Abstract
Abstract: :
Purpose: To evaluate the expression of inflammatory cytokines and matrix metalloproteinases in the corneal epithelium in chronic corneal edema. Methods: Tissue sections were prepared from paraffin fixed blocks of corneal buttons removed during penetrating keratoplasty from 20 patients who had pseudophakic bullous keratopathy (PBK). Tissue sections from 10 age–matched eyes enucleated because of uveal melanoma served as controls. Expression of Interleukin (IL)–1, IL–6, IL–8, vascular endothelial growth factor (VEGF), matrix metalloproteinase (MMP)–1, MMP–3 and MMP–9 in the corneal epithelium was evaluated by immuno– histochemistry using mouse anti–human monoclonal antibodies for these proteins. Digital image analysis using ImagePro–Plus software (Media Cybernetics, Silver Springs, MD) was performed to quantify the expression of the various cytokines and MMPs. A mean intensity stain index (ISI), based on the staining density and the area stained, was calculated from digital images captured from sequential areas of microscopic sections in each coverslip. The mean ISI of sections from patients with PBK was compared to that of controls for each cytokine or MMP tested, using Mann–Whitney’s test. Results: The expression of most of the inflammatory cytokines and MMPs was significantly higher in the corneal epithelium of PBK corneal buttons compared to controls. MMP–9 had the highest difference in expression when compared to controls (ISI score 28.58 ± 18.26 in PBK compared to 0.087 ± 0.21 in controls, p<0.0001). Significantly higher intensity scores compared to controls were also recorded for MMP–1 (8.2 ± 6.5 vs. 0.09 ± 0.17, p=0.0003), IL–1 (47.06 ± 5.97 vs. 17.96 ± 7.55, p=0.0007), IL–8 (24.99 ± 15.3 vs. 0.54 ± 0.38, p=0.02) and VEGF (50.38 ± 15.38 vs. 22.1 ± 12.1, p=0.0001). The expression of MMP–3 and IL–6 in PBK was not significantly higher than controls. Conclusions: The corneal epithelium in PBK expresses high levels of cytokines and enzymes, which are associated with inflammation, angiogenesis and tissue degradation. These agents may augment the corneal edema and epithelial damage clinically observed in PBK, and may persist in the remaining host tissue after penetrating keratoplasty.
Keywords: cornea: epithelium • cytokines/chemokines • immunohistochemistry