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Effects of electrical fields on cardiomyocyte differentiation of embryonic stem cells

The effects of electromagnetic fields (EMFs) on the differentiation of cardiomyocytes in embryoid bodies derived from pluripotent embryonic stem (ES) cells were investigated. A single direct current (DC) field pulse was applied to 4‐day‐old embryoid bodies. The electrical field induced a hyperpolarization of the anode‐facing side of embryoid bodies and a depolarization at the cathode‐facing side. Significant effects of a single electrical field pulse applied for 90 s on cardiomyocyte differentiation were achieved with field strengths of 250 and 500 V/m, which increased both the number of embryoid bodies differentiating beating foci of cardiomyocytes and the size of the beating foci. The 500‐V/m electrical field increased intracellular reactive oxygen species (ROS), but not [Ca2+]i and activated nuclear factor kappa B (NF‐κB). A comparable increase in the number of beating embryoid bodies was achieved by an incubation for 1 h with H2O2 (1–10 nM), indicating that the electrical field effect was transduced via the intracellular generation of ROS. Because the radical scavengers dehydroascorbate and pyrrolidinedithiocarbamate (APDC) and the NF‐κB antagonist N‐tosyl‐L‐phenylalanine chloromethyl ketone (TPCK) inhibited cardiac differentiation, we assume that ROS and NF‐κB may play a role in early cardiac development. J. Cell. Biochem. 75:710–723, 1999. © 1999 Wiley‐Liss, Inc.