Abstract
Purpose :
The Tau knockout (Tau KO) mouse is an iron overaccumulation model of Parkinson’s Disease (PD) that has been shown to exhibit hallmark motor deficit and degenerative changes. Retinal alterations in this mouse model are under-studied. As such in this study, MultiColour Imaging (MCI) and Optical Coherence Tomography (OCT) were examined in the Tau KO model.
Methods :
Tau KO and WT mice at 15 months (KO: n = 13, WT: n = 12) and 18 months of age (KO: n = 12, WT n = 15) were assessed. Retinal structure was examined through OCT and retinal reflectance through MCI (Spectralis®, Heidelberg Engineering, Heidelberg, Germany). MCI produced three images of different wavelengths (blue reflectance; BR; 468nm, green reflectance; GR; 518nm and infrared; IR; 815nm) which were analyzed in an open-source FIJI software package with the mean reflectance returned. Reflectance values were expressed through reflectivity ratios of shorter wavelengths (GR and BR) against the longer wavelength (IR). A two-way ANOVA compared between genotypes (KO and WT) and age (15 months and 18 months) for OCT data whereas a mixed-effect analysis was done for MCI data to account for missing values. Outliers were removed using ROUT outlier test (Q = 1%).
Results :
This study showed that Tau KO mice had thinner OCT layers (TRT, NFL, GCIPL, INL, OPL and ONL) than age matched wild-type littermates at 15 and 18 months of age (p < 0.01). A thickening was also found in the photoreceptor segments (p < 0.01) A preferential thinning was found in the GCIPL compared with the TRT, INL, OPL and ONL (p < 0.05). The MCI reflectivity ratio showed a significant interaction and genotype effect at 18 months of age (p < 0.05) with the Tau KO mice exhibiting a greater reflectivity ratio than WTs. The 15-month-old Tau KO mice and WT littermates showed a decrease in reflectivity ratios when moving from the inner retinal layers to the outer retinal layers (p < 0.0001).
Conclusions :
This data suggests that MCI can differentiate between genotypes in a Tau KO mouse model of PD. The MCI add-on to the OCT device affords further information towards the understanding of the PD model as it allows localization of reflectance in the retinal depth dimension.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.