HUMAN CORNEAL AND CONJUNCTIVAL EPITHELIA EXPRESS MUC1 MUCIN

Purpose. To determine if human corneal and conjunctival epithelia synt hesize MUC1 mucin, a membrane-spanning mucin present in a variety of s imple epithelia.Methods. Reverse transcription-polymerase chain reacti on (RT-PCR) was carried out to examine the expression of MUC1 mRNA by epithelial cells, using total cellular RNA prepared from cultured corn eal epithelial cells and conjunctival epithelial cells stripped from t he ocular surface with nitrocellulose filter paper Northern blot analy sis was performed to examine the transcription of MUC1 gene in culture d corneal epithelial cells. In situ hybridization histochemistry was p erformed to determine distribution of MUC1 mRNA in ocular surface epit helium. Human milk fat globule antibody (HMFG-1) and monoclonal antibo dy 139H2, which are specific for MUC1 core protein, were used in immun oblot analysis, immunohistochemistry, or both, to determine the presen ce and distribution of MUC1. Results. MUC1 mRNA was detected in cultur ed corneal and ex vivo conjunctival epithelial cells by RT-PCR Norther n blot analysis showed production of two different sizes of transcript s in the cultured corneal epithelium. Expression of MUC1 mRNA was obse rved in all layers bf corneal epithelium. By immunoblot analysis, HMFG -1 binding (>200 kd) was detected in human cultured corneal epithelium , and its binding was enhanced by neuraminidase pretreatment. Immunohi stochemically, HMFG-1 binding was observed along the apical membranes of corneal epithelium after neuraminidase pretreatment In the conjunct iva, HMFG-1 and 139H2 binding were detected in the basal region and sp oradically on the apical surface, but not in the goblet cells. Conclus ions. The stratified epithelia of the cornea and conjunctiva synthesiz e MUC1 mucin. This transmembrane mucin may have a role in tear film sp read and may prevent adhesion of foreign debris, cells, or pathogens t o the ocular surface.