DIRECTED MIGRATION OF CORNEAL EPITHELIAL SHEETS IN PHYSIOLOGICAL ELECTRIC-FIELDS

Purpose. To characterize the effects of small applied electric fields (EFs) (100 to 250 mV/mm) on cultured bovine corneal epithelial cell (C EC) sheets and to determine how EFs interact with other environmental cues in directing CEC sheet migration. Methods. Primary cultures of bo vine CECs were exposed to EFs in medium with or without serum, epithel ial growth factor, basic fibroblast growth factor, or transforming gro wth factor-beta 1 Cell sheet migration was traced using an image analy zer. Results, Cell sheets migrated toward the cathode (negative pole). The directional migration was voltage dependent, and, at low field st rength (up to 200 mV/mm), it required serum in the medium. Sheets show ed no migration responses up to 200 mV/mm in serum-free medium, wherea s those in medium with serum showed evident migration toward the catho de, at an average rate of approximately 15 mu m/h (n=15 similar to 20) at 150 mV/mm. When serum was present, the threshold was below 100 mV/ mm, very close to the measured wound field strength (similar to 42 mV/ mm). After supplementing serum-free medium with individual growth fact ors or with combinations of epithelial growth factor, basic fibroblast growth factor, and transforming growth factor-beta 1, significant res toration of cathode-directed migration occurred at 150 mV/mm. Lamellip odia were abundant at the leading edges of migrating sheets, extending the area of sheets covered. The extension of cell membranes toward th e cathode was more prominent in cell sheets than in single cells. Conc lusions. The endogenous EFs generated by wounded cornea could play an important role by interacting with other environmental factors to prom ote changes in shape and in directed migration of CEC sheets.