Regulation of growth arrest in senescence: Telomere damage is not the end of the story

Accumulation of senescent cells in the adrenal gland induces hypersecretion of corticosterone via IL1β secretion

Aging progresses through the interaction of metabolic processes, including changes in the immune and endocrine systems. Glucocorticoids (GCs), which are regulated by the hypothalamic-pituitary-adrenal (HPA) axis, play an important role in regulating metabolism and immune responses. However, the age-related changes in the secretion mechanisms of GCs remain elusive. Here, we found that corticosterone (CORT) secretion follows a circadian rhythm in young mice, whereas it oversecreted throughout the day in aged mice >18 months old, resulting in the disappearance of diurnal variation. Furthermore, senescent cells progressively accumulated in the zF of the adrenal gland as mice aged beyond 18 months. This accumulation was accompanied by an increase in the number of Ad4BP/SF1 (SF1), a key transcription factor, strongly expressing cells (SF1-high positive: HP). Removal of senescent cells with senolytics, dasatinib, and quercetin resulted in the reduction of the number of SF1-HP cells and recovery of CORT diurnal oscillation in 24-month-old mice. Similarly, administration of a neutralizing antibody against IL1β, which was found to be strongly expressed in the adrenocortical cells of the zF, resulted in a marked decrease in SF1-HP cells and restoration of the CORT circadian rhythm. Our findings suggest that the disappearance of CORT diurnal oscillation is a characteristic of aging individuals and is caused by the secretion of IL1β, one of the SASPs, from senescent cells that accumulate in the zF of the adrenal cortex. These findings provide a novel insight into aging. Age-related hypersecretory GCs could be a potential therapeutic target for aging-related diseases.

From Crypts to Cancer: A Holistic Perspective on Colorectal Carcinogenesis and Therapeutic Strategies

Colorectal cancer (CRC) represents a significant global health burden, with high incidence and mortality rates worldwide. Recent progress in research highlights the distinct clinical and molecular characteristics of colon versus rectal cancers, underscoring tumor location's importance in treatment approaches. This article provides a comprehensive review of our current understanding of CRC epidemiology, risk factors, molecular pathogenesis, and management strategies. We also present the intricate cellular architecture of colonic crypts and their roles in intestinal homeostasis. Colorectal carcinogenesis multistep processes are also described, covering the conventional adenoma-carcinoma sequence, alternative serrated pathways, and the influential Vogelstein model, which proposes sequential APC, KRAS, and TP53 alterations as drivers. The consensus molecular CRC subtypes (CMS1-CMS4) are examined, shedding light on disease heterogeneity and personalized therapy implications.

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.

Cellular senescence in skin-related research: Targeted signaling pathways and naturally occurring therapeutic agents

Despite the growing interest by researchers into cellular senescence, a hallmark of cellular aging, its role in human skin remains equivocal. The skin is the largest and most accessible human organ, reacting to the external and internal environment. Hence, it is an organ of choice to investigate cellular senescence and to target root-cause aging processes using senolytic and senomorphic agents, including naturally occurring plant-based derivatives. This review presents different aspects of skin cellular senescence, from physiology to pathology and signaling pathways. Cellular senescence can have both beneficial and detrimental effects on the skin, indicating that both prosenescent and antisenescent therapies may be desirable, based on the context. Knowledge of molecular mechanisms involved in skin cellular senescence may provide meaningful insights for developing effective therapeutics for senescence-related skin disorders, such as wound healing and cosmetic skin aging changes.

Exposure to 10 Hz Pulsed Magnetic Fields Do Not Induce Cellular Senescence in Human Fetal Lung Fibroblasts

Rapid population aging has led to a global burden of late-life diseases. As the largest risk factor for a multitude of age-related diseases, aging is not only the result of genotype but also closely related to external factors. With the rapid expansion in the usage of electromagnetic fields (EMFs), the effect of EMFs on aging has also attracted attention. Cells are the basic unit of organs and body tissues, and cellular senescence plays an important role in the aging process. The effect of EMFs on cellular senescence has been investigated in a few studies, but the information is limited, and the results are inconsistent; thus, further investigation is required. In this study, we investigated the effect of 10 Hz pulsed magnetic fields (MFs) on cellular senescence in a 2BS cell line, isolated from human fetal lung fibroblasts, and found that intermittent (1 d on/1 d off) exposure to 10 Hz pulsed MFs at 1.0 mT for 2 weeks induced DNA damage, but no other significant phenotype of cellular senescence in 2BS cells.

Primary high-grade serous ovarian cancer cells are sensitive to senescence induced by carboplatin and paclitaxel in vitro

BACKGROUND

Various types of normal and cancer cells undergo senescence in response to carboplatin and paclitaxel, which are considered the gold standard treatments in ovarian cancer management. Surprisingly, the effect of these drugs on ovarian cancer cell senescence remained unknown.

METHODS

The experiments were conducted on primary high-grade serous ovarian cancer cells. Molecular markers of senescence were evaluated using cytochemistry and immunofluorescence. Cell cycle distribution was analyzed using flow cytometry. Expression of cyclins and signaling pathways was tested using western blot. Telomere length and telomerase activity were measured using qPCR, and the colocalization of telomeres with DNA damage foci using immuno-FISH. Oxidative stress-related parameters were quantified using appropriate fluorescence probes. Production of cancerogenic agents was analyzed using qPCR and ELISA.

RESULTS

Carboplatin applied with paclitaxel induces senescence of ovarian cancer cells in vitro. This activity was reflected by permanent G2/M growth arrest, a high fraction of cells expressing senescence biomarkers (SA-β-Gal and γ-H2A.X), upregulated expression of p16, p21, and p53 cell cycle inhibitors, and decreased expression of cyclin B1. Neither telomere length nor telomerase activity changed in the senescent cells, and the majority of DNA damage was localized outside telomeres. Moreover, drug-treated cancer cells exhibited increased production of STAT3 protein, overproduced superoxide and peroxides, and increased mitochondrial mass. They were also characterized by upregulated ANG1, CCL11, IL-6, PDGF-D, TIMP-3, TSP-1, and TGF-β1 at the mRNA and/or protein level.

CONCLUSIONS

Our findings imply that conventional chemotherapy may elicit senescence in ovarian cancer cells, which may translate to the development of a cancer-promoting phenotype, despite the inability of these cells to divide.

The role of senescence in the pathogenesis of atrial fibrillation: A target process for health improvement and drug development

Cellular senescence is a state of growth arrest that occurs after cells encounter various stresses. Senescence contributes to tumour suppression, embryonic development, and wound healing. It impacts on the pathology of various diseases by secreting inflammatory chemokines, immune modulators and other bioactive factors. These secretory biosignatures ultimately cause inflammation, tissue fibrosis, immunosenescence and many ageing-related diseases such as atrial fibrillation (AF). Because the molecular mechanisms underpinning AF development remain unclear, current treatments are suboptimal and have serious side effects. In this review, we summarize recent results describing the role of senescence in AF. We propose that senescence factors induce AF and have a causative role. Hence, targeting senescence and its secretory phenotype may attenuate AF.

An in vitro senescence model of gingival epithelial cell induced by hydrogen peroxide treatment

Gingival tissue shows progressive changes with aging and an in vitro model of gingival tissue could be useful in understanding age-associated oral diseases. The present study aims to establish a hydrogen peroxide (H₂O₂) treatment model to induce aging in human gingival epithelial cells. In addition, fisetin, a flavonoid component studied for the anti-aging property is used to examine if it could reverse the induced senescence. Primary human gingival epithelial progenitor (HGEPp) cells were cultured and treated with different concentrations of H₂O₂. A cell vitality and morphology, senescence-associated beta-galactosidase (SA-β-gal) staining, mRNA and protein expression analysis of known senescence markers p16, p21, and p53, and cell cycle assay were performed. The cells showed dose-dependent changes in vitality and morphology, SA-β-gal staining, relative mRNA and protein expression, and cell cycle assay after H₂O₂ treatment. Based on these results, 400 μM H₂O₂ was considered as an optimal concentration to induce senescence. Treatment of senescence-induced cells with fisetin downregulated all the senescence markers used in this study. In conclusion, a senescence model of gingival epithelial cells induced by hydrogen peroxide treatment was established which could be employed to study age-related periodontal diseases.

Telomere Length in Metaphase Chromosomes of Human Triploid Zygotes

The human lifespan is strongly influenced by telomere length (TL) which is defined in a zygote—when two highly specialised haploid cells form a new diploid organism. Although TL is a variable parameter, it fluctuates in a limited range. We aimed to establish the determining factors of TL in chromosomes of maternal and paternal origin in human triploid zygotes. Using Q-FISH, we examined TL in the metaphase chromosomes of 28 human triploid zygotes obtained from 22 couples. The chromosomes’ parental origin was identified immunocytochemically through weak DNA methylation and strong hydroxymethylation in the sperm-derived (paternal) chromosomes versus strong DNA methylation and weak hydroxymethylation in the oocyte-derived (maternal) ones. In 24 zygotes, one maternal and two paternal chromosome sets were identified, while the four remaining zygotes contained one paternal and two maternal sets. For each zygote, we compared mean relative TLs between parental chromosomes, identifying a significant difference in favour of the paternal chromosomes, which attests to a certain “imprinting” of these regions. Mean relative TLs in paternal or maternal chromosomes did not correlate with the respective parent’s age. Similarly, no correlation was observed between the mean relative TL and sperm quality parameters: concentration, progressive motility and normal morphology. Based on the comparison of TLs in chromosomes inherited from a single individual’s gametes with those in chromosomes inherited from different individuals’ gametes, we compared intraindividual (intercellular) and interindividual variability, obtaining significance in favour of the latter and thus validating the role of heredity in determining TL in zygotes. A comparison of the interchromatid TL differences across the chromosomes from sets of different parental origin with those from PHA-stimulated lymphocytes showed an absence of a significant difference between the maternal and paternal sets but a significant excess over the lymphocytes. Therefore, interchromatid TL differences are more pronounced in zygotes than in lymphocytes. To summarise, TL in human zygotes is determined both by heredity and parental origin; the input of other factors is possible within the individual’s reaction norm.

Nuclear localization of p65 reverses therapy-induced senescence

Senescence is the arrest of cell proliferation and is a tumor suppressor phenomenon. In a previous study, we have shown that therapy-induced senescence of glioblastoma multiforme (GBM) cells can prevent relapse of GBM tumors. Here, we demonstrate that ciprofloxacin-induced senescence in glioma-derived cell lines and primary glioma cultures is defined by SA-β-gal positivity, a senescence-associated secretory phenotype (SASP), a giant cell (GC) phenotype, increased levels of reactive oxygen species (ROS), γ-H2AX and a senescence-associated gene expression signature, and has three stages of senescence -initiation, pseudo-senescence and permanent senescence. Ciprofloxacin withdrawal during initiation and pseudo-senescence reinitiated proliferation in vitro and tumor formation in vivo Importantly, prolonged treatment with ciprofloxacin induced permanent senescence that failed to reverse following ciprofloxacin withdrawal. RNA-seq revealed downregulation of the p65 (RELA) transcription network, as well as incremental expression of SMAD pathway genes from initiation to permanent senescence. Ciprofloxacin withdrawal during initiation and pseudo-senescence, but not permanent senescence, increased the nuclear localization of p65 and escape from ciprofloxacin-induced senescence. By contrast, permanently senescent cells showed loss of nuclear p65 and increased apoptosis. Pharmacological inhibition or genetic knockdown of p65 upheld senescence in vitro and inhibited tumor formation in vivo Our study demonstrates that levels of nuclear p65 define the window of reversibility of therapy-induced senescence and that permanent senescence can be induced in GBM cells when the use of senotherapeutics is coupled with p65 inhibitors.

Pancreatic β-Cell Senescence: Mechanisms and Association with Diabetes

Senescence occurs as a part of the cellular response to different stressors. With increasing age, continuous exposure to stressors leads to age-induced senescence. Pancreatic β-cell proliferation and glucose homeostasis also decrease with age, which results in a decrease in β cell mass and, eventually, the possible development of diabetes. This process is mediated through impaired cell cycle regulators, along with specific increases in cell cycle inhibitors, telomere shortening, and defective DNA repair mechanisms. Diabetes contributes to β-cell senescence through hyperglycaemia, dyslipidaemia, oxidative stress, and inflammation. β cells isolated from patients with Type 2 diabetes mellitus have been shown to have senescence markers, such as senescence-associated secretory phenotype genes and β-galactosidase. In this paper, the authors discuss the mechanisms of cellular senescence, how senescence is impacted by the diabetic microenvironment, and the possible mechanisms and factors contributing to β-cell senescence.

mTOR as a senescence manipulation target: A forked road

Cellular senescence, cancer and aging are highly interconnected. Among many important molecular machines that lie at the intersection of this triad, the mechanistic (formerly mammalian) target of rapamycin (mTOR) is a central regulator of cell metabolism, proliferation, and survival. The mTOR signaling cascade is essential to maintain cellular homeostasis in normal biological processes or in response to stress, and its dysregulation is implicated in the progression of many disorders, including age-associated diseases. Accordingly, the pharmacological implications of mTOR inhibition using rapamycin or others rapalogs span the treatment of various human diseases from immune disorders to cancer. Importantly, rapamycin is one of the only known pan-species drugs that can extend lifespan. The molecular and cellular mechanisms explaining the phenotypic consequences of mTOR are vast and heavily studied. In this review, we will focus on the potential role of mTOR in the context of cellular senescence, a tumor suppressor mechanism and a pillar of aging. We will explore the link between senescence, autophagy and mTOR and discuss the opportunities to exploit senescence-associated mTOR functions to manipulate senescence phenotypes in age-associated diseases and cancer treatment.

Cellular senescence: Silent operator and therapeutic target in cancer

The process of carcinogenesis and its progression involves an intricate interplay between a number of signaling networks, metabolic pathways and the microenvironment. These include an alteration in the cellular redox metabolism and deregulation of cell cycle checkpoints. Similar to the dichotomy of redox signaling in cancer cell fate and state determination, a diverging effect of an irreversible cell cycle arrest or senescence on carcinogenesis has been demonstrated. In this regard, while overwhelming oxidative stress has a damaging effect on tissue architecture and organ function and promotes death execution, a mild "pro-oxidant" environment is conducive for cell proliferation, growth and survival. Similarly, cellular senescence has been shown to elicit both a tumor suppressor and an oncogenic effect in a context-dependent manner. Notably, there appears to be a crosstalk between these two critical regulators of cell fate and state, particularly from the standpoint of the divergent effects on processes that promote or abate carcinogenesis. This review aims to provide an overview of these overarching themes and attempts to highlight critical intersection nodes, which are emerging as potential diagnostic and/or therapeutic targets for novel anticancer strategies.

Decreased expression of TERT and telomeric proteins as human ovaries age may cause telomere shortening

OBJECTIVE

Telomeres are repetitive sequences localized at the ends of eukaryotic chromosomes comprising noncoding DNA and telomere-binding proteins. TRF1 and TRF2 both bind to the double-stranded telomeric DNA to regulate its length throughout the lifespan of eukaryotic cells. POT1 interacts with single-stranded telomeric DNA and contributes to protecting genomic integrity. Previous studies have shown that telomeres gradually shorten as ovaries age, coinciding with fertility loss. However, the molecular background of telomere shortening with ovarian aging is not fully understood.

METHODS

The present study aimed to determine the spatial and temporal expression levels of the TERT, TRF1, TRF2, and POT1 proteins in different groups of human ovaries: fetal (n = 11), early postnatal (n = 10), premenopausal (n = 12), and postmenopausal (n = 14). Also, the relative telomere signal intensity of each group was measured using the Q-FISH method.

RESULTS

We found that the telomere signal intensities decreased evenly and significantly from fetal to postmenopausal groups (P < 0.05). The TERT, TRF1, TRF2, and POT1 proteins were localized in the cytoplasmic and nuclear regions of the oocytes, granulosa and stromal cells. Furthermore, the expression levels of these proteins reduced significantly from fetal to postmenopausal groups (P < 0.05).

CONCLUSION

These findings suggest that decreased TERT and telomere-binding protein expression may underlie the telomere shortening of ovaries with age, which may be associated with female fertility loss. Further investigations are required to elicit the molecular mechanisms regulating the gradual decrease in the expression of TERT and telomere-binding proteins in human oocytes and granulosa cells during ovarian aging.

Cell Senescence: A Nonnegligible Cell State under Survival Stress in Pathology of Intervertebral Disc Degeneration

The intervertebral disc degeneration (IDD) with increasing aging mainly manifests as low back pain (LBP) accompanied with a loss of physical ability. These pathological processes can be preliminarily interpreted as a series of changes at cellular level. In addition to cell death, disc cells enter into the stagnation with dysfunction and deteriorate tissue microenvironment in degenerative discs, which is recognized as cell senescence. During aging, many intrinsic and extrinsic factors have been proved to have strong connections with these cellular senescence phenomena. Growing evidences of these connections require us to gather up critical cues from potential risk factors to pathogenesis and relative interventions for retarding cell senescence and attenuating degenerative changes. In this paper, we try to clarify another important cell state apart from cell death in IDD and discuss senescence-associated changes in cells and extracellular microenvironment. Then, we emphasize the role of oxidative stress and epigenomic perturbations in linking risk factors to cell senescence in the onset of IDD. Further, we summarize the current interventions targeting senescent cells that may exert the benefits of antidegeneration in IDD.

Tree age did not affect the leaf anatomical structure or ultrastructure of Platycladus orientalis L. (Cupressaceae)

Tree aging is a new research area and has attracted research interest in recent years. Trees show extraordinary longevity; Platycladus orientalis L. (Cupressaceae) has a lifespan of thousands of years. Ancient trees are precious historical heritage and scientific research materials. However, tree aging and tree senescence have different definitions and are poorly understood. Since leaves are the most sensitive organ of a tree, we studied the structural response of leaves to tree age. Experiments investigating the leaf morphological structure, anatomical structure and ultrastructure were conducted in healthy P. orientalis at three different ages (ancient trees >2,000 years, 200 years < middle-aged trees <500 years, young trees <50 years) at the world’s largest planted pure forest in the Mausoleum of the Yellow Emperor, Shaanxi Province, China. Interestingly, tree age did not significantly impact leaf cellular structure. Ancient P. orientalis trees in forests older than 2,000 years still have very strong vitality, and their leaves still maintained a perfect anatomical structure and ultrastructure. Our observations provide new evidence for the unique pattern of tree aging, especially healthy aging. Understanding the relationships between leaf structure and tree age will enhance the understanding of tree aging.

Immunohistochemical Expression of p16 in Melanocytic Lesions: An Updated Review and Meta-analysis

CONTEXT

- Making an accurate diagnosis for melanocytic lesions has always been challenging for pathologists, especially when dealing with difficult-to-diagnose cases. Misdiagnosis of melanoma and melanocytic lesions in general has tremendous medical-legal implications, often leading to unnecessary and excessive use of adjunctive tests. Although molecular testing is of much interest and there is great support for its development, currently, for most melanocytic lesions, immunohistochemical studies remain the most practical method for assistance in the routine diagnosis of melanocytic lesions for the average pathologist.

OBJECTIVES

- To review the practical use of p16 immunohistochemistry for evaluating melanocytic lesions, particularly for differentiating benign from malignant tumors, and to perform a meta-analysis of primary studies evaluating p16 immunohistochemistry in melanocytic lesions.

DATA SOURCES

- A PubMed database search for literature reporting melanocytic lesions and p16 immunohistochemistry was performed. Essential information from each study (number of samples, antibody used, collection dates, overall p16 immunohistochemistry results, and general method of interpretation) was tabulated and analyzed. Examples of representative cases showing p16 immunostaining pattern are also illustrated.

CONCLUSIONS

- Incorporation of p16 immunohistochemistry for the diagnosis of melanocytic lesions is of limited use, especially for the purpose of differentiating benign from malignant lesions. Evaluation of multiple studies reveals a wide range of results. However, there appears to be some value for the use of p16 in distinguishing nodal nevi from metastatic melanoma within nodes. The method of interpretation (nuclear versus cytoplasmic staining) also appears to give differing results, as studies considering only nuclear staining appeared to show more consistent results from study to study.

Telomeres and genomic instability during early development

Genomic instability is widespread during early embryo development. Aneuploidy, mosaicism, and copy number variants (CNVs) commonly appear in human preimplantation embryos. Both age-dependent meiotic aneuploidy and age-independent mitotic aneuploidy and CNVs occur In human embryos. Telomere attrition, which contributes to genomic instability in somatic cells, also may promote genomic instability in preimplantation embryos. Telomere dynamics during gametogenesis are strikingly dimorphic between females and males. Sperm telomeres lengthen with advancing paternal age, while oocyte telomeres are among the shortest in the body. Spermatogonia express telomerase activity throughout the life of the male, while oocytes and cleavage stage embryos express low or un-measureable levels of telomerase activity. Telomere attrition in oocytes contributes to meiotic dysfunction, including spindle dysmorphologies, reduced synapsis and chiasmata, as well as delayed, arrested and fragmented embryos. Cleavage stage embryos, with such inefficient telomere reconstitution, likely undergo NHEJ, which produces anaphase lag, chromosome bridges, micronuclei, and genomic instability, including mosaicism and CNVs. Cleavage stage embryos reconstitute the short telomeres inherited from their mothers by Alternative Lengthening of Telomeres (ALT), a DNA recombination based method involving RAD 50, MRE 11, Werner and Bloom proteins, as well as telomere sister chromatid exchange. ALT robustly reconstitutes telomeres, but also predisposes to genomic instability.

Epigenetic Regulation of Skin Cells in Natural Aging and Premature Aging Diseases

Skin undergoes continuous renewal throughout an individual’s lifetime relying on stem cell functionality. However, a decline of the skin regenerative potential occurs with age. The accumulation of senescent cells over time probably reduces tissue regeneration and contributes to skin aging. Keratinocytes and dermal fibroblasts undergo senescence in response to several intrinsic or extrinsic stresses, including telomere shortening, overproduction of reactive oxygen species, diet, and sunlight exposure. Epigenetic mechanisms directly regulate skin homeostasis and regeneration, but they also mark cell senescence and the natural and pathological aging processes. Progeroid syndromes represent a group of clinical and genetically heterogeneous pathologies characterized by the accelerated aging of various tissues and organs, including skin. Skin cells from progeroid patients display molecular hallmarks that mimic those associated with naturally occurring aging. Thus, investigations on progeroid syndromes strongly contribute to disclose the causal mechanisms that underlie the aging process. In the present review, we discuss the role of epigenetic pathways in skin cell regulation during physiologic and premature aging.

miR-200a Modulates the Expression of the DNA Repair Protein OGG1 Playing a Role in Aging of Primary Human Keratinocytes

Oxidative DNA damage accumulation may induce cellular senescence. Notably, senescent cells accumulate in aged tissues and are present at the sites of age-related pathologies. Although the signaling of DNA strand breaks has been extensively studied, the role of oxidative base lesions has not fully investigated in primary human keratinocyte aging. In this study, we show that primary human keratinocytes from elderly donors are characterized by a significant accumulation of the oxidative base lesion 8-OH-dG, impairment of oxidative DNA repair, and increase of miR-200a levels. Notably, OGG1-2a, a critical enzyme for 8-OH-dG repair, is a direct target of miR-200a and its expression levels significantly decrease in aged keratinocytes. The 8-OH-dG accumulation displays a significant linear relationship with the aging biomarker p16 expression during keratinocyte senescence. Interestingly, we found that miR-200a overexpression down-modulates its putative target Bmi-1, a well-known p16 repressor, and up-regulates p16 itself. miR-200a overexpression also up-regulates the NLRP3 inflammasome and IL-1β expression. Of note, primary keratinocytes from elderly donors are characterized by NRPL3 activation and IL-1β secretion. These findings point to miR-200a as key player in primary human keratinocyte aging since it is able to reduce oxidative DNA repair activity and may induce several senescence features through p16 and IL-1β up-regulation.

Telomeres, Reproductive Aging, and Genomic Instability During Early Development

Implantation rate decreases and miscarriage rate increases with advancing maternal age. The oocyte must be the locus of reproductive aging because donation of oocytes from younger to older women abrogates the effects of aging on fecundity. Nuclear transfer experiments in a mouse model of reproductive aging show that the reproductive aging phenotype segregates with the nucleus rather than the cytoplasm. A number of factors within the nucleus have been hypothesized to mediate reproductive aging, including disruption of cohesions, reduced chiasma, aneuploidy, disrupted meiotic spindles, and DNA damage caused by chronic exposure to reactive oxygen species. We have proposed telomere attrition as a parsimonious way to explain these diverse effects of aging on oocyte function. Telomeres are repetitive sequences of DNA and associated proteins, which form a loop (t loop) at chromosome ends. Telomeres prevent the blunt end of DNA from triggering a DNA damage response. Previously, we showed that experimental telomere shortening phenocopies reproductive aging in mice. Telomere shortening causes reduced synapsis and chiasma, chromosome fusions, embryo arrest and fragmentation, and abnormal meiotic spindles. Telomere length of polar bodies predicts the fragmentation of human embryos. Telomerase, the reverse transcriptase capable of reconstituting shortened telomeres, is only minimally active in oocytes and preimplantation embryos. Intriguingly, during the first cell cycles following activation, telomeres robustly elongate via a DNA double-strand break mechanism called alternative lengthening of telomeres (ALTs). Alternative lengthening of telomere takes place even in telomerase-null mice. This mechanism of telomere elongation previously had been found only in cancer cells lacking telomerase activity. We propose that ALT elongates telomeres across generations but does so at the cost of extensive genomic instability in preimplantation embryos.

Caveolin-1 is involved in high glucose accelerated human glomerular mesangial cell senescence

BACKGROUND/AIMS

We demonstrated the role of caveolin-1 involved in high glucose (HG)-induced glomerular mesangial cells (GMCs) senescence.

METHODS

HG was used to stimulate GMCs. The telomere lengths were analyzed by Southern blot. β-Galactosidase staining was determined. The expressions of caveolin-1 and P53 proteins were determined by Western blot.

RESULTS

Treatment with high concentrations of glucose induced GMC senescence accompanied by shortened telomere length and increase of β-galactosidase staining as well as P53 protein, which was abrogated after application of caveolin-1-siRNA.

CONCLUSIONS

This study proved that HG induced cell senescence in GMCs. The caveolin-1 is involved in HG-induced mesangial cell senescence, and blocking caveolin-1 significantly reduced cell senescence. The effect of caveolin-1 is mediated by P53 pathway.

DNA damage and senescence in osteoprogenitors expressing Osx1 may cause their decrease with age

Age-related bone loss in mice results from a decrease in bone formation and an increase in cortical bone resorption. The former is accounted by a decrease in the number of postmitotic osteoblasts which synthesize the bone matrix and is thought to be the consequence of age-dependent changes in mesenchymal osteoblast progenitors. However, there are no specific markers for these progenitors, and conclusions rely on results from in vitro cultures of mixed cell populations. Moreover, the culprits of such changes remain unknown. Here, we have used Osx1-Cre;TdRFP mice in which osteoprogenitors express the TdRFP fluorescent protein. We report that the number of TdRFP-Osx1 cells, freshly isolated from the bone marrow, declines by more than 50% between 6 and 24 months of age in both female and male mice. Moreover, TdRFP-Osx1 cells from old mice exhibited markers of DNA damage and senescence, such as γH2AX foci, G1 cell cycle arrest, phosphorylation of p53, increased p21CIP1 levels, as well as increased levels of GATA4 and activation of NF-κB - two major stimulators of the senescence-associated secretory phenotype (SASP). Bone marrow stromal cells from old mice also exhibited elevated expression of SASP genes, including several pro-osteoclastogenic cytokines, and increased capacity to support osteoclast formation. These changes were greatly attenuated by the senolytic drug ABT263. Together, these findings suggest that the decline in bone mass with age is the result of intrinsic defects in osteoprogenitor cells, leading to decreased osteoblast numbers and increased support of osteoclast formation.

The impact of cerebrovascular aging on vascular cognitive impairment and dementia

As human life expectancy rises, the aged population will increase. Aging is accompanied by changes in tissue structure, often resulting in functional decline. For example, aging within blood vessels contributes to a decrease in blood flow to important organs, potentially leading to organ atrophy and loss of function. In the central nervous system, cerebral vascular aging can lead to loss of the integrity of the blood-brain barrier, eventually resulting in cognitive and sensorimotor decline. One of the major of types of cognitive dysfunction due to chronic cerebral hypoperfusion is vascular cognitive impairment and dementia (VCID). In spite of recent progress in clinical and experimental VCID research, our understanding of vascular contributions to the pathogenesis of VCID is still very limited. In this review, we summarize recent findings on VCID, with a focus on vascular age-related pathologies and their contribution to the development of this condition.

Metastatic pathways in patients with cutaneous melanoma

Metastasis represents the end product of an elaborate biological process, which is determined by a complex interplay between metastatic tumour cells, host factors and homoeostatic mechanisms. Cutaneous melanoma can metastasize haematogenously or lymphogenously. The three predominant models that endeavour to explain the patterns of melanoma progression are the stepwise spread model, the simultaneous spread model and the model of differential spread. The time course to the development of metastases differs between the different metastatic routes. There are several clinical and histopathological risk factors for the different metastatic pathways. In particular, patient sex and the anatomical location of the primary tumour influence patterns of disease progression. There is limited existing evidence regarding the relationship between tumour mutation status, other diagnostic and prognostic biomarkers and the metastatic pathways of primary cutaneous melanoma. This knowledge gap needs to be addressed to better identify patients at high risk of disease recurrence and personalize surveillance strategies.

Biomarkers of skin aging

Aging is a complex process not only influenced by inherited but also by several environmental factors. It is characterized by a progressive loss of function in multiple tissues, which leads to an increased probability of death. On the other hand, several morphological and histological changes are registered in aged skin that is mostly dependent on the cumulative exposure in environmental aging promoters, such as ultraviolet radiation. Understanding of individual pathogenesis and introduction of preventive measurements require objective assessment, i.e., the administration of biomarkers. Because of the complexity of skin aging, the exact definition of biomarkers is a major research challenge. In this article, we summarize the basic knowledge involving skin aging and its biomarkers.

Understanding the connection between platelet-activating factor, a UV-induced lipid mediator of inflammation, immune suppression and skin cancer

Lipid mediators of inflammation play important roles in several diseases including skin cancer, the most prevalent type of cancer found in the industrialized world. Ultraviolet (UV) radiation is a complete carcinogen and is the primary cause of skin cancer. UV radiation is also a potent immunosuppressive agent, and UV-induced immunosuppression is a well-known risk factor for skin cancer induction. An essential mediator in this process is the glyercophosphocholine 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine commonly referred to as platelet-activating factor (PAF). PAF is produced by keratinocytes in response to diverse stimuli and exerts its biological effects by binding to a single specific G-protein-coupled receptor (PAF-R) expressed on a variety of cells. This review will attempt to describe how this lipid mediator is involved in transmitting the immunosuppressive signal from the skin to the immune system, starting from its production by keratinocytes, to its role in activating mast cell migration in vivo, and to the mechanisms involved that ultimately lead to immune suppression. Recent findings related to its role in regulating DNA repair and activating epigenetic mechanisms, further pinpoint the importance of this bioactive lipid, which may serve as a critical molecular mediator that links the environment (UVB radiation) to the immune system and the epigenome.

Reflections on the role of senescence during development and aging

New and stimulating results have challenged the concept that cellular senescence might not be synonymous with aging. It is indisputable that during aging, senescent cell accumulation has an impact on organismal health. Nevertheless, senescent cells are now known to display physiological roles during embryonic development, during wound healing repair and as a cellular response to stress. The fact that senescence has been found in cells that did not attain their maximal round of replications, nor have metabolic alterations or DNA damage, also challenges the paradigm that senescence is cellular aging, and it is in favor of the idea that cellular senescence is a phenomenon that has a function by itself. Therefore, in order to understand this phenomenon it is important to analyze the relationship between senescence and other cellular responses that have many features in common, such as apoptosis, cancer and autophagy, particularly highlighting their role during development and adulthood.

miR-29c-3p promotes senescence of human mesenchymal stem cells by targeting CNOT6 through p53-p21 and p16-pRB pathways

Mesenchymal stem cells (MSCs) are important seed cells for tissue engineering and are promising targets for cell-based therapies. However, the replicative senescence of MSCs during in vitro culture limits their research and clinical applications. The molecular mechanisms underlying the replicative senescence of MSCs are not fully understood. Evidence suggests that miRNAs play important roles in replicative senescence. A microarray analysis found that the miR-29c-3p level was significantly increased during the MSC senescence process. In our study, we investigated the roles of miR-29c-3p in senescence of MSCs. We cultured MSCs for long periods of time, up and down-regulated the miR-29c-3p expression in MSCs, and examined the senescent phenotype changes. The over-expression of miR-29c-3p led to enhanced senescence-associated-β-galactosidase (SA-β-gal) staining, senescence associated secretory phenotype (SASP), senescence associated heterochromatic foci (SAHF), reduced proliferation ability, retarded osteogenic differentiation and corresponding changes in senescence markers, whereas the miR-29c-3p down-regulation had the opposite results. Dual-luciferase reporter assays demonstrated that CNOT6 is the target gene of miR-29c-3p. Knockdown of CNOT6 confirmed its inhibitory effects on the senescence of MSCs. In addition, Western blot results showed that both the p53-p21 and the p16-pRB pathways were activated during the miR-29c-3p-induced senescence of MSCs. In conclusion, our results demonstrate that miR-29c-3p promotes the senescence of MSCs by targeting CNOT6 through p53-p21 and p16-pRB pathways and highlight the contribution of post-transcriptional regulation to stem cell senescence.

Assessing Cell Cycle Independent Function of the CDK Inhibitor p21(CDKN¹A) in DNA Repair

The cyclin-dependent kinase (CDK) inhibitor p21(CDKN1A) is a small protein that is able to regulate many important cell functions, often independently of its activity of CDK inhibitor. In addition to cell cycle, this protein regulates cell transcription, apoptosis, cell motility, and DNA repair. In particular, p21 may participate in different DNA repair processes, like the nucleotide excision repair (NER), base excision repair (BER), and double-strand breaks (DSB) repair, because of its ability to interact with DNA repair proteins, such as proliferating cell nuclear antigen (PCNA), a master regulator of many DNA transactions. Although this role has been debated for a long time, the influence of p21 in DNA repair has been now established. However, it remain to be clarified how this role is coupled to proteasomal degradation that has been shown to occur after DNA damage. This chapter describes procedures to study p21 protein recruitment to localized DNA damage sites in the cell nucleus. In particular, we describe a technique based on local irrradiation with UV light through a polycarbonate filter with micropores; an in situ lysis procedure to detect chromatin-bound proteins by immunofluorescence; a cell fractionation procedure to study chromatin association of p21 by Western blot analysis, and p21 protein-protein interactions by an immunoprecipitation assay.

Genetics of melanoma progression: the rise and fall of cell senescence

There are many links between cell senescence and the genetics of melanoma, meaning both familial susceptibility and somatic-genetic changes in sporadic melanoma. For example, CDKN2A, the best-known melanoma susceptibility gene, encodes two effectors of cell senescence, while other familial melanoma genes are related to telomeres and their maintenance. This article aimed to analyze our current knowledge of the genetic or epigenetic driver changes necessary to generate a cutaneous metastatic melanoma, the commonest order in which these occur, and the relation of these changes to the biology and pathology of melanoma progression. Emphasis is laid on the role of cell senescence and the escape from senescence leading to cellular immortality, the ability to divide indefinitely.

Oxidative stress response and Nrf2 signaling in aging

Increasing oxidative stress, a major characteristic of aging, has been implicated in a variety of age-related pathologies. In aging, oxidant production from several sources is increased, whereas antioxidant enzymes, the primary lines of defense, are decreased. Repair systems, including the proteasomal degradation of damaged proteins, also decline. Importantly, the adaptive response to oxidative stress declines with aging. Nrf2/EpRE signaling regulates the basal and inducible expression of many antioxidant enzymes and the proteasome. Nrf2/EpRE activity is regulated at several levels, including transcription, posttranslation, and interactions with other proteins. This review summarizes current studies on age-related impairment of Nrf2/EpRE function and discusses the changes in Nrf2 regulatory mechanisms with aging.

DAMPs and influenza virus infection in ageing

Influenza A virus (IAV) is a serious global health problem worldwide due to frequent and severe outbreaks. IAV causes significant morbidity and mortality in the elderly population, due to the ineffectiveness of the vaccine and the alteration of T cell immunity with ageing. The cellular and molecular link between ageing and virus infection is unclear and it is possible that damage associated molecular patterns (DAMPs) may play a role in the raised severity and susceptibility of virus infections in the elderly. DAMPs which are released from damaged cells following activation, injury or cell death can activate the immune response through the stimulation of the inflammasome through several types of receptors found on the plasma membrane, inside endosomes after endocytosis as well as in the cytosol. In this review, the detriment in the immune system during ageing and the links between influenza virus infection and ageing will be discussed. In addition, the role of DAMPs such as HMGB1 and S100/Annexin in ageing, and the enhanced morbidity and mortality to severe influenza infection in ageing will be highlighted.

From cellular senescence to Alzheimer's disease: The role of telomere shortening

The old age population is increasing worldwide as well as age related diseases, including neurodegenerative disorders, such as Alzheimer's disease (AD), which negatively impacts on the health care systems. Aging represents per se a risk factor for AD. Thus, the study and identification of pathways within the biology of aging represent an important end point for the development of novel and effective disease-modifying drugs to treat, delay, or prevent AD. Cellular senescence and telomere shortening represent suitable and promising targets. Several studies show that cellular senescence is tightly interconnected to aging and AD, while the role of telomere dynamic and stability in AD pathogenesis is still unclear. This review will focus on the linking mechanisms between cellular senescence, telomere shortening, and AD.

Stn1 is critical for telomere maintenance and long-term viability of somatic human cells

Disruption of telomere maintenance pathways leads to accelerated entry into cellular senescence, a stable proliferative arrest that promotes aging-associated disorders in some mammals. The budding yeast CST complex, comprising Cdc13, Stn1, and Ctc1, is critical for telomere replication, length regulation, and end protection. Although mammalian homologues of CST have been identified recently, their role and function for telomere maintenance in normal somatic human cells are still incompletely understood. Here, we characterize the function of human Stn1 in cultured human fibroblasts and demonstrate its critical role in telomere replication, length regulation, and function. In the absence of high telomerase activity, shRNA-mediated knockdown of hStn1 resulted in aberrant and fragile telomeric structures, stochastic telomere attrition, increased telomere erosion rates, telomere dysfunction, and consequently accelerated entry into cellular senescence. Oxidative stress augmented the defects caused by Stn1 knockdown leading to almost immediate cessation of cell proliferation. In contrast, overexpression of hTERT suppressed some of the defects caused by hStn1 knockdown suggesting that telomerase can partially compensate for hStn1 loss. Our findings reveal a critical role for human Stn1 in telomere length maintenance and function, supporting the model that efficient replication of telomeric repeats is critical for long-term viability of normal somatic mammalian cells.

Immunohistochemical Expression of p16 and p21 in Pituitary Tissue Adjacent to Pituitary Adenoma versus Pituitary Tissue Obtained at Autopsy: Is There a Difference?

Normal pituitary tissue is frequently used for comparison with protein expression in tumor tissue, being obtained either at surgery or at autopsy. p16 and p21 proteins are cyclin-dependent kinase inhibitors, belonging to INK4 and Cip/Kip family, respectively. Their expression is increased in response to DNA damage or other cellular stressors, resulting in the activation of cell cycle checkpoints. They also play important roles in cellular senescence. The purpose of this study was to investigate differences in p16 and p21 immunohistochemical expression in normal pituitary tissue adjacent to pituitary adenoma obtained during neurosurgical procedure with pituitary tissue obtained at autopsy, from patients who died from non-endocrinological diseases. Our results show significant difference in p16 nuclear and p21 cytoplasmic immunohistochemical expression between two types of normal pituitary tissues. One of the reasons for this difference could be the age of subjects because those who underwent autopsy for a non-endocrinological disease were significantly older than subjects who underwent neurosurgery for a pituitary adenoma. Our finding that differences are probably not influenced by postmortem changes is supported by no significant correlation between postmortem interval and immunohistochemical p16 and p21 expression. The influence of the presence of a pituitary adenoma could not be evaluated in these specimens.

Cancer-targeted IL-12 controls human rhabdomyosarcoma by senescence induction and myogenic differentiation

Stimulating the immune system to attack cancer is a promising approach, even for the control of advanced cancers. Several cytokines that promote interferon-γ-dominated immune responses show antitumor activity, with interleukin 12 (IL-12) being of major importance. Here, we used an antibody-IL-12 fusion protein (NHS-IL12) that binds histones of necrotic cells to treat human sarcoma in humanized mice. Following sarcoma engraftment, NHS-IL12 therapy was combined with either engineered IL-7 (FcIL-7) or IL-2 (IL-2MAB602) for continuous cytokine bioavailability. NHS-IL12 strongly induced innate and adaptive antitumor immunity when combined with IL-7 or IL-2. NHS-IL12 therapy significantly improved survival of sarcoma-bearing mice and caused long-term remissions when combined with IL-2. NHS-IL12 induced pronounced cancer cell senescence, as documented by strong expression of senescence-associated p16^INK4a and nuclear translocation of p-HP1γ, and permanent arrest of cancer cell proliferation. In addition, this cancer immunotherapy initiated the induction of myogenic differentiation, further promoting the hypothesis that efficient antitumor immunity includes mechanisms different from cytotoxicity for efficient cancer control in vivo.

Increased expression of p21WAF1/CIP1 in kidney proximal tubules mediates fibrosis

Tissue fibrosis is a major cause of death in developed countries. It commonly occurs after either acute or chronic injury and affects diverse organs, including the heart, liver, lung, and kidney. Using the renal ablation model of chronic kidney disease, we previously found that the development of progressive renal fibrosis was dependent on p21(WAF1/Cip1) expression; the genetic knockout of the p21 gene greatly alleviated this disease. In the present study, we expanded on this observation and report that fibrosis induced by two different acute injuries to the kidney is also dependent on p21. In addition, when p21 expression was restricted only to the proximal tubule, fibrosis after injury was induced in the whole organ. One molecular fibrogenic switch we describe is transforming growth factor-β induction, which occurred in vivo and in cultured kidney cells exposed to adenovirus expressing p21. Our data suggests that fibrosis is p21 dependent and that preventing p21 induction after stress could be a novel therapeutic target.

Cellular senescence and the aging brain

Cellular senescence is a potent anti-cancer mechanism that arrests the proliferation of mitotically competent cells to prevent malignant transformation. Senescent cells accumulate with age in a variety of human and mouse tissues where they express a complex 'senescence-associated secretory phenotype' (SASP). The SASP includes many pro-inflammatory cytokines, chemokines, growth factors and proteases that have the potential to cause or exacerbate age-related pathology, both degenerative and hyperplastic. While cellular senescence in peripheral tissues has recently been linked to a number of age-related pathologies, its involvement in brain aging is just beginning to be explored. Recent data generated by several laboratories suggest that both aging and age-related neurodegenerative diseases are accompanied by an increase in SASP-expressing senescent cells of non-neuronal origin in the brain. Moreover, this increase correlates with neurodegeneration. Senescent cells in the brain could therefore constitute novel therapeutic targets for treating age-related neuropathologies.

No evidence for neo-oogenesis may link to ovarian senescence in adult monkey

Female germline or oogonial stem cells transiently residing in fetal ovaries are analogous to the spermatogonial stem cells or germline stem cells (GSCs) in adult testes where GSCs and meiosis continuously renew. Oocytes can be generated in vitro from embryonic stem cells and induced pluripotent stem cells, but the existence of GSCs and neo-oogenesis in adult mammalian ovaries is less clear. Preliminary findings of GSCs and neo-oogenesis in mice and humans have not been consistently reproducible. Monkeys provide the most relevant model of human ovarian biology. We searched for GSCs and neo-meiosis in ovaries of adult monkeys at various ages, and compared them with GSCs from adult monkey testis, which are characterized by cytoplasmic staining for the germ cell marker DAZL and nuclear expression of the proliferative markers PCNA and KI67, and pluripotency-associated genes LIN28 and SOX2, and lack of nuclear LAMIN A, a marker for cell differentiation. Early meiocytes undergo homologous pairing at prophase I distinguished by synaptonemal complex lateral filaments with telomere perinuclear distribution. By exhaustive searching using comprehensive experimental approaches, we show that proliferative GSCs and neo-meiocytes by these specific criteria were undetectable in adult mouse and monkey ovaries. However, we found proliferative nongermline somatic stem cells that do not express LAMIN A and germ cell markers in the adult ovaries, notably in the cortex and granulosa cells of growing follicles. These data support the paradigm that adult ovaries do not undergo germ cell renewal, which may contribute significantly to ovarian senescence that occurs with age.

Telomerase activation: a potential key modulator for human healthspan and longevity

The elderly population is increasing progressively. Along with this increase the number of age related diseases, such as cardiovascular, neurodegenerative diseases, metabolic impairment and cancer, is also on the rise thereby negatively impacting the burden on health care systems. Telomere shortening and dysfunction results in cellular senescence, an irreversible proliferative arrest that has been suggested to promote organismal aging and disabling age-related diseases. Given that telomerase, the enzyme responsible for maintaining telomere lengths, is not expressed at levels sufficient to prevent telomere shortening in most of our cells, telomeres progressively erode with advancing age. Telomerase activation, therefore, might serve as a viable therapeutic strategy to delay the onset of cellular senescence, tissue dysfunction and organismal decline. Here we analyze the more recent findings in telomerase activation as a potential key modulator for human healthspan and longevity.

In vitro lifespan and senescence mechanisms of human nucleus pulposus chondrocytes

BACKGROUND CONTEXT

Our previous in vivo study demonstrated that human nucleus pulposus chondrocytes (NPCs) in aging discs exhibited characteristic senescent features such as an increased senescence-associated β-galactosidase (SA-β-gal) expression, shortened telomere, and decreased telomerase activity. The replicative p53-p21-pRB pathway, rather than the stress-induced p16-pRB pathway, played a more important role in the senescence of NPCs in an in vivo condition, although there is a situation in which both the pathways can be activated simultaneously. However, the in vitro lifespan and senescence mechanisms of human NPCs remain unclear.

PURPOSE

To evaluate the underlying mechanisms of in vitro lifespan and in vitro senescence of the human NPCs and to verify whether the in vitro senescence mechanisms of the human NPC can represent the in vivo aging mechanisms of the cell.

STUDY DESIGN/SETTING

An in vitro study.

METHODS

We serially cultivated human NPCs from patients of different ages (35, 42, 55, 66, and 76 years) until the cells reached the end of their in vitro lifespan. During each subcultivation, we calculated NPCs cumulative population doubling level (PDL) and examined senescence markers (SA-β-gal, telomere length, telomerase activity, and p53, p21, pRB, and p16 expressions).

RESULTS

The cumulative PDLs of the NPCs from patients aged 35, 42 55, 66, and 76 years were 32, 29, 11, 9, and 11, respectively. The younger patients (35 and 42 years) had a higher mean of cumulative PDLs than the elderly patients did (55, 66, and 76 years; 30.5 vs. 10.3; p=.001). In addition, there was a significant, negative correlation between the cumulative PDLs and patient's age (r=-0.89; p=.04). With advancing culture passages, the NPCs irrespective of patient's age exhibited characteristic senescent features, such as an increase in SA-β-gal expression, shortening of telomeres, decrease in telomerase activity, and activation of both replicative p53-p21-pRB and stress-induced p16-pRB pathways. However, all the senescent features occurred at the earlier passages in elderly compared with younger patients.

CONCLUSIONS

The present study demonstrated that the human NPCs had a finite in vitro lifespan, which declined with host aging. The in vitro lifespan was determined by both replicative and stress-induced senescence mechanisms. The similarity in the in vitro senescent features with those apparent in the previous in vivo study suggests a possibility of the in vitro senescence mechanisms of the human NPC as a model of the in vivo aging mechanisms of the cell for future studies.

Association of TERC and OBFC1 haplotypes with mean leukocyte telomere length and risk for coronary heart disease

Objective

To replicate the associations of leukocyte telomere length (LTL) with variants at four loci and to investigate their associations with coronary heart disease (CHD) and type II diabetes (T2D), in order to examine possible causal effects of telomere maintenance machinery on disease aetiology.

Methods

Four SNPs at three loci BICD1 (rs2630578 GγC), 18q12.2 (rs2162440 GγT), and OBFC1 (rs10786775 CγG, rs11591710 AγC) were genotyped in four studies comprised of 2353 subjects out of which 1148 had CHD and 566 T2D. Three SNPs (rs12696304 CγG, rs10936601G>T and rs16847897 GγC) at the TERC locus were genotyped in these four studies, in addition to an offspring study of 765 healthy students. For all samples, LTL had been measured using a real-time PCR-based method.

Results

Only one SNP was associated with a significant effect on LTL, with the minor allele G of OBFC1 rs10786775 SNP being associated with longer LTL (β=0.029, P=0.04). No SNPs were significantly associated with CHD or T2D. For OBFC1 the haplotype carrying both rare alleles (rs10786775G and rs11591710C, haplotype frequency 0.089) was associated with lower CHD prevalence (OR: 0.77; 95% CI: 0.61–0.97; P= 0.03). The TERC haplotype GTC (rs12696304G, rs10936601T and rs16847897C, haplotype frequency 0.210) was associated with lower risk for both CHD (OR: 0.86; 95% CI: 0.75-0.99; P=0.04) and T2D (OR: 0.74; 95% CI: 0.61–0.91; P= 0.004), with no effect on LTL. Only the last association remained after adjusting for multiple testing.

Conclusion

Of reported associations, only that between the OBFC1 rs10786775 SNP and LTL was confirmed, although our study has a limited power to detect modest effects. A 2-SNP OBFC1 haplotype was associated with higher risk of CHD, and a 3-SNP TERC haplotype was associated with both higher risk of CHD and T2D. Further work is required to confirm these results and explore the mechanisms of these effects.

Ageing of trees: application of general ageing theories

The main questions posed in ageing theories are how ageing evolved and whether or not it is programmed. While these questions have not yet been clearly resolved, several groups of possible theories have been published on this topic. However, most of these theories do not consider plants, and the specific traits involved in their ageing mechanisms. The first trait covers clonality and sectoriality and the second concerns the lack of a differentiated germ line. The lack of a germ line prevents telomere shortening which can lead to the transfer of somatic mutations into sexual offspring, while sectoriality in trees causes isolation of potentially catastrophic events in one tree part, thus creating a population of more or less independent modules within one axis. The processes of population dynamics, including ageing, can act within the framework of an individual tree as well as in that of the population as a whole, although the processes involved differ and consequently result in different effects.

Increased TERC gene copy number and cells in senescence in primary sclerosing cholangitis compared to colitis and control patients

OBJECTIVE

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disorder that involves inflammatory and fibrotic changes in the bile ducts. Up to 80% of patients have concomitant inflammatory bowel disease (IBD) with colitis. PSC patients are predisposed to develop hepatobiliary, colonic and other extrahepatic malignancies, probably related to inflammatory processes that might promote carcinogenesis. Telomerase is an enzyme complex that lengthens telomeres and has enhanced expression in numerous malignancies. In this study, we evaluated the TERC gene copy number, the proportion of cells in senescence and the amount of fragmentation in the senescent state.

METHODS

Fluorescence in situ hybridization (FISH) for the TERC gene was applied to lymphocytes retrieved from PSC (N=19), colitis (N=20) and healthy control patients (N=20) to determine the TERC copy number. On the same FISH slides, cells stained with DAPI were also analyzed for senescence-associated heterochromatin foci (SAHF) status, including the number of cells with fragments and the number of SAHF fragments in each cell.

RESULTS

A higher TERC gene copy number was observed in cells from PSC patients compared to colitis and control group patients. It was also higher in the colitis than in the control group. Significantly more cells in the senescent state and more fragmentation in each cell were observed in the PSC group compared to colitis and control groups.

CONCLUSION

The TERC gene copy number and the number of cells in the senescent state were increased in PSC patients compared to the colitis and control groups. These findings are probably related to the genetic instability parameters that reflect the higher tendency of this patient group to develop malignancies.