Pluripotent stem cells escape from senescence-associated DNA methylation changes.
Pluripotent stem cells evade replicative senescence, whereas other primary cells lose their proliferation and differentiation potential after a limited number of cell divisions, 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 they are enriched in intergenic and nonpromoter regions of developmental genes. Furthermore, SA-hypomethylation in particular appears to be associated with H3K9me3, H3K27me3, and Polycomb-group 2 target genes. We demonstrate that ionizing irradiation, although associated with a 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 prevent SA-DNAm. In contrast, we demonstrate that reprogramming into iPSC prevents almost the entire set of SA-DNAm changes. Our results indicate that long-term culture is associated with an epigenetically controlled process that stalls cells in a particular functional 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.
Helmholtz Institute for Biomedical Engineering, RWTH Medical School, 52074 Aachen, Germany.
Carmen M
CM
Koch
Kristina
K
Reck
Kaifeng
K
Shao
Qiong
Q
Lin
Sylvia
S
Joussen
Patrick
P
Ziegler
Gudrun
G
Walenda
Wolf
W
Drescher
Bertram
B
Opalka
Tobias
T
May
Tim
T
Brümmendorf
Martin
M
Zenke
Tomo
T
Saric
Wolfgang
W
Wagner
D000328:Adult; D000368:Aged; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics* / Q000528:radiation effects; D019175:DNA Methylation / Q000528:radiation effects; D044127:Epigenesis, Genetic / Q000528:radiation effects; D005720:Gamma Rays / Q000009:adverse effects; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000378:metabolism / Q000528:radiation effects; D059630:Mesenchymal Stem Cells / Q000378:metabolism / Q000528:radiation effects; D008875:Middle Aged; D008954:Models, Biological; D039904:Pluripotent Stem Cells / Q000378:metabolism* / Q000528:radiation effects