P16INK4A—More Than a Senescence Marker

Alpha-6 integrin deletion delays the formation of Brca1/p53-deficient basal-like breast tumors by restricting luminal progenitor cell expansion

BACKGROUND

The aberrant amplification of mammary luminal progenitors is at the origin of basal-like breast cancers associated with BRCA1 mutations. Integrins mediate cell-matrix adhesion and transmit mechanical and chemical signals that drive epithelial stem cell functions and regulate tumor progression, metastatic reactivation, and resistance to targeted therapies. Consistently, we have recently shown that laminin-binding integrins are essential for the expansion and differentiation of mammary luminal progenitors in physiological conditions. As over-expression of the laminin-binding α6 integrin (Itgα6) is associated with poor prognosis and reduced survival in breast cancer, we here investigate the role of Itgα6 in mammary tumorigenesis.

METHODS

We used Blg-Cre; Brca1F/F; Trp53F/F mice, a model that phenocopies human basal-like breast cancer with BRCA1 mutations. We generated mutant mice proficient or deficient in Itgα6 expression and followed tumor formation. Mammary tumors and pretumoral tissues were characterized by immunohistochemistry, flow cytometry, RT-qPCR, Western blotting and organoid cultures. Clonogenicity of luminal progenitors from preneoplastic glands was studied in 3D Matrigel cultures.

RESULTS

We show that Itga6 deletion favors activation of p16 cell cycle inhibitor in the preneoplastic tissue. Subsequently, the amplification of luminal progenitors, the cell of origin of Brca1-deficient tumors, is restrained in Itgα6-deficient gland. In addition, the partial EMT program operating in Brca1/p53-deficient epithelium is attenuated in the absence of Itgα6. As a consequence of these events, mammary tumor formation is delayed in Itgα6-deficient mice. After tumor formation, the lack of Itgα6 does not affect tumor growth but rather alters their differentiation, resulting in reduced expression of basal cell markers.

CONCLUSIONS

Our data indicate that Itgα6 has a pro-tumorigenic role in Blg-Cre; Brca1F/F; Trp53F/F mice developing basal-like mammary tumors. In particular, we reveal that Itgα6 is required for the luminal progenitor expansion and the aberrant partial EMT program that precedes the formation of BRCA1 deficient tumors.

Suppression of autophagy induces senescence in the heart

Aging is a critical risk factor for heart disease, including ischemic heart disease and heart failure. Cellular senescence, characterized by DNA damage, resistance to apoptosis and the senescence-associated secretory phenotype (SASP), occurs in many cell types, including cardiomyocytes. Senescence precipitates the aging process in surrounding cells and the organ through paracrine mechanisms. Generalized autophagy, which degrades cytosolic materials in a non-selective manner, is decreased during aging in the heart. This decrease causes deterioration of cellular quality control mechanisms, facilitates aging and negatively affects lifespan in animals, including mice. Although suppression of generalized autophagy could promote senescence, it remains unclear whether the suppression of autophagy directly stimulates senescence in cardiomyocytes, which, in turn, promotes myocardial dysfunction in the heart. We addressed this question using mouse models with a loss of autophagy function. Suppression of general autophagy in cardiac-specific Atg7 knockout ( Atg7 cKO) mice caused accumulation of senescent cardiomyocytes. Induction of senescence via downregulation of Atg7 was also observed in chimeric Atg7 cardiac-specific KO mice and cultured cardiomyocytes in vitro , suggesting that the effect of autophagy suppression upon induction of senescence is cell autonomous. ABT-263, a senolytic agent, reduced the number of senescent myocytes and improved cardiac function in Atg7 cKO mice. Suppression of autophagy and induction of senescence were also observed in doxorubicin-treated hearts, where activation of autophagy alleviated senescence in cardiomyocytes and cardiac dysfunction. These results suggest that suppression of general autophagy directly induces senescence in cardiomyocytes, which in turn promotes cardiac dysfunction.

Replication stress as a driver of cellular senescence and aging

Replication stress refers to slowing or stalling of replication fork progression during DNA synthesis that disrupts faithful copying of the genome. While long considered a nexus for DNA damage, the role of replication stress in aging is under-appreciated. The consequential role of replication stress in promotion of organismal aging phenotypes is evidenced by an extensive list of hereditary accelerated aging disorders marked by molecular defects in factors that promote replication fork progression and operate uniquely in the replication stress response. Additionally, recent studies have revealed cellular pathways and phenotypes elicited by replication stress that align with designated hallmarks of aging. Here we review recent advances demonstrating the role of replication stress as an ultimate driver of cellular senescence and aging. We discuss clinical implications of the intriguing links between cellular senescence and aging including application of senotherapeutic approaches in the context of replication stress.

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

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

The NDR family of kinases: essential regulators of aging

Aging is defined as a progressive decline of cognitive and physiological functions over lifetime. Since the definition of the nine hallmarks of aging in 2013 by López-Otin, numerous studies have attempted to identify the main regulators and contributors in the aging process. One interesting group of proteins whose participation has been implicated in several aging hallmarks are the nuclear DBF2-related (NDR) family of serine-threonine AGC kinases. They are one of the core components of the Hippo signaling pathway and include NDR1, NDR2, LATS1 and LATS2 in mammals, along with its highly conserved metazoan orthologs; Trc in Drosophila melanogaster, SAX-1 in Caenorhabditis elegans, CBK1, DBF20 in Saccharomyces cerevisiae and orb6 in Saccharomyces pombe. These kinases have been independently linked to the regulation of widely diverse cellular processes disrupted during aging such as the cell cycle progression, transcription, intercellular communication, nutrient homeostasis, autophagy, apoptosis, and stem cell differentiation. However, a comprehensive overview of the state-of-the-art knowledge regarding the post-translational modifications of and by NDR kinases in aging has not been conducted. In this review, we summarize the current understanding of the NDR family of kinases, focusing on their relevance to various aging hallmarks, and emphasize the growing body of evidence that suggests NDR kinases are essential regulators of aging across species.

Homocysteine-potentiated Kelch-like ECH-associated protein 1 promotes senescence of neuroblastoma 2a cells via inhibiting ubiquitination of β-catenin

Elevated serum homocysteine (Hcy) level is a risk factor for Alzheimer's disease (AD) and accelerates cell aging. However, the mechanism by which Hcy induces neuronal senescence remains largely unknown. In this study, we observed that Hcy significantly promoted senescence in neuroblastoma 2a (N2a) cells with elevated β-catenin and Kelch-like ECH-associated protein 1 (KEAP1) levels. Intriguingly, Hcy promoted the interaction between KEAP1 and the Wilms tumor gene on the X chromosome (WTX) while hampering the β-catenin-WTX interaction. Mechanistically, Hcy attenuated the methylation level of the KEAP1 promoter CpG island and activated KEAP1 transcription. However, a slow degradation rate rather than transcriptional activation contributed to the high level of β-catenin. Hcy-upregulated KEAP1 competed with β-catenin to bind to WTX. Knockdown of both β-catenin and KEAP1 attenuated Hcy-induced senescence in N2a cells. Our data highlight a crucial role of the KEAP1-β-catenin pathway in Hcy-induced neuronal-like senescence and uncover a promising target for AD treatment.

A comparative in vitro study on the effect of SGLT2 inhibitors on chemosensitivity to doxorubicin in MCF-7 breast cancer cells

Cancer frequently develops resistance to the majority of chemotherapy treatments. This study aimed to examine the synergistic cytotoxic and antitumor effects of SGLT2 inhibitors, specifically Canagliflozin (CAN), Dapagliflozin (DAP), Empagliflozin (EMP), and Doxorubicin (DOX), using in vitro experimentation. The precise combination of CAN+DOX has been found to greatly enhance the cytotoxic effects of doxorubicin (DOX) in MCF-7 cells. Interestingly, it was shown that cancer cells exhibit an increased demand for glucose and ATP in order to support their growth. Notably, when these medications were combined with DOX, there was a considerable inhibition of glucose consumption, as well as reductions in intracellular ATP and lactate levels. Moreover, this effect was found to be dependent on the dosages of the drugs. In addition to effectively inhibiting the cell cycle, the combination of CAN+DOX induces substantial modifications in both cell cycle and apoptotic gene expression. This work represents the initial report on the beneficial impact of SGLT2 inhibitor medications, namely CAN, DAP, and EMP, on the responsiveness to the anticancer properties of DOX. The underlying molecular mechanisms potentially involve the suppression of the function of SGLT2.

Accelerated Aging in Cancer Survivors: Cellular Senescence, Frailty, and Possible Opportunities for Interventions

The population of cancer survivors has markedly increased due to the rapid improvements in cancer treatment. However, cancer survivors experience accelerated aging, which leads to chronic diseases and other age-related conditions, such as frailty. Those conditions may persist years after cancer diagnosis and treatment. Cellular senescence, a hallmark of aging, is one of the mechanisms that contribute to accelerated aging in cancer survivors. Several aging measures, including measures based on clinical markers and biomarkers, have been proposed to estimate the aging process, and some of them have shown associations with mortality and frailty in cancer survivors. Several anti-aging interventions, including lifestyle changes and anti-aging drugs, have been proposed. Future research, particularly in large-scale studies, is needed to determine the efficiency of these aging measures and anti-aging interventions before considering their application in clinics. This review focuses on the mechanisms of cellular senescence and accelerated aging in cancer survivors, assessment of the aging process using clinical markers and biomarkers, and the high prevalence of frailty in that population, as well as possible opportunities for anti-aging interventions. A deeper understanding of aging measures and anti-aging interventions in cancer survivors will contribute to the development of effective strategies to mitigate accelerated aging in cancer survivors and improve their quality of life.

Ergothioneine promotes longevity and healthy aging in male mice

Healthy aging has emerged as a crucial issue with the increase in the geriatric population worldwide. Food-derived sulfur-containing amino acid ergothioneine (ERGO) is a potential dietary supplement, which exhibits various beneficial effects in experimental animals although the preventive effects of ERGO on aging and/or age-related impairments such as frailty and cognitive impairment are unclear. We investigated the effects of daily oral supplementation of ERGO dissolved in drinking water on lifespan, frailty, and cognitive impairment in male mice from 7 weeks of age to the end of their lives. Ingestion of 4 ~ 5 mg/kg/day of ERGO remarkably extended the lifespan of male mice. The longevity effect of ERGO was further supported by increase in life and non-frailty spans of Caenorhabditis elegans in the presence of ERGO. Compared with the control group, the ERGO group showed significantly lower age-related declines in weight, fat mass, and average and maximum movement velocities at 88 weeks of age. This was compatible with dramatical suppression by ERGO of the age-related increments in plasma biomarkers (BMs) such as the chemokine ligand 9, creatinine, symmetric dimethylarginine, urea, asymmetric dimethylarginine, quinolinic acid, and kynurenine. The oral intake of ERGO also rescued age-related impairments in learning and memory ability, which might be associated with suppression of the age-related decline in hippocampal neurogenesis and TDP43 protein aggregation and promotion of microglial shift to the M2 phenotype by ERGO ingestion. Ingestion of ERGO may promote longevity and healthy aging in male mice, possibly through multiple biological mechanisms.

PR55α-controlled protein phosphatase 2A inhibits p16 expression and blocks cellular senescence induction by γ-irradiation

Cellular senescence is a permanent cell cycle arrest that can be triggered by both internal and external genotoxic stressors, such as telomere dysfunction and DNA damage. The execution of senescence is mainly by two pathways, p16/RB and p53/p21, which lead to CDK4/6 inhibition and RB activation to block cell cycle progression. While the regulation of p53/p21 signaling in response to DNA damage and other insults is well-defined, the regulation of the p16/RB pathway in response to various stressors remains poorly understood. Here, we report a novel function of PR55α, a regulatory subunit of PP2A Ser/Thr phosphatase, as a potent inhibitor of p16 expression and senescence induction by ionizing radiation (IR), such as γ-rays. The results show that ectopic PR55α expression in normal pancreatic cells inhibits p16 transcription, increases RB phosphorylation, and blocks IR-induced senescence. Conversely, PR55α-knockdown by shRNA in pancreatic cancer cells elevates p16 transcription, reduces RB phosphorylation, and triggers senescence induction after IR. Furthermore, this PR55α function in the regulation of p16 and senescence is p53-independent because it was unaffected by the mutational status of p53. Moreover, PR55α only affects p16 expression but not p14 (ARF) expression, which is also transcribed from the same CDKN2A locus but from an alternative promoter. In normal human tissues, levels of p16 and PR55α proteins were inversely correlated and mutually exclusive. Collectively, these results describe a novel function of PR55α/PP2A in blocking p16/RB signaling and IR-induced cellular senescence.

Senotherapeutics to Counteract Senescent Cells Are Prominent Topics in the Context of Anti-Ageing Strategies

Cellular senescence is implicated in ageing and associated with a broad spectrum of age-related diseases. Importantly, a cell can initiate the senescence program irrespective of the organism's age. Various stress signals, including those defined as ageing hallmarks and alterations leading to cancer development, oncogene activation, or loss of cancer-suppressive functions, can trigger cellular senescence. The primary outcome of these alterations is the activation of nuclear factor (NF)-κB, thereby inducing the senescence-associated secretory phenotype (SASP). Proinflammatory cytokines and chemokines, components of this phenotype, contribute to chronic systemic sterile inflammation, commonly referred to as inflamm-ageing. This inflammation is linked to age-related diseases (ARDs), frailty, and increased mortality in older individuals. Additionally, senescent cells (SCs) accumulate in multiple tissues with age and are believed to underlie the organism functional decline, as demonstrated by models. An escalating effort has been dedicated to identify senotherapeutics that selectively target SCs by inducing apoptosis; these drugs are termed senolytics. Concurrently, small molecules that suppress senescent phenotypes without causing cell death are known as senomorphics. Both natural and synthetic senotherapeutics, along with immunotherapies employing immune cell-mediated clearance of SCs, currently represent the most promising strategies to combat ageing and ARDs. Indeed, it is fascinating to observe that information regarding the immune reaction to SCs indicates that regulation by specific lymphocyte subsets, elevated in the oldest centenarians, plays a role in attaining extreme longevity. Regardless, the application of methods already utilized in cancer treatment, such as CAR cells and monoclonal antibodies, broadens the spectrum of potential approaches to be utilized.

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.

In Vitro Osteogenesis Study of Shell Nacre Cement with Older and Young Donor Bone Marrow Mesenchymal Stem/Stromal Cells

Bone void-filling cements are one of the preferred materials for managing irregular bone voids, particularly in the geriatric population who undergo many orthopedic surgeries. However, bone marrow mesenchymal stem/stromal cells (BM-MSCs) of older-age donors often exhibit reduced osteogenic capacity. Hence, it is crucial to evaluate candidate bone substitute materials with BM-MSCs from the geriatric population to determine the true osteogenic potential, thus simulating the clinical situation. With this concept, we investigated the osteogenic potential of shell nacre cement (SNC), a bone void-filling cement based on shell nacre powder and ladder-structured siloxane methacrylate, using older donor BM-MSCs (age > 55 years) and young donor BM-MSCs (age < 30 years). Direct and indirect cytotoxicity studies conducted with human BM-MSCs confirmed the non-cytotoxic nature of SNC. The standard colony-forming unit-fibroblast (CFU-F) assay and population doubling (PD) time assays revealed a significant reduction in the proliferation potential (p < 0.0001, p < 0.05) in older donor BM-MSCs compared to young donor BM-MSCs. Correspondingly, older donor BM-MSCs contained higher proportions of senescent, β-galactosidase (SA-β gal)-positive cells (nearly 2-fold, p < 0.001). In contrast, the proliferation capacity of older donor BM-MSCs, measured as the area density of CellTrackerTM green positive cells, was similar to that of young donor BM-MSCs following a 7-day culture on SNC. Furthermore, after 14 days of osteoinduction on SNC, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS) showed that the amount of calcium and phosphorus deposited by young and older donor BM-MSCs on SNC was comparable. A similar trend was observed in the expression of the osteogenesis-related genes BMP2, RUNX2, ALP, COL1A1, OMD and SPARC. Overall, the results of this study indicated that SNC would be a promising candidate for managing bone voids in all age groups.

p16 Expression in Laryngeal Squamous Cell Carcinoma: A Surrogate or Independent Prognostic Marker?

Laryngeal squamous cell carcinoma (LSCC) is a common malignancy that, despite scientific advancements, has not seen an improvement in its prognosis in the last decades. Few promising predictive markers have been found and none are relevant in clinical practice. p16ink4a, an oncosuppressor protein involved in cell cycle arrest, with a prognostic impact on other cancers, has been widely used in the head and neck region as a surrogate marker of HPV infection. Published papers and recent meta-analyses seem to minimize the biological role of HPV in the context of LSCC's cancerogenesis, and to disprove the reliability of p16ink4a as a surrogate prognostic marker in this context, while still highlighting its potential role as an independent predictor of survival. Unfortunately, the available literature, in particular during the last two decades, is often not focused on its potential role as an independent biomarker and few relevant data are found in papers mainly focused on HPV. The available data suggest that future research should focus specifically on p16ink4a, taking into account both its potential inactivation and overexpression, different patterns of staining, and immunohistochemistry cutoffs, and should focus not on its potential role as a surrogate marker but on its independent role as a predictor of survival.

Diverse Response to Local Pharmacological Blockade of Sirt1 Cleavage in Age-Induced versus Trauma-Induced Osteoarthritis Female Mice

Objective: Previous studies have shown that the cleavage of Sirt1 contributes to the development of osteoarthritis (OA). In fact, OA was effectively abrogated by the intra-articular (IA) administration of two compounds, one blocking Sirt1 cleavage (CA074me) and the other activating Sirt1 (SRT1720), using a post-traumatically induced model (PTOA) in young female mice. In this study, we attempted to understand if this local treatment is effective in preventing age-associated OA (AOA) progression and symptoms. Design: A group of 17-month-old female C57BL/6J mice were IA administered with CA074me and/or SRT1720 or their combination. Joint histopathological analysis and bone histomorphometry were carried out, with an assessment of knee mechanical hyperalgesia. A serum analysis for NT/CT Sirt1 was carried out along with immunohistochemistry for articular cartilage to detect p16INK4A or γH2A.X. Similarly, meniscal cartilage was monitored for Lef1 and Col1a1 deposition. The data were compared for young female mice subjected to post-traumatic OA (PTOA). Results: Similar to PTOA, combination-treated AOA exhibited improved knee hyperalgesia, yet structural improvements were undetected, corresponding to unchanged NT/CT Sirt1 serum levels. Both AOA and PTOA exhibited unchanged staining for nuclear p16INK4A or γH2A.X and lacked a correlation with OA severity. Contrarily to PTOA, the combination treatment with AOA did not exhibit a local reduction in the Lef1 and Col1 targets. Conclusions: When targeting Sirt1 cleavage, the PTOA and AOA models exhibited a similar pain response to the combination treatment; however, they displayed diverse structural outcomes for joint-related damage, related to Lef1-dependent signaling. Interestingly, nuclear p16INK4A was unaffected in both models, regardless of the treatment's effectiveness. Finally, these findings highlight the variations in the responses between two highly researched OA preclinical models, reflecting OA pathophysiology heterogeneity and variations in gender-related drug-response mechanisms.

Eternal Youth: A Comprehensive Exploration of Gene, Cellular, and Pharmacological Anti-Aging Strategies

The improvement of human living conditions has led to an increase in average life expectancy, creating a new social and medical problem-aging, which diminishes the overall quality of human life. The aging process of the body begins with the activation of effector signaling pathways of aging in cells, resulting in the loss of their normal functions and deleterious effects on the microenvironment. This, in turn, leads to chronic inflammation and similar transformations in neighboring cells. The cumulative retention of these senescent cells over a prolonged period results in the deterioration of tissues and organs, ultimately leading to a reduced quality of life and an elevated risk of mortality. Among the most promising methods for addressing aging and age-related illnesses are pharmacological, genetic, and cellular therapies. Elevating the activity of aging-suppressing genes, employing specific groups of native and genetically modified cells, and utilizing senolytic medications may offer the potential to delay aging and age-related ailments over the long term. This review explores strategies and advancements in the field of anti-aging therapies currently under investigation, with a particular emphasis on gene therapy involving adeno-associated vectors and cell-based therapeutic approaches.

Tat-heat shock protein 10 ameliorates age-related phenotypes by facilitating neuronal plasticity and reducing age-related genes in the hippocampus

We investigated the effects of heat shock protein 10 (HSP10) protein on memory function, hippocampal neurogenesis, and other related genes/proteins in adult and aged mice. To translocate the HSP10 protein into the hippocampus, the Tat-HSP10 fusion protein was synthesized, and Tat-HSP10, not HSP10, was successfully delivered into the hippocampus based on immunohistochemistry and western blotting. Tat-HSP10 (0.5 or 2.0 mg/kg) or HSP10 (control protein, 2.0 mg/kg) was administered daily to 3- and 21-month-old mice for 3 months, and observed the senescence maker P16 was significantly increased in aged mice and the treatment with Tat-HSP10 significantly decreased P16 expression in the hippocampus of aged mice. In novel object recognition and Morris water maze tests, aged mice demonstrated decreases in exploratory preferences, exploration time, distance moved, number of object contacts, and escape latency compared to adult mice. Treatment with Tat-HSP10 significantly improved exploratory preferences, the number of object contacts, and the time spent swimming in the target quadrant in aged mice but not adults. Administration of Tat-HSP10 increased the number of proliferating cells and differentiated neuroblasts in the dentate gyrus of adult and aged mice compared to controls, as determined by immunohistochemical staining for Ki67 and doublecortin, respectively. Additionally, Tat-HSP10 treatment significantly mitigated the reduction in sirtuin 1 mRNA level, N-methyl-D-aspartate receptor 1, and postsynaptic density 95 protein levels in the hippocampus of aged mice. In contrast, Tat-HSP10 treatment significantly increased sirtuin 3 protein levels in both adult and aged mouse hippocampus. These suggest that Tat-HSP10 can potentially reduce hippocampus-related aging phenotypes.

Melatonin Exerts Prominent, Differential Epidermal and Dermal Anti-Aging Properties in Aged Human Eyelid Skin Ex Vivo

Human skin aging is associated with functional deterioration on multiple levels of physiology, necessitating the development of effective skin senotherapeutics. The well-tolerated neurohormone melatonin unfolds anti-aging properties in vitro and in vivo, but it remains unclear whether these effects translate to aged human skin ex vivo. We tested this in organ-cultured, full-thickness human eyelid skin (5-6 donors; 49-77 years) by adding melatonin to the culture medium, followed by the assessment of core aging biomarkers via quantitative immunohistochemistry. Over 6 days, 200 µM melatonin significantly downregulated the intraepidermal activity of the aging-promoting mTORC1 pathway (as visualized by reduced S6 phosphorylation) and MMP-1 protein expression in the epidermis compared to vehicle-treated control skin. Conversely, the transmembrane collagen 17A1, a key stem cell niche matrix molecule that declines with aging, and mitochondrial markers (e.g., TFAM, MTCO-1, and VDAC/porin) were significantly upregulated. Interestingly, 100 µM melatonin also significantly increased the epidermal expression of VEGF-A protein, which is required and sufficient for inducing human skin rejuvenation. In aged human dermis, melatonin significantly increased fibrillin-1 protein expression and improved fibrillin structural organization, indicating an improved collagen and elastic fiber network. In contrast, other key aging biomarkers (SIRT-1, lamin-B1, p16INK4, collagen I) remained unchanged. This ex vivo study provides proof of principle that melatonin indeed exerts long-suspected but never conclusively demonstrated and surprisingly differential anti-aging effects in aged human epidermis and dermis.

In Vitro Models of Cell Senescence: A Systematic Review on Musculoskeletal Tissues and Cells

Ageing is an irreversible and inevitable biological process and a significant risk factor for the development of various diseases, also affecting the musculoskeletal system, resulting from the accumulation of cell senescence. The aim of this systematic review was to collect the in vitro studies conducted over the past decade in which cell senescence was induced through various methods, with the purpose of evaluating the molecular and cellular mechanisms underlying senescence and to identify treatments capable of delaying senescence. Through three electronic databases, 22 in vitro studies were identified and included in this systematic review. Disc, cartilage, or muscle cells or tissues and mesenchymal stem cells were employed to set-up in vitro models of senescence. The most common technique used to induce cell senescence was the addition to the culture medium of tumor necrosis factor (TNF)α and/or interleukin (IL)1β, followed by irradiation, compression, hydrogen peroxide (H2O2), microgravity, in vitro expansion up to passage 10, and cells harvested from damaged areas of explants. Few studies evaluated possible treatments to anti-senescence effects. The included studies used in vitro models of senescence in musculoskeletal tissues, providing powerful tools to evaluate age-related changes and pathologies, also contributing to the development of new therapeutic approaches.

The anti-aging mechanism of ginsenosides with medicine and food homology

With the acceleration of global aging and the rise in living standards, the achievement of healthy aging is becoming an imperative issue globally. Ginseng, a medicinal plant that has a long history of dietary intake and remarkable medicinal value, has become a research hotspot in the field of food and medicine. Ginsenosides, especially protopanaxadiol-type saponins and protopanaxatriol-type saponins, are among the most important active ingredients in ginseng. Ginsenosides have been found to exhibit powerful and diverse pharmacological activities, such as antiaging, antitumor, antifatigue and immunity enhancement activities. Their effects in antiaging mainly include (1) promotion of metabolism and stem cell proliferation, (2) protection of skin and nerves, (3) modulation of intestinal flora, (4) maintenance of mitochondrial function, and (5) enhancement of telomerase activity. The underlying mechanisms are primarily associated with the intervention of the signaling pathways in apoptosis, inflammation and oxidative stress. In this review, the mechanism of action of ginsenosides in antiaging as well as the potential values of developing ginsenoside-based functional foods and antiaging drugs are discussed.

Senescence of alveolar epithelial progenitor cells: a critical driver of lung fibrosis

Pulmonary fibrosis comprises a range of chronic interstitial lung diseases (ILDs) that impose a significant burden on patients and public health. Among these, idiopathic pulmonary fibrosis (IPF), a disease of aging, is the most common and most severe form of ILD and is treated largely by lung transplantation. The lack of effective treatments to stop or reverse lung fibrosis-in fact, fibrosis in most organs-has sparked the need to understand causative mechanisms with the goal of identifying critical points for potential therapeutic intervention. Findings from many groups have indicated that repeated injury to the alveolar epithelium-where gas exchange occurs-leads to stem cell exhaustion and impaired alveolar repair that, in turn, triggers the onset and progression of fibrosis. Cellular senescence of alveolar epithelial progenitors is a critical cause of stemness failure. Hence, senescence impairs repair and thus contributes significantly to fibrosis. In this review, we discuss recent evidence indicating that senescence of epithelial progenitor cells impairs alveolar homeostasis and repair creating a profibrotic environment. Moreover, we discuss the impact of senescent alveolar epithelial progenitors, alveolar type 2 (AT2) cells, and AT2-derived transitional epithelial cells in fibrosis. Emerging evidence indicates that transitional epithelial cells are prone to senescence and, hence, are a new player involved in senescence-associated lung fibrosis. Understanding the complex interplay of cell types and cellular regulatory factors contributing to alveolar epithelial progenitor senescence will be crucial to developing targeted therapies to mitigate their downstream profibrotic sequelae and to promote normal alveolar repair.NEW & NOTEWORTHY With an aging population, lung fibrotic diseases are becoming a global health burden. Dysfunctional repair of the alveolar epithelium is a key causative process that initiates lung fibrosis. Normal alveolar regeneration relies on functional progenitor cells; however, the senescence of these cells, which increases with age, hinders their ability to contribute to repair. Here, we discuss studies on the control and consequence of progenitor cell senescence in fibrosis and opportunities for research.

Resveratrol Reverses Endothelial Colony-Forming Cell Dysfunction in Adulthood in a Rat Model of Intrauterine Growth Restriction

Individuals born after intrauterine growth restriction (IUGR) are at risk of developing cardiovascular diseases (CVDs). Endothelial dysfunction plays a role in the pathogenesis of CVDs; and endothelial colony-forming cells (ECFCs) have been identified as key factors in endothelial repair. In a rat model of IUGR induced by a maternal low-protein diet, we observed an altered functionality of ECFCs in 6-month-old males, which was associated with arterial hypertension related to oxidative stress and stress-induced premature senescence (SIPS). Resveratrol (R), a polyphenol compound, was found to improve cardiovascular function. In this study, we investigated whether resveratrol could reverse ECFC dysfunctions in the IUGR group. ECFCs were isolated from IUGR and control (CTRL) males and were treated with R (1 μM) or dimethylsulfoxide (DMSO) for 48 h. In the IUGR-ECFCs, R increased proliferation (5'-bromo-2'-deoxyuridine (BrdU) incorporation, p < 0.001) and improved capillary-like outgrowth sprout formation (in Matrigel), nitric oxide (NO) production (fluorescent dye, p < 0.01), and endothelial nitric oxide synthase (eNOS) expression (immunofluorescence, p < 0.001). In addition, R decreased oxidative stress with reduced superoxide anion production (fluorescent dye, p < 0.001); increased Cu/Zn superoxide dismutase expression (Western blot, p < 0.05); and reversed SIPS with decreased beta-galactosidase activity (p < 0.001), and decreased p16^ink4a (p < 0.05) and increased Sirtuin-1 (p < 0.05) expressions (Western blot). No effects of R were observed in the CTRL-ECFCs. These results suggest that R reverses long-term ECFC dysfunctions related to IUGR.

Developmental Expression of the Cell Cycle Regulator p16INK4a in Retinal Glial Cells: A Novel Marker for Immature Ocular Astrocytes?

Retinal astrocytes are vital for neuronal homeostasis in the retina. Together with Müller glia, they provide retinal cells with neurotrophic factors, antioxidative support, and defense mechanisms such as the formation of the blood-retinal barrier. Substantial heterogeneity of astrocyte morphology and function represents a challenge for identification of distinct subtypes which may be potential targets for therapeutic purposes. Hence, identification of novel markers of astrocyte subpopulations is highly relevant to better understand the molecular mechanisms involved in retinal development, homeostasis, and pathology. In this study, we observed that the cell cycle regulator, p16INK4a, is expressed in immature astrocytes in the mouse retina. Immunohistochemical analysis showed p16INK4a expression in the optic nerve of wild-type mice from 3 days to 3 months of age and in the nerve fiber layer of the adult mouse retina. Colocalization of p16INK4a expression and glial fibrillary acidic protein (immature/mature astrocyte marker) tends to decrease with age. However, colocalization of p16INK4a expression and vimentin (immature astrocyte marker) remains high in the optic nerve from the early postnatal period to adulthood. The observations from this study provide a valuable tool for further investigations of ocular astrocytes in the developing retina as well as in degenerative retinopathies.

Controversies and Recent Advances in Senescence and Aging

Aging is the leading predictive factor of many chronic diseases that account for most of the morbidity and mortality worldwide, i [...]

The Pathological Activation of Microglia Is Modulated by Sexually Dimorphic Pathways

Microglia are the primary immunocompetent cells of the central nervous system (CNS). Their ability to survey, assess and respond to perturbations in their local environment is critical in their role of maintaining CNS homeostasis in health and disease. Microglia also have the capability of functioning in a heterogeneous manner depending on the nature of their local cues, as they can become activated on a spectrum from pro-inflammatory neurotoxic responses to anti-inflammatory protective responses. This review seeks to define the developmental and environmental cues that support microglial polarization towards these phenotypes, as well as discuss sexually dimorphic factors that can influence this process. Further, we describe a variety of CNS disorders including autoimmune disease, infection, and cancer that demonstrate disparities in disease severity or diagnosis rates between males and females, and posit that microglial sexual dimorphism underlies these differences. Understanding the mechanism behind differential CNS disease outcomes between men and women is crucial in the development of more effective targeted therapies.

Identification of a novel senescence-associated signature to predict biochemical recurrence and immune microenvironment for prostate cancer

Background

Prostate cancer (PCa) is an age-associated malignancy with high morbidity and mortality rate, posing a severe threat to public health. Cellular senescence, a specialized cell cycle arrest form, results in the secretion of various inflammatory mediators. In recent studies, senescence has shown an essential role in tumorigenesis and tumor development, yet the extensive effects of senescence in PCa have not been systematically investigated. Here, we aimed to develop a feasible senescence-associated prognosis model for early identification and appropriate management in patients with PCa.

Method

The RNA sequence results and clinical information available from The Cancer Genome Atlas (TCGA) and a list of experimentally validated senescence-related genes (SRGs) from the CellAge database were first obtained. Then, a senescence-risk signature related with prognosis was constructed using univariate Cox and LASSO regression analysis. We calculated the risk score of each patient and divided them into high-risk and low-risk groups in terms of the median value. Furthermore, two datasets (GSE70770 and GSE46602) were used to assess the effects of the risk model. A nomogram was built by integrating the risk score and clinical characteristics, which was further verified using ROC curves and calibrations. Finally, we compared the differences in the tumor microenvironment (TME) landscape, drug susceptibility, and the functional enrichment among the different risk groups.

Results

We established a unique prognostic signature in PCa patients based on eight SRGs, including CENPA, ADCK5, FOXM1, TFAP4, MAPK, LGALS3, BAG3, and NOX4, and validated well prognosis-predictive power in independent datasets. The risk model was associated with age and TNM staging, and the calibration chart presented a high consistency in nomogram prediction. Additionally, the prognostic signature could serve as an independent prediction factor due to its high accuracy. Notably, we found that the risk score was positively associated with tumor mutation burden (TMB) and immune checkpoint, whereas negatively correlated with tumor immune dysfunction and exclusion (TIDE), suggesting that these patients with risk scores were more sensitive to immunotherapy. Drug susceptibility analysis revealed differences in the responses to general drugs (docetaxel, cyclophosphamide, 5-Fluorouracil, cisplatin, paclitaxel, and vincristine) were yielded between the two risk groups.

Conclusion

Identifying the SRG-score signature may become a promising method for predicting the prognosis of patients with PCa and tailoring appropriate treatment strategies.

Exploiting pivotal mechanisms behind the senescence-like cell cycle arrest in cancer

Senescence-like cell cycle arrest is a critical state of cancer initiation and progression. Senescence is an irreversible cell cycle arrest in response to stress induced by extrinsic and intrinsic stimuli, including oxidative/genotoxic stress, oncogenic activation, irradiation, mitochondrial malfunction, or chemotherapeutic drugs. Several signaling pathways are involved in senescence-like cell cycle arrest, which is primarily induced by the activation of p53/p21-dependent apoptotic pathways and suppressing p16INK4A/retinoblastoma protein (pRB)-dependent oncogenic pathways. p21 is necessary for proper cell cycle advancement, is involved in cell death, and mediates p53-dependent cell cycle arrest caused by DNA damage. pRB's role in tumor suppression is through modulation of the G1 checkpoint in the cell cycle, as it has the ability to block S-phase entry and cell growth. The aforementioned pathways are also highly interconnected with significant crosstalk, such as cyclin-dependent kinases (CDK)/cyclin complexes, and the dimerization partner, RB-like, E2F and multi-vulval class B (DREAM) complex. The primary regulators of transcription are p53 and pRB, which maintain the senescent state through negative control of the cell cycle and process of tumorigenesis. Because CDK inhibitors comprise negative regulators of cell cycle progress, they are fundamental parts of each route. Prolonged overexpression of any of these four fundamental elements (p16, p53, p21, and pRB) suffices to induce senescence, demonstrating how the regulatory DREAM complex causes senescence and how its malfunction results in cell cycle progression. The present chapter aims at revealing the pivotal mechanisms behind the senescence-like cell cycle arrest in cancer.

Role of Senescent Cells in Cutaneous Wound Healing

Cellular senescence has gained increasing attention in the field of aging research. Senescent cells have been implicated in biological aging processes, tumorigenesis, development, and wound repair amongst other processes and pathologies. Recent findings reveal that senescent cells can both promote and inhibit cutaneous wound healing processes. Relating senescent cells in acute and chronic wounds will help to clarify their role in wound healing processes and inform our understanding of senescent cell heterogeneity. To clarify this apparent contradiction and guide future research and therapeutic development, we will review the rapidly growing field of cellular senescence and its role in wound healing biology.