Inducement and Evaluation of a Murine Model of Experimental Myopia

Murine model of myopia can be a powerful tool for myopia research because of the comparatively easy genetic manipulation. One way to induce myopia in ...

A Murine Model of Ischemic Retinal Injury Induced by Transient Bilateral Common Carotid Artery Occlusion

Diverse vascular diseases such as diabetic retinopathy, occlusion of retinal veins or arteries and ocular ischemic syndrome can lead to retinal ischemia. ...

Keio University School of Medicine

Despite the global pandemic of myopia, the precise molecular mechanism of the onset of myopia remains largely unknown. This is partially because of the lack of efficient murine myopic models that allow genetic manipulation at low cost. Here we report a highly practical and reproducible lens-induced myopia model by specially designed frames and lenses for mice. A lens power dependent myopic induction in mice was shown until minus 30 diopter lenses. The phenotype was significantly stronger than form-deprivation myopia. We presented the protocol for precise evaluations of the state of myopia, including refraction, corneal curvature and axial length using up-to-date devices. We also found that myopic mouse eyes showed decreased visual acuity on optokinetic response examination. Finally, we confirmed the anti-myopic effect of 1% atropine using this model, which showed its potential in drug screening. The strong phenotype, stable evaluation and the potential for gene manipulation utilizing the presented method in mice will accelerate the translational research of myopia.

A highly efficient murine model of experimental myopia.

Increased global incidence of myopia necessitates establishment of therapeutic approaches against its progression. To explore agents which may control myopia, we screened 207 types of natural compounds and chemical reagents based on an activity of a myopia suppressive factor, early growth response protein 1 (Egr-1) in vitro. Among the candidates, crocetin showed the highest and dose-dependent activation of Egr-1. For in vivo analysis, experimental myopia was induced in 3-week-old C57BL/6 J mice with -30 diopter (D) lenses for 3 weeks. Animals were fed with normal or mixed chow containing 0.003% (n = 19) and 0.03% (n = 7) of crocetin during myopia induction. Refraction and axial length were measured at 3-week-old and the 6-week-old with an infrared photorefractor and a SD-OCT system. Compared to controls (n = 14), crocetin administration showed a significant smaller change of refractive errors (-13.62 ± 8.14 vs +0.82 ± 5.81 D for 0.003%, p < 0.01, -2.00 ± 4.52 D for 0.03%, p < 0.01) and axial elongation (0.27 ± 0.03 vs 0.22 ± 0.04 mm for 0.003%, p < 0.01, 0.23 ± 0.05 mm for 0.03%, p < 0.05). These results suggest that a dietary factor crocetin may have a preventive effect against myopia progression.

Oral crocetin administration suppressed refractive shift and axial elongation in a murine model of lens-induced myopia.

The prevalence of myopia has been increasing in recent years. The natural carotenoid crocetin has been reported to suppress experimental myopia in mice. We evaluated the effects of crocetin on myopia suppression in children. A multicenter randomized double-blind placebo-controlled clinical trial was performed with 69 participants aged 6 to 12 years, whose cycloplegic spherical equivalent refractions (SER) were between -1.5 and -4.5 diopter (D). The participants were randomized to receive either a placebo or crocetin and followed up for 24 weeks. Axial length (AL) elongation and changes in SER were evaluated for 24 weeks. Both written informed assent from the participants and written informed consent from legal guardians were obtained in this study because the selection criteria of this trial included children aged between 6 and 12 years old. This trial was approved by the institutional review boards. A mixed-effects model was used for analysis, using both eyes. Two participants dropped out and 67 children completed this trial. The change in SER in the placebo group, -0.41 ± 0.05 D (mean ± standard deviation), was significantly more myopic compared to that in the crocetin group, -0.33 ± 0.05 D ( = 0.049). The AL elongation in the placebo group, 0.21 ± 0.02 mm, was significantly bigger than that in the crocetin group, 0.18 ± 0.02 mm ( = 0.046). In conclusion, dietary crocetin may have a suppressive effect on myopia progression in children, but large-scale studies are required in order to confirm this effect.

The Effect of Dietary Supplementation of Crocetin for Myopia Control in Children: A Randomized Clinical Trial.

Given the estimates of increasing prevalence of myopia, especially in Asia, it is important to determine the current prevalence of myopia among populations of schoolchildren in Japan.

Current Prevalence of Myopia and Association of Myopia With Environmental Factors Among Schoolchildren in Japan.

Whether hyperoxia affects the refraction in neonatal and adult mice is unknown. The mice exposed to 85% oxygen at postnatal 8 days (P8d) for 3 days and the mice exposed to normal air were assigned to the neonatal hyperoxia and normoxia groups, respectively. The refraction, the corneal curvature radius (CR) and the axial length (AL) were measured at P30d and P47d. Postnatal 6 weeks (P6w) adult mice were divided into the adult hyperoxia and normoxia groups. These parameters were measured before oxygen exposure, after 1 and 6 weeks, and every 7 weeks. The lens elasticity was measured at P7w and P26w by enucleation. The neonatal hyperoxia group showed a significantly larger myopic change than the neonatal normoxia group (P47d -6.56 ± 5.89 D, +4.11 ± 2.02 D,  < 0.001), whereas the changes in AL were not significantly different (P47d, 3.31 ± 0.04 mm, 3.31 ± 0.05 mm,  = 0.852). The adult hyperoxia group also showed a significantly larger myopic change (P12w, -7.20 ± 4.09 D, +7.52 ± 2.54 D,  < 0.001). The AL did not show significant difference (P12w, 3.44 ± 0.03 mm, 3.43 ± 0.01 mm,  = 0.545); however, the CR in the adult hyperoxia group was significantly smaller than the adult normoxia group (P12w, 1.44 ± 0.03 mm, 1.50 ± 0.03 mm,  = 0.003). In conclusion, hyperoxia was demonstrated to induce myopic shift both in neonatal and adult mice, which was attributed to the change in the CR rather than the AL. Elucidation of the mechanisms of hyperoxia and the application of this result to humans should be carried out in future studies.

Effects of Hyperoxia on the Refraction in Murine Neonatal and Adult Models.

The natural carotenoid crocetin has been reported to suppress phenotypes of an experimental myopia model in mice. We investigated the minimum effective dose to prevent myopia progression in a murine model. Three-week-old male mice (C57B6/J) were equipped with a -30 diopter (D) lens to induce myopia, and fed with normal chow, 0.0003%, or 0.001% of crocetin-containing chow. Changes in refractive errors and axial lengths (AL) were evaluated after three weeks. Pharmacokinetics of crocetin in the plasma and the eyeballs of mice was evaluated with specific high sensitivity quantitative analysis using liquid chromatography tandem mass spectrometry (LC-MS/MS) to determine the minimum effective dosage. A concentration of 0.001% of crocetin-containing chow showed a significant ( < 0.001) suppressive effect against both refractive and AL changes in the murine model. Meanwhile, there was no significant difference of AL change between the 0.0003% and the normal chow groups. The concentration of crocetin in the plasma and the eyeballs from mice fed with 0.001% crocetin-containing chow was significantly higher than control and 0.0003% crocetin-containing chow. In conclusion, we suggest 0.001% of crocetin-containing extract is the minimum effective dose showing a significant suppressive effect against both refractive and AL changes in the murine model.

Shin-ichi Ikeda

Laboratory of Photobiology,
Department of Ophthalmology

Keio University School of Medicine

Inducement and Evaluation of a Murine Model of Experimental Myopia

A Murine Model of Ischemic Retinal Injury Induced by Transient Bilateral Common Carotid Artery Occlusion

Shin-ichi Ikeda

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Laboratory of Photobiology,Department of Ophthalmology

Keio University School of Medicine

Inducement and Evaluation of a Murine Model of Experimental Myopia

A Murine Model of Ischemic Retinal Injury Induced by Transient Bilateral Common Carotid Artery Occlusion

Laboratory of Photobiology,
Department of Ophthalmology