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: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.
Project description:Primary cells enter replicative senescence after a limited number of cell divisions. This process is associated with reproducible changes in DNA methylation (DNAm) at specific sites in the genome. The mechanism that drives senescence-associated DNAm changes remains unknown and may arise through drift in DNAm or through regulated, senescence dependent modifications at specific sites in the genome. In this study, we analyzed the reorganization of nuclear architecture and DNA methylation during long-term culture of human fibroblasts and mesenchymal stromal cells (MSCs). [MethylCap-seq] Fibroblasts of two female donors (both 43 years old) were culture expanded and DNA was harvested of 10,000,000 cells at early passage (P3 or P5) and late passage (P30 and P33). DNA methylation changes were subsequently analyzed by MethylCap-Seq.
Project description:Pathogenic mutations in lamin A/C (LMNA) lead to nuclear structural abnormalities, mesenchymal tissue damage, and laminopathies, which have numerous tissue-specific and progeria phenotypes. However, how LMNA mutations lead to accelerated mesenchymal-derived cell senescence remains unclear. Here, we established a replicative senescence model in vitro using induced pluripotent stem cell-derived mesenchymal stem cells (iMSCs) from patients with homozygous LMNA p.R527C mutation (LMNA R527C iMSCs). R527C iMSCs exhibited marked cell senescence and stemness potential attenuation, accompanied by immunophenotypic changes when expanded to passage 13 in vitro. Proteome analysis revealed that DNA replication, nuclear structure, and chromatin-related gene sets were the most significant changes in R527C iMSCs during replicative senescence, and pathways such as cell cycle, DNA replication, cell adhesion, and inflammation might play important roles in senescence.
Project description:Altered DNA methylation and associated destabilization of genome integrity and function is a hallmark of cancer. Replicative senescence imposes a limit on proliferative potential that all cancer cells must bypass. Compared to proliferating cells, senescent cells exhibit marked chromatin re-organization. Here we show by whole-genome single-nucleotide bisulfite sequencing that replicative senescent human cells exhibit widespread alterations in their DNA methylome. These changes are linked to mislocalization of the maintenance DNA methyltransferase (DNMT1) in cells approaching senescence, altered replication-coupled DNA methylation and de-repression of repetitive satellite sequences. Deficiency of DNMT1 triggers chromatin changes characteristic of senescence and expression of satellite sequences. Most importantly, but paradoxically, gains and losses of methylation in replicative senescence are similar to those in cancer, and this M-bM-^@M-^XreprogrammedM-bM-^@M-^Y methylation landscape is largely retained when cells escape or bypass senescence. In sum, altered regulation of DNMT1 in cells approaching replicative senescence contributes to changes in chromatin structure and function. Consequently, if senescent cells escape the proliferative barrier, they already harbor epigenetic changes likely to promote malignancy. Examination of methylation status in IMR90 cells
Project description:In differentiated cells, aging is associated with hypermethylation of DNA regions enriched in repressive histone posttranslational modifications. However, the chromatin marks associated with changes in DNA methylation in adult stem cells during lifetime are still largely unknown. Here, DNA methylation profiling of mesenchymal stem cells obtained from individuals aged 2 to 92 identified 18735 hypermethylated and 45407 hypomethylated CpG sites associated with aging. As in differentiated cells, hypermethylated sequences were enriched in chromatin repressive marks. Most importantly, hypomethylated CpG sites were strongly enriched in the active chromatin mark H3K4me1 in stem and differentiated cells, suggesting this is a cell type-independent chromatin signature of DNA hypomethylation during aging. Analysis of scedasticity showed that interindividual variability of DNA methylation increased during aging in MSCs and differentiated cells, providing a new avenue for the identification of DNA methylation changes over time. DNA methylation profiling of genetically identical individuals showed that both the tendency of DNA methylation changes and scedasticity depended on non-genetic as well as genetic factors. Our results indicate that the dynamics of DNA methylation during aging depend on a complex mixture of factors that include the DNA sequence, cell type and chromatin context involved, and that, depending on the locus, the changes can be modulated by genetic and/or external factors. Total DNA isolated by standard procedures from human adult mesenchymal stem cells (MSCs) obtained from 34 individuals aged 2 to 92
Project description:Pluripotent stem cells evade replicative senescence, whereas other primary cells lose their proliferation and differentiation potential after a limited number of cell divisions M-bM-^@M-^S and this is accompanied by specific senescence-associated DNA methylation (SA-DNAm) changes. Here, we investigate SA-DNAm changes in mesenchymal stromal cells (MSC) upon long-term culture, irradiation-induced senescence, immortalization and reprogramming into induced pluripotent stem cells (iPSC) using high density HumanMethylation450 BeadChips. SA-DNAm changes are highly reproducible and occur particularly in intergenic and non-promoter regions of developmental genes. We demonstrate that ionizing irradiation, although associated with a very similar senescence phenotype, does not affect SA-DNAm. Furthermore, overexpression of the catalytic subunit of the human telomerase (TERT) or conditional immortalization with a doxycycline-inducible system (TERT and SV40 TAg) result in telomere extension but do not influence SA-DNAm. In contrast, we demonstrate that reprogramming into iPSC prevented SA-DNAm changes. Our results indicate that replicative senescence is associated with an epigenetically controlled process which stalls cells in a particular differentiated state, whereas irradiation-induced senescence and immortalization are not causally related to this process. Absence of SA-DNAm in pluripotent cells may play a central role for their escape from cellular senescence. Samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Primary cells enter replicative senescence after a limited number of cell divisions. This process is associated with reproducible changes in DNA methylation (DNAm) at specific sites in the genome. The mechanism that drives senescence-associated DNAm changes remains unknown and may arise through drift in DNAm or through regulated, senescence dependent modifications at specific sites in the genome. In this study, we analyzed the reorganization of nuclear architecture and DNA methylation during long-term culture of human fibroblasts and mesenchymal stromal cells (MSCs). [RNA-seq]
Project description:Primary cells enter replicative senescence after a limited number of cell divisions. This process is associated with reproducible changes in DNA methylation (DNAm) at specific sites in the genome. The mechanism that drives senescence-associated DNAm changes remains unknown and may arise through drift in DNAm or through regulated, senescence dependent modifications at specific sites in the genome. In this study, we analyzed the reorganization of nuclear architecture and DNA methylation during long-term culture of human fibroblasts and mesenchymal stromal cells (MSCs). [MethylCap-seq]
Project description:Mesenchymal stromal cells (MSC) were isolated from human bone marrow. Here, we have compared gene expression profiles of MSC at early and late passages. Long-term culture associated gene expression changes were then correlated with DNA-methylation profiles. The goal of this study was to determine if senescence-associated DNA-methylation (SA-DNAm) changes are reflected by differential gene expression. Overall, genes with SA-DNAm changes (particularly with SA-hypomethylation) were detected at low level and seemed to be scarcely expressed at early and late passages. MSC were isolated from three different donors and culture expanded until replicative senescence. Gene expression profiles were compared at early and late passage using GeneChip Humang Gene 1.0 ST arrays (Affymetrix). Six hybridizations are included in this series.