Morphologic characteristics of retinal degeneration induced by sodium iodate in mice

Purpose. Retinal degeneration induced by sodium iodate (NaIO3) in mice was evaluated morphologically. Methods. Male and female ICR and C57BL mice were intraperitoneally administered 100 mg/kg NaIO3 at 7 weeks of age, and were killed 6, 12, 24 hrs, and 3, 7 and 28 days after the treatment. Retinas were examined histologically, ultrastructurally, immunohistochemically, and by the TUNEL method. Results. Retinal degeneration was evoked in all NaIO3-treated mice. The primary site of damage appeared in the retinal pigment epithelial (RPE) cells followed by photoreceptor cell degeneration. Initially, the RPE cells showed necrosis starting 6 hrs post-NaIO3, followed by photoreceptor outer segment disruption and photoreceptor cell apoptosis at 24 hrs; photoreceptor cell apoptosis peaked at day 3 and was completed by day 7. At day 3, Muller cell proliferation, macrophage migration within the retina, and regeneration of damaged RPE cells occurred. Finally at day 7 and day 28, the retina showed a mosaic pattern of relatively normal retina and areas lacking RPE cells and photoreceptor cells. Conclusions. RPE cell necrosis followed by photoreceptor cell apoptosis and the resulting mosaic pattern of the retina phenotypically resembles gyrate atrophy of the choroid and retina.