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Shan Liu, Alexander Viktor Tschulakow, Sylvie Julien-Schraermeyer, Ulrich Schraermeyer, Antje Kristina Biesemeier; A valid ultrastructural rat choroidal neovascularization model developed by overexpression of VEGF. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2269.
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© ARVO (1962-2015); The Authors (2016-present)
Vascular endothelial growth factor (VEGF) promotes choroidal neovascularization (CNV), an important component of subsequent vision loss in age related macular degeneration (AMD). Our aims were to develop a new efficient and reliable CNV model induced by overexpression of VEGF, to test its effects on extracellular matrix formation and use the model to facilitate the study of antiangiogenic and antiproliferative therapies for ocular diseases.
We developed a CNV model by subretinal injection of a high-capacity adenovirus vector encoding for human VEGF-A165 (HC Ad.VEGF) into 8 rats (Long Evans). Two rats injected with HC Ad.EGFP and five untreated rats were used as controls. Scanning laser ophthalmoscopy (SLO), fluorescein angiography (FA), indocyanine green angiography (ICG) and optical coherence tomography (OCT) were performed in all rats at postoperative 2 and 4 weeks. The eyes were excised 4 weeks after the injection and fixed for paraffin and EPON embedding. Sections were observed by light and electron microscopy (EM). HE staining and immunohistochemistry (IHC) were performed. Masson trichrome staining showed the distribution of extracellular matrix components (collagen, elastin and fibrin). Loss of retinal pigment epithelium (RPE) and choriocapillaris (CC) was tested by t-test (significance level: P=0.05).
The hyperfluorescent areas, shown in FA and ICG of 81.25% of the VEGF treated eyes, were possibly caused by alterations or leakages of the CC. OCT showed a marked subretinal edema-like change in most eyes. In the EM, we found newly formed blood vessels with perivascular cells and fenestrations between Bruch’s membrane (BM) and RPE or between RPE cells, multi-layered RPE, loss of photoreceptors, loss of RPE and CC compared with controls (P<0.05), thickened BM and collagen accumulation in CNV areas, resembling human CNV. We are not able to confirm the existence of leakage in the model, because of the lack of fibrin around newly formed blood vessels. IHC verified human VEGF expression, high proliferation (Ki67), occurrence of pericytes (alpha SMA) and absence of macrophages (CD68) in CNV areas.
Based on the results of examinations, especially EM, this rat model resembles human CNV. Running experiments using additional angiopoietin1, 2 and PDGF-B vectors will provide a tool to modulate CNV severity and might yield new therapeutic options for the future.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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