Role of Oncostatin M in the Pathogenesis of Vernal Keratoconjunctivitis: Focus on the Barrier Function of the Epithelium and Interleukin-33 Production by Fibroblasts.

PURPOSE: Vernal keratoconjunctivitis (VKC) is a severe, recurrent allergic conjunctivitis. Previously, we found high concentrations of oncostatin M (OSM) in the tears of patients with VKC. Here, we investigated the role of OSM in VKC by focusing on epithelial barrier function and IL-33 production.

METHODS: To assess the effect of OSM on the barrier function of human conjunctival epithelial cells (HConEpiCs), we measured transepithelial electrical resistance and dextran permeability. We also assessed expression of tight junction-related proteins such as E-cadherin and ZO-1 in HConEpiCs by Western blotting and immunofluorescence. Then we used immunohistochemistry to evaluate expression of Ki-67, E-cadherin, epithelial-mesenchymal transition-related proteins, and IL-33 in giant papillae (GPs) from patients with VKC. In addition, we used Western blotting, microarray, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay to examine whether OSM activates signal transducer and activator of transcription 1 (STAT1) or STAT3 and induces the expression of various genes in human conjunctival fibroblasts (HConFs).

RESULTS: OSM reduced expression of E-cadherin and ZO-1 in HConEpiCs, indicating barrier dysfunction. In immunohistochemistry, Ki-67 expression was present in the lower epithelial layer of the GPs, and E-cadherin expression was reduced in the superficial and lower layers; double staining revealed that GPs had a high number of fibroblasts expressing IL-33. In addition, in HConFs, OSM phosphorylated both STAT1 and STAT3 and induced IL-33.

CONCLUSIONS: OSM has important roles in severe, prolonged allergic inflammation by inducing epithelial barrier dysfunction and IL-33 production by conjunctival fibroblasts.