Monophasic and biphasic electrical stimulation induces a precardiac differentiation in progenitor cells isolated from human heart.

Electrical stimulation (ES) of cells has been shown to induce a variety of responses, such as cytoskeleton rearrangements, migration, proliferation and differentiation. Herein we have investigated whether mono and biphasic pulsed ES could exert any effect on the proliferation and differentiation of cardiac progenitor cells (hCPCs) isolated from human heart fragments. Cells were cultured under continuous exposure to mono or biphasic ES with fixed cycles for 1 or 3 days. Results indicate that neither stimulation protocol affected cell viability, while cell shape became more elongated and re-oriented more perpendicular to the electric field direction. Moreover, the biphasic ES clearly induced the up-regulation of early cardiac transcription factors MEF2D, GATA-4 and Nkx2.5, as well as the de novo expression of the late cardiac sarcomeric proteins troponin T, cardiac alpha actinin and SERCA 2a. Both treatments increased the expression of connexin 43 and its relocation to the cell membrane; but biphasic ES was faster and more effective. Finally, when hCPCs were exposed to both mono and biphasic ES, they expressed de novo the mRNA of the voltage-dependent calcium channel Cav 3.1(1G) subunit, which is peculiar of the developing heart. Taken together, these results show that ES alone is able to set the conditions for early differentiation of adult hCPCs towards a cardiac phenotype.