Centripetal movement of corneal epithelial cells in the normal adult mouse.

PURPOSE To study the natural movement of corneal epithelial cells in the normal adult mouse with histology and in vivo microscopy. METHODS A transgenic mouse line that was engineered to ubiquitously express green fluorescent protein (GFP) was used to visualize corneal epithelial cells. For histology, epithelial GFP was imaged in a wholemounted cornea en face, and also in frozen cross-sections, under a fluorescence microscope. For in vivo studies, the anesthetized mouse was placed on a custom-made observation platform under a fluorescence microscope. Epithelial fluorescence was digitally recorded two to three times a week, and a rate of cell movement was determined from the time-lapse sequences. RESULTS The GFP expression in the corneal epithelium was nearly ubiquitous up to about 1 week after birth, and thereafter it gradually became sporadic, resulting in a mosaic pattern of GFP positive cells, with the brightest cells present in the basal and suprabasal layer of the epithelium. Both high- and low GFP-cells formed radial streaks toward the central cornea, frequently displaying vortex patterns at the center. Clusters of several high-GFP cells were tracked in living mice for up to 7 weeks, and an analysis of time-lapse sequences revealed that they moved centripetally at an average rate of 26 micro m/d. CONCLUSIONS Corneal epithelium of adult GFP mice exhibits a pattern of GFP expression that is suitable for studying cell movement in the normal cornea. Epithelial cells at the basal or suprabasal layers move centripetally in these mice at an average rate of 26 micro m/d.