Effect of diabetes mellitus on NGF and NGF-receptor distribution in retinal ganglion cells and vascularity in adult rats

Purpose Recent studies reported that NGF exerts a protective action on cells of the visual system, including retinal cells, and that eye topical application of NGF can reach brain NGF-responsive cells. The aim of the present study is to investigate the response of NGF, NGF-receptor and VEGF in retinal cells in a rat model of DM. Methods Adult SD rats were obtained from local animal facilities, maintained in a 12:12-hr light:dark cycle and had free access to tap water and food through out the experiments. Rats received a single intraperitoneal injection with 70mg/kg body weight of Streptozotocin (STZ) dissolved in PBS. Control rats received an equivalent volume of buffer solution. Animals were sacrificed with an overdose of Nembutal and pancreas, retina, optic nerve and lachrymal gland removed and used for biochemical, immunohistochemical, and molecular analysis. NGF was determined with “NGF Emax Immunoassay System” ELISA kit by Promega (USA). For histological and immunohistochemical analysis, eye globes were fixed in Bouin fluid. Twenty µm thick sections were cut with a cryostat at -20°C and immunostained for localization of NGF, NGF-receptors, or vascular endothelial growth factor. Results DT lowers the presence of NGF in the whole retina and reduces the number of retinal cells, particularly in the retinal ganglion layer, and the presence of retinal vessels. NGF administration markedly reduces these deficits. Conclusion The present findings support the hypothesis of a NGF role in retinal cell physiopathology and suggest that eye NGF application might be useful to prevent and/o reducing retinopathy induced by DT. *V. Colafrancesco has a fellowship supported by Bietti Foundation, Roma