Direct Correlation among Telomere Length, Cellular Aging, and Rejuvenation Effects of Honey Child Powder

Purpose: Telomere length (TL) is an indicator of age;however, hormonal influences complicate individual aging. It remains unclear whether TL shortening is a direct factor in both individual and cellular aging. Therefore, we examined the direct relationship between TL and cellular senescence at the cellular level. Methods: Telomerase activity, TL, and gene expression were measured in cultured human lung-, fetal-, and skin-derived fibroblasts, human skin keratinocytes, and telomerase reverse transcriptase (TERT) gene-immortalized cells using detection kits, Cawthon’s method, and reverse transcription-quantitative polymerase chain reaction, respectively. Novel substances that elongate telomeres were screened to confirm cell rejuvenation effects. Results: Long-term cell culture of TIG-1-20 normal human fibroblasts resulted in TL shortening, decreased division rate, and senescence progression, whereas in OUMS-36T-2 cells, TL elongation via TERT gene transfer increased the division rate, reduced endoplasmic reticulum stress, and upregulated genes associated with young individuals, indicating that cellular rejuvenation occurs via TL elongation. In addition, a honey child powder (HCP) extract was found through screening, and the HCP extract strongly suppressed the menin gene, resulting in increased telomerase activity and extended cell lifespan. Upon addition of the HCP extract to skin fibroblasts, gene expression of moisturizing components, including collagen, hyaluronic acid, and elastin, increased, and exhibited a rejuvenating effect with an increase in elastin amount. Conclusions: TL elongation or shortening is involved in cell proliferation rate and cellular aging, and TL elongation rejuvenates cells. In addition, HCP extract has a rejuvenating effect on cells and is expected to be a rejuvenating compound.

A Study of Radiation-Induced Telomere Instability Using Multiplex Ligation-Dependent Probe Amplification (MLPA)

The integrity of the chromosomes for two WIL2-derived lymphoblastoid cell lines (TK6 and WTK1) in the presence and absence of ionizing radiation was analyzed by Multiplex Ligation-Dependent Probe Amplification (MLPA). The TK6 cell line has the native p53 tumor-suppressor gene, whereas WTK1 cells contain a p53 mutation. Each cell line was isolated pre- and post-irradiation (2 and 3 Gy) and analyzed by MLPA. The impact of irradiation on these two cell lines was investigated using probes that target specific regions on chromosomes associated with subtelomeric regions. Results indicate that WTK1 and TK6 are impacted differently after irradiation, and that each cell line presents its own unique MLPA profile. The most notable differences are the appearance of a number of probes in the post-irradiated MLPA profile that are not present in the controls, and two unique probe signals only seen in WTK1 cells. These results build on our previous studies that indicate how different human cell lines can be affected by radiation in significantly different ways depending on the presence or absence of wild type p53.

EPAS1 prevents telomeric damage-induced senescence by enhancing transcription of TRF1,TRF2,and RAD50

Telomeres are nucleoprotein structures located at the end of each chromosome,which function in terminal protection and genomic stability.Telomeric damage is closely related to replicative senescence in vitro and physical aging in vivo.As relatively long-lived mammals based on body size,bats display unique telomeric patterns,including the upregulation of genes involved in alternative lengthening of telomeres(ALT),DNA repair,and DNA replication.At present,however,the relevant molecular mechanisms remain unclear.In this study,we performed cross-species comparison and identified EPAS1,a well-defined oxygen response gene,as a key telomeric protector in bat fibroblasts.Bat fibroblasts showed high expression of EPAS1,which enhanced the transcription of shelterin components TRF1 and TRF2,as well as DNA repair factor RAD50,conferring bat fibroblasts with resistance to senescence during long-term consecutive expansion.Based on a human single-cell transcriptome atlas,we found that EPAS1 was predominantly expressed in the human pulmonary endothelial cell subpopulation.Using in vitro-cultured human pulmonary endothelial cells,we confirmed the functional and mechanistic conservation of EPAS1 in telomeric protection between bats and humans.In addition,the EPAS1 agonist M1001 was shown to be a protective compound against bleomycin-induced pulmonary telomeric damage and senescence.In conclusion,we identified a potential mechanism for regulating telomere stability in human pulmonary diseases associated with aging,drawing insights from the longevity of bats.

Association between Dietary Collagen Consumption and Telomere Length: National Health and Nutrition Examination Survey

Background: Bioactive peptides derived from hydrolyzed collagen have broad physiological functions and beneficial effects on human health, ranging from reducing skin aging to modifying lipid metabolism. Telomere length shortening is an established biomarker of cellular aging. It is not known if collagen consumption is associated with telomere length protection. Our purpose was to investigate the relationship between dietary collagen consumption and telomere length in a nationally representative US adult population. Methods: We analyzed the data of 6173 adults aged 20 - 84 from the National Health and Nutrition Examination Survey (NHANES) 1999-2002. Multivariable linear regression and a generalized additive model with smoothing plot were used to assess the association between the total collagen consumption and log-transformed leukocyte telomere length (LTL). Results: Compared with the lowest quartile of total collagen (Q1), we found that the second quartile of collagen (Q2) consumption (1.36 - 3.40 g/1000kcal) was positively associated with telomere length (β: 0.017;95% CI: 0.006, 0.028;P = 0.022) in the females while no association in the males (β: −0.003;95% CI: −0.019, 0.012;P = 0.678) and overall population (β: 0.008;95% CI: −0.002, 0.018;P = 0.141). The association in the females is nonlinear with an inflection point of 2.5 g/1000kcal (P for non-linearity: Conclusion: In conclusion, moderate dietary collagen has a positive and nonlinear association with telomere length in US females, while no significant associations were found in the males and the overall population.

Hematopoietic stem cell transplantation of aplastic anemia by relative with mutations and normal telomere length: A case report

BACKGROUND Immunosuppressive therapy and matched sibling donor hematopoietic stem cell transplantation(MSD-HSCT)are the preferred treatments for aplastic anemia(AA).CASE SUMMARY In this report,we describe a 43-year-old male patient with severe AA who carried BRIP1(also known as FANCJ),TINF2,and TCIRG1 mutations.Screening of the family pedigree revealed the same TINF2 mutation in his mother and older brother,with his older brother also carrying the BRIP1 variant and demonstrating normal telomere length and hematopoietic function.The patient was successfully treated with oral cyclosporine A,eltrombopag,and acetylcysteine,achieving remission 4 years after receiving MSD-HSCT from his older brother.CONCLUSION This case provides a valuable clinical reference for individuals with suspected pathogenic gene mutations,normal telomere length,and hematopoietic function,highlighting them as potential donors for patients with AA.

Telomere,telomerase and digestive cancer

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Telomeres,telomerase and colorectal cancer

Colorectal cancer(CRC)is the third most common cancer worldwide and,despite improved treatments,is still an important cause of cancer-related deaths.CRC encompasses a complex of diseases arising from a multistep process of genetic and epigenetic events.Besides heterogeneity in the molecular and biological features of CRC,chromosomal instability is a hallmark of cancer and cancer cells may also circumvent replicative senescence and acquire the ability to sustain unlimited proliferation.Telomere/telomerase interplay is an important mechanism involved in both genomic stability and cellular replicative potential,and its dysfunction plays a key role in the oncogenetic process.The erosion of telomeres,mainly because of cell proliferation,may be accelerated by specific alterations in the genes involved in CRC,such as APC and MSH2.Although there is general agreement that the shortening of telomeres plays a role in the early steps of CRC carcinogenesis by promoting chromosomal instability,the prognostic role of telomere length in CRC is still under debate.The activation of telomerase reverse transcriptase(TERT),the catalytic component of the telomerase complex,allows cancer cells to grow indefinitely by maintaining the length of the telomeres,thus favouring tumour formation/progression.Several studies indicate that TERT increases with disease progression,and most studies suggest that telomerase is a useful prognostic factor.Plasma TERT mRNA may also be a promising marker for the minimally invasive monitoring of disease progression and response to therapy.

Telomerase Activity in Human Renal Cell Carcinoma with Reference to Clinicopathologic Features

Objective: To study the telomerase activity in human renal cell carcinoma and to evaluate the correlation with the clinicobiologic features of the neogrowth.Methods: The telomerase activity was studied by means of a modified telomeric repeat amplification protocol (TRAP) in 32 renal cell carcinoma tissues, 32 normal renal tissues and 32 paracancer tissues and its correlation with the clinicopathologic features of the tumor was evaluated.Results: Telomerase activity was strongly positive in 17, positive in 12 and negative in 3 cases of renal cell carcinoma tissues, the total positive rate being 91%. Telomerase activity was weakly positive (6%) in only 2 out of 32 samples of normal renal cortex tissues and positive in 6 paracancer tissues (19%), the difference was conspicuous (P<0.01).Conclusion: The positive rate of telomerase activity was significantly higher in renal cell carcinoma tissues and might serve as a prognostic marker for estimating the biologic characteristics of renal cell carcinoma.

Telomere and telomerase in chronic liver disease and hepatocarcinoma

The pathogenesis of liver cirrhosis is not completely elucidated.Although in the majority of patients,the risk factors may be identified in B and C viral hepatitis,alcohol intake,drugs or fatty liver disease,there is a small percentage of patients with no apparent risk factors.In addition,the evolution of chronic liver disease is highly heterogeneous from one patient to another.Among patient with identical risk factors,some rapidly progress to cirrhosis and hepatocellular carcinoma(HCC)whereas others have a benign course.Therefore,a genetic predisposition may contribute to the development of cirrhosis and HCC.Evidence supporting the role of genetic factors as a risk for cirrhosis has been accumulating during the past years.In addition to the results from epidemiological studies,polymorphisms studies and data on twins,the concept of telomere shortening as a genetic risk factor for chronic liver disease and HCC has been proposed.Here we review the literature on telomerase mutations,telomere shortening and liver disease including hepatocellular carcinoma.

Influence of the h TERT rs2736100 polymorphism on telomere length in gastric cancer

AIM: To investigate the functional consequences of rs2736100 polymorphism in telomere length and examine its link to gastric cancer risk.METHODS: Telomere length and human telomerase reverse transcriptase(h TERT) m RNA expression were measured in 35 gastric cancer tissues and 5 cell lines and correlated to rs2736100 polymorphism. The relationship between rs2736100 polymorphism and the risk of gastric cancer were examined in 243 gastric cancer patients and 246 healthy individuals.RESULTS: The rs2736100 A allele carrier is closely associated with reduced h TERT m RNA expression and shortened telomere length in gastric cancer tissue and cell lines. When gastric cancers were stratified by histological subtype,telomere length and h TERT m RNA levels were significantly increased in those with the C/C genotype in intestinal-type gastric cancer,but not in diffuse-type gastric cancer. Interestingly,there was no significant difference in the genotype and allele frequencies of the rs2736100 polymorphism between the patients with gastric cancer and healthy controls.CONCLUSION: The rs2736100 polymorphism of the h TERT gene is involved in the regulation of h TERT expression and telomere length,but not in the risk of gastric cancer.

Estrogen deficiency leads to telomerase inhibition, telomere shortening and reduced cell proliferation in the adrenal gland of mice

Estrogen deficiency mediates aging, but the underlying mechanism remains to be fully determined. We report here that estrogen deficiency caused by targeted disruption of aromatase in mice results in significant inhibition of telomerase activity in the adrenal gland in vivo. Gene expression analysis showed that, in the absence of estrogen, telomerase reverse transcriptase （TERT） gene expression is reduced in association with compromised cell proliferation in the adrenal gland cortex and adrenal atrophy. Stem cells positive in c-kit are identified to populate in the parenchyma of adrenal cortex. Analysis of telomeres revealed that estrogen deficiency results in significantly shorter teiomeres in the adrenal cortex than that in wild-type （WT） control mice. To further establish the causal effects of estrogen, we conducted an estrogen replacement therapy in these estrogen-deficient animals. Administration of estrogen for 3 weeks restores TERT gene expression, telomerase activity and cell proliferation in estrogen-deficient mice. Thus, our data show for the first time that estrogen deficiency causes inhibitions of TERT gene expression, telomerase activity, telomere maintenance, and cell proliferation in the adrenal gland of mice in vivo, suggesting that telomerase inhibition and telomere shortening may mediate cell proliferation arrest in the adrenal gland, thus contributing to estrogen deficiency-induced aging under physiological conditions.

Telomere and telomerase in the initial stage of immortalization of esophageal epithelial cell

AIM: To search for the biomarker of cellular immortalization, the telomere length, telomerase activity and its subunits in cultured epithelial cells of human fetal esophagus in the process of immortalization. METHODS: The transgenic cell line of human fetal esophageal epithelium (SHEE) was established with E(6)E(7) genes of human papillomavirus (HPV) type 18 in our laboratory. Morphological phenotype of cultured SHEE cells from the 6th to 30th passages, was examined by phase contrast microscopy, the telomere length was assayed by Southern blot method, and the activity of telomerase was analyzed by telomeric repeat amplification protocol (TRAP). Expressions of subunits of telomerase, hTR and hTERT, were assessed by RT-PCR. DNA content in cell cycle was detected by flow cytometry. The cell apoptosis was examined by electron microscopy (EM) and TUNEL label. RESULTS: SHEE cells from the 6th to 10th passages showed cellular proliferation with a good differentiation. From the 12th to the 16th passages, many senescent and apoptotic cells appeared, and the telomere length sharply shortened from 23kb to 17kb without expression of hTERT and telomerase activity. At the 20th passage, SHEE cells overcame the senescence and apoptosis and restored their proliferative activity with expression of telomerase and hTERT at low levels, but the telomere length shortened continuously to the lowest of 3kb. After the 30th passage cells proliferation was restored by increment of cells at S and G2M phase in the cell cycle and telomerase activity expressed at high levels and with maintenance of telomere length. CONCLUSION: At the early stage of SHEE cells, telomeres are shortened without expression of telomerase and hTERT causing cellular senescence and cell death. From the 20th to the 30th passages, the activation of telomerase and maintenance of telomere length show a progressive process for immortalization of esophageal epithelial cells. The expression of telomerase may constitute a biomarker for detection of immortalization of cells.

Mechanisms of cell immortalization mediated by EB viral activation of telomerase in nasopharyngeal carcinoma

Nasopharyngeal carcinoma （NPC） is a common cancer in Southern China and Southeast Asia. The disease is a poorly differentiated carcinoma without effective cure, and the mechanism underlying its development remains largely unknown. Of several factors identified in NPC aetiology in recent years, Epstein-Barr virus （EBV） infection has emerged to be most important. In almost all NPC cells, EBV uses several intracellular mechanisms to cause oncogenic evolution of the infected cells. One such mechanism by which EBV infection induces cellular immortalization is believed to be through the activation of telomerase, an enzyme that is normally repressed but becomes activated during cancer development. Studies show that greater than 85% of primary NPC display high telomerase activity by mechanisms involving EBV infection, consistent with the notion that EBV is commonly involved in inducing cell immortalization. More recently, different EBV proteins have been shown to activate or inhibit the human telomerase reverse transcriptase gene, by modulating intracellular signalling pathways. These findings suggest a new model with a number of challenges towards our understanding, molecular targeting and therapeutic intervention in NPC.

Dynamic alteration of telomerase expression and its diagnostic significance in liver or peripheral blood for hepatocellular carcinoma

AIM： To investigate the dynamic alteration of telomerase expression during development of hepatocellular carcinoma （HCC） and its diagnostic implications in liver tissues or peripheral blood mononuclear cells for HCC. METHODS： Dynamic expressions of liver telomerase during malignant transformation of hepatocytes were observed in Sprague-Dawly （SD） rats fed with 0.05% of 2-fluoenyacetamide （2-FAA）. Total RNA and telomerase were extracted from rat or human liver tissues. The telomerase activities in livers and in circulating blood were detected by a telomeric repeat amplification protocol-enzyme-linked immunosorbent assay （TRAP- ELISA）, and its diagnostic value was investigated in patients with benign or malignant liver diseases. RESULTS： The hepatoma model displayed the dynamic expression of hepatic telomerase during HCC development. The telomerase activities were consistent with liver total RNA levels （r = 0.83, P 〈 0.01） at the stages of degeneration, precancerosis, and cancerization of hepatocytes. In HCC patients, the telomerase levels in HCC tissues were significantly higher than in their adjacent non-cancerous tissues, but liver total RNA levels were lower in the former than in the latter. Although the circulating telomerase of HCC patients was abnormally expressed among patients with chronic liver diseases, the telomerase activity was a non-specific marker for HCC diagnosis, because the incidence was 15.7% in normal control, 25% in chronic hepatitis, 45.9% in liver cirrhosis, and 85.2% in HCC, respectively when absorbance value of telomerase activity was more than 0.2. If the value was over 0.6, the incidence was 60% in HCC group and 0% in any of the others （P 〈 0.01） except in two cases with liver cirrhosis. However, the combination of circulating telomerase with serum alpha-fetoprotein level could increase the positive rate and the accuracy （92.6%, 125 of 135） of HCC diagnosis. CONCLUSION： The overexpression of telomerase is associated with HCC development, and its abnormality in liver tissues or in peripheral blood could be a useful marker for diagnosis and prognosis of HCC.

Clinical significance of telomerase and its associate genes expression in the maintenance of telomere length in squamous cell carcinoma of the esophagus

AIM: To observe the interaction between the expression of telomerase activity (TA) and its associate genes in regulation of the terminal restriction fragment length(TRFL) in esophageal squamous cell carcinoma (SCC).METHODS: Seventy-four specimens of esophageal SCC were examined. The TA was measured by telomeric repeat amplification protocol (TRAP) assay, and the associated genes [human telomerase-specific reverse transcriptase (hTERT), hTERC, TP1, c-Myc, TRF1,and TRF2] were detected using RT-PCR method. The TRFL was measured by Telomere Length Assay Kit and Southern blotting. The correlations between the expression of telomerase and its associated genes with the TRFL and survivals were examined.RESULTS: Expressions of the TA, hTERT, hTERC, TP1,c-Myc, TRF1, and TRF2 genes were observed in 85.1%,64.9%, 79.7%, 100.0%, 94.6%, 82.4%, and 91.9% of the tumor tissues, respectively. The TRFL of the tumor and normal esophageal tissues were 2.70±1.42 and 4.93±1.74 kb, respectively (P＜0.0001). The TRFL of the telomerase positive and telomerase negative tumor tissues were 2.72±1.44 and 2.58±1.32 kb, respectively (P = 0.767).The TRFL ratios (TRFLR) of the telomerase positive and telomerase negative tumor tissues were 0.55±0.22 and 0.59±0.41, respectively (P = 0.742). The expression rates of h-TERT (P = 0.0002), hTERC (P＜0.0001), and TRF1(P = 0.002) in the tumor tissues are higher than those of the normal paired tissues. Though TA is markedly activated in tumor tissues (P＜0.0001), its expression is not related to clinicopathological parameters including gender, tumor differentiation, and TNM stages. The cumulative 4-year survival rates of telomerase positive and telomerase negative cases were 35.86% and 31.2%,respectively (P = 0.8442). The cumulative 4-year survival rates of patients with their TRFLR ≤85% and ＞85%were 38.7% and 15.7%, respectively (P = 0.1307).CONCLUSION: Though telomerase expression is not related to tumor stages and prognosis, our data support that the TA increased as the TRFL decreased,probably under the control of hTERT, hTERC, and TRF1.When telomerase expression was activated, only TRF2overexpression persisted to stabilize T-loop formation.Furthermore, as the TRFLR decreased to 85%, a trend of better prognosis was observed. Cox model analysis indicates a higher t/n TRFLR and distant metastasis are independent poorer prognostic factors (P = 0.035 and P = 0.042, respectively).

Effects of cisplatin on telomerase activity and telomere length in BEL-7404 human hepatoma cells

Telomerase activity was inhibited in a dose and time-dependent manner with the treatment of cisplatin for 24, 48, or 72 h in a concentration ranged from 0.8 to 50 1uM in BEL-7404 human hepatoma cells. There were no changes in expression pattern of three telomerase subunits, its catalytic reverse transcriptase subunit (hTERT), its RNA component (hTR) or the associated protein subunit (TP1), after cisplatin treated for 72 h with indicated concentrations. Mean telomere lengths were decreased by the cisplatin treatment. Cell growth inhibition and cell cycle accumulation in G2/M phase were found to be correlated with telomerase inhibition in the present study, but percentages of cell apoptosis did not change markedly during the process.

A study of the relationship between expression level of TRF1 protein and telomerase activity in human acute leukemia

Objective： To study the expression level of TRF1 （telomeric repeat binding factor 1） protein in human acute leukemia and relationship between expression level of TRF1 protein and telomerase, Methods： A quantitative Western±Blot technique was developed using anti±TRF1^33±277 monoclonal antibody and GST±TRFI purity protein as a standard to further determine the expression level of TRF1 protein in total proteins extracted from clinical specimens. Results： Bone marrow tissues of 20 acute leukemia patients were studied, 11 healthy donors＇ bone marrows were taken as a control. The expression level of TRF1 protein was significantly higher （P〈0.01） in normal bone marrow （（2.2174±0.462） μg/μl） than that of acute leukemia patients （（0.7544±0.343） μg/μl）, But there was no remarkable difference between ALL and ANLL patients （（0.6184±0.285） μg/μl vs （0.8454±0.359） μg/μl, P〉0.05）. After chemotherapy, TRFI expression level of patients with complete remission elevated （（0.7724±0.307）/μg/μl vs （1.6834±0,344）μg/μl, P〈0.01 ）, but lower than that of normal （（2.2174±0.462）/μg/μl, P〈0.01）. There was no significantly difference after chemotherapy （（0.7264±0.411） μg/μl vs （0.895±0.339） μg/μl,p〉0.05）. TRF1 expression level of patients with complete remission is higher than that of patients without complete remission （（1,683±0.344）μg/μl vs （0.895±0.339）μg/μl P〈0.01）. All samples were determined for telomerase activity. It was confirmed that the activity of telomerase in normal bone marrow was lower than that of acute leukemia patients （（0.125±0.078） μg/μl vs （0.765±0.284）μg/μl, P〈0.01）. There was no significant difference of expression level ofTRF I protein between ALL and ANLL patients （（0.897±0.290） μg/μl vs （0.677±0.268） μg/μl, P〉0.05）. After chemotherapy, telomerase activity of patients with complete remission decreased （（0.393±0.125） μg/μl）, but was still higher than that of normal （（0.125±0.078） μg/μl, P〈0.01）. Conclusion： The expression level of TRF1 protein has correlativity to the activity of telomerase （P〈0.001）.

Association between Physical Activity and Telomere Length in a North Chinese Population： A China Suboptimal Health Cohort Study

Several studies have demonstrated an association between physical activity and telomere length; however, the association remains inconsistent. A cross-sectional study consisting of 588 participants （375 females, median age of 33.8 years） was carried out to investigate the association between telomere length and physical activity in a general population from North China. The results show that relative telomere length is not significantly different in participants in the northern Chinese population with different levels of physical activity, either in the model only adjusted for age （F = 2.127, P = 0.120） or in the model adjusted for demographics and lifestyle （F = 1.227, P = 0.294）. The gender-stratified analysis also produced insignificant results. Our study confirmed a non-significant association between physical activity and telomere length in the northern Chinese population, which adds to the inconsistent association between physical activity and telomere length across different ethnic populations.

Telomeres and Telomerase: Molecular Views and Perspectives

Telomere, the nucleoprotein structure at the end of eukaryotic linear chromosomes is indispensable for maintaining the genome stability. Telomeric DNA loss is apparent with each cell division, which marks an endpoint to the indefinite replication of the cell by causing replicative senescence that may lead to the programmed cell death. The loss of telomere is normal in cell division and as such after 20 - 40 divisions, telomere becomes too short to facilitate the capping function. Telomere uncapping or chromosomal free end causes a potential threat to the genomic stability and thus leads to the accumulation of chromosomal abnormalities that have been known to play a role in aging and cancer. Telomerase, the ribonucleoprotein complex, and its accessory proteins are required to maintain the telomere sequence. Telomerase plays a key role in maintaining the length of telomere by adding G-rich repeat sequences. Its activity has been found to be quite high in the gametes, stem cells and most importantly tumor cells. Almost 85% of tumor cells compensate for telomere loss aided by telomerase-associated protein complex and shelter in complex or telosome. However, 5% - 10% of the cells undergo telomerase-independent mechanism. This review presents the molecular view of the telomere and telomerase along with its associated complex structures. It also discusses its contrasting role in causing cellular senescence and promoting tumorigenesis.

Telomere dynamics in induced pluripotent stem cells:Potentials for Human disease modeling

Recent advances in reprograming somatic cells from normal and diseased tissues into induced pluripotent stem cells (iPSCs) provide exciting possibilities for generating renewed tissues for disease modeling and therapy. However, questions remain on whether iPSCs still retain certain markers (e.g. aging) of the original somatic cells that could limit their replicative potential and utility. A reliable biological marker for measuring cellular aging is telomere length, which is maintained by a specialized form of cellular polymerase known as telomerase. Telomerase is composed of the cellular reverse transcriptase protein, the integral RNA component, and other cellular proteins (e.g. dyskerin). Mutations in any of these components of telomerase can lead to a severe form of marrow def iciency known as dyskeratosis congenita (DC). This review summarizes recent f indings on the effect of cellular reprograming via iPS of normal or DC patient-derived tissues on telomerase function and consequently on telomere length maintenance. The potentials and challenges of using iPSCs in a clinical setting will also be discussed.