associated with aging and is primarily characterized by a reduction in T cell production and accumulation of atypical subsets. Age-related immunological dysfunction leads to impaired immune protection and persistent low-grade chronic inflammation, resulting in a decreased vaccination response and increased vulnerability to infection, cancer, cardiovascular disease, and autoimmune disease in the elderly. As the elderly constitute a growing proportion of the population with renal disease, immunosenescence is a normal aging process that is prevalent among older people. In addition, immunosenescence seems to be more pronounced in patients with kidney diseases than in healthy controls, as shown by severe chronic inflammation, accumulation of immune cells with the senescent phenotype (CD28− T cells, CD14+CD16+ monocytes), and proinflammatory cytokine production. Immunosenescence inhibits immunological clearance and renal tissue regeneration, thereby increasing the risk of permanent renal damage, infection, and cardiovascular events in patients with kidney disease, lowering the prognosis, and even influencing the efficacy of renal replacement treatment. Biological drugs (senomorphics and senolytics) target the aging immune system and exert renoprotective effects. This review aims to emphasize the features of immunosenescence and its influence on kidney diseases and immunotherapy, highlighting the future directions of kidney disease treatment using senescence-focused techniques.

Senescence and the tumor-immune landscape: Implications for cancer immunotherapy

Cancer therapies, including conventional chemotherapy, radiation, and molecularly targeted agents, can lead to tumor eradication through a variety of mechanisms. In addition to their effects on tumor cell growth and survival, these regimens can also influence the surrounding tumor-immune microenvironment in ways that ultimately impact therapy responses. A unique biological outcome of cancer therapy is induction of cellular senescence. Senescence is a damage-induced stress program that leads to both the durable arrest of tumor cells and remodeling the tumor-immune microenvironment through activation of a collection pleiotropic cytokines, chemokines, growth factors, and proteinases known as the senescence-associated secretory phenotype (SASP). Depending on the cancer context and the mechanism of action of the therapy, the SASP produced following therapy-induced senescence (TIS) can promote anti-tumor immunity that enhances therapeutic efficacy, or alternatively chronic inflammation that leads to therapy failure and tumor relapse. Thus, a deeper understanding of the mechanisms regulating the SASP and components necessary for robust anti-tumor immune surveillance in different cancer and therapy contexts are key to harnessing senescence for tumor control. Here we draw a roadmap to modulate TIS and its immune-stimulating features for cancer immunotherapy.