Telomere length, aging, and somatic cell turnover

A pathological convergence theory for non-communicable diseases

The current paradigm considers the study of non-communicable diseases (NCDs), which are the main causes of mortality, as individual disorders. Nevertheless, this conception is being solidly challenged by numerous remarkable studies. The clear fact that the mortality, by virtually all NCDs, tends to cluster at old ages (with the exception of congenital malformations and certain types of cancer, among a few others); makes us intuitive to assume that the common convergence mechanism that exponentially increases mortality by almost all NCDs in older ages is cell aging. Moreover, when we study NCDs, we are not analyzing which disorders cause the mortality of the populations, rather that which disorders kill us before others do, because the aging of the individuals causes inevitably their death by one cause or another. This is not a defeatist perspective, but a challenging and efficient one. These intuitive assumptions have been supported by studies from the pathophysiologic, epidemiologic, and genetic fields, leading to the affirmation that, as NCDs share genetic and pathophysiological mechanisms (derived from mostly the same risk factors), they should no longer be considered independently. Those studies should make us reconsider our current conceptions of studying NCDs as individual disorders, and to hypothesize about a paradigm that would consider most NCDs (cancer, neurological pathologies, cardiovascular diseases, type II diabetes mellitus, chronic respiratory diseases, osteoarthritis, and osteoporosis, among others) different manifestations of the same process: the cell aging.

Associations Between Children's Telomere Length, Parental Intrusiveness, and the Development of Early Externalizing Behaviors

Shorter telomeres mark cellular aging and are linked to chronic stress exposure as well as negative physical and psychological outcomes. However, it is unclear whether telomere length mediates associations between early stress exposure and later externalizing problems, or whether boys and girls differ in pathways to these concerns. We therefore examined associations between telomere length, early stress via negative caregiving, and children's externalizing symptom development over time in 409 three-year-old children and their parents. Telomere length mediated the association between early parental intrusiveness and later rule-breaking behavior; however, this association was moderated by children's biological sex such that parent intrusiveness was related only to boys' rule-breaking. Findings support the notion that children's telomere length may mark individual differences in responses to negative early caregiving, and highlight a potential mechanism contributing to the development of rule-breaking problems in boys.

Growing and aging of hematopoietic stem cells

In the hematopoietic system, a small number of stem cells produce a progeny of several distinct lineages. During ontogeny, they arise in the aorta-gonad-mesonephros region of the embryo and the placenta, afterwards colonise the liver and finally the bone marrow. After this fetal phase of rapid expansion, the number of hematopoietic stem cells continues to grow, in order to sustain the increasing blood volume of the developing newborn, and eventually reaches a steady-state. The kinetics of this growth are mirrored by the rates of telomere shortening in leukocytes. During adulthood, hematopoietic stem cells undergo a very small number of cell divisions. Nonetheless, they are subjected to aging, eventually reducing their potential to produce differentiated progeny. The causal relationships between telomere shortening, DNA damage, epigenetic changes, and aging have still to be elucidated.

Photobiomodulation with 590 nm Wavelength Delays the Telomere Shortening and Replicative Senescence of Human Dermal Fibroblasts In Vitro

Background: Cellular senescence is one of the major factors contributing to the aging process. Photobiomodulation (PBM) is known to trigger an array of cellular responses, but there are no data on how it affects the process of cellular senescence. In this study, we analyze the effect of PBM on the cellular senescence and telomere dynamics. Methods: Human dermal fibroblasts were irradiated by a panel of light-emitting diodes with 590 nm and dose 30 J/cm² accumulated over 1200 sec repeated in 4-day cycle within 40 days. After the last cycle of PBM treatment, the difference in number of senescent cells between PBM treated groups end nontreated control groups was measured by senescent sensitive β-galactosidase assay, and the difference in average telomere length between the experimental end control groups was analyzed using relative human telomere length quantitative Polymerase Chain Reaction (qPCR) assay. Results: After 10 cycles of irradiation, the percentage of senescent cells in PBM-treated cultures was 19.7% ± 4.5%, p < 0.05 smaller than the percentage of senescent cells in the control group, and their relative telomere length was 1.19 ± 0.09-fold, p < 0.05 greater than nontreated controls. Conclusions: Our study demonstrates for the first time that PBM with appropriate parameters can delay the attrition of the telomeres and the entry of cells into senescence, suggesting a potential involvement of telomerase reactivation. A hypothetical mechanism for this light-induced antiaging effect is discussed.

Contributions of Age-Related Thymic Involution to Immunosenescence and Inflammaging

Immune system aging is characterized by the paradox of immunosenescence (insufficiency) and inflammaging (over-reaction), which incorporate two sides of the same coin, resulting in immune disorder. Immunosenescence refers to disruption in the structural architecture of immune organs and dysfunction in immune responses, resulting from both aged innate and adaptive immunity. Inflammaging, described as a chronic, sterile, systemic inflammatory condition associated with advanced age, is mainly attributed to somatic cellular senescence-associated secretory phenotype (SASP) and age-related autoimmune predisposition. However, the inability to reduce senescent somatic cells (SSCs), because of immunosenescence, exacerbates inflammaging. Age-related adaptive immune system deviations, particularly altered T cell function, are derived from age-related thymic atrophy or involution, a hallmark of thymic aging. Recently, there have been major developments in understanding how age-related thymic involution contributes to inflammaging and immunosenescence at the cellular and molecular levels, including genetic and epigenetic regulation, as well as developments of many potential rejuvenation strategies. Herein, we discuss the research progress uncovering how age-related thymic involution contributes to immunosenescence and inflammaging, as well as their intersection. We also describe how T cell adaptive immunity mediates inflammaging and plays a crucial role in the progression of age-related neurological and cardiovascular diseases, as well as cancer. We then briefly outline the underlying cellular and molecular mechanisms of age-related thymic involution, and finally summarize potential rejuvenation strategies to restore aged thymic function.

The Dietary Inflammatory Index® and Alternative Healthy Eating Index 2010 in relation to leucocyte telomere length in postmenopausal women: a cross-sectional study

Telomeres are nucleoprotein complexes that form the ends of eukaryotic chromosomes where they protect DNA from genomic instability, prevent end-to-end fusion and limit cellular replicative capabilities. Increased telomere attrition rates, and relatively shorter telomere length, is associated with genomic instability and has been linked with several chronic diseases, malignancies and reduced longevity. Telomeric DNA is highly susceptible to oxidative damage and dietary habits may make an impact on telomere attrition rates through the mediation of oxidative stress and chronic inflammation. The aim of this study was to examine the association between leucocyte telomere length (LTL) with both the Dietary Inflammatory Index^® 2014 (DII^®) and the Alternative Healthy Eating Index 2010 (AHEI-2010). This is a cross-sectional analysis using baseline data from 263 postmenopausal women from the Alberta Physical Activity and Breast Cancer Prevention (ALPHA) Trial, in Calgary and Edmonton, Alberta, Canada. No statistically significant association was detected between LTL z-score and the AHEI-2010 (P = 0·20) or DII^® (P = 0·91) in multivariable adjusted models. An exploratory analysis of AHEI-2010 and DII^® parameters and LTL revealed anthocyanidin intake was associated with LTL (P < 0·01); however, this association was non-significant after a Bonferroni correction was applied (P = 0·27). No effect modification by age, smoking history, or recreational physical activity was detected for either relationship. Increased dietary antioxidant and decreased oxidant intake were not associated with LTL in this analysis.

Molecular and Cellular Bases of Immunosenescence, Inflammation, and Cardiovascular Complications Mimicking "Inflammaging" in Patients with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an archetype of systemic autoimmune disease, characterized by the presence of diverse autoantibodies and chronic inflammation. There are multiple factors involved in lupus pathogenesis, including genetic/epigenetic predisposition, sexual hormone imbalance, environmental stimulants, mental/psychological stresses, and undefined events. Recently, many authors noted that "inflammaging", consisting of immunosenescence and inflammation, is a common feature in aging people and patients with SLE. It is conceivable that chronic oxidative stresses originating from mitochondrial dysfunction, defective bioenergetics, abnormal immunometabolism, and premature telomere erosion may accelerate immune cell senescence in patients with SLE. The mitochondrial dysfunctions in SLE have been extensively investigated in recent years. The molecular basis of normoglycemic metabolic syndrome has been found to be relevant to the production of advanced glycosylated and nitrosative end products. Besides, immunosenescence, autoimmunity, endothelial cell damage, and decreased tissue regeneration could be the results of premature telomere erosion in patients with SLE. Herein, the molecular and cellular bases of inflammaging and cardiovascular complications in SLE patients will be extensively reviewed from the aspects of mitochondrial dysfunctions, abnormal bioenergetics/immunometabolism, and telomere/telomerase disequilibrium.

Genetic reprogramming of somatic cells into neuroblasts through a co-induction of the doublecortin gene along the Yamanaka factors: A promising approach to model neuroregenerative disorders

Neural stem cell (NSC) mediated adult neurogenesis represents the regenerative plasticity of the brain. The functionality of the neurogenic process appears to be operated by neuroblasts, the multipotent immature neuronal population of the adult brain. While neuroblasts have been realized to play a major role in synaptic remodeling and immunogenicity, neurodegenerative disorders have been characterized by failure in the terminal differentiation, maturation, integration and survival of newborn neuroblasts. Advancement in understanding the impaired neuroregenerative process along the neuropathological conditions has currently been limited by lack of an appropriate experimental model of neuroblasts. The genetic reprogramming of somatic cells into pluripotent state offers a potential strategy for the experimental modeling of brain disorders. Thus, the induced pluripotent stem cell (iPSC) based direct reprogramming of somatic cells into neuroblasts would represent a potential tool to understand the regenerative biology of the adult brain. Therefore, this concise article discusses the significance of iPSCs, the functional roles of neuroblasts in the adult brain and provides a research hypothesis for the direct reprogramming of somatic cells into neuroblasts through the co-induction of a potential proneurogenic marker, the doublecortin (DCX) gene along with the Yamanaka factors. The proposed cellular model of adult neurogenesis may provide us with further insights into neuropathogenesis of many neurodegenerative disorders and will provide a potential experimental platform for diagnostic, drug discovery and regenerative therapeutic strategies.

Modeling large fluctuations of thousands of clones during hematopoiesis: The role of stem cell self-renewal and bursty progenitor dynamics in rhesus macaque

In a recent clone-tracking experiment, millions of uniquely tagged hematopoietic stem cells (HSCs) and progenitor cells were autologously transplanted into rhesus macaques and peripheral blood containing thousands of tags were sampled and sequenced over 14 years to quantify the abundance of hundreds to thousands of tags or “clones.” Two major puzzles of the data have been observed: consistent differences and massive temporal fluctuations of clone populations. The large sample-to-sample variability can lead clones to occasionally go “extinct” but “resurrect” themselves in subsequent samples. Although heterogeneity in HSC differentiation rates, potentially due to tagging, and random sampling of the animals’ blood and cellular demographic stochasticity might be invoked to explain these features, we show that random sampling cannot explain the magnitude of the temporal fluctuations. Moreover, we show through simpler neutral mechanistic and statistical models of hematopoiesis of tagged cells that a broad distribution in clone sizes can arise from stochastic HSC self-renewal instead of tag-induced heterogeneity. The very large clone population fluctuations that often lead to extinctions and resurrections can be naturally explained by a generation-limited proliferation constraint on the progenitor cells. This constraint leads to bursty cell population dynamics underlying the large temporal fluctuations. We analyzed experimental clone abundance data using a new statistic that counts clonal disappearances and provided least-squares estimates of two key model parameters in our model, the total HSC differentiation rate and the maximum number of progenitor-cell divisions.

Hematopoiesis of virally tagged cells in rhesus macaques is analyzed in the context of a mechanistic and statistical model. We find that the clone size distribution and the temporal variability in the abundance of each clone (viral tag) in peripheral blood are consistent with (i) stochastic HSC self-renewal during bone marrow repair, (ii) clonal aging that restricts the number of generations of progenitor cells, and (iii) infrequent and small-size samples. By fitting data, we infer two key parameters that control the level of fluctuations of clone sizes in our model: the total HSC differentiation rate and the maximum proliferation capacity of progenitor cells. Our analysis provides insight into the mechanisms of hematopoiesis and a framework to guide future multiclone barcoding/lineage tracking measurements.

Low estrogen levels and obesity are associated with shorter telomere lengths in pre- and postmenopausal women

The aim of this study was to determine whether there is an association between leukocyte telomere length (LTL), and estrogen level, oxidative stress, cardiovascular disease (CVD) risk factors, and cardiorespiratory fitness (CRF) in pre- and postmenopausal obese women. Fifty-four obese women (premenopausal, n=25; postmenopausal, n=29) were selected to participate in this study. The outcome measurements in the pre- and postmenopausal groups were compared using independent t-tests and Pearson correlation analysis. The estrogen level (P<0.001), LTL (P<0.05), high-density lipoprotein level (P<0.05), and CRF (P<0.001) were higher in premenopausal women than in postmenopausal women. The body fat percentage (P<0.05) and triglyceride concentration (P<0.05) were lower in premenopausal women than in postmenopausal women. There were no significant associations between LTL, CVD risk, CRF, and oxidative stress and antioxidant enzyme activity in pre-menopausal women. The body mass index (BMI) and body fat percent-age in postmenopausal women were negatively associated with LTL (P<0.05). When all women were considered (i.e., both pre- and post-menopause), the BMI, percentage of fat, and waist circumference had a negative association with LTL (P<0.05), and estrogen levels were positively associated with LTL (P<0.05). Decreased estrogen levels after menopause, a pivotal factor in the biology of aging, and obesity were more associated with shorter telomere lengths in pre- and postmenopausal women than aerobic capacity and other CVD risk factors.

Pretreatment levels of serum osteoprotegerin and p53 protein and urine telomerase as prognostic factors affecting survival in Egyptian bladder cancer patients

A non-invasive marker is required for the diagnosis and follow-up of patients with bladder cancer. The aim of the current study was to evaluate the potential prognostic significance of serum osteoprotegerin (OPG), p53 protein and urine telomerase in patients with bladder cancer. For all patients, serum levels of OPG and p53 protein were determined using enzyme-linked immunosorbent assay (ELISA), and urine telomerase was assessed using a polymerase chain reaction ELISA technique. Patients were assigned into group 1 (cystectomy and adjuvant radiotherapy) or group 2 (transurethral resection and chemoradiotherapy). The results revealed that serum OPG and p53, and urine telomerase levels were significantly higher in bladder cancer patients compared with in healthy individuals (P<0.0001). High serum OPG was associated with significantly lower overall survival and disease-free survival rates (both P=0.001), and was correlated with advanced tumor stages (P<0.0001), high tumor grades (P<0.0001) and the occurrence of disease relapse (P=0.001). Serum p53 and urine telomerase did not demonstrate prognostic significance. These findings indicate that serum OPG level may be used as a diagnostic tool and a prognostic variable for patients with muscle invasive bladder cancer. Future trials are required to elucidate its therapeutic role in such patients.

Senescence as a general cellular response to stress: A mini-review

Cellular senescence was initially described as the phenomenon of limited cell divisions that normal cells in culture can undergo during long-term-cultivation. Later it was found that senescence may be induced by various stress factors. The intriguing resemblance between stress-induced and replicative senescence makes questionable the distinction between both types and suggests that the cellular senescence is a common outcome of stress response. Growing evidences support the idea that stress-induced senescence is the cell-type specific.

A shorter telomere is the key factor in preventing cultured human mesenchymal stem cells from senescence escape

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 transformation in vitro is well defined.It was demonstrated that in rMSCs, there were small numbers of re-proliferating cells appearing after a substantial senescent period. These “senescence-escaped”rMSCs were highly proliferative and did not show any sign of growth arrest during the following subcultures upto observed passage 32. Whereas after entering senescence, hMSCs no longer re-proliferated and finally died from apoptosis. Compared with rMSCs, the hMSCs possessed a much shorter telomere, and lacked both telomerase reverse transcriptase expression and telomerase activity. When proliferating from pre-senescent to senescent stages,the hMSCs had a greater loss of relative telomere length(51 % in hMSC vs. 15 % in rMSC), but both cells displayed a similar average telomere shortening per population doubling (0.50 ± 0.06 kb in rMSC vs. 0.49 ± 0.06 kbin hMSC; p > 0.05), indicating that the greater relative shortening of the hMSC telomeres was due to their original shorter length, rather than lack of telomere maintenance mechanisms. In conclusion, the hMSCs do not spontaneously initiate transformation, because they cannot escape senescence. This is particularly due to their much shorter telomere.

Association between previously identified loci affecting telomere length and coronary heart disease (CHD) in Han Chinese population

Purpose

To replicate previously confirmed telomere-length loci in a Chinese Han population with coronary heart disease (CHD), and investigate these loci and the possibility of and age at onset of CHD.

Patients and methods

1514 CHD patients and 2470 normal controls were recruited. Medical data including age, sex, body mass index, lipid profiles, history of hypertension, type 2 diabetes mellitus, and dyslipidemia were collected from all the participants. Seven previously identified single-nucleotide polymorphisms (SNPs) related to leucocyte telomere length were genotyped, including rs10936599 in TERC, rs2736100 in TERT, rs7675998 in NAF1, rs9420907 in OBFC1, rs8105767 in ZNF208, rs755017 in RTEL1, and rs11125529 in ACYP2.

Results

No significant difference in genotype frequencies from the Hardy–Weinberg equilibrium test was noted for all tested SNPs both in the CHD patients and the normal controls. No polymorphism was observed for rs9420907, and AA genotype was noted in both the CHD patients and the controls. Neither the genotype nor the allele frequencies of rs2736100, rs8105767, rs11125529, and rs2967374 were significantly different between the CHD patients and the normal controls. For rs10936599 and rs755017, statistical difference was found for the allele frequency but not genotype. Distributions of genotype and allele were significantly different between the two groups for rs7675998. The odds ratio for carriers of CHD was 2.127 (95% confidence interval: 1.909–2.370) for the A allele of rs7675998. By one-way analysis of variance test, rs7675998 was associated with the onset age of CHD. CHD patients with the AA genotype of rs7675998 had significantly lower onset age (P<0.05).

Conclusion

In a Chinese Han population, NAF1 gene encoding proteins with known function in telomere biology may influence both the possibility of and the age at onset of CHD, as previously reported in European studies.

Effects of the polymeric niche on neural stem cell characteristics during primary culturing

The polymeric niche encountered by cells during primary culturing can affect cell fate. However, most cell types are primarily propagated on polystyrene (PS). A cell type specific screening for optimal primary culture polymers particularly for regenerative approaches seems inevitable. The effect of physical and chemical properties of treated (corona, oxygen/nitrogen plasma) and untreated cyclic olefin polymer (COP), polymethymethacrylate (PMMA), PP, PLA, PS, PC on neuronal stem cell characteristics was analyzed. Our comprehensive approach revealed plasma treated COP and PMMA as optimal polymers for primary neuronal stem cell culturing and propagation. An increase in the number of NT2/D1 cells with pronounced adhesion, metabolic activities and augmented expression of neural precursor markers was associated to the plasma treatment of surfaces of COP and PMMA with nitrogen or oxygen, respectively. A shift towards large cell sizes at stable surface area/volume ratios that might promote the observed increase in metabolic activities and distinct modulations in F-actin arrangements seem to be primarily mediated by the plasma treatment of surfaces. These results indicate that the polymeric niche has a distinct impact on various cell characteristics. The selection of distinct polymers and the controlled design of an optimized polymer microenvironment might thereby be an effective tool to promote essential cell characteristics for subsequent approaches.

Hedgehog signaling regulates telomerase reverse transcriptase in human cancer cells

The Hedgehog (HH) signaling pathway is critical for normal embryonic development, tissue patterning and cell differentiation. Aberrant HH signaling is involved in multiple human cancers. HH signaling involves a multi-protein cascade activating the GLI proteins that transcriptionally regulate HH target genes. We have previously reported that HH signaling is essential for human colon cancer cell survival and inhibition of this signal induces DNA damage and extensive cell death. Here we report that the HH/GLI axis regulates human telomerase reverse transcriptase (hTERT), which determines the replication potential of cancer cells. Suppression of GLI1/GLI2 functions by a C-terminus truncated GLI3 repressor mutant (GLI3R), or by GANT61, a pharmacological inhibitor of GLI1/GLI2, reduced hTERT protein expression in human colon cancer, prostate cancer and Glioblastoma multiforme (GBM) cell lines. Expression of an N-terminus deleted constitutively active mutant of GLI2 (GLI2ΔN) increased hTERT mRNA and protein expression and hTERT promoter driven luciferase activity in human colon cancer cells while GANT61 inhibited hTERT mRNA expression and hTERT promoter driven luciferase activity. Chromatin immunoprecipitation with GLI1 or GLI2 antibodies precipitated fragments of the hTERT promoter in human colon cancer cells, which was reduced upon exposure to GANT61. In contrast, expression of GLI1 or GLI2ΔN in non-malignant 293T cells failed to alter the levels of hTERT mRNA and protein, or hTERT promoter driven luciferase activity. Further, expression of GLI2ΔN increased the telomerase enzyme activity, which was reduced by GANT61 administration in human colon cancer, prostate cancer, and GBM cells. These results identify hTERT as a direct target of the HH signaling pathway, and reveal a previously unknown role of the HH/GLI axis in regulating the replication potential of cancer cells. These findings are of significance in understanding the important regulatory mechanisms that determine the functions of HH/GLI signaling in cancer cells.

Life-long programming implications of exposure to tobacco smoking and nicotine before and soon after birth: evidence for altered lung development

Tobacco smoking during pregnancy remains common, especially in indigenous communities, and likely contributes to respiratory illness in exposed offspring. It is now well established that components of tobacco smoke, notably nicotine, can affect multiple organs in the fetus and newborn, potentially with life-long consequences. Recent studies have shown that nicotine can permanently affect the developing lung such that its final structure and function are adversely affected; these changes can increase the risk of respiratory illness and accelerate the decline in lung function with age. In this review we discuss the impact of maternal smoking on the lungs and consider the evidence that smoking can have life-long, programming consequences for exposed offspring. Exposure to maternal tobacco smoking and nicotine intake during pregnancy and lactation changes the genetic program that controls the development and aging of the lungs of the offspring. Changes in the conducting airways and alveoli reduce lung function in exposed offspring, rendering the lungs more susceptible to obstructive lung disease and accelerating lung aging. Although it is generally accepted that prevention of maternal smoking during pregnancy and lactation is essential, current knowledge of the effects of nicotine on lung development does not support the use of nicotine replacement therapy in this group.

Cancer models, genomic instability and somatic cellular Darwinian evolution

The biology of cancer is critically reviewed and evidence adduced that its development can be modelled as a somatic cellular Darwinian evolutionary process. The evidence for involvement of genomic instability (GI) is also reviewed. A variety of quasi-mechanistic models of carcinogenesis are reviewed, all based on this somatic Darwinian evolutionary hypothesis; in particular, the multi-stage model of Armitage and Doll (Br. J. Cancer 1954:8;1-12), the two-mutation model of Moolgavkar, Venzon, and Knudson (MVK) (Math. Biosci. 1979:47;55-77), the generalized MVK model of Little (Biometrics 1995:51;1278-1291) and various generalizations of these incorporating effects of GI (Little and Wright Math. Biosci. 2003:183;111-134; Little et al. J. Theoret. Biol. 2008:254;229-238).

Quantum dots thermal stability improves simultaneous phenotype-specific telomere length measurement by FISH-flow cytometry

Telomere length analysis has been greatly simplified by the quantitative flow cytometry technique FISH-flow. In this method, a fluorescein-labeled synthetic oligonucleotide complementary to the telomere terminal repeat sequence is hybridized to the telomere sequence and the resulting fluorescence measured by flow cytometry. This technique has supplanted the traditional laborious Southern blot telomere length measurement techniques in many laboratories, and allows single cell analysis of telomere length in high-throughput sample formats. Nevertheless, the harsh conditions required for telomere probe annealing (82 degrees C) has made it difficult to successfully combine this technique with simultaneous immunolabeling. Most traditional organic fluorescent probes (i.e. fluorescein, phycoerythrin, etc.) have limited thermal stability and do not survive the high temperature annealing process, despite efforts to covalently crosslink the antigen-antibody-fluorophore complex. This loss of probe fluorescence has made it difficult to measure FISH-flow in complex lymphocyte populations, and has generally forced investigators to use fluorescent-activated cell sorting to pre-separate their populations, a laborious technique that requires prohibitively large numbers of cells. In this study, we have substituted quantum dots (nanoparticles) for traditional fluorophores in FISH-flow. Quantum dots were demonstrated to possess much greater thermal stability than traditional low molecular weight and phycobiliprotein fluorophores. Quantum dot antibody conjugates directed against monocyte and T cell antigens were found to retain most of their fluorescence following the high temperature annealing step, allowing simultaneous fluorescent immunophenotyping and telomere length measurement. Since quantum dots have very narrow emission bandwidths, we were able to analyze multiple quantum dot antibody conjugates (Qdot 605, 655 and 705) simultaneously with FISH-flow measurement to assess the age-associated decline in telomere length in both human monocytes and T cell subsets. With quantum dot immunolabeling, the mean decrease rate in telomere length for CD4+ cells was calculated at 41.8 bp/year, very close to previously reported values using traditional flow-FISH and Southern blotting. This modification to the traditional flow-FISH technique should therefore allow simultaneous fluorescent immunophenotyping and telomere length measurement, permitting complex cell subset-specific analysis in small numbers of cells without the requirement for prior cell sorting.

Leukocyte telomere dynamics and human hematopoietic stem cell kinetics during somatic growth

OBJECTIVE

A central question in stem cell research is knowing the frequency of human hematopoietic stem cells (HSC) replication in vivo.

MATERIALS AND METHODS

We have constructed a model that characterizes HSC kinetics and the relative sizes of the hematopoietic progenitor cell (HPC) and HSC pools from birth onward. The model capitalizes on leukocyte telomere length (LTL) data and body weight-gain charts from birth to the age of 20 years. The core premise of the model is that during human growth, LTL dynamics (birth LTL and age-dependent LTL shortening afterward) chronicle the expansions of the HSC and HPC pools.

RESULTS

The model estimates that by the end of the first year of life, HSC have replicated approximately 17 times and they replicate approximately 2.5 times/year between the ages of 3 and 13 years. Subsequently, HSC replication slows considerably. In adults HSC replicate at a rate of approximately 0.6 times/year. In addition, the model predicts that newborns with small birth weight would have shorter LTL as adults and that women would have longer LTL than men.

CONCLUSION

Our findings will be useful in bone marrow transplantations and might explain a body of clinical observations related to LTL distribution in the general population.

Exercise training improves the antioxidant enzyme activity with no changes of telomere length

The purpose of this study was to determine the changes of both oxidant and antioxidant levels with exercise training in obese middle-aged women. The association between telomere length and oxidative stress with exercise was also examined. Sixteen obese middle-aged women participated in this study. The subjects were randomly divided into exercise group (EX) and control group (CON). EX performed aerobic exercise training for 6 months. DNA was extracted from leukocytes in peripheral blood and their telomere lengths were measured by real time PCR analysis. Long-term exercise training decreased body weight and BMI, and increased VO2 max. Resting levels of erythrocyte glutathione peroxidase activity were higher in EX compared to CON. Superoxide dismutase (SOD) activities were higher after the acute exercise test at mid-intensity in post-exercise training than in the pre-exercise training conditions. The telomere length did not change significantly after the acute exercise test in the pre-exercise training condition in spite of the increased level of malondialdehyde (MDA) as a marker of oxidative stress. In conclusion, antioxidant enzyme activities were increased following long-term exercise training; however, the lengths of telomere in leukocytes were not influenced by both mid-intensity and high intensity of exercise stress.

Premature telomere shortening in polymorphonuclear neutrophils from patients with systemic lupus erythematosus is related to the lupus disease activity

We investigated whether premature telomeric loss occurred in peripheral polymorphonuclear neutrophils (PMN) as well as mononuclear cells (MNC) from patients with systemic lupus erythematosus (SLE). We measured the telomere length of MNC and PMN in 60 SLE patients and 26 sex-, race- and age-matched healthy volunteers by Southern blotting with chemiluminescence method. The possible predisposing factors associated with telomere change were also analysed. We found the telomere length of MNC and PMN shortened with age in different degrees in both SLE and control groups. Compared to the control group, the telomere length was shortened in both SLE-MNC (6.08 kb in SLE versus 6.71 kb in control, P = 0.0008) and PMN (6.24 kb in SLE versus 6.75 kb in control, P = 0.0025). The average reduction in telomere length in SLE patients was equivalent to a premature senescence of 16.5 years in MNC and 13.4 years in PMN. In addition, the accelerated telomere shortening was more prominent in SLE patients younger than 45 years old. SLE disease activity (SLEDAI) contributed remarkably to the accelerated telomere erosion, at least in PMN. Moreover, the telomere length of MNC was significantly shorter than PMN in the same SLE patients with leukopenia and lymphopenia. These data suggested that MNC and PMN from patients with SLE displayed premature and accelerated telomere shortening that SLE is an independent factor for it.

Clinical and laboratory parameters that define clinically relevant B-CLL subgroups

B cell-type chronic lymphocytic leukemia (B-CLL) is a heterogeneous disease. This is reflected by the very wide-ranging clinical courses that B-CLL patients experience and by the marked variation in laboratory findings between patients. In this chapter, we will review the various clinical and laboratory parameters that divide B-CLL patients into "subgroups," and correlate the parameters that define them. When feasible, we will also link clinical features to the cellular and genetic characteristics recently defined for these leukemic cells. The discussion is limited to parameters that define phenotypes or subgroups that may relate to disease activity and clinical outcome.

Telomere dysfunction: a new player in radiation sensitivity

Human individuals often exhibit important differences in their sensitivity to ionising radiation. Extensive literature links radiation sensitivity with impaired DNA repair which is due to a lack of correct functioning in many proteins involved in DNA-repair pathways and/or in DNA-damage checkpoint responses. Given that ionising radiation is an important and widespread diagnostic and therapeutic tool, it is important to investigate further those factors and mechanisms that underlie individual radiosensitivity. Recently, evidence is accumulating that telomere function may well be involved in cellular and organism responses to ionising radiation, broadening still further the currently complex and challenging scenario.

Expansion of mesenchymal stem cells isolated from pediatric and adult donor bone marrow

The enormous plasticity of mesenchymal stem cells (MSCs) suggests an improvement of a standard protocol of isolation and ex vivo expansion for experimental and clinical use. We isolated and expanded MSCs from bone marrow (BM) of pediatric and young adult donors, to analyze the growth kinetic, immunophenotype, telomere length, karyotype during ex vivo expansion. Seventeen BM samples were collected from young adult donors and 8 from pediatric donors. MSCs isolated from two groups showed no morphological differences while their cell growth was strictly related to the donor's age. The MSCs isolated from pediatric donors reached a cumulative PD almost twice as high as MSCs isolated from young adult donors after 112 days (10.2 +/- 1.9 versus 5.5 +/- 3.7). Furthermore, we analyzed the modulation of antigen expression in the MSCs isolated from two groups until 10th passage (77 days) and there was no significant difference between the modulation of antigen expression. In particular, at the first passage, MSCs showed a low contamination of hemopoietic cells which became insignificant in the following passages. There was a high expression of CD90, CD29, CD44 and CD105 and variable and moderate expression of CD166 and CD106 at the start of MSC culture and at each passage during expansion. No chromosomal alteration or evidence of cellular senescence were observed in all analyzed samples. All these data suggest that MSCs can be isolated and expanded from most healthy donors, providing for an autologous source of stem cells.

Over-expression of hTERT in CHO K1 results in decreased apoptosis and reduced serum dependency

The enzyme telomerase plays a crucial role in cellular proliferation. By adding hexameric repeats to the chromosome ends, it prevents telomeric loss and, thus entry into senescence of limited life span cells. It is unclear, however, what would be the effect of over-expressing telomerase in an immortalised cell line, characterised by unlimited life span and high levels of apoptosis under sub-optimal growth conditions. In order to address this question, we have transfected the immortal cell line CHO K1 with the human telomerase reverse transcriptase (hTERT) catalytic subunit. Differences in the growth profile and apoptosis levels between the cells over-expressing hTERT (Telo) and the cells containing mock vector were found under standard growth conditions. Similarly, the Telo cells showed lower levels of apoptosis, greater attachment tendency and higher viable cell density under serum-deprived conditions compared to the control cell line, suggesting a major role for hTERT over-expression in stressed cultures. Using a mouse cDNA microarray, the collagen type III and V genes were shown to have at least a 10-fold higher expression in the Telo cells than the control cells, suggesting a role of hTERT in the cell attachment pathways.

T cell aging: naive but not young

The immune system exhibits profound age-related changes, collectively termed immunosenescence. The most visible of these is the decline in protective immunity, which results from a complex interaction of primary immune defects and compensatory homeostatic mechanisms. The sum of these changes is a dysregulation of many processes that normally ensure optimal immune function. Recent advances suggest that old mice can produce fully functional new T cells, opening both intriguing inquiry avenues and raising critical questions to be pursued.

Cancer and aging: the importance of telomeres in genome maintenance

Telomeres are the specialized DNA-protein structures that cap the ends of linear chromosomes, thereby protecting them from degradation and fusion by cellular DNA repair processes. In vertebrate cells, telomeres consist of several kilobase pairs of DNA having the sequence TTAGGG, a few hundred base pairs of single-stranded DNA at the 3' end of the telomeric DNA tract, and a host of proteins that organize the telomeric double and single-stranded DNA into a protective structure. Functional telomeres are essential for maintaining the integrity and stability of genomes. When combined with loss of cell cycle checkpoint controls, telomere dysfunction can lead to genomic instability, a common cause and hallmark of cancer. Consequently, normal mammalian cells respond to dysfunctional telomeres by undergoing apoptosis (programmed cell death) or cellular senescence (permanent cell cycle arrest), two cellular tumor suppressor mechanisms. These tumor suppressor mechanisms are potent suppressors of cancer, but recent evidence suggests that they can antagonistically also contribute to aging phenotypes. Here, we review what is known about the structure and function of telomeres in mammalian cells, particularly human cells, and how telomere dysfunction may arise and contribute to cancer and aging phenotypes.

Divergent cell cycle kinetics underlie the distinct functional capacity of mucosal T cells in Crohn's disease and ulcerative colitis

BACKGROUND

Different abnormalities of T cell effector function distinguish Crohn's disease (CD) from ulcerative colitis (UC). Because cell cycling determines effector function, pathogenic events in CD and UC may depend on cell cycle changes unique to each condition.

METHODS

Cell cycle kinetics, cycle regulatory molecule expression, apoptosis, caspase and telomerase activity, and cellular expansion were evaluated in CD2 and CD3 activated control, CD, and UC lamina propria T cells.

RESULTS

Compared with normal cells, CD T cells cycle faster, express increased phosphorylated Rb and decreased phosphorylated p53 levels, display less caspase activity but more telomerase activity, die less, and undergo vigorous cellular expansion. In contrast, UC T cells cycle slower, express normal levels of phosphorylated Rb and p53, display more caspase activity but have no telomerase activity, die more, and have a limited capacity to expand.

CONCLUSIONS

T cell cycle abnormalities in CD indicate a state of hyperreactivity compatible with loss of tolerance, but a hyporeactive state compatible with anergy in UC. Thus distinct and divergent T cell cycle characteristics underlie the pathogenesis of the two main forms of inflammatory bowel disease.

Telomere length and telomerase activity delineate distinctive replicative features of the B-CLL subgroups defined by immunoglobulin V gene mutations

Patients with B-cell chronic lymphocytic leukemia (B-CLL) segregate into subgroups with very different survival times. Because clinical observations suggest that leukemic cells accumulate at different rates, we measured telomere length and telomerase activity in B-CLL cells to distinguish differences in cellular replication. Our data indicate that the telomeres of B-CLL cells are shorter than telomeres of B cells from healthy subjects, indicating that the leukemic cells have a prolonged proliferative history. Leukemic cells of the immunoglobulin V gene mutation subgroups differ in telomere length and telomerase activity. B lymphocytes from the subgroup with poor outcome and with limited IgV gene mutations have uniformly shorter telomeres and more telomerase activity than those from the subgroup with better outcome and with considerable mutations. Differences in telomere length appear to largely reflect the proliferative histories of precursors of the leukemic cells, although differences in cell division, masked by the action of telomerase, cannot be excluded. These results may provide insight into the stages of maturation and the activation pathways of the cells that give rise to B-CLL. In addition, they reinforce the concept that B-CLL is not simply an accumulative disease of slowly dividing B lymphocytes but possibly one of B cells with extensive proliferative histories.

Immunotherapy and prostate cancer

Prostate cancer is the second leading cause of cancer death in the US, largely because of the limitations of our current therapeutic options, especially once the cancer has metastasized. Investigators have long sought new therapeutic modalities such as angiogenesis inhibitors, vaccines, and gene therapy, among others. It appears that a combination approach will be required to cure the majority of malignancies. Immunotherapy for prostate cancer appears feasible and a likely therapeutic modality in the armamentarium. Unfortunately, further research in basic immunology and the interaction of the immune system with other forms of therapy is needed. Many obstacles exist in immunotherapy, including vector design, tumouricidal specificity, and tumor evasion, which will have to be overcome in order to realize the maximum therapeutic benefit from this treatment modality.

Telomere length and telomerase activity: effect of ageing on human NK cells

Telomeres are repeats of TTAGGG sequences located at the end of eukaryotic chromosomes. They are essential for stabilisation and protection of chromosomal ends and for the regulation of cell replicative capacity. Due to the end-replication defect of DNA polymerase, telomeres shorten progressively with each cell division and telomere length may be an indicator of the replicative history of a cell. Compensatory mechanisms for the telomere loss have been identified. The most widely studied one is mediated by telomerase a ribonuclear protein-enzyme complex that synthesise telomeric repeats. In this study we have investigated whether NK cells, derived from a group of old healthy subjects, underwent the modifications of telomere length and telomerase activity observed in other sub-populations of lymphocytes with advancing age. We demonstrated that: (a) telomere shortening occurred and telomerase activity decreased in human NK cells with ageing; (b) the rate of telomere loss was different under and over 80 years of age; (c) similarly to telomere shortening, the modification of telomerase activity was particularly evident in octogenarians; (d) subjects with the most evident modifications of telomeres and telomerase were the oldest and those with increased NK cell numbers.

Stable telomere length and telomerase expression from naïve to memory B-lymphocyte differentiation

Telomere length and telomerase activity play important roles in regulating replicative lifespan of cells. The length of telomeres also serves as a marker for the replicative history and for the remaining replicative potential of cells. Differential telomere length has been reported in human naïve and memory T cells but not in naïve versus memory B-lymphocytes. We report here an analysis of telomere length and induced telomerase expression in naïve (CD27(-)) and memory (CD27(+)) B cells from normal adults. Although both naïve and memory B cells lose telomere repeats with age, there is no consistent difference in telomere length between these two B cell subsets. Furthermore, both naïve and memory B cells are capable of inducing telomerase activity at similar levels after in vitro stimulation independent of donor's age. Finally, there is a slow increase of memory B cells in peripheral blood with age. Together, these findings suggest that B cells are capable of maintaining telomere length during differentiation from naïve to memory B cells and this ability is maintained through age.

Mus musculus and Mus spretus homologues of the human telomere-associated protein TIN2

Telomere length is regulated by TRF1, which binds telomeric DNA, and TIN2, which binds TRF1. Laboratory mice (Mus musculus) have long telomeres, although a related mouse species, Mus spretus, has human-sized telomeres. Because differences in TIN2 might explain these differences in telomere length, we cloned cDNAs encoding murine TIN2s and compared their sequence to that of human TIN2. M. musculus (Mm) and M. spretus TIN2s were >95% identical, but shared only 67% identity with human TIN2. An N-terminal truncation, or N-terminal fragment, of MmTIN2 elongated M. spretus telomeres. These findings suggest that mouse TIN2, like human TIN2, negatively regulates telomere length, and that N-terminal perturbations have dominant-negative effects. Our findings suggest that differences in TIN2 cannot explain the telomere length differences among Homo sapiens, M. musculus, and M. spretus. Nonetheless, M. spretus cells appear be a good system for studying the function of mouse telomere-associated proteins.

Dendritic cells reconstituted with human telomerase gene induce potent cytotoxic T-cell response against different types of tumors

Human telomerase reverse transcriptase (hTERT) is the catalytic component of a functional telomerase complex, which is important in maintaining cell immortality. In most normal human adult cells, the expression of telomerase is very low and/or transient. In contrast, almost 90% of human tumors express a relatively high level of telomerase implying the possibility of using hTERT as a universal candidate tumor antigen. In this study, we show that human monocyte-derived dendritic cells (DCs) lack telomerase activity. Similar to other normal somatic cells, DCs express the RNA (hTR) component but not the catalytic component, hTERT. We also show that telomerase activity could be reconstituted using either lipid-mediated transfection of the hTERT plasmid DNA or transduction with an E1-, E3-deleted adenoviral vector containing the hTERT gene. However, relative to plasmid transfection, adenoviral gene transfer produced higher levels of hTERT expression. Nine of 10 AdhTERT-transduced DCs were able to generate CTL responses, while only three of nine plasmid-transfected DCs did. CTLs primed against hTERT exhibited killing of telomerase positive but not telomerase negative tumor lines of diverse tissue origins. Antigenic specificity of these T cells to telomerase was further determined by introducing hTERT gene into a telomerase negative cell line, U2OS, by adenoviral transduction. Although some antigenic specificity was directed against adenoviral epitopes, the majority of CTLs were targeted against telomerase-derived antigen(s). Thus, the hTERT gene, particularly as delivered via the recombinant adenovirus, may be useful as vaccine to induce specific T-cell-mediated tumor immunity in cancer patients. In addition, our results suggest that telomerase activity and/or telomerase expression after hTERT gene transfer have a predictive value in the success of hTERT/DC-based cancer vaccination.

Telomere maintenance in human B lymphocytes

Telomere shortening has been causally linked to replicative senescence in human cells. To characterize telomere-length heterogeneity in peripheral blood cells of normal individuals, we analysed the mean length of telomeric repeat sequences in subpopulations of peripheral blood leucocytes, using fluorescence in situ hybridization and flow cytometry (flow-FISH). Although the telomere length of most haematopoietic subsets was within the same range, the mean telomere length was found to be 15% higher in B compared with T lymphocytes in adult peripheral blood. Whereas telomere loss with ageing corresponded to 33 base pairs (bp) per year in T cells, telomere shortening was slower in B cells, corresponding to 15 bp per year. Separation of adult B-lymphocyte subpopulations based on CD27 expression revealed that telomere length was almost 2 kb longer in CD19+CD27+ (memory) compared with CD19+CD27- (naive) cells. Furthermore, peripheral blood B cells were activated in vitro. Whereas B-cell activation with Staphylococcus aureus Cowan strain (SAC) did not increase telomere length, a striking telomere elongation was observed when cells were stimulated with SAC and interleukin 2 to induce plasma cell differentiation. Our observations support the concept that telomere dynamics in B cells are distinct from other haematopoietic cell lineages and that telomere elongation may play an essential role in the generation of long-term B memory cells.

Adult stem cells: assessing the case for pluripotency

It has been known for decades that stem cells with limited differentiation potential are present in post-natal tissues of mammals, and adult stem cells are already used clinically. For instance, hematopoietic stem cells can reestablish the hematopoietic system following myeloablation, and stem cells are being used to regenerate corneal and skin tissue. But recent studies report that adult tissues might contain cells with pluripotent characteristics. These have evoked significant excitement, given the medical implications, but have also met with much skepticism. Indeed, most studies still await independent confirmation, there is a low frequency with which the apparent lineage switching occurs, and importantly such lineage switching defies established developmental biology and stem cell principles. Here, I critically review the published data indicating that postnatal stem cells persist that have greater differentiation potential than previously thought.

Cancer and aging: a model for the cancer promoting effects of the aging stroma

The incidence of cancer rises exponentially with age in humans and many other mammalian species. Malignant tumors are caused by an accumulation of oncogenic mutations. In addition, malignant tumorigenesis requires a permissive tissue environment in which mutant cells can survive, proliferate, and express their neoplastic phenotype. We propose that the age-related increase in cancer results from a synergy between the accumulation of mutations and age-related, pro-oncogenic changes in the tissue milieu. Most age-related cancers derive from the epithelial cells of renewable tissues. An important element of epithelial tissues is the stroma, the sub-epithelial layer composed of extracellular matrix and several cell types. The stroma is maintained, remodeled and repaired by resident fibroblasts, supports and instructs the epithelium, and is essential for epithelial function. One change that occurs in tissues during aging is the accumulation of epithelial cells and fibroblasts that have undergone cellular senescence. Cellular senescence irreversibly arrests proliferation in response to damage or stimuli that put cells at risk for neoplastic transformation. Senescent cells secrete factors that can disrupt tissue architecture and/or stimulate nearby cells to proliferate. We therefore speculate that their presence may create a pro-oncogenic tissue environment that synergizes with oncogenic mutations to drive the rise in cancer incidence with age. Recent evidence lends support to this idea, and suggests that senescent stromal fibroblasts may be particularly adept at creating a tissue environment that can promote the development of age-related epithelial cancers.

Functional characterization of the poly(ADP-ribose) polymerase activity of tankyrase 1, a potential regulator of telomere length

Poly(ADP-ribose) polymerases (PARPs) comprise a growing family of enzymes known to be involved in genotoxic signaling and metabolic regulation. One of the latest family members, tankyrase 1, was shown to be involved in maintenance of telomere integrity. Here we expressed full-length tankyrase 1 and a fragment, termed T-PARP, spanning the poly(ADP-ribose) polymerase domain and characterized the enzymatic properties of the two proteins. Both, tankyrase 1 and T-PARP catalyze an auto poly(ADP-ribosyl)ation reaction with comparable catalytic activity. In contrast, (ADP-ribosyl)ation of TRF1, a previously described substrate, is strongly performed only by the full-length enzyme but not by T-PARP. Characterization of the poly(ADP-ribose) products reveals that tankyrase 1 synthesizes polymers with an average chain length of 20 units and no detectable branching of the polymers. Finally, we show that the catalytic efficiency of tankyrase 1, as expressed by the k(cat)/K(m) value, is approximately 150-fold lower compared to the basal activity of the poly(ADP-ribose) polymerase, PARP 1.

Stability and plasticity of wild-type and Pax5-deficient precursor B cells

In Pax5-deficient mice, B cell development is blocked at the pre-BI cell stage. Like wild-type, Pax5-/- pre-BI cells can be grown long-term in vitro in the presence of stromal cells and IL-7. However, unlike their wild-type in vitro-grown counterparts, Pax5-/- pre-BI cells possess an extraordinary developmental plasticity showing hematopoietic stem cell features such as multipotency and self renewing capacity. Here we review and discuss this in vitro and in vivo plasticity of Pax5-/- pre-BI cells.

The genetics of aging-- implications for pharmacogenomics

Lifespan experiments of lower organisms and mammals along with recent studies of centenarians are making inroads into delineating genetic factors that determine the ability to achieve exceptional longevity. These models may be helpful for the discovery of both longevity-enabling genes as well as genes associated with increased propensity to develop specific diseases. Both academic and commercial laboratories are putting substantial resources into discovering such genes in order to better understand the genetic and environmental underpinnings of how some people age more slowly than others and markedly delay or even escape age-associated diseases.

p53 negatively regulates intestinal immunity by delaying mucosal T cell cycling

To mount an effective immune response, T cells must divide in response to antigen contact. To maintain tolerance, mucosal lamina propria T cells (LPTs) may adapt their cycling to an antigen-rich gut stimulatory environment. Here, we compared the cell cycle kinetics of LPTs and peripheral blood T cells (PBTs) before and after CD3- and CD2-mediated activation. While CD3-activated naive (CD45RA(+)) and memory (CD45RO(+)) PBTs peaked in the S and G2/M phase at 2-3 days, CD3-activated LPTs peaked at 4-6 days. In contrast, CD2 activation induced modest PBT but vigorous LPT cycling. The doubling time of CD3-activated PBTs was 1 day, while that of CD3- or CD2-activated LPTs was 2 days. LPTs failed to upregulate cyclin-dependent kinase 4 and cyclin D3, but Rb phosphorylation and cyclin A and B1 upregulation were induced by CD2 engagement. The extents of clonal expansion in LPT and PBT were comparable, indicating that LPTs' slow replication delays but does not hinder cell division. CD2-activated LPTs displayed a striking upregulation of p53, whose blockade by antisense oligonucleotides accelerated their S phase transit time to that of CD3-activated PBTs. By slowing LPT cycling, p53 may act as a negative regulator of mucosal immunity, promoting immunological tolerance by preventing excessive T cell replication.

Clinical significance of telomerase activity in multiple myeloma

BACKGROUND

The clinical course of patients with multiple myeloma varies, and therefore it is important to evaluate the disease state. We studied the telomerase activity of myeloma cells as a possible prognostic factor in such patients.

METHODS

Twenty five samples from patients with multiple myeloma were studied. We purified myeloma cells in bone marrow samples according to the expression of surface antigens, CD38 and CD45. CD38+/CD45- or dim cells had morphologic characteristics of myeloma cells, with a purity exceeding 95%. The telomerase activity of myeloma cells was determined by a polymerase chain reaction-based telomeric repeat amplification protocol assay. Ki-67 positivity of the purified cells was determined by flow cytometry using anti-Ki-67 antibody. The relationship between telomerase activity and prognostic factors was also examined.

RESULTS

A significantly high degree of telomerase activity was detected in subjects with a serum beta2-microglobulin level > or = 6 mg/dL or at Stage III (P = 0.002). The serum C-reactive protein, lactate dehydrogenase, and creatinine levels did not correlate with the telomerase activity, but this activity did significantly correlate with Ki-67 positivity and the percentage of plasma cells in the bone marrow (r = 0.561, P = 0.004, and r = 0.397, P = 0.049, respectively). The patients with high levels of telomerase activity were thus found to have a significantly short survival time after sampling (P = 0.035).

CONCLUSIONS

The measurement of the telomerase activity in myeloma cells was found to be a reliable marker for the proliferating capacity and tumor mass in myeloma patients. The telomerase activity of myeloma cells may therefore be useful as a prognostic factor.

Extensive in vivo self-renewal, long-term reconstitution capacity, and hematopoietic multipotency of Pax5-deficient precursor B-cell clones

Self-renewal, pluripotency, and long-term reconstitution are defining characteristics of single hematopoietic stem cells. Pax5(-/-) precursor B cells apparently possess similar characteristics. Here, using serial transplantations, with in vitro recloning and growth of the bone marrow-homed donor cells occurring after all transplantations, we analyzed the extent of self-renewal and hematopoietic multipotency of Pax5(-/-) precursor B-cell clones. Moreover, telomere length and telomerase activity in these clones was analyzed at various time points. Thus far, 5 successive transplantations have been performed. Clones transplanted for the fifth time, which have proliferated for more than 150 cell divisions in vitro, still repopulate the bone marrow with precursor B cells and reconstitute these recipients with lymphoid and myeloid cells. During this extensive proliferation, Pax5(-/-) precursor B cells shorten their telomeres at 70 to 90 base pairs per division. Their telomerase activity remains at 3% of that of HEK293 cancer cells during all serial in vivo transplantations/in vitro expansions. Together, these data show that Pax5(-/-) precursor B-cell clones possess extensive in vivo self-renewal capacity, long-term reconstitution capacity, and hematopoietic multipotency, with their telomeres shortening at the normal rate.

Age-related telomere length dynamics in peripheral blood mononuclear cells of healthy cynomolgus monkeys measured by Flow FISH

Telomere length is a good biomarker to study the cellular senescence as well as aging of an organism, because it regulates the replicative capacity of vertebrate somatic cells. To demonstrate age-related telomere length dynamics in the peripheral blood mononuclear cells (PBMC) of the cynomolgus monkey, we introduced a novel method of measuring telomere length by fluorescence in situ hybridization with a Peptide Nucleic Acid (PNA) labelled probe and flow cytometry (Flow FISH). A highly significant correlation was observed between the intensity of telomere-specific fluorescence by Flow FISH and telomere length by Southern blot analysis (R = 0.923, n = 22). The intensity of telomere fluorescence in PBMC significantly decreased with age in 55 monkeys aged from 0 to 34 years and this decrease corresponded to the loss of 62.7 base pairs per year (R = - 0.52, P < 0.00004). We also analysed the expression of naive cell-associated markers, CD28, CD62L and CD45RA/CD62L in T lymphocytes of 47 cynomolgus monkeys. An age-related increase in the CD28- subset was observed in CD8+ T lymphocytes in monkeys less than 11 years old and in CD4+ T lymphocytes in monkeys over 23 years old, respectively. The percentage of CD62L+ subsets was significantly decreased with age in both CD4+ (R = - 0.55) and CD8+ T lymphocytes (R = - 0.73). From the comparison of telomere length among PBMC, CD62L+ and CD62L- T lymphocytes, it was clearly evident that loss of naive subsets results in the shortening of telomere length in vivo. These results show that this method can be applicable to studying the turnover and precursor-progeny of PBMC in cynomolgus monkeys as an animal model of aging.