Inhibitory Effect of an Antibody to Cryptic Collagen Type IV Epitopes on Choroidal Neovascularization

Abstract

Abstract: : Purpose: Cryptic extracellular matrix epitopes are specifically exposed, and play a functional role during angiogenic processes such as tumor growth and retinal neovascularization. We tested the effect of a humanized antibody directed to a cryptic collagen type IV epitope (H8; original Ab termed HUIV26) in a murine model of choroidal neovascularization (CNV). Methods: To induce experimental CNV, adult C57BL/6 mice were anesthetized and treated with a Diode laser to rupture Bruch's membrane. Subsequently, mice were treated with daily intraperitoneal injections of 10mg/kg of H8 (Cell–Matrix, Inc.) or an isotype–matched control antibody. After 2 weeks, the eyes were enucleated, and choroidal flatmounts were prepared. Areas of CNV were measured by fluorescence microscopy following immunostaining of PECAM to identify vessels. The expression of collagen type IV and exposure of the cryptic epitope after laser injury were assessed by immunostaining. Results: The presence of collagen type IV and the cryptic epitope were observed at the site of laser burn. The intensity and area of staining for H8 were maximal at 5 days post laser burn and extended beyond the area of neovascularization. At 14 days post injury, H8 staining appeared reduced, colocalized with the area of CNV, and was nearly absent from the underlying choroidal vessels. Mice treated with 10mg/kg H8 had significantly smaller CNV than control–treated mice. Conclusions: Results suggest that exposure of a cryptic collagen type IV epitope is associated with the incidence of CNV and that humanized antibody H8 may provide an new effective treatment for CNV.

Keywords: choroid: neovascularization • extracellular matrix • drug toxicity/drug effects