In vitro Expansion of Hematopoietic Stem Induces Gene Expression Changes

Hematopoietic stem and progenitor cells (HPCs) can be maintained in vitro, but the vast majority of their progeny loses “stemness” during culture. We have analyzed DNA methylation (DNAm) profiles of freshly isolated CD34+ cells and upon expansion on either tissue culture plastic (TCP) or mesenchymal stromal cells (MSCs). Cultured HPCs acquired significant DNA-hypermethylation, particularly in up-stream promoter regions and shore-regions of CpG islands (CGIs). To analyze if these DNAm changes are relevant for differential gene expression we analyzed gene expression profiles of additional samples. As expected highly expressed genes (10% with highest signal intensity in gene expression arrays) were hardly methylated at promoter regions, CGIs and shore-regions. 9 samples were hybridized GeneChip Human Gene 1.0 ST Arrays (Affymetrix)