Differential expression of MUC16 in human oral mucosal epithelium and cultivated epithelial sheets

Cultivated oral mucosal epithelial sheet transplantation is a new surgical strategy to treat severe ocular surface disorders such as chemical burns, ocular cicatricial pemphigoid, and Stevens-Johnson syndrome. MUC16 is thought to be the most important membrane-associated mucin on the ocular surface because it forms a protective barrier on the epithelial cell surface. In this study, we studied MUC16 expression in mRNA and protein levels and compared the expression patterns between cultivated oral mucosal epithelial cell sheet and oral mucosal tissue. Specimens (5x5 mm) of oral mucosal tissue harvested from healthy volunteers were used. The oral mucosal epithelial cells were cultured on temperature-responsive culture dishes to generate stratified cell sheets. Cultivated oral mucosal epithelial cells formed three- to five-cell thick stratified sheets for 2 weeks. Scanning electron micrographs revealed that the apical surfaces of the oral mucosal tissue and the oral mucosal sheets were covered with dense microvilli/microplicae. Real-time PCR showed significantly more MUC16 transcripts in the cultivated oral mucosal sheets and corneal epithelial sheets than in the oral mucosal tissue (P=0.023 and 0.008, respectively, Mann-Whitney rank sum test). These findings were confirmed by immunohistochemical examination using an MUC16 antibody to the protein. MUC16 protein was localized to the apical cells of the oral mucosal sheets, but the human oral mucosal tissue did not express MUC16 protein in any cell layers. In this study, interestingly, the expression of membrane-associated mucin MUC16 differs between human oral mucosal epithelia and cultivated epithelial sheets. MUC16 expressed in the oral mucosal sheets may contribute to ocular surface reconstruction after oral mucosal sheet transplantation.