Development of a new intraocular hypertension and glaucoma animal model with gold nanoparticles

Abstract

Purpose: The aim of this study was to develop a new rabbit model of glaucoma produced by GNPs with characteristics like human chronic glaucoma and to evaluate different inflammation and oxidative stress biomarkers related with glaucoma in tears, aqueous humour and retina samples, to characterize the model. Methods: Fifteen rabbits were used to the animal model development, n = 7 for model group, n = 4 for control group and n = 4 for Positive control group. The ocular hypertension model was developed by making multiple intracameral injections of 100 μl of PBS + GNPs(70 nM) in model group, only PBS (10 nM) in the control group and 100 μl of 20% Chondroitin Sulfate in the Positive control group. Increasing intraocular pression (IOP) protocol was developed during a period of 4 weeks by series of two weekly injections, followed by one‐week injection for the model group, to increase the volume of the anterior chamber. IOP was measured by Tonometer for 5 hours postoperatively and daily until the enucleation. Corneal thickness was evaluated by OCT. For biomarkers evaluation, nine rabbits were included, n = 3 for the three group. Tear collection was performed, weekly, using Schirmer test. Following the animal model design, 100 μl of aqueous humour was extracted, weekly, before the intracameral injection for the three groups. After Sacrifice, retina samples were collected. Level of Osteopontin were measured by HPLC, and Level of MMP‐9, TNF‐alpha, TGF‐beta, IL‐8 were measured by Elisa and compared between the groups. Results: The IOP was increased in the study group from 12.7 ± 1.8 mmHg at the baseline to 21.24 ± 5 mmHg after 6 weeks experiments for the model group and to 22.37 ± 4 mmHg for the positive control group, being the trend statistically significant (p < 0.05). The increasing was constant, being around 3 mmHg each week. However, no differences were found in control group for any measurement, keeping in similar values during all experiment. The corneal thickness was increased in the model group (650 ± 300 mm) and positive control group (620 ± 200 mm) comparing to control group (350 ± 50 mm). Therefore, IOP was adjusted, considering the corneal thickness. Regarding biomarkers evaluation, it was found a significant increasing of IL‐8 and MMP‐9 and a decrease of Osteopontin, in tears, after 6 weeks experiments in Model group comparing to Control group. Also, a significant increase of IL‐8 and Osteopontin, in the aqueous humour and in the retina after sacrifice, was found in model group comparing to control group. For TGF‐beta and TNF‐alpha, the difference of the concentration of biomarkers was not significant between the groups. Conclusion: Osteopontin's increase in retina of the model group, comparing to control group, can be a good alternative to convert the ocular hypertension model to Glaucoma model. This model seems to be a great option to study potential biomarkers of glaucoma. New long‐term studies to analyse the effect of GNPs in the ganglion cells density are needed to validate the glaucoma model.