Telomere length analysis

Macrophage-derived exosomes promote telomere fragility and senescence in tubular epithelial cells by delivering miR-155

BACKGROUND

Chronic kidney disease (CKD) is highly prevalent worldwide, and its global burden is substantial and growing. CKD displays a number of features of accelerated senescence. Tubular cell senescence is a common biological process that contributes to CKD progression. Tubulointerstitial inflammation is a driver of tubular cell senescence and a common characteristic of CKD. However, the mechanism by which the interstitial inflammation drives tubular cell senescence remains unclear. This paper aims to explore the role of exosomal miRNAs derived from macrophages in the development of tubular cell senescence.

METHODS

Among the identified inflammation-related miRNAs, miR-155 is considered to be one of the most important miRNAs involved in the inflammatory response. Macrophages, the primary immune cells that mediate inflammatory processes, contain a high abundance of miR-155 in their released exosomes. We assessed the potential role of miR-155 in tubular cell senescence and renal fibrosis. We subjected miR-155-/- mice and wild-type controls, as well as tubular epithelial cells (TECs), to angiotensin II (AngII)-induced kidney injury. We assessed kidney function and injury using standard techniques. TECs were evaluated for cell senescence and telomere dysfunction in vivo and in vitro. Telomeres were measured by the fluorescence in situ hybridization.

RESULTS

Compared with normal controls, miR-155 was up-regulated in proximal renal tubule cells in CKD patients and mouse models of CKD. Moreover, the expression of miR-155 was positively correlated with the extent of renal fibrosis, eGFR decline and p16INK4A expression. The overexpression of miR-155 exacerbated tubular senescence, evidenced by increased detection of p16INK4A/p21expression and senescence-associated β-galactosidase activity. Notably, miR-155 knockout attenuates renal fibrosis and tubule cell senescence in vivo. Interestingly, once released, macrophages-derived exosomal miR-155 was internalized by TECs, leading to telomere shortening and dysfunction through targeting TRF1. A dual-luciferase reporter assay confirmed that TRF1 was the direct target of miR-155. Thus, our study clearly demonstrates that exosomal miR-155 may mediate communication between macrophages and TECs, subsequently inducing telomere dysfunction and senescence in TECs.

CONCLUSIONS

Our work suggests a new mechanism by which macrophage exosomes are involved in the development of tubule senescence and renal fibrosis, in part by delivering miR-155 to target TRF1 to promote telomere dysfunction. Our study may provide novel strategies for the treatment of AngII-induced kidney injury.

Techniques, procedures, and applications in host genetic analysis

This chapter overviews genetic techniques' fundamentals and methodological features, including different approaches, analyses, and applications that have contributed to advancing health and disease. The aim is to describe laboratory methodologies and analyses employed to understand the genetic landscape of different biological contexts, from conventional techniques to cutting-edge technologies. Besides describing detailed aspects of the polymerase chain reaction (PCR) and derived types as one of the principles for many novel techniques, we also discuss microarray analysis, next-generation sequencing, and genome editing technologies such as transcription activator-like effector nucleases (TALENs) and the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) systems. These techniques study several phenotypes, ranging from autoimmune disorders to viral diseases. The significance of integrating diverse genetic methodologies and tools to understand host genetics comprehensively and addressing the ethical, legal, and social implications (ELSI) associated with using genetic information is highlighted. Overall, the methods, procedures, and applications in host genetic analysis provided in this chapter furnish researchers and practitioners with a roadmap for navigating the dynamic landscape of host-genome interactions.

Hypolipidemic effect and modulation of hepatic enzymes by different edible oils in obese Wistar rats

The current study assessed the hypolipidemic effect and modulation of hepatic enzymes by different edible oils in obese Wistar rats. In order to conduct this study, 36 Wistar rats that were collected at 5 weeks of age and weighed an average of 70 g were split into two groups: 28 of them were fed a high-fat diet (HFD) and 8 of them were fed a control diet. After 5 weeks of feeding, rats from the HFD (obese, n = 4) and the control diet group (n = 4) were sacrificed. Subsequently, the rest of obese rats (n = 24) were separated into six groups, including the continuing high-fat (CHF) diet group, rice bran oil (RBO) diet group, olive oil (OO) diet group, soybean oil (SO) diet group, cod liver oil (CLO) diet group, and sunflower oil (SFO) diet group, and the continuing control diet group (n = 4). Rats from each group were sacrificed following an additional 5 weeks, and all analytical tests were carried out. The results found that the interventions of RBO, CLO, and SFO in obese rats reduced their body weight non-significantly when compared with CHF. It was also observed that a non-significant reduction in weight of the heart, AAT, and EAT occurred by RBO, OO, SO, and CLO, while SFO reduced the AAT level significantly (p < 0.05). Besides, RBO, OO, SO, CLO, and SFO decreased IBAT and liver fat significantly compared to CHF. Similarly, the administration of RBO, OO, SO, and CLO reduced ALT significantly. RBO reduced GGT (p < 0.05) significantly, but other oils did not. The given oil has the efficiency to reduce TC, TAG, and LDL-C but increase HDL-C significantly. These findings suggest that different edible oils can ameliorate obesity, regulate lipid profiles, and modulate hepatic enzymes.

MiR-182-3p targets TRF2 and impairs tumor growth of triple-negative breast cancer

The telomeric repeat-binding factor 2 (TRF2) is a telomere-capping protein that plays a key role in the maintenance of telomere structure and function. It is highly expressed in different cancer types, and it contributes to cancer progression. To date, anti-cancer strategies to target TRF2 remain a challenge. Here, we developed a miRNA-based approach to reduce TRF2 expression. By performing a high-throughput luciferase screening of 54 candidate miRNAs, we identified miR-182-3p as a specific and efficient post-transcriptional regulator of TRF2. Ectopic expression of miR-182-3p drastically reduced TRF2 protein levels in a panel of telomerase- or alternative lengthening of telomeres (ALT)-positive cancer cell lines. Moreover, miR-182-3p induced DNA damage at telomeric and pericentromeric sites, eventually leading to strong apoptosis activation. We also observed that treatment with lipid nanoparticles (LNPs) containing miR-182-3p impaired tumor growth in triple-negative breast cancer (TNBC) models, including patient-derived tumor xenografts (PDTXs), without affecting mouse survival or tissue function. Finally, LNPs-miR-182-3p were able to cross the blood-brain barrier and reduce intracranial tumors representing a possible therapeutic option for metastatic brain lesions.

Urinary cadmium and peripheral blood telomere length predict the risk of renal function impairment: a study of 547 community residents of Shanxi, China

Few reports have investigated the predictive value of urinary cadmium (UCd) and telomere length on renal function impairment. Therefore, we constructed nomogram models, using a cross-sectional survey to analyze the potential function of UCd and telomere length in renal function impairment risk. We randomly selected two community populations in Shanxi, China, and general information of the subjects was collected through face-to-face questionnaire surveys. Venous blood of subjects was collected to detect absolute telomere length (ATL) by real-time quantitative chain reaction (RT-PCR). Collecting urinary samples detected UCd and urinary N-acetyl-β-d-glucosaminidase (UNAG). Estimated glomerular filtration rate (eGFR) was obtained based on serum creatinine (SCr). Nomogram models on risk prediction analysis of renal function impairment was constructed. After adjusting for other confounding factors, UCd (β = 0.853, 95% confidence interval (CI): 0.739 ~ 0.986) and ATL (β = 1.803, 95%CI: 1.017 ~ 1.154) were independent risk influencing factors for increased UNAG levels, and the risk factors for eGFR reduction were UCd (β = 1.011, 95%CI: 1.187 ~ 1.471), age (β = 1.630, 95%CI: 1.303 ~ 2.038), and sex (β = 0.181, 95%CI: 0.105 ~ 0.310). Using UCd, ATL, sex, and age to construct the nomogram, and the C-statistics 0.584 (95%CI: 0.536 ~ 0.632) and 0.816 (95%CI: 0.781 ~ 0.851) were obtained by internal verification of the calibration curve, C-statistics revealed nomogram model validation was good and using decision curve analysis (DCA) confirmed a good predictive value of the nomogram models. In a nomogram model, ATL, UCd, sex, and age were detected as independent risk factors for renal function impairment, with UCd being the strongest predictor.

An Open-Label Clinical Trial Analyzing the Efficacy of a Novel Telomere-Protecting Antiaging Face Cream

Telomere length, a hallmark of cellular senescence, decreases with age and is associated with age-related diseases. Environmental factors, including dietary and lifestyle factors, can affect the rate at which telomeres shorten, and telomere protection prevents this from happening. The protection of telomeres by natural molecules has been proposed as an antiaging strategy that may play a role in treating age-related diseases. This study investigated the effect of a cycloartane-type triterpene glycoside (astragaloside IV). Astragaloside IV is one of the primary compounds from the aqueous extract of Astragalus membranaceus, and it provides telomere protection both in vitro and in vivo. In a study cohort with 13 participants, telomere length in human skin samples was analyzed after daily treatment for 4 weeks. A comparison of the average median telomere length between the treatment and control groups (5342 bp vs. 4616 bp p = 0.0168) showed significant results. In the second clinical cohort with 20 participants, skin parameters at baseline and after 4 and 8 weeks were measured in vivo. The results show that the product improved hydration by 95%, the skin appeared brighter by 90%, and wrinkle visibility was reduced by 70%. The combination of biologically active compounds in the cream possesses telomere-protecting properties and notable antioxidant activity in vitro and in vivo.

TGS1 mediates 2,2,7-trimethyl guanosine capping of the human telomerase RNA to direct telomerase dependent telomere maintenance

Pathways that direct the selection of the telomerase-dependent or recombination-based, alternative lengthening of telomere (ALT) maintenance pathway in cancer cells are poorly understood. Using human lung cancer cells and tumor organoids we show that formation of the 2,2,7-trimethylguanosine (TMG) cap structure at the human telomerase RNA 5′ end by the Trimethylguanosine Synthase 1 (TGS1) is central for recruiting telomerase to telomeres and engaging Cajal bodies in telomere maintenance. TGS1 depletion or inhibition by the natural nucleoside sinefungin impairs telomerase recruitment to telomeres leading to Exonuclease 1 mediated generation of telomere 3′ end protrusions that engage in RAD51-dependent, homology directed recombination and the activation of key features of the ALT pathway. This indicates a critical role for 2,2,7-TMG capping of the RNA component of human telomerase (hTR) in enforcing telomerase-dependent telomere maintenance to restrict the formation of telomeric substrates conductive to ALT. Our work introduces a targetable pathway of telomere maintenance that holds relevance for telomere-related diseases such as cancer and aging.

Telomerase protects chromosome ends in stem cells and cancer cells. Here the authors show that Trimethylguaonsine Synthase 1 (TGS-1) – dependent trimethylguanosine capping of the RNA component of the human telomerase complex has an important role in directing telomere dependent telomere maintenance and suppressing the ALT pathway in cancer cells.

Interphase Chromosomes in Replicative Senescence: Chromosome Positioning as a Senescence Biomarker and the Lack of Nuclear Motor-Driven Chromosome Repositioning in Senescent Cells

This study demonstrates, and confirms, that chromosome territory positioning is altered in primary senescent human dermal fibroblasts (HDFs). The chromosome territory positioning pattern is very similar to that found in HDFs made quiescent either by serum starvation or confluence; but not completely. A few chromosomes are found in different locations. One chromosome in particular stands out, chromosome 10, which is located in an intermediate location in young proliferating HDFs, but is found at the nuclear periphery in quiescent cells and in an opposing location of the nuclear interior in senescent HDFs. We have previously demonstrated that individual chromosome territories can be actively and rapidly relocated, with 15 min, after removal of serum from the culture media. These chromosome relocations require nuclear motor activity through the presence of nuclear myosin 1β (NM1β). We now also demonstrate rapid chromosome movement in HDFs after heat-shock at 42°C. Others have shown that heat shock genes are actively relocated using nuclear motor protein activity via actin or NM1β (Khanna et al., 2014; Pradhan et al., 2020). However, this current study reveals, that in senescent HDFs, chromosomes can no longer be relocated to expected nuclear locations upon these two types of stimuli. This coincides with a entirely different organisation and distribution of NM1β within senescent HDFs.

Telomerase treatment prevents lung profibrotic pathologies associated with physiological aging

Short/dysfunctional telomeres are at the origin of idiopathic pulmonary fibrosis (IPF) in patients mutant for telomere maintenance genes. However, it remains unknown whether physiological aging leads to short telomeres in the lung, thus leading to IPF with aging. Here, we find that physiological aging in wild-type mice leads to telomere shortening and a reduced proliferative potential of alveolar type II cells and club cells, increased cellular senescence and DNA damage, increased fibroblast activation and collagen deposits, and impaired lung biophysics, suggestive of a fibrosis-like pathology. Treatment of both wild-type and telomerase-deficient mice with telomerase gene therapy prevented the onset of lung profibrotic pathologies. These findings suggest that short telomeres associated with physiological aging are at the origin of IPF and that a potential treatment for IPF based on telomerase activation would be of interest not only for patients with telomerase mutations but also for sporadic cases of IPF associated with physiological aging.

Dynamics of telomeric repeat-containing RNA expression in early embryonic cleavage stages with regards to maternal age

Telomeres are transcribed into long non-coding RNAs known as Telomeric Repeat-Containing RNA (TERRA). They have been shown to be essential regulators of telomeres and to act as epigenomic modulators at extra-telomeric sites. However the role of TERRA during early embryonic development has never been investigated. Here, we show that TERRA is expressed in murine and bovine early development following a wave pattern. It starts at 4-cell stage, reaching a maximum at the 16-cell followed by a decline at the morula and blastocyst stages. Moreover, TERRA expression is not affected by increasing oocyte donor age whereas telomere length does. This indicates that TERRA expression is independent of the telomere length in early development. Our findings anticipate an essential role of TERRA in early stages of development and this might be useful in the future for a better understanding of age related female infertility.

SFPQ and NONO suppress RNA:DNA-hybrid-related telomere instability

In vertebrates, the telomere repeat containing long, non-coding RNA TERRA is prone to form RNA:DNA hybrids at telomeres. This results in the formation of R-loop structures, replication stress and telomere instability, but also contributes to alternative lengthening of telomeres (ALT). Here, we identify the TERRA binding proteins NONO and SFPQ as novel regulators of RNA:DNA hybrid related telomere instability. NONO and SFPQ locate at telomeres and have a common role in suppressing RNA:DNA hybrids and replication defects at telomeres. NONO and SFPQ act as heterodimers to suppress fragility and homologous recombination at telomeres, respectively. Combining increased telomere fragility with unleashing telomere recombination upon NONO/SFPQ loss of function causes massive recombination events, involving 35% of telomeres in ALT cells. Our data identify the RNA binding proteins SFPQ and NONO as novel regulators at telomeres that collaborate to ensure telomere integrity by suppressing telomere fragility and homologous recombination triggered by RNA:DNA hybrids.

LncRNA TERRA forms RNA-DNA hybrids at telomere sites leading to telomere instability. Here the authors identify the RNA interacting factors NONO and SFPQ as proteins that interact with TERRA and telomere chromatin and reveal putative roles for these factors in telomere integry maintenance by interfering with RNA:DNA hybrid formation.

TERRA recruitment of polycomb to telomeres is essential for histone trymethylation marks at telomeric heterochromatin

TERRAs are long non-coding RNAs generated from the telomeres. Lack of TERRA knockout models has hampered understanding TERRAs’ functions. We recently identified chromosome 20q as one of the main origins of human TERRAs, allowing us to generate the first 20q-TERRA knockout models and to demonstrate that TERRAs are essential for telomere length maintenance and protection. Here, we use ALT 20q-TERRA knockout cells to address a direct role of TERRAs in telomeric heterochromatin formation. We find that 20q-TERRAs are essential for the establishment of H3K9me3, H4K20me3, and H3K27me3 heterochromatin marks at telomeres. At the mechanistic level, we find that TERRAs bind to PRC2, responsible for catalyzing H3K27 tri-methylation, and that its localization to telomeres is TERRA-dependent. We further demonstrate that PRC2-dependent H3K27me3 at telomeres is required for the establishment of H3K9me3, H4K20me3, and HP1 binding at telomeres. Together, these findings demonstrate an important role for TERRAs in telomeric heterochromatin assembly.

Long non-coding RNA TERRAs are essential for telomere protection and telomere length maintenance. Here the authors report a role for TERRAs in telomeric heterochromatin formation by recruiting Polycomb Repressive Complex 2 to telomeres.

Epigenetic silencing of miR-296 and miR-512 ensures hTERT dependent apoptosis protection and telomere maintenance in basal-type breast cancer cells

The catalytic subunit of the telomerase complex, hTERT, ensures unlimited proliferative potential of cancer cells by maintaining telomere function and protecting from apoptosis. Using a miRNA screening approach we identified miR-296-5p and miR-512-5p as miRNAs that target hTERT in breast cancer cells. Ectopic miR-296-5p and miR-512-5p reduce telomerase activity, drive telomere shortening and cause proliferation defects by enhancing senescence and apoptosis in breast cancer cells. In line with the relevance of hTERT expression for human cancer we found that miR-296-5p and miR-512-5p expression is reduced in human breast cancer. Accordingly, high expression of miR-296-5p and miR-512-5p target genes including hTERT is linked with significantly reduced distant metastasis free survival and relapse free survival of basal type breast cancer patients. This suggests relevance of the identified miRNAs in basal type breast cancer. Epigenetic silencing of miR-296 and miR-512 encoding genes is responsible for low levels of miR-296-5p and miR-512-5p expression in basal type breast cancer cells. Disrupting gene silencing results in a dramatic upregulation of miR-296-5p and miR-512-5p levels leading to reduced hTERT expression and increased sensitivity to the induction of apoptosis. Altogether, our data suggest that epigenetic regulatory circuits in basal type breast cancer may contribute to high hTERT levels by silencing miR-296-5p and miR-512-5p expression, thereby contributing to the aggressiveness of basal type breast cancer.

Assessment and consequences of cell senescence in atherosclerosis

PURPOSE OF REVIEW

Cell senescence is a major process regulating tissue mass, architecture and function, and underlies many diseases of ageing. Recent studies have elucidated some of the regulatory pathways leading to cell senescence, and senescence has also been found in the vasculature. However, assessment of cell senescence is problematic, and the effects of vascular cell senescence are in most cases unproven. The present article will review how senescence is assessed, how it is regulated, where senescence has been described, and the role of cell senescence in atherosclerosis.

RECENT FINDINGS

Senescence results in expression of multiple proteins, both intracellular and secreted. However, to date, none of these are specific for senescence, and multiple markers must be used together for positive identification. Despite these shortfalls, cell senescence is detectable in the vasculature in ageing and in human atherosclerosis, and recent studies in mice have indicated that cell senescence promotes both atherogenesis and multiple features of 'vulnerable' lesions in advanced atherosclerotic plaques.

SUMMARY

The almost ubiquitous presence of cell senescence in atherosclerosis and the fundamental role of senescence in regulating plaque development and stability suggest that prevention or amelioration of senescence in atherosclerosis is a viable therapeutic target.

Telomerase gene therapy rescues telomere length, bone marrow aplasia, and survival in mice with aplastic anemia

Aplastic anemia is a fatal bone marrow disorder characterized by peripheral pancytopenia and marrow hypoplasia. The disease can be hereditary or acquired and develops at any stage of life. A subgroup of the inherited form is caused by replicative impairment of hematopoietic stem and progenitor cells due to very short telomeres as a result of mutations in telomerase and other telomere components. Abnormal telomere shortening is also described in cases of acquired aplastic anemia, most likely secondary to increased turnover of bone marrow stem and progenitor cells. Here, we test the therapeutic efficacy of telomerase activation by using adeno-associated virus (AAV)9 gene therapy vectors carrying the telomerase Tert gene in 2 independent mouse models of aplastic anemia due to short telomeres (Trf1- and Tert-deficient mice). We find that a high dose of AAV9-Tert targets the bone marrow compartment, including hematopoietic stem cells. AAV9-Tert treatment after telomere attrition in bone marrow cells rescues aplastic anemia and mouse survival compared with mice treated with the empty vector. Improved survival is associated with a significant increase in telomere length in peripheral blood and bone marrow cells, as well as improved blood counts. These findings indicate that telomerase gene therapy represents a novel therapeutic strategy to treat aplastic anemia provoked or associated with short telomeres.

Telomeres and telomerase as therapeutic targets to prevent and treat age-related diseases

Telomeres, the protective ends of linear chromosomes, shorten throughout an individual's lifetime. Telomere shortening is a hallmark of molecular aging and is associated with premature appearance of diseases associated with aging. Here, we discuss the role of telomere shortening as a direct cause for aging and age-related diseases. In particular, we draw attention to the fact that telomere length influences longevity. Furthermore, we discuss intrinsic and environmental factors that can impact on human telomere erosion. Finally, we highlight recent advances in telomerase-based therapeutic strategies for the treatment of diseases associated with extremely short telomeres owing to mutations in telomerase, as well as age-related diseases, and ultimately aging itself.

Therapeutic effect of androgen therapy in a mouse model of aplastic anemia produced by short telomeres

Aplastic anemia is a rare but life-threatening disorder characterized by cytopenia in at least two of the three blood lineages. A frequent feature of patients with aplastic anemia is that they have shorter telomeres than those of age-matched controls. Testosterone has been used for over half a century in the treatment of aplastic anemia. However, although remissions are frequent following hormone therapy, the molecular mechanism underlying the response to treatment has remained unknown. Here we explored the possibility that the recently described regulation of telomerase activity by sex hormones may be the mechanism responsible. To this end, we used a mouse model of aplastic anemia induced by short telomeres in the bone marrow compartment. We found that testosterone therapy results in telomerase up-regulation, improved blood counts, and a significant extension of life-span of these mice. Importantly, longitudinal follow-up studies revealed longer telomeres in peripheral blood in mice subjected to hormone treatment. Our results demonstrate that testosterone-mediated telomerase activation can attenuate or reverse aplastic anemia disease progression associated with the presence of short telomeres.

Telomerase expression confers cardioprotection in the adult mouse heart after acute myocardial infarction

Coronary heart disease is one of the main causes of death in the developed world, and treatment success remains modest, with high mortality rates within 1 year after myocardial infarction (MI). Thus, new therapeutic targets and effective treatments are necessary. Short telomeres are risk factors for age-associated diseases, including heart disease. Here we address the potential of telomerase (Tert) activation in prevention of heart failure after MI in adult mice. We use adeno-associated viruses for cardiac-specific Tert expression. We find that upon MI, hearts expressing Tert show attenuated cardiac dilation, improved ventricular function and smaller infarct scars concomitant with increased mouse survival by 17% compared with controls. Furthermore, Tert treatment results in elongated telomeres, increased numbers of Ki67 and pH3-positive cardiomyocytes and a gene expression switch towards a regeneration signature of neonatal mice. Our work suggests telomerase activation could be a therapeutic strategy to prevent heart failure after MI.

miR-155 drives telomere fragility in human breast cancer by targeting TRF1

Telomeres consist of DNA tandem repeats that recruit the multiprotein complex shelterin to build a chromatin structure that protects chromosome ends. Although cancer formation is linked to alterations in telomere homeostasis, there is little understanding of how shelterin function is limited in cancer cells. Using a small-scale screening approach, we identified miR-155 as a key regulator in breast cancer cell expression of the shelterin component TERF1 (TRF1). miR-155 targeted a conserved sequence motif in the 3'UTR of TRF1, resulting in its translational repression. miR-155 was upregulated commonly in breast cancer specimens, as associated with reduced TRF1 protein expression, metastasis-free survival, and relapse-free survival in estrogen receptor-positive cases. Modulating miR-155 expression in cells altered TRF1 levels and TRF1 abundance at telomeres. Compromising TRF1 expression by elevating miR-155 increased telomere fragility and altered the structure of metaphase chromosomes. In contrast, reducing miR-155 levels improved telomere function and genomic stability. These results implied that miR-155 upregulation antagonizes telomere integrity in breast cancer cells, increasing genomic instability linked to poor clinical outcome in estrogen receptor-positive disease. Our work argued that miRNA-dependent regulation of shelterin function has a clinically significant impact on telomere function, suggesting the existence of "telo-miRNAs" that have an impact on cancer and aging.

Multiscale in situ analysis of the role of dyskerin in lung cancer cells

Dyskerin is one of the three subunits of the telomerase ribonucleoprotein (RNP) complex. Very little is known about the role of dyskerin in the biology of the telomeres in cancer cells. In this study, we use a quantitative, multiscale 3D image-based in situ method and several molecular techniques to show that dyskerin is overexpressed in lung cancer cell lines. Furthermore, we show that dyskerin expression correlates with telomere length both at the cell population level--cells with higher dyskerin expression have short telomeres--and at the single cell level--the shortest telomeres of the cell are spatially associated with areas of concentration of dyskerin proteins. Using this in vitro model, we also show that exogenous increase in dyskerin expression confers resistance to telomere shortening caused by a telomerase inactivating drug. Finally, we show that resistance is achieved by the recovery of telomerase activity associated with dyskerin. In summary, using a novel multiscale image-based in situ method, we show that, in lung cancer cell lines, dyskerin responds to continuous telomere attrition by increasing the telomerase RNP activity, which in turn provides resistance to telomere shortening.

Inherited bone marrow failure syndromes in 2012

Inherited bone marrow failure syndromes (CBMFS) are a heterogeneous group of genetic disorders characterized by bone marrow failure, congenital anomalies, and an increased risk of malignant disease. The representative diseases with trilineage involvement are Fanconi anemia and dyskeratosis congenita, while the disease with the single lineage cytopenia is Diamond-Blackfan anemia. Recent advances in our understanding of these diseases have come from the identification of genetic lesions responsible for the disease and their pathways. Although recent studies have identified many causative genes, mutations of these genes have only been found in less than half of the patients. Next-generation sequencing technologies may reveal new causative genes in these patients. Also, induced pluripotent stem cells derived from patients with CBMFS will be useful to study the pathophysiology of the diseases. The only long-term curative treatment for bone marrow failure in patients with inherited bone marrow failure syndromes is allogeneic hematopoietic stem cell transplantation, although this procedure has a risk of severe adverse effects. Multicenter prospective studies are warranted to establish appropriate conditioning regimens aimed at reducing transplant-related mortality.

Human Skin Fibroblast Telomeres are Shortened after Ultraviolet Irradiation

Objective:

Telomere length was used as a biomarker of cell senescence to explore the role of telomere shortening in photoageing induced by ultraviolet A (UVA) light.

Methods:

Real-time polymerase chain reaction was used to determine telomere length in cultured human fibroblasts of different generations and after exposure to UVA at doses up to 10 000 mJ/cm2. Twoway analysis of variance was used to determine whether passaging or UVA was the main factor contributing to telomere shortening.

Results:

In nonirradiated cells, telomere length was inversely related to cell generation number. In fibroblasts exposed to UVA at a dose of 1000 or 10 000 mJ/cm2, telomere length was significantly shorter than that of nonirradiated controls and was negatively related to UVA dose.

Conclusions:

Telomere length and subsequent cell viability may be affected by UVA irradiation. DNA damage caused by UVA irradiation may initiate the photoageing process and telomeres may be a useful new target for attempts to prevent photoageing.

Assessing cell and organ senescence biomarkers

A major goal in cancer and aging research is to discriminate the biochemical modifications that happen locally that could account for the healthiness or malignancy of tissues. Senescence is one general antiproliferative cellular process that acts as a strong barrier for cancer progression, playing a crucial role in aging. Here, we focus on the current methods to assess cellular senescence, discriminating the advantages and disadvantages of several senescence biomarkers.

Indirect co-culture with tendons or tenocytes can program amniotic epithelial cells towards stepwise tenogenic differentiation

BACKGROUND

Amniotic epithelial cells (AEC) have potential applications in cell-based therapy. Thus far their ability to differentiate into tenocytes has not been investigated although a cell source providing a large supply of tenocytes remains a priority target of regenerative medicine in order to respond to the poor self-repair capability of adult tendons. Starting from this premise, the present research has been designed firstly to verify whether the co-culture with adult primary tenocytes could be exploited in order to induce tenogenic differentiation in AEC, as previously demonstrated in mesenchymal stem cells. Since the co-culture systems inducing cell differentiation takes advantage of specific soluble paracrine factors released by tenocytes, the research has been then addressed to study whether the co-culture could be improved by making use of the different cell populations present within tendon explants or of the high regenerative properties of fetal derived cell/tissue.

METHODOLOGY/PRINCIPAL FINDINGS

Freshly isolated AEC, obtained from ovine fetuses at mid-gestation, were co-incubated with explanted tendons or primary tenocytes obtained from fetal or adult calcaneal tendons. The morphological and functional analysis indicated that AEC possessed tenogenic differentiation potential. However, only AEC exposed to fetal-derived cell/tissues developed in vitro tendon-like three dimensional structures with an expression profile of matrix (COL1 and THSB4) and mesenchymal/tendon related genes (TNM, OCN and SCXB) similar to that recorded in native ovine tendons. The tendon-like structures displayed high levels of organization as documented by the cell morphology, the newly deposited matrix enriched in COL1 and widespread expression of gap junction proteins (Connexin 32 and 43).

CONCLUSIONS/SIGNIFICANCE

The co-culture system improves its efficiency in promoting AEC differentiation by exploiting the inductive tenogenic soluble factors released by fetal tendon cells or explants. The co-cultural system can be proposed as a low cost and easy technique to engineer tendon for biological study and cell therapy approach.

Non-stem cancer cell kinetics modulate solid tumor progression

BACKGROUND

Solid tumors are heterogeneous in composition. Cancer stem cells (CSCs) are believed to drive tumor progression, but the relative frequencies of CSCs versus non-stem cancer cells span wide ranges even within tumors arising from the same tissue type. Tumor growth kinetics and composition can be studied through an agent-based cellular automaton model using minimal sets of biological assumptions and parameters. Herein we describe a pivotal role for the generational life span of non-stem cancer cells in modulating solid tumor progression in silico.

RESULTS

We demonstrate that although CSCs are necessary for progression, their expansion and consequently tumor growth kinetics are surprisingly modulated by the dynamics of the non-stem cancer cells. Simulations reveal that slight variations in non-stem cancer cell proliferative capacity can result in tumors with distinctly different growth kinetics. Longer generational life spans yield self-inhibited tumors, as the emerging population of non-stem cancer cells spatially impedes expansion of the CSC compartment. Conversely, shorter generational life spans yield persistence-limited tumors, with symmetric division frequency of CSCs determining tumor growth rate. We show that the CSC fraction of a tumor population can vary by multiple orders of magnitude as a function of the generational life span of the non-stem cancer cells.

CONCLUSIONS

Our study suggests that variability in the growth rate and CSC content of solid tumors may be, in part, attributable to the proliferative capacity of the non-stem cancer cell population that arises during asymmetric division of CSCs. In our model, intermediate proliferative capacities give rise to the fastest-growing tumors, resulting in self-metastatic expansion driven by a balance between symmetric CSC division and expansion of the non-stem cancer population. Our results highlight the importance of non-stem cancer cell dynamics in the CSC hypothesis, and may offer a novel explanation for the large variations in CSC fractions reported in vivo.

Rodent models for the preclinical evaluation of drugs suitable for pharmacological intervention in aging

INTRODUCTION

There is a growing scientific and public interest in the development of new antiaging drugs for the purposes of extending mean and/or maximum life span, maintaining normal physiological function, and alleviating the onset and severity of age-associated diseases. This review looks at the current screening approaches used to evaluate the efficacy of such compounds, with a particular focus on those that extend life span.

AREAS COVERED

This article reviews the current preclinical approaches for assessing longevity therapy including the assessment of antiaging drugs (aging reversal) and geroprotectors (drugs that prevent premature aging and/or slowdown or postpone aging). This article also discusses the methods and the importance in evaluating the anticarcinogenic potential and safety of antitumor drugs.

EXPERT OPINION

Based on more than 30 years of experience in the field, the authors believe that the standard testing protocols for antiaging drugs should include the simultaneous evaluation of the drug's safety, as well as its antitumor and anticarcinogenic activity potential. The authors also believe that the principles of international programs for the expert critical evaluation of pharmacological interventions should be created to improve the range of antiaging interventions available for human studies.

The use of in vitro systems to assess cancer mechanisms and the carcinogenic potential of chemicals

Carcinogenesis is a highly complex, multi-stage process that can occur over a relatively long period before its clinical manifestation. While the sequence in which a cancer cell acquires the necessary traits for tumour formation can vary, there are a number of mechanisms that are common to most, if not all, cancers across the spectrum of possible causes. Many aspects of carcinogenesis can be modelled in vitro. This has led to the development of a number of mechanistically driven, cell-based assays to assess the pro-carcinogenic and anti-carcinogenic potential of chemicals. A review is presented of the current in vitro models that can be used to study carcinogenesis, with examples of cigarette smoke testing in some of these models, in order to illustrate their potential applications. We present an overview of the assays used in regulatory genotoxicity testing, as well as those designed to model other aspects that are considered to be hallmarks of cancer. The latter assays are described with a view to demonstrating the recent advances in these areas, to a point where they should now be considered for inclusion in an overall testing strategy for chemical carcinogens.

Peto's Paradox: evolution's prescription for cancer prevention

The evolution of multicellularity required the suppression of cancer. If every cell has some chance of becoming cancerous, large, long-lived organisms should have an increased risk of developing cancer compared with small, short-lived organisms. The lack of correlation between body size and cancer risk is known as Peto's paradox. Animals with 1000 times more cells than humans do not exhibit an increased cancer risk, suggesting that natural mechanisms can suppress cancer 1000 times more effectively than is done in human cells. Because cancer has proven difficult to cure, attention has turned to cancer prevention. In this review, similar to pharmaceutical companies mining natural products, we seek to understand how evolution has suppressed cancer to develop ultimately improved cancer prevention in humans.

Behaviour of telomere and telomerase during aging and regeneration in zebrafish

Telomere length and telomerase activity are important factors in the pathobiology of human diseases. Age-related diseases and premature aging syndromes are characterized by short telomeres, which can compromise cell viability, whereas tumour cells can prevent telomere loss by aberrantly upregulating telomerase. The zebrafish (Danio rerio) offers multiple experimental manipulation advantages over other vertebrate models and, therefore, it has been recently considered as a potential model for aging, cancer, and regeneration studies. However, it has only partially been exploited to shed light on these fundamental biological processes. The aim of this study was, therefore, to investigate telomere length and telomerase expression and activity in different strains of zebrafish obtained from different stock centres to determine whether they undergo any changes during aging and regeneration. We found that although both telomerase expression and telomere length increased from embryo to adulthood stages, they drastically declined in aged fish despite telomerase activity was detected in different tissues of old fish. In addition, we observed a weaker upregulation of telomerase expression in regenerating fins of old fish, which well correlates with their impaired regeneration capacity. Strikingly, telomeres were elongated or maintained during the fin regeneration process at all ages and after repeated amputations, likely to support high cell proliferation rates. We conclude that the expression of telomerase and telomere length are closely related during the entire life cycle of the fish and that these two parameters can be used as biomarkers of aging in zebrafish. Our results also reveal a direct relationship between the expression of telomerase, telomere length and the efficiency of tissue regeneration.

Recent progress in dyskeratosis congenita

Dyskeratosis congenita (DC) is an inherited disease associated with nail dystrophy, abnormal skin pigmentation, oral leukoplakia, bone marrow failure and a predisposition to cancer. DC is a disease of defective telomere maintenance and patients with DC have very short telomeres. To date, mutations in six genes of telomerase and telomere components have been identified in patients with DC. Recently, mutations in telomerase and telomere components were also identified in patients with aplastic anemia, pulmonary fibrosis, and liver diseases who did not have mucocutaneous manifestations. These findings imply that defective telomere maintenance may cause not only classical DC but also a broad spectrum of diseases previously thought to be idiopathic, and have led to a new concept of diseases, termed "syndromes of telomere shortening". An understanding of the role of telomeres in these diseases is indispensable for diagnosis, genetic counseling and clinical management.

Telomerase deficiency and telomere dysfunction inhibit mammary tumors induced by polyomavirus middle T oncogene

Mice transgenic for MUC1 (mucin 1) and polyomavirus middle T (PyMT) develop mammary carcinomas within 15 weeks with 100% penetrance. PyMT-induced mammary tumorigenesis is closely correlated with robust telomerase expression and activity. To assess the role of telomerase activation and telomere maintenance in mammary carcinoma tumorigenesis, we generated mice expressing MUC1 and PyMT (MMT mice) but deficient in the telomerase RNA component, mTerc, on the C57BL/6 background. Successive generational intercrosses of mTerc(-/-)MMT mice produced cohorts with progressively shorter telomeres that were audited for mammary tumor formation. Relative to MMT (N=14) and G0 mTerc(+/-) female controls (G0=14), mTerc(-/-)MMT females (G1=11, G2=15, G3=15 and G4=5) showed decreased tumor volumes and increased tumor latency-MMT=95.6 days; G0 mTerc(+/-)MMT=98.6 days versus G1, G2, G3 and G4 mTerc(-/-)MMT mice with latencies of 122.6, 138.9, 140.7 and 220.9 days, respectively (controls versus G1-G4, P<0.005). The progressive impairment of lung metastasis was also observed with each successive mTerc(-/-)MMT generation. The impairment of tumorigenesis was associated with decreased proliferation of mammary epithelial and tumor cells and increased apoptosis of tumor cells. Together, these results indicate that, in the setting of viral oncoprotein mammary tumorigenesis, telomerase-dependent telomere maintenance facilitates the formation and metastatic progression of mammary tumors.

Influences on the reduction of relative telomere length over 10 years in the population-based Bruneck Study: introduction of a well-controlled high-throughput assay

BACKGROUND

Telomeres play a key role in the maintenance of chromosome integrity. Short telomeres are linked to age-associated diseases and cancer. Our aim was to determine the decrease rate of relative telomere length (RTL) over 10 years and whether this rate was influenced by age, sex and smoking behaviour.

METHODS

We compared RTL in 510 sample pairs from the longitudinal population-based Bruneck Study, which were collected in 1995 and recollected in 2005, and additionally determined RTL from 159 participants who died during follow-up. RTL were determined by a high-throughput real-time PCR assay and by applying a mathematical model.

RESULTS

The telomeres shortened, on average, by 455 bp over 10 years. The RTL shortening rate was highly correlated with baseline RTL (r = 0.674, P < 0.001). Participants who died within the observed period had considerably shorter telomeres than those who survived (median RTL of 0.98 vs 1.49; P < 0.001). In contrast to previous studies, smoking behaviour had no influence on RTL and on telomere shortening.

CONCLUSION

This is the first comprehensive longitudinal study of individuals who were, on average, 60 at baseline, and who were re-evaluated 10 years later. Our methodology proved to be a reliable tool for a rapid, accurate and cost-efficient determination of RTL with a low amount of DNA.