Differential Modulation of Circulating Endothelial Progenitor Cells in Peripheral Blood Monocyte Population of an Early Stage of Streptozotocin-Induced Diabetic Retinopathy

Objective: To enumerate the circulating endothelial progenitor cells (EPCs) in peripheral blood mononuclear cells (PBMC) in streptozotocin (STZ) induced diabetic retinopathy (DR) rat model. Materials and Methods: Retinal microvascular complications in STZ induced diabetic Wistar rats were validated after 4 months using trypsin digestion assay of retinal vasculature, histological analysis of retina, glial fibrillary acidic protein (GFAP) immunostaining. Subsequently, circulating EPCs were quantified in PBMCs from diabetes induced rats after 4 months using markers such as CD-34, CD-31, CD-146, VE-Cadherin and Flk-1 by flow cytometry. Results: After 4 months of diabetes induction, pericyte loss, acellular capillaries, retinal layer thickness, microglial activation and increased nitric oxide (NO) levels were observed. While the EPC markers such as CD-34, CD-31, VE-Cadherin were decreased, the Flk-1 +ve cells were up-regulated in the endogenous EPC pool. Conclusion: The quantity of EPCs are modulated in diabetes which may provide an insight into the use of EPCs as a biomarker for the progression of diabetes induced microvascular complication. Key words: Diabetic retinopathy, Endothelial progenitor cells, FlK-1, GFAP, Streptozotocin.