Extension of life-span by introduction of telomerase into normal human cells

Telomeric i-motifs and C-strands inhibit parallel G-quadruplex extension by telomerase

Telomeric C-rich repeated DNA sequences fold into tetrahelical i-motif structures in vitro at acidic pH. While studies have suggested that i-motifs may form in cells, little is known about their potential role in human telomere biology. In this study, we explore the effect of telomeric C-strands and i-motifs on the ability of human telomerase to extend G-rich substrates. To promote i-motif formation at neutral pH, we use telomeric sequences where the cytidines have been substituted with 2'-fluoroarabinocytidine. Using FRET-based studies, we show that the stabilized i-motifs resist hybridization to concomitant parallel G-quadruplexes, implying that both structures could exist simultaneously at telomeric termini. Moreover, through telomerase activity assays, we show that both unstructured telomeric C-strands and telomeric i-motifs can inhibit the activity and processivity of telomerase extension of parallel G-quadruplexes and linear telomeric DNA. The data suggest at least three modes of inhibition by C-strands and i-motifs: direct hybridization to the substrate DNA, hybridization to nascent product DNA resulting in early telomerase dissociation, and interference with the unique mechanism of telomerase unwinding and extension of a G-quadruplex. Overall, this study highlights a potential inhibitory role for the telomeric C-strand in telomere maintenance.

Cellular Senescence in Cardiovascular Diseases: From Pathogenesis to Therapeutic Challenges

Cellular senescence (CS), classically considered a stable cell cycle withdrawal, is hallmarked by a progressive decrease in cell growth, differentiation, and biological activities. Senescent cells (SNCs) display a complicated senescence-associated secretory phenotype (SASP), encompassing a variety of pro-inflammatory factors that exert influence on the biology of both the cell and surrounding tissue. Among global mortality causes, cardiovascular diseases (CVDs) stand out, significantly impacting the living quality and functional abilities of patients. Recent data suggest the accumulation of SNCs in aged or diseased cardiovascular systems, suggesting their potential role in impairing cardiovascular function. CS operates as a double-edged sword: while it can stimulate the restoration of organs under physiological conditions, it can also participate in organ and tissue dysfunction and pave the way for multiple chronic diseases under pathological states. This review explores the mechanisms that underlie CS and delves into the distinctive features that characterize SNCs. Furthermore, we describe the involvement of SNCs in the progression of CVDs. Finally, the study provides a summary of emerging interventions that either promote or suppress senescence and discusses their therapeutic potential in CVDs.

Effects of hTERT transfection on the telomere and telomerase of Periplaneta americana cells in vitro

Telomere and telomerase are crucial factors in cell division and chromosome stability. Telomerase activity in most cells depends on the transcription control by the telomerase reverse transcriptase (TERT). The introduction of an exogenous human TERT (hTERT) in cultured cells could enhance telomerase activity and elongate the lifespan of various cells. Telomere elongation mechanisms vary between insects and are complex and unusual. Whether the use of exogenous hTERT can immortalize primary insect cells remains to be investigated. In this study, we used a recombinant virus expressing hTERT to infect primary cultured cells of Periplaneta americana and evaluated its effects on insect cell immortalization. We found that hTERT was successfully expressed and promoted the growth of P. americana cells, shortening their doubling time. This was due to the ability of hTERT to increase the activity of telomerase in P. americana cells, thus prolonging the telomeres. Our study lays the foundation for understanding the mechanisms of telomere elongation in P. americana, and suggests that the introduction of hTERT into insect cells could be an efficient way to establish certain insect cell lines.

Exosomes derived from mesenchymal stem cells primed with disease-condition-serum improved therapeutic efficacy in a mouse rheumatoid arthritis model via enhanced TGF-β1 production

BACKGROUNDS

Rheumatoid arthritis (RA) is a chronic and systemic autoimmune disease characterized by synovial inflammation-mediated progressive destruction of the cartilage and bone, resulting in reduced quality of life. We primed human telomerase reverse transcriptase-overexpressing immortalized human adipose tissue-derived mesenchymal stem cells (iMSCs) with serum derived from a non-human primate RA model and studied the immunomodulatory ability of exosomes obtained from primed iMSCs.

METHODS

After immunophenotyping, nanoparticle tracking analysis, and in vitro functional tests, Dulbecco's phosphate-buffered saline (dPBS, Group C), exosomes derived from the supernatant of iMSCs (Exo-FBS, Group E), exosomes derived from the supernatant of iMSCs primed with RA serum (Exo-RA, Group F), and methotrexate (Group M) were administered in collagen-induced arthritis (CIA) model mice. dPBS was administered to the normal (N) group for comparison (n = 10/group).

RESULTS

Exo-RA had a significantly higher number of exosomes compared to Exo-FBS when measured with nanoparticle tracking analysis or exosome marker CD81, and Transforming growth factor-β1 amounts were significantly higher in Exo-RA than in Exo-FBS. When Exo-FBS or Exo-RA was administered to the collagen-induced arthritis model, serum interleukin (IL)-4 and the proportion of Th2 (CD4+CD25+GATA3+) and M2 (CD11c - CD206+ of CD45+CD64+) cells were significantly increased compared to the control group. Furthermore, Exo-RA could alleviate cartilage damage by significantly lowering the concentrations of proinflammatory cytokines such as tumor necrosis factor-α, keratinocyte chemoattractant, and IL-12p70.

CONCLUSION

Exosomes derived from disease-condition-serum-primed iMSCs ameliorated cartilage damage in a RA model by enhancing TGF-β1 production, inducing Th2 and M2 polarization and lowering proinflammatory cytokines, TNF-α, KC, and IL-12p70 in the host. Patient-derived serum can be used as an iMSC priming strategy in iMSC-derived exosome treatment of RA.

Strategies for senolytic drug discovery

Senolytics are a category of drugs that reduce the impact of cellular senescence, an effect associated with a range of chronic and age-related diseases. Since the discovery of the first senolytics in 2015, the number of known senolytic agents has grown dramatically. This review discusses the broad categories of known senolytics-kinase inhibitors, Bcl-2 family protein inhibitors, naturally occurring polyphenols, heat shock protein inhibitors, BET family protein inhibitors, P53 stabilizers, repurposed anti-cancer drugs, cardiac steroids, PPAR-alpha agonists, and antibiotics. The approaches used to screen for new senolytics are articulated including a range of methods to induce senescence, different target cell types, various senolytic assays, and markers. The choice of methods can greatly influence the outcomes of a screen, with high-quality screens featuring robust systems, adequate controls, and extensive validation in alternate assays. Recent advances in single-cell analysis and computational methods for senolytic identification are also discussed. There is significant potential for further drug discovery, but this will require additional research into drug targets and mechanisms of actions and their subsequent rigorous evaluation in pre-clinical models and human trials.

The Role of Advanced Parental Age in Reproductive Genetics

The increase of parental reproductive age is a worldwide trend in modern society in recent decades. In general, older parents have a significant impact on reproductive genetics and the health of offspring. In particular, advanced parental age contributes to the increase in the risk of adverse neurodevelopmental outcomes in offspring. However, it is currently under debate how and to what extent the health of future generations was affected by the parental age. In this review, we aimed to (i) provide an overview of the effects of age on the fertility and biology of the reproductive organs of the parents, (ii) highlight the candidate biological mechanisms underlying reproductive genetic alterations, and (iii) discuss the relevance of the effect of parental age on offspring between animal experiment and clinical observation. In addition, we think that the impact of environmental factors on cognitive and emotional development of older offspring will be an interesting direction.

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.

Irreversible cell cycle exit associated with senescence is mediated by constitutive MYC degradation

Cells can irreversibly exit the cell cycle and become senescent to safeguard against uncontrolled proliferation. While the p53-p21 and p16-Rb pathways are thought to mediate senescence, they also mediate reversible cell cycle arrest (quiescence), raising the question of whether senescence is actually reversible or whether alternative mechanisms underly the irreversibility associated with senescence. Here, we show that senescence is irreversible and that commitment to and maintenance of senescence are mediated by irreversible MYC degradation. Senescent cells start dividing when a non-degradable MYC mutant is expressed, and quiescent cells convert to senescence when MYC is knocked down. In early oral carcinogenesis, epithelial cells exhibit MYC loss and become senescent as a safeguard against malignant transformation. Later stages of oral premalignant lesions exhibit elevated MYC levels and cellular dysplasia. Thus, irreversible cell cycle exit associated with senescence is mediated by constitutive MYC degradation, but bypassing this degradation may allow tumor cells to escape during cancer initiation.

TERT transcription and translocation into mitochondria regulate benzo[a]pyrene/BPDE-induced senescence and mitochondrial damage in mouse spermatocytes

Telomere and mitochondria may be the targets of Benzo[a]pyrene (BaP) -induced male reproductive damage, and further elucidation of the toxic molecular mechanisms is necessary. In this study, we used in vivo and in vitro exposure models to explore the molecular mechanisms of TERT regulation in BaP-induced telomere and mitochondrial damage in spermatocytes. The results showed that the treatment of benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), the active metabolite of BaP, caused telomere dysfunction in mouse spermatocyte-derived GC-2 cells, resulting in S-phase arrest and increased senescence-associated secretory phenotype (SASP). These effects were significantly alleviated by telomerase agonist (ABG) pretreatment in GC-2 cells. SIRT1, FOXO3a, or c-MYC overexpressing GC-2 cell models were established to demonstrate that BPDE inhibited TERT transcriptional expression through the SIRT1/FOXO3a/c-MYC pathway, leading to telomere dysfunction. We also observed that BPDE induced mitochondrial compromise, including complex I damage, accompanied by reduced mitochondrial TERT expression. Based on this, we constructed wild-type TERT-overexpressing (OE-TERTwt) and mitochondria targeting TERT-overexpressing (OE-TERTmst) GC-2 cell models and found that OE-TERTmst GC-2 cells improved mitochondrial function better than OE-TERTwt GC-2 cells. Finally, ICR mice were given BaP by intragastric administration for 35 days, which verified the results of the in vitro study. The results shown that BaP exposure can lead to spermatogenesis disturbance, which is related to the telomere and mitochondrial damage in spermatocytes. In conclusion, our results suggest that BPDE causes telomere and mitochondrial damage in spermatocytes by inhibiting TERT transcription and mitochondrial TERT expression. This study elucidates the molecular mechanism of male reproductive toxicity due to environmental pollutant BaP, and also provides a new perspective for the exploration of interventions and protective measures against male reproductive damage by BaP.

Combining old and new concepts in targeting telomerase for cancer therapy: transient, immediate, complete and combinatory attack (TICCA)

Telomerase can overcome replicative senescence by elongation of telomeres but is also a specific element in most cancer cells. It is expressed more vastly than any other tumor marker. Telomerase as a tumor target inducing replicative immortality can be overcome by only one other mechanism: alternative lengthening of telomeres (ALT). This limits the probability to develop resistance to treatments. Moreover, telomerase inhibition offers some degree of specificity with a low risk of toxicity in normal cells. Nevertheless, only one telomerase antagonist reached late preclinical studies. The underlying causes, the pitfalls of telomerase-based therapies, and future chances based on recent technical advancements are summarized in this review. Based on new findings and approaches, we propose a concept how long-term survival in telomerase-based cancer therapies can be significantly improved: the TICCA (Transient Immediate Complete and Combinatory Attack) strategy.

[Skin aging-cellular senescence : What is the future?]

BACKGROUND

Cellular senescence is the main cause of skin and organ aging and is associated with a wide range of aging-related diseases.

OBJECTIVES

To understand which senolytics, senomorphics, and cell-based therapies have been developed to alleviate and even rejuvenate skin aging and reduce cellular senescence.

METHODS

Basic literature for the mode of action of senolytics and senomorphics and their clinical perspectives in daily routine are discussed.

RESULTS

Various causes lead to mitochondrial dysfunction and the activation of pro-aging signaling pathways, which eventually lead to cellular senescence with degradation of structural proteins of the dermal connective tissue and severe suppression of regenerative stem cell niches of the skin.

CONCLUSIONS

Depletion of senescent cells suppress skin aging and enforce rejuvenation of skin and other organs and their function. The removal of senescent cells by cells of the native immune system is severely disturbed during aging. Selected senolytics and senomorphics are approved and are already on the market.

CDK2 regulates collapsed replication fork repair in CCNE1-amplified ovarian cancer cells via homologous recombination

CCNE1 amplification is a common alteration in high-grade serous ovarian cancer and occurs in 15-20% of these tumors. These amplifications are mutually exclusive with homologous recombination deficiency, and, as they have intact homologous recombination, are intrinsically resistant to poly (ADP-ribose) polymerase inhibitors or chemotherapy agents. Understanding the molecular mechanisms that lead to this mutual exclusivity may reveal therapeutic vulnerabilities that could be leveraged in the clinic in this still underserved patient population. Here, we demonstrate that CCNE1-amplified high-grade serous ovarian cancer cells rely on homologous recombination to repair collapsed replication forks. Cyclin-dependent kinase 2, the canonical partner of cyclin E1, uniquely regulates homologous recombination in this genetic context, and as such cyclin-dependent kinase 2 inhibition synergizes with DNA damaging agents in vitro and in vivo. We demonstrate that combining a selective cyclin-dependent kinase 2 inhibitor with a DNA damaging agent could be a powerful tool in the clinic for high-grade serous ovarian cancer.

The other side of the coin: mesenchymal stromal cell immortalization beyond evasion of senescence

Mesenchymal stromal cells (MSC) are promising options to cellular therapy to several clinical disorders, mainly because of its ability to immunomodulate and differentiate into different cell types. Even though MSC can be isolated from different sources, a major challenge to understanding the biological effects is that the primary cells undergo replicative senescence after a limited number of cell divisions in culture, requiring time-consuming and technically challenging approaches to get a sufficient cell number for clinical applications. Therefore, a new isolation, characterization, and expansion is necessary every time, which increases the variability and is time-consuming. Immortalization is a strategy that can overcome these challenges. Therefore, here, we review the different methodologies available to cellular immortalization, and discuss the literature regarding MSC immortalization and the broader biological consequences that extend beyond the mere increase in proliferation potential.

Practical Use of Immortalized Cells in Medicine: Current Advances and Future Perspectives

In modern science, immortalized cells are not only a convenient tool in fundamental research, but they are also increasingly used in practical medicine. This happens due to their advantages compared to the primary cells, such as the possibility to produce larger amounts of cells and to use them for longer periods of time, the convenience of genetic modification, the absence of donor-to-donor variability when comparing the results of different experiments, etc. On the other hand, immortalization comes with drawbacks: possibilities of malignant transformation and/or major phenotype change due to genetic modification itself or upon long-term cultivation appear. At first glance, such issues are huge hurdles in the way of immortalized cells translation into medicine. However, there are certain ways to overcome such barriers that we describe in this review. We determined four major areas of usage of immortalized cells for practical medicinal purposes, and each has its own means to negate the drawbacks associated with immortalization. Moreover, here we describe specific fields of application of immortalized cells in which these problems are of much lesser concern, for example, in some cases where the possibility of malignant growth is not there at all. In general, we can conclude that immortalized cells have their niches in certain areas of practical medicine where they can successfully compete with other therapeutic approaches, and more preclinical and clinical trials with them should be expected.

Cellular and Genomic Features of Muscle Differentiation from Isogenic Fibroblasts and Myoblasts

The ability to recapitulate muscle differentiation in vitro enables the exploration of mechanisms underlying myogenesis and muscle diseases. However, obtaining myoblasts from patients with neuromuscular diseases or from healthy subjects poses ethical and procedural challenges that limit such investigations. An alternative consists in converting skin fibroblasts into myogenic cells by forcing the expression of the myogenic regulator MYOD. Here, we directly compared cellular phenotype, transcriptome, and nuclear lamina-associated domains (LADs) in myo-converted human fibroblasts and myotubes differentiated from myoblasts. We used isogenic cells from a 16-year-old donor, ruling out, for the first time to our knowledge, genetic factors as a source of variations between the two myogenic models. We show that myo-conversion of fibroblasts upregulates genes controlling myogenic pathways leading to multinucleated cells expressing muscle cell markers. However, myotubes are more advanced in myogenesis than myo-converted fibroblasts at the phenotypic and transcriptomic levels. While most LADs are shared between the two cell types, each also displays unique domains of lamin A/C interactions. Furthermore, myotube-specific LADs are more gene-rich and less heterochromatic than shared LADs or LADs unique to myo-converted fibroblasts, and they uniquely sequester developmental genes. Thus, myo-converted fibroblasts and myotubes retain cell type-specific features of radial and functional genome organization. Our results favor a view of myo-converted fibroblasts as a practical model to investigate the phenotypic and genomic properties of muscle cell differentiation in normal and pathological contexts, but also highlight current limitations in using fibroblasts as a source of myogenic cells.

Establishment and characterization of a novel kidney cell line derived from the common bottlenose dolphin

Common bottlenose dolphin (Tursiops truncatus) is a well-known cetacean species that inhabits temperate and tropical seas worldwide. Limited supply and poor quality of samples hinder the investigation of the effects of various pathogens and environmental pollutants on this cetacean species. Cultured cells are useful for experimental studies; however, no cell lines derived from cetaceans are generally available. Therefore, in this study, we established a novel kidney cell line, TK-ST, derived from T. truncatus. Primary cells exhibited the morphological characteristics of epithelial and fibroblast cells, but their immortalization and passaging resulted in a predominantly epithelial cell morphology. TK-ST was immortalized using the large T SV40 antigen and human telomerase reverse transcriptase and exhibited long-term stable cell growth. TK-ST cells are generally cultured in Dulbecco's modified Eagle's medium with 10% fetal bovine serum at 37°C and 5% CO2 but can also be cultured in 5-20% fetal bovine serum and several other classical media commonly used for common animal cell culture. TK-ST cells were found to be susceptible to several viruses, including the dolphin morbillivirus (most important virus in cetaceans), and exhibited cytopathic effects, facilitating the replication of the dolphin morbillivirus. Furthermore, mRNA expression levels of cytokine genes were increased in TK-ST cells after stimulation with lipopolysaccharides and poly(I:C). Therefore, the novel TK-ST cell line derived in this study can potentially be used for further in vitro studies on cetaceans.

Human granulosa cells of poor ovarian responder patients display telomeres shortening

OBJECTIVE

We aimed to compare the telomere length in granulosa cells of the young normal and poor ovarian responder patients and elderly patients undergoing ovarian stimulation for IVF.

METHODS

The main outcome measures granulosa cells telomere Length in the 3 study groups of patients undergoing IVF treatment in our center. 1) young normal responder patients (< 35 years); 2) young (< 35 years) poor ovarian responder patients; and 3) Elderly patients (40-45 years). Granulosa cells were obtained at the time of oocyte retrieval. Granulosa cells telomere length was assessed by absolute human telomere length quantification qPCR Assay.

RESULTS

The telomere length of the young normal responder was significantly longer as compared to young poor ovarian responder (15.5 vs 9.6 KB, p < 0.001) and the elderly patients (15.5 vs 10.66 KB, p < 0.002). No significant difference was observed in the telomere length between the young poor ovarian responder and the elderly patients.

CONCLUSIONS

Granulosa cells telomere length of the young normal responder was found to be significantly longer than young poor ovarian responder or elderly patients, highlighting the role of telomere length as a predictor, or contributor to poor oocyte yield following IVF treatment.

Cellular senescence and neurodegeneration

Advancing age is a major risk factor of Alzheimer's disease (AD). The worldwide prevalence of AD is approximately 50 million people, and this number is projected to increase substantially. The molecular mechanisms underlying the aging-associated susceptibility to cognitive impairment in AD are largely unknown. As a hallmark of aging, cellular senescence is a significant contributor to aging and age-related diseases including AD. Senescent neurons and glial cells have been detected to accumulate in the brains of AD patients and mouse models. Importantly, selective elimination of senescent cells ameliorates amyloid beta and tau pathologies and improves cognition in AD mouse models, indicating a critical role of cellular senescence in AD pathogenesis. Nonetheless, the mechanisms underlying when and how cellular senescence contributes to AD pathogenesis remain unclear. This review provides an overview of cellular senescence and discusses recent advances in the understanding of the impact of cellular senescence on AD pathogenesis, with brief discussions of the possible role of cellular senescence in other neurodegenerative diseases including Down syndrome, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis.

Cancer 3D Models for Metallodrug Preclinical Testing

Despite being standard tools in research, the application of cellular and animal models in drug development is hindered by several limitations, such as limited translational significance, animal ethics, and inter-species physiological differences. In this regard, 3D cellular models can be presented as a step forward in biomedical research, allowing for mimicking tissue complexity more accurately than traditional 2D models, while also contributing to reducing the use of animal models. In cancer research, 3D models have the potential to replicate the tumor microenvironment, which is a key modulator of cancer cell behavior and drug response. These features make cancer 3D models prime tools for the preclinical study of anti-tumoral drugs, especially considering that there is still a need to develop effective anti-cancer drugs with high selectivity, minimal toxicity, and reduced side effects. Metallodrugs, especially transition-metal-based complexes, have been extensively studied for their therapeutic potential in cancer therapy due to their distinctive properties; however, despite the benefits of 3D models, their application in metallodrug testing is currently limited. Thus, this article reviews some of the most common types of 3D models in cancer research, as well as the application of 3D models in metallodrug preclinical studies.

Predicting the number of lifetime divisions for hematopoietic stem cells from telomere length measurements

How many times does a typical hematopoietic stem cell (HSC) divide to maintain a daily production of over 1011 blood cells over a human lifetime? It has been predicted that relatively few, slowly dividing HSCs occupy the top of the hematopoietic hierarchy. However, tracking HSCs directly is extremely challenging due to their rarity. Here, we utilize previously published data documenting the loss of telomeric DNA repeats in granulocytes, to draw inferences about HSC division rates, the timing of major changes in those rates, as well as lifetime division totals. Our method uses segmented regression to identify the best candidate representations of the telomere length data. Our method predicts that, on average, an HSC divides 56 times over an 85-year lifespan (with lower and upper bounds of 36 and 120, respectively), with half of these divisions during the first 24 years of life.

Regulation of Cellular Senescence in Type 2 Diabetes Mellitus: From Mechanisms to Clinical Applications

Cellular senescence is accelerated by hyperglycemia through multiple pathways. Therefore, senescence is an important cellular mechanism to consider in the pathophysiology of type 2 diabetes mellitus (T2DM) and an additional therapeutic target. The use of drugs that remove senescent cells has led to improvements in blood glucose levels and diabetic complications in animal studies. Although the removal of senescent cells is a promising approach for the treatment of T2DM, two main challenges limit its clinical application: the molecular basis of cellular senescence in each organ is yet to be understood, and the specific effect of removing senescent cells in each organ has to be determined. This review aims to discuss future applications of targeting senescence as a therapeutic option in T2DM and elucidate the characteristics of cellular senescence and senescence-associated secretory phenotype in the tissues important for regulating glucose levels: pancreas, liver, adipocytes, and skeletal muscle.

TERT Mutations in Non-Small Cell Lung Cancer: Clinicopathologic Features and Prognostic Implications

Introduction

The associations between the clinical characteristics of non-small cell lung cancer (NSCLC) and mutations in telomerase reverse transcriptase (TERT) gene remain unclear. In this study, we used next-generation sequencing (NGS) to investigate the incidence rate and clinical correlates of TERT mutations in patients with NSCLC.

Methods

In total, 283 tumor samples from patients with NSCLC were tested using an NGS panel from September 2017 to May 2020. The genetic testing results and clinical data of all patients were collected.

Results

TERT mutations were found in 30 patients, which were significantly associated with age, smoking history, sex, and metastasis (P < 0.05). Survival analyses showed that patients who carried TERT mutations had a poorer prognosis. Of the 30 TERT-mutation carriers, 17 harbored epidermal growth factor receptor (EGFR) mutations, which were significantly associated with sex, histopathology type, and metastasis (P < 0.05; overall survival [OS], 21 months; 95% confidence interval [CI], 8.153-33.847 months). Three TERT mutation patients harbored Kirsten rat sarcoma virus (KRAS) mutations, which were significantly associated with metastasis risk (P < 0.05), KRAS mutations carriers had a worse prognosis, with an OS of 10 months (95% CI, 8.153-33.847 months). Multivariate Cox regression analyses showed that age, cancer stage, and TERT mutation carrier status were independent risk factors for NSCLC, and the TERT mutation was 2.731 times higher than that without TERT mutation (95% CI, 1.689-4.418, P < 0.001).

Conclusions

TERT mutations were present in 11% of patients with NSCLC. TERT mutations were associated with age, smoking history, sex, and distant metastasis. Co-mutations in TERT and EGFR/KRAS indicated a poor prognosis. The co-mutations of TERT and EGFR differed according to sex, histopathology type, and metastasis, whereas TERT and KRAS co-mutations were only associated with patient metastasis. Age, cancer stage, and TERT mutation carrier status were independent risk factors for poor prognosis in patients with NSCLC.

Stress-induced senescence in mesenchymal stem cells: Triggers, hallmarks, and current rejuvenation approaches

Mesenchymal stem cells (MSCs) have emerged as promising cell-based therapies in the treatment of degenerative and inflammatory conditions. However, despite accumulating evidence of the breadth of MSC functional potency, their broad clinical translation is hampered by inconsistencies in therapeutic efficacy, which is at least partly due to the phenotypic and functional heterogeneity of MSC populations as they progress towards senescence in vitro. MSC senescence, a natural response to aging and stress, gives rise to altered cellular responses and functional decline. This review describes the key regenerative properties of MSCs; summarises the main triggers, mechanisms, and consequences of MSC senescence; and discusses current cellular and extracellular strategies to delay the onset or progression of senescence, or to rejuvenate biological functions lost to senescence.

Loss of FAM111B protease mutated in hereditary fibrosing poikiloderma negatively regulates telomere length

Hereditary fibrosing poikiloderma (HFP) is a rare human dominant negative disorder caused by mutations in the FAM111B gene that encodes a nuclear trypsin-like serine protease. HFP patients present with symptoms including skin abnormalities, tendon contractures, myopathy and lung fibrosis. We characterized the cellular roles of human FAM111B using U2OS and MCF7 cell lines and report here that the protease interacts with components of the nuclear pore complex. Loss of FAM111B expression resulted in abnormal nuclear shape and reduced telomeric DNA content suggesting that FAM111B protease is required for normal telomere length; we show that this function is independent of telomerase or recombination driven telomere extension. Even though FAM111B-deficient cells were proficient in DNA repair, they showed hallmarks of genomic instability such as increased levels of micronuclei and ultra-fine DNA bridges. When mutated as in HFP, FAM111B was more frequently localized to the nuclear envelope, suggesting that accumulation of the mutated protease at the nuclear periphery may drive the disease pathology.

Identification and validation of a cellular senescence-related lncRNA signature for prognostic prediction in patients with multiple myeloma

Multiple myeloma (MM) is the second most common hematologic malignancy, which primarily occurs in the elderly. Cellular senescence is considered to be closely associated with the occurrence and progression of malignant tumors including MM, and lncRNA can mediate the process of cellular senescence by regulating key signaling pathways such as p53/p21 and p16/RB. However, the role of cellular senescence related lncRNAs (CSRLs) in MM development has never been reported. Herein, we identified 11 CSRLs (AC004918.5, AC103858.1, AC245100.4, ACBD3-AS1, AL441992.2, ATP2A1-AS1, CCDC18-AS1, LINC00996, TMEM161B-AS1, RP11-706O15.1, and SMURF2P1) to build the CSRLs risk model, which was confirmed to be highly associated with overall survival (OS) of MM patients. We further demonstrated the strong prognostic value of the risk model in MM patients receiving different regimens, especially for those with three-drug combination of bortezomib, lenalidomide, and dexamethasone (VRd) as first-line therapy. Not only that, our risk model also excels in predicting the OS of MM patients at 1, 2, and 3 years. In order to verify the function of these CSRLs in MM, we selected the lncRNA ATP2A1-AS1 which presented the largest expression difference between high-risk groups and low-risk groups for subsequent analysis and validation. Finally, we found that down-regulation of ATP2A1-AS1 can promote cellular senescence in MM cell lines. In conclusion, the CSRLs risk model established in present study provides a novel and more accurate method for predicting MM patients' prognosis and identifies a new target for MM therapeutic intervention.

Advances in PET imaging of cancer

Molecular imaging has experienced enormous advancements in the areas of imaging technology, imaging probe and contrast development, and data quality, as well as machine learning-based data analysis. Positron emission tomography (PET) and its combination with computed tomography (CT) or magnetic resonance imaging (MRI) as a multimodality PET-CT or PET-MRI system offer a wealth of molecular, functional and morphological data with a single patient scan. Despite the recent technical advances and the availability of dozens of disease-specific contrast and imaging probes, only a few parameters, such as tumour size or the mean tracer uptake, are used for the evaluation of images in clinical practice. Multiparametric in vivo imaging data not only are highly quantitative but also can provide invaluable information about pathophysiology, receptor expression, metabolism, or morphological and functional features of tumours, such as pH, oxygenation or tissue density, as well as pharmacodynamic properties of drugs, to measure drug response with a contrast agent. It can further quantitatively map and spatially resolve the intertumoural and intratumoural heterogeneity, providing insights into tumour vulnerabilities for target-specific therapeutic interventions. Failure to exploit and integrate the full potential of such powerful imaging data may lead to a lost opportunity in which patients do not receive the best possible care. With the desire to implement personalized medicine in the cancer clinic, the full comprehensive diagnostic power of multiplexed imaging should be utilized.

Establishing and characterizing human stem cells from the apical papilla immortalized by hTERT gene transfer

Stem cells from the apical papilla (SCAPs) are promising candidates for regenerative endodontic treatment and tissue regeneration in general. However, harvesting enough cells from the limited apical papilla tissue is difficult, and the cells lose their primary phenotype over many passages. To get over these challenges, we immortalized human SCAPs with lentiviruses overexpressing human telomerase reverse transcriptase (hTERT). Human immortalized SCAPs (hiSCAPs) exhibited long-term proliferative activity without tumorigenic potential. Cells also expressed mesenchymal and progenitor biomarkers and exhibited multiple differentiation potentials. Interestingly, hiSCAPs gained a stronger potential for osteogenic differentiation than the primary cells. To further investigate whether hiSCAPs could become prospective seed cells in bone tissue engineering, in vitro and in vivo studies were performed, and the results indicated that hiSCAPs exhibited strong osteogenic differentiation ability after infection with recombinant adenoviruses expressing BMP9 (AdBMP9). In addition, we revealed that BMP9 could upregulate ALK1 and BMPRII, leading to an increase in phosphorylated Smad1 to induce the osteogenic differentiation of hiSCAPs. These results support the application of hiSCAPs in tissue engineering/regeneration schemes as a stable stem cell source for osteogenic differentiation and biomineralization, which could be further used in stem cell-based clinical therapies.

Critically short telomeres derepress retrotransposons to promote genome instability in embryonic stem cells

Telomeres, at the ends of chromosomes, protect chromosomes from fusion and preserve genomic stability. However, the molecular mechanisms underlying telomere attrition-induced genome instability remain to be understood. We systematically analyzed the expression of retrotransposons and performed genomic sequencing of different cell and tissue types with telomeres of varying lengths due to telomerase deficiency. We found that critically short telomeres altered retrotransposon activity to promote genomic instability in mouse embryonic stem cells, as evidenced by elevated numbers of single nucleotide variants, indels and copy number variations (CNVs). Transpositions of retrotransposons such as LINE1 resulting from the short telomeres can also be found in these genomes with elevated number of mutations and CNVs. Retrotransposon activation is linked to increased chromatin accessibility, and reduced heterochromatin abundance correlates with short telomeres. Re-elongation of telomeres upon recovery of telomerase partly represses retrotransposons and heterochromatin accumulation. Together, our findings suggest a potential mechanism by which telomeres maintain genomic stability by suppressing chromatin accessibility and retrotransposon activity.

NPCs and APBs: two HUBs of non-canonical homology-based recombination at telomeres?

Apart from a few rare exceptions, the maintenance of functional telomeres by recombination-based mechanisms is restricted to accidental and/or pathological situations. Originally described in the yeast S. cerevisiae, this mode of telomere repair has gained interest with the discovery of telomerase negative cancers that use alternative lengthening of telomeres (ALT cancer) dependent on homologous recombination. In both yeast and humans, it has been shown that recombination at telomeres is spatially regulated and occurs preferentially at the nuclear pore complexes (NPCs) in yeast and at ALT-associated promyelocytic leukemia nuclear bodies (APBs) in human cells. Here, we discuss the potential relationships between these two membrane-less structures and their role in enabling unconventional recombination pathways.

The genome-wide mutational consequences of DNA hypomethylation

DNA methylation is important for establishing and maintaining cell identity and for genomic stability. This is achieved by regulating the accessibility of regulatory and transcriptional elements and the compaction of subtelomeric, centromeric, and other inactive genomic regions. Carcinogenesis is accompanied by a global loss in DNA methylation, which facilitates the transformation of cells. Cancer hypomethylation may also cause genomic instability, for example through interference with the protective function of telomeres and centromeres. However, understanding the role(s) of hypomethylation in tumor evolution is incomplete because the precise mutational consequences of global hypomethylation have thus far not been systematically assessed. Here we made genome-wide inventories of all possible genetic variation that accumulates in single cells upon the long-term global hypomethylation by CRISPR interference-mediated conditional knockdown of DNMT1. Depletion of DNMT1 resulted in a genomewide reduction in DNA methylation. The degree of DNA methylation loss was similar to that observed in many cancer types. Hypomethylated cells showed reduced proliferation rates, increased transcription of genes, reactivation of the inactive X-chromosome and abnormal nuclear morphologies. Prolonged hypomethylation was accompanied by increased chromosomal instability. However, there was no increase in mutational burden, enrichment for certain mutational signatures or accumulation of structural variation to the genome. In conclusion, the primary consequence of hypomethylation is genomic instability, which in cancer leads to increased tumor heterogeneity and thereby fuels cancer evolution.

A robust reprogramming strategy for generating hepatocyte-like cells usable in pharmaco-toxicological studies

BACKGROUND

High-throughput pharmaco-toxicological testing frequently relies on the use of established liver-derived cell lines, such as HepG2 cells. However, these cells often display limited hepatic phenotype and features of neoplastic transformation that may bias the interpretation of the results. Alternate models based on primary cultures or differentiated pluripotent stem cells are costly to handle and difficult to implement in high-throughput screening platforms. Thus, cells without malignant traits, optimal differentiation pattern, producible in large and homogeneous amounts and with patient-specific phenotypes would be desirable.

METHODS

We have designed and implemented a novel and robust approach to obtain hepatocytes from individuals by direct reprogramming, which is based on a combination of a single doxycycline-inducible polycistronic vector system expressing HNF4A, HNF1A and FOXA3, introduced in human fibroblasts previously transduced with human telomerase reverse transcriptase (hTERT). These cells can be maintained in fibroblast culture media, under standard cell culture conditions.

RESULTS

Clonal hTERT-transduced human fibroblast cell lines can be expanded at least to 110 population doublings without signs of transformation or senescence. They can be easily differentiated at any cell passage number to hepatocyte-like cells with the simple addition of doxycycline to culture media. Acquisition of a hepatocyte phenotype is achieved in just 10 days and requires a simple and non-expensive cell culture media and standard 2D culture conditions. Hepatocytes reprogrammed from low and high passage hTERT-transduced fibroblasts display very similar transcriptomic profiles, biotransformation activities and show analogous pattern behavior in toxicometabolomic studies. Results indicate that this cell model outperforms HepG2 in toxicological screening. The procedure also allows generation of hepatocyte-like cells from patients with given pathological phenotypes. In fact, we succeeded in generating hepatocyte-like cells from a patient with alpha-1 antitrypsin deficiency, which recapitulated accumulation of intracellular alpha-1 antitrypsin polymers and deregulation of unfolded protein response and inflammatory networks.

CONCLUSION

Our strategy allows the generation of an unlimited source of clonal, homogeneous, non-transformed induced hepatocyte-like cells, capable of performing typical hepatic functions and suitable for pharmaco-toxicological high-throughput testing. Moreover, as far as hepatocyte-like cells derived from fibroblasts isolated from patients suffering hepatic dysfunctions, retain the disease traits, as demonstrated for alpha-1-antitrypsin deficiency, this strategy can be applied to the study of other cases of anomalous hepatocyte functionality.

SAMHD1 restricts the deoxyguanosine triphosphate pool contributing to telomere stability in telomerase-positive cells

SAMHD1 (Sterile alpha motif and histidine/aspartic acid domain-containing protein 1) is a dNTP triphosphohydrolase crucial in the maintenance of balanced cellular dNTP pools, which support genome integrity. In SAMHD1 deficient fibroblasts isolated from Aicardi-Goutières Syndrome (AGS) patients, all four DNA precursors are increased and markedly imbalanced with the largest effect on dGTP, a key player in the modulation of telomerase processivity. Here, we present data showing that SAMHD1, by restricting the dGTP pool, contributes to telomere maintenance in hTERT-immortalized human fibroblasts from AGS patients as well as in telomerase positive cancer cell lines. Only in cells expressing telomerase, the lack of SAMHD1 causes excessive lengthening of telomeres and telomere fragility, whereas primary fibroblasts lacking both SAMHD1 and telomerase enter normally into senescence. Telomere lengthening observed in SAMHD1 deficient but telomerase proficient cells is a gradual process, in accordance with the intrinsic property of telomerase of adding only a few tens of nucleotides for each cycle. Therefore, only a prolonged exposure to high dGTP content causes telomere over-elongation. hTERT-immortalized AGS fibroblasts display also high fragility of chromosome ends, a marker of telomere replication stress. These results not only demonstrate the functional importance of dGTP cellular level but also reveal the critical role played by SAMHD1 in restraining telomerase processivity and safeguarding telomere stability.

Ageing as a software design flaw

Ageing is inherent to all human beings, yet why we age remains a hotly contested topic. Most mechanistic explanations of ageing posit that ageing is caused by the accumulation of one or more forms of molecular damage. Here, I propose that we age not because of inevitable damage to the hardware but rather because of intrinsic design flaws in the software, defined as the DNA code that orchestrates how a single cell develops into an adult organism. As the developmental software runs, its sequence of events is reflected in shifting cellular epigenetic states. Overall, I suggest that to understand ageing we need to decode our software and the flow of epigenetic information throughout the life course.

Inhibition of posterior capsule opacification by adenovirus-mediated delivery of short hairpin RNAs targeting TERT in a rabbit model

PURPOSE

Posterior capsule opacification (PCO) is the most common postoperative complication after cataract surgery and cannot yet be eliminated. Here, we investigated the inhibitory effects of telomerase reverse transcriptase (TERT) gene silencing on PCO in a rabbit model.

METHODS

After rabbit lens epithelial cells (LECs) were treated with adenovirus containing short hairpin RNAs (shRNA) targeting TERT (shTERT group), adenovirus containing scramble nonsense control shRNA (shNC group) or PBS (control group), quantitative real-time polymerase chain reaction and Western blotting were used to measure the expression levels of TERT, and a scratch assay was performed to assess the LEC migration. New Zealand white rabbits underwent sham cataract surgery followed by an injection of adenovirus carrying shTERT into their capsule bag. The intraocular pressure and anterior segment inflammation were evaluated on certain days, and EMT markers (α-SMA and E-cadherin) were evaluated by Western blotting and immunofluorescence. The telomerase activity of the capsule bag was detected by ELISA. At 28 days postoperatively, haematoxylin and eosin staining of the cornea and iris and electron microscopy of the posterior capsule were performed.

RESULTS

Application of shTERT to LECs downregulated the expression levels of TERT mRNA and protein. The scratch assay results showed a decrease in the migration of LECs in the shTERT group. In vivo, shTERT decreased PCO formation after cataract surgery in rabbits and downregulated the expression of EMT markers, as determined by Western blotting and immunofluorescence. In addition, telomerase activity was suppressed in the capsule bag. Despite slight inflammation in the iris, histologic results revealed no toxic effects in the cornea and iris.

CONCLUSION

TERT silencing effectively reduces the migration and proliferation of LECs and the formation of PCO. Our findings suggest that TERT silencing may be a potential preventive strategy for PCO.

Senescence-associated transcriptional derepression in subtelomeres is determined in a chromosome-end-specific manner

Aging is a continuous process leading to physiological deterioration with age. One of the factors contributing to aging is telomere shortening, causing alterations in the protein protective complex named shelterin and replicative senescence. Here, we address the question of the link between this telomere shortening and the transcriptional changes occurring in senescent cells. We found that in replicative senescent cells, the genes whose expression escaped repression are enriched in subtelomeres. The shelterin protein TRF2 and the nuclear lamina factor Lamin B1, both downregulated in senescent cells, are involved in the regulation of some but not all of these subtelomeric genes, suggesting complex mechanisms of transcriptional regulation. Indeed, the subtelomeres containing these derepressed genes are enriched in factors of polycomb repression (EZH2 and H3K27me3), insulation (CTCF and MAZ), and cohesion (RAD21 and SMC3) while being associated with the open A-type chromatin compartment. These findings unveil that the subtelomere transcriptome associated with senescence is determined in a chromosome-end-specific manner according to the type of higher-order chromatin structure.

Post-Transcriptional and Post-Translational Modifications in Telomerase Biogenesis and Recruitment to Telomeres

Telomere length is associated with the proliferative potential of cells. Telomerase is an enzyme that elongates telomeres throughout the entire lifespan of an organism in stem cells, germ cells, and cells of constantly renewed tissues. It is activated during cellular division, including regeneration and immune responses. The biogenesis of telomerase components and their assembly and functional localization to the telomere is a complex system regulated at multiple levels, where each step must be tuned to the cellular requirements. Any defect in the function or localization of the components of the telomerase biogenesis and functional system will affect the maintenance of telomere length, which is critical to the processes of regeneration, immune response, embryonic development, and cancer progression. An understanding of the regulatory mechanisms of telomerase biogenesis and activity is necessary for the development of approaches toward manipulating telomerase to influence these processes. The present review focuses on the molecular mechanisms involved in the major steps of telomerase regulation and the role of post-transcriptional and post-translational modifications in telomerase biogenesis and function in yeast and vertebrates.

Telomerase-mediated immortalization of human vaginal wall fibroblasts derived from patients with pelvic organ prolapse

BACKGROUND

Extracellular matrix (ECM) remodeling is the most important pathomechanism of pelvic organ prolapse (POP). Fibroblasts are the key to ECM regulation. The passaging capacity of human vaginal wall fibroblasts (hVWFs) is limited in vitro . Here, we aimed to immortalize hVWFs through the introduction of human telomerase reverse transcriptase (hTERT).

METHODS

Primary cells were derived from the vaginal wall tissue of patients with POP. Cellular senescence was detected via senescence-associated β-galactosidase staining. We employed a lentiviral transfection vector to stably express hTERT in hVWFs at passage 3, generating immortalized hVWFs (i-hVWFs). We then assessed cellular proliferation via the CCK-8 and EdU assays as well as cellular migration via wound healing assays. G-banded chromosome karyotypic analysis was performed to evaluate chromosomal karyotype stability. Finally, cellular tumorigenesis capacity was assessed in nude mice. A two-tailed Student's t test was used to compare differences between the two groups.

RESULTS

Our results showed that senescence of primary hVWFs significantly increased from passage seven. From passage 11, hVWFs showed a significantly higher senescence percentage than i-hVWFs. During the continuous passage, i-hVWFs presented stability in proliferation, migration capacity, expression of ECM regulation-related genes, and chromosome karyotype. In vivo tumorigenesis was absent in i-hVWFs.

CONCLUSIONS

The senescence of hVWFs significantly increased from the seventh passage, and we successfully used hTERT to immortalize hVWFs derived from patients with POP. Studies on POP that require a long-lived hVWF line will benefit from our technique.

METTL3 alleviates D-gal-induced renal tubular epithelial cellular senescence via promoting miR-181a maturation

Methyltransferase-like protein 3 (METTL3) mediated N6-Methyladenosine (m⁶A) modification has been implicated in many physiological and pathological processes. However, its function and mechanism in kidney aging are not entirely clear. Here, we investigated changes in m⁶A levels of aging kidneys and the role of METTL3 in senescent renal tubular epithelial cells and its potential mechanisms. First, we used the naturally aged mouse model and the D-galactose (D-gal)-induced aged mouse model. Dot blot and m⁶A RNA methylation quantification showed significantly decreased m⁶A levels in both models. In addition, we observed that METTL3 was down-regulated in D-gal-induced senescent human renal tubular epithelial cell line (HK-2). METTL3 reduction was associated with senescence-related phenotypes of HK-2 cells. We also found that miR-181a-5p attenuated HK-2 senescence by targeting the NF-κB pathway. Moreover, METTL3 was able to promote the maturation of miR-181a-5p and then inhibited the expression of NF-κB and IL-1α. Taken together, we demonstrate that the METTL3/miR-181a-5p/NF-κB axis counteracts HK-2 senescence. Our results suggest that METTL3 may be a novel biomarker and a potential therapy target for kidney aging.

Triple signal amplification strategy for ultrasensitive in situ imaging of intracellular telomerase RNA

Abnormal upregulation of telomerase RNA (TR) is a hallmark event at various stages of tumor progression, providing a universal marker for early diagnosis of cancer. Here, we have developed a triple signal amplification strategy for in situ visualization of TR in living cells, which sequentially incorporated the target-initiated strand displacement circuit, multidirectional rolling circle amplification (RCA), and Mg²⁺ DNAzyme-mediated amplification. All oligonucleotide probes and cofactors were transfected into cells in one go, and then escaped from lysosomes successfully. Owing to the specific base pairing, the amplification cascades could only be triggered by TR and performed as programmed, resulting in a satisfactory signal-to-background ratio. Especially, the netlike DNA structure generated by RCA encapsulated high concentrations of DNAzyme and substrates (FQS) in a local region, thereby improving the reaction efficiency and kinetics of the third amplification cycle. Under optimal conditions, the proposed method exhibited ultrasensitive detection of TR mimic with a detection limit at pM level. Most importantly, after transfection with the proposed sensing platform, tumor cells can be easily distinguished from normal cells based on TR abundance-related fluorescence signal, providing a new insight into initial cancer screening.

Functional genomics for curation of variants in telomere biology disorder associated genes: A systematic review

PURPOSE

Patients with an underlying telomere biology disorder (TBD) have variable clinical presentations, and they can be challenging to diagnose clinically. A genomic diagnosis for patients presenting with TBD is vital for optimal treatment. Unfortunately, many variants identified during diagnostic testing are variants of uncertain significance. This complicates management decisions, delays treatment, and risks nonuptake of potentially curative therapies. Improved application of functional genomic evidence may reduce variants of uncertain significance classifications.

METHODS

We systematically searched the literature for published functional assays interrogating TBD gene variants. When possible, established likely benign/benign and likely pathogenic/pathogenic variants were used to estimate the assay sensitivity, specificity, positive predictive value, negative predictive value, and odds of pathogenicity.

RESULTS

In total, 3131 articles were screened and 151 met inclusion criteria. Sufficient data to enable a PS3/BS3 recommendation were available for TERT variants only. We recommend that PS3 and BS3 can be applied at a moderate and supportive level, respectively. PS3/BS3 application was limited by a lack of assay standardization and limited inclusion of benign variants.

CONCLUSION

Further assay standardization and assessment of benign variants are required for optimal use of the PS3/BS3 criterion for TBD gene variant classification.

Links between telomere dysfunction and hallmarks of aging

Aging is characterized by the gradual loss of physiological integrity, leading to impaired function and increased risk of death. This deterioration is the main risk factor for the great majority of chronic diseases, which account for most of the morbidity, death and medical expenses. The hallmarks of aging comprise diverse molecular mechanisms and cell systems, which are interrelated and coordinated to drive the aging process. This review focuses on telomere to analyze the interrelationships between telomere dysfunction and other aging hallmarks and their relative contributions to the initiation and progression of age-related diseases (such as neurodegeneration, cardiovascular disease, and cancer), which will contribute to determine drug targets, improve human health in the aging process with minimal side effects and provide information for the prevention and treatment of age-related diseases.

Cellular Senescence as a Brake or Accelerator for Oncogenic Transformation and Role in Lymphatic Metastasis

Cellular senescence-the irreversible cell cycle arrest driven by a variety of mechanisms and, more specifically, the senescence-associated secretory phenotype (SASP)-is an important area of research in the context of different age-related diseases, such as cardiovascular disease and cancer. SASP factors play both beneficial and detrimental roles in age-related disease progression depending on the source of the SASPs, the target cells, and the microenvironment. The impact of senescence and the SASP on different cell types, the immune system, and the vascular system has been widely discussed. However, the impact of replicative or stress-induced senescence on lymphatic biology and pathological lymphangiogenesis remains underexplored. The lymphatic system plays a crucial role in the maintenance of body fluid homeostasis and immune surveillance. The perturbation of lymphatic function can hamper normal physiological function. Natural aging or stress-induced premature aging influences the lymphatic vessel structure and function, which significantly affect the role of lymphatics in tumor dissemination and metastasis. In this review, we focus on the role of senescence on lymphatic pathobiology, its impact on cancer, and potential therapeutic interventions to manipulate the aged or senescent lymphatic system for disease management.

Functional T cells are capable of supernumerary cell division and longevity

Differentiated somatic mammalian cells putatively exhibit species-specific division limits that impede cancer but may constrain lifespans1-3. To provide immunity, transiently stimulated CD8+ T cells undergo unusually rapid bursts of numerous cell divisions, and then form quiescent long-lived memory cells that remain poised to reproliferate following subsequent immunological challenges. Here we addressed whether T cells are intrinsically constrained by chronological or cell-division limits. We activated mouse T cells in vivo using acute heterologous prime-boost-boost vaccinations4, transferred expanded cells to new mice, and then repeated this process iteratively. Over 10 years (greatly exceeding the mouse lifespan)5 and 51 successive immunizations, T cells remained competent to respond to vaccination. Cells required sufficient rest between stimulation events. Despite demonstrating the potential to expand the starting population at least 1040-fold, cells did not show loss of proliferation control and results were not due to contamination with young cells. Persistent stimulation by chronic infections or cancer can cause T cell proliferative senescence, functional exhaustion and death6. We found that although iterative acute stimulations also induced sustained expression and epigenetic remodelling of common exhaustion markers (including PD1, which is also known as PDCD1, and TOX) in the cells, they could still proliferate, execute antimicrobial functions and form quiescent memory cells. These observations provide a model to better understand memory cell differentiation, exhaustion, cancer and ageing, and show that functionally competent T cells can retain the potential for extraordinary population expansion and longevity well beyond their organismal lifespan.

Senescent cells and SASP in cancer microenvironment: New approaches in cancer therapy

Cellular senescence was first described as a state characterized by telomere shortening, resulting in limiting cell proliferation in aging. Apart from this type of senescence, which is called replicative senescence, other senescence types occur after exposure to different stress factors. One of these types of senescence induced after adjuvant therapy (chemotherapy and radiotherapy) is called therapy-induced senescence. The treatment with chemotherapeutics induces cellular senescence in normal and cancer cells in the tumor microenvironment. Thus therapy-induced senescence in the cancer microenvironment is accepted one of the drivers of tumor progression. Recent studies have revealed that senescence-associated secretory phenotype induction has roles in pathological processes such as inducing epithelial-mesenchymal transition and promoting tumor vascularization. Thus senolytic drugs that specifically kill senescent cells and senomorphic drugs that inhibit the secretory activity of senescent cells are seen as a new approach in cancer treatment. Developing and discovering new senotherapeutic agents targeting senescent cells is also gaining importance. In this review, we attempt to summarize the signaling pathways regarding the metabolism, cell morphology, and organelles of the senescent cell. Furthermore, we also reviewed the effects of SASP in the cancer microenvironment and the senotherapeutics that have the potential to be used as adjuvant therapy in cancer treatment.

Genetics of human telomere biology disorders

Telomeres are specialized nucleoprotein structures at the ends of linear chromosomes that prevent the activation of DNA damage response and repair pathways. Numerous factors localize at telomeres to regulate their length, structure and function, to avert replicative senescence or genome instability and cell death. In humans, Mendelian defects in several of these factors can result in abnormally short or dysfunctional telomeres, causing a group of rare heterogeneous premature-ageing diseases, termed telomeropathies, short-telomere syndromes or telomere biology disorders (TBDs). Here, we review the TBD-causing genes identified so far and describe their main functions associated with telomere biology. We present molecular aspects of TBDs, including genetic anticipation, phenocopy, incomplete penetrance and somatic genetic rescue, which underlie the complexity of these diseases. We also discuss the implications of phenotypic and genetic features of TBDs on fundamental aspects related to human telomere biology, ageing and cancer, as well as on diagnostic, therapeutic and clinical approaches.

Cell Immortalization: In Vivo Molecular Bases and In Vitro Techniques for Obtention

Somatic human cells can divide a finite number of times, a phenomenon known as the Hayflick limit. It is based on the progressive erosion of the telomeric ends each time the cell completes a replicative cycle. Given this problem, researchers need cell lines that do not enter the senescence phase after a certain number of divisions. In this way, more lasting studies can be carried out over time and avoid the tedious work involved in performing cell passes to fresh media. However, some cells have a high replicative potential, such as embryonic stem cells and cancer cells. To accomplish this, these cells express the enzyme telomerase or activate the mechanisms of alternative telomere elongation, which favors the maintenance of the length of their stable telomeres. Researchers have been able to develop cell immortalization technology by studying the cellular and molecular bases of both mechanisms and the genes involved in the control of the cell cycle. Through it, cells with infinite replicative capacity are obtained. To obtain them, viral oncogenes/oncoproteins, myc genes, ectopic expression of telomerase, and the manipulation of genes that regulate the cell cycle, such as p53 and Rb, have been used.

Derivation of the Immortalized Cell Line UM51-PrePodo-hTERT and Its Responsiveness to Angiotensin II and Activation of the RAAS Pathway

Recent demographic studies predict there will be a considerable increase in the number of elderly people within the next few decades. Aging has been recognized as one of the main risk factors for the world's most prevalent diseases such as neurodegenerative disorders, cancer, cardiovascular disease, and metabolic diseases. During the process of aging, a gradual loss of tissue volume and organ function is observed, which is partially caused by replicative senescence. The capacity of cellular proliferation and replicative senescence is tightly regulated by their telomere length. When telomere length is critically shortened with progressive cell division, cells become proliferatively arrested, and DNA damage response and cellular senescence are triggered, whereupon the "Hayflick limit" is attained at this stage. Podocytes are a cell type found in the kidney glomerulus where they have major roles in blood filtration. Mature podocytes are terminal differentiated cells that are unable to undergo cell division in vivo. For this reason, the establishment of primary podocyte cell cultures has been very challenging. In our present study, we present the successful immortalization of a human podocyte progenitor cell line, of which the primary cells were isolated directly from the urine of a 51-year-old male. The immortalized cell line was cultured over the course of one year (~100 passages) with high proliferation capacity, endowed with contact inhibition and P53 expression. Furthermore, by immunofluorescence-based expression and quantitative real-time PCR for the podocyte markers CD2AP, LMX1B, NPHS1, SYNPO and WT1, we confirmed the differentiation capacity of the immortalized cells. Finally, we evaluated and confirmed the responsiveness of the immortalized cells on the main mediator angiotensin II (ANGII) of the renin-angiotensin system (RAAS). In conclusion, we have shown that it is possible to bypass cellular replicative senescence (Hayflick limit) by TERT-driven immortalization of human urine-derived pre-podocyte cells from a 51-year-old African male.

TERT promoter mutations and methylation for telomerase activation in urothelial carcinomas: New mechanistic insights and clinical significance

Telomerase, an RNA-dependent DNA polymerase synthesizing telomeric TTAGGG sequences, is primarily silent in normal human urothelial cells (NHUCs), but widely activated in urothelial cell-derived carcinomas or urothelial carcinomas (UCs) including UC of the bladder (UCB) and upper track UC (UTUC). Telomerase activation for telomere maintenance is required for the UC development and progression, and the key underlying mechanism is the transcriptional de-repression of the telomerase reverse transcriptase (TERT), a gene encoding the rate-limiting, telomerase catalytic component. Recent mechanistic explorations have revealed important roles for TERT promoter mutations and aberrant methylation in activation of TERT transcription and telomerase in UCs. Moreover, these TERT-featured genomic and epigenetic alterations have been evaluated for their usefulness in non-invasive UC diagnostics, recurrence monitoring, outcome prediction and response to treatments such as immunotherapy. Importantly, the detection of the mutated TERT promoter and TERT mRNA as urinary biomarkers holds great promise for urine-based UC liquid biopsy. In the present article, we review recent mechanistic insights into altered TERT promoter-mediated telomerase activation in UCs and discuss potential clinical implications. Specifically, we compare differences in senescence and transformation between NHUCs and other types of epithelial cells, address the interaction between TERT promoter mutations and other factors to affect UC progression and outcomes, evaluate the impact of TERT promoter mutations and TERT-mediated activation of human endogenous retrovirus genes on UC immunotherapy including Bacillus Calmette-Guérin therapy and immune checkpoint inhibitors. Finally, we suggest the standardization of a TERT assay and evaluation system for UC clinical practice.