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

ABSTRACT

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.