Imposition of a Physiologic DC Electric Field Alters the Migratory Response of Human Keratinocytes on Extracellular Matrix Molecules

Abstract

Outwardly directed ionic currents have been measured leaving skin wounds in vivo. These currents generate physiologic electric fields of approximately 100 mV/mm, which may function to direct keratinocyte migration toward the healing wound. We investigated whether the substrate on which the keratinocyte migrates modulates the galvanotactic response to an electric migratory signal. Cultured human keratinocytes were plated on different matrices; types I and IV collagen, fibronectin, laminin, and tissue culture plastic. The effect of an applied direct current (DC) electric field on directional migration was monitored by time-lapse video microscopy over a 2-h period. Directionality was quantitated by calculating the cosine of the angle of migration in relation to anodal-cathodal orientation. Migration toward the negative pole was observed on all matrices as compared with controls (no applied field), which displayed random migration. No significant increase in directional response occurred when the field strength was increased by 100 mV/mm (physiologic levels) to 400 mV/mm. The degree of directionality and the average net cell translocation however, varied significantly with the substrate. The greatest cathodal migration in response to a DC electric field was observed with keratinocytes plated on types I and IV collagens and plastic. The directional migratory response was least on a laminin substrate, whereas cells on fibronectin demonstrated a response that was intermediate between those of collagen and laminin. These results suggest that physiologic ionic currents in concert with underlying matrix may influence the rate of reepithelialization of skin wounds.