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Stolzing A, Hescheler J, Sethe S. Fusion and Regenerative Therapies: Is Immortality Really Recessive? Rejuvenation Res 2007; 10:571-86. [DOI: 10.1089/rej.2007.0570] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
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2
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Abstract
Life expectancy in the United States and other developed nations has increased remarkably over the past century, and continues to increase. However, lifespan has remained relatively unchanged over this period. As life expectancy approaches maximum human lifespan, further increase in life expectancy would only be possible if lifespan could also be increased. Although little is known about the aging process, increasing lifespan and delaying aging are the research challenges of the new century, and have caused intense debate and research activities among biogerontologists. Many theories have been proposed to explain the aging process. However, damage to deoxyribonucleic acid (DNA) is the centerpiece of most of these. Recently telomere shortening has been described to be associated with DNA damage. Located at the ends of eukaryotic chromosomes and synthesized by telomerase, telomeres maintain the length of chromosomes. The loss of telomeres can lead to DNA damage. The association between cellular senescence and telomere shortening in vitro is well established. In the laboratory, telomerase-negative differentiated somatic cells maintain a youthful state, instead of aging, when transfected with vectors encoding telomerase. Many human cancer cells demonstrate high telomerase activity. Evidence is also accumulating that telomere shortening is associated with cellular senescence in vivo. What causes changes in expression of telomerase in different cell types and premature aging syndromes? Does the key to "youthfulness" lie in our ability to control the expression of telomerase? We have reviewed the contemporary literature to find answers to these questions and explore the association between aging, telomeres, and telomerase.
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Affiliation(s)
- A Ahmed
- Division of Gerontology and Geriatric Medicine, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, USA
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3
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Abstract
The aim of this work was to raise allotype specific monoclonal antibodies to human CD45, with the long-term objective of producing a reagent which could be used to prolong graft survival in renal transplantation through removal of passenger leukocytes from the graft. At present there are no anti-CD45 monoclonal antibodies able to distinguish between host and donor leukocytes. An in vitro immunisation technique has been developed through which donated human leukocytes are sensitised to CD45 prior to fusion with a myeloma cell line. IgM was produced by all the anti-CD45-positive clones. Flow cytometric analysis using these antibodies showed their ability to differentiate between blood from individual donors, indicating the existence of allotypic forms of human CD45, in conformity with the findings in rats and pigs. Therefore, a reagent which could be used in renal transplantation is a technical possibility.
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Affiliation(s)
- G S Dean
- Bloomsbury Rheumatology Unit, University College London Medical School, UK
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4
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Abstract
Evidence that control of cellular proliferative potential may be linked to telomere length, along with data indicating that other factors may also be involved, will be reviewed. According to the telomere hypothesis of senescence, the sequential loss of telomeric repeat DNA that occurs during the replication of normal somatic cells eventually dictates the onset of the permanently nonreplicative state known as senescence. Many immortalized cells express telomerase, a ribonucleoprotein enzyme that replaces the telomeric DNA that would otherwise be lost due to replication. However, some immortalized human cells may avoid telomeric shortening without using telomerase. The mechanism involved is currently unknown, but other eukaryotes are able to replace telomeric DNA through (1) recombination and copy switching or (2) retrotransposition. Human fibroblasts that lose p53 function proliferate a limited number of times beyond the population-doubling level at which their normal counterparts become senescent. Lack of functional retinoblastoma (Rb) protein (or equivalent events, such as loss of p16INK4 function, resulting in abrogation of Rb regulatory activity) also permits a temporary extension of proliferative potential. The p53 and pRb effects are additive, indicating that they exert their control on proliferative potential separately. The temporary life span extension associated with loss of p53 and/or Rb pathway function is accompanied by continued telomere shortening. The proliferation arrest that eventually ensues in p53-minus cells or in p53-minus/Rb-minus cells may be regarded as terminal proliferation arrest states serving as a backup to senescence. p53-minus/Rb-minus cells cannot proliferate further unless they acquire the ability to prevent telomeric shortening. Somatic cell hybridization and microcell-mediated chromosome transfer experiments indicate that immortalization involves the loss of function of other, as yet unidentified, genes; some of these may normally repress telomerase expression in somatic cells.
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Affiliation(s)
- R R Reddel
- Children's Medical Research Institute, Westmead, Sydney, NSW, Australia.
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5
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Abstract
Ovarian ageing is not only of major importance in its own right but is also of interest for its relationship with the general biology of senescence. A key feature of ageing is the distinction in higher animals between the immortality of the germ-line and the mortality of somatic cells and tissues. The ovary contains the female germ cells, and it is through these cells that the female contribution to germ-line immortality is effected. It is abundantly clear that individual oocytes can and do age and that the ageing of the ovary plays a major role in initiating or accelerating a series of other senescent changes. To understand how ovarian ageing fits within the general biology of senescence, it is necessary to explain why ageing occurs at all, to examine the likely mechanisms of general ageing, and to ask whether there is anything special about ovarian ageing and its relationship with the human menopause. Research on ovarian ageing interacts with the our emerging understanding of the general biology of senescence at many levels, ranging from the evolution of the human life history to the biochemical and cellular mechanisms of ageing and longevity.
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Affiliation(s)
- T B Kirkwood
- Department of Geriatric Medicine, University of Manchester, UK.
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Ribault D, Habib M, Abdel-Majid K, Barbara A, Mitrovic D. Age-related decrease in the responsiveness of rat articular chondrocytes to EGF is associated with diminished number and affinity for the ligand of cell surface binding sites. Mech Ageing Dev 1998; 100:25-40. [PMID: 9509392 DOI: 10.1016/s0047-6374(97)00115-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The effect of age on the responsiveness of articular chondrocytes (AC) to epidermal growth factor (EGF) was examined. Cells were isolated by digesting cartilage fragments from the humeral and femoral heads of 21-day old, 8- and 14-month old rats with collagenase. The cells were cultured under standard conditions, as monolayers. DNA synthesis was measured by [3H]thymidine incorporation and cell proliferation by the DNA content of subconfluent cultures. [125I]EGF binding and the amounts of EGF and EGF-receptor mRNAs were determined using confluent cells. DNA synthesis was decreased with age of animals. EGF stimulated DNA synthesis in cultures in 1- and 8-month old rats at low serum concentrations (< 5%), and in cultures in 14-month old animals at high serum concentrations. It also increased 5-day DNA content of cultures compared to serum-treated controls but this effect was weak in cultures in 14-month old rats. The number of high affinity binding sites for [125I]EGF decreased from 37,800 in the 1-month old to 1950 in the 14-month old rat AC. The apparent dissociation constant (Kd) also decreased with age: 0.18 nmol/l in the 1-month old; 0.12 nmol/l in the 8-month old; and 0.07 nmol/l in the 14-month old cells. AC in older rats contained more EGF mRNA and less EGF-receptor mRNA. Incubation of the cells with EGF resulted in down regulation of the EGF- and upregulation of EGF-receptor mRNA expressions. These findings show the age-related quantitative and qualitative alterations in EGF and EGF-receptor which may account, at least in part, for the diminished responsiveness of senescent AC to EGF.
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Abstract
The origins of human ageing are to be found in the origins and evolution of senescence as a general feature in the life histories of higher animals. Ageing is an intriguing problem in evolutionary biology because a trait that limits the duration of life, including the fertile period, has a negative impact on Darwinian fitness. Current theory suggests that senescence occurs because the force of natural selection declines with age and because longevity is only acquired at some metabolic cost. In effect, organisms may trade late survival for enhanced reproductive investments in earlier life. The comparative study of ageing supports the general evolutionary theory and reveals that human senescence, while broadly similar to senescence in other mammalian species, has distinct features, such as menopause, that may derive from the interplay of biological and social evolution.
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Affiliation(s)
- T B Kirkwood
- Department of Geriatric Medicine, University of Manchester, UK
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8
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Kirkwood TB. What is the relationship between osteoarthritis and ageing? BAILLIERE'S CLINICAL RHEUMATOLOGY 1997; 11:683-94. [PMID: 9429731 DOI: 10.1016/s0950-3579(97)80004-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The relationship between osteoarthritis and ageing raises important questions about what exactly defines 'normal' ageing and whether the pathogenesis of osteoarthritis shares common pathways with other age-associated dysfunctions, or whether osteoarthritis is a time-dependent disorder distinct from normal ageing with a separate causative mechanism at work. Theories of ageing now emphasize the stochastic nature of the ageing process, that is the role played by accumulation of essentially random cell and tissue damage, such as somatic mutations, oxidative damage and the formation of aberrant proteins. The role of genetic factors in determining longevity and predisposition to age-associated diseases is probably in programming the efficiency of somatic maintenance functions and in influencing the development of a durable soma. Gene-environment interactions, for example through lifestyle, can also be important. Many of the risk factors and mechanisms that are thought to contribute to osteoarthritis can be accommodated within this framework.
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Affiliation(s)
- T B Kirkwood
- Department of Geriatric Medicine, University of Manchester, UK
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9
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Abstract
Normal cells have limited proliferative potential in culture, a fact that has been the basis of their use as a model for replicative senescence for many years. Recent molecular analyses have identified numerous changes in gene expression that occur as cells become senescent, and the results indicate that multiple levels of control contribute to the irreversible growth arrest. These include repression of growth stimulatory genes, overexpression of growth inhibitory genes, and interference with downstream pathways. Studies with cell types other than fibroblasts will better define the role of cell senescence in the aging process and in tumorigenesis.
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Affiliation(s)
- J R Smith
- Roy M. and Phyllis Gough Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030-3498, USA
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10
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Biological Aging and Longevity: Underlying Mechanisms and Potential Intervention Strategies. J Aging Phys Act 1994. [DOI: 10.1123/japa.2.4.304] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Aging is characterized by numerous physical, physiological, biochemical, and molecular changes. The rates at which aging processes occur are highly variable among individuals and are thought to be governed by both environmental and genetic factors. Lifestyle factors such as exercise, dietary, and smoking habits have been demonstrated to alter many of the changes usually associated with human aging. However, at present caloric restriction is the only experimental paradigm that has consistently been demonstrated in animal models to extend not only physiological vigor but also life span. The positive effects of exercise on physiological fitness and the reduction in the risks of certain diseases have been well documented. However, its effects on life span are not as clear. This article explores some of the basic mechanisms thought to be involved causally in the processes of aging, and outlines current and potential interventive strategies to retard or ameliorate the rates of decline in physiological function with advancing age.
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Ryan PA, Maher VM, McCormick JJ. Failure of infinite life span human cells from different immortality complementation groups to yield finite life span hybrids. J Cell Physiol 1994; 159:151-60. [PMID: 8138583 DOI: 10.1002/jcp.1041590119] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The observation that fusion of infinite life span cells with finite life span cells produces hybrid cells with finite life spans led to the conclusion that an infinite life span in culture is a recessive trait resulting from loss of the function of a gene or genes that contribute to an active program for cellular senescence. Furthermore, finding that certain pairs of infinite life span cells, when fused to one another, can complement each other to yield finite life span hybrids allowed 30 infinite life span cell lines to be assigned to four immortality complementation groups (Pereira-Smith and Smith, 1988, Proc. Natl. Acad. Sci. U.S.A., 85:6042). In the present study, we fused a chromosomally stable, near diploid, morphologically normal, infinite life span cell strain, designated MSU-1.1, with its normal, finite life span, precursor cell strain and obtained finite life span hybrids, as expected if infinite life span in culture is a recessive trait. However, 14 of the 14 hybrids from our fusions of MSU-1.1 cells with representative cell lines from each of the four immortality complementation groups, and 38 of the 39 hybrids from our fusions of infinite life span cells that have been reported to complement each other, failed to exhibit finite life spans. This result suggests that infinite life span cells cannot complement each other to yield finite life span hybrids. In examining this unexpected result, we obtained evidence that long-term dual drug selection can be deleterious to hybrid cells even though they carry resistance markers for both drugs, indicating that the cell death of such hybrids observed in other studies may have resulted from the cytotoxic effect of long-term drug selection, rather than from senescence.
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Affiliation(s)
- P A Ryan
- Department of Microbiology, Michigan State University, East Lansing 48824-1316
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Goletz TJ, Hensler PJ, Ning Y, Adami GR, Pereira-Smith OM. Evidence for a genetic basis for the model system of cellular senescence. J Am Geriatr Soc 1993; 41:1255-8. [PMID: 8227901 DOI: 10.1111/j.1532-5415.1993.tb07311.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- T J Goletz
- Roy M. and Phyllis Gough Huffington Center on Aging, Baylor College of Medicine, Houston, TX 77030
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13
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Wadhwa R, Kaul S, Sugimoto Y, Mitsui Y. Induction of cellular senescence by transfection of cytosolic mortalin cDNA in NIH 3T3 cells. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)41515-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Wadhwa R, Kaul S, Ikawa Y, Sugimoto Y. Identification of a novel member of mouse hsp70 family. Its association with cellular mortal phenotype. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(18)53295-6] [Citation(s) in RCA: 146] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Kirkwood TB, Franceschi C. Is aging as complex as it would appear? New perspectives in aging research. Ann N Y Acad Sci 1992; 663:412-7. [PMID: 1482071 DOI: 10.1111/j.1749-6632.1992.tb38685.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- T B Kirkwood
- National Institute for Medical Research, Mill Hill, UK
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