Pluripotent Stem Cells Escape From Senescence-Associated DNA Methylation Changes
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ABSTRACT: This SuperSeries is composed of the following subset Series: GSE37065: Long-term culture associated gene expression changes in MSC [Affymetrix] GSE37066: Pluripotent Stem Cells Escape From Senescence-Associated DNA Methylation Changes [Illumina] GSE38806: Gene expression profiles of induced pluripotent mesenchymal stromal cells [Affymetrix] Refer to individual Series
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:Reprogramming of somatic cells into induced pluripotent stem cells (iPSC) is an epigenetic phenomenon. It has been suggested that iPSC retain some tissue-specific memory whereas little is known about inter-individual epigenetic variation of iPSC clones. In this study we have reprogrammed mesenchymal stromal cells (MSC) from human bone marrow by retrovirus-mediated overexpression of OCT-3/4, SOX2, c-MYC, and KLF4. Global DNA-methylation profiles of the initial MSC, MSC-derived iPSC (iP-MSC) and embryonic stem cells (ESC) were then compared using a high density DNA-methylation array covering more than 450,000 CpG sites. Overall, DNA-methylation patterns of iP-MSC and ESC were similar whereas some CpG sites revealed highly significant differences, which were not related to parental MSC. Furthermore, hypermethylation in iP-MSC versus ESC was particularly enriched in developmental genes as well as shore regions next to CpG islands indicating that these differences are not due to tissue-specific memory or random de novo methylation. Subsequently, we searched for CpG sites with donor-specific variation in MSC preparations. These “epigenetic fingerprints” were highly enriched in non-promoter regions and outside of CpG islands – and they were maintained upon reprogramming into iP-MSC. In conclusion, DNA methylation profiles of iP-MSC clones from the same donor were closely related despite heterogeneity of MSC. On the other hand, iP-MSC maintain donor-derived epigenetic differences. In the absence of isogenic controls for disease modeling applications, it would therefore be more appropriate to compare iPSC from different donors rather than a high number of different clones from the same patient. 16 samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Reprogramming of somatic cells into induced pluripotent stem cells (iPSC) is an epigenetic phenomenon. We have reprogrammed mesenchymal stromal cells (MSC) from human bone marrow by retrovirus-mediated overexpression of OCT-3/4, SOX2, c-MYC, and KLF4. This series summarizes gene expression profiles of eight iP-MSC clones derived from three different donors. These datasets were subsequently used for PluriTest analysis (Muller FJ, Schuldt B et al., Nat. Methods 2011; 8: 315-317) demonstrating that all iP-MSC clones were clearly associated with pluripotent cells. Eight iP-MSC clones derived from three different donors.
Project description:Standardization of mesenchymal stromal cells (MSCs) remains a major obstacle in regenerative medicine. Starting material and culture expansion affect cell preparations and render comparison between studies difficult. In contrast, induced pluripotent stem cells (iPSCs) assimilate towards a ground-state and may therefore give rise to more standardized cell preparations. We reprogrammed bone marrow MSCs into iPSCs which were subsequently re-differentiated towards MSCs. These iPS-MSCs revealed similar morphology, immunophenotype, in vitro differentiation potential, and gene expression profiles as primary MSCs. DNA methylation (DNAm) profiles of iPSCs maintained some donor-specific characteristics, whereas tissue-specific, senescence-associated, and age-related DNAm patterns were erased during reprogramming. iPS-MSCs reacquired senescence-associated DNAm during culture expansion but they remained rejuvenated with regard to age-related DNAm. Overall, iPS-MSCs and MSCs are similar in function but differ in their epigenetic makeup. 8 samples were hybridized to the GeneChip Human Gene 1.0 ST Array (Affymetrix)
Project description:Standardization of mesenchymal stromal cells (MSCs) remains a major obstacle in regenerative medicine. Starting material and culture expansion affect cell preparations and render comparison between studies difficult. In contrast, induced pluripotent stem cells (iPSCs) assimilate towards a ground-state and may therefore give rise to more standardized cell preparations. We reprogrammed bone marrow MSCs into iPSCs which were subsequently re-differentiated towards MSCs. These iPS-MSCs revealed similar morphology, immunophenotype, in vitro differentiation potential, and gene expression profiles as primary MSCs. DNA methylation (DNAm) profiles of iPSCs maintained some donor-specific characteristics, whereas tissue-specific, senescence-associated, and age-related DNAm patterns were erased during reprogramming. iPS-MSCs reacquired senescence-associated DNAm during culture expansion but they remained rejuvenated with regard to age-related DNAm. Overall, iPS-MSCs and MSCs are similar in function but differ in their epigenetic makeup. 12 samples were hybridized to the Illumina Infinium 450k Human Methylation Beadchip
Project description:Polycomb group (PcG) proteins comprise a large group of evolutionary conserved factors with essential roles for embryonic development and adult stem cell function. PcG proteins constitute two main multiprotein polycomb repressive complexes (PRC1 and PRC2) that operate in a hierarchical manner to silence gene expression. Functionally distinct PRC1 complexes are defined by Polycomb group RING finger protein (PCGF) paralogs. So far, six PCGF paralogs (PCGF1-6) have been identified but paralog-specific functions are not well understood. In our studies, we observed that Pcgf6 showed the highest expression level in undifferentiated murine embryonic stem cells (ESCs), blastocysts and testes. When ESCs differentiated, Pcgf6 expression strongly declined. To further investigate Pcgf6 biology, we established dox-inducible shRNA knockdown (KD) ESCs. Following Pcgf6 KD in ESCs the expression of pluripotency genes decreased, while mesodermal- and spermatogenesis-specific genes were de-repressed. Concomitantly with the elevated expression of mesodermal lineage markers, Pcgf6 KD ESCs showed increased hemangioblastic and hematopoietic activities. Finally, PCGF6 replaced SOX2 but not KLF4 or c-MYC in the generation of germline-competent iPS cells. Forced expression of Pcgf6 in OSKM-driven reprogramming increases iPS efficiency while Pcgf6 KD reduces the formation of ESC-like colonies. Together, these analyses show that Pcgf6 is non-redundantly involved in maintaining the pluripotent nature of ESCs and functions in iPS reprogramming. 6 samples were hybridized GeneChip Mouse Gene 1.0 ST Arrays (Affymetrix)
Project description:Surface topography impacts on cell growth and differentiation, but it is not trivial to generate defined surface structures and to assess the relevance of specific topographic parameters. In this study, we have systematically compared in vitro differentiation of mesenchymal stem cells (MSCs) on a variety of groove/ridge structures. Micro- and nano-patterns were generated in polyimide using reactive ion etching or multi beam laser interference, respectively. These structures affected cell spreading and orientation of human MSCs, which was also reflected in focal adhesions morphology and size. Time-lapse demonstrated directed migration parallel to the nano-patterns. Overall, surface patterns clearly enhanced differentiation of MSCs towards specific lineages: 15 um ridges increased adipogenic differentiation whereas 2 um ridges enhanced osteogenic differentiation. Notably, nano-patterns with a periodicity of 650 nm increased differentiation towards both osteogenic and adipogenic lineages. However, in absence of differentiation media surface structures did neither induce differentiation, nor lineage-specific gene expression changes. Furthermore, nanostructures did not affect the YAP/TAZ complex, which is activated by substrate stiffness. Our results provide further insight into how structuring of tailored biomaterials and implant interfaces - e.g. by multi beam laser interference in sub-micrometer scale - do not induce differentiation of MSCs per se, but support their directed differentiation.
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 and upon stimulation with transforming growth factor beta 1 (TGF-b1). Stimulation was performed with 1ng/mL TGF-b1 for 1, 4, or 12 hours as indicated. The goal of this study was to determine if senescence-associated gene expression changes and TGF-b1 induced gene expression changes are related. 24 samples were hybridized GeneChip Human Gene 1.0 ST Arrays (Affymetrix)
Project description:Cells in culture undergo replicative senescence and unequivocally stop proliferation after a limited number of cell divisions. In this study, we have expanded mesenchymal stem cells (MSC) from human adipose tissue and analyzed genetic and epigenetic sequels. The subpopulation of highly proliferative cells and the in vitro differentiation potential decayed already within early passages. Relevant chromosomal aberrations were not detected by karyotyping and SNP-microarrays. Comparison of early and late passage of five samples of mesenchymal stem cells from human adipose tissue.