Abstract
Purpose: :
To study the formation and maintenance of corneal epithelial vortex in normal and injured mouse eyes.
Methods: :
Gross patterns and movements of corneal epithelial cells in normal or injured mouse eyes were determined by in vivo time-lapse fluorescence microscopy, using ubiquitous GFP or RFP mice. Individual cells at the vortex were tracked in histone H2B-GFP mice twice a day over two weeks. Injury models included mechanical scraping of the epithelium, localized denervation by an incision through sclera, and illumination damage to CFP-positive nerves in Thy1-CFP mice.
Results: :
Epithelial vortex could be visualized by a corneal fluorescence pattern. Roughly a half of corneas examined exhibited an elaborate vortex that mimicked a logarithmic spiral in the apex - a degree of turns varied from about 90° to more than 360°. A sign of central vortex became apparent first at about three weeks after birth, which was one week before the onset of centripetal epithelial cell movement from the limbus. The vortex center was located slightly nasal to the geometric center, and this position was generally stable during the life of an animal. Basal epithelial cells at the vortex moved constantly along the spiral toward the center; the rate of movement appeared to decrease as they neared the center. Epithelial vortex patterns were nearly identical to those of underlying sub-epithelial nerve plexus, as determined by histology.When epithelial injuries were made to disrupt centripetal cell movement, the vortex pattern became disrupted in most instances, and a new vortex with the same orientation reappeared a few weeks later, but the location was variable. Eccentric vortexes could be generated reproducibly in 3-week old mice by scraping off the limbal epithelium; they were soon consumed by centripetal cell movement. Both surgical denervation and nerve photo-damage led to alteration or destruction of the epithelial vortex. Epithelial vortexes that re-emerged after an injury were always accompanied by corresponding sub-basal nerve vortexes. Conversely, corneas with a central corneal scar contained neither nerves nor epithelial vortex, similar to pathological corneas with defective centripetal cell movement.
Keywords: cornea: epithelium • cornea: basic science • microscopy: light/fluorescence/immunohistochemistry