INTERFERENTIAL ELECTRIC FIELD TREATMENT REVEALED A LOW INCREASE OF SPONTANEOUS CARDIAC DIFFERENTIATION BUT NO CYCLIC AMP CHANGES NOR INDUCTION OF CARDIAC-SPECIFIC GENE EXPRESSION IN PLURIPOTENT EMBRYONAL CARCINOMA P19 CELLS

Abstract

Earlier studies showed that interferential currents (IFC) can modulate intracellular cAMP levels in fibroblasts. Based on these findings, an open prospective study to treat palmar psoriasis showed that IFC leads to an improvement of psoriatic skin. Here, we investigated whether 4 kHz interferential electric fields modulated at 10, 50, and 100 Hz are able to induce cardiac differentiation in pluripotent embryonal carcinoma (EC) P19 cells. P19 cells differentiated as embryoid bodies (EBs) in suspension culture were exposed to interferential fields during cultivation days 4 to 6 between capacitor plates (field strength 100 V/m). Signals were applied for 5 min at 3 hr intervals for 24, 48, or 72 hr (protocol 1) or 24 hr during day 4, 5, or 6 (protocol 2). Spontaneous cardiac differentiation in sham-exposed control embryoid bodies occurred in 4.3% compared to 100% in DMSO-treated variants (positive control). However, 4 kHz modulated at 100 Hz applied for 72 hr induced differentiation in 8% of the embryoid bodies. Reverse transcription-polymerase chain reaction (RT-PCR) analysis showed no elevated α- and β-cardiac MHC-mRNA levels. 2D-electrophoresis experiments did not indicate changes in protein expression patterns. We conclude that interferential electric fields are able to induce cardiac differentiation, but only in a small subpopulation of EC P19 cells. RT-PCR analysis and 2D-electrophoresis experiments could not resolve significant differences.