Angiogenic Growth Factors and their Inhibitors in Diabetic Retinopathy

Diabetic retinopathy is considered one of the vision-threatening diseases among working-age population. The pathogenesis of the disease is regarded multifactorial and complex: capillary basement membrane thickening, loss of pericytes, microaneuryms, loss of endothelial cells, blood retinal barrier breakdown and other anatomic lesions might contribute to macular edema and/or neovascularization the two major and sight threatening complications of diabetic retinopathy. A number of proangiogenic, angiogenic and antiangiogenic factors are involved in the pathogenesis and progression of diabetic retinal disease, Vascular Endothelial Growth Factor (VEGF) being one of the most important. Other growth factors, which are known to participate in the pathogenesis of the disease, are: Platelet Derived Growth Factor (PDGF), Fibroblast Growth Factor (FGF), Hepatocyte Growth Factor (HGF), Transforming Growth Factor (TGF), Placental Endothelial Cell Growth Factor (PlGF), Connective Tissue Growth Factor (CTGF). Other molecules that are involved in the disease mechanisms are: intergrins, angiopoietins, protein kinase C (PKC), ephrins, interleukins, leptin, angiotensin, monocyte chemotactic protein (MCP), vascular cell adhesion molecule (VCAM), tissue plasminogen activator (TPA), and extracellular matrix metalloproteinases (ECM-MMPs). However, the intraocular concentration of angiogenic factors is counterbalanced by the ocular synthesis of several antioangiogenic factors such as pigment epithelial derived factor (PEDF), angiostatin, endostatin, thrombospondin, steroids, atrial natriuretic peptide (ANP), inteferon, aptamer, monoclonal antibodies, VEGF receptor blocker, VEGF gene suppressors, intracellular signal transduction inhibitors, and extracellular matrix antagonists. Growth stimulation or inhibition by these factors depends on the state of development and differentiation of the target tissue. The mechanisms of angiogenesis factor action are very different and most factors are multipotential; they stimulate proliferation or differentiation of endothelial cells. This review attempts to briefly outline the knowledge about peptide growth factor involvement in diabetic retinopathy. Further ongoing research may provide better understanding of molecular mechanisms, disease pathogenesis and therapeutic interactions.