ATP-Induced Photoreceptor Death in a Feline Model of Retinal Degeneration

PURPOSE: To develop and characterize a feline model of retinal degeneration induced by intravitreal injection of adenosine triphosphate (ATP). METHODS: Nineteen normally sighted adult cats received 100 μL intravitreal injections of ATP with a final concentration of 11, 22, or 55 mM at the retina. Four animals were euthanized 30 hours after injection and retinal sections examined for apoptosis using a TUNEL cell death assay. In the remaining animals, structural and functional changes were characterized over a 3-month period using a combination of electroretinography (ERG) and optical coherence tomography (OCT). RESULTS: Using a TUNEL cell death assay, we detected widespread photoreceptor death 30 hours after injection with 55 mM intravitreal ATP. All concentrations of ATP caused loss of retinal function and gross changes in retinal structure within 2 weeks of injection. Intravitreal injection of ATP led to a rapid loss of rod photoreceptor function and a gradual loss of cone photoreceptor function within 3 months. Outer nuclear layer thickness was globally reduced by 3 months, with the inner nuclear layer including the retinal nerve fiber layer remaining intact. Structural abnormalities were observed, including focal retinal detachment with evidence of both intravitreal and intraretinal inflammation in some eyes. CONCLUSIONS: Development of an ATP-induced feline model of retinal degeneration provides a rapid and effective large-eyed animal model for research into vision restoration.