c-Fos expression in visual cortex of infant rhesus monkeys with myopia induced by hyperopic defocus

Objective

To observe c-Fos expression in visual cortex of infant rhesus monkeys with myopia induced by hyperopic defocus and preliminarily investigate the possibility of visual cortex participating in myopia.

Methods

Eight SPF grade healthy infant rhesus monkeys aged 20 to 30 days were randomly divided into hyperopic defocused group and control group, 4 monkeys for each group.The monkeys in hyperopic defocused group wore -3 D spectacle lenses.The monkeys in control group wore 0 D lenses.The monkeys’ refractive error, corneal topography, vitreous chamber depth were measured at the start of lens wear and at 2, 4, 6, 8, 12 weeks post-treatment.At 12 weeks post-treatment, the visual cortex tissues were removed for c-Fos protein measurement by immunohistochemistry and Western blot assays.The results were analyzed semiquantitatively to compare the differences of c-Fos expression between hyperopic defocused group and control group.The use and care of the animals complied with Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.This study protocol was approved by Ethic Committee of Zhongshan Ophthalmic Center (No.2013-014).

Results

After 12 weeks’ lens wear, the vitreous chamber elongation amplitude of hyperopic defocused group monkeys was more obvious than that of the control group ([0.93±0.24]mm vs.[0.72±0.09]mm; t=2.292, P=0.047). The decrease of hyperopic degrees of hyperopic defocused group monkeys was more obvious than that of the control group ([-3.23±1.36]D vs.[-1.55±0.52]D; t=-3.273, P=0.006). The eyes of hyperopic defocused group monkeys appeared a remarkable myopic shift after treatment.The number of c-Fos immunoreactive neurons was less in the hyperopic defocused group than that in the control group, with a statistically significant difference between them ([1 843±191]/mm² vs.[2 296±503]/mm²; t=2.381, P=0.041). Western blot assay showed that the optical density of c-Fos protein in the hyperopic defocused group was significantly less than that in the control group (0.50±0.17 vs.0.99±0.22; t=-4.982, P<0.01).

Conclusions

Hyperopic defocus, as an abnormal visual stimulus, can induce the onset of myopia in infant rhesus monkeys and inhibit c-Fos expression in visual cortex.Visual cortex may participate in myopia induced by hyperopic defocus.