Morphologic Characteristics of Retinal Degeneration Induced by Sodium Iodate in Mice

Purpose: Retinal degeneration induced by sodium iodate (NaIO( 3)) in mice was evaluated morphologically.

Methods: Male and female ICR and C57BL mice were intraperitoneally administered 100 mg/kg NaIO(3) 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 NaIO(3)-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-NaIO(3), 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, Müller 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.