Eyelid opening induces expression of a glycocalyx glycoprotein of rat ocular surface epithelium.

PURPOSE We previously characterized a monoclonal antibody against a glycoprotein of rat ocular surface glycocalyx (ROSG). This monoclonal antibody recognizes a carbohydrate epitope on a glycoprotein expressed in apical cells of the differentiated ocular surface epithelium. Our goal was to determine the developmental appearance of the ROSG glycoprotein. METHODS We localized the antigen immunohistochemically and immunocytochemically in newborn (day 1) rats and in rats 2-5, 7, and 11-15 days after birth. RESULTS Before eyelid opening (days 12-14), the ROSG antigen was localized in the palpebral conjunctiva near the lid margin. The binding extended to layers of the subapical flattened cells. However, the antigen was not found in the corneal epithelium while the eyelid remained closed. In contrast, at the first day of eyelid opening (days 12-15), the antigen was present contiguously in several cell layers from the eyelid margin along the entire ocular surface, including the corneal epithelium. Thus, the binding pattern seen upon eyelid opening was similar to that of adult rats. The phenomenon of appearance of the glycoprotein upon eyelid opening was further demonstrated in rats with asynchronous eyelid opening. Artificial, premature eyelid opening at days 8-11 also induced the expression of the antigen along the entire ocular surface epithelium, similar to the binding in naturally opened eyes. CONCLUSION Eyelid opening may induce glycosylation or expression of a glycocalyx component that we hypothesize to be involved in mucin spread.