The role of renin-angiotensin and growth factors in developmental and pathological neovascularization in the retina

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In the normal retina of newborn babies, the blood vessels in the inner layers are not fully formed. These vessels are probably stimulated to grow by a reduction in retinal oxygen, which initiates the production of growth agents in retinal cells. Once the new vessels are formed the oxygen level of the retina becomes normal, and both the growth agents and blood vessel growth are reduced. A prolonged reduction in oxygen levels in the retina can have serious consequences for vision. Indeed, in some eye diseases new blood vessel growth is excessive and the vessels are not properly formed, which leads to hemorrhage and ultimately blindness. Such events occur when the oxygen environment of premature babies is reduced after placement in high oxygen incubators. Also, in long-term diabetes, the oxygen levels of the retina falls as the retinal vessels become damaged. To understand the events that cause new vessel growth in retinal development and disease requires identification of the growth agents and their location in the retina. Very recently it has been found that the growth agent renin-angiotensin is made in the retina, and that its blockade in diabetic patients slows the progression of new retinal vessel growth. Renin-angiotensin is likely to cause its growth effects by increasing the production of other retinal growth agents. This proposal will study the role of renin-angiotensin and other growth agents in the developing newborn rat retina and in eye diseases. This information may lead to a further understanding of how blood vessels form in the retinas of newborn babies, and the production of new treatments for eye diseases characterized by blood vessel growth in the retina.