Power frequency fields promote cell differentiation coincident with an increase in transforming growth factor-beta(1) expression

Recent information from several laboratories suggest that power frequency f ields may stimulate cell differentiation in a number of model systems. In t his way, they may be similar to pulsed electromagnetic fields, which have b een used therapeutically. However, the effects of power frequency fields on phenotypic or genotypic expression have not been explained. This study des cribes the ability of power frequency fields to accelerate cell differentia tion in vivo and describes dose relationships in terms of both amplitude an d exposure duration. No change in proliferation or cell content were observ ed. A clear dose relationship, in terms of both amplitude and duration of e xposure, was determined with the maximal biological response occurring at 0 .1 mT and 7-9 h/day. Because this study was designed to explore biological activity at environmental exposure levels, this exposure range does not nec essarily define optimal dosing conditions from the therapeutic point of vie w. This study reports the stimulation by power frequency fields of transfor ming growth factor-beta, an important signalling cytokine known to regulate cell differentiation. The hypothesis is raised that the stimulation of reg ulatory cytokines by electromagnetic fields may be an intermediary mechanis m by which these fields have their biological activity. Bioelectromagnetics 20:453-458, 1999. (C) 1999 Wiley-Liss, Inc.