ABSTRACT
<p><b>OBJECTIVE</b>To investigate the possible involvement of erythr opoietin (EPO)/erythropoietin receptor (EPOR) system in neovascularization and vascular regeneration in diabetic retinopathy (DR).</p><p><b>METHODS</b>EPOR positive circulating progenitor cells (CPCs: CD34(+)) and endothelial progenitor cells (EPCs: CD34(+)KDR(+)) were assessed by flow cytometry in type 2 diabetic patients with different stages of DR. The cohort consisted of age- and sex-matched control patients with out diabetes ( n=7),non-proliferative DR (NPDR, n=7),non-proliferative DR (PDR, n=8), and PDR complicated with diabetic nephr opathy (PDR-DN, n=7).</p><p><b>RESULTS</b>The numbers of EPOR(+) CPCs and EPOR(+) EPCs were reduced remarkably in NPDR compared with the control group (both Pü0.01), whereas rebounded in PDR and PDR-DN groups in varyingdegrees. Similar changes were observed in respect of the proportion of EPOR(+)CPCs in CPCs (NPDR vs. control, Pü0.01) and that of EPOR(+) EPCs in EPCs (NPDR vs. control, Pü0.05).</p><p><b>CONCLUSION</b>Exogenous EPO, mediated via the EPO/EPOR system of EPCs, may alleviate the impaired vascular regeneration in NPDR, whereas it might aggravate retinal neovascularization in PDR due to a rebound of EPOR(+)EPCs associated with ischemia.</p>