TGF-beta1, IL-1beta, and Th2 cytokines stimulate vascular endothelial growth factor production from conjunctival fibroblasts

Giant papillary formation containing newly formed vessels is a major characteristic of severe allergic conjunctivitis, such as atopic keratoconjunctivitis (AKC) or vernal keratoconjunctivitis (VKC). We examined production of vascular endothelial growth factor (VEGF) from cultured conjunctival fibroblasts from normal volunteers under stimulation with type 1-, type 2-helper T cell derived and proinflammatory cytokines to investigate the mechanism of giant papillae formation in AKC/VKC. Primary cultured conjunctival fibroblasts were incubated with interleukin (IL)-4, IL-13, IL-1beta, IL-2, tumor necrotizing factor (TNF)-alpha, interferon (IFN)-gamma, or transforming growth factor (TGF)-beta1. Effects of cytokines on VEGF protein secretion in supernatant were assessed by ELISA, and VEGF mRNA expression in cultured cells were assessed by quantitative PCR. TGF-beta1 most effectively increased VEGF concentration with dose- and time-dependent manner IL-1beta, IL-4, and IL-13 significantly increased VEGF concentration. Though IL-2 also showed slight increase of VEGF concentration, it was not statistically significant. TNF-alpha and INF-gamma did not increase VEGF concentration. Quantitative PCR showed significant increase of VEGF mRNA in TGF-beta1, IL-1beta, and IL-4 stimulated fibroblasts. TGF-beta1, IL-1beta, and Th2 cytokines from allergic inflammatory cells induced VEGF production in conjunctival fibroblasts, and may play a crucial role in neovascularization and formation of giant papillae in AKC/VKC.