Abstract
Purpose :
There is an unmet need for discovering effective treatments and creating animal models of the most prevalent neurodegenerative form of blindness in the elderly, called age-related macular generation (AMD). We performed extensive ocular characterization of an animal model exhibiting AMD-like pathology, the liver-X-receptor alpha knockout mice (LXRα-/-, Nr1h3-/-), as a function of age and identified multiple endpoints, which may serve as valuable tools in drug discovery.
Methods :
Nr1h3-/- mice were divided into three age groups: group 1 (10-14 month old), group 2 (18-22 month old) and group 3 (24-28 month old), and imaged by Micron IV to obtain fundus and optical coherence tomography (OCT) images (n=5/group). Electroretinograms (ERG) were recorded to measure dark-adapted and rod-saturated responses. Retinal morphology and ultrastructure was assessed (n=5/group). RPE-choroid flatmounts (n=4/group) were stained with phalloidin and probed with an antibody to F4/80 and CD68 to evaluate RPE structure and immune cells. Cytokine levels were measured in retinal and RPE/choroid protein lysates as a function of age (n=4/group).
Results :
In vivo, Nr1h3-/- mice exhibited inner and outer retinal hyper-reflective spots and localized deposits by OCT. The frequency of outer retinal hyper reflective spots was higher in group 2 (6/10 eyes) and group 3 (4/10 eyes) cohorts as compared to group 1 (1/10 eyes). Also, a significant decline in scotopic-a (Mean ± SEM, group 1: 183 ± 13 μV, group 2: 103 ± 12 μV, group 3: 47 ± 11 μV, group 1 vs 2: p<0.05, group 1 vs 3: p<0.01), scotopic-b (group 1: 378 ± 36 μV, group 2: 215 ± 23 μV, group 3: 110 ± 8.15, group 1 vs 2: p<0.05, group 1 vs 3: p<0.05), and photopic-b (group 1: 92 ± 6 μV, group 2: 60 ± 178 μV, group 3: 32 ± 14 μV, group 1 vs 3: p<0.05) wave amplitudes were measured with age. Morphologically, the area of RPE dystrophy quantified from RPE/choroid flatmounts increase significantly with age (group 1: 6.2 ± 0.4%, group 2: 8.4 ± 0.8%, group 3:11.5 ± 0.9%, group 1 vs 2: p<0.05, group 1 vs 3: p<0.01).
Conclusions :
Nr1h3-/- mice exhibit an age-related decline in retinal function and compromised RPE morphology, with the oldest cohort showing the most severe phenotype. End-points evaluated in the study can be employed in preventive (younger age; 4-8 months) and interventional pre-clinical studies (older age;14-18 months), testing potential experimental therapies.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.