Evidence for heterogeneity in a small squamous cell type ('light' cells) in the rabbit corneal epithelium--a scanning...

The rabbit corneal epithelial surface, as viewed by scanning electron microscopy (SEM), is composed of a mosaic of polygonal cells with different appearances (light, medium and dark) with the lighter cells having a characteristically high density of microplicae. From the central zone of the corneal epithelial surface of 16 female New Zealand White rabbits (2 kg), the lighter-appearing cells had an average area of 108 +/- 47 microns2 (n = 567, +/-SD). A subgroup of atypical lighter cells had an average area of 294 +/- 67 microns2 (n = 53) compared to typical light cells of 88 +/- 12 microns (n = 514). These atypical lighter cells had fused microplicae at their periphery (instead of a uniform arrangement of densely packed microplicae), tended to be rounder in shape (as opposed to being angular), could show signs of desquamation and were not decorated with the epithelial craters found on almost all (92%) other light cells. All of these features are suggestive of these atypical lighter cells being the terminal phenotype of the light cells just prior to desquamation from the ocular surface. The observation of the desquamation of lighter cells supports a hypothesis that they constitute a distinct sub-population of cells at the corneal epithelial surface.