Endogenous VEGF Is Required for Visual Function: Evidence for a Survival Role on Müller Cells and Photoreceptors

Abstract

BackgroundVascular endothelial growth factor (VEGF) is well known for its role in normal and pathologic neovascularization. However, a growing body of evidence indicates that VEGF also acts on non-vascular cells, both developmentally as well as in the adult. In light of the widespread use of systemic and intraocular anti-VEGF therapies for the treatment of angiogenesis associated with tumor growth and wet macular degeneration, systematic investigation of the role of VEGF in the adult retina is critical.Methods and FindingsUsing immunohistochemistry and Lac-Z reporter mouse lines, we report that VEGF is produced by various cells in the adult mouse retina and that VEGFR2, the primary signaling receptor, is also widely expressed, with strong expression by Müller cells and photoreceptors. Systemic neutralization of VEGF was accomplished in mice by adenoviral expression of sFlt1. After 14 days of VEGF neutralization, there was no effect on the inner and outer retina vasculature, but a significant increase in apoptosis of cells in the inner and outer nuclear layers. By four weeks, the increase in neural cell death was associated with reduced thickness of the inner and outer nuclear layers and a decline in retinal function as measured by electroretinograms. siRNA-based suppression of VEGF expression in a Müller cell line in vitro supports the existence of an autocrine role for VEGF in Müller cell survival. Similarly, the addition of exogenous VEGF to freshly isolated photoreceptor cells and outer-nuclear-layer explants demonstrated VEGF to be highly neuroprotective.ConclusionsThese results indicate an important role for endogenous VEGF in the maintenance and function of adult retina neuronal cells and indicate that anti-VEGF therapies should be administered with caution.

An essential role for RPE-derived soluble VEGF in the maintenance of the choriocapillaris

“…Immunohistochemistry, Histology, and Electron Microscopy. Whole embryos or enucleated eyes were processed and stained using previously published protocols (14) as described in the SI Materials and Methods.…”

“…The ERGs of VEGF188/188 and wt mice ERG were assessed using a UTAS-E3000 recording system (LKC Technologies) (n ϭ 4) using previously published protocols (14) as described in the SI Materials and Methods.…”

“…Systemic VEGF neutralization in mice led to a breakdown of the ventricular barrier function, and a direct role for VEGF as a survival factor for ependymal cells was indicated by their expression of VEGFR2 (10). We recently demonstrated a paracrine relationship between Müller cell-derived VEGF and VEGFR2 expressing photoreceptors in the murine retina (14). The physiologic importance of this relationship was evidenced by a significant loss of photoreceptors following systemic VEGF inhibition (11).…”

Microvascular lesions of diabetic retinopathy: clues towards understanding pathogenesis?

“…102 Although the use of VEGF-blocking agents has shown efficacy in patients with sightthreatening proliferative retinopathy, the use of such agents is controversial as they do not address the underlying vascular insufficiency and there are appropriate concerns that such therapy could compromise retinal neuroglial and functional microvascular survival. [103][104][105] There is a pressing need for phase III clinical trials of anti-VEGF strategies in the context of diabetic retinopathy.…”

Quantitative Proteomics Reveals β2 Integrin-mediated Cytoskeletal Rearrangement in Vascular Endothelial Growth Factor (VEGF)-induced Retinal Vascular Hyperpermeability

“…Thus, all these data together suggest that ␤2 integrin antibody rescued the retinal vascular hyperpermeability induced by VEGF through the cytoskeleton rearrangement and also that ␤2 integrin can serve as an effective therapeutic target for VEGF-induced retinal vascular hyperpermeability. DISCUSSION VEGF is a trophic factor for neuronal and endothelial cells in the retina, as well as a driving factor for vascular hyperpermeability (10,11,36). Thus, therapeutic targets other than VEGF have been searched to circumvent potential toxicity of anti-VEGF agents.…”