[Pathogenesis of diabetic retinopathy]

Diabetic retinopathy (DR) develops in patients with both type 1 and type 2 diabetes and is the major cause of vision loss and blindness in the working population. The main risk factor of DR is hyperglycemia accompanied by enhanced mitochondrial production of reactive oxygen species and oxidative stress, formation of advanced glycation end products (AGE) and hexosamines, increased polyol metabolism of glucose. The severity of vascular injury depends on the individual genetic background and is modified by other metabolic and haemodynamic factors influencing numbers of intracellular signalling molecules such as PKC, MAPK or NF-kappaB. In diabetes, damage to the retina occurs in the vasculature (endothelial cells and pericytes), neurons and glia, pigment epithelial cells and infiltrating immunocompetent cells: monocytes, granulocytes, lymfocytes. These activated cells change the production pattern of a number of mediators such as growth factors, vasoactive agents, coagulation factors and adhesion molecules resulting in increased blood flow, increased capillary permeability, proliferation of extracellular matrix and thickening of basal membranes, altered cell turnover (apoptosis, proliferation, hypertrophy), procoagulant and proaggregant patterns, and finally in angiogenesis and tissue remodelling. The insights into pathophysiological mechanisms responsible for DR that are presented here could help in the development of a more targeted approach to its prevention and treatment.