| Purpose:To study the expression of early growth responsive gene-1(Egr-1)and activity-regulated cytoskeleton-associated(Arc)in visual cortex and lateral geniculate body of form deprivation amblyopia kittens and normal kittens at different ages.To explore the role of Egr-1 and Arc in the pathogenesis of amblyopia.Methods:Thirty 3-week-old kittens were randomly divided into experimental group and control group with 15 kittens in each group.Raised in natural light,the deprived kittens were covered their right eyes with a black opaque covering cloth.The diopter,axial length and pattern visual evoked potential(PVEP)of all kittens were measured before and at the 1st,3rd and 5th weeks after occlusion.After each examination,5 kittens were randomly selected from each group and killed.According to the Atlas of Feline Anatomy For Veterinarians Veterinarians,the visual cortex and lateral geniculate body were separated for paraffin embedding.HE and Nissl staining were used to detect the histomorphological changes.Immunohistochemistry and in situ hybridization were used to detect the expression of Egr-1 and Arc genes.Tunel staining was used to detect apoptosis.The number of positive cells and the average optical density were analyzed by Image-Pro Plus.Results:Before occlusion,there was no significant difference in diopter and axial length between the right eye of the experimental group,the left eye of the experimental group and the right eye of the control group(P>0.05).With the increase of age,the diopter of the three groups gradually decreased and the axial length gradually increased.At the age of 6 and 8 weeks,the diopter difference among the three groups was statistically significant(P<0.05),and the diopter of the right eye of the experimental group was lower than that of the left eye of the experimental group and the right eye of the control group(P<0.05);At the age of 8 weeks,there was significant difference in axial length among the three groups(P<0.05),and the axial length of the right eye of the experimental group was longer than that of the left eye of the experimental group and the right eye of the control group(P<0.05).PVEP test showed that there was no significant difference in P100 wave amplitude and latency between the right eye of the experimental group,the left eye of the experimental group and the right eye of the control group before occlusion(P<0.05).After occlusion,with the increase of age,the amplitude of P100 wave in all three groups increased and the latency decreased(P<0.05).At 6 and 8 weeks of age,the amplitude and latent period of P100 wave were significantly different among the three groups(P<0.05),and the amplitude of the right eye of the experimental group was lower than that of the left eye of the experimental group and the right eye of the control group(P<0.05),while the latency of the right eye of the experimental group was higher than that of the left eye of the experimental group and the right eye of the control group(P<0.05).HE and Nissl staining showed that there were differences in cell morphology between the visual cortex and lateral geniculate body between the two groups.In the experimental group,Nissl corpuscles were decreased,some neurons were edema and degeneration,accompanied by local glial hyperplasia and cavernous degeneration in the visual cortex and lateral geniculate body.In the control group,the neurons in the visual cortex and lateral geniculate body had clear Nissl corpuscles,regular neuronal processes and tight intercellular structures.Immunohistochemistry showed that Egr-1 and Arc proteins were expressed in visual cortex and lateral geniculate body of the two groups,and the expression of the two proteins increased with age(P<0.05).At the age of 8 weeks,the average optical density and the number of positive cells of Egr-1 and Arc in visual cortex and lateral geniculate body of the experimental group were lower than those of the control group(P<0.05).In situ hybridization showed that Egr-l-mRNA and Arc-mRNA were expressed in visual cortex and lateral geniculate body of both groups,and the expression of both mRNA increased with age(P<0.05).At the age of 8 weeks,the average optical density and the number of positive cells of Egr-1-mRNA and Arc-mRNA in visual cortex and lateral geniculate body of experimental group were lower than those of control group(P<0.05).Tunel staining showed that the average optical density and the number of positive cells in the visual cortex and lateral geniculate body of the experimental group were higher than those of the control group at 8 weeks of age(P<0.05).Conclusions:Form deprivation can lead to down-regulation of Egr-1 gene expression in visual cortex and lateral geniculate body of kittens.The down-regulation of Egr-1 gene expression will further lead to the down-regulation of Arc gene expression in this region.Eventually,the cells in this area change in apoptosis,and then affect visual development,thus promoting the occurrence and development of amblyopia. |
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