A comparative study of two common optic nerve crush models in rats

Background

Optic nerve crush (ONC) model is an available tool in the basic research on the mechanism and treatment of optic nerve injury.The opening optic nerves sheath crushing and via bulbar conjunctiva lateral canthus optic nerves crushing are frequently used ONC modeling methods.However, the comparison between these models is not elaborated.

Objective

This study was to compare the outcomes between opening sheath ONC model and via bulbar conjunctiva lateral canthus ONC model.

Methods

Twenty-four male SD rats were randomized into four groups.ONC models were established via superorbital rim opening sheath to crushing optic nerve for 20 seconds in the opening sheath ONC group, or via bulbar conjunctiva lateral canthus cutting to crush optic nerve for different time in the via bulbar conjunctiva ONC 20-second, 40-second and 60-second groups, respectively.All models were monocular created in the rats, and the fellow eyes served as controls.In 14 days after modeling, flash visual evoked potential (F-VEP) were recorded, optic nerve and retinal sections were prepared in the rats.The histopathology of the samples was examined by hematoxylin and eosin staining.The expression of Brn-3α in the retinal ganglion cells (RGCs) was detected by immunofluorescence technique and the number of Brn-3α⁺ RGCs was counted.The modeling procedure and outcomes were compared between the two approaches.

Results

The latencies of P₁ waves were significantly extended in the opening sheath ONC group, via bulbar conjunctiva ONC 20-second, 40-second and 60-second groups in comparison with the corresponding control eyes (t=-11.64, -8.04, -6.50, -10.84, all at P<0.01). The P₁ latencies were longer in the opening sheath ONC group than those in the via bulbar conjunctiva ONC 20-second, 40-second and 60-second groups (P=0.01, 0.02, 0.05), but no significant differences were found in the amplitudes of P₁ waves between model eyes and corresponding control eyes (all at P>0.05). The Brn-3α⁺ RGCs numbers were evidently decreased in the model eyes in comparison with the fellow control eyes.The Brn-3α⁺ RGCs numbers were (13.60±2.14), (18.74±3.61), (15.84±2.31) and (14.58±3.23)/field in the opening sheath ONC group, via bulbar conjunctiva ONC 20-second, 40-second and 60-second groups, which reduced to 47.49%, 67.70%, 56.69% and 50.17% of the fellow eyes, respectively.No significant differences were seen in the Brn-3α⁺ RGC numbers between the opening sheath ONC group and via bulbar conjunctiva ONC 40-second or 60-second groups (both at P>0.05). The disorder of glial cell arrangement, vacuolization of the cell matrix and infiltration of inflammatory cells were displayed in various model groups, with the prominent findings in the opening sheath ONC group.

Conclusions

Compared with the via bulbar conjunctiva ONC models, the morphological and functional damage of optic nerve is more obvious, and the survival rate of RGCs is lower in the opening sheath ONC models.