Corneal Epithelium Can Migrate to Cover Conjunctival Defect

Abstract

Purpose: : Limbus is a barrier that separates corneal epithelium from conjunctival epithelium. Conjunctival epithelium never migrates across the limbal barrier and contributes to the healing of corneal epithelium defects and vice versa when limbus remains its integrity. It has not been studied whether corneal epithelium may participate in the healing of conjunctiva defects. In present studies, we examined the role of conjunctival epithelium on cornea and corneal epithelium on conjunctiva wound healing in the absence of limbal barrier.

Methods: : Corneal epithelial debridement involving-various degrees, whole, ¾, ½ ¼ limbal deficiency, and conjunctival excision were respectively performed with Krt12^Cre/wt/ZEG mice in which corneal epithelial cells that expressed Krt12^Cre allele were green fluorescence positive. Following the surgeries, ocular surface healing was observed using a ZEISS fluorescent stereomicroscopy. Immunostaining with anti-K12 was employed to distinguish the cell phenotypes of ocular surface.

Results: : Corneal epithelium adult Krt12^Cre/wt/ZEG mice displayed strong spiral green fluorescence. Simple corneal epithelial debridement with intact limbus healed quickly with identical spiral green fluorescence prior to debridement. In contrast, corneal epithelial debridement involving limbal defects led to the loss of original spiral green fluorescence. Injuries involving entire and ¾ limbal defects the denuded corneal surfaces were covered by conjunctival epithelium as evidenced by the presence of goblet cells. Surprisingly, conjunctival excision was healed by green fluorescent corneal epithelium which migrated across the region of conjunctival defect. Immunostaining with anti-K12 antibodies revealed that the green fluorescent cells overlaying sclera expressed K12 albeit many of green positive cells had much weaker red-fluorescent signals after two weeks of surgery.

Conclusions: : Removal of limbus barrier allows the migration of corneal epithelium onto denuded sclera surface and participates in the healing of conjunctiva defects, and vice versa. It remains to be shown whether the corneal epithelial cells overlaying conjunctiva may undergo transdifferentiation and assume conjunctival phenotype, e.g., expression of Keratin 4, mucin.

Keywords: cornea: epithelium • conjunctiva • wound healing