Autocrine and Paracrine Secretion of Vascular Endothelial Growth Factor in the Pre-Hypoxic Diabetic Retina.

Vascular endothelial growth factor (VEGF) is well established as the main agent responsible for vascular leakage and angiogenesis in the diabetic retina. While VEGF can have positive effects on hyperglycemia stressed retinal tissues, it also plays a role in events progressing to the oxygen- stressed, i.e. hypoxic, diabetic retina. Some VEGF makes its way to the retina from systemic sources and some is produced locally within the eye. Hyperglycemia, oxidants, inflammation, and advanced glycation end-products are all stimulants to VEGF production, both in the hypoxic and the pre-hypoxic retina. Endothelial cells, pericytes, Müller cells, microglia, astrocytes, retinal pigment epithelium and neurons have all been known to produce VEGF at some point in retinal development or in disease. Excessive VEGF production in the early diabetic retina can lead to retinal exposure or mechanisms which exacerbate further damage. While Müller cells are likely the most significant producer of VEGF in the pre-hypoxic retina, other VEGF producing cells may also play a role due to their proximity to vessels or neurons. Study of the release of VEGF by retinal cells in hyperglycemia conditions, may help identify targets for early treatment and prevent the serious consequences of diabetic retinopathy.