Immunohistochemical profile of VEGF, TGF-β and PGE₂ in human pterygium and normal conjunctiva: experimental study and review of the literature

Human pterygium is made up of chronic proliferative fibro-vascular tissue growing on the ocular surface. This disease exhibits both degenerative and hyperplastic properties. Some fibroangiogenic factors have recently been shown to play a potential role in fibrovascular diseases via the angiogenesis process. The aim of this study is to evaluate VEGF, TGF-β and PGE₂ expression in the epithelial, endothelial and stromal cells of human pterygium and normal conjunctiva in order to determine whether these factors participate in the development of pterygium. Ten specimens from patients with pterygium and two normal conjunctivas (cadavers) were analyzed by immunohistochemistry using specific antibodies against these growth factors. The technique used was ABC/HRP (Avidin complexed with biotinylated peroxidase). Immunoreactivity of VEGF was significantly increased in the epithelium, vascular endothelium and stromal cells in primary pterygium as compared with normal conjunctiva. A moderate expression of TGF-β in the pterygium was observed in the epithelial and stromal layers. On the contrary, immunolabeling of this growth factor in the human normal conjunctiva was weak. PGE₂ was strongly expressed in the epithelium of patients with pterygium, as in control conjunctival tissues, and the immunolabeling was moderate in the stroma from the same patients. Our results suggest that these growth factors may contribute to the progression of primary pterygium by increasing angiogenesis, thus leading to the formation of new blood vessels from the pre-existing vasculature. We conclude that VEGF, TGF-β and PGE₂ may be potential therapeutic targets in the treatment of this disease although proof of this evidence requires further studies.