M. Zhao et al., DIRECTED MIGRATION OF CORNEAL EPITHELIAL SHEETS IN PHYSIOLOGICAL ELECTRIC-FIELDS, Investigative ophthalmology & visual science, 37(13), 1996, pp. 2548-2558
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.