Elevation of monocyte-derived microparticles in patients with diabetic retinopathy

Diabetic retinopathy is associated with microvascular damage and capillary occlusions which are common features of the microangiopathy in diabetes. Monocyte-derived microparticles (MDMPs) are released from activated monocytes and enhance the procoagulant activity, and also activate adhesion reactions. These are key events in the development of capillary occlusion.The MDMPs level in the blood, and platelet activation markers (platelet-derived microparticles (PDMPs), CD62P and CD63) were measured by flow cytometry in 72 diabetic patients. The plasma levels of intracellular adhesion molecule-1 (ICAM-1) and P-selectin were analyzed by ELISA. The level of MDMPs was significantly correlated with the levels of PDMPs (r = 0.52, P < 0.001), CD62P (r = 0.37, P = 0.001), CD63 (r = 0.31 and P = 0.007), P-selectin (r = 0.38, P = 0.001), and ICAM-1 (r = 0.31, P = 0.009). The MDMPs level increased with the progression of the diabetic retinopathy: 81 ± 14/104 platelets (plts) in patients without retinopathy (n = 10); 88 ± 8/104 plts with mild or moderate non-proliferative diabetic retinopathy (NPDR, n = 12); 95 ± 8/104 plts with severe NPDR (n = 24); and 112 ± 9/104 plts with proliferative diabetic retinopathy (PDR) (n = 26). The MDMPs level in patients with areas of capillary occlusion (123 ± 10/104 plts, n = 25) was significantly higher than that in patients without areas of capillary occlusion (84 ± 5/104 plts, n = 25; P = 0.0008). These correlations suggest that increased levels of MDMPs may accelerate the progression of diabetic retinopathy.