Project description:Telomere shortening in populations of human mammary epithelial cells (HMECs) that survive early replicative arrest (M0) by the inactivation of p16INK4A during cell culture on plastic dishes leads to a state of permanent replicative arrest termed senescence. While culture of HMECs on feeder layers abrogates M0 and p16INK4A inactivation, progressive telomere attrition in these cells also eventually results in permanent replicative arrest. Expression of telomerase prevents both senescence on plastic (S-P) and senescence on feeder layers (S-FL) in HMECs, as it does also in cultured primary human fibroblasts. We report here that the gene expression profiles of senescence in HMECs of the same lineage maintained under different culture conditions showed surprisingly little commonality. Moreover, neither of these senescence-associated profiles in HMECs resembles the profile for senescence in human fibroblasts. These results indicate that senescence-associated alterations in gene expression resulting from telomere attrition are affected by culture conditions as well as by cell origins, and argue that replicative senescence at the molecular level is a diverse rather than unique cellular process.
Project description:Although senescence has long been implicated in aging-associated pathologies, it is not clearly understood how senescent cells are linked to these diseases. To address this knowledge gap, we profiled cellular senescence phenotypes and mRNA expression patterns during replicative senescence in human diploid fibroblasts. We identified a sequential order of gain-of-senescence phenotypes: low levels of reactive oxygen species, cell mass/size increases with delayed cell growth, high levels of reactive oxygen species with increases in senescence-associated M-NM-2-galactosidase activity (SA-M-NM-2-gal), and high levels of SA-M-NM-2-gal activity. Gene expression profiling revealed four distinct modules in which genes were prominently expressed at certain stages of senescence, allowing us to divide the process into four stages: early, middle, advanced, and very advanced. Interestingly, the gene expression modules governing each stage supported the development of the associated senescence phenotypes. Senescence-associated secretory phenotype-related genes also displayed a stage-specific expression pattern with three unique features during senescence: differential expression of interleukin isoforms, differential expression of interleukins and their receptors, and differential expression of matrix metalloproteinases and their inhibitory proteins. The analysis of time series gene expression level during replicaive senescence.
Project description:<p><strong>BACKGROUND:</strong> Periodontal ligament mesenchymal stem cells (PDLSCs) are a promising cell resource for cell-based regenerative medicine in dentistry. PDLSCs inevitably acquire a senescent phenotype after prolonged in vitro expansion, and the key regulators of cells during replicative senescence remain unclear.</p><p><strong>METHODS:</strong> We cultured periodontal ligament stem cells to passages 4, 10 and 20 (P4, P10, P20). The senescent phenotypes, proliferation and migration ability of PDLSCs (P4, P10, P20) were detected, and non-targeted metabonomic sequencing was performed. We treated PDLSCs with AICAR and detected the expression of FOXO1, FOXO3a, FOXO6 and AMPK phosphorylation (p-AMPK) levels of replicating senescent PDLSCs to explore the correlation between the metabolic changes and the AMPK pathway.</p><p><strong>RESULTS:</strong> Immunofluorescence staining of γ-H2AX, β-galactosidase staining, cell scratch test and qPCR were performed to confirm the occurrence of replicative senescence in PDLSCs during passaging. Three groups of cells at passage 4 (P4), passage 10 (P10) and passage 20 (P20) were collected for non-targeted metabolomics analysis. Metabonomic sequencing showed that the metabolism of replicative senescence in PDLSCs varied significantly. In particular, the content of fatty acid metabolites decreased with senescence, including capric acid, stearic acid, myristic acid and dodecanoic acid. KEGG pathway analysis showed that the AMPK signaling pathway was closely related to AMP levels. The AMP:ATP ratio increased in senescent PDLSCs; however, the levels of p-AMPK and the profile of FOXO1 and FOXO3a, which are downstream of the AMPK signaling pathway, decreased with senescence. We treated PDLSCs with AICAR, an activator of the AMPK pathway, and the phosphorylated AMPK level at P20 PDLSCs was partially restored. </p><p><strong>CONCLUSION:</strong> In summary, our study suggests that the metabolic process of PDLSCs is active in the early stage of senescence, prefers to consume fatty acids, and is attenuated in the later stages of senescence. AMP accumulates in replicative senescent PDLSCs; however, the sensitivity of AMPK phosphorylation sites is impaired, causing senescent PDLSCs to fail to respond to changes in energy metabolism. Our findings provide a new basis for the clinical application of periodontal ligament stem cells.</p>
Project description:Telomere shortening in populations of human mammary epithelial cells (HMECs) that survive early replicative arrest (M0) by the inactivation of p16INK4A during cell culture on plastic dishes leads to a state of permanent replicative arrest termed senescence. While culture of HMECs on feeder layers abrogates M0 and p16INK4A inactivation, progressive telomere attrition in these cells also eventually results in permanent replicative arrest. Expression of telomerase prevents both senescence on plastic (S-P) and senescence on feeder layers (S-FL) in HMECs, as it does also in cultured primary human fibroblasts. We report here that the gene expression profiles of senescence in HMECs of the same lineage maintained under different culture conditions showed surprisingly little commonality. Moreover, neither of these senescence-associated profiles in HMECs resembles the profile for senescence in human fibroblasts. These results indicate that senescence-associated alterations in gene expression resulting from telomere attrition are affected by culture conditions as well as by cell origins, and argue that replicative senescence at the molecular level is a diverse rather than unique cellular process.
Project description:Although senescence has long been implicated in aging-associated pathologies, it is not clearly understood how senescent cells are linked to these diseases. To address this knowledge gap, we profiled cellular senescence phenotypes and mRNA expression patterns during replicative senescence in human diploid fibroblasts. We identified a sequential order of gain-of-senescence phenotypes: low levels of reactive oxygen species, cell mass/size increases with delayed cell growth, high levels of reactive oxygen species with increases in senescence-associated β-galactosidase activity (SA-β-gal), and high levels of SA-β-gal activity. Gene expression profiling revealed four distinct modules in which genes were prominently expressed at certain stages of senescence, allowing us to divide the process into four stages: early, middle, advanced, and very advanced. Interestingly, the gene expression modules governing each stage supported the development of the associated senescence phenotypes. Senescence-associated secretory phenotype-related genes also displayed a stage-specific expression pattern with three unique features during senescence: differential expression of interleukin isoforms, differential expression of interleukins and their receptors, and differential expression of matrix metalloproteinases and their inhibitory proteins.
Project description:Cellular replicative senescence, a state of permanent cell-cycle arrest that occurs following an extended period of cell division in culture, has been linked to organismal aging, tissue repair and tumorigenesis. In this study, we comparatively investigated the global lipid profiles and mRNA content of proliferating and senescent-state BJ fibroblast cells. We found that both the expression levels of lipid-regulating genes, as well as the abundance of specific lipid families, are actively regulated. We further found that 19 polyunsaturated triacylglycerol species showed the most prominent changes during replicative senescence. We argue that diversion of polyunsaturated fatty acids to glycerolipid biosynthesis could be responsible for the accumulation of specific triacylglycerols. This, in turn, could be one of the cellular mechanisms to prevent lipotoxicity under increased oxidative stress conditions observed during replicative senescence. Collectively, our results place regulation of specific lipid species to a central role during replicative senescence.
Project description:Matrix elasticity influences differentiation of mesenchymal stem cells (MSCs) but it is unclear if these effects are only transient - while the cells reside on the substrate - or if they reflect persistent lineage commitment. In this study, MSCs were continuously culture-expanded in parallel either on polydimethylsiloxane (PDMS) gels of different elasticity or on tissue culture plastic (TCP) to compare impact on replicative senescence, in vitro differentiation, gene expression, and DNA methylation (DNAm) profiles. The maximal number of cumulative population doublings was not affected by matrix elasticity. Differentiation towards adipogenic and osteogenic lineage was increased on soft and rigid biomaterials, respectively - but this propensity was no more evident if cells were transferred to TCP. Global gene expression profiles and DNAm profiles revealed relatively few differences in MSCs cultured on soft or rigid matrices. Furthermore, only moderate DNAm changes were observed upon culture on very soft hydrogels of human platelet lysate. Our results support the notion that matrix elasticity influences cellular differentiation while the cells are organized on the substrate, but it does not have major impact on cell-intrinsic lineage determination, replicative senescence or DNAm patterns. MSCs cultivated either on polydimethylsiloxane (PDMS) gels of different elasticity or on tissue culture plastic (TCP) to compare impact on gene expression profiles.
Project description:Cells in culture undergo replicative senescence. In this study, we analyzed functional, genetic and epigenetic sequels of long‐term culture in human mesenchymal stem cells (MSC). Already within early passages the fibroblastoid colony‐ forming unit (CFU‐f) frequency and the differentiation potential of MSC declined significantly. Relevant chromosomal aberrations were not detected by karyotyping and SNP‐microarrays. Subsequently, we have compared DNA‐methylation profiles with the Infinium HumanMethylation27 Bead Array and the profiles differed markedly in MSC derived from adipose tissue and bone marrow. Notably, all MSC revealed highly consistent senescence‐associated modifications at specific CpG sites. These DNA‐methylation changes correlated with histone marks of previously published data sets, such as trimethylation of H3K9, H3K27 and EZH2 targets. Taken together, culture expansion of MSC has profound functional implications ‐ these are hardly reflected by genomic instability but they are associated with highly reproducible DNA‐methylation changes which correlate with repressive histone marks. Therefore replicative senescence seems to be epigenetically controlled. 8 samples of mesenchymal stem cells (MSC) from human adipose tissue
Project description:This SuperSeries is composed of the following subset Series: GSE3730: Replicative senescence in human fibroblasts GSE3731: Replicative senescence in post-selection HMECs Abstract: Replicative senescence is the state of irreversible proliferative arrest that occurs as a concomitant of progressive telomere shortening. By using cDNA microarrays and the gabriel system of computer programs to apply domain-specific and procedural knowledge for data analysis, we investigated global changes in gene transcription occurring during replicative senescence in human fibroblasts and mammary epithelial cells (HMECs). Here we report the identification of transcriptional "fingerprints" unique to senescence, the finding that gene expression perturbations during senescence differ greatly in fibroblasts and HMECs, and the discovery that despite the disparate nature of the chromosomal loci affected by senescence in fibroblasts and HMECs, the up-regulated loci in both types of cells show physical clustering. This clustering, which contrasts with the random distribution of genes down-regulated during senescence or up-regulated during reversible proliferative arrest (i.e., quiescence), supports the view that replicative senescence is associated with alteration of chromatin structure. Refer to individual Series