Replicative cellular senescence is a phenomenon of irreversible growth arrest triggered by the accumulation of a discrete number of cell divisions. The vast majority of normal cell types from all vertebrate species display this response. It is becoming increasingly evident that what has classically been described as cellular senescence is a collection of interrelated states that can be triggered by distinct intrinsic and extrinsic stimuli. We have found that when normal human diploid fibroblasts are subcultured into replicative exhaustion, three ? essentially independent processes can take place, each of which is sufficient to establish a senescent growth arrest state. The first pathway is initiated by telomere shortening. The second pathway is initiated by an unknown, spontaneous and stochastic process that leads to the upregulation of the cyclin-dependent kinase inhibitor p16 n K4A.The third pathway is initiated by mitochondrial damage leading to the production of sufficient oxidative stress to activate the p53 tumor suppressor protein. We have developed an in vitro cell based model system that allows us to selectively track and study senescent cells in unperturbed cultures, and to prepare homogeneous populations of cells that have activated a single senescence pathway.
Aim 1 will examine the role of p53 and upstream effectors in telomere-initiated senescence. Posttranslational modifications of p53 and the activation status of signaling pathways upstream of p53 will be studied.
Aim 2 will seek to discover what causes the spontaneous, age-dependent upregulation of pl6. Effectors implicated in regulating the p 16 gene will be examined, pharmacological methods will be used to probe cytoplasmic kinase cascades, and the physiological state elicited by the p16 pathway will be explored by microarray expression profiling.
Aim 3 will investigate the causes and consequences of spontaneous upregulation of reactive oxygen species (ROS). The functional relationships between the ROS, p 16 and telomere pathways will be examined, and the effect of the IGF signaling pathway implicated in organismal aging on the pathways of cellular senescence will be studied. In all cases, reverse-genetic interventions utilizing dominant and constitutively active proteins as well as siRNA-mediated ablation will be used to probe the transmission of the senescence signals. Interventions will be sought to elicit senescence responses in naive cells, to prevent a natural senescence response caused by replicative exhaustion, and to reverse an established senescent state. Studies described in this proposal will give us a better understanding of cellular senescence processes, and will begin to shed light on the roles of cellular senescence in organismal aging. ? ?

National Institute of Health (NIH)
National Institute on Aging (NIA)
Research Project (R01)
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Special Emphasis Panel (ZRG1-DEV-2 (03))
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Sierra, Felipe
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Brown University
Schools of Medicine
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Waaijer, Mariƫtte E C; Gunn, David A; van Heemst, Diana et al. (2018) Do senescence markers correlate in vitro and in situ within individual human donors? Aging (Albany NY) 10:278-289
Ito, Takahiro; Teo, Yee Voan; Evans, Shane A et al. (2018) Regulation of Cellular Senescence by Polycomb Chromatin Modifiers through Distinct DNA Damage- and Histone Methylation-Dependent Pathways. Cell Rep 22:3480-3492
Tatar, Marc; Sedivy, John M (2016) Mitochondria: Masters of Epigenetics. Cell 165:1052-1054
Hofmann, Jeffrey W; Zhao, Xiaoai; De Cecco, Marco et al. (2015) Reduced expression of MYC increases longevity and enhances healthspan. Cell 160:477-88
Waaijer, Mariƫtte E C; Parish, William E; Strongitharm, Barbara H et al. (2012) The number of p16INK4a positive cells in human skin reflects biological age. Aging Cell 11:722-5
Alves, Hugo; Munoz-Najar, Ursula; De Wit, Jan et al. (2010) A link between the accumulation of DNA damage and loss of multi-potency of human mesenchymal stromal cells. J Cell Mol Med 14:2729-38
Liu, Yen-Chun; Li, Feng; Handler, Jesse et al. (2008) Global regulation of nucleotide biosynthetic genes by c-Myc. PLoS One 3:e2722
Sedivy, John M; Banumathy, Gowrishankar; Adams, Peter D (2008) Aging by epigenetics--a consequence of chromatin damage? Exp Cell Res 314:1909-17
Jeyapalan, Jessie C; Sedivy, John M (2008) Cellular senescence and organismal aging. Mech Ageing Dev 129:467-74
Schorl, Christoph; Sedivy, John M (2007) Analysis of cell cycle phases and progression in cultured mammalian cells. Methods 41:143-50

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