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J. Garcia–Arumi, A. Fonollosa, V. Martinez–Castillo, A. Boixadera, C. Hernandez, M. Catalan, M. Zapata, M. Garcia–Ramirez, R. Simo; Erythropoietin as a Vitreous Factor in Diabetic Macular Edema . Invest. Ophthalmol. Vis. Sci. 2006;47(13):959.
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Erythropoietin is a potent ischemia–induced angiogenic factor that has been recently found increased in the vitreous fluid from diabetic patients with proliferative diabetic retinopathy (PDR). However, there are no studies on erythropoietin levels in the vitreous fluid from diabetic patients with macular edema without PDR. To elucidate this issue we've studied vitreous levels of erythropoietin in patients with diabetic macular edema.
Serum and vitreous samples from 9 consecutive type 2 diabetic patients with macular edema without PDR and without retinal ischemia evaluated by fluorescein angiography (Group 1) and 8 PDR patients (Group 2) who underwent vitrectomy were included in the study. Vitreous and serum samples from 7 non–diabetic patients with macular hole served as a control group (Group C). Erythropoietin was assessed by RIA(Incstar–Diasorin). Statistics: Man–Whitney test.
The results (mU/mL) are expressed as the median [range]. We did not found any significant difference in serum levels of erythropoietin among groups (Group1 : 12.6[7.9–46.7], Group 2: 11.5 [3.3–19.2], Group 3: 6.4 [4.1–20.8];p=n.s). Intravitreal levels of erythropoietin were higher in diabetic patients (Group 1 and Group 2) than in non–diabetic control subjects (Group 3) [Group 1 vs Group 3: 534 [99–3000] vs 30 [10–75] p<0.01 ; Group 2 vs Group 3: 343 [117–1850] vs 30 [10–75], p<0.01 ]. Higher erythropoien concentration was detected in the vitreous fluid from Group 1 than in Group 2 but the difference was not statistically significant (p=0.12). Because vitreous levels of erythropoietin may in part reflect those in serum, we calculated the ratio vitreous to serum for erythropoietin in each patient. The ratio vitreous to serum for erythropoietin remained significantly higher in Group 1 and in Group 2 in comparison with Group 3 and again no significant differences were observed between Group 1 and Group 2. Finally, no correlation between serum and vitreous levels of erythropoietin was observed in all groups.
We conclude that diabetic patients with macular edema have abundant amounts of erythropoietin within the vitreous fluid. The strikingly high levels of erythropoietin detected in the vitreous fluid in comparison with those obtained in serum strongly suggest its intraocular production. Finally, our results suggest that other factors unrelated to ischemia might be involved in the upregulation of erythropoietin in diabetic retinopathy.
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