Expression of Erythropoietin and Its Receptor in the Human Retina A comparative study of diabetic and nondiabetic subjects

OBJECTIVE — The purpose of this study was to evaluate erythropoietin (Epo) and Epo receptor (EpoR) expression in the retina and in vitreous fluid from diabetic and nondiabetic donors. To gain insight into the mechanisms responsible for the regulation of Epo production in the retina, we also assessed retinal expression of hypoxia-inducible factors (HIF-1 and HIF-2). RESEARCH DESIGN AND METHODS — Eighteen postmortem eyes from 9 diabetic patients without clinically detectable retinopathy were compared with 18 eyes from 9 nondia-betic donors. mRNA of Epo, HIF-1, and HIF-2 (quantitative RT-PCR) were measured sepa-rately in neuroretina and retinal pigment epithelium (RPE). Epo and EpoR were assessed in the retina (immunofluorescence by confocal laser microscopy) and in the vitreous fluid (radioim-munoassay and enzyme-linked immunosorbent assay, respectively). RESULTS — Epo and EpoR mRNAs were significantly higher in the RPE than in the neuro-retina. Higher expression of Epo was detected in the retinas (both in the RPE and in the neuroretina) from diabetic donors. By contrast, EpoR expression was similar in both groups. We did not find any difference in HIF-1 and HIF-2 mRNA expression between diabetic and nondiabetic donors (both in RPE and neuroretina). Intravitreal Epo concentration was higher i