Suppression of VEGF Expression and Lesion Size in Laser-Induced CNV in a Mouse Model Overexpressing BMP-4

Abstract

Purpose: : Bone morphogenetic protein-4 (BMP-4) is a member of the transforming growth factor (TGF)-beta superfamily and plays an important role in development, eye morphogenesis and in the characteristics of the RPE. Recent reports show that BMP-4 is preferentially expressed in the adult murine RPE. Furthermore, our group found increased BMP-4 expression in RPE/choroid of dry AMD patients. The aim of this study is to determine the role of BMP-4 in the initiation, promotion and regression of choroidal neovascularization (CNV) in a mouse model overexpressing BMP-4.

Methods: : Angiogenesis was induced by use of laser-induced CNV model in BMP-4 overexpressing mice, while their littermates served as controls. Fluorescein angiography and histopathology were performed to evaluate the CNV size at 6 and 14 days after laser injury. Immunohistochemistry with anti-VEGF-A antibody was also performed to confirm VEGF expression and distribution. Posterior eye cups were used to isolate protein and mRNA for VEGF ELISA and quantitative real-time RT-PCR.

Results: : CNV size was prominently reduced in BMP-4 overexpressing mice compared to littermate controls. VEGF expression in BMP-4 overexpressing mice was significantly decreased (mean FA score: 1.2 in overexpressing mice vs 2.3 in controls) in the sensory retina compared to the controls at 6 days as evaluated by immunohistochemistry. VEGF expression in the posterior poles was upregulated during CNV formation in the littermate mice, while VEGF remained low in BMP-4 overexpressing mice by both ELISA and real-time RT-PCR analysis.

Conclusions: : Our data suggest that BMP-4 may play a role in the control of angiogenesis in retina by decreasing VEGF expression and CNV volume.

Keywords: choroid: neovascularization • transgenics/knock-outs • retinal pigment epithelium