VEGF protein and its receptor proteins in pterygia: Immunhistochemical localization and Western blot analysis
M. Schellenbeck1, N. Anders1, J. S. Jürgensen2, C. Hartmann1, H. Baatz1
Introduction: Vascular endothelial growth factor (VEGF) is an endothelial cell-specific angiogenic factor that has been implicated in the pathogenesis of various ocular neovascular disorders. As pterygium is considered to be a fibrovascular disorder, this study was designed to investigate whether VEGF protein and its tyrosine kinase receptor proteins flk-1 and flt-1 are detectable in pterygium specimens and normal conjunctival tissue samples.
Methods: VEGF expression was identified by Western blotting with anti- VEGF antibody (Ab, RD Inc.) using frozen tissue samples of primary pterygia and bulbar conjunctiva as controls. Tissue sections of fifteen primary pterygia of thirteen patients and seven normal conjunctival specimens of age-matched controls were examined using a VEGF mouse monoclonal Ab, flk-1 mouse monoclonal Ab and flt-1 goat polyclonal Ab (Santa Cruz Biotechnology Inc.)
Results: Western blot analysis of the primary pterygia lysates incubated with VEGF antibody revealed VEGF expression. Immunohistological examination showed positive staining of VEGF in pterygium tissue samples with intense staining of VEGF in the basal cells of the epithelium and moderate to discrete staining in the cell layers closer to the surface. VEGF protein was located in the cytoplasma as well as on cell surfaces. Moreover, tissue sections of pterygia showed intense staining of flk-1 and flt-1 in the basal layers of the epithelium and weak staining in superficial cell layers. Flk-1 and flt-1 antibody showed membrane staining. Immunolabeling in normal conjunctiva showed no reactivity to VEGF, flk-1 and flt-1. Negative controls did not result in any staining of pterygia or normal conjunctiva.
Conclusion: Our studies show that VEGF and its receptors are detectable in pterygium. The data suggests a role for VEGF in pterygium formation, supporting the concept of a fibrovascular growth disorder rather than a degeneration in the pathogenesis of pterygium. Specific anti-angiogenic substances may provide a therapeutic alternative to surgical pterygium management in the future.
1Eye-Hospital and 2Dept. of Nephrology, Charité, Humboldt University, Augustenburger Platz 1, D-13353 Berlin