Decreased angiogenin concentration in vitreous and serum in proliferative diabetic retinopathy

Diabetic retinopathy is the most common cause of vision loss in young adults in developed countries. The disease therapy with anti-vascular endothelial growth factor (VEGF) agents gives some positive results, but is associated with retinal ischemia and vasoconstriction. Therefore, determination of factors involved in the physiological and pathological angiogenesis in the diabetic eye is of great importance for understanding of the pathogenesis of diabetic retinopathy and its effective treatment. Previously, we found that diabetic patients were characterized by increased serum concentration of VEGF, but decreased levels of other proangiogenic factor-angiogenin. The involvement of VEGF in pathogenesis of diabetic retinopathy is well established, but there is lack of data regarding angiogenin in retinopathy. Therefore, in the present study we measured angiogenin concentration in vitreous and serum samples of the patients with type 1 diabetes to determine its role in diabetic retinopathy. In addition, in each time, we compared the level of angiogenin with level of VEGF as a known factor involved in the pathogenesis of the disease. Angiogenin was found to be significantly more abundant in serum than in vitreous in both diabetic groups. In addition, patients with retinopathy had twofold lower vitreous angiogenin levels than diabetic individuals without complications. On the contrary, vitreous concentration of VEGF was dramatically increased only in participants with retinopathy. Patients without diabetic complications had significantly lower VEGF levels in vitreous than in serum and were characterized by high local and systemic concentration of angiogenin. These data suggest a local imbalance between two proangiogenic factors-VEGF and angiogenin in retinopathy. Low vitreous concentration of angiogenin in diabetic patients suggests that this factor is not responsible for pathological neovascularization in diabetic eye. Further studies will elucidate if angiogenin can be used to improve the insufficient angiogenesis in diabetes and prevent retinal ischemia after retinopathy treatment with anti-VEGF agents.