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D. S. Kasprick, P. C. Kothary, M. A. Del Monte; Effect of PEDF on Glucose Stimulated VEGF-R2 Synthesis in Human Retinal Pigment Epithelial Cells. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1855.
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The human retinal pigment epithelium (hRPE) is a monolayer of mitotically inactive cells that lies just anterior to the choroid vascular layer of the posterior retina. Proliferation of hRPE may lead to retinal neovascularization in patients with diabetes. Research shows that a balance between two endogenous growth factors, vascular endothelial growth factor (VEGF) and pigment epithelium derived growth factor (PEDF), is required to maintain a quiescent hRPE. We have investigated whether PEDF modulates intracellular synthesis of VEGF-R2, one of the two known VEGF receptors.
hRPE cultures were established from eyes obtained from the Michigan Eye Bank. Responsiveness to biological stimuli was ascertained by measuring proliferation after cells were treated with a known mitogen, fetal bovine serum (FBS). To measure intracellular VEGF- R2 synthesis, hRPE was labeled with 14-C-methionine after treatment with control media, glucose, PEDF, or combinations of the three. Cells were immunoprecipitated with anti-VEGF-R2 antibody and protein A, and radioactivity was measured with a scintillation counter. In separate experiments, hRPE was treated with the same reagents then fluorescently labeled with anti-VEGF-R2 antibody and DAPI nuclear stain.
hRPE proliferation is stimulated by FBS in a dose dependant manner, and PEDF significantly inhibits FBS-stimulated proliferation. Glucose (20 mM) significantly stimulates 14C -VEGF- R2 synthesis, and this stimulation is inhibited by the presence of PEDF (100 ng/ml). Immunocytochemistry also suggests that glucose stimulates intracellular VEGF-R2 synthesis while PEDF inhibits it.
These data suggest that PEDF may modulate VEGF’s actions by inhibiting intracellular synthesis of VEGF - R2. Future studies to further characterize the interaction shared by PEDF and VEGF should aid in the development of pharmacological therapies for progressive retinal diseases.
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