Development of a rat glaucoma model with azidobenzoic acid-modified chitosan (Az-CH) photocrosslinked by ultraviolet (UV) irradiation

Abstract

Purpose: The purpose of this study was to establish a rat glaucoma model of chronic intraocular pressure (IOP) elevation with intracameral injection of azidobenzoic acid-modified chitosan (Az-CH) and ultraviolet (UV) irradiation to induce photocrosslinking of the material.

Methods: Chronic IOP elevation was induced by UV irradiation following intracameral injection of Az-CH in Sprague-Dawley rats. The UV irradiation duration was 5 minutes. Twenty-four (24) eyes of 12 rats were divided into six groups: UV-irradiated Az-CH (2 mg/mL), UV-irradiated Az-CH (10 mg/mL), Az-CH (2 mg/mL), Az-CH (10 mg/mL), UV irradiation, and normal control. At the third day, IOP was measured with a TonoLab^® rebound tonometer. Thereafter, IOP changes were monitored weekly up to six weeks. Retinal flat-mounts immunolabeled with Dextran tetramethylrhodamine crystals (DTMR) were used to quantify the retinal ganglion cell (RGC) numbers.

Results: The resulting IOP elevation was maintained up to three weeks in the UV-irradiated Az-CH (10 mg/mL) group. After three weeks, IOP was increased 218.0% in the UV-irradiated Az-CH (10 mg/mL) group, 42.3% in the UV-irradiated Az-CH (2 mg/mL) group, 16.3% in the Az-CH (10 mg/mL) group, 18.1% in the Az-CH (2 mg/mL) group, and 23.6% in the UV-irradiation group. There was a significantly larger IOP increase in the UV-irradiated Az-CH (10 mg/mL) group compared with the other groups (all P < 0.05). At six weeks, the RGC density was significantly lower in all five experimental groups than in the normal control group (all P < 0.05), and there were no significant differences among the five experimental groups.

Conclusions: Intracameral Az-CH photocrosslinked by UV irradiation effectively induced chronic IOP elevation and subsequent RGC death in rat eyes.