Abstract
Purpose: :
Vascular adhesion protein-1 (VAP-1) is an amine oxidase that is involved in leukocyte recruitment and in the normal eye, is expressed predominantly by vascular endothelium, smooth muscle and pericytes. VAP-1 is up-regulated in animal models of ocular inflammation including endotoxin-induced uveitis, laser-induced choroidal neovascularization and diabetic retinopathy where it mediates leukocyte transmigration and participates in corneal neovascularization. The aim of this study was to investigate the expression of VAP-1 in pterygium, a disease characterized by inflammation and neovascularization of the ocular surface.
Methods: :
Immunohistochemical analysis of VAP-1 expression was performed on formalin-fixed paraffin-embedded surgical specimens of pterygia (n=24, 13 primary and 11 recurrent cases), donor matched conjunctiva (n=16, 10 primary and 6 recurrent cases) and uninflamed post-mortem human corneas (n=7). Tissue staining was graded from 0 (no staining), 1 (weak), 2 (moderate) to 3 (intense). Blood vessel staining was graded as percentage positive stained vessels from all blood vessels present in tissue sections.
Results: :
VAP-1 immunoreactivity was observed in epithelium, stromal cells and small blood vessels of pterygia and donor matched conjunctiva but with minimal staining in uninflamed post-mortem corneas. Semi-quantitative analysis of VAP-1 staining showed highest expression in pterygium epithelium, followed by donor matched conjunctiva and least in non-inflamed limbus (1.42 +/- 1.01, 0.75 +/- 0.68 and 0.14 +/- 0.38 respectively). Mean stromal VAP-1 staining was 1.38+/- 0.88 for pterygia, 0.75+/- 0.68 for conjunctiva with no staining observed in normal limbus. VAP-1 immunoreactivity was observed in 93.2% of blood vessels in pterygia, 88.2% of vessels in conjunctiva and 8.5% of vessels in normal limbus.
Conclusions: :
This study is the first to show that VAP-1 is expressed and up-regulated in pterygium implying a role for VAP-1 in its pathogenesis. Given its role in leukocyte transmigration and angiogenesis, inhibition of VAP-1 might be useful in the treatment of ocular inflammatory diseases such as pterygium.
Keywords: pterygium • neovascularization