Humans ; Telomere ; metabolism ; Telomere-Binding Proteins ; metabolism

BACKGROUND: Telomeres are simple repeats elements located at each end of the chromosomes of eukaryotic cells. The main function of telomeres is to cap the chromosome end and protect it from enzymatic attack. Telomerase that facilitates the synthesis of telomere has been detected in not only cancer, but also in precancerous lesion. In this study, we compared the telomerase expression between low-grade and high-grade gastric dysplasia. METHODS: The telomerase expression of 43 patients with gastric dysplasia (22 low-grade and 21 high-grade) was evaluated by immunohistochemical staining in tissues. RESULTS: The telomerase expression was much higher in the tissues from the patients with high-grade gastric dysplasia than in those tissues of the patients with low-grade gastric dysplasia. CONCLUSIONS: Activation of telomerase may be related with the malignant potentiality in gastric cells. Further studies are needed to define the role of telomerase in gastric tumorigenesis.
Carcinogenesis ; Eukaryotic Cells ; Humans ; Immunohistochemistry ; Telomerase* ; Telomere

Humans ; Metabolic Syndrome ; Telomerase ; metabolism ; Telomere

PURPOSE: Telomeres, special protein and tandem repeat DNA structure that cap the ends of linear eukaryotic chromosomes, are essential for chromosome structure and stability. Human telomeric DNA is known to shorten by 30~200 bp with each somatic cell division. However, the phase of telomere changes has not been studied extensively. METHODS: Telomere length was analyzed in the peripheral blood mononuclear cells (PBMCs) of 39 normal controls aged from newborn to 72 years by Southern blot hybridization using PharMingen's TeloQunatTM Telomere Length Assay Kit (Becton Dickinson Co.). RESULTS: The mean telomere length of the population was 9.68 kb (range, 5.65~14.40 kb). The length (kb) decreased with age (A) by the following regression: T=10.86 0.04 A (T=telomere length in kb; A=age in years) (r= 0.38; P=0.016). The mean telomere lengths according to age groups were: 10.26 kb for less than 15 years; 9.92 kb for 16 to 40 years; 8.03 kb for over 40 years. The telomere length of over 40 years was significantly shorter than that of less than 15 years (P=0.013), and than that of 16 to 40 years (P=0.011). The phase of telomere changes was evaluated by age subgroups. The shortening was fastest in individuals of age <5, while the length showed a plateau or slight increment in age group between 5 to 35. The length decreased steadily with age by the regression of 12.43+/-0.07 A (r= 0.500; P=0.034) in age group over 35. CONCLUSION: Telomere length of PBMCs decreases with age, and the different phase of telomere length shortening may suggest that the shortening of telomere is not a constant process over lifespan, but a dynamic process that is differently regulated in age groups.
Blotting, Southern ; Cell Division ; Chromosome Structures ; DNA ; Humans ; Infant, Newborn ; Tandem Repeat Sequences ; Telomere Shortening* ; Telomere*

Telomerase is an enzyme that maintains telomeres and prevents telomere shortening, and may be linked with cellular proliferation or the aging process. The purpose was to examine telomerase activity in human chorionic villi from early and term normal pregnancies, and to analyze the correlation of telomerase activity (TA) with MIB-1 & bcl-2. A total of 37 placentae were obtained from 16 early and 21 term pregnancies. TA was assayed by telomeric repeat amplification protocol, and immunohistochemical staining was performed for MIB-1 & bcl-2 expression. TA & MIB-1 expression were strong in early placenta, but bcl-2 was highly expressed in term placentae. Thirteen (81.25%) of 16 early placentae showed TA, but only 2 (9.52%) of 21 term placentae expressed TA (p<0.01). MIB-1 was observed in nuclei of cytotrophoblast, and the expression rate was 16.09% in early placentae and 2.87% in term placentae (p<0.01). bcl-2 was observed only in the cytoplasm of syncytiotrophoblast. Term placenta demonstrated stronger expression of bcl-2 compared to early placentae (p<0.05). These findings suggest that TA, MIB-1 & bcl-2 expression are critically regulated over the course of gestation: cytotrophoblast, main cells of early chorionic villi, may be a common source of telomerase and proliferative activity. The TA showed good correlation with cellular proliferative activity. Syncytiotrophoblast, may be a main source of bcl-2 expression which is stronger in the term placentae.
Aging ; Cell Proliferation ; Chorion* ; Chorionic Villi* ; Cytoplasm ; Humans* ; Placenta ; Pregnancy* ; Telomerase* ; Telomere ; Telomere Shortening ; Trophoblasts

PURPOSE: Sarcomas have rarely been analyzed for telomerase, which is an RNA-dependent DNA polymerase to maintain telomeres and prevent telomere shortening. This study was undertaken to determine telomerase activity and the expression of the telomerase subunits human telomerase RNA (hTR) and telomerase reverse transcriptase (TERT) in soft tissue sarcomas. MATERIALS AND METHODS: Twenty three sarcomas were analyzed for the telomerase activity by a radioactive PCR-based TRAP assay. All of the samples were further investigated for the expression of hTR by in situ hybridization and for TERT and p53 by immunohistochemistry. RESULTS: Telomerase activity was detected in four (17%) samples. Expression of hTR was demonstrated in 11 (48%) cases, whereas TERT was expressed in 20 (87%).Of the four telomerase-positive tumors, three were positive for both hTR and TERT, and one was positive only for TERT. p53 overexpression was observed in nine (39%) tumors. The frequency of p53 expression increased as the tumor grade advanced (p= .064). CONCLUSION: These data indicate that the reactivation of telomerase is an uncommon event in human soft tissue sarcomas. The high frequency of the expression of hTR and TERT in these tumors suggests that telomerase activity may be regulated at the transcriptional level and an additional event leading to telomerase activation exist.
Humans* ; Immunohistochemistry ; In Situ Hybridization ; RNA ; RNA-Directed DNA Polymerase ; Sarcoma* ; Telomerase* ; Telomere ; Telomere Shortening

PURPOSE: An attempt was made to investigate N-nitrosomorpholine (NNM) induced carcinogenic processes in rat liver. MATERIALS AND METHODS: Rats were fed with NNM (200 mg/l) for 7 weeks, after then stopped. Length of telomere and activity of telomerase were analyzed. Hepatocytes were isolated and grown on tissue culture. Heat shock was treated at 43oC, and patterns of cell death ere evaluted by fluorescent study. Nuclei and nucleoli were isolated for analysis of various signal molecules. RESULTS: Shortening of telomere length presented in NNM treated liver, but induction of telomerase was not found. Ex vivo hepatocytes from 10~12th week showed increased heat shock resistance at 43oC. NNM-treated hepatocytes exhibited heat shock induced cell death (necrosis) after 7 hours, whereas the control showed necrosis after 3 hours. The signal molecules related to nucleolar growth revealed increased expression which included B23, C23, p38, Erk1/2 and p120. Partial degradation of B23 and Erk2 was noted in necrosis of NNM treated hepatocytes induced by heat shock. CONCLUSION: The hepatocytes at the stage of 10~12th week in the stop experiment of NNM are situated in the tumour promotion. Those cells showed various metabolic alterations. We found that the increased growth related signals were accompanied with increased heat shock resistance, telomere shortening but no induction of telomerase.
Animals ; Cell Death ; Hepatocytes* ; Hot Temperature ; Liver ; Metabolism* ; Necrosis ; Rats* ; Shock ; Telomerase ; Telomere ; Telomere Shortening

As an important telomere binding protein, TPP1 protects the ends of telomeres and maintains the stability and integrity of its structure and function by interacting with other five essential core proteins (POT1, TRF1, TRF2, TIN2, and RAP1) to form a complex called Shelterin. Recently, researchers have discovered that TPP1 participates in protection of telomeres and regulation of telomerase activity. The relationship between TPP1 and tumorigenesis, tumor progression and treatment has also been investigated. This paper reviews the latest findings of TPP1 regarding to its structure, function and interaction with other proteins involved in tumorigenesis.
Chromosomal Instability ; DNA Damage ; Humans ; Neoplasms ; genetics ; Telomere ; Telomere-Binding Proteins ; chemistry ; physiology

Previous studies have established a correlation between increasing chronological age and risk of cirrhosis. This pattern raised interest in the role of telomeres and the telomerase complex in the pathogenesis of liver fibrosis and cirrhosis. This review aims to summarize and analyze the current understanding of telomere regulation in hepatocytes and lymphocytes and how this ultimately relates to the development of liver fibrosis. Notably, in chronic viral hepatitis, telomere shortening in hepatocytes and lymphocytes occurs in such a way that may promote further viral replication while also leading to liver damage. However, while telomere shortening occurs in both hepatocytes and lymphocytes and ultimately results in cellular death, the mechanisms of telomere loss appear to be initiated by independent processes. The understanding of telomere maintenance on a hepatic and immune system level in both viral and non-viral etiologies of cirrhosis may open doors to novel therapeutic strategies.
Fibrosis ; Hepatitis ; Hepatocytes ; Immune System ; Liver Cirrhosis ; Liver Diseases* ; Liver* ; Lymphocytes ; Telomerase ; Telomere Shortening ; Telomere*

Pluripotent stem cells (PSCs) have the potential to produce any types of cells from all three basic germ layers and the capacity to self-renew and proliferate indefinitely in vitro. The two main types of PSCs, embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), share common features such as colony morphology, high expression of Oct4 and Nanog, and strong alkaline phosphatase activity. In recent years, increasing evidences suggest that telomere length represents another important internal factor in maintaining stem cell pluripotency. Telomere length homeostasis and its structural integrity help to protect chromosome ends from recombination, end fusion, and DNA damage responses, ensuring the divisional ability of mammalian cells. PSCs generally exhibit high telomerase activity to maintain their extremely long and stable telomeres, and emerging data indicate the alternative lengthening of telomeres (ALT) pathway may play an important role in telomere functions too. Such characteristics are likely key to their abilities to differentiate into diverse cell types in vivo. In this review, we will focus on the function and regulation of telomeres in ESCs and iPSCs, thereby shedding light on the importance of telomere length to pluripotency and the mechanisms that regulate telomeres in PSCs.
Animals ; Humans ; Models, Biological ; Pluripotent Stem Cells ; metabolism ; Telomerase ; metabolism ; Telomere ; metabolism ; Telomere Homeostasis