Role of Insulin-Like Growth Factor Binding Protein-3 in the Pathogenesis of Herpes Stromal Keratitis

PURPOSE: The goal of this study was to determine the role of insulin-like growth factor-binding protein-3 (IGFBP-3) in the pathogenesis of herpes stromal keratitis (HSK). METHODS: In an unbiased approach, a membrane-based protein array was carried out to determine the level of expression of pro- and anti-angiogenic molecules in uninfected and HSV-1 infected corneas. Quantitative RT-PCR and ELISA assays were performed to measure the amounts of IGFBP-3 at mRNA and protein levels. Confocal microscopy documented the localization of IGFBP-3 in uninfected and infected corneal tissue. Flow cytometry assay showed the frequency of immune cell types in infected corneas from C57BL/6J (B6) and IGFBP-3 knockout (IGFBP-3(−/−)) mice. Slit-lamp microscopy was used to quantitate the development of opacity and neovascularization in infected corneas from both groups of mice. RESULTS: Quantitation of protein array dot blot showed an increased level of IGFBP-3 protein in HSV-1 infected than uninfected corneas and was confirmed with ELISA and quantitative RT-PCR assays. Cytosolic and nuclear localization of IGFBP-3 were detected in the cells of corneal epithelium, whereas scattered IGFBP-3 staining was evident in the stroma of HSK developing corneas. Increased opacity and hemangiogenesis were noted in the corneas of IGFBP-3(−/−) than B6 mice during the clinical period of HSK. Furthermore, an increased number of leukocytes comprising of neutrophils and CD4 T cells were found in HSK developing corneas of IGFBP-3(−/−) than B6 mice. CONCLUSIONS: Our data showed that lack of IGFBP-3 exacerbates HSK, suggesting the protective effect of IGFBP-3 protein in regulating the severity of HSK.