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I. Hahm, S. Cho, H. Kim, T. Lee; The Relationship of the Expression of Vascular Endothelial Growth Factor (VEGF) and Pigment Epithelium–Derived Factor (PEDF) in Proliferative Diabetic Retinopathy . Invest. Ophthalmol. Vis. Sci. 2006;47(13):955.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the changes of the expression of VEGF and PEDF from human retinal pigment epithelium (RPE) in diabetic condition as in vitro and to measure the vitreous levels of VEGF and PEDF and the expression of VEGF and PEDF in fibrovascular membranes of proliferative diabetic retinopathy (PDR) patients as in vivo.
Cultured human RPE cells were stimulated with hypoxia (CoCl2) and high glucose concentration (4500 mg/L). RT–PCR was used to examine the expression of VEGF and PEDF mRNA. Western blot was used to detect the levels of VEGF and PEDF proteins. Vitreous samples were collected from 60 eyes of 60 patients with macular hole (control group, n=10), inactive PDR (n=25), and active PDR (n=25). The levels of VEGF and PEDF were measured by enzyme–linked immunosorbent assay (ELISA). Fibrovascular proliferative membranes were collected from 6 eyes with inactive PDR (n=3) and active PDR (n=3). The expression of VEGF and PEDF in the membranes was determined by immunohistochemistry. Blood samples were collected from the 60 patients at one day after operation. The serum levels of VEGF and PEDF were measured by ELISA.
Under hypoxic condition, the expression of VEGF mRNA and VEGF protein increased, and the expression of PEDF mRNA and PEDF protein decreased in human RPE. High concentration of glucose did not influence the expression of VEGF and PEDF in human RPE. The vitreous VEGF was not detected in control group. The VEGF levels were significantly elevated in both the inactive and active PDR groups as compared with the control group. The vitreous PEDF level was relatively high in the control group. The PEDF levels were significantly higher in patients with inactive and active PDR than in the control group. In the fibrovascular membranes stained immunohistochemically for VEGF, vascular endothelium was stained strongly. The strength of stain was not significantly different between inactive and active PDR groups. In PEDF stain, membrane stroma was stained weakly, and there was no difference between two groups. In serum, VEGF and PEDF were present at relatively high concentrations.
The results of in vivo study did not coincide with the results of in vitro study, and these results did not support ischemia–induced downregulation of PEDF. We hypothesize that the retinal vascular leakage is the reason for elevated vitreous level of PEDF in PDR patients. It is also possible that high VEGF/PEDF ratio induces retinal angiogenesis in PDR.
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