Limbal epithelial crypt: a model for corneal epithelial maintenance and novel limbal regional variations.

OBJECTIVE To determine the distribution of cell membrane proteins and extracellular matrix proteins around the limbal epithelial crypt (LEC) compared with adjacent limbus and corneal epithelium. METHODS Serial histological sections of human corneoscleral limbus rims were stained with antibodies of interest by standard immunohistochemistry. RESULTS Superficial cells of the limbus were desmoglein 3 positive, compared with the negative basal cells of the limbus that correspond to cells with more stemlike properties. The LEC had a much lower proportion of desmoglein 3 staining in comparison. Tenascin C staining demonstrated regional variations of the limbus depending on their association with the LEC. Limbus that was associated with or adjacent to the LEC had a greater tenascin C expression compared with normal limbus, whereas the LEC demonstrated the greatest tenascin C expression. CONCLUSIONS Based on these and similar results previously reported for connexin 43, we propose a novel model on the mechanism of corneal surface epithelium maintenance involving 3 different limbal regions: zone 1, limbus including the LEC; zone 2, limbus associated with the LEC; and zone 3, limbus distant to the LEC. CLINICAL RELEVANCE The noted limbal variations may influence the selection of the donor site for limbal grafts in the future.