Telomerase activity in human chorionic villi and placenta determined by TRAP and in situ TRAP assay

Dolutegravir-containing HIV therapy reversibly alters mitochondrial health and morphology in cultured human fibroblasts and peripheral blood mononuclear cells

OBJECTIVES

Given the success of combination antiretroviral therapy (cART) in treating HIV viremia, drug toxicity remains an area of interest in HIV research. Despite newer integrase strand transfer inhibitors (InSTIs), such as dolutegravir (DTG) and raltegravir (RAL), having excellent clinical tolerance, there is emerging evidence of off-target effects and toxicities. Although limited in number, recent reports have highlighted the vulnerability of mitochondria to these toxicities. The aim of the present study is to quantify changes in cellular and mitochondrial health following exposure to current cART regimens at pharmacological concentrations. A secondary objective is to determine whether any cART-associated toxicities would be modulated by human telomerase reverse transcriptase (hTERT).

METHODS

We longitudinally evaluated markers of cellular (cell count, apoptosis), and mitochondrial health [mitochondrial reactive oxygen species (mtROS), membrane potential (MMP) and mass (mtMass)] by flow cytometry in WI-38 human fibroblast with differing hTERT expression/localization and peripheral blood mononuclear cells. This was done after 9 days of exposure to, and 6 days following the removal of, seven current cART regimens, including three that contained DTG. Mitochondrial morphology was assessed by florescence microscopy and quantified using a recently developed deep learning-based pipeline.

RESULTS

Exposure to DTG-containing regimens increased apoptosis, mtROS, mtMass, induced fragmented mitochondrial networks compared with non-DTG-containing regimens, including a RAL-based combination. These effects were unmodulated by telomerase expression. All effects were fully reversible following removal of drug pressure.

CONCLUSION

Taken together, our observations indicate that DTG-containing regimens negatively impact cellular and mitochondrial health and may be more toxic to mitochondria, even among the generally well tolerated InSTI-based cART.

Symptoms of Prenatal Depression Associated with Shorter Telomeres in Female Placenta

BACKGROUND

Depression is a common mood disorder during pregnancy impacting one in every seven women. Children exposed to prenatal depression are more likely to be born at a low birth weight and develop chronic diseases later in life. A proposed hypothesis for this relationship between early exposure to adversity and poor outcomes is accelerated aging. Telomere length has been used as a biomarker of cellular aging. We used high-resolution telomere length analysis to examine the relationship between placental telomere length distributions and maternal mood symptoms in pregnancy.

METHODS

This study utilised samples from the longitudinal Grown in Wales (GiW) study. Women participating in this study were recruited at their presurgical appointment prior to a term elective caesarean section (ELCS). Women completed the Edinburgh Postnatal Depression Scale (EPDS) and trait subscale of the State-Trait Anxiety Inventory (STAI). Telomere length distributions were generated using single telomere length analysis (STELA) in 109 term placenta (37-42 weeks). Multiple linear regression was performed to examine the relationship between maternally reported symptoms of depression and anxiety at term and mean placental telomere length.

RESULTS

Prenatal depression symptoms were significantly negatively associated with XpYp telomere length in female placenta (B = -0.098, p = 0.026, 95% CI -0.184, -0.012). There was no association between maternal depression symptoms and telomere length in male placenta (B = 0.022, p = 0.586, 95% CI -0.059, 0.103). There was no association with anxiety symptoms and telomere length for either sex.

CONCLUSION

Maternal prenatal depression is associated with sex-specific differences in term placental telomeres. Telomere shortening in female placenta may indicate accelerated placental aging.

Postnatal Catch-Up Growth Programs Telomere Dynamics and Glucose Intolerance in Low Birth Weight Mice

Low birth weight and rapid postnatal weight gain are independent predictors of obesity and diabetes in adult life, yet the molecular events involved in this process remain unknown. In inbred and outbred mice, this study examines natural intrauterine growth restriction (IUGR) in relation to body weight, telomere length (TL), glucose tolerance, and growth factor gene (Igf1, Igf2, Insr, Igf1r, and Igf2r) mRNA expression levels in the brain, liver, and muscle at 2- and 10 days of age and then at 3- and 9 months of age. At birth, ~15% of the animals showed IUGR, but by 3 and 9 months, half of these animals had regained the same weight as controls without IUGR (recuperated group). At 10 days, there was no difference in TL between animals undergoing IUGR and controls. However, by 3 and 9 months of age, the recuperated animals had shorter TL than the control and IUGR-non recuperated animals and also showed glucose intolerance. Further, compared to controls, Igf1 and Igf2 growth factor mRNA expression was lower in Day 2-IUGR mice, while Igf2r and Insr mRNA expression was higher in D10-IUGR animals. Moreover, at 3 months of age, only in the recuperated group were brain and liver Igf1, Igf2, Insr, and Igf2r expression levels higher than in the control and IUGR-non-recuperated groups. These data indicate that catch-up growth but not IUGR per se affects TL and glucose tolerance, and suggest a role in this latter process of insulin/insulin-like growth signaling pathway gene expression during early development.

Dynamics of leukocyte telomere length in pregnant women living with HIV, and HIV-negative pregnant women: A longitudinal observational study

Background

HIV-mediated inflammation and immune activation can accelerate telomere attrition. In addition, antiretrovirals can inhibit telomerase, possibly shortening telomeres. We examined the longitudinal dynamics of leukocyte telomere length (LTL) during pregnancy in a unique cohort of women living with HIV (WLWH) treated with combination antiretroviral therapy (cART), and HIV-negative control women.

Methods

Blood was collected at three visits during pregnancy, at 13–23, >23–30, and >30–40 weeks of gestation, and for WLWH only, at 6 weeks post-partum. LTL was measured by qPCR and both cross-sectional and longitudinal (MANOVA) models were used to examine possible predictors of LTL among participants who attended all three visits during pregnancy.

Results

Among WLWH (n = 64) and HIV-negative women (n = 41), within participant LTL were correlated throughout pregnancy (p<0.001). LTL was shorter among WLWH at first visit, but this difference waned by the second visit. WLWH who discontinued cART post-partum experienced a decrease in LTL. Longitudinally, LTL was similar in both groups and increased as gestation progressed, a change that was more pronounced among women under 35 years. Among WLWH, both smoking throughout pregnancy (p = 0.04) and receiving a ritonavir-boosted protease inhibitor-based regimen (p = 0.03) were independently associated with shorter LTL.

Conclusions

LTL increases as pregnancy progresses; the reasons for this are unknown but may relate to changes in blood volume, hormones, and/or cell subset distribution. While our observations need confirmation in an independent cohort, our data suggest that although some cART regimens may influence LTL, being on cART appears overall protective and that stopping cART post-partum may negatively impact LTL. The effect of smoking on LTL is clearly negative, stressing the importance of smoking cessation.

The fetal programming of telomere biology hypothesis: an update

Research on mechanisms underlying fetal programming of health and disease risk has focused primarily on processes that are specific to cell types, organs or phenotypes of interest. However, the observation that developmental conditions concomitantly influence a diverse set of phenotypes, the majority of which are implicated in age-related disorders, raises the possibility that such developmental conditions may additionally exert effects via a common underlying mechanism that involves cellular/molecular ageing-related processes. In this context, we submit that telomere biology represents a process of particular interest in humans because, firstly, this system represents among the most salient antecedent cellular phenotypes for common age-related disorders; secondly, its initial (newborn) setting appears to be particularly important for its long-term effects; and thirdly, its initial setting appears to be plastic and under developmental regulation. We propose that the effects of suboptimal intrauterine conditions on the initial setting of telomere length and telomerase expression/activity capacity may be mediated by the programming actions of stress-related maternal-placental-fetal oxidative, immune, endocrine and metabolic pathways in a manner that may ultimately accelerate cellular dysfunction, ageing and disease susceptibility over the lifespan. This perspectives paper provides an overview of each of the elements underlying this hypothesis, with an emphasis on recent developments, findings and future directions.This article is part of the theme issue 'Understanding diversity in telomere dynamics'.

Leukocyte Telomere Length at Birth and During the Early Life of Children Exposed to but Uninfected With HIV After In Utero Exposure to Antiretrovirals

Background

Maternal combination antiretroviral therapy (cART) during pregnancy could impact the health of human immunodeficiency virus (HIV)-exposed, HIV-uninfected (HEU) children, because some antiretrovirals cross the placenta and can inhibit telomerase. Our objective was to compare leukocyte telomere length (LTL) in HEU children and HIV-unexposed, HIV-uninfected (HUU) children at birth and in early life and to investigate any relationship with cART exposure.

Methods

HEU and HUU children's blood LTL was compared cross-sectionally at birth, and during the first three years of life. Longitudinal HEU LTL dynamics was evaluated over that same period.

Results

At birth, the LTL in HEU children (n = 114) was not shorter than that in HUU children (n = 86), but female infants had longer LTL than male infants. Maternal cART (duration or type) showed no association with shorter infant LTL. Among 214 HEU children age- and sex-matched at a 1:1 ratio to HUU children, LTL declined similarly in both groups. In a longitudinal analysis, LTL attrition in HEU children was rapid from birth to 1 year of age and gradual thereafter. Zidovudine prophylaxis did not significantly alter LTL.

Conclusions

Our results indicate that from birth to 3 years of age, the LTL in HEU children is not negatively affected by exposure to maternal HIV infection and cART, at least not to the regimens used within this Canadian cohort, a reassuring finding.

Telomere length heterogeneity in placenta revealed with high-resolution telomere length analysis

INTRODUCTION

Telomeres, are composed of tandem repeat sequences located at the ends of chromosomes and are required to maintain genomic stability. Telomeres can become shorter due to cell division and specific lifestyle factors. Critically shortened telomeres are linked to cellular dysfunction, senescence and aging. A number of studies have used low resolution techniques to assess telomere length in the placenta. In this study, we applied Single Telomere Length Analysis (STELA) which provides high-resolution chromosome specific telomere length profiles to ask whether we could obtain more detailed information on the length of individual telomeres in the placenta.

METHODS

Term placentas (37-42 weeks) were collected from women delivering at University Hospital of Wales or Royal Gwent Hospital within 2 h of delivery. Multiple telomere-length distributions were determined using STELA. Intraplacental variation of telomere length was analysed (N = 5). Telomere length distributions were compared between labouring (N = 10) and non-labouring (N = 11) participants. Finally, telomere length was compared between female (N = 17) and male (N = 20) placenta.

RESULTS

There were no significant influences of sampling site, mode of delivery or foetal sex on the telomere-length distributions obtained. The mean telomere length was 7.7 kb ranging from 5.0 kb to 11.7 kb across all samples (N = 42) and longer compared with other human tissues at birth. STELA also revealed considerable telomere length heterogeneity within samples.

CONCLUSIONS

We have shown that STELA can be used to study telomere length homeostasis in the placenta regardless of sampling site, mode of delivery and foetal sex. Moreover, as each amplicon is derived from a single telomeric molecule, from a single cell, STELA can reveal the full detail of telomere-length distributions, including telomeres within the length ranges observed in senescent cells. STELA thus provides a new tool to interrogate the relationship between telomere length and pregnancy complications linked to placental dysfunction.

DNA methylation mediated up-regulation of TERRA non-coding RNA is coincident with elongated telomeres in the human placenta

STUDY QUESTION

What factors regulate elongated telomere length in the human placenta?

SUMMARY ANSWER

Hypomethylation of TERRA promoters in the human placenta is associated with high TERRA expression, however, no clear mechanistic link between these phenomena and elongated telomere length in the human placenta was found.

WHAT IS KNOWN ALREADY

Human placenta tissue and trophoblasts show longer telomere lengths compared to gestational age-matched somatic cells. However, telomerase (hTERT) expression and activity in the placenta is low, suggesting a role for an alternative lengthening of telomeres (ALT). While ALT is observed in 10-15% of human cancers and in some mouse stem cells, ALT has never been reported in non-cancerous human tissues.

STUDY DESIGN, SAMPLES/MATERIALS, METHODS

Human term placental tissue and matched cord blood mononuclear cells (CBMCs) were collected as part of the Peri/Postnatal Epigenetic Twins study (PETS). In addition, first trimester placental villi, purified cytotrophoblasts, choriocarcinoma cell lines and a panel of ALT-positive cancer cell lines were tested. Telomere length was determined using the Terminal Restriction Fragment (TRF) assay and a relative quantitative PCR method. DNA methylation levels at several CpG rich subtelomeric TERRA promoters were determined using bisulfite conversion and the SEQUENOM EpiTYPER platform. Expression of TERRA and hTERT was determined using quantitative RT-PCR. ALT was assessed using the C-circle assay (CCA).

MAIN RESULTS AND THE ROLE OF CHANCE

The human placenta tissue and purified first trimester trophoblasts showed low subtelomeric (TERRA) DNA methylation compared to matched CBMCs and other somatic cells. Interestingly placental TERRA methylation was lower than ALT-cancer cell lines, previously reported to be hypomethylated at these loci. Low TERRA methylation was associated with higher expression of TERRA RNA in placenta compared to matched CBMCs. Detectable levels of C-circles were observed in first trimester placental villi, but not term placenta, suggesting that the ALT mechanism may be active in specific placental cells in early gestation. C-circle analysis of purified first trimester trophoblasts and ALT-associated PML bodies (APB) staining of first trimester villi cross-sections failed to identify this specific cell type population.

LIMITATIONS, REASONS FOR CAUTION

While first trimester villi showed detectable levels of C-circles, these levels were very low compared with those observed in ALT-positive tumours and cell lines. This is consistent with a small sub-population of ALT-positive cells but this requires further investigation. Finally, no mechanistic link was established between TERRA DNA methylation, the presence of C-circles and longer telomere length.

WIDER IMPLICATIONS OF THE FINDINGS

Given the previously described role of TERRA ncRNA as a negative regulator of telomerase, the finding of elevated TERRA and long telomeres is counterintutive. ALT as a mechanism for telomere length maintenance has only been reported in certain human cancers, and recently in mouse embryonic stem cells and embryos. As with many aspects of cancer, it appears that ALT activity in tumours may be the inappropriate activation of a pathway found in very specific cell types in human development. Our data are the first supportive evidence for ALT in a non-cancerous human tissue, a result that requires further investigation and replication. The level of TERRA methylation in the human placenta is significantly lower than found in ALT cancer cell lines and somatic cells, raising the possibility of a novel mechanism in maintaining low methylation at subtelomeric regions.

LARGE SCALE DATA

Not applicable.

STUDY FUNDING AND COMPETING INTERESTS

This study was supported by NHMRC early career fellowship (B.N.), NHMRC Senior Research Fellowship (R.S.) and the Victoria Government Infrastructure Grant. R.R. holds a patent for the C-circle assay. No other conflicts declared.

Placental telomere length and risk of placental abruption

OBJECTIVE

To investigate the associations of placental telomere length with placental abruption (PA) risk and interactions between placental telomere length and placental mitochondrial DNA (mtDNA) copy number on PA risk.

MATERIALS AND METHODS

Relative telomere length and mtDNA copy number in placental samples collected from 105 cases and 73 controls were measured in two batches using qRT-PCR. Mean differences in relative telomere length between PA cases and controls were examined. After creating batch-specific median cutoffs for relative telomere length (84.92 and 102.53) and mtDNA copy number (2.32 and 1.42), interaction between the two variables was examined using stratified logistic regression models.

RESULTS

Adjusted mean difference in relative telomere length between PA cases and controls was -0.07 (p > 0.05). Among participants with low mtDNA copy number, participants with short relative telomere length had a 3.07-fold higher odds (95% CI: 1.13-8.38) of PA as compared with participants with long relative telomere length (the reference group). Among participants with high mtDNA copy number, participants with short relative telomere length had a 0.71-fold lower odds (95% CI: 0.28-1.83) of PA as compared with the reference group (interaction p values = 0.03).

CONCLUSION

Findings suggest complex relationships between placental telomere length, mtDNA copy number and PA risk which warrant further larger studies.

Telomerase activity in pregnancy complications (Review)

Telomeres are specific DNA regions positioned at the ends of chromosomes and composed of functional non-coding repeats. Upon cell division, the telomeres decrease in length by a preordained amount. When the telomeres become critically short, cells lose the ability to divide and enter a specific functioning mode designated as 'cellular senescence'. However, human tissues express an enzyme that deters the shrinking of the telomeres, the telomerase. Due to its ability to maintain telomere length, the telomerase slows down and possibly suspends the aging of the cells. In regard to this, solid evidence demonstrates that female human fertility decreases with increased maternal age and that various adverse factors, including alterations in telomerase activity, can contribute to age-associated infertility in women. The fact that telomerase activity is regulated in a time- and location-dependent manner in both embryo and placental tissues, highlights it potential importance to the successful completion of pregnancy. Since maternal age is a crucial determining factor for the success of in vitro and in vivo fertilization, numerous studies have focused on telomerase activity and its correlation with mammalian fertilization, as well as the following cleavage and pre-implantation developmental processes. Associations between telomerase activity and pregnancy complications have been previously observed. Our aim in this review was to summarize and critically discuss evidence correlating telomerase activity with pregnancy complications.

Placental aging and oxidation damage in a tissue micro-array model: an immunohistochemistry study

To evaluate the expression of markers correlated with cellular senescence and DNA damage (8-hydroxy-2'-deoxy-guanosine (8-OHdG), p53, p21, APE1/Ref-1 (APE1), interleukin (IL-6 and IL-8) in placentas from healthy and pathologic pregnancies. This retrospective study considered a placental tissue micro-array containing 92 controls from different gestational ages and 158 pathological cases including preeclampsia (PE), HELLP syndrome (hemolysis, elevated liver enzymes, low platelet count), small for gestational age (SGA) fetuses, and intrauterine growth restriction (IUGR) occurring at different gestational ages. In this study, we demonstrated a significant influence of gestational age on the expression in the trophoblast of 8-OHdG, p53, p21, APE1, and IL-6. In placentas of cases affected by PE, HELLP, or IUGR, there was an increased expression of 8-OHdG, p53, APE1, and IL-6 compared to controls (only IL-8 was significantly decreased in cases). In both groups of pathology between 22- and 34-week gestation and after 34-week gestation, APE1 levels were higher in the trophoblast of women affected by hypertensive disorders of pregnancy than women carrying an IUGR fetus. The cytoplasmic expression of 8-OHdG was increased in placentas in IUGR cases compared to PE or HELLP pregnancies. In cases after 34-week gestation, p21 was higher in SGA and IUGR than in controls and late PE. Moreover, p53 was increased after 34-week gestation in IUGR pregnancies. Placentas from pathological pregnancies had an altered expression of 8-OHdG, p53, p21, APE1, IL-6, and IL-8. The alterations of intracellular pathways involving these elements may be the cause or the consequence of placental dysfunction, but in any case reflect an impaired placental function, possibly due to increased aging velocity in pathologic cases.

Telomere homeostasis in IUGR placentas - A review

Telomeres are nucleoprotein structures located at the termini of chromosomes. They are essential for chromosome stability. Telomeres become shorter due to mitotic cycles and environmental factors. When telomeres are shortened and therefore dysfunctional, cellular senescence occurs and organ dysfunction might develop. During pregnancy, fetal growth restriction secondary to placental insufficiency has been linked to impaired telomere homeostasis in which telomeres are shorter, telomerase is decreased, and compensatory mechanisms of telomere capture are enhanced. These characteristics, along with increased signs of senescence, indicate telomere dysfunction in trophoblasts from placentas affected by intrauterine growth restriction (IUGR). This review summarizes the information currently available regarding telomere homeostasis in trophoblasts from human pregnancies affected by IUGR. Improved understanding of placental physiology might help in the development of treatment options for fetuses with IUGR.

Maternal psychosocial stress during pregnancy is associated with newborn leukocyte telomere length

OBJECTIVE

In adults, one of the major determinants of leukocyte telomere length (LTL), a predictor of age-related diseases and mortality, is cumulative psychosocial stress exposure. More recently we reported that exposure to maternal psychosocial stress during intrauterine life is associated with LTL in young adulthood. The objective of the present study was to determine how early in life this effect of stress on LTL is apparent by quantifying the association of maternal psychosocial stress during pregnancy with newborn telomere length.

STUDY DESIGN

In a prospective study of N = 27 mother-newborn dyads maternal pregnancy-specific stress was assessed in early gestation and cord blood peripheral blood mononuclear cells were subsequently collected and analyzed for LTL measurement.

RESULTS

After accounting for the effects of potential determinants of newborn LTL (gestational age at birth, weight, sex, and exposure to antepartum obstetric complications), there was a significant, independent, linear effect of pregnancy-specific stress on newborn LTL that accounted for 25% of the variance in adjusted LTL (β = -0.099; P = .04).

CONCLUSION

Our finding provides the first preliminary evidence in human beings that maternal psychological stress during pregnancy may exert a "programming" effect on the developing telomere biology system that is already apparent at birth, as reflected by the setting of newborn LTL.

Telomeres and human reproduction

Telomeres mediate biologic aging in organisms as diverse as plants, yeast, and mammals. We propose a telomere theory of reproductive aging that posits telomere shortening in the female germ line as the primary driver of reproductive aging in women. Experimental shortening of telomeres in mice, which normally do not exhibit appreciable oocyte aging, and which have exceptionally long telomeres, recapitulates the aging phenotype of human oocytes. Telomere shortening in mice reduces synapsis and chiasmata, increases embryo fragmentation, cell cycle arrest, apoptosis, spindle dysmorphologies, and chromosome abnormalities. Telomeres are shorter in the oocytes from women undergoing in vitro fertilization, who then produce fragmented, aneuploid embryos that fail to implant. In contrast, the testes are replete with spermatogonia that can rejuvenate telomere reserves throughout the life of the man by expressing telomerase. Differences in telomere dynamics across the life span of men and women may have evolved because of the difference in the inherent risks of aging on reproduction between men and women. Additionally, growing evidence links altered telomere biology to endometriosis and gynecologic cancers, thus future studies should examine the role of telomeres in pathologies of the reproductive tract.

Prenatal stress, telomere biology, and fetal programming of health and disease risk

A substantial body of epidemiological, clinical, cellular, and molecular evidence converges to suggest that conditions during the intrauterine period of life play a critical role in developmental programming to influence subsequent health and susceptibility for common, complex disorders. Elucidation of the biological mechanisms underlying these effects is an area of considerable interest and investigation, and it is important to determine whether these mechanisms are distinct for different health outcomes or whether there are some common underlying pathways that may account for the effects of disparate prenatal and early postnatal conditions on various health and disease risk phenotypes. We propose that telomere biology may represent a common underlying mechanism connecting fetal programming and subsequent health outcomes. It appears that the initial establishment of telomere length and regulation of telomere homeostasis may be plastic and receptive to the influence of intrauterine and other early life conditions. Moreover, telomere homeostasis in various cell types may serve as a fundamental integrator and regulator of processes underlying cell genomic integrity and function, aging, and senescence over the life span. We advance the hypothesis that context- and time-inappropriate exposures to various forms of physiological stress (maternal-placental-fetal endocrine aberrations and immune, inflammatory, and oxidative stresses) during the intrauterine period of development may alter or program the telomere biology system in a manner that accelerates cellular dysfunction, aging, and disease susceptibility over the life span.

Leukocyte telomere length in HIV-infected pregnant women treated with antiretroviral drugs during pregnancy and their uninfected infants

OBJECTIVES

HIV disease can lead to accelerated telomere attrition, although certain drugs used as part of antiretroviral therapy (ART) can inhibit telomerase reverse transcriptase activity. This could in turn lead to shorter telomeres. We hypothesized that HIV and ART exposure would be associated with shorter leukocyte telomere length (TL) in exposed mother/infant pairs compared with controls.

METHODS

In these retrospective and prospective observational cohort studies, TL was evaluated in peripheral blood leukocytes obtained from HIV-infected pregnant women treated with ART and their uninfected infants, and compared with HIV untreated (retrospective cohort) or HIV mothers and their infants (prospective cohort).

RESULTS

In HIV-infected ART-exposed mothers, leukocyte TL was not significantly shorter than that in HIV untreated mothers or HIV controls, nor was their infants' TL significantly different. Cord blood of ART-exposed infants exhibited TL shorter than that from infants born to HIV-negative mothers. Placenta also showed evidence of shorter TL after adjustment for relevant covariates. Factors associated with shorter maternal and infant TL included smoking and the use of drugs of addiction in pregnancy.

CONCLUSIONS

These results suggest that maternal HIV infection or exposure to ART has minimal effect on infant leukocyte TL, a reassuring finding. In contrast, tissues that express higher telomerase activity such as umbilical cord blood and placenta appear comparatively more affected by ART. Smoking and the use of drugs of addiction have a negative impact on maternal and infant leukocyte TL, possibly through oxidative telomere damage.

Increased placental telomerase mRNA in hypertensive disorders of pregnancy

OBJECTIVE

We assessed hTERT mRNA levels in normal versus preeclamptic placental samples, examining hTERT expression levels in different clinical manifestations of hypertensive disorder of pregnancy.

METHODS

We performed a single-site, prospective case-control study of hTERT mRNA levels in placentas from term and preterm pregnancies with hypertensive disorders compared with unaffected pregnancies. Placental biopsies were collected from 61 patients (preeclamptic: 32; non-preeclamptic (control): 29). Total RNA from placenta was isolated and reversely transcribed to c-DNA. A probe-specific real-time quantitative PCR assay was employed to determine the relative expressional levels of hTERT mRNA levels in these placentas from both unaffected and affected pregnancies with different categories of hypertensive disorders including preeclampsia, severe preeclampsia, eclampsia and HELLP syndrome (Hemolysis, Elevated Liver function tests, Low Platelet).

RESULTS

The average ratio of hTERT mRNA levels was 1.73 in the preeclamptic group and 1.02 for control group (p < 0.0001). The hTERT expression levels were elevated for each of the different categories of hypertensive disorders of pregnancy compared with control: HELLP syndrome 1.86, severe preeclampsia 1.81, eclampsia 1.71 and mild preeclampsia 1.63. In addition, hTERT levels were higher in severe than mild preeclampsia (p < 0.01).

CONCLUSIONS

 Elevated hTERT mRNA expression is observed in placentas from pregnancies with different clinical manifestations of hypertensive disorders of pregnancy. The patho-physiological significance of this finding awaits further studies.

Telomeres are shorter in placental trophoblasts of pregnancies complicated with intrauterine growth restriction (IUGR)

OBJECTIVE

Telomeres are nucleoprotein structures located at the termini of chromosomes, and protect them from fusion and degradation. Telomeres are progressively shortened with each mitotic cycle and by environmental factors. We hypothesized that antepartum stress can lead to accelerated telomere shortening in placental trophoblasts, and plays a role in intrauterine growth restriction (IUGR).

METHODS

Placental biopsies were derived from 16 pregnancies complicated with IUGR and from 13 uncomplicated pregnancies. Fluorescence-in-situ protocol was used to determine telomere length. Immunohistochemistry for hTERT was performed to assess telomerase activity. Clinical and histopathological characteristics were collected to ensure that IUGR was secondary to placental insufficiency. Fluorescence-in-situ-hybridization was used to rule out aneuploidy as a reason for shortened telomeres.

RESULTS

The number and intensity of telomeres staining and telomerase activity were significantly lower in the IUGR placentas. No aneuploidy was detected for the chromosomes checked in the placental biopsies.

CONCLUSIONS

Telomeres are shorter in trophoblasts of IUGR placentas.

Short telomeres may play a role in placental dysfunction in preeclampsia and intrauterine growth restriction

OBJECTIVE

Telomeres shorten and aggregate with cellular senescence and oxidative stress. Telomerase and its catalytic component human telomerase reverse-transcriptase regulate telomere length. The pathogenesis of preeclampsia and intrauterine growth restriction involves hypoxic stress. We aimed to assess telomere length in trophoblasts from pregnancies with those complications.

STUDY DESIGN

Placental specimens from 4 groups of patients were studied: severe preeclampsia, intrauterine growth restriction, preeclampsia combined with intrauterine growth restriction, and uncomplicated (control). Telomere length and human telomerase reverse-transcriptase expression were assessed by using quantitative fluorescence-in-situ protocol and immunohistochemistry.

RESULTS

Telomere length was significantly lower in preeclampsia, intrauterine growth restriction, and preeclampsia plus intrauterine growth restriction placentas. More aggregates were found in preeclampsia, but not in intrauterine growth restriction placentas. Human telomerase reverse-transcriptase was significantly higher in the controls compared with the other groups.

CONCLUSION

Telomeres are shorter in placentas from preeclampsia and intrauterine growth restriction pregnancies. Increased telomere aggregate formation in preeclampsia but not in intrauterine growth restriction pregnancies, implies different placental stress-related mechanisms in preeclampsia with or without intrauterine growth restriction.

The isolation and characterization of a novel telomerase immortalized first trimester trophoblast cell line, Swan 71

Studies using first trimester trophoblast cells may be limited by the inability to obtain patient samples and/or adequate cell numbers. First trimester trophoblast cell lines have been generated by SV40 transformation or similar methods, however, this approach is known to induce phenotypic and karyotypic abnormalities. The introduction of telomerase has been proposed to be a viable alternative for the immortalization of primary human cells. To investigate whether telomerase-induced immortalization might be a more feasible approach for the generation of first trimester trophoblast cell lines, we isolated primary trophoblast cells from a 7-week normal placenta and infected the cells with human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase. Although this hTERT-infected first trimester trophoblast cell line, which we have named Swan 71, has been propagated for more than 100 passages, it still has attributes that are characteristic of primary first trimester trophoblast cells. The Swan 71 cells are positive for the expression of cytokeratin 7, vimentin and HLA-G, but do not express CD45, CD68 or the Fibroblast Specific Antigen (FSA), CD90/Thy-1. In addition, we also demonstrated that the Swan 71 cells secrete fetal fibronectin (FFN) as well as low levels of human Chorionic Gonadotrophin (hCG). Moreover, the Swan 71 cells exhibit a cytokine and growth factor profile that is similar to primary trophoblast cells and are resistant to Fas, but not TNF-alpha-induced apoptosis. This suggests that the Swan 71 cells may represent a valuable model for future in vitro trophoblast studies.

Fetal growth restriction is associated with accelerated telomere shortening and increased expression of cell senescence markers in the placenta

A hallmark of fetal growth restriction (FGR) is restricted placental development and insufficient nutrient supply to the fetus. It has previously been shown that activity levels of telomerase, the enzyme responsible for completing replication of telomeric DNA during cell division, is suppressed in FGR placenta samples as compared to control placenta samples from donors of the same gestational age. Here we examine whether telomere length maintenance is also compromised in FGR placenta samples. Southern analysis of telomere length for placenta and cord blood samples from 32 FGR and 36 control donors, ranging in gestational age from 37 to 40 weeks, revealed significantly shorter telomeres (P<or=0.001) in FGR placenta samples, but not cord blood samples. Furthermore, analysis of telomerase extracts, RNA and DNA placental samples from donors with and without idiopathic FGR confirmed a direct association between suppression of telomerase activity and reduced telomere length in FGR placenta. In addition, expression levels of markers of telomere-induced senescence, p21, p16 and EF-1 alpha, were significantly elevated in FGR placenta samples (P<or=0.01). These observations support a direct affect of reduced telomerase activity levels on the placental pathology associated with FGR.

Telomerase activity of chorionic trophoblasts in preterm premature rupture of membranes

Premature rupture of membranes (PROM) is a complication associated with preterm birth. Because most neonatal death, morbidity, and cost are linked to preterm birth, understanding the mechanisms for developing preterm PROM (pPROM) is critical. The aim of this study is to investigate whether telomerase activity of the chorionic trophoblasts may play a role in the pathogenesis of PROM. Placental membranes were collected from 56 patients with pPROM and 45 patients with preterm labor (PTL). Telomerase activity was assessed by immunohistochemistry, and telomerase activity index (TAI) was calculated for both groups. Results are expressed as the mean +/- standard deviation. Differences between groups were analyzed using an independent-samples t-test. To evaluate other suggested mechanisms, such as apoptosis and extracellular matrix degradation, immunohistochemistry for matrix metalloproteinase (MMP)-9, tissue inhibitor of metalloproteinase (TIMP)-3, and M30 CytoDEATH antibodies were also performed. The TAI was found to be 6.8 +/- 3.2 for PTL, while it was 2.5 +/- 1.5 for pPROM. Decreased TAI was statistically significant in pPROM membranes in comparison with PTL (P < 0.001). Number of apoptotic trophoblasts was significantly increased for the membranes of pPROM (P < 0.001), whereas strong staining of MMP-9 and TIMP-3 was found for chorionic trophoblasts as well as for other cells in both groups. Although study of the pPROM has focused on activation of matrix metalloproteinases and apoptosis that result in the consequence of a programmed membrane weakening process, decreased telomerase activity of chorionic trophoblasts is likely to have a contributing role in the pathogenesis of pPROM as well.

Telomerase and apoptosis in the placental trophoblasts of growth discordant twins

In an effort to investigate the molecular basis of growth discordance in embryos that experience the same uterine environment, we compared telomerase activity and apoptosis in placental trophoblasts obtained from growth discordant twins. Between January 2003 and February 2005, placental tissue from twenty pairs of twins was obtained within thirty minutes of delivery. Eleven cases were classified as growth discordant, with birth weight discordance greater than 20%. Nine cases comprised the control group, with less than 20% discordance. Telomerase and apoptotic activities in placental trophoblasts were analyzed by ELISA and immunoblot. Statistical significance was analyzed by a paired t-test, chi- squared test, and ANOVA (SPSS ver 11.0). The average growth discordance was 26.8% in the growth discordant group and 14.4% in the control group. There were no significant differences in maternal age, week of gestation at delivery, parity, or chorionisity between the two groups. In the growth discordant group, the larger twin showed significantly higher telomerase activity (p < 0.01), whereas no significant difference was observed in the control group (p = 0.36). In addition, there was no definitive correlation between telomerase activity and the degree of growth discordance in the larger or smaller twins (R = -0.521 and -0.399, p = 0.15 and 0.25, respectively). The apoptosis proteins Bax and Bcl 2 were detected in both the larger and smaller twins in the growth discordant and control groups. There was no statistically significant difference in Bax expression between the larger and smaller twins (p = 0.25 and 0.92, respectively) for either the growth discordant or the control groups. Bcl 2 expression also showed no significant difference between groups. In conclusion, a tendency toward reduced telomerase activity and increased apoptosis was discovered in placental trophoblasts of the smaller growth- discordant twin, possibility resulting in delayed fetal growh.

Long telomeres in the mature human placenta

OBJECTIVE

To investigate whether telomere shortening may play a role in senescence of the placenta.

STUDY DESIGN

Villous tissue was collected from single, random sites of full-term placentas (39-41 weeks of gestation; n=10) as well as multiple, specific sites of the same placenta (39-41 weeks of gestation; n=5). For the latter group of placentas, samples were taken near the umbilical cord and at the periphery on both the maternal and fetal sides (a total of 4 samples per placenta). Cord blood samples were also obtained from all placental donors. Telomerase activity was assessed by the TRAP assay, and telomere length measured by Southern analysis of mean terminal restriction fragment (TRF) length.

RESULTS

We show for the first time that telomeres are longer ( approximately 25% longer; P<0.001) in placenta tissue than in cord blood from the same donor.

CONCLUSION

Telomere shortening is unlikely to have a significant role in senescence or terminal maturation of the placenta.

Regulation of telomerase during human placental differentiation: a role for TGFbeta1

The transient tumor-like attributes of the first-trimester placenta anchor the developing embryo to the uterine wall thus establishing a vital link between the mother and the fetus. Dysregulation of this invasive behavior and/or controlled proliferation of the placenta is associated with abnormal pregnancies. Several of these diseased states also exhibit aberrant telomerase activity, among other pathophysiological manifestations. Considering the strong correlation between telomerase activity and tumorigenesis, it was of interest to see whether the crucial processes of trophoblast proliferation and differentiation were brought about through the modulation of telomerase. Using two in vitro model systems of trophoblast differentiation, we demonstrate here that telomerase activity is negatively regulated during placental differentiation. We further show that this modulation is at the level of transcription of hTERT. We also propose a role for TGF beta1 in regulating telomerase activity in differentiating trophoblasts by down-regulating the expression of hTERT at the transcriptional level.

Telomerase activity and apoptosis as indicators of ageing in placenta with and without intrauterine growth retardation

Telomerase activity (TA) and apoptosis were analysed in placenta with and without intrauterine growth retardation (IUGR). Thirty-one specimens were taken from chorionic villi in the first trimester (Group A), 32 placenta specimens were obtained from cases without IUGR in second and third trimester (Group B) and 12 specimens of placenta tissue were obtained from cases of asymmetric IUGR between 26 and 39 weeks of gestation (Group C). TA was analysed by the Telomeric Repeat Amplification Protocol (TRAP) and in situ TRAP assay. Apoptotic changes were assessed by immunohistochemical staining using Bcl-2 monoclonal antibody and by terminal transferase-mediated in situ end-labelling (TUNEL). TA was detected in 29 of the 31 (93.5 per cent) chorionic villi (Group A) and in 20 of the 32 (62.5 per cent) placenta without IUGR (Group B), whereas weak TA was observed in the placenta of all 12 asymmetric IUGR cases (Group C). Significantly higher Bcl-2 immunoreactivity was observed in trophoblastic cells of Group A (85.9+/-4.2 per cent) and Group B (72.8+/-7.2 per cent) than Group C (54.84+/-4.83 per cent), while TUNEL positive cells were identified at a significantly higher frequency in the trophoblastic cells of Group C (9.7+/-7.4 per cent) than Group A (1.1+/-1.9 per cent) or Group B (2.9+/-3.7 per cent).