CONJUNCTIVAL EPITHELIAL-CELLS CAN RESURFACE DENUDED CORNEA, BUT DO NOT TRANSDIFFERENTIATE TO EXPRESS CORNEA-SPECIFIC KERATIN-12 FOLLOWING REMOVAL OF LIMBAL EPITHELIUM IN MOUSE

Limbal stem cell deficiency contributes to recurrent corneal epithelia l defects. We examined whether the conjunctival epithelium can transdi fferentiate to corneal epithelium following surgically induced limbal stem cell deficiency. Mice were anesthetized by intraperitoneal inject ion of sodium pentobarbital. Partial or total epithelial removal was p roduced with a no. 69 Beaver blade under a dissecting microscope. The wounds were allowed to heal for 0-28 days, and the mice were examined every other day to evaluate re-epithelialization. Corneas were then su bjected to histological, immunohistochemical studies and Western blot analysis with epitope-specific anti-keratin 12 antibodies. Partial epi thelial defects re-epithelialized within 2 days and were normal in app earance and expressed cornea-specific keratin 12. In eyes with limbal deficiency, re-epithelialization progressed more slowly and was charac terized by opacification; epithelial closure usually occurred by the 7 th day. This epithelium differed from normal corneal epithelium in bas ic morphology, cell shape, and the presence of goblet cells at 2 weeks after injury. The epithelium at the center of injured corneas with to tal defect at 4 weeks had cornealike morphology and was devoid of gobl et cells. These epithelial cells derived from conjunctiva did not expr ess the cornea-specific keratin 12, as determined by immunohistochemis try, Western blot analysis and in situ hybridization. As evidenced by differences in morphology and the expression of cornea-specific kerati n 12, conjunctival transdifferentiation does not occur in conjunctical overgrowth after the removal of limbal epithelium.