Comparative analysis of telomere lengths and erosion with age in human epidermis and lingual epithelium

Mechanisms of Senescence and Anti-Senescence Strategies in the Skin

The skin is the layer of tissue that covers the largest part of the body in vertebrates, and its main function is to act as a protective barrier against external environmental factors, such as microorganisms, ultraviolet light and mechanical damage. Due to its important function, investigating the factors that lead to skin aging and age-related diseases, as well as understanding the biology of this process, is of high importance. Indeed, it has been reported that several external and internal stressors contribute to skin aging, similar to the aging of other tissues. Moreover, during aging, senescent cells accumulate in the skin and express senescence-associated factors, which act in a paracrine manner on neighboring healthy cells and tissues. In this review, we will present the factors that lead to skin aging and cellular senescence, as well as ways to study senescence in vitro and in vivo. We will further discuss the adverse effects of the accumulation of chronic senescent cells and therapeutic agents and tools to selectively target and eliminate them.

Genome (in)stability at tandem repeats

Repeat sequences account for over half of the human genome and represent a significant source of variation that underlies physiological and pathological states. Yet, their study has been hindered due to limitations in short-reads sequencing technology and difficulties in assembly. A important category of repetitive DNA in the human genome is comprised of tandem repeats (TRs), where repetitive units are arranged in a head-to-tail pattern. Compared to other regions of the genome, TRs carry between 10 and 10,000 fold higher mutation rate. There are several mutagenic mechanisms that can give rise to this propensity toward instability, but their precise contribution remains speculative. Given the high degree of homology between these sequences and their arrangement in tandem, once damaged, TRs have an intrinsic propensity to undergo aberrant recombination with non-allelic exchange and generate harmful rearrangements that may undermine the stability of the entire genome. The dynamic mutagenesis at TRs has been found to underlie individual polymorphism associated with neurodegenerative and neuromuscular disorders, as well as complex genetic diseases like cancer and diabetes. Here, we review our current understanding of the surveillance and repair mechanisms operating within these regions, and we describe how alterations in these protective processes can readily trigger mutational signatures found at TRs, ultimately resulting in the pathological correlation between TRs instability and human diseases. Finally, we provide a viewpoint to counter the detrimental effects that TRs pose in light of their selection and conservation, as important drivers of human evolution.

DNA repair enzymes in sunscreens and their impact on photoageing-A systematic review

BACKGROUND

DNA damage is one of the main factors responsible for photoageing and is predominantly attributed to ultraviolet irradiation (UV-R). Photoprotection by conventional sunscreens is exclusively prophylactic, and of no value, once DNA damage has occurred. As a result, the demand for DNA repair mechanisms inhibiting, reversing or delaying the pathologic events in UV-exposed skin has sparked research on anti-photoageing and strategies to improve the effect of conventional sunscreens. This review provides an overview of recent developments in DNA repair enzymes used in sunscreens and their impact on photoageing.

METHODS

A systematic review of the literature, up to March 2019, was conducted using the electronic databases, PubMed and Web of Science. Quality assessment was carried out using the Newcastle-Ottawa scale (NOS) to ensure inclusion of adequate quality studies only (NOS > 5).

RESULTS

Out of the 352 publications, 52 were considered relevant to the key question and included in the present review. Two major enzymes were found to play a major role in DNA damage repair in sunscreens: photolyase and T4 endonuclease V. These enzymes are capable of identifying and removing UV-R-induced dimeric photoproducts. Clinical studies revealed that sunscreens with liposome-encapsulated types of photolyase and/or T4 endonuclease V can enhance these repair mechanisms.

CONCLUSION

There is a lack of randomized controlled trials demonstrating the efficacy of DNA repair enzymes on photoageing, or a superiority of sunscreens with DNA repair enzymes compared to conventional sunscreens. Further studies are mandatory to further reveal pathogenic factors of photoageing and possible therapeutic strategies against it.

Association between antidiabetic agents use and leukocyte telomere shortening rates in patients with type 2 diabetes

Telomere length and telomere shortening rate (TSR) are accepted indicators of aging in cross-sectional population studies. This study aimed to investigate the potential influence of common antidiabetic agents on telomere length and TSR in patients with type 2 diabetes mellitus (T2DM). Leukocyte telomere length was measured through terminal restriction fragment analysis, and TSR was calculated in 388 T2DM patients. Depending on whether or not they received antidiabetic medication, patients were first divided into a treatment group and a nontreatment group. Treated patients were further subdivided into an acarbose-free group (patients taking antidiabetic agents without acarbose) and an acarbose group (patients using acarbose for more than 3 months). Results showed that untreated patients had higher TSRs than patients on antidiabetic drugs. Interestingly, patients in the acarbose group had significantly higher TSRs than patients in the acarbose-free group. Compared to the nontreatment group, the acarbose group showed better glycemic control of HbA1c, but the TSR was also higher. Our results suggest that antidiabetic treatments without acarbose can slow aging. By contrast, acarbose may accelerate biological aging in patients with T2DM, independently of glycemic control.

The effects of Astragalus Membranaceus Active Extracts on Autophagy-related Diseases

Autophagy is an evolutionarily conserved 'self-eating' process that maintains cellular, tissue, and organismal homeostasis. New studies on autophagy, mediated by subsets of autophagy proteins, are emerging in many physiological and pathological processes. Astragalus membranaceus (AM), also named Huangqi, is one of the fundamental herbs in traditional Chinese medicine and its extracts have been proved to possess many biological activities related to autophagy, including anti-oxidation, anti-inflammation, anticancer, anti-photoaging, and improvement of cardiomyocyte function. Evidence suggests that AM extracts can have therapeutic potential in autophagy dysregulation-associated diseases because of their biological positive effects. Here we will review the literature concerning the effects of AM extracts on autophagy dysregulation-associated diseases.

Telomeres and telomerase in head and neck squamous cell carcinoma: from pathogenesis to clinical implications

Strongly associated with tobacco use, heavy alcohol consumption, and with high-risk human papillomavirus (HPV) infection, head and neck squamous cell carcinoma (HNSCC) is a frequently lethal, heterogeneous disease whose pathogenesis is a multistep and multifactorial process involving genetic and epigenetic events. The majority of HNSCC patients present with locoregional advanced stage disease and are treated with combined modality strategies that can markedly impair quality of life and elicit unpredictable results. A large fraction of those who undergo locoregional treatment and achieve a complete response later develop locoregional recurrences or second field tumors. Biomarkers that are thus able to stratify risk and enable clinicians to tailor treatment plans and to personalize post-therapeutic surveillance strategies are highly desirable. To date, only HPV status is considered a reliable independent predictor of treatment response and survival in patients with HNSCC arising from the oropharyngeal site. Recent studies suggest that telomere attrition, which may be an early event in human carcinogenesis, and telomerase activation, which is detected in up to 90 % of malignancies, could be potential markers of cancer risk and disease outcome. This review examines the current state of knowledge on and discusses the implications linked to telomere dysfunction and telomerase activation in the development and clinical outcome of HNSCC.

Changes of telomere status with aging: An update

Accumulated data have shown that most human somatic cells or tissues show irreversible telomere shortening with age, and that there are strong associations between telomere attrition and aging-related diseases, including cancers, diabetes and cognitive disorders. Although it has been largely accepted that telomere attrition is one of the major causes of aging-related disorders, critical aspects of telomere biology remain unresolved, especially the lack of standardized methodology for quantification of telomere length. Another frustrating issue is that no potentially promising methods for safe prevention of telomere erosion, or for telomere elongation, have been devised. Here, we review several methods for quantification of telomere length currently utilized worldwide, considering their advantages and drawbacks. We also summarize the results of our recent studies of human cells and tissues, mainly using quantitative fluorescence in situ hybridization and Southern blotting, including those derived from patients with progeria-prone Werner syndrome and trisomy 21, and several strains of induced pluripotent stem cells. We discuss the possible merits of using telomere shortness as an indicator, or a new marker, for diagnosis of precancerous states and aging-related disorders. In addition, we describe newly found factors that are thought to impact telomere dynamics, providing a new avenue for examining the unsolved issues related to telomere restoration and maintenance.

Introduction to skin aging

Cutaneous science has seen considerable development in the last 25 years, in part due to the Omics revolution, and the appreciation that this organ is hardwired into the body's key neuro-immuno-endocrine axes. Moreover, there is greater appreciation of how stratification of skin disorders will permit more targeted and more effective treatments. Against this has been how the remarkable extension in the average human life-span, though in the West at least, this parallels worrying increases in lifestyle-associated conditions like diabetes, skin cancer etc. These demographic trends bring greater urgency to finding clinical solutions for numerous age-related deficits in skin function caused by extrinsic and intrinsic factors. Mechanisms for aging skin include the actions of reactive oxygen species (ROS), mtDNA mutations, and telomere shortening, as well as hormonal changes. We have also significantly improved our understanding of how to harness the skin's considerable regenerative capacity e.g., via its remarkable investment of stem cell subpopulations. In this way we hope to develop new strategies to selectively target the skin's capacity to undergo optimal wound repair and regeneration. Here, the unsung hero of the skin regenerative power may be the humble hair follicle, replete with its compliment of epithelial, mesenchymal, neural and other stem cells. This review introduces the topic of human skin aging, with a focus on how maintenance of function in this complex multi-cell type organ is key for retaining quality of life into old age.

Posttraumatic Stress Disorder, Adverse Childhood Events, and Buccal Cell Telomere Length in Elderly Swiss Former Indentured Child Laborers

Posttraumatic stress disorder (PTSD) is associated with increased risk for age-related diseases and early mortality. Accelerated biological aging could contribute to this elevated risk. The aim of the present study was to assess buccal cell telomere length (BTL) - a proposed marker of biological age - in men and women with and without PTSD. The role of childhood trauma was assessed as a potential additional risk factor for shorter telomere length. The sample included 62 former indentured Swiss child laborers (age: M = 76.19, SD = 6.18) and 58 healthy controls (age: M = 71.85, SD = 5.97). Structured clinical interviews were conducted to screen for PTSD and other psychiatric disorders. The Childhood Trauma Questionnaire (CTQ) was used to assess childhood trauma exposure. Quantitative polymerase chain reaction was used to measure BTL. Covariates include age, sex, years of education, self-evaluated financial situation, depression, and mental and physical functioning. Forty-eight (77.42%) of the former indentured child laborers screened positive for childhood trauma, and 21 (33.87%) had partial or full-blown PTSD. Results did not support our hypotheses that PTSD and childhood trauma would be associated with shorter BTL. In fact, results revealed a trend toward longer BTL in participants with partial or full PTSD [F(2,109) = 3.27, p = 0.04, η(2) = 0.06], and longer BTL was marginally associated with higher CTQ scores (age adjusted: β = 0.17 [95% CI: -0.01 to 0.35], t = 1.90, p = 0.06). Furthermore, within-group analyses indicated no significant association between BTL and CTQ scores. To the best of our knowledge, this is the first study exploring the association between childhood trauma and BTL in older individuals with and without PTSD. Contrary to predictions, there were no significant differences in BTL between participants with and without PTSD in our adjusted analyses, and childhood adversity was not associated with BTL. Possible explanations and future research possibilities are discussed.

Psychiatric disorders and leukocyte telomere length: Underlying mechanisms linking mental illness with cellular aging

Many psychiatric illnesses are associated with early mortality and with an increased risk of developing physical diseases that are more typically seen in the elderly. Moreover, certain psychiatric illnesses may be associated with accelerated cellular aging, evidenced by shortened leukocyte telomere length (LTL), which could underlie this association. Shortened LTL reflects a cell's mitotic history and cumulative exposure to inflammation and oxidation as well as the availability of telomerase, a telomere-lengthening enzyme. Critically short telomeres can cause cells to undergo senescence, apoptosis or genomic instability, and shorter LTL correlates with poorer health and predicts mortality. Emerging data suggest that LTL may be reduced in certain psychiatric illnesses, perhaps in proportion to exposure to the psychiatric illnesses, although conflicting data exist. Telomerase has been less well characterized in psychiatric illnesses, but a role in depression and in antidepressant and neurotrophic effects has been suggested by preclinical and clinical studies. In this article, studies on LTL and telomerase activity in psychiatric illnesses are critically reviewed, potential mediators are discussed, and future directions are suggested. A deeper understanding of cellular aging in psychiatric illnesses could lead to re-conceptualizing them as systemic illnesses with manifestations inside and outside the brain and could identify new treatment targets.

Analysis of the age of Panax ginseng based on telomere length and telomerase activity

Ginseng, which is the root of Panax ginseng (Araliaceae), has been used in Oriental medicine as a stimulant and dietary supplement for more than 7,000 years. Older ginseng plants are substantially more medically potent, but ginseng age can be simulated using unscrupulous cultivation practices. Telomeres progressively shorten with each cell division until they reach a critical length, at which point cells enter replicative senescence. However, in some cells, telomerase maintains telomere length. In this study, to determine whether telomere length reflects ginseng age and which tissue is best for such an analysis, we examined telomerase activity in the main roots, leaves, stems, secondary roots and seeds of ginseng plants of known age. Telomere length in the main root (approximately 1 cm below the rhizome) was found to be the best indicator of age. Telomeric terminal restriction fragment (TRF) lengths, which are indicators of telomere length, were determined for the main roots of plants of different ages through Southern hybridization analysis. Telomere length was shown to be positively correlated with plant age, and a simple mathematical model was formulated to describe the relationship between telomere length and age for P. ginseng.

Stem cells and aberrant signaling of molecular systems in skin aging

The skin is the body's largest organ and it is able to self-repair throughout an individual's life. With advanced age, skin is prone to degenerate in response to damage. Although cosmetic surgery has been widely adopted to rejuvinate skin, we are far from a clear understanding of the mechanisms responsible for skin aging. Recently, adult skin-resident stem/progenitor cells, growth arrest, senescence or apoptotic death and dysfunction caused by alterations in key signaling genes, such as Ras/Raf/MEK/ERK, PI3K/Akt-kinases, Wnt, p21 and p53, have been shown to play a vital role in skin regeneration. Simultaneously, enhanced telomere attrition, hormone exhaustion, oxidative stress, genetic events and ultraviolet radiation exposure that result in severe DNA damage, genomic instability and epigenetic mutations also contribute to skin aging. Therefore, cell replacement and targeting of the molecular systems found in skin hold great promise for controlling or even curing skin aging.

The secreted protein S100A7 (psoriasin) is induced by telomere dysfunction in human keratinocytes independently of a DNA damage response and cell cycle regulators

Background

Replicative senescence is preceded by loss of repeat sequences of DNA from the telomeres that eventually leads to telomere dysfunction, the accumulation of irreparable DNA double strand breaks and a DNA damage response (DDR). However, we have previously reported that whilst telomere dysfunction in human keratinocytes is associated with a permanent cell cycle arrest, the DDR was very weak and transcriptional profiling also revealed several molecules normally associated with keratinocytes terminal differentiation, including S100A7 (psoriasin).

Results

We show here that S100A7 and the closely related S100A15 (koebnerisin) are not induced by repairable or irreparable DSBs, ruling out the hypotheses that these genes are induced either by the low DDR observed or by non-specific cell cycle arrest. We next tested whether S100A7 was induced by the cell cycle effectors ARF (p14^ARF), CDKN2A (p16^INK4A) and TP53 (p53) and found that, although all induced a similar level of acute and permanent cell cycle arrest to telomere dysfunction, none induced S100A7 (except p53 over-expression at high levels), showing that cell cycle arrest is not sufficient for its induction. The closely related transcript S100A15 was also upregulated by telomere dysfunction, to a similar extent by p16^INK4A and p53 and to a lesser extent by p14^ARF.

Conclusions

Our results show that mere cell cycle arrest, the upregulation of senescence-associated cell cycle effectors and DNA damage are not sufficient for the induction of the S100 transcripts; they further suggest that whilst the induction of S100A15 expression is linked to both telomere-dependent and -independent senescence, S100A7 expression is specifically associated with telomere-dependent senescence in normal keratinocytes. As both S100A7 and S100A15 are secreted proteins, they may find utility in the early detection of human keratinocyte telomere dysfunction and senescence.

Q-FISH measurement of hepatocyte telomere lengths in donor liver and graft after pediatric living-donor liver transplantation: donor age affects telomere length sustainability

Along with the increasing need for living-donor liver transplantation (LDLT), the issue of organ shortage has become a serious problem. Therefore, the use of organs from elderly donors has been increasing. While the short-term results of LDLT have greatly improved, problems affecting the long-term outcome of transplant patients remain unsolved. Furthermore, since contradictory data have been reported with regard to the relationship between donor age and LT/LDLT outcome, the question of whether the use of elderly donors influences the long-term outcome of a graft after LT/LDLT remains unsettled. To address whether hepatocyte telomere length reflects the outcome of LDLT, we analyzed the telomere lengths of hepatocytes in informative biopsy samples from 12 paired donors and recipients (grafts) of pediatric LDLT more than 5 years after adult-to-child LDLT because of primary biliary atresia, using quantitative fluorescence in situ hybridization (Q-FISH). The telomere lengths in the paired samples showed a robust relationship between the donor and grafted hepatocytes (r = 0.765, p = 0.0038), demonstrating the feasibility of our Q-FISH method for cell-specific evaluation. While 8 pairs showed no significant difference between the telomere lengths for the donor and the recipient, the other 4 pairs showed significantly shorter telomeres in the recipient than in the donor. Multiple regression analysis revealed that the donors in the latter group were older than those in the former (p = 0.001). Despite the small number of subjects, this pilot study indicates that donor age is a crucial factor affecting telomere length sustainability in hepatocytes after pediatric LDLT, and that the telomeres in grafted livers may be elongated somewhat longer when the grafts are immunologically well controlled.

Sex- and season-dependent differences in telomere length and telomerase activity in the leaves of ash and willow

Telomeres and telomerase have important biological functions and can protect chromosome ends. In this study, sex- and season-dependent changes in telomere length and telomerase activity in ash and willow were analyzed. A statistical analysis showed that the telomere lengths of male and female trees differed significantly (P < 0.05). In ash, the telomere lengths of female trees were shorter than those of male trees. In willow, the telomere lengths of female trees were longer than those of male trees. During the annual developmental cycle, the telomere lengths of male and female ash and willow increased from April to May (P < 0.05), remained stable from May to August (P > 0.05), and decreased significantly in September and October (P < 0.05). Additionally, telomerase activities could be detected in both male and female ash and willow trees from April to October. Our results show that the telomere lengths changed according to season and sex in ash and willow. Telomere length did not have a direct positive correlation with telomerase activity.

The association of telomere length with colorectal cancer differs by the age of cancer onset

OBJECTIVES:

Telomeres are nucleoprotein structures that cap the end of chromosomes and shorten with sequential cell divisions in normal aging. Short telomeres are also implicated in the incidence of many cancers, but the evidence is not conclusive for colorectal cancer (CRC). Therefore, the aim of this study was to assess the association of CRC and telomere length.

METHODS:

In this case–control study, we measured relative telomere length from peripheral blood leukocytes (PBLs) DNA with quantitative PCR in 598 CRC patients and 2,212 healthy controls.

RESULTS:

Multivariate analysis indicated that telomere length was associated with risk for CRC, and this association varied in an age-related manner; younger individuals (≤50 years of age) with longer telomeres (80–99 percentiles) had a 2–6 times higher risk of CRC, while older individuals (>50 years of age) with shortened telomeres (1–10 percentiles) had 2–12 times the risk for CRC. The risk for CRC varies with extremes in telomere length in an age-associated manner.

CONCLUSIONS:

Younger individuals with longer telomeres or older individuals with shorter telomeres are at higher risk for CRC. These findings indicate that the association of PBL telomere length varies according to the age of cancer onset and that CRC is likely associated with at minimum two different mechanisms of telomere dynamics.

Effects of smoking on human telomerase reverse transcriptase expression in the skin

BACKGROUND

Telomeres are DNA-protein complexes that cap chromosomal ends, promoting chromosome stability. Telomerase is a ribonucleoprotein complex with a direct telomere protective function. Telomere shortening represents lifetime exposure to oxidative stress and is negatively correlated with age, smoking, and mortality. Smoking increases oxidative DNA modification and thus may influence telomere dynamics and human telomerase reverse transcriptase (hTERT) activity.

OBJECTIVES

This study investigated the effect of smoking on hTERT expression in the skin of smokers and non-smokers.

METHODS

A cross-sectional study in 20 current smokers and 20 non-smokers was conducted. Three-mm punch skin biopsies were obtained. Biopsies were examined in routine hematoxylin and eosin staining and immunohistochemistry to investigate expression of hTERT.

RESULTS

All skin biopsies from smokers and non-smokers showed cytoplasmic staining in epidermal cells. Sections positive for hTERT expression showed nuclear and some nucleolar staining in cells of the basal and suprabasal layers. In the dermis, hTERT expression was present in some skin appendages. The epidermis of smokers showed positive hTERT in 55% and negative hTERT in 45% of biopsies. The epidermis of non-smokers showed positive hTERT in 70% and negative hTERT in 30% of biopsies (P > 0.05). Among smokers, 20% showed positive and 80% showed negative hTERT expression in the dermis. Among non-smokers, 30% showed positive and 70% showed negative hTERT expression in the dermis. A higher mean pack year value was found in subjects with negative rather than positive hTERT expression (P < 0.01). In addition, pack year was inversely correlated with hTERT expression in the epidermis (P < 0.05): as pack year increased, hTERT expression decreased. Mean pack year values were higher in subjects with negative rather than positive hTERT expression in the dermis (P < 0.01).

CONCLUSIONS

This research focused on smoking as a lifestyle factor that may alter telomere length and subsequently telomerase kinetics in the skin. Findings showed a higher percentage of negative hTERT in the epidermis and dermis among smokers compared with non-smokers and a higher percentage of positive hTERT expression among non-smokers (not significant). The results of this work showed a statistically significant higher mean pack year count among cases with negative rather than positive hTERT expression in the epidermis and dermis. Pack year count was inversely correlated to hTERT scoring in the epidermis (percentage of cells stained) and hTERT expression in the dermis. Thus, smoking may affect telomerase activity in the skin, thereby contributing to skin aging.

Republished: Non-heritable genetics of human disease: spotlight on post-zygotic genetic variation acquired during lifetime

The heritability of most common, multifactorial diseases is rather modest and known genetic effects account for a small part of it. The remaining portion of disease aetiology has been conventionally ascribed to environmental effects, with an unknown part being stochastic. This review focuses on recent studies highlighting stochastic events of potentially great importance in human disease—the accumulation of post-zygotic structural aberrations with age in phenotypically normal humans. These findings are in agreement with a substantial mutational load predicted to occur during lifetime within the human soma. A major consequence of these results is that the genetic profile of a single tissue collected at one time point should be used with caution as a faithful portrait of other tissues from the same subject or the same tissue throughout life. Thus, the design of studies in human genetics interrogating a single sample per subject or applying lymphoblastoid cell lines may come into question. Sporadic disorders are common in medicine. We wish to stress the non-heritable genetic variation as a potentially important factor behind the development of sporadic diseases. Moreover, associations between post-zygotic mutations, clonal cell expansions and their relation to cancer predisposition are central in this context. Post-zygotic mutations are amenable to robust examination and are likely to explain a sizable part of non-heritable disease causality, which has routinely been thought of as synonymous with environmental factors. In view of the widespread accumulation of genetic aberrations with age and strong predictions of disease risk from such analyses, studies of post-zygotic mutations may be a fruitful approach for delineation of variants that are causative for common human disorders.

Association of telomere shortening in myocardium with heart weight gain and cause of death

We attempted to clarify myocardial telomere dynamics using samples from 530 autopsied patients using Southern blot analysis. Overall regression analysis demonstrated yearly telomere reduction rate of 20 base pairs in the myocardium. There was a significant correlation between myocardial telomere and aging. Moreover, regression analyses of telomere and heart weight yielded a telomere reduction rate of 3 base pairs per gram, and a small but significant correlation between telomere reduction and heart weight was demonstrated. Hearts of autopsied patients who had died of heart disease were significantly heavier than those of patients who had died of cancer or other diseases, and heart disease was significantly more correlated with myocardial telomere shortening than cancer or other diseases. Here we show that telomeres in myocardial tissue become shortened with aging and heart disease, and that heart disease was associated with a gain of heart weight and telomere shortening in the myocardium.

Quantitative fluorescence in situ hybridization measurement of telomere length in skin with/without sun exposure or actinic keratosis

Chromosomal and genomic instability due to telomere dysfunction is known to play an important role in carcinogenesis. To study telomere shortening in the epidermis surrounding actinic keratosis, we measured telomere lengths of basal, parabasal, and suprabasal cells in epidermis with actinic keratosis (actinic keratosis group, n = 18) and without actinic keratosis (sun-protected, n = 15, and sun-exposed, n = 13 groups) and in actinic keratosis itself as well as in dermal fibroblasts in the 3 groups, using quantitative fluorescence in situ hybridization. Among the 3 cell types, telomeres of basal cells were not always the longest, suggesting that tissue stem cells are not necessarily located among basal cells. Telomeres of basal cells in the sun-exposed group were shorter than those in the sun-protected group. Telomeres in the background of actinic keratosis and in actinic keratosis itself and those of fibroblasts in actinic keratosis were significantly shorter than those in the controls. Our findings demonstrate that sun exposure induces telomere shortening and that actinic keratosis arises from epidermis with shorter telomeres despite the absence of any histologic atypia.

The contrasting roles of lamin B1 in cellular aging and human disease

The nuclear lamina underlies the inner nuclear membrane and consists of a proteinaceous meshwork of intermediate filaments: the A- and B-type lamins. Mutations in LMNA (encoding lamin A and C) give rise to a variety of human diseases including muscular dystrophies, cardiomyopathies and the premature aging syndrome progeria (HGPS). Duplication of the LMNB1 locus, leading to elevated levels of lamin B1, causes adult-onset autosomal dominant leukodystrophy (ADLD), a rare genetic disease that leads to demyelination in the central nervous system (CNS). Conversely, reduced levels of lamin B1 have been observed in HGPS patient derived fibroblasts, as well as fibroblasts and keratinocytes undergoing replicative senescence, suggesting that the regulation of lamin B1 is important for cellular physiology and disease. However, the causal relationship between low levels of lamin B1 and cellular senescence and its relevance in vivo remain unclear. How do elevated levels of lamin B1 cause disease and why is the CNS particularly susceptible to lamin B1 fluctuations? Here we summarize recent findings as to how perturbations of lamin B1 affect cellular physiology and discuss the implications this has on senescence, HGPS and ADLD.

Determination of chronological aging parameters in epidermal keratinocytes by in vivo harmonic generation microscopy

Skin aging is an important issue in geriatric and cosmetic dermatology. To quantitatively analyze changes in keratinocytes related to intrinsic aging, we exploited a 1230 nm-based in vivo harmonic generation microscopy, combining second- and third-harmonic generation modalities. 52 individuals (21 men and 31 women, age range 19-79) were examined on the sun-protected volar forearm. Through quantitative analysis by the standard algorithm provided, we found that the cellular and nuclear size of basal keratinocytes, but not that of granular cells, was significantly increased with advancing age. The cellular and nuclear areas, which have an increase of 0.51 μm(2) and 0.15 μm(2) per year, respectively, can serve as scoring indices for intrinsic skin aging.

Non-heritable genetics of human disease: spotlight on post-zygotic genetic variation acquired during lifetime

The heritability of most common, multifactorial diseases is rather modest and known genetic effects account for a small part of it. The remaining portion of disease aetiology has been conventionally ascribed to environmental effects, with an unknown part being stochastic. This review focuses on recent studies highlighting stochastic events of potentially great importance in human disease-the accumulation of post-zygotic structural aberrations with age in phenotypically normal humans. These findings are in agreement with a substantial mutational load predicted to occur during lifetime within the human soma. A major consequence of these results is that the genetic profile of a single tissue collected at one time point should be used with caution as a faithful portrait of other tissues from the same subject or the same tissue throughout life. Thus, the design of studies in human genetics interrogating a single sample per subject or applying lymphoblastoid cell lines may come into question. Sporadic disorders are common in medicine. We wish to stress the non-heritable genetic variation as a potentially important factor behind the development of sporadic diseases. Moreover, associations between post-zygotic mutations, clonal cell expansions and their relation to cancer predisposition are central in this context. Post-zygotic mutations are amenable to robust examination and are likely to explain a sizable part of non-heritable disease causality, which has routinely been thought of as synonymous with environmental factors. In view of the widespread accumulation of genetic aberrations with age and strong predictions of disease risk from such analyses, studies of post-zygotic mutations may be a fruitful approach for delineation of variants that are causative for common human disorders.

Telomere length and pancreatic cancer: a case-control study

BACKGROUND

Telomeres, the ends of chromosomes, are critical for maintaining genomic stability and grow shorter with age. Shortened telomeres in pancreatic tissue play a key role in the pathogenesis of pancreatic cancer, and shorter telomeres in peripheral blood leukocytes (PBL) have been associated with increased risk for several cancer types. We hypothesized that shorter blood telomeres are associated with higher risk for pancreatic cancer.

METHODS

Telomere length was measured in PBLs using quantitative real-time PCR in 499 cases with pancreatic cancer and 963 cancer-free controls from the Mayo Clinic. ORs and confidence intervals (CI) were computed using logistic generalized additive models (GAM) adjusting for multiple variables.

RESULTS

In multivariable adjusted models, we observed a significant nonlinear association between telomere length in peripheral blood samples and the risk for pancreatic cancer. Risk was lower among those with longer telomeres compared with shorter telomeres across a range from the 1st percentile to 90th percentile of telomere length. There was also some evidence for higher risk among those with telomeres in the longest extreme.

CONCLUSIONS

Short telomeres in peripheral blood are associated with an increased risk for pancreatic cancer across most of the distribution of length, but extremely long telomeres may also be associated with higher risk.

IMPACT

Although the temporality of this relationship is unknown, telomere length may be useful as either a marker of pancreatic cancer risk or of the presence of undetected pancreatic cancer. If telomere shortening precedes cancer incidence, interventions to preserve telomere length may be an effective strategy to prevent pancreatic cancer.

Telomere length dynamics in the human pituitary gland: robust preservation throughout adult life to centenarian age

Many studies have demonstrated the association between telomere length in mitotic cells and aging, but the relationship between telomere length in post-mitotic cells and aging in human populations has remained largely unclear. In this study, we assessed the dynamics of telomere length (terminal restriction fragment length-TRF) in normal pituitary glands obtained at autopsy from 65 patients aged between 0 and 100 years. The initial length (the value for neonatal pituitary) was 14.2 ± 1.1 kbp (mean of the median TRF value ± SD), being the longest among those for other systemic organs. The annual telomere reduction rates for pituitary (21 bp) were equivalent to or below the lowest values for various cells and tissues. Hence, comparison of TRF lengths among organs revealed that the pituitary gland retained longer telomeres than most other organs throughout life. The median TRF value showed a significant decrease between newborns and the 61-75 age group, but then leveled off or increased slightly in advanced age groups. These data indicate that innate telomere length is highly conserved in the pituitary and suggest that pituitary telomere length provides a good basic indicator for studies of telomere biology.

Structural genetic variation in the context of somatic mosaicism

Somatic mosaicism is the result of postzygotic de novo mutation occurring in a portion of the cells making up an organism. Structural genetic variation is a very heterogeneous group of changes, in terms of numerous types of aberrations that are included in this category, involvement of many mechanisms behind the generation of structural variants, and because structural variation can encompass genomic regions highly variable in size. Structural variation rapidly evolved as the dominating type of changes behind human genetic diversity, and the importance of this variation in biology and medicine is continuously increasing. In this review, we combine the evidence of structural variation in the context of somatic cells. We discuss the normal and disease-related somatic structural variation. We review the recent advances in the field of monozygotic twins and other models that have been studied for somatic mutations, including other vertebrates. We also discuss chromosomal mosaicism in a few prime examples of disease genes that contributed to understanding of the importance of somatic heterogeneity. We further highlight challenges and opportunities related to this field, including methodological and practical aspects of detection of somatic mosaicism. The literature devoted to interindividual variation versus papers reporting on somatic variation suggests that the latter is understudied and underestimated. It is important to increase our awareness about somatic mosaicism, in particular, related to structural variation. We believe that further research of somatic mosaicism will prove beneficial for better understanding of common sporadic disorders.

Short telomeres in an oral precancerous lesion: Q-FISH analysis of leukoplakia

OBJECTIVES

A precancerous condition is a lesion that, if left untreated, leads to cancer or can be induced to become malignant. In the oral region, leukoplakia is a lesion that has been regarded as precancerous. In cases of oral carcinoma, we have frequently noticed that a type of leukoplakia histologically demonstrating hyper-orthokeratosis and mild atypia (ortho-keratotic dysplasia; OKD) is often associated with carcinoma, either synchronously or metachronously. Therefore, we consider OKD-type leukoplakia to be a true precancerous lesion.

MATERIALS AND METHODS

In an attempt to clarify the relationship between OKD as a precancerous condition in the oral mucosa and telomere length, we estimated telomere lengths in this type of leukoplakia using quantitative fluorescence in situ hybridization, and also quantified the frequency of anaphase-telophase bridges (ATBs) in comparison with squamous cell carcinoma in situ (CIS) and the background tissues of CIS and OKD.

RESULTS

Ortho-keratotic dysplasia was frequently associated with squamous cell carcinoma (45.0%) and showed significantly shorter telomeres than normal control epithelium, CIS, or the background of CIS or OKD. The frequency of ATBs was much higher in OKD than in control epithelium or CIS.

CONCLUSION

Ortho-keratotic dysplasia appears to be frequently associated with carcinoma, chromosomal instability, and excessively shortened telomeres, not only in the lesion itself but also in the surrounding background. Therefore, when this type of leukoplakia is recognized in the oral region, strict follow-up for oral squamous cell carcinoma is necessary, focusing not only on the areas of leukoplakia, but also the surrounding background.

Telomere biology in hematopoiesis and stem cell transplantation

Telomeres are long (TTAGGG)(n) nucleotide repeats and an associated protein complex located at the end of the chromosomes. They shorten with every cell division and, thus are markers for cellular aging, senescence, and replicative capacity. Telomere dysfunction is linked to several bone marrow disorders, including dyskeratosis congenita, aplastic anemia, myelodysplastic syndrome, and hematopoietic malignancies. Hematopoietic stem cell transplantation (HSCT) provides an opportunity in which to study telomere dynamics in a high cell proliferative environment. Rapid telomere shortening of donor cells occurs in the recipient shortly after HSCT; the degree of telomere attrition does not appear to differ by graft source. As expected, telomeres are longer in recipients of grafts with longer telomeres (e.g., cord blood). Telomere attrition may play a role in, or be a marker of, long term outcome after HSCT, but these data are limited. In this review, we discuss telomere biology in normal and abnormal hematopoiesis, including HSCT.

Autonomic and adrenocortical reactivity and buccal cell telomere length in kindergarten children

OBJECTIVE

To examine associations between autonomic nervous system and adrenocortical reactivity to laboratory stressors and buccal cell telomere length (BTL) in children.

METHODS

The study sample comprised 78 children, aged 5 to 6 years, from a longitudinal cohort study of kindergarten social hierarchies, biologic responses to adversity, and child health. Buccal cell samples and reactivity measures were collected in the spring of the kindergarten year. BTL was measured by real-time polymerase chain reaction, as the telomere-to-single-copy gene ratio. Parents provided demographic information; parents and teachers reported children's internalizing and externalizing behavior problems. Components of children's autonomic (heart rate, respiratory sinus arrhythmia [RSA], and preejection period [PEP]) and adrenocortical (salivary cortisol) responses were monitored during standardized laboratory challenges. We examined relationships between reactivity, internalizing and externalizing behaviors, and BTL, adjusted for age, race, and sex.

RESULTS

Heart rate and cortisol reactivity were inversely related to BTL, PEP was positively related to BTL, and RSA was unrelated to BTL. Internalizing behaviors were also inversely related to BTL (standardized β = -0.33, p = .004). Split at the median of reactivity parameters, children with high sympathetic activation (decreasing PEP), and parasympathetic withdrawal (decreasing RSA) did not differ with regard to BTL. However, children with both this profile and high cortisol reactivity (n = 12) had significantly shorter BTL (0.80 versus 1.00; χ² = 7.6, p = .006), compared with other children.

CONCLUSIONS

The combination of autonomic and adrenocortical reactivity was associated with shorter BTL in children. These data suggest that psychophysiological processes may influence, and that BTL may be a useful marker of, early biologic aging.

Accelerated in vivo epidermal telomere loss in Werner syndrome

Many data pertaining to the accelerated telomere loss in cultured cells derived from Werner syndrome (WS), a representative premature aging syndrome, have been accumulated. However, there have been no definitive data on in vivo telomere shortening in WS patients. In the present study, we measured terminal restriction fragment (TRF) lengths of 10 skin samples collected from extremities of 8 WS patients aged between 30 and 61 years that had been surgically amputated because of skin ulceration, and estimated the annual telomere loss. Whereas the values of TRF length in younger WS patients (in their thirties) were within the normal range, those in older WS patients were markedly shorter relative to non-WS controls. Regression analyses indicated that the TRF length in WS was significantly shorter than that in controls (p < 0.001). Furthermore, we found that TRF lengths in muscle adjacent to the examined epidermis were also significantly shorter than those of controls (p = 0.047). These data demonstrate for the first time that in vivo telomere loss is accelerated in systemic organs of WS patients, suggesting that abnormal telomere erosion is one of the major causes of early onset of age-related symptoms and a predisposition to sarcoma and carcinoma in WS.

Telomere dysfunction promotes metastasis in a TERC null mouse model of head and neck cancer

Squamous cell carcinoma arises from highly proliferative basal layer epithelial cells, which normally divide for a short time before detaching from the basement membrane and undergoing terminal differentiation. Basal layer cells in stratified epithelia express the reverse transcriptase known as telomerase. Most human cells do not express telomerase and therefore are subject to loss of telomeric DNA with age due to the inability of lagging strand synthesis to completely replicate chromosomal ends. Late generation telomerase deficient mice exhibit signs of premature aging including reduced function of proliferating cellular compartments. We examined development of squamous cell carcinoma in a telomerase deficient murine background with long and short telomeres. G1 Terc-/- mice (long telomeres) had fewer lymph node metastases, which correlated with increased numbers of apoptotic cells in these tumors compared with wild-type mice. However, G5 Terc-/- mice with short telomeres had increased metastatic tumor burden similar to wild type mice. This increased metastasis correlated with genomic instability and aneuploidy in tumor cells from G5 Terc-/- mice. A number of similarities with human SCC were noted in the mouse model, and dramatic differences in global gene expression profiles were shown between primary and metastatic tumors. We concluded that telomere shortening promotes metastatic tumor development in a Terc null mouse model of head and neck cancer.

Telomere length in blood, buccal cells, and fibroblasts from patients with inherited bone marrow failure syndromes

Telomeres, the nucleotide repeats and protein complex at chromosome ends, are required for chromosomal stability and are important markers of aging. Patients with dyskeratosis congenita (DC), an inherited bone marrow failure syndrome (IBMFS), have mutations in telomere biology genes, and very short telomeres. There are limited data on intra-individual telomere length (TL) variability in DC and related disorders. We measured relative TL by quantitative-PCR in blood, buccal cells, and fibroblasts from 21 patients with an IBMFS (5 Diamond-Blackfan anemia, 6 DC, 6 Fanconi anemia, and 4 Shwachman-Diamond syndrome). As expected, TL in patients with DC was significantly (p<0.01) shorter in all tissues compared with other IBMFS. In all disorders combined, the median Q-PCR TL was longer in fibroblast and buccal cells than in blood (overall T/S ratio=1.42 and 1.16 vs. 1.05, p=0.001, 0.006, respectively). Although the absolute values varied, statistically significant intra-individual correlations in TL were present in IBMFS patients: blood and fibroblast (r=0.66, p=0.002), blood and buccal cells (r=0.74, p<0.0001), and fibroblast and buccal cells (r=0.65, p=0.004). These data suggest that relative TL is tissue-independent in DC and possibly in the other IBMFS.

Regulation of senescence in cancer and aging

Senescence is regarded as a physiological response of cells to stress, including telomere dysfunction, aberrant oncogenic activation, DNA damage, and oxidative stress. This stress response has an antagonistically pleiotropic effect to organisms: beneficial as a tumor suppressor, but detrimental by contributing to aging. The emergence of senescence as an effective tumor suppression mechanism is highlighted by recent demonstration that senescence prevents proliferation of cells at risk of neoplastic transformation. Consequently, induction of senescence is recognized as a potential treatment of cancer. Substantial evidence also suggests that senescence plays an important role in aging, particularly in aging of stem cells. In this paper, we will discuss the molecular regulation of senescence its role in cancer and aging. The potential utility of senescence in cancer therapeutics will also be discussed.

The role of telomeres in the ageing of human skin

Skin is a self-renewing tissue that is required to go through extensive proliferation throughout the lifespan of an organism. Telomere shortening acts as a mitotic clock that prevents aberrant proliferation such as cancer. A consequence of this protection is cellular senescence and ageing. The telomerase enzyme complex maintains telomere length in germline cells and in cancer cells. Telomerase is also active in certain somatic cells such as those in the epidermis but is almost undetectable in the dermis. Increasing evidence indicates that telomerase plays a significant role in maintenance of skin function and proliferation. Mutations in telomerase component genes in the disease dyskeratosis congenita result in numerous epidermal abnormalities. Studies also indicate that telomerase activity in epidermal stem cells might have roles that go beyond telomere elongation. Telomeres in skin cells may be particularly susceptible to accelerated shortening because of both proliferation and DNA-damaging agents such as reactive oxygen species. Skin might present an accessible tissue for manipulation of telomerase activity and telomere length with the potential of ameliorating skin diseases associated with ageing.

An evolutionary review of human telomere biology: the thrifty telomere hypothesis and notes on potential adaptive paternal effects

Telomeres, repetitive DNA sequences found at the ends of linear chromosomes, play a role in regulating cellular proliferation, and shorten with increasing age in proliferating human tissues. The rate of age-related shortening of telomeres is highest early in life and decreases with age. Shortened telomeres are thought to limit the proliferation of cells and are associated with increased morbidity and mortality. Although natural selection is widely assumed to operate against long telomeres because they entail increased cancer risk, the evidence for this is mixed. Instead, here it is proposed that telomere length is primarily limited by energetic constraints. Cell proliferation is energetically expensive, so shorter telomeres should lead to a thrifty phenotype. Shorter telomeres are proposed to restrain adaptive immunity as an energy saving mechanism. Such a limited immune system, however, might also result in chronic infections, inflammatory stress, premature aging, and death--a more "disposable soma." With an increased reproductive lifespan, the fitness costs of premature aging are higher and longer telomeres will be favored by selection. Telomeres exhibit a paternal effect whereby the offspring of older fathers have longer telomeres due to increased telomere lengths of sperm with age. This paternal effect is proposed to be an adaptive signal of the expected age of male reproduction in the environment offspring are born into. The offspring of lineages of older fathers will tend to have longer, and thereby less thrifty, telomeres, better preparing them for an environment with higher expected ages at reproduction.

Tissue engineering of skin and cornea: Development of new models for in vitro studies

Human beings are greatly preoccupied with the unavoidable nature of aging. While the biological processes of senescence and aging are the subjects of intense investigations, the molecular mechanisms linking aging with disease and death are yet to be elucidated. Tissue engineering offers new models to study the various processes associated with aging. Using keratin 19 as a stem cell marker, our studies have revealed that stem cells are preserved in human skin reconstructed by tissue engineering and that the number of epithelial stem cells varies according to the donor's age. As with skin, human corneas can also be engineered in vitro. Among the epithelial cells used for reconstructing skin and corneas, significant age-dependent variations in the expression of the transcription factor Sp1 were observed. Culturing skin epithelial cells with a feeder layer extended their life span in culture, likely by preventing Sp1 degradation in epithelial cells, therefore demonstrating the pivotal role played by this transcription factor in cell proliferation. Finally, using the human tissue-engineered skin as a model, we linked Hsp27 activation with skin differentiation.

Variation at theTERTlocus and predisposition for cancer

Telomerase and the control of telomere length are intimately linked to the process of tumourigenesis in humans. Here I review the evidence that variation at the 5p15.33 locus, which contains theTERTgene (encoding the catalytic subunit of telomerase), might play a role in the determination of cancer risk. Mutations in the coding regions ofTERTcan affect telomerase activity and telomere length, and create severe clinical phenotypes, including bone marrow failure syndromes and a substantive increase in cancer frequency. Variants within theTERTgene have been associated with increased risk of haematological malignancies, including myelodysplastic syndrome and acute myeloid leukaemia as well as chronic lymphocytic leukaemia. Furthermore, there is good evidence from a number of independent genome-wide association studies to implicate variants at the 5p15.33 locus in cancer risk at several different sites: lung cancer, basal cell carcinoma and pancreatic cancer show strong associations, while bladder, prostate and cervical cancer and glioma also show risk alleles in this region. Thus, multiple independent lines of evidence have implicated variation in theTERTgene as a risk factor for cancer. The mechanistic basis of these risk variants is yet to be established; however, the basic biology suggests that telomere length control is a tantalising candidate mechanism underlying cancer risk.

[Skin aging]

Like the entire human organism, the skin is subject to an intrinsic unpreventable aging process. But exogenous factors also influence skin aging. Ultraviolet radiation in particular results in premature skin aging, also referred to as extrinsic skin aging or photo aging, causing in large part aging-associated changes in sun-exposed areas. Intrinsic and extrinsic aging share several molecular similarities despite morphological and pathophysiological differences. The formation of reactive oxygen species and the induction of metalloproteinases reflect central aspects of skin aging. Accumulation of fragmented collagen fibrils prevents neocollagenesis and accounts for further degradation of extracellular matrix by means of positive feedback regulation. The importance of extrinsic factors in skin aging and the detection of its mechanisms has given rise to development of various therapeutic and preventive strategies.

Telomere lengths in the oral epithelia with and without carcinoma

Aging appears to be intrinsically related to carcinogenesis. Genomic instability due to telomere shortening plays an important role in carcinoma development. In order to clarify telomere dysfunction in carcinoma development, we examined the uninvolved epithelium adjacent to carcinoma in situ (CIS), i.e. background of CIS, and CIS itself, compared to control without carcinoma, using an improved quantitative fluorescence in situ hybridization (Q-FISH) method. We also estimated anaphase bridge (AB), which is inferred to be related to chromosomal instability. In all cell types (basal, parabasal, and suprabasal), mean telomere lengths were significantly shorter in the background than in the control. We also demonstrated increased incidences of AB, not only in CIS, but also in the background and control epithelia with excessively shortened telomeres. Thus we have conclusively demonstrated that CIS arises from epithelium with short telomeres.

Telomere shortening in Barrett's mucosa and esophageal adenocarcinoma and its association with loss of heterozygosity

OBJECTIVE

Telomere shortening is thought to be associated with genetic instability. The purpose of this study was to measure telomere length in a series of Barrett's adenocarcinomas (BAs), focusing on the telomere/centromere fluorescent intensity ratio (TCR) with tissue quantitative fluorescent in situ hybridization (Q-FISH).

MATERIAL AND METHODS

A total of 11 cases of BA were evaluated for upper esophagus (UE), lower esophagus (LE), Barrett's mucosa (BM), BA, and gastric cardiac mucosa (GC). Q-FISH was performed using two kinds of peptide nucleic acid probe, specific for telomeres and centromeres. The sections were analyzed with a CCD camera and original software (Tissue Telo) for measuring TCR. In addition, Laser Capture Microdissection and GeneScan were implemented for evaluation of genetic instability.

RESULTS

The TCR values in BM and, to a lesser extent, BA were significantly lower than those in the other tissues, particularly in heterozygosity (LOH)-positive cases. However, no significant difference was evident between microsatellite instability (MSI)-positive and -negative groups.

CONCLUSIONS

In our study of BA series, telomere length appeared to change with the degree of histological atypia, with decreases linked to LOH.

Change of season-specific telomere lengths in Ginkgo biloba L

Telomeres have lately received considerable attention in the development of tree species. Normal somatic cells have limited replicative capacity and telomeres get shorten with each round of DNA replication. For broad-leaved tree species, to determine what changes happen to their somatic cells in its annual development cycle, an exhaustive research on different ages of gingko trees telomere length changes was carried out. Analysis of changes in leaf telomere lengths in the annual development cycle of Ginkgo biloba L. showed no significant changes (P > 0.05) from April to August, but a dramatic decrease in September and October (P < 0.05). Statistical analyses showed that TRF length of males and females are equal, the p values of the three age groups comparison were all bigger than 0.05. The results showed that specific apoptotic changes occur in the annual development cycle of Ginkgo biloba L.