How long should telomeres be?

In utero exposure to endocrine-disrupting chemicals and telomere length at birth

Telomere length correlates with morbidity and mortality. While telomere length appears to be influenced by hormone levels, the potential impact of exposure to endocrine-disrupting chemicals (EDCs) has not been studied. We examined the association between maternal gestational concentrations of biomarkers of EDC exposure and telomere length at birth in the Harvard Epigenetic Birth Cohort. EDC (phenols and phthalates) biomarker concentrations were measured in maternal spot urine samples during the first trimester and telomere length in maternal and cord blood collected at delivery among 181 mother-newborn singleton dyads. Maternal and newborn telomere length exhibited a positive correlation (Spearman ρ = 0.20 (p-value< 0.01). Infant telomere length was associated with maternal biomarker concentrations of specific EDCs, and most of these associations were observed to be infant sex-specific. Prenatal exposure to triclosan, a non-paraben phenol with antimicrobial properties, was one of the most strongly associated EDCs with telomere length; telomere length was 20% (95% CI 5%-33%) shorter among boys in the highest quartile of maternal biomarker concentrations compared to the lowest quartile. In contrast, we observed longer telomere length associated with increased gestational concentrations of mono-isobutyl phthalate, and among boys, with increased concentrations of mono-2-ethylhexyl phthalate. In this birth cohort, we observed associations between maternal gestational exposure to select EDC biomarkers and telomere length, most of which were sex-specific. These findings need to be confirmed in future studies.

Telomere length in the colon is related to colorectal adenoma prevalence

Telomere length has been associated with risk of several cancers. However, studies of the relationship between telomere length and colorectal cancer risk have been inconsistent. This study examined the relationship between telomere length in normal colon tissue and the prevalence of colorectal adenoma, a precursor to colorectal cancer. This nested case-control study consisted of 85 patients aged 40 to 65 undergoing a screening colonoscopy: 40 cases with adenoma(s) detected at colonoscopy and 45 controls with normal colonoscopy. During the colonoscopy, two pinch biopsies of healthy, normal appearing mucosa were obtained from the descending colon. Relative telomere length (rTL) was quantified in DNA extracted from colon mucosa using quantitative real-time PCR. Logistic regression was used to assess the relationship between telomere length and adenoma prevalence and estimate odds ratios and 95% confidence intervals. rTL was significantly longer in colon tissue of individuals with adenomas compared to healthy individuals (p = 0.008). When rTL was categorized into quartiles according to the distribution of rTL among controls, individuals with the longest telomeres had increased odds of adenoma when compared to individuals with shortest telomeres (OR = 4.58, 95% CI: 1.19, 17.7). This study suggests that long telomeres in normal colon tissue are associated with increased colorectal cancer risk.

The NVL gene confers risk for both major depressive disorder and schizophrenia in the Han Chinese population

NVL (nuclear VCP (valosin containing protein)/p97-Like), a member of the AAA-ATPase (ATPases associated with various cellular activities) family, encodes a novel hTERT (human telomerase reverse transcriptase)-interacting protein NVL2 which is a telomerase component essential for holoenzyme assembly. Previous researches have reported the impacts of telomerase activity on mental illness and the potential association between NVL and major depressive disorder. To validate the susceptibility of NVL to major depressive disorder, and to investigate the overlapping risk conferred by NVL for both major depressive disorder and schizophrenia, we analyzed 9 tag single nucleotide polymorphisms (tag SNPs) using TaqMan® technology, in 1045 major depressive disorder patients, 1235 schizophrenia patients and 1235 normal controls of Han Chinese origin. We found that rs10916583 (P(allele) = 0.020, P(genotype) = 0.028, OR = 1.156) and rs16846649 (adjusted P(allele) = 0.014, P(genotype) = 0.007, OR = 0.718) were associated with major depressive disorder, while rs10916583 (adjusted P(allele) = 1.08E-02, OR = 1.213), rs16846649 (adjusted P(allele) = 7.40E-06, adjusted P(genotype) = 8.07E-05, OR = 0.598) and rs10799541 (adjusted P(allele) = 8.10E-03, adjusted P(genotype) = 0.049, OR= 0.826) showed statistically significant association with schizophrenia after Bonferroni correction. Furthermore, rs10916583 (adjusted P(allele) = 9.00E-03, adjusted P(genotype) = 3.15E-02, OR = 1.187) and rs16846649 (adjusted P(allele) = 8.92E-06, adjusted P(genotype) = 8.84E-05, OR = 0.653) remained strongly associated with the analysis of combined cases of major depressive disorder and schizophrenia after Bonferroni correction. Our results indicated that the NVL gene may contain overlapping common genetic risk factors for major depressive disorder and schizophrenia in the Han Chinese population. The roles of NVL in telomerase biogenesis were also highlighted in psychiatric pathogenesis. The study on variants conferring overlapping risk for multiple psychiatric disorders could be tangible pathogenesis support and clinical or diagnostic references.

Genome-wide differential gene expression in immortalized DF-1 chicken embryo fibroblast cell line

BACKGROUND

When compared to primary chicken embryo fibroblast (CEF) cells, the immortal DF-1 CEF line exhibits enhanced growth rates and susceptibility to oxidative stress. Although genes responsible for cell cycle regulation and antioxidant functions have been identified, the genome-wide transcription profile of immortal DF-1 CEF cells has not been previously reported. Global gene expression in primary CEF and DF-1 cells was performed using a 4X44K chicken oligo microarray.

RESULTS

A total of 3876 differentially expressed genes were identified with a 2 fold level cutoff that included 1706 up-regulated and 2170 down-regulated genes in DF-1 cells. Network and functional analyses using Ingenuity Pathways Analysis (IPA, Ingenuity® Systems, http://www.ingenuity.com) revealed that 902 of 3876 differentially expressed genes were classified into a number of functional groups including cellular growth and proliferation, cell cycle, cellular movement, cancer, genetic disorders, and cell death. Also, the top 5 gene networks with intermolecular connections were identified. Bioinformatic analyses suggested that DF-1 cells were characterized by enhanced molecular mechanisms for cell cycle progression and proliferation, suppressing cell death pathways, altered cellular morphogenesis, and accelerated capacity for molecule transport. Key molecules for these functions include E2F1, BRCA1, SRC, CASP3, and the peroxidases.

CONCLUSIONS

The global gene expression profiles provide insight into the cellular mechanisms that regulate the unique characteristics observed in immortal DF-1 CEF cells.

Telomere dynamics in rhesus monkeys: no apparent effect of caloric restriction

The role of telomere attrition in limiting the replicative capacity of cells in culture is well established. In humans, epidemiologic evidence suggests telomere length (TL) in leukocytes is highly variable at birth and inversely related to age. Although calorie restriction (CR) significantly increases life span in most rodent models, its association with TL is unknown. Using linear regression analysis, TLs (as measured by Southern blot analysis) of skeletal muscle (a postmitotic tissue that largely represents early development TL), fat, leukocytes, and skin were tested for effects of age, sex, and diet in 48 control and 23 calorie restriction rhesus monkeys. After controlling for the individual's muscle mean TL, differences between leukocytes muscle and skin muscle were significantly associated with age (p = .002; p = .002) and sex (p = .003; p = .042), but not calorie restriction (p = .884; p = .766). Despite an age-dependent shortening of TL in leukocytes and skin, calorie restriction did not significantly affect TL dynamics in these samples.

Development, characterization, conservation and storage of fish cell lines: a review

Cell lines provide an important biological tool for carrying out investigations into physiology, virology, toxicology, carcinogenesis and transgenics. Teleost fish cell lines have been developed from a broad range of tissues such as ovary, fin, swim bladder, heart, spleen, liver, eye muscle, vertebrae, brain, skin. One hundred and twenty-four new fish cell lines from different fish species ranging from grouper to eel have been reported since the last review by Fryer and Lannan (J Tissue Culture Methods 16: 87-94, 1994). Among the cell lines listed, more than 60% were established from species from Asia, which contributes more than 80% of total fish production. This includes 59 cell lines from 19 freshwater, 54 from 22 marine and 11 from 3 brackish water fishes. Presently, about 283 cell lines have been established from finfish around the world. In addition to the listing and a scientific update on new cell lines, the importance of authentication, applications, cross-contamination and implications of overpassaged cell lines has also been discussed in this comprehensive review. The authors feel that the review will serve an updated database for beginners and established researchers in the field of fish cell line research and development.

Genetic pathway of major depressive disorder in shortening telomeric length

CONTEXT

Shortened telomeric length has been associated with aging and monoamine oxidase A gene activity. The pathways of genetic activity and mental disorder in shortening telomeric length, however, remain unclear.

OBJECTIVE

The purpose of this study was to explore the possible pathways of the monoamine oxidase A promoter, ApoE polymorphisms and telomeric length in major depressive disorder.

METHODS

This study enrolled 253 unrelated patients with major depression in southern Taiwan, and was carried out between March 2001 and September 2004. In addition, 411 controls were randomly selected from the general population in southern Taiwan.

RESULTS

Hierarchical regression showed that the influence of the monoamine oxidase A promoter and ApoE2 polymorphisms was not statistically significant to telomeric length, when additionally adjusting for major depressive disorder. A final robust structural equation model showed that aging and major depressive disorder both have a statistically significant shortening effect on telomeric length. Moreover, sex, the Apoepsilon2 allele, and the monoamine oxidase A promoter polymorphism have indirect effects on telomeric length.

CONCLUSION

Major depressive disorder is a mediating factor between the monoamine oxidase A promoter polymorphism and telomeric length.

Characteristics of primary and immortalized fibroblast cells derived from the miniature and domestic pigs

Background

The pig, Sus scrofa domestica includes both the miniature and commercial domestic breed. These animals have influenced the human life and economies and have been studied throughout history. Although the miniature breeds are more recent and have increasingly been used in a variety of biomedical studies, their cell lines have rarely been established. Therefore, we sought to establish primary and immortal cell lines derived from both the miniature and domestic pig to better enable insight into possible in vivo growth differences.

Results

The in vitro lifespan of primary domestic pig fibroblast (PF) and miniature pig fibroblast (MPF) cells using a standard 3T3 protocol was determined. Both of the primary PF and MPF cells were shown to have a two-step replicative senescence barrier. Primary MPF cells exhibited a relatively shorter lifespan and slower proliferation rate compared to those of primary PF cells. Beyond senescence barriers, lifespan-extended PF and MPF cells were eventually established and indicated spontaneous cellular immortalization. In contrast to the immortalized PF cells, immortal MPF cells showed a transformed phenotype and possessed more frequent chromosomal abnormalities and loss of p53 regulatory function. The lifespan of primary MPF and PF cells was extended by inactivation of the p53 function using transduction by SV40LT without any detectable senescent phenotype.

Conclusion

These results suggest that p53 signaling might be a major determinant for the replicative senescence in the MPF cells that have the shorter lifespan and slower growth rate compared to PF cells in vitro.

Arterial baroreflex function does not influence telomere length in kidney of rats

AIM

To investigate the relationship between arterial baroreflex (ABR) function and telomere length in kidney of rats.

METHODS

Stroke-prone spontaneously hypertensive rats (SHR-SP) and sinoaortic denervated rats (SAD) were used as models with depressed arterial baroreflex. In the first experiments, SHR-SP rats were examined at the age of 24 weeks for both sexes and 40 weeks for female rats. In the second experiments, SAD rats were studied 4 and 35 weeks after SAD operation. Blood pressure was continuously recorded for 4 h in a conscious state. After the determination of baroreflex sensitivity (BRS), the terminal restriction fragment (TRF) of rat kidney was analyzed using Southern blot.

RESULTS

The TRF length was found shorter in: a) male SHR-SP compared with age-matched female SHR-SP; b) female SHR-SP 40 weeks of age compared with 24 weeks of age; c) in rats 35 weeks after operation compared with rats 4 weeks post operation in both sham-operated and SAD rats.

CONCLUSION

In SHR-SP, the TRF length did not correlate with BRS. In addition, SAD did not affect TRF length at either 4 or 35 weeks post-surgery. It may be concluded that baroreflex function does not influence the terminal restriction fragment (TRF) length in rats.

Modulation of p53 expression and its role in the conversion to a fully immortalized chicken embryo fibroblast line

We have established a spontaneously immortalized chicken embryo fibroblast (CEF) cell line (SC-1) that has been in continuous culture for more than three years. This is only the second report of a spontaneously immortalized reverse transcriptase (RT)-negative chicken cell line. The SC-1 cells emerged from crisis (at about passage 29-31) with a slower growth rate than primary cells. Passage 50 SC-1 cells expressed similar levels of p53 mRNA, but slightly lower levels of p53 protein than passage 6 CEF cells. By passage 120, p53 mRNA levels were significantly decreased in the SC-1 cells, while protein levels were slightly increased compared to passage 6 CEF cells. However, functional analysis of p53 revealed reduced activity in later passage SC-1 cells. Other p53-related genes including p21WAF1, p27Kip1, MDM-2, and the p16INK4a alternate reading frame (ARF) sequence showed similar patterns of differential mRNA expression. Levels of p15INK4b mRNA and protein were dramatically decreased in SC-1 cells, suggesting that the Rb pathway also has been compromised. Telomerase expression was undetectable in SC-1 cells. Fluorescence-activated cell sorting analysis showed that SC-1 and primary cells contained a similar proportion of G0/G1 phase cells, unlike the only other spontaneously immortalized chicken cell line (DF-1). The present study suggests that alterations in the p53 and Rb pathways cause fluctuations in expression levels of important cell-cycle regulatory genes during crucial transition periods as the SC-1 spontaneously immortalized chicken fibroblast cells progress toward becoming a fully committed cell line.

Age-Dependent Telomere Attrition as a Potential Indicator of Racial Differences in Renal Growth Patterns

BACKGROUND

Racial differences in the predilection to salt sensitivity may arise from different renal growth patterns. To test this idea, we monitored age-dependent telomere attrition rate, reflecting largely the replicative history of somatic cells, in the outer renal cortex and the inner renal medulla of African Americans and Caucasians.

METHODS

Telomere length, determined by the mean length of the terminal restriction fragments (TRF), was measured in specimens from 58 African-American and 63 Caucasian males, ages 1 day to 71 years.

RESULTS

In the outer renal cortex, TRF length attrition rate was significantly slower in African Americans (-0.021 +/- 0.0064 kb/year) than in Caucasians (-0.060 +/- 0.0094 kb/year) (p = 0.0007). In both ethnic groups the TRF length attrition rate was slower in the inner medulla than in the outer renal cortex, but without significant racial differences.

CONCLUSIONS

The proximal tubule is the most abundant nephron structure in the outer renal cortex. Less proliferative growth of proximal tubular cells in kidneys from African Americans may be one factor explaining the slower age-dependent telomere attrition rate in the outer renal cortex of African Americans than in Caucasians.

Chronology versus biology: telomeres, essential hypertension, and vascular aging

There is considerable evidence that essential hypertension is closely linked to the growth, development, and aging of human beings. It is imperative, therefore, to introduce biological indicators of growth and aging into models developed to provide a better understanding of the etiology of essential hypertension. One of these indicators may well be the age-dependent telomere attrition rate in somatic cells. Telomere attrition registers the replicative history of somatic cells. As such, it chronicles not only the growth that results from the replication of somatic cells but also their turnover-a process that is strongly linked to inflammation and oxidative stress, which are key factors in the biology of human aging.

Events in the immortalizing process of primary human mammary epithelial cells by the catalytic subunit of human telomerase

The in vitro immortalization of primary human mammary epithelial (HME) cells solely by the exogenous introduction of the catalytic subunit of human telomerase (hTERT) has been achieved. Early passage hTERT-transfected HME (T-HME) cells continuously decreased the length and density of telomeres even in the presence of telomerase activity, with a significant number of cells staining positive for senescence-associated beta-galactosidase (SA-beta-gal). Subsequently, with the increase in cell passages, the copy number of the exogenously transfected hTERT gene and the percentage of SA-beta-gal positive cells were found to decrease. Eventually, a single copy of the exogenous hTERT gene was observed in the relatively later passage T-HME cells in which telomere length was elongated and stabilized without obvious activation of endogenous hTERT and c-Myc expression. In T-HME cells, the expression of two p53 regulated genes p21(WAF) and HDM2 increased (as in primary senescent HME cells), and was found to be further elevated as the function of p53 was activated by treatment with DNA-damaging agents. p16(INK4a) was shown to be significantly higher in the primary senescent HME and the early passage T-HME cells when compared with the primary presenescent HME cells, with a dramatic repression of p16(INK4a) observed in the later passage T-HME cells. In addition, the expression of E2F1 and its transcription factor activity were found to be significantly higher in the later passage T-HME cells when compared with the earlier passage T-HME cells. Together, our results indicate that in vitro immortalization in HME cells may require the activation of the function of telomerase and other genetic alterations such as the spontaneous loss of p16(INK4a) expression.