Effect of 5-azacytidine: evidence for alteration of the multipotent ability of mesenchymal stem cells.

The treatment of cardiac diseases by cell therapy continues to be challenged by a limited supply of appropriate cells. Although stem cells can generate myocytes after local delivery into the heart, this is often accompanied by the generation of several other cell types as a consequence of environment-driven differentiation. One strategy for overcoming dysregulated differentiation is the pretreatment of stem cells with the demethylation agent 5-azacytidine. The effects of 5-azacytidine on various stem cell types vary from cardiomyogenic differentiation to failure of differentiation or from adipogenic and chondrogenic differentiation to uncontrollable expression of a variety of genes. The underlying mechanisms remain poorly understood, and the effect of 5-azacytidine on the multipotent capacity of stem cells has never been addressed. This study was designed to investigate the changes induced by 5-azacytidine in mesenchymal stem cells (MSC), with particular focus on multipotency maintenance and the capacity of 5-azacytidine to boost myogenic differentiation. Our results show that MSCs retained their multipotent capacity after one pulse with 5-azacytidine, whereas additional pulses resulted in a restricted differentiation potential with concomitant increased ability to accomplish chondrogenic commitment. The induction of cardiac differentiation of MSCs was not observed unless the transcriptional activation of several genes was induced by random hypomethylation. Nevertheless, 5-azacytidine treatment promoted cell response to subsequent stimuli and generation of myogenic differentiation under permissive environmental conditions. Therefore, we assume that one pulse with 5-azacytidine might similarly promote the subsequent cardiac differentiation of MSCs, but it is dependent on the finding of adequate conditions for myocardial differentiation.