In vivo studies of changes in Photoreceptor-RPE-Choroid Neurovascular Unit (PRC-NVU) morphology and function in the mouse models of Doyne Honeycomb Retinal Dystrophy and RPE mitochondrial dysfunction

Abstract

Purpose : To present the in vivo results of Photoreceptor-RPE-Choroid Neurovascular Unit (PRC-NVU) morphology and function monitored locally and longitudinally as a function of age in mouse models of Doyne Honeycomb Retinal Dystrophy and RPE mitochondrial dysfunction.

Methods : Three cohorts of Efemp1^R345W/R345W (hereafter referred to as Efemp1) and RPEΔMT mice bred into the albino C57BL/6J-Tyr-c-Brd background, and control albino C57BL/6J-Tyr-c-Brd were imaged over one year to monitor the longitudinal changes in PRC-NVU morphology and function. Efemp1 mice are a model of Doyne Honeycomb Retinal Dystrophy, an inherited macular degeneration in which a point mutation in fibulin-3 causes basal deposits over the BrM. RPEΔMT mice (triple cross of Tfam^lox/lox and Best1-Cre+ on an albino C57BL/6J-Tyr-c-Brd background) have RPE mitochondrial dysfunction and exhibit spatial variation in deterioration of RPE mosaic and cellular structure. Our in vivo measurements included (1) SLO-based autofluorescence mapping; (2) OCT-based: PRC-NVU morphology ; (3) bleaching-activated optophysiology; (4) OCTA-based choriocapillaris and choroidal vasculature mapping; (5) ERGs for analysis of rod-driven photoreceptor function.

Results : The lack of melanin in albino mice allowed investigation of BrM, Rods Outer Segments Tips (ROST) and choriocapillaris morphology, giving Efemp1 and RPEΔMT mice bred on an albino background a clear advantage for monitoring progression of retinal degeneration in this model. The presence of melanin in pigmented mice makes direct measurements of BrM thickness impossible and mapping of choriocapillaris challenging. Efemp1 and RPEΔMT mouse strains showed an accelerated deterioration of PRC-NVU complex structure and function as compared to age-matched controls.

Conclusions : We used innovative cellular-level resolution in vivo imaging combined with additional functional tests to characterize age-related changes in the structure and function of cells of the PRC-NVU in two cohorts of mice with the genetic defects relative to their controls. Our ability to follow degeneration with in vivo imaging methods and automated image analysis allowed a drastic reduction in the number of animals needed for the studies, and permited a fast analysis of correlative, local changes in structure and function.

This is a 2020 ARVO Annual Meeting abstract.