Serine Metabolism Controls Dental Pulp Stem Cell Aging by Regulating the DNA Methylation of p16

Serine Metabolism Regulates the Replicative Senescence of Human Dental Pulp Cells through Histone Methylation

Tissue regeneration therapy based on human dental pulp cells (hDPCs) faces the distinct challenge of cellular senescence during massive expansion in vitro. To further explore the regulatory mechanism of cellular senescence in hDPCs, we conduct experiments on young cells (Passage 5, P5) and replicative senescent (Passage 12, P12) hDPCs. The results confirm that hDPCs undergo replicative senescence with passaging, during which their ability to proliferate and osteogenic differentiation decreases. Notably, during replicative senescence, phosphoglycerate dehydrogenase (PHGDH), the key enzyme of the serine synthesis pathway (SSP), is significantly downregulated, as well as S-adenosylmethionine (SAM) levels, resulting in reduced H3K36me3 modification on Sirtuin 1 (SIRT1)and Runt-related transcription factor 2 (RUNX2) promoters. Inhibition of PHGDH leads to the same phenotype as replicative senescence. Serine supplementation fails to rescue the senescence phenotype caused by replicative senescence and inhibitors, in which folate metabolism-related genes, including serine hydroxymethyl transferase 2 (SHMT2), methylenetetrahydrofolate dehydrogenase 1(MTHFD1), methylenetetrahydrofolate dehydrogenase 2(MTHFD2), are notably decreased. Our research raised a possibility that PHGDH may be involved in cellular senescence by affecting folate metabolism and histone methylation in addition to serine biosynthesis, providing potential targets to prevent senescence.

Lysine demethylase 3A promotes chondrogenic differentiation of aged human dental pulp stem cells

Background/purpose

Aging severely impairs the beneficial effects of human dental pulp stem cells (hDPSCs) on cartilage regeneration. Lysine demethylase 3A (KDM3A) is involved in regulating mesenchymal stem cells (MSCs) senescence and bone aging. In this study, we investigated the role of KDM3A in hDPSCs aging and whether KDM3A could rejuvenate aged hDPSCs to enhance their chondrogenic differentiation capacity.

Materials and methods

The cellular aging of hDPSCs was evaluated by senescence-associated β-galactosidase (SA-β-gal) staining. Protein levels were determined using Western blot analysis. KDM3A was overexpressed in aged hDPSCs by lentivirus infection. Quantitative reverse-transcription polymerase chain reaction (RT-qPCR) were used to determine the mRNA levels of stemness markers. Toluidine blue staining was used to evaluate the effect of KDM3A overexpression on the chondrogenic differentiation of aged hDPSCs.

Results

hDPSCs at passage 12 or treated with etoposide exhibited augmented cellular senescence as evidenced by increased SA-β-gal activity. KDM3A was significantly increased during senescence of hDPSCs. Overexpression of KDM3A did not affect the stemness properties but significantly promoted the chondrogenic differentiation of aged hDPSCs.

Conclusion

Our findings indicate that KDM3A plays an important role in the maintenance of the chondrogenic differentiation capacity of aged hDPSCs and suggest that therapies targeting KDM3A may be a novel strategy to rejuvenate aged hDPSCs.

Serine deficiency exacerbates psoriatic skin inflammation by regulating S-adenosyl methionine-dependent DNA methylation and NF-κB signalling activation in keratinocytes

BACKGROUND

Serine metabolism is crucial for tumour oncogenesis and immune responses. S-adenosyl methionine (SAM), a methyl donor, is typically derived from serine-driven one-carbon metabolism. However, the involvement of serine metabolism in psoriatic skin inflammation remains unclear.

OBJECTIVES

To investigate the association between serine metabolism and psoriatic skin inflammation.

METHODS

Clinical samples were collected from patients with psoriasis and the expression of serine biosynthesis enzymes was evaluated. The HaCaT human keratinocyte cell line was transfected with small interfering RNA (siRNA) of key enzyme or treated with inhibitors. RNA sequencing and DNA methylation assays were performed to elucidate the mechanisms underlying serine metabolism-regulated psoriatic keratinocyte inflammation. An imiquimod (IMQ)-induced psoriasis mouse model was established to determine the effect of the SAM administration on psoriatic skin inflammation.

RESULTS

The expression of serine synthesis pathway enzymes, including the first rate-limiting enzyme in serine biosynthesis, phosphoglycerate dehydrogenase (PHGDH), was downregulated in the epidermal lesions of patients with psoriasis compared with that in healthy controls. Suppressing PHGDH in keratinocytes promoted the production of proinflammatory cytokines and enrichment of psoriatic-related signalling pathways, including the tumour necrosis factor-alpha (TNF-α) signalling pathway, interleukin (IL)-17 signalling pathway and NF-κB signalling pathway. In particular, PHGDH inhibition markedly promoted the secretion of IL-6 in keratinocytes with or without IL-17A, IL-22, IL-1α, oncostatin M and TNF-α (mix) stimulation. Mechanistically, PHGDH inhibition upregulated the expression of IL-6 by inhibiting SAM-dependent DNA methylation at the promoter and increasing the binding of myocyte enhancer factor 2A. Furthermore, PHGDH inhibition increased the secretion of IL-6 by increasing the activation of NF-κB via SAM inhibition. SAM treatment effectively alleviated IMQ-induced psoriasis-like skin inflammation in mice.

CONCLUSIONS

Our study revealed the crucial role of PHGDH in antagonising psoriatic skin inflammation and indicated that targeting serine metabolism may represent a novel therapeutic strategy for treating psoriasis.

A New Landscape of Human Dental Aging: Causes, Consequences, and Intervention Avenues

Aging is accompanied by physical dysfunction and physiologic degeneration that occurs over an individual's lifetime. Human teeth, like many other organs, inevitably undergo chronological aging and age-related changes throughout the lifespan, resulting in a substantial need for preventive, restorative as well as periodontal dental care. This is particularly the case for seniors at 65 years of age and those older but economically disadvantaged. Dental aging not only interferes with normal chewing and digestion, but also affects daily appearance and interpersonal communications. Further dental aging can incur the case of multiple disorders such as oral cancer, encephalitis, and other systemic diseases. In the next decades or even hundreds of years, the proportion of the elderly in the global population will continue to rise, a tendency that attracts increasing attention across multiple scientific and medical disciplines. Dental aging will bring a variety of problems to the elderly themselves and poses serious challenges to the medical profession and social system. A reduced, but functional dentition comprising 20 teeth in occlusion has been proposed as a measurement index of successful dental aging. Healthy dental aging is critical to healthy aging, from both medical and social perspectives. To date, biomedical research on the causes, processes and regulatory mechanisms of dental aging is still in its infancy. In this article, updated insights into typical manifestations, associated pathologies, preventive strategies and molecular changes of dental aging are provided, with future research directions largely projected.

Metabolic Profiles of Cancer Stem Cells and Normal Stem Cells and Their Therapeutic Significance

Cancer stem cells (CSCs) are a rare cancer cell population, responsible for the facilitation, progression, and resistance of tumors to therapeutic interventions. This subset of cancer cells with stemness and tumorigenic properties is organized in niches within the tumor microenvironment (TME) and presents altered regulation in a variety of metabolic pathways, including glycolysis, oxidative phosphorylation (OXPHOS), as well as lipid, amino acid, and iron metabolism. CSCs exhibit similarities as well as differences when comparedto normal stem cells, but also possess the ability of metabolic plasticity. In this review, we summarize the metabolic characteristics of normal, non-cancerous stem cells and CSCs. We also highlight the significance and implications of interventions targeting CSC metabolism to potentially achieve more robust clinical responses in the future.

Roles of DNA methylation in influencing the functions of dental-derived mesenchymal stem cells

OBJECTIVE

DNA methylation as intensively studied epigenetic regulatory mechanism exerts pleiotropic effects on dental-derived mesenchymal stem cells (DMSCs). DMSCs have self-renewal and multidifferentiation potential. Here, this review aims at summarizing the research status about application of DMSCs in tissue engineering and clarifying the roles of DNA methylation in influencing the functions of DMSCs, with expectation of paving the way for its in-depth exploration in tissue engineering.

METHOD

The current research status about influence of DNA methylation in DMSCs was acquired by MEDLINE (through PubMed) and Web of Science using the keywords 'DNA methylation', 'dental-derived mesenchymal stem cells', 'dental pulp stem cells', 'periodontal ligament stem cells', 'dental follicle stem cells', 'stem cells from the apical papilla', 'stem cells from human exfoliated deciduous teeth', and 'gingival-derived mesenchymal stem cells'.

RESULTS

This review indicates DNA methylation affects DMSCs' differentiation and function through inhibiting or enhancing the expression of specific gene resulted by DNA methylation-related genes or relevant inhibitors.

CONCLUSION

DNA methylation can influence DMSCs in aspects of osteogenesis, adipogenesis, immunomodulatory function, and so on. Yet, the present studies about DNA methylation in DMSCs commonly focus on dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs). Little has been reported for other DMSCs.

Chronological and Replicative Aging of CD51+/PDGFR-α+ Pulp Stromal Cells

As a crucial source of mesenchymal stromal cells, CD51⁺/PDGFR-α⁺ human dental pulp stromal cells (hDPSCs) are promising seeding cells for regenerative medicine. Cellular senescence hinders the translational application of hDPSCs. However, it remains unclear whether chronological and replicative senescence results in distinct outcomes for hDPSCs. To investigate the influence of senescence on DPSCs, we used transgenic lineage tracking, immunofluorescence, flow cytometry, and various molecular experiments to depict the dynamic pattern of hDPSCs in mice and humans during chronological and replicative senescence. The data demonstrated that CD51⁺/PDGFR-α⁺ cells were decreased in chronological senescence. Impaired self-renewal and higher ossificatory differentiation were observed in chronologically senescent hDPSCs. Regarding replicative senescence, a decreased CD51⁺ but upregulated PDGFR-α⁺ population was observed in culture. Furthermore, weakened self-renewal and osteogenic differentiation were observed in replicatively senescent hDPSCs. In summary, CD51⁺/PDGFR-α⁺ hDPSCs decrease in chronologically aged pulp, with self-renewal that is impaired without impaired osteogenic differentiation. However, replicative senescence has a different impact: self-renewal and ossific differentiation are impaired and CD51 expression is reduced, but PDGFR-α expression remains. These findings demonstrate the different outcomes of chronological and replicative senescence in CD51⁺/PDGFR-α⁺ hDPSCs. Furthermore, we revealed that impaired self-renewal is the core dysfunction for both types of cellular aging and that osteogenic differentiation capability differs between them. This study provides insights into the influence of chronological and replicative senescence on the characteristics and capabilities of hDPSCs. These advances provide fundamental knowledge to alleviate cellular aging of CD51⁺/PDGFR-α⁺ hDPSCs and promote their translational applications.

PSAT1 positively regulates the osteogenic lineage differentiation of periodontal ligament stem cells through the ATF4/PSAT1/Akt/GSK3β/β-catenin axis

BACKGROUND

Periodontal ligament stem cells (PDLSCs) are important seed cells for tissue engineering to realize the regeneration of alveolar bone. Understanding the gene regulatory mechanisms of osteogenic lineage differentiation in PDLSCs will facilitate PDLSC-based bone regeneration. However, these regulatory molecular signals have not been clarified.

METHODS

To screen potential regulators of osteogenic differentiation, the gene expression profiles of undifferentiated and osteodifferentiated PDLSCs were compared by microarray and bioinformatics methods, and PSAT1 was speculated to be involved in the gene regulation network of osteogenesis in PDLSCs. Lentiviral vectors were used to overexpress or knock down PSAT1 in PDLSCs, and then the proliferation activity, migration ability, and osteogenic differentiation ability of PDLSCs in vitro were analysed. A rat mandibular defect model was built to analyse the regulatory effects of PSAT1 on PDLSC-mediated bone regeneration in vivo. The regulation of PSAT1 on the Akt/GSK3β/β-catenin signalling axis was analysed using the Akt phosphorylation inhibitor Ly294002 or agonist SC79. The potential sites on the promoter of PSAT1 that could bind to the transcription factor ATF4 were predicted and verified.

RESULTS

The microarray assay showed that the expression levels of 499 genes in PDLSCs were altered significantly after osteogenic induction. Among these genes, the transcription level of PSAT1 in osteodifferentiated PDLSCs was much lower than that in undifferentiated PDLSCs. Overexpressing PSAT1 not only enhanced the proliferation and osteogenic differentiation abilities of PDLSCs in vitro, but also promoted PDLSC-based alveolar bone regeneration in vivo, while knocking down PSAT1 had the opposite effects in PDLSCs. Mechanistic experiments suggested that PSAT1 regulated the osteogenic lineage fate of PDLSCs through the Akt/GSK3β/β-catenin signalling axis. PSAT1 expression in PDLSCs during osteogenic differentiation was controlled by transcription factor ATF4, which is realized by the combination of ATF4 and the PSAT1 promoter.

CONCLUSION

PSAT1 is a potential important regulator of the osteogenic lineage differentiation of PDLSCs through the ATF4/PSAT1/Akt/GSK3β/β-catenin signalling pathway. PSAT1 could be a candidate gene modification target for enhancing PDLSCs-based bone regeneration.

Epigenetic regulation of dental-derived stem cells and their application in pulp and periodontal regeneration

Dental-derived stem cells have excellent proliferation ability and multi-directional differentiation potential, making them an important research target in tissue engineering. An increasing number of dental-derived stem cells have been discovered recently, including dental pulp stem cells (DPSCs), stem cells from exfoliated deciduous teeth (SHEDs), stem cells from apical papilla (SCAPs), dental follicle precursor cells (DFPCs), and periodontal ligament stem cells (PDLSCs). These stem cells have significant application prospects in tissue regeneration because they are found in an abundance of sources, and they have good biocompatibility and are highly effective. The biological functions of dental-derived stem cells are regulated in many ways. Epigenetic regulation means changing the expression level and function of a gene without changing its sequence. Epigenetic regulation is involved in many biological processes, such as embryonic development, bone homeostasis, and the fate of stem cells. Existing studies have shown that dental-derived stem cells are also regulated by epigenetic modifications. Pulp and periodontal regeneration refers to the practice of replacing damaged pulp and periodontal tissue and restoring the tissue structure and function under normal physiological conditions. This treatment has better therapeutic effects than traditional treatments. This article reviews the recent research on the mechanism of epigenetic regulation of dental-derived stem cells, and the core issues surrounding the practical application and future use of pulp and periodontal regeneration.

Epigenetic control of mesenchymal stem cells orchestrates bone regeneration

Recent studies have revealed the vital role of MSCs in bone regeneration. In both self-healing bone regeneration processes and biomaterial-induced healing of bone defects beyond the critical size, MSCs show several functions, including osteogenic differentiation and thus providing seed cells. However, adverse factors such as drug intake and body senescence can significantly affect the functions of MSCs in bone regeneration. Currently, several modalities have been developed to regulate MSCs' phenotype and promote the bone regeneration process. Epigenetic regulation has received much attention because of its heritable nature. Indeed, epigenetic regulation of MSCs is involved in the pathogenesis of a variety of disorders of bone metabolism. Moreover, studies using epigenetic regulation to treat diseases are also being reported. At the same time, the effects of epigenetic regulation on MSCs are yet to be fully understood. This review focuses on recent advances in the effects of epigenetic regulation on osteogenic differentiation, proliferation, and cellular senescence in MSCs. We intend to illustrate how epigenetic regulation of MSCs orchestrates the process of bone regeneration.

Association of Early Childhood Caries with Bitter Taste Receptors: A Meta-Analysis of Genome-Wide Association Studies and Transcriptome-Wide Association Study

Although genetics affects early childhood caries (ECC) risk, few studies have focused on finding its specific genetic determinants. Here, we performed genome-wide association studies (GWAS) in five cohorts of children (aged up to 5 years, total N = 2974, cohorts: Center for Oral Health Research in Appalachia cohorts one and two [COHRA1, COHRA2], Iowa Fluoride Study, Iowa Head Start, Avon Longitudinal Study of Parents and Children [ALSPAC]) aiming to identify genes with potential roles in ECC biology. We meta-analyzed the GWASs testing ~3.9 million genetic variants and found suggestive evidence for association at genetic regions previously associated with caries in primary and permanent dentition, including the β-defensin anti-microbial proteins. We then integrated the meta-analysis results with gene expression data in a transcriptome-wide association study (TWAS). This approach identified four genes whose genetically predicted expression was associated with ECC (p-values < 3.09 × 10−6; CDH17, TAS2R43, SMIM10L1, TAS2R14). Some of the strongest associations were with genes encoding members of the bitter taste receptor family (TAS2R); other members of this family have previously been associated with caries. Of note, we identified the receptor encoded by TAS2R14, which stimulates innate immunity and anti-microbial defense in response to molecules released by the cariogenic bacteria, Streptococcus mutans and Staphylococcus aureus. These findings provide insight into ECC genetic architecture, underscore the importance of host-microbial interaction in caries risk, and identify novel risk genes.

Effect of Biodentine on Odonto/Osteogenic Differentiation of Human Dental Pulp Stem Cells

This study aims to compare the biological characteristics of human dental pulp stem cells (hDPSCs) isolated from different-aged populations and examine the effects of Biodentine on proliferation and odonto/osteogenic differentiation of hDPSCs isolated from the elderly in vitro. hDPSCs were isolated from three different-aged populations: group A (≤18 years old), group B (19−59 years old), and group C (≥60 years old). The adhesion, proliferation, odonto/osteogenesis, and senescence were compared. The optimal concentration of aqueous Biodentine extract was determined by CCK-8 assay, alkaline phosphatase (ALP), and alizarin red staining (ARS). The effect of Biodentine on odonto/osteogenic gene and protein expression of hDPSCs in each group was evaluated by quantitative real-time PCR (QRT-PCR) and Western blot. hDPSCs were successfully isolated from three different-aged populations. Flow cytometry revealed that all isolated hDPSCs were positive for CD73 (>90%), CD90 (>90%), CD146 (<30%), and negative for CD45 (<1%). There existed an age-related decline in proliferation, odonto/osteogenic gene expression, and S-phase fraction (p < 0.05), an increase in senescence genes and p21 and p16 expression, and time needed for cell adhesion. Biodentine promoted hDPSC proliferation and mineralization in each group, particularly at a concentration of 0.2 mg/mL. Biodentine markedly enhanced odonto/osteogenesis-related gene and protein expression in each group (p < 0.05). hDPSCs can be obtained from populations of all ages. Though there is an age-related decline in their biological properties, hDPSCs from the elderly still maintain certain proliferation and multidirectional differentiation abilities. Biodentine can significantly promote the proliferation and odonto/osteogenic differentiation of hDPSCs isolated from the elderly over 60 years old, which could be considered a pulp capping material for vital pulp therapy in the elderly. Nevertheless, the efficacy of Biodentine in clinical application has to be further studied.

Biological characteristics and pulp regeneration potential of stem cells from canine deciduous teeth compared with those of permanent teeth

BACKGROUND

Clinical studies have demonstrated that dental pulp stem cells isolated from permanent teeth (PT-DPSCs) are safe and efficacious for complete pulp regeneration in mature pulpectomized permanent teeth with complete apical closure. Moreover, dental pulp stem cells from deciduous teeth (DT-DPSCs) have also been shown to be useful for pulp regenerative cell therapy of injured immature permanent teeth. However, direct comparisons of the pulp regenerative potential of DT-DPSCs and PT-DPSCs from the same individual have not been performed. This study aimed to compare the differences in stem cell properties and pulp regenerative potential of DT-DPSCs and PT-DPSCs of identical origin.

METHODS

DT-DPSCs and PT-DPSCs were isolated from the same individual dogs at 4 months and 9 months of age, respectively. The expression of cell surface antigen markers, proliferation and migration activities, and gene expression of stem cell markers, angiogenic/neurotrophic factors and senescence markers were compared. The effects of conditioned medium (CM) derived from these cells on cellular proliferation, migration, angiogenesis, neurite outgrowth and immunosuppression were also compared. Autologous transplantation of DT-DPSCs or PT-DPSCs together with G-CSF was performed to treat pulpectomized teeth in individual dogs. The vascularization and reinnervation of the regenerated pulp tissues were qualitatively and quantitatively compared between groups by histomorphometric analyses.

RESULTS

The rates of positive CXCR4 and G-CSFR expression in DT-DPSCs were significantly higher than those in PT-DPSCs. DT-DPSCs migrated at a higher rate with/without G-CSF and exhibited increased expression of the stem cell markers Oct3/4 and CXCR4 and the angiogenic factor VEGF and decreased expression of the senescence marker p16 than PT-DPSCs. DT-DPSC-derived CM promoted increased cell proliferation, migration with G-CSF, and angiogenesis compared with PT-DPSC-derived CM; however, no difference was observed in neurite outgrowth or immunosuppression. The regenerated pulp tissues in the pulpectomized teeth were quantitatively and qualitatively similar between the DT-DPSCs and PT-DPSCs transplant groups.

CONCLUSIONS

These results demonstrated that DT-DPSCs could be a potential clinical alternative to PT-DPSCs for pulp regenerative therapy. DT-DPSCs can be preserved in an individual cell bank and used for potential future pulp regenerative therapy before the supply of an individual's own sound discarded teeth has been exhausted.

DNA Methylation and Histone Modification in Dental-derived Mesenchymal Stem Cells

Epigenetic regulation, mainly involving DNA methylation, histone modification, and noncoding RNAs (ncRNAs), is essential for the regulation of multiple cellular processes. Dental-derived mesenchymal stem cells (DMSCs), a kind of multipotent cells derived from dental tissues, are impactful in regenerative medicine. Recent studies have shown that epigenetic regulation plays a major role in DMSCs. Therefore, exploring how epigenetic regulation is involved in DMSCs may be of guiding significance for tissue repair and regeneration or for exploring more effective treatments. A number of research of ncRNAs in DMSCs have been reported. However, little is known about the roles of DNA methylation and histone modifications in DMSCs. In this review, we summarize the important roles of DNA methylation and histone modifications of the fate of DMSCs.

Human gingival mesenchymal stem cells retain their growth and immunomodulatory characteristics independent of donor age

Aging has been reported to deteriorate the quantity and quality of mesenchymal stem cells (MSCs), which affect their therapeutic use in regenerative medicine. A dearth of age-related stem cell research further restricts their clinical applications. The present study explores the possibility of using MSCs derived from human gingival tissues (GMSCs) for studying their ex vivo growth characteristics and differentiation potential with respect to donor age. GMSCs displayed decreased in vitro adipogenesis and in vitro and in vivo osteogenesis with age, but in vitro neurogenesis remained unaffected. An increased expression of p53 and SIRT1 with donor age was correlated to their ability of eliminating tumorigenic events through apoptosis or autophagy, respectively. Irrespective of donor age, GMSCs displayed effective immunoregulation and regenerative potential in a mouse model of LPS-induced acute lung injury. Thus, we suggest the potential of GMSCs for designing cell-based immunomodulatory therapeutic approaches and their further extrapolation for acute inflammatory conditions such as acute respiratory distress syndrome and COVID-19.

Metabolic Remodeling Impacts the Epigenetic Landscape of Dental Mesenchymal Stem Cells

Epigenetic regulation can dynamically adjust the gene expression program of cell fate decision according to the cellular microenvironment. Emerging studies have shown that metabolic activities provide fundamental components for epigenetic modifications and these metabolic-sensitive epigenetic events dramatically impact the cellular function of stem cells. Dental mesenchymal stem cells are promising adult stem cell resource for in situ injury repair and tissue engineering. In this review, we discuss the impact of metabolic fluctuations on epigenetic modifications in the oral and maxillofacial regions. The principles of the metabolic link to epigenetic modifications and the interaction between metabolite substrates and canonical epigenetic events in dental mesenchymal stem cells are summarized. The coordination between metabolic pathways and epigenetic events plays an important role in cellular progresses including differentiation, inflammatory responses, and aging. The metabolic-epigenetic network is critical for expanding our current understanding of tissue homeostasis and cell fate decision and for guiding potential therapeutic approaches in dental regeneration and infectious diseases.

Oral Senescence: From Molecular Biology to Clinical Research

Cellular senescence is an irreversible cell cycle arrest occurring following multiple rounds of cell division (replicative senescence) or in response to cellular stresses such as ionizing radiation, signaling imbalances and oxidative damage (stress-induced premature senescence). Even very small numbers of senescent cells can be deleterious and there is evidence that senescent cells are instrumental in a number of oral pathologies including cancer, oral sub mucous fibrosis and the side effects of cancer therapy. In addition, senescent cells are present and possibly important in periodontal disease and other chronic inflammatory conditions of the oral cavity. However, senescence is a double-edged sword because although it operates as a suppressor of malignancy in pre-malignant epithelia, senescent cells in the neoplastic environment promote tumor growth and progression. Many of the effects of senescent cells are dependent on the secretion of an array of diverse therapeutically targetable proteins known as the senescence-associated secretory phenotype. However, as senescence may have beneficial roles in wound repair, preventing fibrosis and stem cell activation the clinical exploitation of senescent cells is not straightforward. Here, we discuss biological mechanisms of senescence and we review the current approaches to target senescent cells therapeutically, including senostatics and senolytics which are entering clinical trials.