Epigenetic status of cardiac master genes in native adipose derived stem cells

Adipose derived stem cells (ADSCs) are mesenchymal stem cells that can be easly isolated from lipoaspirates. They show multilineage differentiative capacities, including the cardiac phenotype. Therefore they represent a promise for regenerative medicine (Zuk 2001), for the treatment of those diseases affecting organs with extremely low potential of repair and regeneration, such as the heart. The knowledge of the molecular mechanisms that control development and differentiation - such as epigenetic DNA promoter methylation at CpG sites and histone modifications inducing chromatin remodelling and changes in DNA accessibility (Bernstein 2007) - will help to understand their potential in this regard. Aim of this study was to evaluate the epigenetic status of cardiac specific transcription factors,such as GATA-4, MEF-2C and Nkx2.5 (Brand 2003) in undifferentiated human ADSCs. The analysis of DNA promoter methylation, using Methylation Specific PCR (MSP), revealed the unmethylated status of the promoters of the above cardiac master genes. This finding suggested that ADSCs are not prevented to differentiate towards the cardiac phenotype by DNA methylation, as otherwise reported for myogenic genes (Sørensen 2010). Chromatin immunoprecipitation (ChIP) showed association of a well known transcriptional repressive mark [trimethylation of Lys27 in H3 (H3K27me3)] with GATA-4 and Nkx2.5 promoters. On the other hand, an enrichment in acetylation of histone 3 (acH3), hallmark of transcriptional potential, was detected for MEF-2C promoter. These results are in agreement with those of the gene expression analysis, showing the presence of only MEF-2C transcript in total mRNA extracted from undifferentiated human ADSCs of three different donors. In conclusion our results suggest that the epigenetic signature of ADSCs represents a level for intervention to address their differentiation towards the cardiac lineage.