Increased Number of Circulating Endothelial Progenitor Cells (EPCs) in Patients With Type 1 Diabetes and Proliferative Diabetic Retinopathy (PDR)

Abstract

Abstract: : Purpose: PDR–associated neoangiogenesis is a phenomenon known since a number of years but its cellular and molecular bases are still largely unknown. The recent identification in human adult perypheral blood of circulating EPCs actively participating in postnatal vasculogenesis suggested that these cells could also be involved in the pathophysiology of PDR. Methods: We isolated EPCs from whole blood of 5 type 1 diabetic patients with PDR, 5 patients without PDR despite similar age, gender distribution and duration of diabetes and 8 age– and gender–matched healthy controls. Peripheral Blood Monocyte Cells (PBMCs) were isolated and seeded at a density of 2 x 10⁵ in petri dishes pretreated with Endothelial Cell Attachment Factor (ECAF). Cells were cultured in M199 medium supplemented with 10% bovine serum. 24 hours after seeding supernatant was removed, cells were spinned and re–seeded (1 x 10⁶ per well) in a 24–wells plate. Culture medium was changed after 3 days. 7 days after seeding the experiment was stopped and colonies–forming units of EPC were counted. It is commonly accepted that after 7 days in culture in these conditions EPCs are the only adherent cells forming colonies. Each colony is originated from a single EPC and therefore the number of colonies per well may be also expressed as number of EPCs per million of circulating PBMCs. Results: The number of colonies was increased in patients with PDR (14.2 colonies ± 2.26) when compared to patients without retinopathy (0.6± 2.2, p = 0.0028). Non diabetic controls showed an intermediate number of colonies (9.5± 4.0). Conclusions: Type 1 diabetic patients with PDR have an increased number of circulating EPCs compared to patients without retinal damage, suggesting that PDR is characterized by an increased EPCs synthesis. Whether the increased number of circulating EPCs found in PDR simply parallels the intraretinal neoangiogenesis or it is directly involved in its pathogenesis remains to be clarified by further studies.

Keywords: diabetic retinopathy • proliferative vitreoretinopathy • clinical laboratory testing