Reliability and reproducibility of a rodent model of choroidal neovascularization based on the subretinal injection of polyethylene glycol

Abstract

Purpose: To evaluate the reliability and reproducibility of a rodent choroidal neovascularization (CNV) model by subretinal injection of polyethylene glycol (PEG). Methods: C57BL/6 mice were injected subretinally with 2 μl PBS (Gibco, Invitrogen, Paisley, UK; n=14) or PEG (1 mg; n=18). Animals were sacrificed at either 0, 5, 14 or 21 days. Eyes were embedded in paraffin wax and serial sections were stained with haematoxylin and eosin or Fontana-Masson or immunostained for cytokeratin 8/18, isolectin B4 (IB4), vascular endothelial growth factor (VEGF) and von Willebrand factor (vWF). Results: Both the PBS and PEG groups had retinal degeneration and retinal pigment epithelium (RPE)/choroid modifications at 5 and 14 days. Pigment clumps and cell vacuolization at the RPE/choroid were identified as melanin-containing RPE cells. In PEG-injected eyes, CK8/18-positive cellular elements were present at the subretinal space, IB4 immunoreactivity was significantly increased and choroidal vessels appeared diffusely thickened. However, neither VEGF nor vWF (angiogenesis/neovascularization markers) were detected in either group. At 21 days, the retina/choroid of PBS-injected animals was normal in appearance, while retina/choroid changes remained in some PEG-injected mice. Conclusions: Subretinal injection of PEG induced retina/choroid degenerative modifications that mimic the initial steps of human CNV. However, ocular changes were heterogeneous among animals from PBS and PEG groups and did not follow a consistent pattern while most PBS-injected animals showed similar degenerative changes. Abnormal growth of new vessels originating from the choroidal vasculature was not observed. Therefore, we consider that this model does not consistently reproduce CNV and that researchers should choose other rodent models of CNV to avoid misinterpreting their results.