Epigenetic Dysregulation in Mesenchymal Stem Cell Aging and Spontaneous Differentiation

Abstract

BackgroundMesenchymal stem cells (MSCs) hold great promise for the treatment of difficult diseases. As MSCs represent a rare cell population, ex vivo expansion of MSCs is indispensable to obtain sufficient amounts of cells for therapies and tissue engineering. However, spontaneous differentiation and aging of MSCs occur during expansion and the molecular mechanisms involved have been poorly understood.Methodology/Principal FindingsHuman MSCs in early and late passages were examined for their expression of genes involved in osteogenesis to determine their spontaneous differentiation towards osteoblasts in vitro, and of genes involved in self-renewal and proliferation for multipotent differentiation potential. In parallel, promoter DNA methylation and hostone H3 acetylation levels were determined. We found that MSCs underwent aging and spontaneous osteogenic differentiation upon regular culture expansion, with progressive downregulation of TERT and upregulation of osteogenic genes such as Runx2 and ALP. Meanwhile, the expression of genes associated with stem cell self-renewal such as Oct4 and Sox2 declined markedly. Notably, the altered expression of these genes were closely associated with epigenetic dysregulation of histone H3 acetylation in K9 and K14, but not with methylation of CpG islands in the promoter regions of most of these genes. bFGF promoted MSC proliferation and suppressed its spontaneous osteogenic differentiation, with corresponding changes in histone H3 acetylation in TERT, Oct4, Sox2, Runx2 and ALP genes.Conclusions/SignificanceOur results indicate that histone H3 acetylation, which can be modulated by extrinsic signals, plays a key role in regulating MSC aging and differentiation.

Osteogenic lineage commitment of mesenchymal stem cells from patients with ossification of the posterior longitudinal ligament

“…However, the process for the spontaneous phenotypic differentiation of MSCs into osteoprogenitor cells or osteoblasts has not been clearly elucidated. Some authors suggest that miRNA and epigenetic alterations regulate osteogenic differentiation of progenitor cells in muscle sites and in vitro [23,24]. We, too, hypothesize that genetic and epigenetics aspects are major factors controlling lineage commitment of MSCs.…”

Correlation between telomere maintenance and stemness of mesenchymal stem/stromal cells

“…Contrary, SHEDs, PDL-MSCs and AT-MSCs, possessed lower RTL values and hTERT mRNA expression, but higher expression of Cbfa1, major transcriptional factor of osteogenesis. Negative correlation between expression of Cbfa1 and TERT was also described in human bone marrow [32] and placental MSCs [33] .…”

Epigenetic Modifications upon Senescence of Mesenchymal Stem Cells

“…Several transcription factors involved in differentiation, stem cell development, and tumorigenesis have significant enrichment of binding motives in differentially methylated regions as well as in promoters of differentially expressed genes during senescence [18•]. However, the promoter methylation of relevant genes for osteogenesis, such as runt-related transcription factor 2 (RUNX2) and alkaline phosphatase (ALP) [48] or adipogenesis, such as fatty acid binding protein 4 (FABP4) and lipoprotein lipase (LPL) [46], remains unchanged in the course of cellular senescence. Therefore, DNAm is a relevant epigenetic mechanism in the differentiation commitment, but not essential.…”

“…Treatment with HDAC inhibitors indicates that HDAC activity is essential for maintenance of self-renewal, multipotency, and differentiation potential of MSCs [52]. Expression changes of several genes that are relevant for self-renewal (OCT4 and SOX2) or for maintenance of telomeres (hTERT) seem to be associated with a decreased acetylation of histone 3 at lysine 9 or 14 (H3K9ac or H3K14ac) in the promoter regions [48]. H3K9ac and H3K14ac are required for the recruitment of different transcription factors [53] and the chromatin remodeling complex SWI/SNF, to initiate the transcription [54].…”