Expression of interphotoreceptor retinoid-binding protein in lens-induced myopia in guinea pig

Abstract

Background The pathogenesis of myopia is currently unclear. Studies showed that retinoic acid regulates the development of myopia. Whether IRBP, a retinoid transport proteins, participates in the development of myopia or not is unknown. Objective The aim of this study was to investigate the expression of interphotoreceptor retinoid-binding protein (IRBP) in the retina of guinea pig with lens-induced myopia and study the relationship between IRBP expression and experimental myopia. Methods Fifty guinea pigs were randomized into the normal controls(n=10) ,defocus Ⅰ group (n=20) and defocus Ⅱ group (n=20). Guinea pigs in the defocus Ⅰ groups wore -10. 00 D lenses on the right eyes for 14 days and the defocus Ⅱ group for 28 days. The left eyes of both defocus groups did not wear any lens served as self-control. The refraction diopter and axial length were measured before and after wearing lenses. The protein expression of IRBP in the retina was detected by immunohistochemisty and Western blot. RT-PCR was used to observe the level of IRBP mRNA in the retina. Result Compared with the control eyes,the right eyes in the defocus Ⅰ and Ⅱ groups developed to ( -5. 53±1.93) D and (-8.69±2.46) D, and the ocular axial length elongated to (0. 31±0. 15 ) mm and (0.41 ±0. 13 ) mm, showing statistically significant differences between them ( group Ⅰ: t= 12. 57,29.63 ,P＜0.05 ;group Ⅱ :t= 15.82,44.35 ,P＜0.05 ) ,and the degree of myopia was lower and axial length was shorter in group Ⅰ than the eyes of group Ⅱ ( P＜0.05 ). There was no statistically significant differences found between the left eyes of defocus group Ⅰ and defocus group Ⅱ or eyes of the control group in diopter and axial length (P＞0.05). Immunochemistry revealed that the mean gray value of IRBP protein expression was 165.62t4. 93 and 171.00±4. 25 in defocus Ⅰ group and defocus Ⅱ group and was significantly higher than that of the self-control eyes and the normal control group ( 156. 31±4.00,155.26 ±3.49 and 158.61 ±4. 58 ) ( P＜0.05 ). Western blot demonstrated that the expressios of IRBP protein were down-regulated and RT-PCR showed the IRBP mRNA level of IRBP was significantly lower in defocusIgroup and defocusⅡgroup,compared with the self-control eyes and the normal control group (P＜0. 05). Conclusion Expression of IRBP in guinea pig may play a role in lens-induced myopia. Key words: Myopia; Defocus; Interphotoreceptor retinoid-binding protein; Retinoic acid