Neurotrophins of the retina and their involvement in early-stage diabetic retinopathy in an animal model of type 1 diabetes mellitus

IntroductionDiabetic retinopathy (DR) is a blindness-causing disease which belongs to the group of neurodegenerative diseases. Neurodegeneration of the retina is a process, in which retinal neurons suffer irreversible damage. This study aimed to assess the involvement of neurotrophins (brain-derived neurotrophic factor [BDNF] and nerve growth factor [NGF]) in the pathogenesis of DR.MethodsThe study was performed using male Lewis rats with type 1 diabetes mellitus induced by streptozotocin, and the control group included rats without drug administration. <i>In vivo</i> examinations performed over four weeks included eye fundus imaging, measurement of intraocular pressure, and glycemia. After sacrifice, serum and eyeballs were harvested. <i>Post-mortem</i> analyses included a histopathological analysis of the retina and the measurement of BDNF and NGF levels in the serum and eyeball homogenate.ResultsIn the experimental group, early-stage DR was confirmed, and changes in the retina were observed: diabetic rats had relatively thicker outer nuclear layers and relatively thinner inner plexiform layers. A lower level of BDNF was observed in the serum of rats with DR, while the level of NGF in the eyeball homogenate positively correlated with vascular changes.ConclusionsThe observed changes in the levels of neurotrophins in early-stage DR may indicate their involvement in the disease pathogenesis.