Model of epithelial downgrowth: II. Scanning and transmission electron microscopy of corneal epithelialization.

We present a cat model of prolific epithelial downgrowth reviewing the scanning and transmission electron microscopy data. The cat model of posterior corneal epithelialization closely mimics the human clinical condition in the following areas: uneven epithelial spread over the endothelial surface on scanning electron microscopy, prominence of intercellular desmosomes and hemidesmosomes, and attachment of the latter to a basement membrane overlying a newly formed posterior collagenous layer. Cell layering is attenuated during the centripetal spread of cells down the center of the cornea. Adjacent endothelial cells show signs of cytotoxicity by increased microvilli and eventual plasma membrane retraction. Endothelial cells are covered by the advancing epithelium with subsequent endothelial cell death. The density of subepithelial collagen attachments would suggest that removal of Descemet's membrane would be required to guarantee total epithelial cell removal.