Corneal epithelial wound healing in the absence of limbal epithelium.

Corneal epithelial stem cells are thought to be at the limbus. The limbal epithelium was surgically removed in 12 New Zealand white rabbits. After 6 months, four showed mild vascularization. To challenge the remaining proliferative reserve, two consecutive 7.5-mm epithelial woundings were created 3 weeks apart in 11 limbal-deficient corneas and 11 controls. After the first wounding, five of the limbal-deficient corneas showed delayed healing, and seven became moderately vascularized; the controls healed normally. After the second wounding, eight experimental corneas showed intense vascularization; the controls did not. Recurrent erosions with delays in healing were noted in nine experimental animals but not in controls. Flat-mount preparation and impression cytology revealed centripetal migration of conjunctival epithelium with goblet cells onto the experimental corneas. These results indicate that only limited proliferative capacity of corneal epithelium remains in the absence of limbus. The constellation of delayed healing with recurrent erosion, corneal vascularization, and conjunctival epithelial ingrowth can be considered possible signs of limbal stem cell dysfunction.