Histological observation of RGCs and optic nerve injury in acute ocular hypertension rats

AIM: To explore the injury of retinal ganglion cells (RGCs) and optic nerves in acute ocular hypertension (OHT) rats. METHODS: We retrogradely labeled RGCs and optic nerves of Sprague-Dawley rats by injecting 20g/L fluorogold (FG) into bilateral superior colliculi. Twenty-four hours after the injection, the right eyes were performed physiological saline anterior chamber perfusion with intraocular pressure maintained at 100mmHg for 60 minutes, while the contralateral eyes were performed sham procedure as control group without elevation of the saline bottle. Retinal hematoxylin and eosin (HE) sections, retinal whole mounts and frozen sections were made 14 days later to observe the morphology and survival of RGCs. Frozen sections and transmission electron microscopy were utilized to investigate the histological manifestations of optic nerves at the same time. RESULTS: A larger number of RGCs presented in control group. It had an average density of 1995±125/mm2 and distributed uniformly, while RGCs in OHT eyes reduced significantly to 1505±43/mm2 compared with control group (P<0.05). The optic nerves in control group showed stronger and more uniform fluorescence on the frozen sections, and the auxiliary fibers as well as myelin sheaths were in even and intact organization by transmission electron microscopy. However, exiguous fluorescence signals, vesicular dissociation and disintegration of myelin sheaths were found in OHT group. CONCLUSION: The present study suggested that fluorogold retrograde tracing is a feasible, convenient method for quantitative and qualitative study of neuronal populations and axonal injury in acute ocular hypertension rats.