stem cell

Authors: Sun L, Chiang JY, Choi JY, Xiong ZM, Mao X, Collins FS, Hodes RJ, Cao K. Published: 9/3/2019 Abstract Telomerase is an enzymatic ribonucleoprotein complex that acts as a reverse transcriptase in the elongation of telomeres. Telomerase activity is well documented in embryonic stem cells and the vast majority of tumor...

Human mesenchymal stem cells (hMSCs) are multipotent non-hematopoietic precursor cells with the ability to differentiate into several tissue types. The use of hMSCs has gained significant importance in cancer therapies as well as a large number of degenerative disease therapies due to their homing abilities. However, these cells may undergo spontaneous transformation leading to them bypassing naturally built-in cell controls that could lead to senescence and carcinogenesis. Therefore, although...

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...

Naturally occurring telomerase reverse transcriptase (TERT) isoforms may regulate telomerase activity, and possibly function independently of telomeres to modulate embryonic stem (ES) cell self-renewal and differentiation....

Senescence was originally identified by the finite lifespan of normal cells that is a consequence of telomere shortening with each cycle of DNA replication. Cells undergoing replicative senescence display pronounced morphological and biochemical changes such as flattening and/or enlargement, increases in p21(WAF1) and/or p16(INK4A), a senescence-associated secretory phenotype, and often senescence-associated heterochromatic foci. Senescence also occurs in tumor cells in response to various forms...

Stem cells are endowed with the awesome power of self-renewal and multi-lineage differentiation that allows them to be major contributors to tissue homeostasis. Owing to their longevity and self-renewal capacity, they are also faced with a higher risk of genomic damage compared to differentiated cells. Damage on the genome, if not prevented or repaired properly, will threaten the survival of stem cells and culminate in organ failure, premature aging, or cancer formation. It is therefore of...

Normal human stem cells rely on low levels of active telomerase to sustain their high replicative requirements. Deficiency in telomere maintenance mechanisms leads to the development of premature aging diseases, such as dyskeratosis congenita (DC) and aplastic anemia (AA). Mutations in the unique insertion in fingers domain (IFD) in the human telomerase catalytic subunit (hTERT) have previously been identified and shown to be associated with DC and AA. However, little is known about the...

Nutrition and lifestyle, known to modulate aging process and age-related diseases, might also affect telomerase activity. Short and dysfunctional telomeres rather than average telomere length are associated with longevity in animal models, and their rescue by telomerase maybe sufficient to restore cell and organismal viability. Improving telomerase activation in stem cells and potentially in other cells by diet and lifestyle interventions may represent an intriguing way to promote health-span in...

Telomeres are the terminal part of the chromosome containing a long repetitive and non-codifying sequence that has as function protecting the chromosomes. In normal cells, telomeres lost part of such repetitive sequence in each mitosis, until telomeres reach a critical point, triggering at that time senescence and cell death. However, in most of tumor cells in each cell division a part of the telomere is lost, however the appearance of an enzyme called telomerase synthetize the segment that just...

Glioblastoma (GBM) is an invariably fatal brain tumor in which a small subpopulation of self-renewable glioma stem cells (GSCs) contributes to tumor propagation and relapse. Targeting GSCs could therefore have a significant clinical impact for GBM. Telomestatin is a naturally-occurring compound that preferentially impairs GSC growth by perturbing transcription and inducing a DNA damage response. Telomestatin stabilizes G-quadruplexes (G4s), which are guanine-rich four-strand nucleic acid...

Aging is a multifactorial and tissue-specific process involving diverse alterations regarded as the "hallmarks of aging", which include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion and altered intracellular communication. Virtually all these hallmarks are targeted by dietary olive oil, particularly by virgin olive oil, since many of its beneficial effects...

Mouse embryonic stem cell (ESC) cultures exhibit a heterogeneous mixture of metastable cells sporadically entering the 2-cell (2C)-embryo-like state, critical for ESC potency. One of 2-cell genes, Zscan4, has been shown to be responsible for telomere maintenance, genomic stability and pluripotency of mouse ESCs. Functions of other 2C-genes in ESCs remain elusive. Here we show that 2C-genes Tcstv1 and Tcstv3 play a role in regulation of telomere lengths. Overexpression or knockdown Tcstv1 and...

Measuring the length distribution of telomeres can reveal information about biological processes that are otherwise difficult to analyze experimentally....

Authors: Stella S. Hurtley, Leslie L. Roberts, L Bryan LB. Ray, Beverly A BA. Purnell, Caroline C. Ash Published: 01/20/2016, Science (New York, N.Y.) PubMed Full Text...

Telomeres are linear guanine-rich DNA structures at the ends of chromosomes. The length of telomeric DNA is actively regulated by a number of mechanisms in highly proliferative cells such as germ cells, cancer cells, and pluripotent stem cells. Telomeric DNA is synthesized by way of the ribonucleoprotein called telomerase containing a reverse transcriptase (TERT) subunit and RNA component (TERC). TERT is highly conserved across species and ubiquitously present in their respective pluripotent...

Does Sirt3 dysfunction result in poor developmental outcomes for human oocytes after in vitro maturation (IVM)?...

The non-histone chromatin binding protein High Mobility Group AT-hook protein 2 (HMGA2) plays important roles in the repair and protection of genomic DNA in embryonic stem cells and cancer cells. Here we show that HMGA2 localizes to mammalian telomeres and enhances telomere stability in cancer cells. We present a novel interaction of HMGA2 with the key shelterin protein TRF2. We found that the linker (L1) region of HMGA2 contributes to this interaction but the ATI-L1-ATII molecular region of...

Cryopreservation represents an efficient way to preserve human mesenchymal stem cells (hMSCs) at early culture/passage, and allows pooling of cells to achieve sufficient cells required for off-the-shelf use in clinical applications, e.g. cell-based therapies and regenerative medicine. To fully apply cryopreserved hMSCs in a clinical setting, it is necessary to evaluate their biosafety, e.g. chromosomal abnormality and tumourigenic potential. To date, many studies have demonstrated that...

The aim of the study was to compare the biological activity of the total pool of genes in CD34(-) umbilical cord blood and bone marrow stem cells and to search for the differences in signaling pathway gene expression responsible for the biological processes. The introductory analysis revealed a big similarity of gene expression among stem cells. When analyzing GO terms for biological processes, we observed an increased activity of JAK-STAT signaling pathway, calcium-mediated, cytokine-mediated,...

Telomerase catalyzes telomeric DNA synthesis, an essential process to maintain the length of telomere for continuous cell proliferation and genomic stability. Telomerase is activated in gametes, stem cells, and most tumor cells, and its activity is tightly controlled by a catalytic human telomerase reverse transcriptase (hTERT) subunit and a collection of associated proteins.In the present work, normal human testis tissue was used for the first time to identify proteins involved in the...

Cancer up-regulated drug resistant (CUDR) is a novel non-coding RNA gene. Herein, we demonstrate excessive CUDR cooperates with excessive CyclinD1 or PTEN depletion to accelerate liver cancer stem cells growth and liver stem cell malignant transformation in vitro and in vivo. Mechanistically, we reveal the decrease of PTEN in cells may lead to increase binding capacity of CUDR to CyclinD1. Therefore, CUDR-CyclinD1 complex loads onto the long noncoding RNA H19 promoter region that may lead to...

Mesenchymal stem cells (MSCs) are a source of adult multipotent cells important in tissue regeneration. Murine MSCs are known to proliferate poorly in vitro under normoxia. The aim of this study is to analyze the interaction of nonphysiological high oxygen and low-dose γ-irradiation onto growth, senescence, and DNA damage. Tri-potent bone marrow-derived MSCs from p53 wildtype and p53-/- mice were cultured under either 21% or 2% O2. Long-term observations revealed a decreasing ability of...

Telomerase is a key component of the telomere length maintenance system in the majority of eukaryotes. Telomerase displays maximal activity in stem and cancer cells with high proliferative potential. In humans, telomerase activity is regulated by various mechanisms, including the interaction with telomere ssDNA overhangs that contain a repetitive G-rich sequence, and with noncoding RNA, Telomeric repeat-containing RNA (TERRA), that contains the same sequence. So these nucleic acids can compete...

Mesenchymal stem cells (MSCs) have the ability to differentiate into multi-lineage cells, which confers great promise for use in regenerative medicine. In this study, canine adipose MSCs (cAD-MSCs) were isolated from canine adipose tissue. These cells clearly represented stemness (Oct4, Sox2, and Nanog) and differentiation potential into the mesoderm (adipocytes, chondrocytes, and osteoblasts) at early passages. The aim of this study was to evaluate the effects of hypoxia on the differentiation...

Telomerase activity controls telomere length, and this plays an important role in stem cells, aging and tumors. Antioxidant was shown to protect telomerase activity in normal cells but inhibit that in cancer cells, but the underlying mechanism is elusive. Here we found that 7721 hepatoma cells held a higher redox homeostasis threshold than L02 normal liver cells which caused 7721 cells to have a higher demand for ROS; MnSOD over-expression in 7721 decreased endogenous reactive oxygen species...

The low reprogramming efficiency in cells from elderly patients is a challenge that must be overcome. Recently, it has been reported that senescence-associated microRNA (miR)-195 targets Sirtuin 1 (SIRT1) to advance cellular senescence. Thus, we hypothesized that a blockade of miR-195 expression could improve reprogramming efficiency in old skeletal myoblasts (SkMs). We found that miR-195 expression was significantly higher in old SkMs (24 months) isolated from C57BL/6 mice as compared to young...

The scope of this review is to revise recent advances of the cell-based therapies of liver diseases with an emphasis on cell donor's and patient's age. Regenerative medicine with cell-based technologies as its integral part is focused on the structural and functional restoration of tissues impaired by sickness or aging. Unlike drug-based medicine directed primarily at alleviation of symptoms, regenerative medicine offers a more holistic approach to disease and senescence management aimed to...

Phosphorylation of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) at the Thr2609 cluster is essential for its complete function in DNA repair and tissue stem cell homeostasis. This phenomenon is demonstrated by congenital bone marrow failure occurring in DNA-PKcs(3A/3A) mutant mice, which require bone marrow transplantation (BMT) to prevent early mortality. Surprisingly, an increased incidence of spontaneous tumors, especially skin cancer, was observed in adult BMT-rescued...

Bortezomib inhibits the ubiquitin/proteasome pathway to achieve its anti-cancer effect and its well characterized activity is the NF-κB inhibition through which the anti-apoptotic bcl-2 expression is down-regulated and apoptosis is subsequently induced. However, the downstream molecular targets of bortezomib are still incompletely defined. Because telomere stabilization via activation of telomerase, induction of telomerase reverse transcriptase (hTERT) and appropriate expression of shelterin...

Telomeres are nucleoprotein complexes comprised of tandem arrays of repetitive DNA sequence that serve to protect chromosomal termini from inappropriate degradation, as well as to prevent these natural DNA ends from being recognized as broken DNA (double-strand breaks) and triggering of inappropriate DNA damage responses. Preservation of telomere length requires telomerase, the specialized reverse transcriptase capable of maintaining telomere length via template-mediated addition of telomeric...

Recent progress has greatly increased the understanding of telomere-bound shelterin proteins and the telomerase holoenzyme, predominantly as separate complexes. Pioneering studies have begun to investigate the requirements for shelterin-telomerase interaction. From this vantage point, focusing on human cells, we review and discuss models for how telomerase and shelterin subunits coordinate to achieve balanced telomere-length homeostasis....

Long noncoding RNA CUDR plays an important role during tumorigenesis. Herein, we demonstrate that SET1A cooperates with CUDR to accelerate hepatocarcinogenesis and promote malignant transformation of hepatocyte-like stem cells. Mechanistically, CUDR enhances the phosphorylation of RB1, C-myc expression, and the interplay between the SET1A and pRB1. Notably, CUDR acts as a sponge cushion that shows a link between SET1A and pRB1, producing a activated pRB1-SET1A complex. On the other hand, the...

Telomerase inactivation causes loss of the male germline in worms, fish, and mice, indicating a conserved dependence on telomere maintenance in this cell lineage. Here, using telomerase reverse transcriptase (Tert) reporter mice, we found that very high telomerase expression is a hallmark of undifferentiated spermatogonia, the mitotic population where germline stem cells reside. We exploited these high telomerase levels as a basis for purifying undifferentiated spermatogonia using...

Authors: Tiziano T. Moccetti, Annarosa A. Leri, Piero P. Anversa Published: 11/06/2015, Regenerative medicine PubMed Full Text...

TO summarize the researcn situation or mesenchymal stem cells (MSCs) senescence, including the characteristics and mechanisms of senescence....

Replication stress causes DNA damage at fragile sites in the genome. DNA damage at telomeres can initiate breakage-fusion-bridge cycles and chromosome instability, which can result in replicative senescence or tumor formation. Little is known about the extent of replication stress or telomere dysfunction in human embryonic stem cells (hESCs). hESCs are grown in culture with the expectation of being used therapeutically in humans, making it important to minimize the levels of replication stress...

The cycling properties of mammary stem and progenitor cells is not well understood. To determine the division properties of these cells, we administered synthetic nucleosides for varying periods of time to mice at different stages of postnatal development and monitored the rate of uptake of these nucleosides in the different mammary cell compartments. Here we show that most cell division in the adult virgin gland is restricted to the oestrogen receptor-expressing luminal cell lineage. Our data...

Stem cells of intensely regenerative tissues are susceptible to cellular damage. Although the response to this process in hematopoietic stem cells (HSCs) is crucial, the mechanisms by which hematopoietic homeostasis is sustained are not completely understood. Aging increases reactive oxygen species (ROS) levels and inflammation, which contribute to increased proliferation, senescence and/or apoptosis, leading to self-renewal premature exhaustion. In this study, we assessed ROS production, DNA...

Telomere repeat binding factor TRF2 is a member of shelterin complex with an important role in protecting and stabilizing chromosomal ends. In the present study, we investigated the effect of partial knockdown of TRF2 on radiosensitivity of telomerase immortalized human mesenchymal stem cells (hMSC-telo1), which have a higher radioresistance compared to non telomerized counterpart. Partial knockdown of the protein achieved 15-20% reduction in TRF2 protein levels. The study compared the effect of...

Telomeres, the repetitive sequences at chromosomal ends, protect intact chromosomes. Telomeres progressively shorten through successive rounds of cell divisions, and critically shortened telomeres trigger senescence and apoptosis. The enzyme that elongates telomeres and maintains their structure is known as telomerase. The catalytic subunit of this enzyme (telomerase reverse transcriptase [TERT]) is expressed at a high level in malignant cells, but at a very low level in normal cells. Although...

Reduced telomere length with increasing age in dividing cells has been implicated in contributing to the pathologies of human aging, which include cardiovascular and metabolic disorders, through induction of cellular senescence. Telomere shortening results from the absence of telomerase, an enzyme required to maintain telomere length. Telomerase reverse transcriptase (TERT), the protein subunit of telomerase, is expressed only transiently in a subset of adult somatic cells, which include stem...

Mutations in the PARN gene (encoding poly(A)-specific ribonuclease) cause telomere diseases including familial idiopathic pulmonary fibrosis (IPF) and dyskeratosis congenita, but how PARN deficiency impairs telomere maintenance is unclear. Here, using somatic cells and induced pluripotent stem cells (iPSCs) from patients with dyskeratosis congenita with PARN mutations, we show that PARN is required for the 3'-end maturation of the telomerase RNA component (TERC). Patient-derived cells as well as...

Inhibition of Mek/Erk signaling by pharmacological Mek inhibitors promotes self-renewal and pluripotency of mouse embryonic stem cells (ESCs). Intriguingly, Erk signaling is essential for human ESC self-renewal. Here we demonstrate that Erk signaling is critical for mouse ESC self-renewal and genomic stability. Erk-depleted ESCs cannot be maintained. Lack of Erk leads to rapid telomere shortening and genomic instability, in association with misregulated expression of pluripotency genes, reduced...

Poly(ADP-ribosyl)ation is known to be involved in a variety of cellular processes, such as DNA repair, cell death, telomere regulation, genomic stability and cell differentiation by poly(ADP-ribose) polymerase (PARP). While PARP inhibitors are presently under clinical investigation for cancer therapy, little is known about their side effects. However, PARP involvement in mesenchymal stem cell (MSC) differentiation potentiates MSC-related side effects arising from PARP inhibition. In this study,...

We investigate the in vivo patterns of stem cell divisions in the human hematopoietic system throughout life. In particular, we analyze the shape of telomere length distributions underlying stem cell behavior within individuals. Our mathematical model shows that these distributions contain a fingerprint of the progressive telomere loss and the fraction of symmetric cell proliferations. Our predictions are tested against measured telomere length distributions in humans across all ages, collected...

Previously, we reported that a novel subpopulation of young mesenchymal stem cells (YMSCs) existed in old bone marrow, which possessed high antiaging properties as well as excellent efficacy for cardiac repair. MicroRNAs (miRNAs) have emerged as key regulators in post-transcriptional gene expression programs, and however, it is unknown whether miRNAs directly control stem cell senescence. Here we present the first evidence that miR-195 overexpressed in old MSCs (OMSCs) induces stem cell...

hTERT is the key component of telomerase and its overactivation contributes to maintaining telomere length and cell immortalization. Previously, we identified RFPL3 as a new transcription activator of hTERT in lung cancers. However, the exact mechanism of RFPL3 in mediating hTERT activation and its associated signal regulatory network remain unclear. In this study, we found that RFPL3 colocalized and interacted directly with CBP in the nucleus of lung cancer cells. Immunohistochemical analysis...

Benign prostatic hyperplasia (BPH) treatments have changed little over many years and do not directly address the underlying cause. Because BPH is characterised by uncontrolled cell growth, the chromosomal telomeres should be eroded in the reported absence or low levels of telomerase activity, but this is not observed. We investigated the telomere biology of cell subpopulations from BPH patients undergoing transurethral resection of prostate (TURP). Measurement of TERC, TERT, and telomerase...

Aberrant MSC function was shown to contribute to the pathophysiology of myelodysplastic syndromSe (MDS). In comparison to adult MDS, pediatric MDS displayed different features both in biologically and clinically. The mechanisms for adult MDS may not be applicable in pediatric MDS. However, understanding of the MSCs in pediatric MDS is lacking. In this study, we investigated the proliferation capacity of MSCs from pediatric MDS patients at clone cell level....

Recently, the newly identified embryonic stem cell marker, Zinc finger and SCAN domain containing 4 gene (ZSCAN4), which plays a key role in genomic stability by regulating telomere elongation, was shown to co-localize with TRF1 foci. This suggests that the interaction of ZSCAN4 with TRF1 functions in regulation of telomere elongation in ESC. Based on these studies, we hypothesized that ZSCAN4 binds to TRF1 in cancer cells to function in regulating telomere length. The purpose of this study was...

In vitro expansion changes replication and differentiation capacity of mesenchymal stem cells (MSCs), increasing challenges and risks, while limiting the sufficient number of MSCs required for cytotherapy. Here, we characterized and compared proliferation, differentiation, telomere length and pluripotency marker expression in MSCs of various origins....

The proliferation and differentiation potential of bone marrow mesenchymal stem cells (BMMSCs) declines with age and with in vitro passages. However, the underlying mechanisms and putative approaches to maintain their function are not fully understood. Recent studies have revealed telomere attrition as the core initiator determining functional decline in aging of BMMSCs. Telomere attrition activates downstream p53 signaling and compromises mitochondrial metabolism via the peroxisome...

Myelodysplastic syndrome (MDS) associated with an acquired, isolated deletion of chromosome 5q (del (5q) MDS), represent a clonal disorder of hematopoiesis and a clinically distinct entity of MDS. Treatment of del (5q) MDS with the drug lenalidomide has significantly improved quality of life leading to transfusion independence and complete cytogenetic response rates (CCR) in the majority of patients. Telomeres are located at the end of eukaryotic chromosomes and are linked to replicative...

Cardiac aging has been confounded by the concept that the heart is a postmitotic organ characterized by a predetermined number of myocytes, which is established at birth and largely preserved throughout life until death of the organ and organism. Based on this premise, the age of cardiac cells should coincide with that of the organism; at any given time, the heart would be composed of a homogeneous population of myocytes of identical age. The discovery that stem cells reside in the heart and...

BIBR1532 is a highly specific telomerase inhibitor, although the molecular basis for inhibition is unknown. Here we present the crystal structure of BIBR1532 bound to Tribolium castaneum catalytic subunit of telomerase (tcTERT). BIBR1532 binds to a conserved hydrophobic pocket (FVYL motif) on the outer surface of the thumb domain. The FVYL motif is near TRBD residues that bind the activation domain (CR4/5) of hTER. RNA binding assays show that the human TERT (hTERT) thumb domain binds the P6.1...

Acquired aplastic anemia (AAA) is rare disorders caused due to the profound or almost complete bone marrow failure. It is a life threatening hematopoietic stem cells disorder, which is characterized by pancytopenia or complete loss of blood-forming cells. The aim of the present study is to screen for the mutations in telomerase complex genes, and to establish a molecular and hematological profile of Indian sub population....

In mammals, DNA methylation is essential for protecting repetitive sequences from aberrant transcription and recombination. In some developmental contexts (e.g., preimplantation embryos) DNA is hypomethylated but repetitive elements are not dysregulated, suggesting that alternative protection mechanisms exist. Here we explore the processes involved by investigating the role of the chromatin factors Daxx and Atrx. Using genome-wide binding and transcriptome analysis, we found that Daxx and Atrx...

PCBs are persistent organic pollutants that are carcinogenic and immunotoxic and have developmental toxicity. This suggests that they may interfere with normal cell maturation. Cancer and stem/progenitor cells have telomerase activity to maintain and protect the chromosome ends, but lose this activity during differentiation. We hypothesized that PCBs interfere with telomerase activity and the telomere complex, thereby disturbing cell differentiation and stem/progenitor cell function. HL-60 cells...

Mouse embryonic stem cells (mESCs) have a remarkable capacity to maintain normal genome stability and karyotype in culture. We previously showed that infrequent bursts of Zscan4 expression (Z4 events) are important for the maintenance of telomere length and genome stability in mESCs. However, the molecular details of Z4 events remain unclear. Here we show that Z4 events involve unexpected transcriptional derepression in heterochromatin regions that usually remain silent. During a Z4 event, we...

In addition to being a hallmark at active genes, histone variant H3.3 is deposited by ATRX at repressive chromatin regions, including the telomeres. It is unclear how H3.3 promotes heterochromatin assembly. We show that H3.3 is targeted for K9 trimethylation to establish a heterochromatic state enriched in trimethylated H3.3K9 at telomeres. In H3f3a(-/-) and H3f3b(-/-) mouse embryonic stem cells (ESCs), H3.3 deficiency results in reduced levels of H3K9me3, H4K20me3 and ATRX at telomeres. The...

The stem terminus element (STE), which was discovered 13 y ago in human telomerase RNA, is required for telomerase activity, yet its mode of action is unknown. We report that the Schizosaccharomyces pombe telomerase RNA, TER1 (telomerase RNA 1), also contains a STE, which is essential for telomere maintenance. Cells expressing a partial loss-of-function TER1 STE allele maintained short stable telomeres by a recombination-independent mechanism. Remarkably, the mutant telomere sequence was...

Telomerase, a unique ribonucleoprotein complex that contains the telomerase reverse transcriptase (TERT), the telomerase RNA component (TERC) and the TERC-binding protein dyskerin, is required for continued cell proliferation in stem cells and cancer cells. Here we identify SRSF11 as a novel TERC-binding protein that localizes to nuclear speckles, subnuclear structures that are enriched in pre-messenger RNA splicing factors. SRSF11 associates with active telomerase enzyme through an interaction...

Accumulated data indicate that wound-care products should have a composition equivalent to that of the skin: a combination of particular growth factors and extracellular matrix (ECM) proteins endogenous to the skin, together with viable epithelial cells, fibroblasts, and mesenchymal stem cells (MSCs). Strategies consisting of bioengineered dressings and cell-based products have emerged for widespread clinical use; however, their performance is not optimal because chronic wounds persist as a...

The Developmental Origins of Health and Disease (DOHaD) paradigm is one of the most rapidly expanding areas of biomedical research. Environmental stressors that can impact on DOHaD encompass a variety of environmental and occupational hazards as well as deficiency and oversupply of nutrients and energy. They can disrupt early developmental processes and lead to increased susceptibility to disease/dysfunctions later in life. Presentations at the fourth Conference on Prenatal Programming and...

Siegl-Cachedenier I, Flores I, Klatt P, Blasco MA. J Cell Biol. ;179(2):277-90. Organ homeostasis and organismal survival are related to the ability of stem cells to sustain tissue regeneration. As a consequence of accelerated telomere shortening, telomerase-deficient mice show defective tissue regeneration and premature death. This suggests a direct impact of...

Ilaria Chiodi and Chiara Mondello* Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, Pavia, Italy Telomerase canonical activity at telomeres prevents telomere shortening, allowing chromosome stability and cellular proliferation. To perform this task, the catalytic subunit (telomerase reverse transcriptase, TERT) of the enzyme works as a reverse transcriptase together...

By John Gever, Senior Editor, MedPage Today Published: September 21, 2010 Reviewed by Zalman S. Agus, MD; Emeritus Professor University of Pennsylvania School of Medicine and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner Shortened telomeres in peripheral blood leukocytes may predict relapse, malignant progression, and poorer survival in patients with...

E Hiyama and K Hiyama, British Journal of Cancer 96, 1020-1024. Telomeres, guanine-rich tandem DNA repeats of the chromosomal end, provide chromosomal stability, and cellular replication causes their loss. In somatic cells, the activity of telomerase, a reverse transcriptase that can elongate telomeric repeats, is usually diminished after...

H. Jiang, Z. Ju, K.L. Rudolph; Z Gerontol Geriat 40:314-324; 2007 Telomeres form the ends of human chromosomes. Telomeres shorten with each round of cell division and this mechanism limits proliferation of human cells to a finite number of cell divisions by inducing replicative senescence, differentiation, or apoptosis....

For many years, the transplantation of hematopoietic stem cells has been used to treat some diseases of the hematopoietic system. For a very long time, only bone marrow was used as a source of hematopoietic stem cells for this method of treatment. However, to comply with allogeneic bone marrow transplantation, an antigenically compatible donor is necessary. Transplantations from unrelated donors are associated with increased risk of a graft-versus-host reaction, transplant rejection and,...

Clonal evolutionary processes can drive pathogenesis in human diseases, with cancer being a prominent example. To prevent or treat cancer, mechanisms that can potentially interfere with clonal evolutionary processes need to be understood better. Mathematical modeling is an important research tool that plays an ever-increasing role in cancer research. This paper discusses how mathematical models can be useful to gain insights into mechanisms that can prevent disease initiation, help analyze...

Aging is the most prominent risk factor contributing to the development of neurodegenerative disorders. In the United States, over 35 million of elderly people suffer from age-related diseases. Aging impairs the self-repair ability of neuronal cells, which undergo progressive deterioration. Once initiated, this process hampers the already limited regenerative power of the central nervous system, making the search for new therapeutic strategies particularly difficult in elderly affected patients....

Mutations in the human telomerase reverse transcriptase (TERT) promoter are the most frequent non-coding mutations in cancer, but their molecular mechanism in tumorigenesis has not been established. We used genome editing of human pluripotent stem cells with physiological telomerase expression to elucidate the mechanism by which these mutations contribute to human disease. Surprisingly, telomerase-expressing embryonic stem cells engineered to carry any of the three most frequent TERT promoter...

Multipotent mesenchymal stem cells (MSCs) are widely used as seed cells in studies of tissue engineering and regenerative medicine; however, their clinical application is limited due to replicative senescence. It has been demonstrated that telomerase expression extends the lifespan and maintains the bone-forming ability of MSCs; however, the detailed role and the underlying molecular mechanisms in MSCs remain largely unknown. In the present study, we found that senescence was associated with...

There is a well-established association between aging and the onset of metastasis. Although the mechanisms through which age impinges upon the malignant phenotype remain uncharacterized, the role of a senescent microenvironment has been emphasized. We reported previously that human epithelial cells that undergo telomere-driven chromosome instability (T-CIN) display global microRNA (miR) deregulation and develop migration and invasion capacities. Here, we show that post-crisis cells are not able...

We sought to determine the location, expression, and characterization of cardiac stem cells (CSCs) in children with end-stage heart failure (ESHF). We hypothesized ESHF myocardium would contain an increased number of CSCs relative to age-matched healthy myocardium, and ESHF-derived CSCs would have diminished functional capacity as evidenced by reduced telomere length....

Mammalian telomeres and subtelomeres are marked by heterochromatic epigenetic modifications, including repressive DNA methylation and histone methylation (e.g., H3K9me3 and H4K20me3). Loss of these epigenetic marks results in increased rates of telomere recombination and elongation. Other than these repressive epigenetic marks, telomeric and subtelomeric H3 and H4 are underacetylated. Yet, whether histone acetylation also regulates telomere length has not been directly addressed. We thought to...

The elevation of circulating LPS has been associated with obesity and aging. However, whether and how LPS contributes to adipose tissue dysfunction is unclear. In this study, we investigated the effect of LPS on the adipogenic capacity and cellular senescence of adipocyte progenitors. Stromal-vascular cells were isolated from inguinal adipose tissue of C57BL/6 mice and treated with LPS during the different time periods of adipocyte differentiation. We found that LPS treatment for 24 h prior to...

Zidovudine and tenofovir are the two main nucleos(t)ide analogs used to prevent mother-to-child transmission of HIV. In vitro, both drugs bind to and integrate into human DNA and inhibit telomerase. The objective of the present study was to assess the genotoxic effects of either zidovudine or tenofovir-based combination therapies on cord blood cells in newborns exposed in utero....

Hepatocyte transplantation is an alternative to liver transplantation in certain disorders such as inherited liver diseases and liver failure. It is a relatively less complicated surgical procedure, and has the advantage that it can be repeated several times if unsuccessful. Another advantage is that hepatocytes can be isolated from partly damaged livers which are not suitable for liver transplantation. Despite these advantages hepatocyte transplantation is less popular. Important issues are...

Telomere length and telomerase activity are important indicators of cellular senescence and replicative ability. Loss of telomerase is associated with ageing and the development of osteoarthritis. Implantation of telomerase-positive cells, chondrocytes, or stem cells expressing a normal chondrocyte phenotype is desired for cartilage repair procedures. The objective of this study was to identify at what age chondrocytes and at what passage bone marrow-derived mesenchymal stem cells (MSCs) become...

We first aimed to generate transformed cell lines from a human induced pluripotent stem cell (hiPSC)-teratoma, and then examined the tumorigenic risks of the differentiated cells from hiPSC explant, because hiPSC-derivatives give rise to tumors in immune-deficient mice when transplanted. The colonies isolated from sparse cultures of hiPSC-teratoma cells expressed NANOG and OCT3/4 strongly, and telomerase reverse transcriptase (TERT) weakly. However, soft agar assay demonstrated that only one of...

Aging is characterized by a decrease in genome integrity, impaired organ maintenance, and an increased risk of cancer, which coincide with clonal dominance of expanded mutant stem and progenitor cell populations in aging tissues, such as the intestinal epithelium, the hematopoietic system, and the male germline. Here we discuss possible explanations for age-associated increases in the initiation and/or progression of mutant stem/progenitor clones and highlight the roles of stem cell quiescence,...

Non-coding RNAs can modulate histone modifications that, at the same time, affect transcript expression levels. Here, we dissect such a network in mouse embryonic stem cells (ESCs). It regulates the activity of the reverse transcriptase telomerase, which synthesizes telomeric repeats at the chromosome ends. We find that histone H3 serine 10 phosphorylation set by Aurora kinase B (AURKB) in ESCs during the S phase of the cell cycle at centromeric and (sub)telomeric loci promotes the expression of...

In adults, bone hematopoietic cells are responsible for the lifelong production of all blood cells. It is affected in aging, with progressive loss of physiological integrity leading to impaired function by cellular intrinsic and extrinsic factors. However, intervention measures, which directly inhibit the aging of hematopoietic cells, remain to be investigated. In the present study, 10 µmol/l ginsenoside Rg1 (Rg1) markedly alleviated the aging phenotypes of Sca‑1+ hematopoietic cells...

The incidence of CVD increases with aging, because of long-term exposure to risk factors/stressors. Aging is a complex biological process resulting in progressive loss of physiological integrity, leading to impaired function and increased vulnerability to death. The main hallmarks of aging are cellular senescence, stem cell exhaustion, and altered intracellular communication. The major hallmarks of senescence are mitochondrial dysfunction, genomic instability, telomere attrition and epigenetic...

Dyskeratosis congenita (DC) and related diseases are a heterogeneous group of disorders characterized by impaired telomere maintenance, known collectively as the telomeropathies. Disease-causing variants have been identified in 10 telomere-related genes including the reverse transcriptase (TERT) and the RNA component (TERC) of the telomerase complex. Variants in TERC and TERT can impede telomere elongation causing stem cells to enter premature replicative senescence and/or apoptosis as telomeres...

Pulmonary fibrosis has been linked molecularly and pathophysiologically by abnormal telomere maintenance. Short telomere lengths are commonly found in both the familial and sporadic forms, telomerase mutations being the most common identifiable genetic cause of the disease. Telomeres are repeated nucleotide sequences that cap the ends of chromosomes and protect them from damage. Telomeres are eroded with cell division and shorten with age. Telomere integrity is mediated by the telomerase...

The researches in the dynamic changes of the progress of HSCs aging are very limited and necessary. In this study, male C57BL/6 mice were divided into 5 groups by age. We found that the superoxide damage of HSPCs started to increase from the middle age (6 months old), with notably reduced antioxidation ability. In accordance with that, the senescence of HSPCs also started from the middle age, since the self-renewal and differentiation ability remarkably decreased, and senescence-associated...

Lymphocytes are unique among cells in that they undergo programmed DNA breaks and translocations, but that special property predisposes them to chromosomal instability (CIN), a cardinal feature of neoplastic lymphoid cells that manifests as whole chromosome- or translocation-based aneuploidy. In several lymphoid malignancies translocations may be the defining or diagnostic markers of the diseases. CIN is a cornerstone of the mutational architecture supporting lymphoid neoplasia, though it is...

Dyskeratosis congenita (DC) is an inherited bone marrow failure syndrome characterized by the presence of short telomeres at presentation. Mutations in ten different genes, whose products are involved in the telomere maintenance pathway, have been shown to cause DC. The X-linked form is the most common form of the disease and is caused by mutations in the gene DKC1, encoding the protein dyskerin. Dyskerin is required for the assembly and stability of telomerase and is also involved in ribosomal...

Previously, we found that the delivery of mouse ES (mES) cell-derived proteins to adult fibroblasts enables the full reprogramming of these cells, converting them to mouse pluripotent stem cells (protein-iPS cells) without transduction of defined factors. During reprogramming, global gene expression and epigenetic status such as DNA methylation and histone modifications convert from somatic to ES-equivalent status. mES cell extract-derived iPS cells are biologically and functionally...

Myelodysplastic syndrome (MDS) risk correlates with advancing age, therapy-induced DNA damage, and/or shorter telomeres, but whether telomere erosion directly induces MDS is unknown. Here, we provide the genetic evidence that telomere dysfunction-induced DNA damage drives classical MDS phenotypes and alters common myeloid progenitor (CMP) differentiation by repressing the expression of mRNA splicing/processing genes, including SRSF2. RNA-seq analyses of telomere dysfunctional CMP identified...

Clonospheres formed due to modified culture conditions are often studied for their stem cell like behaviour. The main objective of the current study is to compare the stem cell markers and link it to hTERT levels by monitoring their quantitative gene expression as they are potential targets for new generation combination therapeutics....

Coronary artery disease (CAD) is the leading cause of death worldwide. The efficacy and safety of statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) in primary and secondary prevention of CAD are confirmed in several large studies. It is well known that statins have some pleiotropic, anti-atherosclerotic effects. We review the molecular mechanisms underlying the beneficial effects of statins revealed in recently published studies. Endothelial cell injury is regarded as the...

The Suv39h1 and Suv39h2 H3K9 histone methyltransferases (HMTs) have a conserved role in the formation of constitutive heterochromatin and gene silencing. Using a transgenic mouse model system we demonstrate that elevated expression of Suv39h1 increases global H3K9me3 levels in vivo. More specifically, Suv39h1 overexpression enhances the imposition of H3K9me3 levels at constitutive heterochromatin at telomeric and major satellite repeats in primary mouse embryonic fibroblasts. Chromatin...

Telomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at...

The cornea protects the anterior eye and accounts for two thirds of the eyes refractive capacity. The homeostasis of corneal epithelium is thought to be maintained by putative stem cells residing in the epithelial basal layer. As a tissue constantly exposed to environmental stress, the cornea is hypothesised to accumulate persistent DNA damage events with time in stem cell populations. Recently, telomere associated DNA damage foci (TAFs) have been suggested as a marker for persistent DNA damage...

Expression of type I interferons (IFNs) can be induced by DNA-damaging agents, but the mechanisms and significance of this regulation are not completely understood. We found that the transcription factor IRF3, activated in an ATM-IKKα/β-dependent manner, stimulates cell-autonomous IFN-β expression in response to double-stranded DNA breaks. Cells and tissues with accumulating DNA damage produce endogenous IFN-β and stimulate IFN signaling in vitro and in vivo. In turn, IFN acts to amplify...

To minimize the risk of tumorigenesis in mesenchymal stem cells (MSCs), G-banding analysis is widely used to detect chromosomal aberrations in MSCs. However, a critical limitation of G-banding is that it only reflects the status of metaphase cells, which can represent as few as 0.01% of tested cells. During routine cytogenetic testing in MSCs, we often detect chromosomal aberrations in minor cell populations. Therefore, we aimed to investigate whether such a minority of cells can expand over...

Human cardiac progenitor cells (hCPC) improve heart function after autologous transfer in heart failure patients. Regenerative potential of hCPCs is severely limited with age, requiring genetic modification to enhance therapeutic potential. A legacy of work from our laboratory with Pim1 kinase reveals effects on proliferation, survival, metabolism, and rejuvenation of hCPCs in vitro and in vivo. We demonstrate that subcellular targeting of Pim1 bolsters the distinct cardioprotective effects of...

Adipose stem cells (ASCs) are an appealing source of cells for therapeutic intervention; however, the environment from which ASCs are isolated may impact their usefulness. Using a range of functional assays, we have evaluated whether ASCs isolated from an obese environment are comparable to cells from non-obese adipose tissue. Results showed that ASCs isolated from obese tissue have a reduced proliferative ability and a loss of viability together with changes in telomerase activity and DNA...

Telomere dysfunction-induced loss of genome integrity and its associated DNA damage signaling and checkpoint responses are well-established drivers that cause tissue degeneration during ageing. Cancer, with incidence rates greatly increasing with age, is characterized by short telomere lengths and high telomerase activity. To study the roles of telomere dysfunction and telomerase reactivation in ageing and cancer, the protocol shows how to generate two murine inducible telomerase knock-in...

Telomere length, a highly heritable trait, is longer in offspring of older fathers. This perplexing feature has been attributed to the longer telomeres in sperm of older men and it might be an 'epigenetic' mechanism through which paternal age plays a role in telomere length regulation in humans. Based on two independent (discovery and replication) twin studies, comprising 889 twin pairs, we show an increase in the resemblance of leukocyte telomere length between dizygotic twins of older fathers,...

Cord blood (CB) leukocytes have inherent telomere length (TL) variation, and CB hematopoietic stem cells (HSC) can maintain high telomerase levels preventing telomere attrition in vitro. We evaluated TL changes in 13 adult double-unit CB transplant (CBT) recipients. In the 26 units, we observed a marked variation in CB TL at thaw (median, 9.99 kilobases [kb]; range, 6.85 to 13.5). All 13 patients engrafted. Of 11 engrafting with 1 unit, there was no correlation between unit dominance and TL...

The actions of transcription factors, chromatin modifiers and noncoding RNAs are crucial for the programming of cell states. Although the importance of various epigenetic machineries for controlling pluripotency of embryonic stem (ES) cells has been previously studied, how chromatin modifiers cooperate with specific transcription factors still remains largely elusive. Here, we find that Pontin chromatin remodelling factor plays an essential role as a coactivator for Oct4 for maintenance of...

Telomere syndromes have their most common manifestation in lung disease that is recognized as idiopathic pulmonary fibrosis and emphysema. In both conditions, there is loss of alveolar integrity, but the underlying mechanisms are not known. We tested the capacity of alveolar epithelial and stromal cells from mice with short telomeres to support alveolar organoid colony formation and found that type 2 alveolar epithelial cells (AEC2s), the stem cell-containing population, were limiting. When...

The Telomeric repeat amplification protocol (TRAP) is a highly sensitive PCR-based assay and prove to be an important tool for understanding the role of telomerase in cancer and various tissues that harbors telomerase positive stem cells. This assay measures telomerase activity where the amount of target is dependent upon the activity of the enzyme. This protocol consists of two steps: first, telomeric repeats are added to the substrate by telomerase present in the cell and second, the extended...

Mature adipocytes have shown dynamic plasticity to be converted into fibroblast-like and lipid-free cells. After the dedifferentiation process, these cells re-entered the cell cycle and acquired a high proliferation potential, becoming a valid source of stem cells. However, many aspects of the cellular biosafety about dedifferentiated fat cells remained unclear. This study aimed to elucidate their potential susceptibility to malignant transformation and to ascertain the safety of these cells for...

The causal role of aneuploidy in cancer initiation remains under debate since mutations of euploidy-controlling genes reduce cell fitness but aneuploidy strongly associates with human cancers. Telomerase activation allows immortal growth by stabilizing telomere length, but its role in aneuploidy survival has not been characterized. Here, we analyze the response of primary human cells and murine hematopoietic stem cells (HSCs) to aneuploidy induction and the role of telomeres and the telomerase...

Nucleostemin (NS) is a nucleolar GTP-binding protein that is involved in a plethora of functions including ribosomal biogenesis and maintenance of telomere integrity. In addition to its expression in cancerous cells, the NS gene is expressed in stem cells including embryonic stem cells (ESCs). Previous knockdown and knockout studies have demonstrated that NS is important to preserve the self-renewality and high expression levels of pluripotency marker genes in ESCs. Here, we found that forced...

A hallmark of cancer cells is an activated telomere maintenance mechanism, which allows prolonged survival of the malignant cells. In more than 80% of tumours, telomeres are elongated by the enzyme telomerase, which adds de novo telomere repeats to the ends of chromosomes. Cancer cells are also characterized by expression of active LINE-1 elements (L1s, long interspersed nuclear elements-1). L1 elements are abundant retrotransposons in the eukaryotic genome that are primarily known for...

Culture microenvironment plays a critical role in the propagation and differentiation of human embryonic stem cells (hESCs) and their differentiated progenies. Although high efficiency of hESC differentiation to keratinocytes (hESC-Kert) has been achieved, little is known regarding the effects of early culture microenvironment and pertinent extracellular matrix (ECM) interactions during epidermal commitment on subsequent proliferative capacity of hESC-Kert. The aim of this study is to evaluate...

Nuclear receptor subfamily 0, group B, member 1 (Nr0b1, also known as Dax1) is regarded as an important component of the transcription factor network that governs pluripotency in mouse embryonic stem (ES) cells. Here we generated inducible knockout ES cells for Nr0b1 using the Cre-loxP system and analyzed its precise function. We succeeded in establishing the Nr0b1-null ES cells and confirmed their pluripotency by showing their contribution to chimeric embryos. However, they proliferated slowly...

Nonsense-mediated mRNA decay (NMD) is a post-transcriptional mechanism that targets aberrant transcripts and regulates the cellular RNA reservoir. Genetic modulation in vertebrates suggests that NMD is critical for cellular and tissue homeostasis, although the underlying mechanism remains elusive. Here, we generate knockout mice lacking Smg6/Est1, a key nuclease in NMD and a telomerase cofactor. While the complete loss of Smg6 causes mouse lethality at the blastocyst stage, inducible deletion of...

Cells of different organs at different ages have an intrinsic set of kinetics that dictates their behavior. Transformation into cancer cells will inherit these kinetics that determine initial cell and tumor population progression dynamics. Subject to genetic mutation and epigenetic alterations, cancer cell kinetics can change, and favorable alterations that increase cellular fitness will manifest themselves and accelerate tumor progression. We set out to investigate the emerging intratumoral...

Regular exercise has multi-system anti-aging effects. Here we summarize how exercise impacts the major hallmarks of aging. We propose that, besides searching for novel pharmaceutical targets of the aging process, more research efforts should be devoted to gaining insights into the molecular mediators of the benefits of exercise and to implement effective exercise interventions for elderly people....

Much like an individual's hairstyle, hair fibers along the scalp see a number of changes over the course of one's lifetime. As the decades pass, the shine and volume synonymous with youthful hair may give way to thin, dull, and brittle hair commonly associated with aging. These changes are a result of a compilation of genetic and environmental elements influencing the cells of the hair follicle, specifically the hair follicle stem cells and melanocytes. Telomere shortening, decrease in cell...

Human ALT cancers show high mutation rates in ATRX and DAXX. Although it is well known that the absence of ATRX/DAXX disrupts H3.3 deposition at heterochromatin, its impact on H3.3 deposition and post-translational modification in the global genome remains unclear. Here, we explore the dynamics of phosphorylated H3.3 serine 31 (H3.3S31ph) in human ALT cancer cells. While H3.3S31ph is found only at pericentric satellite DNA repeats during mitosis in most somatic human cells, a high level of...

Bloom syndrome helicase (BLM) has key roles in homologous recombination repair, telomere maintenance, and DNA replication. Germ-line mutations in the BLM gene causes Bloom syndrome, a rare disorder characterized by premature aging and predisposition to multiple cancers, including breast cancer. The clinicopathologic significance of BLM in sporadic breast cancers is unknown. We investigated BLM mRNA expression in the Molecular Taxonomy of Breast Cancer International Consortium cohort (n = 1,950)...

Increasing evidence suggests that the mesenchymal stem cells (MSCs) derived from placenta of fetal origin (fPMSCs) are superior to MSCs of other sources for cell therapy. Since the initial number of isolated MSCs is limited, in vitro propagation is often required to reach sufficient numbers of cells for therapeutic applications, during which MSCs may undergo genetic and/or epigenetic alterations that subsequently increase the probability of spontaneous malignant transformation. Thus, factors...

The mechanism of functional restoration by stem cell therapy remains poorly understood. Novel manganese-enhanced MRI and bioluminescence reporter gene imaging were applied to follow myocardial viability and cell engraftment, respectively. Human-placenta-derived amniotic mesenchymal stem cells (AMCs) demonstrate unique immunoregulatory and precardiac properties. In this study, the restorative effects of 3 AMC-derived subpopulations were examined in a murine myocardial injury model: (1) unselected...

We studied potential changes in the subventricular zone (SVZ) stem cell niche of the senescence-accelerated mouse prone-8 (SAM-P8) aging model. Bromodeoxyuridine (BrdU) assays with longtime survival revealed a lower number of label-retaining stem cells in the SAM-P8 SVZ compared with the SAM-Resistant 1 (SAM-R1) control strain. We also found that in SAM-P8 niche signaling is attenuated and the stem cell pool is less responsive to the self-renewal niche factor pigmented epithelium-derived factor...

Cardiac atrial appendage stem cells (CASCs) have recently emerged as an attractive candidate for cardiac regeneration after myocardial infarction. As with other cardiac stem cells, CASCs have to be expanded ex vivo to obtain clinically relevant cell numbers. However, foetal calf serum (FCS), which is routinely used for cell culturing, is unsuitable for clinical purposes, and influence of long-term in vitro culture on CASC behaviour is unknown....

Werner syndrome (WS) is a rare human autosomal recessive premature aging disorder characterized by early onset of aging-associated diseases, chromosomal instability, and cancer predisposition. The function of the DNA helicase encoded by WRN, the gene responsible for WS, has been studied extensively. WRN helicase is involved in the maintenance of chromosome integrity through DNA replication, repair, and recombination by interacting with a variety of proteins associated with DNA repair and...

Cancer stem cells (CSCs) are thought to be responsible for tumor progression, metastasis, and recurrence. HER2 overexpression is associated with increased CSCs, which may explain the aggressive phenotype and increased likelihood of recurrence for HER2(+) breast cancers. Telomerase is reactivated in tumor cells, including CSCs, but has limited activity in normal tissues, providing potential for telomerase inhibition in anti-cancer therapy. The purpose of this study was to investigate the effects...

Adipose tissue-derived stromal cells (ASCs) natively reside in a relatively low-oxygen tension (i.e., hypoxic) microenvironment in human body. Low oxygen tension (i.e., in situ normoxia), has been known to enhance the growth and survival rate of ASCs, which, however, may lead to the risk of tumourigenesis. Here, we investigated the tumourigenic potential of ASCs under their physiological condition to ensure their safe use in regenerative therapy. Human ASCs isolated from subcutaneous fat were...

Cellular senescence is a state of irreversible cell cycle arrest that has been involved in many gastrointestinal diseases, including human cholestatic liver disorders. Senescence may play a role in biliary atresia, primary sclerosing cholangitis, cellular rejection, and primary biliary cirrhosis, four liver diseases affecting cholangiocytes and the biliary system. In this review, we examine proposed mechanisms of senescence-related biliary diseases, including hypotheses associated with the...

Telomere extension has been proposed as a means to improve cell culture and tissue engineering and to treat disease. However, telomere extension by nonviral, nonintegrating methods remains inefficient. Here we report that delivery of modified mRNA encoding TERT to human fibroblasts and myoblasts increases telomerase activity transiently (24-48 h) and rapidly extends telomeres, after which telomeres resume shortening. Three successive transfections over a 4 d period extended telomeres up to 0.9...

Functional decline in stem cell-mediated regeneration contributes to aging associated with cellular senescence in c-kit+ cardiac progenitor cells (CPCs). Clinical implementation of CPC-based therapy in elderly patients would benefit tremendously from understanding molecular characteristics of senescence to antagonize aging. Nucleostemin (NS) is a nucleolar protein regulating stem cell proliferation and pluripotency....

Proliferating mammalian stem and cancer cells express telomerase [telomerase reverse transcriptase (TERT)] in an effort to extend chromosomal G-overhangs and maintain telomere ends. Telomerase-expressing cells also have higher levels of the single-stranded DNA-binding protein SSB1, which has a critical role in DNA double-strand break (DSB) repair. Here, we report that SSB1 binds specifically to G-strand telomeric DNA in vitro and associates with telomeres in vivo. SSB1 interacts with the TERT...

During aging, progressive deleterious changes increase the risk of disease and death. Prominent molecular hallmarks of aging are genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, cellular senescence, stem cell exhaustion, and altered intercellular communication. Long noncoding RNAs (lncRNAs) play important roles in a wide range of biological processes, including age-related diseases like cancer, cardiovascular pathologies, and neurodegenerative disorders....

Prolonged culture of embryonic stem cells (ESCs) leads them to adopt embryonal carcinoma cell features, creating enormous dangers for their further application. The mechanism involved in ESC stability has not, however, been extensively studied. We previously reported that SMAD family member 3 (Smad3) has an important role in maintaining mouse ESC stability, as depletion of Smad3 results in cancer cell-like properties in ESCs and Smad3-/- ESCs are prone to grow large, malignant teratomas. To...

Telomeres are located at the outermost ends of all eukaryotic chromosomes and provide for the maintenance of genomic stability and integrity during the life span of organisms. The length of telomeres shortens due to each round of DNA replication, genotoxic insults, and/or reactive oxygen species. To counteract this shortening, certain types of cells, including stem cells, male/female germline cells, granulosa cells, early embryos, and most cancerous cells, express an enzyme known as telomerase,...

Cellular senescence is a stable cell cycle arrest that normal cells undergo in response to a variety of intrinsic and extrinsic stimuli, including progressive telomere shortening, changes in telomeric structure or other forms of genotoxic as well nongenotoxic stress. Senescence is thought to have originated as a remodelling program that is active in embryonic development and acts as a key tumour suppressor mechanism during the reproductive stage in early adult life, by leading to the removal of...

Significant improvement in the understanding of mesenchymal stem cell biology paved the way to their clinical use. Human lipoaspirates derived from mesenchymal stem cells (adipose-derived stem cells) continue to draw the attention of researchers in the field of basic and applied research due to their regenerative, reparative, angiogenic, antiapoptotic, and immunosuppressive properties, all of which collectively point out their therapeutic potential. There is still, however, a need for further...

In regenerative medicine, human cord blood-derived multipotent mesenchymal stromal cells (CBMSCs) stand out for their biological peculiarities demonstrated in in vitro and in vivo preclinical studies. Here, we present our 9-year experience for the consistent isolation of CBMSCs. Although nearly one CB unit out of two retains the potential to give rise to MSC colonies, only 46% of them can be cultured till low passages (P≥4), but one-fourth of those reaches even higher passages (P≥8)....

We have previously shown that hsa-miR-520d-5p can convert cancer cells into induced pluripotent stem cells (iPSCs) or mesenchymal stem cells (MSCs) via a dedifferentiation by a demethylation mechanism....

To determine the effects of Benzo(a)pyrene (BaP) on the development of early preimplantation embryo by exposure to physiologic concentrations of BaP based on a previous report in human ovarian follicular fluid and serum....

Dyskeratosis congenita (DC) is an inherited multisystem disorder, characterized by oral leukoplakia, nail dystrophy, and abnormal skin pigmentation, as well as high rates of bone marrow (BM) failure, solid tumors, and other medical problems such as osteopenia. DC and telomere biology disorders (collectively referred to as TBD here) are caused by germline mutations in telomere biology genes leading to very short telomeres and limited proliferative potential of hematopoietic stem cells. We found...

Over the last 50 years, major improvements have been made in our understanding of the driving forces, both parallel and opposing, that lead to aging and cancer. Many theories on aging first proposed in the 1950s, including those associated with telomere biology, senescence, and adult stem-cell regulation, have since gained support from cumulative experimental evidence. These views suggest that the accumulation of mutations might be a common driver of both aging and cancer. Moreover, some tumor...

Dental-pulp tissue is often exposed to inflammatory injury. Sequested growth factors or angiogenic signaling proteins that are released following inflammatory injury play a pivotal role in the formation of reparative dentin. While limited or moderate angiogenesis may be helpful for dental pulp maintenance, the induction of significant level of angiogenesis is probably highly detrimental. Hitherto, several studies have addressed the effects of proinflammatory stimuli on the survival and...

In this issue of Blood, Wang et al elegantly show that telomere shortening results in DNA damage that induces apoptosis and senescence in quiescent hematopoietic stem cells (HSCs)....

Autoimmune cytopenia is a frequent manifestation of primary immunodeficiencies. Two siblings presented with Evans syndrome, viral infections, and progressive leukopenia. DNA available from one patient showed a homozygous frameshift mutation in tripeptidyl peptidase II (TPP2) abolishing protein expression. TPP2 is a serine exopeptidase involved in extralysosomal peptide degradation. Its deficiency in mice activates cell death programs and premature senescence. Similar to cells from naïve,...

Haplo-insufficiency of telomerase genes in humans leads to telomere syndromes such as dyskeratosis congenital and idiopathic pulmonary fibrosis. Generation of pluripotent stem cells from telomerase haplo-insufficient donor cells would provide unique opportunities toward the realization of patient-specific stem cell therapies. Recently, pluripotent human embryonic stem cells (ntESCs) have been efficiently achieved by somatic cell nuclear transfer (SCNT). We tested the hypothesis that SCNT could...

Telomere maintenance by telomerase is impaired in the stem cell disease dyskeratosis congenita and during human aging. Telomerase depends upon a complex pathway for enzyme assembly, localization in Cajal bodies, and association with telomeres. Here, we identify the chaperonin CCT/TRiC as a critical regulator of telomerase trafficking using a high-content genome-wide siRNA screen in human cells for factors required for Cajal body localization. We find that TRiC is required for folding the...

While global chromatin conformation studies are emerging, very little is known about the chromatin conformation of human telomeres. Most studies have focused on the role of telomeres as a tumor suppressor mechanism. Here we describe how telomere length regulates gene expression long before telomeres become short enough to produce a DNA damage response (senescence). We directly mapped the interactions adjacent to specific telomere ends using a Hi-C (chromosome capture followed by high-throughput...

The pathophysiology of severe aplastic anemia (SAA) is immune-mediated destruction of hematopoietic stem and progenitor cells (HSPCs). Most patients respond to immunosuppressive therapies, but a minority transform to myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), frequently associated with monosomy 7 (-7). Thirteen SAA patients were analyzed for acquired mutations in myeloid cells at the time of evolution to -7, and all had a dominant HSPC clone bearing specific acquired...

Los of renal function is associated with uremia-associated immune deficiency, which contributes significantly to the mortality and morbidity of end-stage renal disease (ESRD) patients. In this review, the effect of ESRD on the adaptive cellular immune system is discussed. Progressive loss of renal function causes a preferential loss of number and function of lymphoid cells. More in depth analysis of these changes reveals a loss of thymic function, attrition of telomeres, and expanded memory T...

Werner syndrome (WS) is a premature aging disorder characterized by chromosomal instability and cancer predisposition. Mutations in WRN are responsible for the disease and cause telomere dysfunction, resulting in accelerated aging. Recent studies have revealed that cells from WS patients can be successfully reprogrammed into induced pluripotent stem cells (iPSCs). In the present study, we describe the effects of long-term culture on WS iPSCs, which acquired and maintained infinite proliferative...

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...

End-stage renal disease (ESRD) patients have a defective T-cell-mediated immune system which is related to excessive premature ageing of the T-cell compartment. This is likely to be caused by the uremia-associated pro-inflammatory milieu, created by loss of renal function. Therefore, ESRD patients are highly susceptible for infections, have an increased risk for virus-associated cancers, respond poorly to vaccination and have an increased risk for atherosclerotic diseases. Three ageing...

The study of canine bone marrow-derived mesenchymal stem cells (MSCs) has a prominent position in veterinary cell-based applications. Yet the plethora of breeds, their different life spans, and interbreed variations provide unclearness on what can be achieved specifically by such therapies. In this study, we compared a set of morphological, physiological, and genetic markers of MSCs derived from large dog breeds, namely, Border collie, German shepherd, Labrador, Malinois, Golden retriever, and...

Genomic instability is recognized as one of the most important hurdles in the expanding field of stem cell-based therapies. In the recent years, an accumulating body of evidence has shown that human stem cells undergo a diverse program of biological changes upon ex vivo cultivation that include numerical and structural chromosomal abnormalities, point mutations, variation of telomere length, and epigenetic instability. As the field moves forward, the growing awareness of the risk factors...

Cellular senescence is the state of permanent inhibition of cell proliferation. Senescent cells are characterized by several features including increased activity of senescence-associated β-galactosidase (SA-β-GAL) and senescenceassociated secretory phenotype (SASP). In vitro, 2 types of senescence have been described. One is telomere-dependent replicative senescence and the second is stress-induced premature senescence (SIPS). Despite some tissue-specific characteristics many kinds of cells,...

Animals and plants have biological clocks that help to regulate circadian cycles, seasonal rhythms, growth, development and sexual maturity. If aging is not a stochastic process of attrition but is centrally orchestrated, it is reasonable to suspect that the timing of senescence is also influenced by one or more biological clocks. Evolutionary reasoning first articulated by G. Williams suggests that multiple, redundant clocks might influence organismal aging. Some aging clocks that have been...

Mesenchymal stem cells (MSCs) from various animals undergo spontaneous transformation in vitro,establishing some malignant characteristics. However,this phenomenon seems seldom appearing in human (h)MSCs. To address the question whether the hMSCs really do not undergo the spontaneous transformation and why,the present study compared MSCs from two species under the same conditions, the commercialized primary hMSCs whose in vitro life span is very uniform, and the rat (r)MSCs whose spontaneous...

Telomeres are repetitive sequence structures at the ends of linear chromosomes that consist of double-stranded DNA repeats followed by a short single-stranded DNA protrusion. Telomeres need to be replicated in each cell cycle and protected from DNA-processing enzymes, tasks that cells execute using specialized protein complexes such as telomerase (that includes TERT), which aids in telomere maintenance and replication, and the shelterin complex, which protects chromosome ends. These complexes...

Germline mutations in telomere biology genes cause dyskeratosis congenita (DC), an inherited bone marrow failure and cancer predisposition syndrome. DC is a clinically heterogeneous disorder diagnosed by the triad of dysplastic nails, abnormal skin pigmentation, and oral leukoplakia; Hoyeraal-Hreidarsson syndrome (HH), a clinically severe variant of DC, also includes cerebellar hypoplasia, immunodeficiency, and intrauterine growth retardation. Approximately 70% of DC cases are associated with a...

Our understanding of the pathophysiology of aplastic anemia is undergoing significant revision, with implications for diagnosis and treatment. Constitutional and acquired disease is poorly delineated, as lesions in some genetic pathways cause stereotypical childhood syndromes and also act as risk factors for clinical manifestations in adult life. Telomere diseases are a prominent example of this relationship. Accelerated telomere attrition is the result of mutations in telomere repair genes and...

Decline in the gene expression of senescence repressor Bmi1, and telomerase, together with telomere shortening, underlay senescence of stem cells cultured for multiple passages. Here, we investigated whether the impairment of senescence preventing mechanisms can be efficiently counteracted by exposure of human adipose-derived stem cells to radio electric asymmetrically conveyed fields by an innovative technology, named Radio Electric Asymmetric Conveyer (REAC). Due to REAC exposure, the number...

Telomere shortening limits the proliferative capacity of human cells, and age-dependent shortening of telomeres occurs in somatic tissues including hematopoietic stem cells (HSCs). It is currently unknown whether genomic and molecular damage that occurs in HSCs induced by telomere shortening is transmitted to the progenitor cells. Here we show that telomere shortening results in DNA damage accumulation and gene expression changes in quiescent HSCs of aged mice. Upon activation, a subset of HSCs...

DNA methylation at the C-5 position of cytosine (5mC) is one of the best-studied epigenetic modifications and plays important roles in diverse biological processes. Iterative oxidation of 5mC by the ten-eleven translocation (Tet) family of proteins generates 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). 5fC and 5caC are selectively recognized and excised by thymine DNA glycosylase (TDG), leading to DNA demethylation. Functional characterization of Tet...

Limited resources for adult stem cells necessitate their in vitro culture prior to clinical use. Investigating mitochondrial DNA (mtDNA) and telomere shortening has proved to be important indications of stem cell validity. This study was designed to investigate these indicators in multiple passages of three adult stem cell lines which were produced in our stem cell laboratory....

Glioblastoma multiforme is the most aggressive primary tumor of the central nervous system. Glioma stem cells (GSCs), a small population of tumor cells with stem-like properties, are supposedly responsible for glioblastoma multiforme relapse after current therapies. In approximately thirty percent of glioblastoma multiforme tumors, telomeres are not maintained by telomerase but through an alternative mechanism, termed alternative lengthening of telomere (ALT), suggesting potential interest in...

Feline oral squamous cell carcinoma (SCC) has very poor prognosis. Here, a retrospective pilot study was conducted on 20 feline oral SCC patients who underwent stereotactic radiation therapy (SRT), to evaluate: (1) the value of putative tumour initiating cell (TIC) markers of human head and neck SCC (CD44, Bmi-1); (2) telomere length (TL) specifically in putative TICs; and (3) tumour relative telomerase activity (TA). Significant inverse correlations were found between treatment outcomes and...

Standard treatment for glioblastoma comprises surgical resection, chemotherapy with temozolomide, and radiotherapy. Nevertheless, majority of glioblastoma patients have recurrence from resistance to the cytotoxic conventional therapies. We examined combinational effects of KML001, an arsenic compound targeting telomeres of chromosomes with temozolomide or irradiation, in glioblastoma cell lines and xenograft models, to overcome the therapeutic limitation of chemoradiation therapy for...

Telomerase is a ribonucleoprotein enzyme that is necessary for overcoming telomere shortening in human germ and stem cells. Mutations in telomerase or other telomere-maintenance proteins can lead to diseases characterized by depletion of hematopoietic stem cells and bone marrow failure (BMF). Telomerase localization to telomeres requires an interaction with a region on the surface of the telomere-binding protein TPP1 known as the TEL patch. Here, we identify a family with aplastic anemia and...

Revascularization of necrotic pulp has been successful in the resolution of periradicular inflammation; yet, several case studies suggest the need for cell-based therapies using mesenchymal stem cells (MSCs) as an alternative for de novo pulp regeneration. Because the availability of MSCs may be limited, especially in an aged population, the current study reports an alternative approach in generating MSCs from epidermal keratinocytes through a process called epithelial-mesenchymal transition...

The telomeric complex has been analyzed in detail for its role in regulating telomere protection and telomere length. Now, modern genome-editing techniques in human embryonic stem cells reveal TPP1 as the essential recruitment factor for telomerase, with additional functions in telomerase activation and definition of telomere length homeostasis....

We have reported that telomere fluorescence units (TFUs) of established induced pluripotent stem cells (iPSCs) derived from human amnion (hAM933) and fetal lung fibroblasts (MRC-5) were significantly longer than those of the parental cells, and that the telomere extension rates varied quite significantly among clones without chromosomal instability, although the telomeres of other iPSCs derived from MRC-5 became shorter as the number of passages increased along with chromosomal abnormalities...

The development of sensitive telomerase biosensors is hindered by the restricted accessibility of telomere strand (TS) primer and the limited enzyme reaction space, which is mainly confined by the vertical distance. In this work, we designed an electrochemical telomerase biosensor based on a spired DNA tetrahedron TS primer (STTS). By adding a rigid dsDNA spire onto the top of the DNA tetrahedron, we successfully regulated the distance between the TS primer and the surface, and thus greatly...

Dyskeratosis congenita (DC) is an inherited bone marrow failure (BMF) syndrome characterized by the classic triad of abnormal skin pigmentation, nail dystrophy, and oral leukoplakia. However, patients usually develop BMF and are predisposed to cancer, with increased risk for squamous cell carcinoma and hematolymphoid neoplasms. DC is a disease of defective telomere maintenance and is heterogeneous at the genetic level. It can be inherited in X-linked, autosomal dominant, or autosomal recessive...

Severe liver diseases are characterized by expansion of liver progenitor cells (LPC), which correlates with disease severity. However, the origin and role of LPC in liver physiology and in hepatic injury remains a contentious topic. We found that ductular reaction cells in human cirrhotic livers express hepatocyte nuclear factor 1 homeobox B (HNF1β). However, HNF1β expression was not present in newly generated epithelial cell adhesion molecule (EpCAM)-positive hepatocytes. In order to...

Telomeres are specific nucleoprotein structures at the ends of eukaryotic chromosomes. Telomeres and telomere-associated proteins maintain genome stability by protecting the ends of chromosomes from fusion and degradation. In normal somatic cells, the length of the telomeres gradually becomes shortened with cell division. In tumor cells, the shortening of telomeres length is accelerated under the increased proliferation pressure. However, it will be maintained at an extremely short length as the...

Telomere length homeostasis is essential for the long-term survival of stem cells, and its set point determines the proliferative capacity of differentiated cell lineages by restricting the reservoir of telomeric repeats. Knockdown and overexpression studies in human tumor cells showed that the shelterin subunit TPP1 recruits telomerase to telomeres through a region termed the TEL patch. However, these studies do not resolve whether the TPP1 TEL patch is the only mechanism for telomerase...

A consistent association has been observed between leukocyte telomere length (LTL) and atherosclerosis, but the mechanisms underlying these associations are still not well understood. Premature biology aging was evident in atherosclerotic plaques, characterized by reduced cell proliferation, irreversible growth arrest and apoptosis, and telomere attrition. As atherosclerosis is a state of chronic low-grade inflammation and increased oxidative stress, shortened LTL in patients with...

Pediatric ependymomas are highly recurrent tumors resistant to conventional chemotherapy. Telomerase, a ribonucleoprotein critical in permitting limitless replication, has been found to be critically important for the maintenance of tumor-initiating cells (TICs). These TICs are chemoresistant, repopulate the tumor from which they are identified, and are drivers of recurrence in numerous cancers. In this study, telomerase enzymatic activity was directly measured and inhibited to assess the...

Telomere length, an important feature of life span control, is dependent on the activity of telomerase (a key enzyme of the telomere-length-maintaining system). Telomerase RNA is a component of telomerase and, thus, is crucial for its activity. The structures of telomerase RNA genes and their promoter regions were compared for the long-living naked mole rat and different organisms. Two rare polymorphisms in Heterocephalus glaber telomerase RNA (hgTER) were identified: A→G in the first loop of...

Statins are one of the most potent drugs in delaying age-related inflammatory changes in the arterial vessel wall, slowing down the progression of atherosclerosis. Statins have also been shown to abrogate telomere-attributed cardiovascular risk. The goal of our study was to explore a potential effect of atorvastatin on telomerase activity in peripheral blood mononuclear cells (PBMCs) and T-lymphocytes (T cells)....

Soft tissue sarcomas (STS) are malignant tumors of mesenchymal origin. A substantial portion of these tumors exhibits complex karyotypes and lack characterized chromosomal aberrations. Owing to such properties, both histopathologic and molecular classification of these tumors has been a significant challenge. This study examines the protein expression of a large number of human STS, including subtype heterogeneity, using two-dimensional gel proteomics. In addition, detailed proteome profiles of...

CXCL12 encodes stromal cell-derived factor 1α (SDF-1), which binds to the receptor encoded by CXCR4. Variation at the CXCL12 locus is associated with coronary artery disease and endothelial progenitor cell numbers, whereas variation at the CXCR4 locus is associated with leukocyte telomere length, which has been shown to be associated with coronary artery disease. Therefore, we examined the relationships of plasma SDF-1 levels to cardiovascular disease (CVD)-related outcomes, risk factors,...

Telomere repeat binding factor 2 (TRF2) is a component of the shelterin complex that is known to bind and protect telomeric DNA, yet the detection of TRF2 in extra-telomeric regions of chromosomes suggests other roles for TRF2 besides telomere protection. Here, we demonstrate that TRF2 plays a critical role in antagonizing the repressive function of neuron-restrictive silencer factor, also known as repressor element-1 silencing transcription factor (REST), during the neural differentiation of...

Histone variant H3.3 is deposited in chromatin at active sites, telomeres, and pericentric heterochromatin by distinct chaperones, but the mechanisms of regulation and coordination of chaperone-mediated H3.3 loading remain largely unknown. We show here that the chromatin-associated oncoprotein DEK regulates differential HIRA- and DAAX/ATRX-dependent distribution of H3.3 on chromosomes in somatic cells and embryonic stem cells. Live cell imaging studies show that nonnucleosomal H3.3 normally...

Ageing is associated with an overall decline in the functional capacity of tissues and stem cells, including haematopoietic stem and progenitor cells (HSPCs), as well as telomere dysfunction. Dietary restriction (DR) is a recognised anti-ageing intervention that extends lifespan and improves health in several organisms. To investigate the role of telomeres and telomerase in haematopoietic ageing, we compared the HSPC profile and clonogenic capacity of bone marrow cells from wild type with...

Epidermal stem cells have been in clinical application as a source of culture-generated grafts. Although applications for such cells are increasing due to aging populations and the greater incidence of diabetes, current keratinocyte grafting technology is limited by immunological barriers and the time needed for culture amplification. We studied the feasibility of using human fetal skin cells for allogeneic transplantation and showed that fetal keratinocytes have faster expansion times, longer...

Telomeres consist of repetitive DNA-protein complexes that cap the ends of vertebrate linear chromosomes. Their capping function and dynamics both with regard to structure and length are carefully orchestrated by many regulatory mechanisms and factors, with likely more yet to be described. Telomere shortening has been shown to be a major measurable molecular characteristic of aging of cells in vitro and in vivo and is thought to have evolved as a tumor protection mechanism in long-lived species....

Telomerase expression in humans is restricted to different populations of stem and progenitor cells, being silenced in most somatic tissues. Efficient telomere homeostasis is essential for embryonic and adult stem cell function and therefore essential for tissue homeostasis throughout organismal life. Accordingly, the mutations in telomerase culminate in reduced stem cell function both in vivo and in vitro and have been associated with tissue dysfunction in human patients. Despite the importance...

Aplastic anemia is a disease in which the hematopoietic stem cell fails to adequately produce peripheral blood cells, causing pancytopenia. In some cases of acquired aplastic anemia and in inherited type of aplastic anemia, dyskeratosis congenita, telomere biology gene mutations and telomere shortening are etiologic. Telomere erosion hampers the ability of hematopoietic stem and progenitor cells to adequately replicate, clinically resulting in bone marrow failure. Additionally, telomerase...

Telomeres maintain chromosome stability and cell replicative capacity. Telomere shortening occurs concomitant with aging. Short telomeres are associated with some diseases, such as dyskeratosis congenita, idiopathic pulmonary fibrosis, and aplastic anemia. Telomeres are longer in pluripotent stem cells than in somatic cells and lengthen significantly during preimplantation development. Furthermore, telomere elongation during somatic cell reprogramming is of great importance in the acquisition of...

Neurogenesis continues throughout the lifetime in the hippocampus, while the rate declines with brain aging. It has been hypothesized that reduced neurogenesis may contribute to age-related cognitive impairment. Ginsenoside Rg1 is an active ingredient of Panax ginseng in traditional Chinese medicine, which exerts anti-oxidative and anti-aging effects. This study explores the neuroprotective effect of ginsenoside Rg1 on the hippocampus of the D-gal (D-galactose) induced aging rat model. Sub-acute...

The shoot apical meristem (SAM) acts as a reservoir for stem cells. The central zone (CZ) harbors stem cells. The stem cell progenitors differentiate in the adjacent peripheral zone and in the rib meristem located just beneath the CZ. The SAM is further divided into distinct clonal layers: the L1 epidermal, L2 sub-epidermal and L3 layers. Collectively, SAMs are complex structures that consist of cells of different clonal origins that are organized into functional domains. By employing...

Telomerase reverse transcriptase (TERT) is a key component of the telomerase complex. By lengthening telomeres in DNA strands, TERT increases senescent cell lifespan. Mice that lack TERT age much faster and exhibit age-related conditions such as osteoporosis, diabetes and neurodegeneration. Accelerated telomere shortening in both human and animal models has been documented in conditions associated with insulin resistance, including T2DM. We investigated the role of TERT, in regulating cellular...

Telomeres are repeated sequences (the hexanucleotide TTAGGG in vertebrates) located at chromosome ends of eukaryotes, protecting DNA from end joining or degradation. Telomeres become shorter with each cell cycle, but telomerase, a ribonucleoprotein complex, alleviates this attrition. The telomerase RNA component (TERC) is an essential element of telomerase, serving as a template for telomere elongation. The H/ACA domain of TERC is indispensable for telomere biogenesis. Mutations in the...

Recent evidence points to extra-telomeric, noncanonical roles for telomerase in regulating stem cell function. In this study, human embryonic stem cells (hESCs) were cultured in 20% or 2% O2 microenvironments for up to 5 days and evaluated for telomerase reverse transcriptase (TERT) expression and telomerase activity. Results showed increased cell survival and maintenance of the undifferentiated state with elevated levels of nuclear TERT in 2% O2-cultured hESCs despite no significant difference...

We have investigated the effects of hyperthermia (HT) on cell proliferation and telomerase activity of human hematopoietic stem cells (HSCs) and compared with human leukemic cell lines (TF-1, K562 and HL-60). The cells were exposed to HT at 42 and 43 °C up to 120 min. The cells were incubated at 37 °C for 96 h. Then the cells were collected and assayed for cell proliferation, viability, telomerase activity, and terminal restriction fragment (TRF) lengths. The enzyme activity from HSCs was...

Adult stem cells are characterised by longer telomeres compared to mature cells from the same tissue. In this study, candidate CD146 (+) umbilical cord (UC) mesenchymal stem cells (MSCs) were purified by cell sorting from UC tissue digests and their telomere lengths were measured in comparison to donor-matched CD146-negative fraction. UC tissue fragments were enzymatically treated with collagenase and the cells were used for cell sorting, colony-forming fibroblast (CFU-F) assay or for long-term...

Glioblastoma is the most prevalent primary brain tumor and is essentially universally fatal within 2 years of diagnosis. Glioblastomas contain cellular hierarchies with self-renewing glioblastoma stem cells (GSCs) that are often resistant to chemotherapy and radiation therapy. GSCs express high amounts of repressor element 1 silencing transcription factor (REST), which may contribute to their resistance to standard therapies. Telomere repeat-binding factor 2 (TRF2) stablizes telomeres and REST...

Aging is one of the contributing risk factors for kidney diseases. Accumulating evidence prompts the view that telomere length in kidney tissue cells is an indicator for organismal aging. Previously identified aging markers (cathelin-related antimicrobial peptide (CRAMP), stathmin, elongation factor-1α (EF-1α), and chitinase) were associated not only with telomere driven aging in mice but also with human aging and chronic diseases. This study focuses on the relationship between these...

Tissue homeostasis is maintained by balancing stem cell self-renewal and differentiation. How surrounding cells support this process has not been entirely resolved. Here we show that the chromatin and telomere-binding factor Without children (Woc) is required for maintaining the association of escort cells (ECs) with germ cells in adult ovaries. This tight association is essential for germline stem cell (GSC) differentiation into cysts. Woc is also required in larval ovaries for the association...

Mesenchymal stem cells (MSCs) senescence is an age-related process that impairs the capacity for tissue repair and compromises the clinical use of autologous MSCs for tissue regeneration. Here, we describe the effects of SIRT1, a NAD(+)-dependent deacetylase, on age-related MSCs senescence. Knockdown of SIRT1 in young MSCs induced cellular senescence and inhibited cell proliferation whereas overexpression of SIRT1 in aged MSCs reversed the senescence phenotype and stimulated cell proliferation....

Among diverse environmental factors that modify aging, diet has a profound effect. Calorie restriction (CR), which entails reduced calorie consumption without malnutrition, is the only natural regimen shown to extend maximum and mean lifespan, as well as healthspan in a wide range of organisms. Although the knowledge about the biological mechanisms underlying CR is still incipient, various approaches in biogerontology research suggest that CR can ameliorate hallmarks of aging at the cellular...

In human cancer, high expression of telomerase is correlated with tumor aggressiveness and metastatic potential. Human telomerase reverse transcriptase (hTERT), which regulates telomere length, can promote tumor development. Most research on hTERT has been focused on its crucial function of telomere maintenance. However, there are many phenomena that cannot be explained by its reverse transcriptase activity. Accumulating evidence suggests that hTERT has functions independent of its protective...

During recent years, it has become increasingly evident that donor leukemia following allogeneic transplant may be more common then realized in the past. We identified five cases of potential donor leukemia cases during past five years. The precise mechanism of the origin of such leukemias, however, remains poorly defined. In this short communication, we report a well documented case of donor-derived de novo acute myeloid leukemia (AML) that developed fourteen years after allogeneic stem cell...

Telomeres are repetitive sequences at the ends of chromosomes protected by DNA binding proteins of the shelterin complex that form capping structures. Through the interaction of shelterin complex-associated proteins, telomere length maintenance is regulated. Recently, the newly identified embryonic stem cell marker, Zinc finger and SCAN domain-containing 4 gene (Zscan4), was shown to be a telomere-associated protein, co-localizing to the shelterin complex. Furthermore, it was shown to play an...

Pluripotent or multipotent stem cells are involved in development and tissue homeostasis; they have the ability to self-renew and differentiate into various types of functional cells. To maintain these properties, stem cells must undergo sustained or unlimited proliferation that requires the stabilization of telomeres, which are essential for chromosome end protection. Telomerase, an RNA-dependent DNA polymerase, synthesizes telomeric DNA. Through the lengthening of telomeres the lifespans of...

Aging, a time-dependent functional decline of biological processes, is the primary risk factor in developing diseases such as cancer, cardiovascular or degenerative diseases. There is a real need to understand the human aging process in order to increase the length of disease-free life, also known as "health span". Accumulation of progerin and prelamin A are the hallmark of a group of premature aging diseases but have also been found during normal cellular aging strongly suggesting similar...

Telomere associations have been observed during key cellular processes such as mitosis, meiosis, and carcinogenesis and must be resolved before cell division to prevent genome instability. Here we establish that telomeric repeat-binding factor 1 (TRF1), a core component of the telomere protein complex, is a mediator of telomere associations in mammalian cells. Using live-cell imaging, we show that expression of TRF1 or yellow fluorescent protein (YFP)-TRF1 fusion protein above endogenous levels...

FEN1 has key roles in Okazaki fragment maturation during replication, long patch base excision repair, rescue of stalled replication forks, maintenance of telomere stability and apoptosis. FEN1 may be dysregulated in breast and ovarian cancers and have clinicopathological significance in patients. We comprehensively investigated FEN1 mRNA expression in multiple cohorts of breast cancer [training set (128), test set (249), external validation (1952)]. FEN1 protein expression was evaluated in 568...

Telomere attrition and genomic instability are associated with organism aging. Concerns still exist regarding telomere length resetting in cloned embryos and ntES cells, and possibilities of premature aging of cloned animals achieved by somatic cell nuclear transfer (SCNT). Trichostatin A (TSA), a histone deacetylase inhibitor, effectively improves the developmental competence of cloned embryos and animals, and recently contributes to successful generation of human ntES cells by SCNT. To test...

Cryopreservation is the only method for long-term storage of viable cells and tissues used for cellular therapy, stem cell transplantation and/or tissue engineering. However, the freeze-thaw process strongly contributes to cell and tissue damage through several mechanisms, including oxidative stress, cell injury from intracellular ice formation and altered physical cellular properties. Our previous proteomics investigation was carried out on Wharton's Jelly Stem Cells (WJSCs) having similar...

Telomeres are nucleoprotein complexes that cap the ends of all linear chromosomes and function to prevent aberrant repair and end-to-end chromosome fusions. In somatic cells, telomere shortening is a natural part of the aging process as it occurs with each round of cell division. In germ and stem cells, however, the enzyme telomerase synthesizes telomere DNA to counter-balance telomere shortening and help maintain cellular proliferation. Of the primary telomere end-binding proteins, TPP1 has...

The somatic mutation burden in healthy white blood cells (WBCs) is not well known. Based on deep whole-genome sequencing, we estimate that approximately 450 somatic mutations accumulated in the nonrepetitive genome within the healthy blood compartment of a 115-yr-old woman. The detected mutations appear to have been harmless passenger mutations: They were enriched in noncoding, AT-rich regions that are not evolutionarily conserved, and they were depleted for genomic elements where mutations...

It has been shown that bone marrow mesenchymal stromal cells (MSCs) from patients with myelodysplastic syndromes (MDSs) display defective proliferative potential. We have probed the impaired replicative capacity of culture-expanded MSCs in MDS patients (n=30) compared with healthy subjects (n=32) by studying senescence characteristics and gene expression associated with WNT/transforming growth factor-β1 (TGFB1) signaling pathways. We have also explored the consequences of the impaired patient...

The NAD-dependent deacetylase SIRT1 is involved in chromatin silencing and genome stability. Elevated SIRT1 levels in embryonic stem cells also suggest a role for SIRT1 in pluripotency. Murine SIRT1 attenuates telomere attrition in vivo and is recruited at telomeres in induced pluripotent stem cells (iPSCs). Because telomere elongation is an iPSC hallmark, we set out to study the role of SIRT1 in pluripotency in the setting of murine embryonic fibroblasts reprogramming into iPSCs. We find that...

Telomere length homeostasis is essential for genomic stability and unlimited self-renewal of embryonic stem cells (ESCs). We show that telomere-associated protein Rif1 is required to maintain telomere length homeostasis by negatively regulating Zscan4 expression, a critical factor for telomere elongation by recombination. Depletion of Rif1 results in terminal hyperrecombination, telomere length heterogeneity, and chromosomal fusions. Reduction of Zscan4 by shRNA significantly rescues telomere...

TRF2 is a component of shelterin, the protein complex that protects the ends of mammalian chromosomes. TRF2 is essential for telomere capping owing to its roles in suppressing an ATM-dependent DNA damage response (DDR) at chromosome ends and inhibiting end-to-end chromosome fusions. Mice deficient for TRF2 are early embryonic lethal. However, the role of TRF2 in later stages of development and in the adult organism remains largely unaddressed, with the exception of liver, where TRF2 was found to...

Reactivation of the endogenous telomerase reverse transcriptase (TERT) catalytic subunit and telomere elongation occur during the reprogramming of somatic cells to induced pluripotent stem (iPS) cells. However, the role of TERT in the reprogramming process is unclear. To clarify its function, the reprogramming process was examined in TERT-KO somatic cells. To exclude the effect of telomere elongation, tail-tip fibroblasts (TTFs) from first generation TERT-KO mice were used. Although iPS cells...

miR-34a has been identified as a tumor suppressor in several tumors, but its involvement in gallbladder cancer (GBC) has not been reported. In this study, the miR-34a level and telomere length were measured in 77 gallbladder adenocarcinomas and 36 peritumoral tissues by real-time PCR. Forced miR-34a expression was established by an adenovirus carrying a miR-34a expression cassette. The colony-forming ability of isolated CD44+CD133+ GBC tumor stem-like cells was measured by matrigel colony assay....

The telomere capping protein TRF1 is a component of the multiprotein complex "shelterin," which organizes the telomere into a high order structure. Besides telomere maintenance, telomere-associated proteins also have nontelomeric functions. For example, tankyrase 1 and TRF1 are required for the maintenance of faithful mitotic progression. However, the functional relevance of their centrosomal localization has not been established. Here, we report the identification of a TRF1-binding protein,...

Advances in medical science and technology allow people live longer lives, which results in age-related problems. Humans cannot avoid the various aged-related alterations of aging; in other words, humans cannot remain young at molecular and cellular levels. In 1956, Harman proposed the "free radical theory of aging" to explain the molecular mechanisms of aging. Telomere length, and accumulation of DNA or mitochondrial damage are also considered to be mechanisms of aging. On the other hand, stem...

Mapping genome-wide data to human subtelomeres has been problematic due to the incomplete assembly and challenges of low-copy repetitive DNA elements. Here, we provide updated human subtelomere sequence assemblies that were extended by filling telomere-adjacent gaps using clone-based resources. A bioinformatic pipeline incorporating multiread mapping for annotation of the updated assemblies using short-read data sets was developed and implemented. Annotation of subtelomeric sequence features as...

Werner syndrome (WS) patients exhibit premature aging predominantly in mesenchyme-derived tissues, but not in neural lineages, a consequence of telomere dysfunction and accelerated senescence. The cause of this lineage-specific aging remains unknown. Here, we document that reprogramming of WS fibroblasts to pluripotency elongated telomere length and prevented telomere dysfunction. To obtain mechanistic insight into the origin of tissue-specific aging, we differentiated iPSCs to mesenchymal stem...

The etiology of endometriosis remains poorly understood but circulating stem cells may contribute. Telomeres shorten with cell divisions and age. Stem cells attempt to compensate for telomere attrition through the action of telomerase. Since circulating stem cells may contribute to endometriosis, we compared telomere content in lymphocytes of patients with and without endometriosis....

The chromatin remodeling protein ATRX, which targets tandem repetitive DNA, has been shown to be required for expression of the alpha globin genes, for proliferation of a variety of cellular progenitors, for chromosome congression and for the maintenance of telomeres. Mutations in ATRX have recently been identified in tumours which maintain their telomeres by a telomerase independent pathway involving homologous recombination thought to be triggered by DNA damage. It is as yet unknown whether...

Telomeres are genomic structures that reflect both mitotic history and biochemical trauma to the genome. Metals inherent in fine particulate matter (PM(2.5)) were shown to be genotoxic via oxidative damage. However, few studies investigated the induction time of cumulative PM(2.5) exposure on telomere length in a longitudinal setting. Therefore, the purpose of this study was to assess the association between occupational PM(2.5) exposure in various time windows and telomere length. The study...

Aplastic anemia is a heterogeneous disorder of bone marrow failure syndrome. Accumulating evidence indicates that both acquired and congenital aplastic anemia is linked to telomerase activity and telomere length. Chinese herbal medicine Tianshengyuan-1 (TSY-1), a liquid extraction of multiple Chinese herbs, appears to stimulate hematopoiesis in patients with bone marrow deficiencies; however, the exact mechanism of action remains unclear. In this study, we investigated the effect of TSY-1 on...

Exposure to total body irradiation (TBI) induces not only acute hematopoietic radiation syndrome but also long-term or residual bone marrow (BM) injury. This residual BM injury is mainly attributed to permanent damage to hematopoietic stem cells (HSCs), including impaired self-renewal, decreased long-term repopulating capacity, and myeloid skewing. These HSC defects were associated with significant increases in production of reactive oxygen species (ROS), expression of p16(Ink4a) (p16) and Arf...

Therapeutic use of multipotent mesenchymal stromal stem cells (MSC) is a promising venue for a large number of degenerative diseases and cancer. Their availability from many different adult tissues, ease of expansion in culture, the ability to avoid immune rejection and their homing ability, are some of the properties of MSCs that make them a great resource for therapy. However, the challenges and risks for cell-based therapies are multifaceted. The blessing of cell culture expansion also comes...

Telomere biology is frequently associated with disease evolution in human cancer and dysfunctional telomeres have been demonstrated to contribute to genetic instability. In BCR-ABL(+) chronic myeloid leukemia (CML), accelerated telomere shortening has been shown to correlate with leukemia progression, risk score and response to treatment. Here, we demonstrate that proliferation of murine CML-like bone marrow cells strongly depends on telomere maintenance. CML-like cells of telomerase knockout...

Authors: Yu Y. Yin, Na N. Liu, Xiaoying X. Ye, Renpeng R. Guo, Jie J. Hao, Fang F. Wang, Lin L. Liu Published: 03/03/2014, Protein & cell PubMed Full Text...

Telomere shortening and telomerase deficiency have been linked with several age related degenerative diseases. Moreover, degenerative changes in various tissues/organs have been attributed to derangement of stem cell functions causing regenerative tragedy. Bone marrow stromal cells (BMSCs) are considered the ideal candidates for regenerative approaches owing to their beneficial effects in numerous clinical applications. Thus, the effect of telomerase deficiency in perpetrating age related...

Telomeres protect and cap linear chromosome ends, yet these genomic buffers erode over an organism's lifespan. Short telomeres have been associated with many age-related conditions in humans, and genetic mutations resulting in short telomeres in humans manifest as syndromes of precocious aging. In women, telomere length limits a fertilized egg's capacity to develop into a healthy embryo. Thus, telomere length must be reset with each subsequent generation. Although telomerase is purportedly...

Telomerase is the enzyme responsible for the maintenance of telomere length by adding guanine-rich repetitive sequences. Its activity can be seen in gametes, stem cells and tumor cells. In human somatic cells the proliferative potential is limited, reaching senescence after 50-70 cell divisions, because the DNA polymerase is not able to copy the DNA at the ends of chromosomes. By contrast, in most tumor cells the replicative potential is unlimited due to the maintenance of the telomeric length...

Pluripotent stem cells (PSCs) have the potential to produce any types of cells from all three basic germ layers and the capacity to self-renew and proliferate indefinitely in vitro. The two main types of PSCs, embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), share common features such as colony morphology, high expression of Oct4 and Nanog, and strong alkaline phosphatase activity. In recent years, increasing evidences suggest that telomere length represents another...

Human telomeric regions are packaged as constitutive heterochromatin, characterized by extensive subtelomeric DNA methylation and specific histone modifications. ICF (immunodeficiency, centromeric instability, facial anomalies) type I patients carry mutations in DNA methyltransferase 3B (DNMT3B) that methylates de novo repetitive sequences during early embryonic development. ICF type I patient fibroblasts display hypomethylated subtelomeres, abnormally short telomeres and premature senescence....

Chromosome ends are protected by telomeres that prevent DNA damage response and degradation. Telomerase expression extends telomeres and inhibits DNA damage response. Telomeres are also maintained by the recombination-based alternative lengthening pathway. Telomerase is believed to be the sole mechanism for telomere maintenance in the epidermis. We show that basal cells in the epidermis maintain telomeres both by telomerase and alternative lengthening of telomere (ALT) mechanisms in vivo. ALT...

Epidemiological and experimental studies indicate that early vascular dysfunction occurs in low-birth-weight subjects, especially preterm (PT) infants. We recently reported impaired angiogenic activity of endothelial colony-forming cells (ECFCs) in this condition. We hypothesized that ECFC dysfunction in PT might result from premature senescence and investigated the underlying mechanisms. Compared with ECFCs from term neonates (n = 18), ECFCs isolated from PT (n = 29) display an accelerated...

Dyskeratosis congenita (DC) is an inherited disorder with mutations affecting telomerase or telomeric proteins. DC patients usually die of bone marrow failure. Here we show that genetic depletion of the telomerase RNA component (TR) in the zebrafish results in impaired myelopoiesis, despite normal development of haematopoietic stem cells (HSCs). The neutropenia caused by TR depletion is independent of telomere length and telomerase activity. Genetic analysis shows that TR modulates the...

Human aging is associated with DNA methylation changes at specific sites in the genome. These epigenetic modifications may be used to track donor age for forensic analysis or to estimate biological age....

Transchromosomic (Tc) technology using human chromosome fragments (hCFs), or human artificial chromosomes (HACs), has been used for generating mice containing Mb-sized segments of the human genome. The most significant problem with freely segregating chromosomes with human centromeres has been mosaicism, possibly due to the instability of hCFs or HACs in mice. We report a system for the stable maintenance of Mb-sized human chromosomal fragments following translocation to mouse chromosome 10...

Clinical studies suggest that hypercholesterolemia may cause ageing in hematopoietic stem cells (HSCs) because ageing-associated alterations were found in peripheral blood cells and their bone marrow residing precursors in patients with advanced atherosclerosis. We hypothesized that hypercholesterolemia induces oxidant stress in hematopoietic stems cells that accelerates their ageing....

The progressive bone marrow failure syndrome dyskeratosis congenita (DC) is often caused by mutations in telomerase or the factors involved in telomerase biogenesis and trafficking. However, a subset of DC patients is heterozygous for mutations in the shelterin component TIN2. To determine how the TIN2-DC mutations affect telomere function, we generated mice with the equivalent of the TIN2 K280E DC allele (TIN2(DC)) by gene targeting. Whereas homozygous TIN2(DC/DC) mice were not viable,...

Pluripotent stem cells (PSCs) must maintain their proper genomic content in order to preserve appropriate self-renewal and differentiation capacities. However, their prolonged in vitro propagation, as well as the environmental culture conditions, present serious challenges to genome maintenance. Recent work has been focused on potential means to alleviate the genomic insults experienced by PSCs, and to detect them as soon as they arise, in order to prevent the detrimental consequences of these...

Carcinogenesis is a multistep process involving alterations in various cellular pathways. The critical genetic events driving the evolution of primary liver cancer, specifically hepatoblastoma and hepatocellular carcinoma (HCC), are still poorly understood. However, telomere stabilization is acknowledged as prerequisite for cancer progression in humans. In this project, human fetal hepatocytes were utilized as a cell culture model for untransformed, proliferating human liver cells, with...

Aplastic anemia (AA) is a disease characterized by pancytopenia and hypoplastic bone marrow caused by the decrease of hematopoietic stem cells. The pathogenesis of AA is complex and involves an abnormal hematopoietic microenvironment, hematopoietic stem cell/progenitor cell deficiencies and immunity disorders. Survival in severe aplastic anemia (SAA) has markedly improved in the past 4 decades because of advances in hematopoietic stem cell transplantation, immunosuppressive and biologic drugs,...

Leukemia stem cells (LSCs) play important roles in leukemia initiation, progression and relapse, and thus represent a critical target for therapeutic intervention. Hence, it is extremely urgent to explore new therapeutic strategies directly targeting LSCs for acute myelogenous leukemia (AML) therapy. We show here that Angelica sinensis polysaccharide (ASP), a major active component in Dong quai (Chinese Angelica sinensis), effectively inhibited human AML CD34+CD38? cell proliferation in vitro...

Telomerase reverse transcriptase (TERT) is the protein component of telomerase and combined with an RNA molecule, telomerase RNA component, forms the telomerase enzyme responsible for telomere elongation. Telomerase is essential for maintaining telomere length from replicative attrition and thus contributes to the preservation of genome integrity. Although diverse mouse models have been developed and studied to prove the physiological roles of telomerase as a telomere- elongating enzyme, recent...

High telomerase activity is a characteristic of human embryonic stem cells (hESCs), however, the regulation and maintenance of correct telomere length in hESCs is unclear. In this study we investigated telomere elongation in hESCs in vitro and found that telomeres lengthened from their derivation in blastocysts through early expansion, but stabilized at later passages. We report that the core unit of telomerase, hTERT, was highly expressed in hESCs in blastocysts and throughout long-term...

The shelterin complex plays dual functions in telomere homeostasis by recruiting telomerase and preventing the activation of a DNA damage response at telomeric ends. Somatic stem cells require telomerase activity, as evidenced by progressive stem cell loss leading to bone marrow failure in hereditary dyskeratosis congenita. Recent work demonstrates that dyskeratosis congenita can also arise from mutations in specific shelterin genes, although little is known about shelterin functions in somatic...

The maintenance of human telomeres requires the ribonucleoprotein enzyme telomerase, which is composed of telomerase reverse transcriptase (TERT), telomerase RNA component, and several additional proteins for assembly and activity. Telomere elongation by telomerase in human cancer cells involves multiple steps including telomerase RNA biogenesis, holoenzyme assembly, intranuclear trafficking, and telomerase recruitment to telomeres. Although telomerase has been shown to accumulate in Cajal...

Although somatic cell nuclear transfer (SCNT) and induction of pluripotency (to form iPSCs) are both recognized reprogramming methods, there has been relatively little comparative analysis of the resulting pluripotent cells. Here, we examine the capacity of these two reprogramming approaches to rejuvenate telomeres using late-generation telomerase-deficient (Terc(-/-)) mice that exhibit telomere dysfunction and premature aging. We found that embryonic stem cells established from Terc(-/-) SCNT...

Telomeres are critical in maintaining genomic stability and integrity, and telomerase expression in spermatogonial stem cells is responsible for the maintenance of telomere length in the human male germline. Genetic variants in telomere-associated pathway genes might affect telomere length and chromosomal stability, and subsequently disease susceptibility. Thus, we hypothesize that single nucleotide polymorphisms (SNPs) in this pathway could contribute to male infertility risk. In a case-control...

The efficacy of bypass surgery in patients with ischemic cardiomyopathy is not easily predictable; preoperative clinical conditions may be similar, but the outcome may differ significantly. We hypothesized that the growth reserve of cardiac stem cells (CSCs) and circulating cytokines promoting CSC activation are critical determinants of ventricular remodeling in this patient population....

Hypoxia favors stem cell quiescence, whereas normoxia is required for stem cell activation, but whether cardiac stem cell (CSC) function is regulated by the hypoxic/normoxic state of the cell is currently unknown....

Cell therapies utilizing mesenchymal stem cells (MSCs) could overcome limitations of traditional treatments for reconstructing craniofacial tissues. This large-scale study explored a standardized methodology for the isolation and clinical-scale expansion of alveolar bone marrow-derived MSCs (aBMSCs). We harvested 103 alveolar bone marrow samples from 45 patients using 1 of 3 standardized methodologies. Following aBMSC isolation, cells were characterized through cell-surface marker expression and...

The fate of cultivated primary hematopoietic stem cells (HSCs) with respect to genetic instability and telomere attrition has not yet been described in great detail. Thus, knowledge of the genetic constitution of HSCs is important when interpreting results of HSCs in culture. While establishing a cell culture model for myelodysplastic syndrome with a deletion in 5q by performing RPS14 knockdown, we found surprising data that may be of importance for any CD34+ cell culture experiments. We...

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...

DNA damage at the base sequence and chromosome level is a fundamental cause of developmental and degenerative diseases. Multiple micronutrients and their interactions with the inherited and/or acquired genome determine DNA damage and genomic instability rates. The challenge is to identify for each individual the combination of micronutrients and their doses (i.e. the nutriome) that optimises genome stability, including telomere integrity and functionality and DNA repair. Using nutrient array...

The incidence of skin cancer is increasing worldwide and cutaneous squamous cell carcinomas (SCCs) are associated with considerable morbidity and mortality, particularly in immunosuppressed individuals ('carcinomatous catastrophy'). Yet, molecular mechanisms are still insufficiently understood. Besides ultraviolet (UV)-indicative mutations, chromosomal aberrations are prominent. As telomeres are essential in preserving chromosome integrity, and telomere erosion as well as aberrant spatial...

Telomeres are located at the ends of all eukaryotic chromosomes and protect them from deleterious events such as inappropriate DNA repair, illegitimate recombination or improper segregation of the chromosomes during mitotic or meiotic divisions. However, telomeres gradually shorten primarily due to successive rounds of genomic DNA replication and also as the result of the adverse effects of oxidative stress, genotoxic agents, diseases related to ageing and environmental factors on the nuclear...

The occurrence of clonal perturbations and leukemia in patients transplanted with gamma-retroviral (RV) vector-transduced autologous hematopoietic stem and progenitor cells (HSPCs) has stimulated extensive investigation, demonstrating that proviral insertions may perturb adjacent proto-oncogene expression. Although enhancer-deleted lentiviruses are less likely to result in insertional oncogenesis, there is evidence that they may perturb transcript splicing, and one patient with a benign clonal...

Human bone marrow-derived mesenchymal stem cells (MSCs) have limited growth potential in vitro and cease to divide due to replicative senescence, which from a tissue-engineering perspective has practical implications, such as defining the correct starting points for differentiation and transplantation. Time spent in culture before the loss of required differentiation potential is different and reflects patient variability, which is a problem for cell expansion. This study aimed to develop a...

In the field of cell-based therapy and regenerative medicine, clinical application is the ultimate goal. However, one major concern is: does in vitro manipulation during culture expansion increases tumourigenicity risk on the prepared cells? Therefore, the aim of this study was to investigate the effect of long-term in vitro expansion on human adipose-derived stem cells (ASCs). The ASCs were harvested from lipo-aspirate samples and cultured until passage 20 (P20), using standard culture...