Abstract 5280: Comparing Epigenetic Modifications of Adult Progenitor Cells
Cell therapy is a promising option for treatment of cardiovascular diseases. Recent studies demonstrate that pluripotency can be induced in somatic cells by a combination of genes such as Oct4, Klf4, c-Myc and Sox2. To address whether adult progenitor cells might express some of the pluripotency genes and therefore might be more easily reprogrammable, we analyzed expression and accessibility of the promoters of pluripotency genes in adult progenitor cells. Oct4 mRNA was expressed at low level (0.2–0.5% compared to human embryonic stem cells (ESC)) in peripheral blood derived early endothelial progenitor cells (EPC), bone marrow-derived mesenchymal stem cells (MSC) and CD34+ cells, whereas neuronal stem cells (NSC) did not express Oct4. Klf4 mRNA was highly expressed in EPC, MSC and CD34+ cells but not in NSC. Interestingly, Sox2 was selectively expressed in NSC (71,65±13,01%) but was low in EPC, MSC and CD34+ (< 4% of hESC). To investigate whether epigenetic mechanisms account for the differential expression of the pluripotency genes, we analyzed promoter DNA methylation by bisulfite sequencing with 2 different primers. The Oct4 promoter showed high incidence of methylated CpG islands in Region A (EPC:82%; MSC:87%; CD34+ 71% compared to ESC: 5 %). Interestingly, the DNA methylation of the Nanog promoter in Region B was low in EPC (37%), MSC (8%), and ESC (9 %) in contrast to CD34+ cells (97%). At the level of histones, chromatine immunoprecipitation experiments demonstrated that the active marks, acetylated-histone H3 (H3Ac) and trimethylation of H3 lysine 4 (H3K4m3) were increased at the Nanog promoter in EPC and MSC. The Sox2 promoter showed a bivalent modification with active H3K4me3 and repressive H3K27m3 marks in EPC, MSC and CD34+. The Klf4 promoter exhibits high levels of active H3Ac and H3K4m3 but no repressive modification in EPC, MSC and CD34+ cells. These data indicate that adult progenitor cells express variable levels of the pluripotency genes. Modification of the epigenetic histone code, e.g. by histone demethylases, might facilitate the induction of pluripotency by remodeling the accessibility of the promoter regions. This may provide an attractive tool to reprogram adult progenitor cells to generate patient-specific stem cells.