Orientation and directed migration of cultured corneal epithelial cells in small electric fields are serum dependent

Abstract

Reorientation and migration of cultured bovine corneal epithelial cells (CECs) in an electric field were studied. Electric field application was designed to model the laterally directed, steady direct current electric fields which arise in an injured corneal epithelium. Single cells cultured in media containing 10% foetal bovine serum showed significant galvanotropism, reorienting to lie perpendicular to electric field vector with a threshold field strength of less than 100 mV/mm. Cells cultured in serum-free medium showed no reorientation until 250 mV/mm. Addition of EGF, bFGF or TGF-beta 1 singly or in combination to serum free medium significantly restored the reorientation response at low field strengths. Both the mean translocation rate and directedness of cell migration were serum dependent. Cultured in medium with serum or serum plus added EGF, single cells showed obvious cathodal migration at 100 mV/mm. Increasing electric field strength enhanced the cathodal directedness of single cell migration. Supplementing serum free medium with growth factors restored the cathodal directed migration of single cells and highest directedness was found for the combination of EGF and TGF-beta 1. Corneal epithelial sheets also migrated towards the cathode in electric fields. Serum or individual growth factors stimulated CEC motility (randomly directed). Applied fields did not further augment migration rates but added a vector to stimulated migration. Electric fields which are present in wounded cornea interact with other environmental factors and may impinge on CECs migration during wound healing. Therapies which combine the application of growth factors and electric fields may be useful clinically.