Optic nerve damage model: A preliminary study to determine injury duration and degree of gliosis

Aims/Purpose: The aim of this study was to investigate the effects of varying durations of optic nerve compression on retinal function and morphology in an adult DA/HanR rat with optic nerve crush model. Methods: In the study, adult DA/HanR rats (4‐8 mo) were divided into 5 experimental groups. Lateral canthotomy and lateral bulbar conjunctiva incision were performed to reach the area. The optic nerve was held 2‐3 mm posterior to the globe with the help of calibrated forceps and compressed for four different periods of time: 10 seconds, 15 seconds, 30 seconds and 2 minutes. During the injury, retinal fundus observation of rats was checked with a 90‐diopter fundus lens. To evaluate changes in vision after optic nerve damage, in vivo electrophysiological tests (VEP, EEG and ERG) with daylight stimulator, a light intensity of 500 μW/cm2, was studied. Changes in optic nerve and retina morphology after injury were evaluated by hematoxylin‐eosin (H&E), TUNEL assay, immunofluorescence staining of gliosis and retina cell markers. Results: It was observed that the response to light was reduced in both the retina (ERG) and visual cortex (VEP‐EEG) in the damaged eyes compared to the control group. Retina cell survival showed decrease in injured groups by TUNEL assay. In immunofluorescence staining, an increase in the severity of gliosis with activation of the microglia and Müller cells in the retina and optic nerve depending on the duration of damage was shown by the expressions of GFAP, Glutamine Synthetase and Vimentin. It was observed that the expression of the neural marker NeuN and the photoreceptor marker Rhodopsin decreased upon injury. Conclusions: Our study provided preliminary results to further optic nerve regeneration studies to select optimum time points for improve axonal healing in retina and optic nerve injuries. Funding Information: This work is supported by the Scientific and Technological Research Council of Turkey (TÜBİTAK) under Grant ARDEB‐121S762