VEGF expression in the avascular retina

Purpose. To characterize the expression patterns of VEGF in chicken retinal cells and tissues, a species that develops an avascular retina. Methods. Semi quantitative RT/PGR and western blotting were used to measure the expression of VEGF protein and mRNA in developing chick retinal tissue and primary chick retinal cells cultured under normoxic or hypoxic conditions. Results. Duri ig development of the chick retina a physiological hypoxia occurs just as it does in the rat, cat and other mammalian retinas. VEGF protein expression is increased in the chick retina during this developmental period, yet vasculogenesis of the tissue is not initiated. Furthermore, primary chick retinal cells up-regulate levels of VEGF mRNA several fold after culture in a hypoxic environment. Conclusion. Since the chick retina remains avascular after maturation of the tissue, we investigated the poss bility that VEGF expression was not regulated by hypoxia in the chick as it has been shown to be regulated in various mammalian retinas. Our da a show that chick VEGF is regulated by hypoxia as it is in other species. We conclude that the chick retina is actively producing a protein which is anti-angiogenic in nature, opposing the effects of VEGF expression. The identification of this protein may have profound implications for the treatment of nee-vascular retinopathy driven by VEGF expression in the human retina.