Course of Sodium Iodate-Induced Retinal Degeneration in Albino and Pigmented Mice

To characterize the course of sodium iodate (SI)-induced retinal degeneration in young adult albino and pigmented mice.

Single intraperitoneal (IP) injections of SI (25, 50, and 100 mg/kg) were performed in 7- to 8-week-old BALB/c and C57Bl/6J mice. Retinal function and structure was assessed at baseline, 24 hours, 3 days, 1, 2, 3, and 4 weeks postinjection by optokinetic tracking response, ERG, optical coherence tomography (OCT), and histologic and immunohistochemical techniques.

The 50 mg/kg SI dosage was selected after dose ranging due to consistent retinal effects and lack of systemic toxicity. Time-dependent deterioration in retinal function and morphology was consistently observed between 1 and 4 weeks in all measured parameters. These include reduction of ERG responses, thinning of retinal layers as observed by OCT and histology, and loss of RPE nuclei. Immunohistochemistry revealed rapid RPE disorganization with loss of tight junctions and markedly reduced expression of RPE65 and rod opsin, accompanied by mislocalization of cone opsins. Earlier time points displayed variable results, including partial recovery of visual acuity at 1 week and supranormal ERG cone responses at 24 hours, suggesting possible limitations of early intervention and assessment in the SI model.

A single IP injection of 50 mg/kg SI leads to severe RPE injury followed by vision impairment, dysfunction, and loss of photoreceptors in both BALB/c and C57Bl/6J mice. This easily induced and reproducible noninherited model may serve as a useful tool for seeking and evaluating novel therapeutic modalities for the treatment of retinal degenerations caused by primary failure of the RPE.