Premature aging in Werner's syndrome spares the central nervous system

Accelerated aging and aging process in the brain

One of the approaches to the research of the problem of aging is the study of genetic pathologies leading to accelerated aging, such as the Hutchinson-Gilford progeria syndrome, Werner syndrome, and Down syndrome. Probably, this approach can be used in an attempt to understand the neuronal mechanisms underlying normal and pathological brain aging. The analysis of the current state of scientific knowledge about these pathologies shows that in the Hutchinson-Gilford progeria and Werner syndrome, the rate of brain aging is significantly lower than the rate of whole body aging, whereas in Down syndrome, the brain ages faster than other organs due to amyloid-beta accumulation and chronic oxidative stress in the brain tissue. The main point of a previously proposed hypothesis is that the aging of higher animals and humans is associated with an increased level of reactive oxygen species in mitochondria with age, which activates apoptosis, thus reducing the number of functioning cells.

Nonfunctional mutant Wrn protein leads to neurological deficits, neuronal stress, microglial alteration, and immune imbalance in a mouse model of Werner syndrome

Werner syndrome (WS) is a premature aging disorder caused by mutations in a RecQ-family DNA helicase, WRN. Mice lacking part of the helicase domain of the WRN orthologue exhibit many phenotypic features of WS, including metabolic abnormalities and a shorter lifespan. Yet, little is known about the impact of WRN mutations on the central nervous system in both humans and mouse models of WS. In the current study, we have performed a longitudinal behavioral assessment on mice bearing a Wrn helicase deletion. Behavioral tests demonstrated a loss of motor activity and coordination, reduction in perception, increase in repetitive behavior, and deficits in both spatial and social novelty memories in Wrn mutant mice compared to age-matched wild type mice. These neurological deficits were associated with biochemical and histological changes in the brain of aged Wrn mutant mice. Microglia, resident immune cells that regulate neuronal plasticity and function in the brain, were hyper-ramified in multiple regions involved with the behavioral deficits of Wrn mutant mice. Furthermore, western analyses indicated that Wrn mutant mice exhibited an increase of oxidative stress markers in the prefrontal cortex. Supporting these findings, electron microscopy studies revealed increased cellular aging and oxidative stress features, among microglia and neurons respectively, in the prefrontal cortex of aged Wrn mutant mice. In addition, multiplex immunoassay of serum identified significant changes in the expression levels of several pro- and anti-inflammatory cytokines. Taken together, these findings indicate that microglial dysfunction and neuronal oxidative stress, associated with peripheral immune system alterations, might be important driving forces leading to abnormal neurological symptoms in WS thus suggesting potential therapeutic targets for interventions.

Impact of pulse pressure on cerebrovascular events leading to age-related cognitive decline

Aging is a modern concept: human life expectancy has more than doubled in less than 150 yr in Western countries. Longer life span, however, reveals age-related diseases, including cerebrovascular diseases. The vascular system is a prime target of aging: the "wear and tear" of large elastic arteries exposed to a lifelong pulsatile pressure causes arterial stiffening by fragmentation of elastin fibers and replacement by stiffer collagen. This arterial stiffening increases in return the amplitude of the pulse pressure (PP), its wave penetrating deeper into the microcirculation of low-resistance, high-flow organs such as the brain. Several studies have associated peripheral arterial stiffness responsible for the sustained increase in PP, with brain microvascular diseases such as cerebral small vessel disease, cortical gray matter thinning, white matter atrophy, and cognitive dysfunction in older individuals and prematurely in hypertensive and diabetic patients. The rarefaction of white matter is also associated with middle cerebral artery pulsatility that is strongly dependent on PP and artery stiffness. PP and brain damage are likely associated, but the sequence of mechanistic events has not been established. Elevated PP promotes endothelial dysfunction that may slowly develop in parallel with the accumulation of proinflammatory senescent cells and oxidative stress, generating cerebrovascular damage and remodeling, as well as brain structural changes. Here, we review data suggesting that age-related increased peripheral artery stiffness may promote the penetration of a high PP to cerebral microvessels, likely causing functional, structural, metabolic, and hemodynamic alterations that could ultimately promote neuronal dysfunction and cognitive decline.

Cognitive deficit in hippocampal-dependent tasks in Werner syndrome mouse model

Mammalian aging is often characterized by metabolic disturbances, cognitive declines and DNA repairs deficiency, but the underlying molecular mechanisms are still not well understood. Alterations in DNA repair can significantly exacerbate aging. Mammalian neuronal cells which accumulate unrepaired DNA damage over time could potentially lead to brain functions disorders. Focusing on the ATP-dependent RecQ-type DNA helicase, an enzyme involved in repair of double strand DNA, a mouse model of Werner syndrome (WS) had been proposed as a model of accelerated aging. Until now, no study has investigated the impact of this premature aging syndrome on learning and memory. Spatial memory and cognitive flexibility are particularly affected by the aging process in both men and rodents. Studies have shown that aged mice exhibited similar performance than young adult mice on non-hippocampus dependent memory whereas their performances were decreased in hippocampus-dependent tasks. In this study, we have submitted 3, 5 and 8 month-old WS mice to several behavioral paradigms to evaluate hippocampus-dependent (spatial object location, Morris water maze and fear conditioning) and non hippocampus-dependent (object recognition) memories. No effect on the locomotion activity and anxiety level has been observed in adult WS mice. Interestingly, the 8 month-old WS mice exhibit long-term memory impairment similar to aged mice, suggesting that adult WS mice do develop some aspects of cognitive aging.

Use of p38 MAPK Inhibitors for the Treatment of Werner Syndrome

Werner syndrome provides a convincing model for aspects of the normal ageing phenotype and may provide a suitable model for therapeutic interventions designed to combat the ageing process. Cultured primary fibroblast cells from Werner syndrome patients provide a powerful model system to study the link between replicative senescence in vitro and in vivo pathophysiology. Genome instability, together with an increased pro-oxidant state, and frequent replication fork stalling, all provide plausible triggers for intracellular stress in Werner syndrome cells, and implicates p38 MAPK signaling in their shortened replicative lifespan. A number of different p38 MAPK inhibitor chemotypes have been prepared rapidly and efficiently using microwave heating techniques for biological study in Werner syndrome cells, including SB203580, VX-745, RO3201195, UR-13756 and BIRB 796, and their selectivity and potency evaluated in this cellular context. Werner syndrome fibroblasts treated with a p38 MAPK inhibitor reveal an unexpected reversal of the accelerated ageing phenotype. Thus the study of p38 inhibition and its effect upon Werner pathophysiology is likely to provide new revelations into the biological mechanisms operating in cellular senescence and human ageing in the future.

DNA repair deficiency and neurological disease

The ability to respond to genotoxic stress is a prerequisite for the successful development of the nervous system. Mutations in various DNA repair factors can lead to human diseases that are characterized by pronounced neuropathology. In many of these syndromes the neurological component is among the most deleterious aspects of the disease. The nervous system poses a particular challenge in terms of clinical intervention, as the neuropathology associated with these diseases often arises during nervous system development and can be fully penetrant by childhood. Understanding how DNA repair deficiency affects the nervous system will provide a rational basis for therapies targeted at ameliorating the neurological problems in these syndromes.

The clinical characteristics of Werner syndrome: molecular and biochemical diagnosis

Werner syndrome (WS) is an adult onset segmental progeroid syndrome caused by mutations in the WRN gene. The WRN gene encodes a 180 kDa nuclear protein that possesses helicase and exonuclease activities. The absence of WRN protein leads to abnormalities in various DNA metabolic pathways such as DNA repair, replication and telomere maintenance. Individuals with WS generally develop normally until the third decade of life, when premature aging phenotypes and a series of age-related disorders begin to manifest. In Japan, where a founder effect has been described, the frequency of Werner heterozygotes appears to be as high as 1/180 in the general population. Due to the relatively non-specific nature of the symptoms and the lack of awareness of the condition, this disease may be under-diagnosed in other parts of the world. Genetic counseling of WS patients follows the path of other autosomal recessive disorders, with special attention needed for cancer surveillance in relatives. Molecular diagnosis of WS is made by nucleotide sequencing and, in some cases, protein analysis. It is also of potential interest to measure WRN activities in WS patients. More than 50 different disease-causing mutations in the WRN gene have been identified in WS patients from all over the world. All but one of these cases has mutations that result in the premature termination of the protein. Here we describe the clinical, molecular and biochemical characteristics of WS for use by medical professionals in a health care setting. Additional information is available through the International Registry of WS (http://www.wernersyndrome.org).

Cardiac stem cells and myocardial disease

Recent data indicate that the heart is a self-renewing organ and contains a pool of progenitor cells (PCs). According to the new paradigm, this resident population of multipotent undifferentiated cells gives rise to myocytes, endothelial cells, smooth muscle cells and fibroblasts. Understanding the function of cardiac PCs is critical for the implementation of these cells in the treatment of the diseased human heart. However, cardiac repair is an extremely complex phenomenon. Efficient myocardial regeneration requires restoration of segmental and focal areas of myocardial scarring, replacement of damaged coronary arteries, arterioles and capillaries, and substitution of hypertrophied poorly contracting myocytes with smaller better functioning parenchymal cells. To achieve these goals, the acquisition of a more profound knowledge of the biology of cardiac PCs cells and their fate following pathologic insults represents an essential need.

Transplantation and regeneration in the heart of the Mediterranean

The second half of the 20th century witnessed the birth of organ transplantation, and failing organs can now be replaced with healthy ones procured from living or cadaveric donors, allowing their recipient to start, or return to, an active life. Major milestones in the field were set in the eighties and nineties at the University of Pittsburgh Medical Center (UPMC), an institution that made it a mission to spread its expertise internationally. A successful partnership between UPMC and the Region of Sicily gave rise to the Mediterranean Institute for Transplantation and Highly Specialized Therapies (ISMETT), the only Italian facility entirely dedicated to transplantation of all solid organs and therapies for the treatment of end-stage organ failure. In its first seven years of activity, ISMETT has become a major referral center for patients from the entire Mediterranean Basin and the Middle East. Despite the fact that organ transplantation is the current gold standard for end-stage organ failure, the field is facing a worldwide emergency represented by the chronic shortage of organ donors. Research aimed at understanding the molecular networks involved in organ-specific ageing and their relationship with maintenance networks and organ failure should be actively encouraged and supported as it could ultimately allow to control organ performance and lifespan, increasing the number of organs available for transplant.

Atypical meningioma in Werner syndrome: a case report

INTRODUCTION

Werner Syndrome, or adult progeria, is a rare autosomal recessive disorder caused by a mutation in the Werner Syndrome Gene belonging to the family of RecQ helicase. Malignant mesenchymal tumours and atherosclerosis are typical causes of death. Intracranial meningiomas are frequently described in these patients.

CLINICAL PRESENTATION

We present the case of a 46-year-old man with Werner Syndrome and a convexity meningioma. The patient had a 2-year history of paresthesia and paresis in his right leg, which had worsened in recent months. He underwent surgery with Simpson grade II removal, with improvement of the slight paresis and no other neurological defects. The patient then underwent radiotherapy (60 Gy). Histological examination revealed an atypical meningioma. Cytogenetic analysis showed a hypodiploid clone with a complex karyotype characterized by monosomy 22 and deletion 1p. After 3 years' follow-up no relapses had occurred.

CONCLUSION

1p deletion correlates with meningioma progression and in this case correlates with histological examination. The chromosomal instability underlying Werner Syndrome could have fostered the complex karyotype.

Myocardial aging

This review questions the old paradigm that describes the heart as a post-mitotic organ and introduces the notion of the heart as a self-renewing organ regulated by a compartment of multipotent cardiac stem cells (CSCs) capable of regenerating myocytes and coronary vessels throughout life. Because of this dramatic change in cardiac biology, the objective is to provide an alternative perspective of the aging process of the heart and stimulate research in an area that pertains to all of us without exception. The recent explosion of the field of stem cell biology, with the recognition that the possibility exists for extrinsic and intrinsic regeneration of myocytes and coronary vessels, necessitates reevaluation of cardiac homeostasis and myocardial aging. From birth to senescence, the mammalian heart is composed of non-dividing and dividing cells. Loss of telomeric DNA is minimal in fetal and neonatal myocardium but rather significant in the senescent heart. Aging affects the growth and differentiation potential of CSCs interfering not only with their ability to sustain physiological cell turnover but also with their capacity to adapt to increases in pressure and volume loads. The recognition of factors enhancing the activation of the CSC pool, their mobilization, and translocation, however, suggests that the detrimental effects of aging on the heart might be prevented or reversed by local stimulation of CSCs or the intramyocardial delivery of CSCs following their expansion and rejuvenation in vitro. CSC therapy may become, perhaps, a novel strategy for the devastating problem of heart failure in the old population.

Myocardial aging and senescence: where have the stem cells gone?

Heart failure remains a leading cause of hospital admissions and mortality in the elderly, and current interventional approaches often fail to treat the underlying cause of pathogenesis. Preservation of structure and function in the aging myocardium is most likely to be successful via ongoing cellular repair and replacement, as well as survival of existing cardiomyocytes that generate contractile force. Research has led to a paradigm shift driven by application of stem cells to generate cardiovascular cell lineages. Early controversial findings of pluripotent precursors adopting cardiac phenotypes are now widely accepted, and current debate centers upon the efficiency of progenitor cell incorporation into the myocardium. Much work remains to be done in determining the relevant progenitor cell population and optimizing conditions for efficient differentiation and integration. Significant implications exist for treatment of pathologically damaged or aging myocardium since future interventional approaches will capitalize upon the use of cardiac stem cells as therapeutic reagents.

Senescence and death of primitive cells and myocytes lead to premature cardiac aging and heart failure

Chronological myocardial aging is viewed as the inevitable effect of time on the functional reserve of the heart. Cardiac failure in elderly patients is commonly interpreted as an idiopathic or secondary myopathy superimposed on the old heart independently from the aging process. Thus, aged diseased hearts were studied to determine whether cell regeneration was disproportionate to the accumulation of old dying cells, leading to cardiac decompensation. Endomyocardial biopsies from 19 old patients with a dilated myopathy were compared with specimens from 7 individuals of similar age and normal ventricular function. Ten patients with idiopathic dilated cardiomyopathy were also analyzed to detect differences with aged diseased hearts. Senescent cells were identified by the expression of the cell cycle inhibitor p16INK4a and cell death by hairpin 1 and 2. Replication of primitive cells and myocytes was assessed by MCM5 labeling, myocyte mitotic index, and telomerase function. Aged diseased hearts had moderate hypertrophy and dilation, accumulation of p16INK4a positive primitive cells and myocytes, and no structural damage. Cell death markedly increased and occurred only in cells expressing p16INK4a that had significant telomeric shortening. Cell multiplication, mitotic index and telomerase increased but did not compensate for cell death or prevented telomeric shortening. Idiopathic dilated cardiomyopathy had severe hypertrophy and dilation, tissue injury, and minimal level of p16INK4a labeling. In conclusion, telomere erosion, cellular senescence, and death characterize aged diseased hearts and the development of cardiac failure in humans.

Lack of amyloid plaque formation in the central nervous system of a patient with Werner syndrome

Werner syndrome (WS) is an autosomal recessive disorder associated with accelerated aging. It is well documented on systemic aging but it is unclear whether the brain with WS shows accelerated aging. A 55-year-old patient with WS was studied and it was found that a deletion mutation of exon 26 of the WRN gene was not associated with CNS pathology, such as amyloid plaques or NFT. Furthermore, additional genetic analysis showed an apolipoprotein E genotype of epsilon3/epsilon3 that did not play either an accelerating or inhibitory action on' amyloid deposition. Therefore, based on the genetic and neuropathological analysis, it was observed that the WS-associated aging seen in many organs did not extend to the CNS.

Werner Syndrome

Werner syndrome is a premature aging disease caused by the mutation in the WRN gene. The cloning and characterization of the WRN gene and its product allows investigators to study the disease and the human aging process at molecular level. This review summarizes the recent progresses on various aspects of the WRN research including functional analysis of the protein, interactive cloning, complexes formation, mouse models, and SNPs (single nucleotide polymorphisms). These in depth investigations have greatly advanced our understanding of the disease and elucidated future research direction for Werner syndrome and the human aging process.

The Werner syndrome protein: an update

Progeria and progeroid syndromes are characterized by the earlier onset of complex senescent phenotypes. WRN was originally identified as a gene responsible for Werner syndrome (WS; "Progeria of Adults"). The WRN gene product has RecQ-type helicase domains in the central region of the protein. Subsequent studies also revealed that the WRN protein displays exonuclease activity and acts as a transcriptional activation factor. These biochemical studies, combined with cell biological studies, suggested that this protein is likely to be involved in the response to DNA damage during replication, as well as recombination and transcription processes. However, the precise molecular mechanisms by which mutations in WRN cause the WS phenotype remain unknown. Recent progress in the understanding of the WRN protein and its implication in the normal aging process are discussed.

Myopia, intelligence, and the expanding human neocortex: behavioral influences and evolutionary implications

The first two parts of this monograph document that areas of the human neocortex heavily used to cope with a complex, language-driven society have been expanding rapidly and suggest strongly that this is linked with the huge upsurge that's occurred in myopia, and with the large gradual 20th-century increase in measured intelligence. Part III proposes mechanisms capable of supporting such rapid changes, without violating the basic precepts of Darwin's thinking. Part IV discusses the social and evolutionary ramifications of our apparent proclivity for rapid, progressive, adaptive neocortical change, and suggests areas for productive research.