Overexpression of VEGF-A induces neovascularization and increased vascular leakage in rabbit eye after intravitreal adenoviral gene transfer

Aims: The aim of this study was to determine dose–response effects of vascular endothelial growth factor A as delivered using an adenoviral vector on vascular growth and pathological changes in the rabbit eye. Moreover, we wanted to develop a large animal model for angioproliferative diseases in the eye. Methods: Seventeen New Zealand White rabbits were injected with adenoviral vascular endothelial growth factor‐A (AdVEGF‐A) intravitreally with different doses (10⁹–10¹¹ vp). Controls were injected with an empty virus (AdCMV). Some animals had a combination of AdVEGF‐A and AdsKDR (a soluble form of the VEGF receptor‐2). Animals were killed 6 days after the gene transfer. On the basis of these results, 14 rabbits were injected intravitreally with AdVEGF‐A or adenoviral LacZ (AdLacZ) with 10¹⁰ vp in a volume of 0.1 mL. Animals were killed 3, 6, 14 and 28 days after the gene transfer, eyes were removed and analysed histologically. Results: In enzyme‐linked immunosorbent assay (ELISA) analysis, human VEGF‐A was present in vitreous humour in all VEGF‐A transduced eyes. The amount of VEGF‐A showed a dose‐dependent increase with the AdVEGF‐A dose and was the highest 6 days after the gene transfer. Histologic analyses revealed an increased capillary area and density in the AdVEGF‐A eyes when compared with the AdLacZ eyes (P < 0.05). In the AdVEGF‐A/AdsKDR eyes the average capillary area was not increased compared with AdLacZ eyes. Conclusion: This model could be useful for large animal studies regarding the pathogenesis of neoangiogenesis and for the development of new therapeutic strategies for angioproliferative diseases of the eye. Our results establish the key role of VEGF‐A in the induction of neovascularization and pathological changes in the rabbit eye.