Effects Of Retinoic Acid And LE540 In The Posterior Sclera Of Guinea Pigs Of Early Form Deprivation Myopia

PurposeThe aims of this study were detecting the retinoic acid (RA) and retinoic acid receptorβ(RARβ)level in posterior pole sclera of early form deprivation myopia (FDM) guinea pigs.To compare refractive state among different intervention groups: FD, injection of exogenous RA,and injection of RARβinhibitor LE540 conbinded with FD.To investigate scleral matrix metalloproteinase-2 (MMP-2) and decorin levels in posterior pole sclera of guinea pigs in those groups.And explore the role of RA and RARβin posterior pole scleral change of FDM guinea pigs.MethodsPart one:Monocular form deprivation models were established in 24 pigmented guinea pigs of 3-week-old (The radio-institute of Chinese Medical Sciences Academy) by covering the left eyes with facemasks and randomly divided into form deprivation 15 days group and 24 days group.Other 6 normal guinea pigs were used as control group and the fellow eyes were used as internal control.Refraction was measured before and after experiment by using retinoscopy.Eyeballs were extracted immediately at the corresponding time points and ocular axial length was measured with micrometer. Level of RA in sclera was detected by high performance liquid chromatography (HPLC),and level of RARβwas detected by western blotting.Part two:30 pigmented guinea pigs of 3-week-old were randomly divided into four groups:Left eyes of guinea pigs in group I were injected periglomerularly with 0. 1 ml LE540 (0.1 g/L) conbinded with occluded with facemask.Guinea pigs in groupⅡ(n=8)were monocularly treated with by facemasks in Left eyes only.A solution of 0.1 ml RA (0.4 g/L) was injected periglomerularly into left eyes of groupⅢ(n=8). Other 6 guinea pigs in group IV were used as control group. Refraction was measured before and after experiment by using retinoscopy.Ocular axial length was measured with micrometer. Eyeballs were made into paraffin section to do pathological examination. The level of MMP-2 and decorin was detected by western blotting. Assayed data with SPSS 11.5,and adopted analysis of variance ANOVA and T Test.ResultsPart one:Refractive dioptors reduced in experimental eyes after form deprivation, (F=23.053,P=0.000).The axial lengths were considerably increased in form deprivation after experiment (F=14.551,P=0.000) but no evident changes in fellow eyes (F=3.612, P=0.060).The dioptors and ocular axial lengths were significantly different between form deprivation eyes and fellow eyes (P>0.05).The level of RA in sclera of form deprivation eyes was higher than fellow eyes in both form deprivation 15 days and 24 days(P<0.01).But there was no significant differences in the level of RA between form deprivation 15 days and 24 days(P> 0.05).There was significant differences in RARβ/β-actin among normol, form deprivation 15 days and 24 days groups(F=20.527, P＜0.001). RARβ/β-actin in form deprivation eyes of 15 days and 24 days was higher than normal eyes(t=0.324,P＜0.001;t=0.482,P＜0.001).Part two:Relative myopia was induced in experimental eyes of groupⅡandⅢ, showing statistically differences between experimental and control eyes in both groups (t=8.543,P=0.000;t=6.027,P=0.001).Dioptors reduced by(-1.77±0.93)D in groupⅠand (-5.39±1.26)D in groupⅡ,and there was statistically significant difference between them(P=0.000);In groupⅢthe experiment eyes developed (-3.73±0.79) D myopia (t=13.340, P=0.000).Difference of axial lengths between left and right eyes in group I after the experimental intervention was not significant (t=1.635,P=0.146);but in groupⅡandⅢdifferences were significant respectively (t=2.980,P=0.021;t=4.100,P=0.005).Histopathologic examination showed thinning of posterior sclera of experimental eye in groupⅡandⅢ.MMP-2/β-actin in groupⅠ,ⅡandⅢwere significantly higher (t=4.520,P=0.020;t=6.913,P=0.006; t=5.462,P=0.012) than in control eye after experiment. Similarly,Decorin/β-actin in experimental eye were lower compared with their control eyes,the difference in group I was not statistically significant (t=2.522,P=0.086), while there was statistically significant in groupⅡandⅢ(t=9.072,P=0.003;t=4.202,P=0.025).ConclusionFDM could be induced in 15 days to 24 days after monocular occlusion,and power of refraction was increased with time. RA and RARβmay play a transductional role in early FDM. MMP-2 and Decorin in sclera have corresponding changes and ECM decomposition going fast after RA injection and FD. Inductional effect of FDM in which RA may participat in was partly inhibited by LE540.