Abstract
Purpose:
Recently we showed that targeted AAV-decorin gene therapy significantly inhibits corneal angiogenesis in vivo in rabbits. This study tested the hypothesis that decorin’s anti-angiogenic effects in the cornea are mediated via the restoration of normal physiologic balance between the pro- and anti-angiogenic cytokines, VEGFR modulation, and VEGFR-mediated ERK signaling.
Methods:
New Zealand white rabbits and human corneal fibroblast (HCF) cultures were used. The HCF cellular lysates treated with decorin (250nM) +/- VEGF (50ng/ml) were used for time dependent analysis of vascular endothelial growth factor receptor (VEGFR), VEGFR1 and VEGFR2 phosphorylation using proteome human receptor tyrosine kinases (RTKs) array analysis. Corneal neovascularization in rabbits was produced with VEGF-implant micro-pocket assay. Quantitative real-time qPCR, immunohistochemistry and fluorescence confocal microscopy analyzed pro-/anti-angiogenic cytokines (VEGF, MCP1, angiopoietin, PEDF etc.), VEGFR mRNA/protein expression, and VEGFR-mediated ERK1/2 signaling in AAV-decorin-transduced, AAV-gfp-transduced neovascularized, and naive rabbit corneas.
Results:
VEGF treatment caused phosphorylation of VEGFR in HCF as detected by RTK array assay. Detection of no VEGFR phosphorylation in HCF incubated with VEGF+decorin suggests that decorin abrogated VEGF-induced phosphorylation of VEGFR in corneal fibroblasts. Decorin also inhibited VEGFR phosphorylation in vivo as revealed by a marked decrease in ERK1/2 phosphorylation in AAV-decorin-delivered neovascularized rabbit corneal sections. Additionally, AAV-decorin gene delivery rescue normal physiologic balance between pro- and anti-angiogenic factors by down-regulating VEGF, MCP1 (mRNA 3-5 fold p< 0.05 and protein 11-27%, p<0.01) and up-regulating PEDF (mRNA 1.8-2.5 fold p<0.05 and protein 9-13%, p<0.01) in neovascularized rabbit corneas. The results of other signaling studies are pending.
Conclusions:
Decorin inhibits corneal angiogenesis largely by interrupting VEGF signaling, and restoring the pro- and anti-angiogenic factors balance required for corneal transparency.
Keywords: 480 cornea: basic science •
484 cornea: stroma and keratocytes •
538 gene transfer/gene therapy