Stem cell experiments and initial clinical trial of cellular cardiomyoplasty.

Growing myocardial cells from human stem cells and stem cell transplantation to repair injured myocardium are new frontiers in cardiovascular research. The 1st stage of this study was conducted to determine whether transplantation of autologous bone marrow stem cells into infarcted myocardium of sheep could differentiate into beating cardiomyocytes. The 2nd stage was to demonstrate transdifferentiation of human bone marrow mesenchymal stem cells to precursor cardiomyocytes in vitro, using a novel conditioning medium. In the 3rd stage, a clinical trial of stem cell implantation in patients with severe myocardial dysfunction involved injection of peripheral blood-derived endothelial precursor cells in 11 patients and autologous bone marrow mononuclear cells in 29. A marginal improvement in myocardial function was noted at 3 months (mean increase in ejection fraction, 6% +/- 1%), although it plateaued at 6 months. The trial proved to be safe because there was no procedure-related mortality. There is growing optimism that stem cell therapy may delay heart transplantation.