Methylome analysis of human bone marrow MSCs reveals extensive age and culture induced changes at distal regulatory elements

Human mesenchymal stem cells (MSCs) need expansion prior to use as cell-based therapies in immunological and tissue repair applications. Aging and expansion of MSCs induce epigenetic changes that can impact therapeutic outcomes. By applying sequencing-based methods, we reveal that the breadth of DNA methylation dynamics associated with aging and expansion are greater than previously reported. Methylation changes are enriched at known distal transcription factor binding sites such as enhancer elements instead of CpG-rich regions and are associated with changes in gene expression. From this, we constructed hypo- and hypermethylation specific regulatory networks, including a sub-network of MSC master regulators and their predicted target genes, and identified putatively disrupted signaling pathways. Our genome-wide analyses provide a broader overview of age and expansion induced DNA methylation changes, and a better understanding of the extent to which these changes alter gene expression and functionality of human bone marrow MSCs.