Selective Cre/lox Flt-1 Ablation In RPE Induces CNV: A Novel Transgenic Murine CNV Model

Abstract

Purpose: : To determine whether CNV is developed spontaneously without injury by conditional ablation of VEGF receptor-1 (Flt-1) in the RPE.

Methods: : We interbred the transgenic Vmd₂-cre mice, which express Cre recombinase specifically in the RPE cells with floxed Flt-1 mice. At 21days to 3 months after born, the fundi were observed in vivo by fluorescein angiography (FA) and indocyanine green (ICG) angiography using the Heidelberg Retina Angiograph. Histology was performed by hematoxylin and eosin (H&E) stainining and Transmission electron microscope (TEM). The soluble Flt-1 or Cre or VEGF expression was analyzed by immunohisochemistry (IHC) or stainining and in situ hybridization or Western blotting.

Results: : At 21days to 3 months of age, all homozygous RPE-specific Flt-1 knockout mice (Cre⁺ flt-1^lox/lox) (18/22 eyes, 82%, P=1.3E-6), and about half of the hemizygous conditional Flt-1 knockout mice (Cre⁺ flt-1^lox/+) (17/42 eyes, 40%, P=0.009) developed CNV, which progressed over time, compared with 18% (2/22 eyes, 9%) of littermate controls (Cre⁺ flt-1^+/+). We further confirmed that soluble FLT-1 was down-regulated by IHC staining and in situ hybridization, while VEGF-A was up-regulated by western blotting, in conditional Flt-1 Knockout mice, compared with littermate controls.

Conclusions: : FLT-1 (soluble FLT-1) knockdown in the RPE by selective Cre/lox FLT-1 ablation can induce CNV in the early stage. The transgenic mice were developed in this study could be used as a novel murine CNV model.

Keywords: choroid: neovascularization • vascular endothelial growth factor