Abstract
Purpose:
The aim of this study is to characterize the ocular alterations of the STZ-induced diabetes model through fluorescence angiography (FA), focal electroretinogram (fERG), and angiogenesis-related factors study by immunohistochemistry and gene expression.
Methods:
6-week-old Long Evans male rats were randomly assigned to treated (65 mg/kg STZ) and control groups (1 ml/kg citrate buffer) and divided into four time-points (1, 2, 4 and 8 weeks of diabetes). Two days after STZ administration, glucose levels were measured to assess the hyperglycemia in the STZ-treated animals. Inner and outer retinal functions were measured by fERG every week, comparing central and peripheral retina. Once a week, animals were injected with fluorescein and FA were taken to study vascular abnormalities. After each time-point animals were euthanized and eyes were enucleated. Left eyes were fixed with 4% paraformaldehide and frozen on TFM for cryosection and retinas from right eyes were isolated and frozen for RNA extraction and real time PCR. Gene and protein expression of the main angiogenesis-related factors (VEGF as the principal angiogenesis promoter and PEDF and SST as two of the most important anti-angiogenic factors) was determined.
Results:
fERG measurements showed a significant reduction of the oscillatory potentials after 8 weeks of diabetes, being higher in central retina, demonstrating inner-retinal dysfunction. Fluorescence angiographies showed increased vessel tortuosity and vascular leakage starting at week 2 after treatment, evidencing diabetes-driven retinal vascular abnormalities. Post-mortem analysis showed increased VEGF levels, glial activation and apoptosis in retinas of STZ rats compared with controls, as well as lower PEDF and SST levels.
Conclusions:
Taken together, these data give new evidences on the ocular alterations in the STZ-induced diabetes model, suggesting that this is a good aproach for the study of proliferative diabetic retinopathy, highlighting the neural and vascular abnormalities as well as proposing it for the study of neuroprotective and anti-angiogenic agents.
Keywords: 499 diabetic retinopathy •
609 neovascularization