Abstract
Purpose: :
Diabetic retinopathy (DRT), one of the most serious ocular complications of diabetes (DT), is characterized by local immune cell infiltration and retinal cell degeneration. Vascular endothelial growth factor (VEGF) and nerve growth factor (NGF) have been indicated to exert overlapping and/or distinct roles in retinal cell protection and inflammation. We and others have shown that NGF is produced by and acts upon retinal cells, protecting damaged retinal ganglion cells (RGCs). We have now investigated the expression of NGF and VEGF in the retina of diabetic rats, induced by streptozotocin.
Methods: :
Control and diabetic rats were sacrificed and retina and optic nerve removed and used for histological, biochemical immunohistochemical and molecular analyses. NGF and VEGF were determined with commercially available immunoassay ELISA kits.
Results: :
It was found that DT enhances the presence of NGF in the retina and lacrimal gland (LG) and the level of VEGF in the retina, but not in the LG. The intravitreal administration of anti-NGF antibody reduces the presence of NGF and has no effect on VEGF. Moreover, diabetes down-regulates the expression TrkA-receptor in RGCs.
Conclusions: :
These findings support the hypothesis of a neuroprotective and most probably anti-inflammatory effect of NGF in diabetic retinal cells. Our previous reports, showing that NGF promotes recovery of peripheral neuropathy and corneal and skin ulcer induced by diabetes, seem to be consistent with this hypothesis. Whether NGF application can represent a potential therapeutic strategy also for RGC protection remains to be determined.
Keywords: diabetic retinopathy • growth factors/growth factor receptors • retinal neovascularization