抄録
We have isolated a cardiomyogenic cell line (CMG cell) from murine bone marrow stromal cells. Stromal cells were immortalized, treated with 5-azacytidine, and spontaneous beating cells were repeatedly screened for. The cells showed a f ibroblast-like morphology, but the morphology changed after 5-azacytidine treatment in approximately 30% of the cells : they connected with adjoining cells after 1 week, formed myotube-like structures and began spontaneous beating after 2 weeks, and beat synchronously after 3 weeks. They expressed ANP and BNP. Electron microscopy revealed a cardiomyocyte-like ultrastructure including typical sarcomeres and atrial granules. These cells had several types of action potentials : sinus node like and ventricular cell-like action potentials. All cells had a long action potential duration or plateau, a relatively shallow resting membrane potential, and a pacemaker-like late diastolic slow depolarization. Analysis of the isoform of contractile protein genes, such as myosin heavy chain, myosin light chain and α-actin, indicated that their muscle phenotype was similar to fetal ventricular cardiomyocytes. These cells expressed Nkx 2.5/Csx, GATA 4, TEF-1 and MEF-2 C mRNA before 5-azacytidine treatment, and expressed MEF-2 A and MEF-2 D after treatment. This new cell line provides a powerful model for the study of cardiomyocyte differentiation.
