Tunicamycin eye drops, as a chemical inducer for myopia in C57BL6J mice, by changing the scleral collagen

Abstract

Purpose : Recent studies have indicated a strong relationship between endoplasmic reticulum (ER) stress and myopia. However, it remains unclear whether ER stress of the sclera can directly induce myopia or not. This study tested the hypothesis that tunicamycin (Tm) eye drops could act as a chemical inducer to induce myopia in C57BL6J mice by changing the scleral collagen.

Methods : C57BL6J mice were treated with different concentrations (0, 25μg/ml, 50μg/ml and 100μg/ml) and/or frequencies (0, once, 3 times and 7 times) of Tm eye drops at three weeks of age. Refraction and axial length (AL) of mice were measured by eccentric infrared photorefractor and SD-OCT before and 1 week after Tm treatment. Meanwhile, alterations of collagen in the sclera were measured by picrosirius red staining and visualized under polarized light. Sclerotic ER stress-related indicators and the expression of collagen I were detected by western blotting. Data were analyzed by one-way ANOVA.

Results : Compared with the control group, mice administered with Tm eye drops at a concentration of 50μg/ml only once offered the greatest change in the expression of myopic shifts in refraction and axial length (change of refraction, -2.634±3.907 D, n=10; change of AL, 0.1253±0.0256 mm, n=10). Treatment with 50μg/ml of Tm led to a reduction in the protein expression of collagen I in the sclera (each group, n=3, each sample pooled 3 sclera). Picrosirius red staining sections were observed under polarized light and there was a significant decreased in percentage of collagen bundled in the Tm group. Treatment with Tm increased the expression of bip, p-IRE1/IRE1, p-PERK/PERK and so on which were associated with ER stress.

Conclusions : This study was conducted to establish a stable myopia mouse model by a chemical inducer. Tm eye drops induced myopic change (elongated AL and negative diopters) in C57BL6J mice. Meanwhile, Tm decreased the expression of collagen I and altered the morphological changes of collagen in the sclera which became much more loose. ER stress in the sclera may be involved in this process via PERK and IRE1 pathways.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.