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

Pharmacotherapeutic Considerations on Telomere Biology: The Positive Effect of Pharmacologically Active Substances on Telomere Length

Telomeres are part of chromatin structures containing repeated DNA sequences, which function as protective caps at the ends of chromosomes and prevent DNA degradation and recombination, thus ensuring the integrity of the genome. While telomere length (TL) can be genetically inherited, TL shortening has been associated with ageing and multiple xenobiotics and bioactive substances. TL has been characterised as a reliable biomarker for the predisposition to developing chronic pathologies and their progression. This narrative review aims to provide arguments in favour of including TL measurements in a complex prognostic and diagnostic panel of chronic pathologies and the importance of assessing the effect of different pharmacologically active molecules on the biology of telomeres. Medicines used in the management of cardiovascular diseases, diabetes, schizophrenia, hormone replacement therapy at menopause, danazol, melatonin, and probiotics have been studied for their positive protective effects against TL shortening. All these classes of drugs are analysed in the present review, with a particular focus on the molecular mechanisms involved.

Efficacy of a dietary supplement derived from five edible plants on telomere length in Thai adults: A randomized, double-blind, placebo-controlled trial

Mylife/Mylife100® is a dietary supplement consisting of black sesame seed, guava fruit, mangosteen aril, pennywort leaves, and soy protein. These edible plants contain multiple high-potential bioactive compounds exerting various vital biological functions including antioxidants which contribute to delaying the rate of telomere shortening. Telomere length is associated with cellular aging and age-related diseases. This study aimed to assess the efficacy of Mylife/Mylife100® on telomere length through a randomized, double-blind placebo-controlled trial. The trial assessed the alteration of leukocyte telomere length after 32 adults aged 50-65 years received either Mylife/Mylife100® or placebo (five capsules/day) for 8-week supplementation. The results demonstrated a significant increase in mean telomere length from baseline (6313 bp) to the 8-week supplementation period (6655 bp; p < 0.05) in the group receiving the product, whereas no significant change was observed in the placebo group. Additionally, the product group exhibited a significant improvement in plasma total antioxidant capacity levels compared to the placebo group (mean change, +35 vs -38; p = 0.006). This study also showed a significant correlation between telomere length and % CD4 + T cells (r = +0.325; p = 0.00003), % CD8 + T cells (r = +0.156; p = 0.048), and visceral fat (r = - 0.349; p = 0.000006). The findings suggest that consuming this dietary supplement (Mylife/Mylife100®) for 8 weeks has a positive effect on cellular aging by lengthening telomeres possible through their antioxidant capacities. Oxidative stress and cellular aging are underlying predisease mechanisms that might be alleviated by supplementing with this product.

Association between female-specific reproductive factors and leukocyte telomere length

STUDY QUESTION

What are the associations between female-specific reproductive factors and leukocyte telomere length (LTL)?

SUMMARY ANSWER

Early menarche, early menopause, short reproductive lifespan, early age at first birth, multiparity, and use of oral contraceptives (OCs) and hormone replacement therapy (HRT) were associated with shorter LTL.

WHAT IS KNOWN ALREADY

Reproductive factors have been associated with age-related diseases, but their associations with cellular aging, as indicated by LTL, are unclear.

STUDY DESIGN, SIZE, DURATION

This population-based study included 224 965 women aged 40-69 years from the UK Biobank between 2006 and 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women aged 40-69 were included. Female-specific reproductive factors, including age at menarche, age at natural menopause, reproductive lifespan, number of live births, age at first live birth, history of stillbirth, history of miscarriage, and use of OCs and HRT were self-reported. LTL was measured using a validated polymerase chain reaction method. Multiple linear regression and restricted cubic spline models were applied to explore the association between each reproductive factor and LTL.

MAIN RESULTS AND THE ROLE OF CHANCE

After adjustment for potential confounders, early menarche (<12 years; percent change, per unit change in LTL Z score: -1.29%, 95% CI: -2.32%, -0.26%), early menopause (<45 years; percent change: -7.18%, 95% CI: -8.87%, -5.45%), short reproductive lifespan (<30 years; percent change: -6.10%, 95% CI: -8.14%, -4.01%), multiparity (percent change: -3.38%, 95% CI: -4.38%, -2.37%), early age at first live birth (<20 years; percent change: -4.46%, 95% CI: -6.00%, -2.90%), and use of OCs (percent change: -1.10%, 95% CI: -2.18%, -0.02%) and HRT (percent change: -3.72%, 95% CI: -4.63%, -2.80%) were all significantly associated with shorter LTL. However, no significant association was found for history of miscarriage and stillbirth. We observed nonlinear relationships of age at menarche, age at natural menopause, reproductive lifespan, and age at first live birth with LTL (Pnonlinear < 0.05).

LIMITATIONS, REASONS FOR CAUTION

Considering that the participants were predominantly of European ethnicity, the findings may not be generalizable to women of other ethnic backgrounds.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings suggest that early menarche, early menopause, short reproductive lifespan, early age at first birth, multiparity, and use of OCs and HRT were associated with shorter LTL, which has been linked to various chronic diseases. The accelerated shortening of telomeres may potentially contribute to the development of chronic diseases related to reproductive factors.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the National Natural Science Foundation of China (82003479, 82073660), Hubei Provincial Natural Science Foundation of China (2023AFB663), and the China Postdoctoral Science Foundation (2019M662646, 2020T130220). The authors have no competing interests to disclose.

TRIAL REGISTRATION NUMBER

N/A.

Targeting estrogen signaling and biosynthesis for aged skin repair

Non-healing skin wounds are disproportionally prevalent in older adults. Current treatments do not account for the particularities of aged skin and result in inadequate outcomes. Overall, healing chronic wounds in the elderly remains a major unmet clinical need. Estrogens play a critical role in reproduction but also have important actions in non-reproductive organs. Estrogen biosynthesis and signaling pathways are locally activated during physiological wound healing, processes that are inhibited in elderly estrogen-deprived skin. Estrogen deprivation has been shown to be a critical mediator of impaired wound healing in both postmenopausal women and aged men, and topical estrogen application reverses age-associated delayed wound healing in both elderly men and women. These data indicate that adequate estrogen biosynthesis and properly regulated estrogen signaling pathways are essential for normal wound healing and can be targeted to optimize tissue repair in the elderly. However, due to fundamental questions regarding how to safely restore estrogen signaling locally in skin wounds, there are currently no therapeutic strategies addressing estrogen deficiency in elderly chronic wounds. This review discusses established and recent literature in this area and proposes the hypothesis that estrogen plays a pleiotropic role in skin aging and that targeting estrogen signaling and biosynthesis could promote skin repair in older adults.

Could hypoxia rehabilitate the osteochondral diseased interface? Lessons from the interplay of hypoxia and purinergic signals elsewhere

The osteochondral unit comprises the articular cartilage (90%), subchondral bone (5%) and calcified cartilage (5%). All cells present at the osteochondral unit that is ultimately responsible for matrix production and osteochondral homeostasis, such as chondrocytes, osteoblasts, osteoclasts and osteocytes, can release adenine and/or uracil nucleotides to the local microenvironment. Nucleotides are released by these cells either constitutively or upon plasma membrane damage, mechanical stress or hypoxia conditions. Once in the extracellular space, endogenously released nucleotides can activate membrane-bound purinoceptors. Activation of these receptors is fine-tuning regulated by nucleotides' breakdown by enzymes of the ecto-nucleotidase cascade. Depending on the pathophysiological conditions, both the avascular cartilage and the subchondral bone subsist to significant changes in oxygen tension, which has a tremendous impact on tissue homeostasis. Cell stress due to hypoxic conditions directly influences the expression and activity of several purinergic signalling players, namely nucleotide release channels (e.g. Cx43), NTPDase enzymes and purinoceptors. This review gathers experimental evidence concerning the interplay between hypoxia and the purinergic signalling cascade contributing to osteochondral unit homeostasis. Reporting deviations to this relationship resulting from pathological alterations of articular joints may ultimately unravel novel therapeutic targets for osteochondral rehabilitation. At this point, one can only hypothesize how hypoxia mimetic conditions can be beneficial to the ex vivo expansion and differentiation of osteo- and chondro-progenitors for auto-transplantation and tissue regenerative purposes.

Intrinsic and extrinsic factors interact during development to influence telomere length in a long-lived reptile

The mechanisms connecting environmental conditions to plasticity in biological aging trajectories are fundamental to understanding individual variation in functional traits and life history. Recent findings suggest that telomere biology is especially dynamic during early life stages and has long-term consequences for subsequent reproduction and survival. However, our current understanding is mostly derived from studies investigating ecological and anthropogenic factors separately, leaving the effects of complex environmental interactions unresolved. American alligators (Alligator mississippiensis) are long-lived apex predators that rely on incubation temperature during a discrete period during development and endocrine cues to determine sex, making them especially vulnerable to current climatic variability and exposure to anthropogenic contaminants interfering with hormone function. Here, we combine field studies with a factorial design to understand how the developmental environment, along with intrinsic biological variation contribute to persistent telomere variation. We found that exposure to a common endocrine disrupting contaminant, DDE, affects telomere length, but that the directionality is highly dependent upon incubation temperature. Variation in hatchling growth, underlies a strong clutch effect. We also assess concentrations of a panel of glucocorticoid hormones and find that contaminant exposure elicits an increase in circulating glucocorticoids. Consistent with emerging evidence linking stress and aging trajectories, GC levels also appear to trend with shorter telomere length. Thus, we add support for a mechanistic link between contaminants and glucocorticoid signalling, which interacts with ecological aspects of the developmental environment to alter telomere dynamics.

Transgenic Mouse Models to Study the Development and Maintenance of the Adrenal Cortex

The cortex of the adrenal gland is organized into concentric zones that produce distinct steroid hormones essential for body homeostasis in mammals. Mechanisms leading to the development, zonation and maintenance of the adrenal cortex are complex and have been studied since the 1800s. However, the advent of genetic manipulation and transgenic mouse models over the past 30 years has revolutionized our understanding of these mechanisms. This review lists and details the distinct Cre recombinase mouse strains available to study the adrenal cortex, and the remarkable progress total and conditional knockout mouse models have enabled us to make in our understanding of the molecular mechanisms regulating the development and maintenance of the adrenal cortex.

Consequences of telomere dysfunction in fibroblasts, club and basal cells for lung fibrosis development

TRF1 is an essential component of the telomeric protective complex or shelterin. We previously showed that dysfunctional telomeres in alveolar type II (ATII) cells lead to interstitial lung fibrosis. Here, we study the lung pathologies upon telomere dysfunction in fibroblasts, club and basal cells. TRF1 deficiency in lung fibroblasts, club and basal cells induced telomeric damage, proliferative defects, cell cycle arrest and apoptosis. While Trf1 deletion in fibroblasts does not spontaneously lead to lung pathologies, upon bleomycin challenge exacerbates lung fibrosis. Unlike in females, Trf1 deletion in club and basal cells from male mice resulted in lung inflammation and airway remodeling. Here, we show that depletion of TRF1 in fibroblasts, Club and basal cells does not lead to interstitial lung fibrosis, underscoring ATII cells as the relevant cell type for the origin of interstitial fibrosis. Our findings contribute to a better understanding of proper telomere protection in lung tissue homeostasis.

Monitoring of telomere dynamics in peripheral blood leukocytes in relation to colorectal cancer patients’ outcomes

We investigated the possible associations between leukocyte telomere length, therapy outcomes, and clinicopathological features in patients with colorectal cancer. Additionally, telomerase reverse transcriptase (TERT) expression was evaluated. Telomere length was measured using singleplex qPCR in 478 consecutive leukocyte DNA samples from 198 patients. Blood was drawn at diagnosis prior to any therapy and then at 6-month intervals for 18 months. Following diagnosis, the telomeres gradually shortened during the course of the treatment regardless of the patient’s age. The most pronounced decrease was observed 12 months after the diagnosis (p < 0.0001). Based on tumor localization, the decrease in telomere length one year after the diagnosis followed different trajectories (p = 0.03). In patients treated with adjuvant therapy, telomere length correlated with the time elapsed after completion of therapy (p = 0.03). TERT expression did not correlate with the telomere length; however, it was higher in women than men (1.35-fold, 95% CI 1.11–1.65, p = 0.003) and in smokers than non-smokers (1.27-fold, 95% CI 1.01–1.61, p = 0.04). Leukocyte telomere length declines naturally during aging, but the accelerated shortening observed in our patients was age-independent. Telomere length manifestly reflected chemotherapy impact and could be linked to therapy toxicity.

Sex-specific associations of exposure to metal mixtures with telomere length change: Results from an 8-year longitudinal study

Studies on the relationships between exposure to metal mixtures and telomere length (TL) are limited, particularly longitudinal studies. Few studies are available on the potential sex-specific associations between metal exposures and TL change. We examined blood metal concentrations and TL at baseline (August 2012) and follow-up (June 2020) among 316 participants in a ferro-manganese refinery. The least absolute shrinkage and selection operator (LASSO) followed by the generalized linear model (GLM) was applied to evaluate the associations between multiple-metal exposures and TL change (TL in 2012 minus TL in 2020). Bayesian kernel machine regression (BKMR) was applied to cope with metal mixtures and evaluate their joint effects on TL change. Among men, three statistical methods consistently showed rubidium was negatively associated with TL change (β [95% CI] = -2.755 [-5.119, -0.391] in the GLM) and dominated the negative overall effects of 10 metal mixtures (magnesium, manganese, iron, cobalt, copper, zinc, selenium, rubidium, cadmium, and lead) on TL change (posterior inclusion probabilities = 0.816). Among women, the GLM (β [95% CI] = 4.463 [0.943, 7.983]) and LASSO (β = 4.289) showed rubidium was positively associated with TL change. Interestingly, no significant association was observed between exposure to metal mixtures and TL change in overall participants (P > 0.05). Furthermore, stratified analysis showed significant relationships between rubidium and TL change in men (β = -2.744), women (β = 3.624), and current smokers (β = -3.266) (both P interaction <0.05). In summary, our findings underlined the steady and negative association between rubidium and TL change among men with potential sex-dependent heterogeneities. Further experimental studies are required to expound the underlying mechanisms.

Molecular Mechanisms of Alveolar Epithelial Stem Cell Senescence and Senescence-Associated Differentiation Disorders in Pulmonary Fibrosis

Pulmonary senescence is accelerated by unresolved DNA damage response, underpinning susceptibility to pulmonary fibrosis. Recently it was reported that the SARS-Cov-2 viral infection induces acute pulmonary epithelial senescence followed by fibrosis, although the mechanism remains unclear. Here, we examine roles of alveolar epithelial stem cell senescence and senescence-associated differentiation disorders in pulmonary fibrosis, exploring the mechanisms mediating and preventing pulmonary fibrogenic crisis. Notably, the TGF-β signalling pathway mediates alveolar epithelial stem cell senescence by mechanisms involving suppression of the telomerase reverse transcriptase gene in pulmonary fibrosis. Alternatively, telomere uncapping caused by stress-induced telomeric shelterin protein TPP1 degradation mediates DNA damage response, pulmonary senescence and fibrosis. However, targeted intervention of cellular senescence disrupts pulmonary remodelling and fibrosis by clearing senescent cells using senolytics or preventing senescence using telomere dysfunction inhibitor (TELODIN). Studies indicate that the development of senescence-associated differentiation disorders is reprogrammable and reversible by inhibiting stem cell replicative senescence in pulmonary fibrosis, providing a framework for targeted intervention of the molecular mechanisms of alveolar stem cell senescence and pulmonary fibrosis. Abbreviations: DPS, developmental programmed senescence; IPF, idiopathic pulmonary fibrosis; OIS, oncogene-induced replicative senescence; SADD, senescence-associated differentiation disorder; SALI, senescence-associated low-grade inflammation; SIPS, stress-induced premature senescence; TERC, telomerase RNA component; TERT, telomerase reverse transcriptase; TIFs, telomere dysfunction-induced foci; TIS, therapy-induced senescence; VIS, virus-induced senescence.

Aging-Induced Impairment of Vascular Function: Mitochondrial Redox Contributions and Physiological/Clinical Implications

Significance: The vasculature responds to the respiratory needs of tissue by modulating luminal diameter through smooth muscle constriction or relaxation. Coronary perfusion, diastolic function, and coronary flow reserve are drastically reduced with aging. This loss of blood flow contributes to and exacerbates pathological processes such as angina pectoris, atherosclerosis, and coronary artery and microvascular disease. Recent Advances: Increased attention has recently been given to defining mechanisms behind aging-mediated loss of vascular function and development of therapeutic strategies to restore youthful vascular responsiveness. The ultimate goal aims at providing new avenues for symptom management, reversal of tissue damage, and preventing or delaying of aging-induced vascular damage and dysfunction in the first place. Critical Issues: Our major objective is to describe how aging-associated mitochondrial dysfunction contributes to endothelial and smooth muscle dysfunction via dysregulated reactive oxygen species production, the clinical impact of this phenomenon, and to discuss emerging therapeutic strategies. Pathological changes in regulation of mitochondrial oxidative and nitrosative balance (Section 1) and mitochondrial dynamics of fission/fusion (Section 2) have widespread effects on the mechanisms underlying the ability of the vasculature to relax, leading to hyperconstriction with aging. We will focus on flow-mediated dilation, endothelial hyperpolarizing factors (Sections 3 and 4), and adrenergic receptors (Section 5), as outlined in Figure 1. The clinical implications of these changes on major adverse cardiac events and mortality are described (Section 6). Future Directions: We discuss antioxidative therapeutic strategies currently in development to restore mitochondrial redox homeostasis and subsequently vascular function and evaluate their potential clinical impact (Section 7). Antioxid. Redox Signal. 35, 974-1015.

Idiopathic early ovarian aging: is there a relation with premenopausal accelerated biological aging in young women with diminished response to ART?

PURPOSE

To evaluate whether young women with idiopathic early ovarian aging, as defined by producing fewer oocytes than expected for a given age over multiple in vitro fertilization (IVF) cycles, have changes in telomere length and epigenetic age indicating accelerated biological aging (i.e., increased risk of morbidity and mortality).

METHODS

A prospective cohort study was conducted at two Danish public fertility clinics. A total of 55 young women (≤ 37 years) with at least two IVF cycles with ≤ 5 harvested oocytes despite sufficient stimulation with follicle-stimulating hormone (FSH) were included in the early ovarian aging group. As controls, 52 young women (≤ 37 years) with normal ovarian function, defined by at least eight harvested oocytes, were included. Relative telomere length (rTL) and epigenetic age acceleration (AgeAccel) were measured in white blood cells as markers of premenopausal accelerated biological aging.

RESULTS

rTL was comparable with a mean of 0.46 (± SD 0.12) in the early ovarian aging group and 0.47 (0.14) in the normal ovarian aging group. The AgeAccel of the early ovarian aging group was, insignificantly, 0.5 years older, but this difference disappeared when adjusting for chronological age. Sub-analysis using Anti-Müllerian hormone (AMH) as selection criterion for the two groups did not change the results.

CONCLUSION

We did not find any indications of accelerated aging in whole blood from young women with idiopathic early ovarian aging. Further investigations in a similar cohort of premenopausal women or other tissues are needed to fully elucidate the potential relationship between premenopausal accelerated biological aging and early ovarian aging.

The Sexually Dimorphic Adrenal Cortex: Implications for Adrenal Disease

Many adrenocortical diseases are more prevalent in women than in men, but the reasons underlying this sex bias are still unknown. Recent studies involving gonadectomy and sex hormone replacement experiments in mice have shed some light onto the molecular basis of sexual dimorphism in the adrenal cortex. Indeed, it has been shown that gonadal hormones influence many aspects of adrenal physiology, ranging from stem cell-dependent tissue turnover to steroidogenesis and X-zone dynamics. This article reviews current knowledge on adrenal cortex sexual dimorphism and the potential mechanisms underlying sex hormone influence of adrenal homeostasis. Both topics are expected to contribute to personalized and novel therapeutic approaches in the future.

Estrogen is required for maintaining the quality of cardiac stem cells

Compared to the age-matched men, the incidence of cardiovascular diseases is lower in premenopausal but higher in postmenopausal women, suggesting the cardio-protective role of estrogen in females. Although cardiac stem cells (CSCs) express estrogen receptors, yet the effects of estrogen on CSCs remain unclear. In this study, we investigated the potential role of estrogen in maintaining the quality of CSCs by in vivo and in vitro experiments. For the in vivo study, estrogen deficiency was induced by ovariectomy in 6-weeks-old C57BL/6 female mice, and then randomly given 17β-estradiol (E₂) replacements at a low dose (0.01 mg/60 days) and high dose (0.18 mg/60 days), or vehicle treatment. All mice were killed 2 months after treatments, and heart tissues were collected for ex vivo expansion of CSCs. Compared to age-matched healthy controls, estrogen deficiency slightly decreased the yield of CSCs with significantly lower telomerase activity and more DNA damage. Interestingly, E₂ replacements at low and high doses significantly increased the yield of CSCs and reversed the quality impairment of CSCs following estrogen deficiency. For the in vitro study, twice-passaged CSCs from the hearts of adult healthy female mice were cultured with the supplement of 0.01, 0.1, and 1 μM E₂ in the medium for 3 days. We found that E₂ supplement increased c-kit expression, increased proliferative activity, improved telomerase activity, and reduced DNA damage of CSCs in a dose-dependent manner. Our data suggested the potential role of estrogen in maintaining the quality of CSCs, providing new insight into the cardio-protective effects of estrogen.

c-KIT oncogene expression in PRKAR1A-mutant adrenal cortex

Protein kinase A (PKA) regulatory subunit type 1A (PRKAR1A) defects lead to primary pigmented nodular adrenocortical disease (PPNAD). The KIT protooncogene (c-KIT) is not known to be expressed in the normal adrenal cortex (AC). In this study, we investigated the expression of c-KIT and its ligand, stem cell factor (SCF), in PPNAD and other cortisol-producing tumors of the adrenal cortex. mRNA and protein expression, by qRT-PCR, immunohistochemistry (IHC) and immunoblotting (IB), respectively, were studied. We then tested c-KIT and SCF responses to PRKAR1A introduction and PKA stimulation in adrenocortical cell lines CAR47 and H295R, which were also treated with the KIT inhibitor, imatinib mesylate (IM). Mice xenografted with H295R cells were treated with IM. There was increased c-KIT mRNA expression in PPNAD; IHC showed KIT and SCF immunoreactivity within certain nodular areas in PPNAD. IB data was consistent with IHC and mRNA data. PRKAR1A-deficient CAR47 cells expressed c-KIT; this was enhanced by forskolin and lowered by PRKAR1A reintroduction. Knockdown of PKA's catalytic subunit (PRKACA) by siRNA reduced c-KIT levels. Treatment of the CAR47 cells with IM resulted in reduced cell viability, growth arrest, and apoptosis. Treatment with IM of mice xenografted with H295 cells inhibited further tumor growth. We conclude that c-KIT is expressed in PPNAD, an expression that appears to be dependent on PRKAR1A and/or PKA activity. In a human adrenocortical cell line and its xenografts in mice, c-KIT inhibition decreased growth, suggesting that c-KIT inhibitors may be a reasonable alternative therapy to be tested in PPNAD, when other treatments are not optimal.

Demographic and developmental patterns in telomere length across adolescence

Telomere length is often used in studies of adults as a biomarker of cellular aging and an indicator of stress exposure. However, we know little about how telomeres change over time, particularly over the course of the important developmental period of adolescence. We use data on telomere length collected at two points in time spanning adolescence (Years 9 and 15) from the Fragile Families and Child Wellbeing Study to examine longitudinal patterns (n = 1,654) in telomere length. We find a quantitatively small but significant average lengthening in telomere length across adolescence and little evidence of associations between telomere length and pubertal development.

Reproductive history and blood cell telomere length

Telomeres are repetitive nucleotide sequences that protect against chromosomal shortening. They are replenished by telomerase, an enzyme that may be activated by estrogen. Women have longer telomeres than men; this difference might be due to estrogen exposure. We hypothesized that reproductive histories reflecting greater estrogen exposure will be associated with longer blood cell telomeres. Among women in the Sister Study (n= 1,048), we examined telomere length in relation to self-reported data on reproductive history. The difference between age at menarche and last menstrual period was used to approximate the reproductive period. Relative telomere length (rTL) was measured using qPCR. After adjustment, rTL decreased with longer reproductive period (β= -0.019, 95% CI: -0.04, -0.00, p= 0.03). Premenopausal women had shorter rTL than postmenopausal women (β= -0.051, 95% CI: -0.12, 0.01, p= 0.13). Longer breastfeeding duration was associated with longer rTL (β= 0.027, 95% CI: 0.01, 0.05, p=0.01); increasing parity was associated with shorter rTL (β = -0.016, 95% CI: -0.03, 0.00, p=0.07). Duration of exogenous hormone use was not associated with rTL. Reproductive histories reflecting greater endogenous estrogen exposure were associated with shorter rTL. Our findings suggest that longer telomeres in women are unlikely to be explained by greater estrogen exposure.

BPA exposure is associated with non-monotonic alteration in ESR1 promoter methylation in peripheral blood of men and shorter relative telomere length in peripheral blood of women

The aim of this study was to evaluate the potential association of urinary Bisphenol A (BPA) levels with estrogen receptor alpha (ESR1) promoter % methylation and relative telomere length in a sample of 482 participants. Urinary BPA concentration was measured using organic phase extraction followed by high performance liquid chromatography mass spectroscopy. Peripheral blood ESR1 promoter % methylation and relative telomere length were measured using direct bisulfite sequencing and real-time polymerase chain reaction, respectively. The mean ± SD urinary BPA concentration adjusted for urinary creatinine was 2.90 ± 4.81 (μg/g creatinine) with a median of 1.86 μg/g creatinine (min-max: <LOD -69.85). There was a potentially non-monotonic relationship between adjusted urinary BPA concentrations and ESR1 promoter % methylation in men. As a matter of fact, for the lowest tertile of ESR1 promoter % methylation, the OR and 95% CI of the middle and highest tertiles of urinary adjusted BPA were 2.54 (1.01-6.39) and 1.64 (0.55-4.86) when compared to the lowest BPA tertile, respectively. After adjustment for potential confounders, similar results remained in men and appeared in the whole cohort. As for relative telomere length, there was a significant trend whereby higher adjusted urinary BPA concentrations were significantly associated with shorter relative telomere length in females. For instance, for the shortest relative telomere length tertile, the OR and 95% CI of the middle and highest tertiles of urinary adjusted BPA were 2.91 (1.38-6.16) and 3.19 (1.57-6.49) when compared to the lowest BPA tertile, respectively. This trend remained significant after adjustment for potential confounders.

Leukocyte telomere length in the Thoroughbred racehorse

Thoroughbred racehorses possess superior cardiorespiratory fitness levels and are at the pinnacle of athletic performance compared to other breeds of horses. Although equine athletes have undergone years of artificial selection for racing performance, musculoskeletal injuries and illnesses are common and concerns relating to animal welfare have been proposed. Leukocyte telomere length is indicative of biological age, and accelerated telomere shortening occurs with excess physical and psychological stress. This study was designed to explore the association between leukocyte telomere length, biological factors (age, sex and coat colour), training status, winnings and race history parameters. Blood was collected from 146 Thoroughbred racehorses from around Geelong, Victoria, Australia. DNA was extracted from leukocytes; telomere length was measured using qPCR and analysed in context with traits obtained from the Racing Australia website. Age was inversely correlated with telomere length (r = -0.194, P = 0.019). The oldest horses (≥11 years) in the highest age quartile possessed shorter telomeres compared to younger horses in the first, second and third quartiles (≤2, 3-5 and 6-10 years respectively; P < 0.05). No statistically significant associations were observed between telomere length and biological factors, training status, winnings or race history parameters in age-adjusted analyses. The study findings suggest that Thoroughbred horses may undergo age-related telomere shortening similar to other mixed breeds and humans. Despite concerns from some quarters regarding the welfare of racehorses, there was a lack of accelerated biological ageing observed in the present study, as indicated by leukocyte telomere length.

Interplay between estrogen-related receptors and steroidogenesis-controlling molecules in adrenals. In vivo and in vitro study

Estrogen-related receptors (ERRs) α, β and γ appear to be novel molecules implicated in estrogen signaling. We blocked and activated ERRs in mouse (C57BL/6) adrenals and adrenocortical cells (H295R) using pharmacological agents XCT 790 (ERRα antagonist) and DY131 (ERRβ/γ agonist), respectively. Mice were injected with XCT 790 or DY131 (5 μg/kg bw) while cells were exposed to XCT 790 or DY131 (0.5 μg/L). Irrespectively of the agent used, changes in adrenocortical cell morphology along with changes in lutropin, cholesterol levels and estrogen production were found. Diverse and complex ERRs regulation of multilevel-acting steroidogenic proteins (perilipin; PLIN, cytochrome P450 side-chain cleavage; P450scc, translocator protein; TSPO, steroidogenic acute regulatory protein; StAR, hormone sensitive lipase; HSL and HMG-CoA reductase; HMGCR) was revealed. Blockage of ERRα decreased P450scc, StAR and TSPO expressions. Activation of ERRβ/γ increased P450scc, StAR and HMGCR while decreased HSL expressions. PLIN expression increased either after XCT 790 or DY131 treatment. Additionally, treatment with both XCT 790 or DY131 decreased activity of Ras/Raf, Erk and Akt indicating their involvement in control of morphology and steroidogenic function of cortex cells. ERRs are important in maintaining morpho-function of cortex cells through action in specific, opposite, or common manner on steroidogenic molecules.

Relationships of sex hormone levels with leukocyte telomere length in Black, Hispanic, and Asian/Pacific Islander postmenopausal women

BACKGROUND

Sex hormones may play important roles in sex-specific biological aging. In the study, we specifically examined associations between circulating sex hormone concentrations and leukocyte telomere length (TL).

METHODS

A cross-sectional study was conducted among 1124 Black, 444 Hispanic, and 289 Asian/Pacific Islander women in the Women's Health Initiative Observational Cohort. Estradiol and testosterone concentrations were measured using electrochemiluminescence immunoassays; TL was measured using quantitative polymerase chain reaction.

RESULTS

Women in the study were aged 50-79 years. Estradiol concentrations were not significantly associated with TL in this sample. The associations between total and free testosterone and TL differed by race/ethnicity (P_interaction  = 0.03 and 0.05 for total and free testosterone, respectively). Total and free testosterone concentrations were not associated with TL in Black and Hispanic women, whereas in Asian/Pacific Islander women their concentrations were inversely associated with TL (P_trend  = 0.003 for both). These associations appeared robust in multiple subgroup analyses and multivariable models adjusted for potential confounding factors. In Asian/Pacific Islander women, a doubling of serum free and total testosterone concentrations was associated with a 202-bp shorter TL (95% confidence interval [CI] 51-353 bp) and 203-bp shorter TL (95% CI 50-355 bp), respectively.

CONCLUSIONS

Serum estradiol concentrations were not associated with leukocyte TL in this large sample of postmenopausal women. Total and free testosterone concentrations were inversely associated with TL in Asian/Pacific Islander women, but not in Black and Hispanic women, although future studies to replicate our observations are warranted particularly to address potential ethnicity-specific relationships.

Sjögren's syndrome X-chromosome dose effect: An epigenetic perspective

Sjögren's syndrome (SS) is a chronic autoimmune disease affecting exocrine glands leading to mouth and eyes dryness. The extent to which epigenetic DNA methylation changes are responsible for an X-chromosome dose effect has yet to be determined. Our objectives were to (i) describe how epigenetic DNA methylation changes could explain an X-chromosome dose effect in SS for women with normal 46,XX genotype and (ii) determine the relevant relationships to this dose effect, between X-linked genes, genes controlling X-chromosome inactivation (XCI) and genes encoding associated transcription factors, all of which are differentially expressed and/or differentially methylated in the salivary glands of patients with SS. We identified 58 upregulated X-chromosome genes, including 22 genes previously shown to escape XCI, based on the analysis of SS patient salivary gland GEO2R gene expression datasets. Moreover, we found XIST and its cis regulators RLIM, FTX, and CHIC1, and polycomb repressor genes of the PRC1/2 complexes to be upregulated. Many of the X-chromosome genes implicated in SS pathogenesis can be regulated by transcription factors which we found to be overexpressed and/or differentially methylated in patients with SS. Determination of the mechanisms underlying methylation-dependent gene expression and impaired XCI is needed to further elucidate the etiopathogenesis of SS.

Age at maturation has sex- and temperature-specific effects on telomere length in a fish

Telomeres are highly conserved nucleoprotein structures which protect genome integrity. The length of telomeres is influenced by both genetic and environmental factors, but relatively little is known about how different hereditary and environmental factors interact in determining telomere length. We manipulated growth rates and timing of maturation by exposing full-sib nine-spined sticklebacks (Pungitius pungitius) to two different temperature treatments and quantified the effects of temperature treatments, sex, timing of maturation, growth rate and family (genetic influences) on telomere length. We did not find the overall effect of temperature treatment on the relative telomere length. However, we found that variation in telomere length was related to timing of maturation in a sex- and temperature-dependent manner. Telomere length was negatively related to age at maturation in elevated temperature and early maturing males and females differed in telomere length. Variation in growth rate did not explain any variation in telomere length. The broad sense heritability (h ²) of telomere length was estimated at h ² = 0.31 - 0.47, suggesting predominance of environmental over genetic determinants of telomere length variability. This study provides the first evidence that age at maturation together with factors associated with it are influencing telomere length in an ectotherm. Future studies are encouraged to identify the extent to which these results can be replicated in other ectotherms.

The role of estrogen in cutaneous ageing and repair

Combined advances in modern medical practice and increased human longevity are driving an ever-expanding elderly population. Females are particularly at risk of age-associated pathology, spending more of their lives in a post-menopausal state. Menopause, denoted by a rapid decline in serum sex steroid levels, accelerates biological ageing across the body's tissues. Post-menopause physiological changes are particularly noticeable in the skin, which loses structural architecture and becomes prone to damage. The sex steroid most widely discussed as an intrinsic contributor to skin ageing and pathological healing is 17β-estradiol (or estrogen), although many others are involved. Estrogen deficiency is detrimental to many wound-healing processes, notably inflammation and re-granulation, while exogenous estrogen treatment widely reverses these effects. Over recent decades, many of the molecular and cellular correlates to estrogen's beneficial effect on normal skin homeostasis and wound healing have been reported. However, disparities still exist, particularly in the context of mechanistic studies investigating estrogen receptor signalling and its potential cellular effects. New molecular techniques, coupled with increased understanding of estrogen in skin biology, will provide further opportunities to develop estrogen receptor-targeted therapeutics.

Cell signaling pathways in the adrenal cortex: Links to stem/progenitor biology and neoplasia

The adrenal cortex is a dynamic tissue responsible for the synthesis of steroid hormones, including mineralocorticoids, glucocorticoids, and androgens in humans. Advances have been made in understanding the role of adrenocortical stem/progenitor cell populations in cortex homeostasis and self-renewal. Recently, large molecular profiling studies of adrenocortical carcinoma (ACC) have given insights into proteins and signaling pathways involved in normal tissue homeostasis that become dysregulated in cancer. These data provide an impetus to examine the cellular pathways implicated in adrenocortical disease and study connections, or lack thereof, between adrenal homeostasis and tumorigenesis, with a particular focus on stem and progenitor cell pathways. In this review, we discuss evidence for stem/progenitor cells in the adrenal cortex, proteins and signaling pathways that may regulate these cells, and the role these proteins play in pathologic and neoplastic conditions. In turn, we also examine common perturbations in adrenocortical tumors (ACT) and how these proteins and pathways may be involved in adrenal homeostasis.

Association between telomere length and CYP19 TTTA repetition polymorphism in healthy and breast cancer-diagnosed women

Introduction

Several studies have reported an increase in breast cancer (BC) risk when patients are carriers of the CYP19 TTA polymorphism with ≥10 repeats; moreover, it has been reported that telomere length is associated with a higher susceptibility of developing cancer.

Objective

The objective of this study was to understand the relationship between CYP19 TTTA repetition polymorphism and telomere length and its effects on serum estradiol, estrone and follicle-stimulating hormone (FSH).

Materials and methods

A total of 180 postmenopausal healthy and 70 BC-diagnosed women were included. Telomere length was determined through real-time quantitative polymerase chain reaction, and aromatase polymorphism was analyzed through DNA; both samples were obtained from circulating leukocytes. Serum estrone, estradiol and FSH were determined by enzyme-linked immunosorbent assay.

Results

Patients with a BC diagnosis showed >10 repetitions more frequently, compared with that of healthy women (50% vs 23%, χ² = 11.44, p = 0.0007). A significant difference in telomere length between healthy and BC women was observed (5,042.7 vs 2,256.7 pb, Z = 4.88, p < 0.001). CYP19 TTTA repeat polymorphism was associated with serum levels of estradiol and estrone in both groups, being higher in those with >10 repeats. Moreover, telomere length showed an inverse relationship with the number of repeats of the aromatase polymorphism in healthy women (R² = 0.04, r = −0.24); in contrast, BC patients did not display this relationship. In addition, telomere length presented an inverse relationship with serum levels of estradiol and estrone in BC patients (p = 0.02).

Conclusion

Telomere length is shorter in BC patients than in healthy patients. The CYP19 TTTA repeat polymorphism is associated with serum levels of estradiol and estrone in both healthy women and BC patients, being higher in those with polymorphism carriers >10 repeats. Telomere length has an inverse correlation with the number of repeats of the aromatase polymorphism in healthy women but not in BC women. Estradiol and estrone levels in BC women have an inverse relationship with telomere length.

Accelerated telomere shortening in peripheral blood lymphocytes after occupational polychlorinated biphenyls exposure

Polychlorinated biphenyls (PCBs) are organochlorine pollutants with a worldwide dissemination. We examined telomere length (TL) in peripheral blood cells of 207 individuals with a high body burden of PCBs due to occupational exposure in a transformer recycling company. Whereas TL in granulocytes was not affected, the age-adjusted TL in lymphocytes (∆TLLymph) of exposed individuals was significantly shorter than expected [-0.77 kb; 95 % confidence interval (CI) -0.9316; -0.6052; p = 0.0001]. PCB exposure did not affect lymphocyte numbers or T cell receptor excision circle (TREC) levels in T cells, suggesting that PCBs cause loss of telomeric DNA in T cells due to their metabolic activation and antigen-stimulated proliferation. In support of this hypothesis, blood plasma levels of PCB-exposed individuals inhibited expression of telomerase, the telomere elongating enzyme in vitro in antigen-specific T cell proliferation assays. 3-OH-CB28, a downstream metabolite of the lower chlorinated PCB-28 in PCB-exposed individuals (mean blood plasma concentration: 0.185 ± 0.68 ng/mL), inhibited telomerase gene expression within 48 h of incubation in lymphoproliferative assays starting at a concentration of 0.27-6.75 µg/mL and accelerated telomere shortening in long-term cell culture experiments. Accelerated telomere shortening due to PCB exposure may lead to limitations of cell renewal and clonal expansion of lymphocyte populations. As PCB-related immune dysfunctions have been linked to increased susceptibility to infectious diseases and increased risk of cancer, our data provide a possible explanation, for how PCBs could promote infections and cancer through limiting immune surveillance.

Sex biology contributions to vulnerability to Alzheimer's disease: A think tank convened by the Women's Alzheimer's Research Initiative

More than 5 million Americans are living with Alzheimer's disease (AD) today, and nearly two-thirds of Americans with AD are women. This sex difference may be due to the higher longevity women generally experience; however, increasing evidence suggests that longevity alone is not a sufficient explanation and there may be other factors at play. The Alzheimer's Association convened an expert think tank to focus on the state of the science and level of evidence around gender and biological sex differences for AD, including the knowledge gaps and areas of science that need to be more fully addressed. This article summarizes the think tank discussion, moving forward a research agenda and funding program to better understand the biological underpinnings of sex- and gender-related disparities of risk for AD.

Diurnal and stress-reactive dehydroepiandrosterone levels and telomere length in youth

The current investigation examined the association between the aging-related biomarkers dehydroepiandrosterone (DHEA) and telomere length (TL) in community-recruited African-American youth. The examination of DHEA included stress reactive, basal and diurnal sampling, in order to elucidate the underlying physiological process that may overlap with TL. One hundred and two participants completed the Trier Social Stressor Test for children (TSST-C). TL was obtained from all youth from buccal swabs on the same day as the TSST-C. Saliva samples from 83 participants were obtained over the course of two additional days to measure waking and diurnal levels of DHEA. DHEA diurnal slope was a robust predictor of TL (B=0.516, P<0.05), while other DHEA values were not significantly associated with TL. This study is one of the first studies to examine basal, diurnal and reactivity measurements of DHEA in youth. Furthermore, this is the first study, to our knowledge, to demonstrate a positive association between DHEA, a putative anti-aging hormone, and TL, an indicator of cellular aging.

Sexual dimorphism in cancer

The incidence of many types of cancer arising in organs with non-reproductive functions is significantly higher in male populations than in female populations, with associated differences in survival. Occupational and/or behavioural factors are well-known underlying determinants. However, cellular and molecular differences between the two sexes are also likely to be important. In this Opinion article, we focus on the complex interplay that sex hormones and sex chromosomes can have in intrinsic control of cancer-initiating cell populations, the tumour microenvironment and systemic determinants of cancer development, such as the immune system and metabolism. A better appreciation of these differences between the two sexes could be of substantial value for cancer prevention as well as treatment.

A novel method for banking stem cells from human exfoliated deciduous teeth: lentiviral TERT immortalization and phenotypical analysis

Background

Stem cells from human exfoliated deciduous teeth (SHED) have recently attracted attention as novel multipotential stem cell sources. However, their application is limited due to in vitro replicative senescence. Ectopic expression of telomerase reverse transcriptase (TERT) is a promising strategy for overcoming this replicative senescence. Nevertheless, its potential application and the phenotype as well as tumorigenicity have never been assessed in SHED.

Methods

TERT expression was stably restored in SHED (TERT-SHED) isolated from healthy children aged 6–8 years using lentiviral transduction with a puromycin selection marker. The expression of TERT was detected using reverse transcription polymerase chain reaction, Western blot and immunofluorescence. Surface markers of SHED were detected by flow cytometry. Enzyme-linked immunosorbent assay was used to assess senescence-associated β-galactosidase, while CCK-8 methods were used to examine the proliferation capacity of SHED and TERT-SHED at different passages. Moreover, multilineage differentiation, karyotype, colony formation in soft agar, and tumor formation in nude mice of SHED and TERT-SHED were also examined.

Results

Lentiviral transduction induced stable TERT expression even in SHED at the 40th passage. TERT-SHED showed robust proliferation capacity and low concentration of β-galactosidase. Although they had some different biomarkers than early passage SHED, TERT-SHED at late passage showed similar mutilineage differentiation as TERT at early passage. Moreover, TERT-SHED at late passage showed normal karyotype, no soft agar colony formation, and no tumor formation in nude mice.

Conclusions

TERT-immortalized SHED may be a promising resource for stem-cell therapy, although attention should be paid to the biological behavior of the cells.

Molecular mechanisms of ageing and related diseases

Human and other multicellular life species age, and ageing processes become dominant during the late phase of life. Recent studies challenge this dogma, suggesting that ageing does not occur in some animal species. In mammals, cell replicative senescence occurs as early as before birth (i.e. in embryos) under physiological conditions. How the molecular machinery operates and why ageing cells dominate under some circumstances are intriguing questions. Recent studies show that cell ageing involves extensive cellular remodelling, including telomere attrition, heterochromatin formation, endoplasmic reticulum stress, mitochondrial disorders and lysosome processing organelles and chromatins. This article provides an update on the molecular mechanisms underlying the ageing of various cell types, the newly described developmental and programmed replicative senescence and the critical roles of cellular organelles and effectors in Parkinson's disease, diabetes, hypertension and dyskeratosis congenita.

Current aging research in China

The mini-review stemmed from a recent meeting on national aging research strategies in China discusses the components and challenges of aging research in China. Highlighted are the major efforts of a number of research teams, funding situations and outstanding examples of recent major research achievements. Finally, authors discuss potential targets and strategies of aging research in China.

Stem cells and aberrant signaling of molecular systems in skin aging

The skin is the body's largest organ and it is able to self-repair throughout an individual's life. With advanced age, skin is prone to degenerate in response to damage. Although cosmetic surgery has been widely adopted to rejuvinate skin, we are far from a clear understanding of the mechanisms responsible for skin aging. Recently, adult skin-resident stem/progenitor cells, growth arrest, senescence or apoptotic death and dysfunction caused by alterations in key signaling genes, such as Ras/Raf/MEK/ERK, PI3K/Akt-kinases, Wnt, p21 and p53, have been shown to play a vital role in skin regeneration. Simultaneously, enhanced telomere attrition, hormone exhaustion, oxidative stress, genetic events and ultraviolet radiation exposure that result in severe DNA damage, genomic instability and epigenetic mutations also contribute to skin aging. Therefore, cell replacement and targeting of the molecular systems found in skin hold great promise for controlling or even curing skin aging.

Long-chain polyunsaturated fatty acids may mutually benefit both obesity and osteoporosis

The overconsumption of n-6 polyunsaturated fatty acids (PUFA), resulting in a high ratio of n-6 to n-3 PUFA, may contribute to the increased pathogenesis of obesity and osteoporosis by promoting low-grade chronic inflammation (LGCI). As evidence suggests, both obesity and osteoporosis are linked on a cellular and systemic basis. This review will analyze if a relationship exists between LGCI, fat, bone, and n-3 PUFA. During the life cycle, inflammation increases, fat mass accumulates, and bone mass declines, thus suggesting that a connection exists. This review will begin by examining how the current American diet and dietary guidelines may fall short of providing an anti-inflammatory dose of the n-3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It will then define LGCI and outline the evidence for a relationship between fat and bone. Inflammation as it pertains to obesity and osteoporosis and how EPA and DHA can alleviate the associated inflammation will be discussed, followed by some preliminary evidence to show how mesenchymal stem cell (MSC) lineage commitment may be altered by inflammation to favor adipogenesis. Our hypothesis is that n-3 PUFA positively influence obesity and osteoporosis by reducing LGCI, ultimately leading to a beneficial shift in MSC lineage commitment. This hypothesis essentially relates the need for more focused research in several areas such as determining age and lifestyle factors that promote the shift in MSC commitment and if current intakes of EPA and DHA are optimal for fat and bone.

Unexplained antepartum stillbirth: a consequence of placental aging?

Unexplained antepartum stillbirth is a major obstetric health problem. Data demonstrate a rapid rise in risk per 1000 continuing pregnancies as gestation advances beyond 40 weeks. We review the evidence that such stillbirths are a consequence of aging related changes in the late gestation placenta. We suggest that the relatively small number of continuing pregnancies after 40 completed weeks means that negative effects of genes that produce aging affect so few pregnancies that polymorphisms in genes that produce these effects are retained in the population. Aging related changes likely represent a consequence of the damaging effects of oxidative stress, increased by cigarette smoking counteracted by the mitigating effects of oxidative defence pathways. The aging related changes are likely downstream from nutrient sensing units such as mTOR and include effects on production of telomerase and consequent shortening of telomere length. The late gestation changes occur in the context of increasing fetal growth and nutrient supply demands that can produce the rapid development of a mismatch between placental supply and fetal need resulting in fetal demise. Premature aging may also play an important role in antepartum stillbirth occurring earlier in pregnancy, especially in the context of growth restriction.

Telomere length attrition, a marker of biological senescence, is inversely correlated with triglycerides and cholesterol in South Asian males with type 2 diabetes mellitus

South Asians have a higher risk of type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD) than white Caucasians, for a given BMI. Premature biological ageing, assessed by reduction in telomere length (TL), may be mediated by factors resulting from altered metabolic profiles associated with obesity. We hypothesise that ethnicity and metabolic status represent detrimental factors contributing to premature biological ageing. Therefore we assessed TL in two South Asian, age and BMI-matched cohorts [T2DM (n = 142) versus non-T2DM (n = 76)] to determine the effects of BMI, gender, lipid and CVD profile on biological ageing. Genomic DNA was obtained from the UKADS cohort; biochemical and anthropometric data was collected and TL was measured by quantitative real-time PCR. Our findings indicated a gender-specific effect with reduced TL in T2DM men compared with non-T2DM men (P = 0.006). Additionally, in T2DM men, TL was inversely correlated with triglycerides and total cholesterol (r = −0.419, P < 0.01; r = −0.443, P < 0.01). In summary, TL was reduced amongst South Asian T2DM men and correlated with triglycerides and total cholesterol. This study highlights enhanced biological ageing among South Asian, T2DM men, which appears to be tracked by changes in lipids and BMI, suggesting that raised lipids and BMI may directly contribute to premature ageing.

RPE cell senescence: a key contributor to age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in industrialized countries. Although much progress has been made recently in the management of later stages of the disease, no agents have yet been developed for the early stages or for prophylactic use. Furthermore, even the treatments for the later stages have limited effectiveness. The process of developing improved treatments for AMD is complicated by the existence of several theories concerning the cause of the disorder, each suggesting a different strategy for finding effective therapeutics. One of the potential contributors to AMD pathology is retinal pigment epithelial (RPE) cell senescence. The present paper hypothesizes that RPE senescence plays a central role in the etiology of AMD. This hypothesis is supported by the ability of RPE cell senescence to account for the signs, risk factors, and successful treatment modalities of the disorder. This hypothesis also points to several new prophylactic and treatment strategies for AMD.

Molecular regulation of telomerase activity in aging

The process of aging is mitigated by the maintenance and repair of chromosome ends (telomeres), resulting in extended lifespan. This review examines the molecular mechanisms underlying the actions and regulation of the enzyme telomerase reverse transcriptase (TERT), which functions as the primary mechanism of telomere maintenance and regulates cellular life expectancy. Underpinning increased cell proliferation, telomerase is also a key factor in facilitating cancer cell immortalization. The review focuses on aspects of hormonal regulations of telomerase, and the intracellular pathways that converge to regulate telomerase activity with an emphasis on molecular interactions at protein and gene levels. In addition, the basic structure and function of two key telomerase enzyme components-the catalytic subunit TERT and the template RNA (TERC) are discussed briefly.

Estrogen deficiency reversibly induces telomere shortening in mouse granulosa cells and ovarian aging in vivo

Estrogen is implicated as playing an important role in aging and tumorigenesis of estrogen responsive tissues; however the mechanisms underlying the mitogenic actions of estrogen are not fully understood. Here we report that estrogen deficiency in mice caused by targeted disruption of the aromatase gene results in a significant inhibition of telomerase maintenance of telomeres in mouse ovaries in a tissue-specific manner. The inhibition entails a significant shortening of telomeres and compromised proliferation in the follicular granulosa cell compartment of ovary. Gene expression analysis showed decreased levels of proto-oncogene c-Myc and the telomerase catalytic subunit, telomerase reverse transcriptase (TERT), in response to estrogen deficiency. Estrogen replacement therapy led to increases in TERT gene expression, telomerase activity, telomere length and ovarian tissue growth, thereby reinstating ovary development to normal in four weeks. Our data demonstrate for the first time that telomere maintenance is the primary mechanism mediating the mitogenic effect of estrogen on ovarian granulosa cell proliferation by upregulating the genes of c-Myc and TERT in vivo. Estrogen deficiency or over-activity may cause ovarian tissue aging or tumorigenesis, respectively, through estrogen regulation of telomere remodeling.