Interaction Between Conjunctival Epithelial Cells and Mast Cells Induces CCL2 Expression and Piecemeal Degranulation in Mast Cells

PURPOSE: Intraepithelial mast cells are observed in giant papillae tissue samples obtained from patients with atopic keratoconjunctivitis (AKC)/vernal keratoconjunctivitis (VKC). We examined the roles of interaction between the conjunctival epithelial cells and mast cells. METHODS: The interaction between human mast cells and conjunctival epithelial cells (HCjE) was investigated using a coculture model. Protein array analysis, ELISA, and real-time PCR were performed to test the interaction. Tissue samples (n = 6) from giant papillae were resected for therapeutic purposes, and subjected to immunohistological analysis of CCL2 expression. Recombinant CCL2 (10 ng/mL) was reacted with the cultured human mast cells and ultrastructural analysis was performed. A ragweed (RW)-induced mouse experimental allergic conjunctivitis model was used to examine ccl2 mRNA expression and mast cell morphology. RESULTS: Protein array and real-time PCR analyses showed that CCL2 protein/mRNA expression was induced by mast cell-HCjE coculture. Upregulation of CCL2 mRNA was observed in mast cells, whereas in situ CCL2 expression was observed at the conjunctival epithelium of the giant papillae by immunohistochemistry. Ultrastructural analysis showed that recombinant CCL2 treatment induced piecemeal degranulation (PMD) in the mast cells. Ultrastructural analysis of tissues from the giant papillae showed PMD of mast cells within the conjunctival epithelial cells. The RW-induced experimental allergic conjunctivitis model showed increased ccl2 mRNA expression and PMD morphology in the conjunctivae. CONCLUSIONS: Mast cell-conjunctival epithelial cell interaction induces CCL2 expression and subsequent PMD.