Postnatal Visual Deprivation in Rats Regulates Several Retinal Genes and Proteins, Including Differentiation-Associated Fibroblast Growth Factor-2

Little is known about the retinal cellular basis of amblyopia, which is a developmental disease characterized by impaired visual acuity. This study examined the retinal transcripts associated with experimentally induced unilateral amblyopia in rats. Surgical tarsorrhaphy of the eyelids on one side was performed in pups prior to eye opening at postnatal day 14, thereby preventing any visual experience. This condition was maintained for over 2 months, after which electroretinograms (ERGs) were recorded, the retinal ganglion cell (RGC) arrangement and number were determined using neuroanatomical tracing, the retinal transcripts were studied using microarray analysis, regulated mRNAs were confirmed with quantitative reverse-transcriptase PCR, and proteins were stained using Western blotting and immunohistochemistry. An attenuated ERG was found in eyes that were deprived of visual experience. Retrograde neuroanatomical staining disclosed a larger number of RGCs within the retina on the visually deprived side compared to the non-deprived, control side, and a multilayered distribution of RGCs. At the retinomic level, several transcripts associated with retinal differentiation, such as fibroblast growth factor 2 (FGF-2), were either up- or downregulated. Most of the transcripts could be verified at the mRNA level. To unravel the role of a differentiation-associated protein, we tested FGF-2 in dissociated postnatal retinal cell cultures and found that FGF-2 is a potent factor triggering ganglion cell differentiation. The data suggest that visual experience shapes the postnatal retinal differentiation, whereas visual deprivation induces changes at the functional, cellular and molecular levels within the retina.