Platelet Fibronectin Levels as a Marker for the Progression of Diabetic Retinopathy

Abstract

Aim of the study was to correlate fibronectin (Fn) and von Villebrand factor (vWf) levels measured in plasma and in platelets with the progression of diabetic retinopathy. Patients were classified in five groups reflecting the progression of this microvascular complication, on the basis of fluorangiographic findings (0 = no microangiopathy; 1= simple microangiopathy; 2= oedematous retinopathy; 3= ischaemic retinopathy; 4= ischaemic proliferative retinopathy). 43 patients were studied, 22 suffering from type I diabetes and 21 from type II diabetes, according to the classification of National Diabetes Data Group. Fn and vWf were measured in plasma and in platelet samples using an original double-sandwich microELISA method and expressed as micrograms/ml or as micrograms/10* platelets. Platelets were counted and solubilized with 0.5% Triton × 100. Bleeding time and platelet adhesion to glass beads were also evaluated on every patient. Intraplatelet Fn levels were reduced in retinopathies and correlate with the severity of the microvascular alteration, being the difference significant between the two extreme groups (p<0.05). vWf intraplatelet levels were also significantly lower in patients with severe microvascular complications (p<0.05). No significant differences were detected for plasma Fn and vWf levels in the 5 groups. Intraplatelet Fn and vWf levels may therefore be considered as markers of the severity of diabetic retinopathy. The leakage of Fn and vWf from activated platelet and the incorporation of these glycoproteins in the subendothelial matrix may be responsible for the worsening of this microvascular complication.