Cardiomyogenic potential of human adult bone marrow mesenchymal stem cells in vitro

Background: The aim of this study was to investigate the ability of adult human bone marrow mesenchymal stem cells to differentiate towards a cardiomyogenic phenotype in vitro. Methods: Bone marrow samples were aspirated from 30 patients undergoing open heart surgery from the anterior iliac crest. Second passaged cells were treated with 10 mu M 5-azacytidine. As control groups we used cells not expanded in culture and cells untreated with 5-azacytidine. Morphologic characteristics were analysed by confocal and electron microscopy. The expression of the cytoskeletal protein vimentin and muscle-specific myocin heavy chain was analysed by immunohistochemistry. The expression of the cardiomyocyte specific genes alpha-cardiac actin, beta-myocin heavy chain and cardiac troponin-T was detected by reverse transcriptase polymerase chain reaction. Results: Mesenchymal stem cells were spindle-shaped with irregular processes. Cells treated with 5-azacytidine assumed a stick-like morphology. They connected with adjoining cells to form myotube-like structures. Numerous myofilaments were detected in induced cells which were immunohistochemically positive for myosin heavy chain and vimentin. The mRNAs of all specific cardiac genes were expressed in both induced and uninduced cells. Conclusion: These results indicate that adult human bone marrow mesenchymal stem cells treated with 5-aza can differentiate towards a cardiomyogenic lineage in vitro.