HYPOXIC REGULATION OF VASCULAR GROWTH IN VITRO

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DESCRIPTION: (Candidate's Abstract) This Physician Scientist Award application focuses on the development of in vitro experimental systems to examine the role of hypoxia in the regulation of ocular vascular growth. New blood vessel formation, or angiogenesis, is important in wound healing, cyclic endometrial proliferation, placental maturation and in normal development.In mature tissues, vascular endothelial cells exist in a differentiated, quiescent state and rarely proliferate. It is likely that this quiescent state is maintained, at least in part, by a balance between local inhibitory and stimulatory factors.Abnormal blood vessel proliferation in the eye is the proximate event in visual loss in retinopathy of prematurity, proliferative diabetic retinopathy, neovascular glaucoma, age-related macular degeneration and retinal vein occlusion. Retinal ischemia increases the risk of subsequent ocular neovascularization and the studies described in this proposal examine the hypothesis that hypoxia alters the balance between inhibitory and stimulatory mediators of endothelial cell proliferation in the blood vessel wall. Transforming growth factor-B (TGF-B) has been shown to inhibit the proliferation of endothelial cells in culture. The effects of hypoxia on the production of TGF-B, however, are unknown. Studies to be performed will examine the role of hypoxia in the regulation of TGF-B. Our hypothesis predicts that there will be a relative decrease in antiangiogenic factors such as TGF-B under conditions of hypoxia leading to the loss of inhibition of endothelial cell growth and subsequent neovascularization. Vascular endothelial growth factor (VEGF) is a potent endothelial cell mitogen and has been demonstrated to be upregulated under conditions of hypoxia. Tissue hypoxia has been postulated to act as a stimulus for the release of a diffusible angiogenic factor from the retina. VEGF is a prime candidate for this role. Studies will examine the effects of VEGF on endothelial cell proliferation under hypoxic conditions. The second hypothesis to be tested is that gene expression of VEGF is regulated by hypoxia. It is known that both the amount of VEGF and VEGF mRNA are increased under hypoxic conditions. The mechanism(s) by which this occurs, however, is unknown.Experiments will examine the relative roles of increased transcription of VEGF mRNA and the possibility of an increased half-life of the VEGF mRNA.In addition, the hypoxic response element of the VEGF DNA responsible for the hypoxic induction of VEGF will be characterized. The studies outlined in this proposal will examine mechanisms by which hypoxia leads to ocular angiogenesis and will add to our understanding of ocular neovascularization with the ultimate goal of bringing us closer to a treatment of these blinding diseases. The opportunity to carry out the studies outlined in this proposal and receive formal training in cellular and molecular biology will afford the applicant the training opportunity that is required as the next step toward the establishment of her career as an independent physician scientist.