Sodium Iodate: Rapid and Clinically Relevant Model of AMD.

BACKGROUND

Age-related macular degeneration (AMD) is the most common cause of vision loss in people above the age of 50, affecting approximately 10% of the population worldwide and the incidence is rising. Hyperreflective foci (HRF) are a major predictor of AMD progression. The purpose of this study was to use the sodium iodate mouse model to study HRF formation in retinal degeneration.

METHODS

Sodium iodate (NaIO3) treated rodents were studied to characterize HRF. 3-month-old male wild-type (WT) C57Bl/6J mice were injected with phosphate-buffered saline (PBS) or varying doses of NaIO3 (15-60 mg/kg). Optical Coherence Tomography (OCT) images were collected at baseline and several days post-NaIO3 injection. Retinal thicknesses were measured using Bioptigen software. Seven days post-injection, eyes were prepared for either transmission electron microscopy (TEM), Hematoxylin & Eosin (H&E), or immunofluorescence.

RESULTS

OCT imaging of the mice given higher doses of NaIO3 revealed HRF formation in the neural retina (n = 4). The amount of HRF correlated with the degree of retinal tissue loss. H&E and TEM imaging of the retinas seven days post-NaIO3 injection revealed several pigmented bodies in multiple layers of the retina (n = 3-5). Immunofluorescence revealed that some pigmented bodies were positive for macrophage markers and an epithelial-to-mesenchymal transition marker, while all were retinal pigment epithelium (RPE) 65-negative (n = 4).

CONCLUSIONS

The data suggest that NaIO3 induces the formation of HRF in the outer retina and their abundance correlates with retinal tissue loss. The experiments in this study highlight NaIO3 as a clinically relevant model of intermediate AMD that can be used to study HRF formation and to discover new treatment targets.