In-vivo Longitudinal Imaging Biomarkers for Endoplasmic Reticulum Stress in Reporter Mouse Models of Retinal Degeneration: A Comparative Study with Three Mouse Models

Abstract

Purpose : To assess the in-vivo longitudinal performance of the Endoplasmic Reticulum Stress Activated Indicator (ERAI) reporter mouse across three retinal degeneration mouse models.

Methods : In continuation of our previous study (Invest. Ophthalmol. Vis. Sci. 2023;64(8):3895), we evaluated ERAI mice mated to tulp1^-/-, tulp1^F491L and Rho^P23H mice compared to ERAIWT. Rho^P23H mice express ER stress-inducing misfolded rhodopsin, tulp1^F491L mice express misfolded Tulp1, and tulp1^-/- mice express no Tulp1. A total of n= 55 mice representing all four genotypes underwent imaging at postnatal days P30, P60, and P120. The imaging protocol included confocal scanning laser ophthalmoscopy, blue autofluorescence (BAF), and infrared autofluorescence (IRAF) for specific emphasis on retinal ER stress. OCT thickness heat maps were generated via Bioptigen software to encompass the thickness of all eight retinal layers. Statistical analyses were conducted using Student’s t-test, with significance set at P < 0.05 and a 95% confidence interval.

Results : The ERAI;^RhoP23H/+ retinas showed significantly increased BAF and IRAF signal at P30, P60, and P120, when compared with ERAI;tulp1^-/-, ERAI;tulp1^F491L and ERAI;^WT retinas. The mean total retinal thickness was significantly decreased for all three (ERAI;tulp1^-/-, ERAI;tulp1^F491L and ERAI;^RhoP23H/+) but was maximum decrease observed in ERAI;Rho^P23H/+ when compared with ERAI;^WT at P120. The retinas of ERAI;^RhoP23H/+ mice exhibited notably higher levels of BAF and IRAF signals compared to those of ERAI;^tulp1-/-, ERAI;^tulp1F491L, and ERAI; ^WT mice. Moreover, there was a significant reduction in mean total retinal thickness for all three models (ERAI;^tulp1-/-, ERAI;^tulp1F491L, and ERAI;^RhoP23H/+), with the most substantial decrease observed in ERAI;RhoP23H/+ retinas when compared to ERAI; ^WT retinas at P120.

Conclusions : ERAI reporter mice enable longitudinal studies of ER stress in living mouse eyes. This was demonstrated by retinal degeneration in all three groups of mice: tulp1^-/- mice, tulp1^F491L mice, and ERAI;^RhoP23H/+ mice when compared with ERAI; ^WT . The ERAI;^RhoP23H/+ mice exhibited the most aggressive retinal degeneration and significantly increased ER stress compared to the other two groups of retinal degeneration and control ERAI;Tulp1^+/+mice.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.