Erythropoietin receptor positive circulating progenitor cells and endothelial progenitor cells in patients with different stages of diabetic retinopathy

Objective To investigate the possible involvement of erythropoietin (EPO)/erythropoietin receptor (EPOR) system in neovascularization and vascular regeneration in diabetic retinopathy (DR). Methods 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 without diabetes ( n =7), non-proliferative DR (NPDR, n =7), proliferative DR (PDR, n =8), and PDR complicated with diabetic nephropathy (PDR-DN, n =7). Results The numbers of EPOR + CPCs and EPOR + EPCs were reduced remarkably in NPDR compared with the control group (both P + CPCs in CPCs (NPDR vs. control, P + EPCs in EPCs (NPDR vs. control, P Conclusion 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.