Selective expression of Nrf2 in the retinal pigment epithelium slows vision loss in rd1 mice

Abstract

Purpose : Ocular Nrf2 overexpression using an Adeno-Associated Virus (AAV 2/8) with a CMV promoter can slow cone photoreceptor death and vision loss in a mouse model of retinal degeneration. However, as the CMV promoter is active in both RPE and photoreceptors, it is unclear through which cell type(s) this protective effect is mediated. We sought to answer this question by studying the ability of cell-type specific Nrf2 AAVs to slow retinal degeneration.

Methods : AAV 2/8 constructs were made with one of two promoters: Best1 (AAV Best1), selectively expressed in RPE, and human red opsin (AAV hRedO), selectively expressed in photoreceptors. AAVs were delivered via injection to the subretinal space of rd1 or rd10 mouse eyes at p0-p2. Experimental eyes received AAV 2/8 with Best1 or hRedO promoters driving the human Nrf2 gene. For controls, some eyes were injected with AAV 2/8 Best1 or hRedO driving GFP and other eyes were left uninjected. Mice were sacrificed between P40 and P70 and their eyes flat-mounted. Cones were identified by immunostaining for cone arrestin and RPE were identified by phalloidin. Optomotor assay was used to assess visual acuity.

Results : Whole eye-mounts of rd1 mice collected between P40 and P70 injected with control AAVs (Best1 GFP or hRedO GFP) showed cone loss centrally, with RPE underlying ares of cone loss became significantly more dysmoprhic. Some eyes receiving Nrf2 AAVs showed areas of cone preservation. RPE morphology was significantly better in eyes receiving Best1 Nrf2 than hRedO Nrf2, although RPE morphology was better with hRedO Nrf2 than control. Optomotor data showed both Best1 Nrf2 and hRedO Nrf2 resulted in significantly increased visual acuity (p< 0.05) compared to control eyes in rd10 mice at later timepoints (P55 and P60). The degree of rescue was not statistically different between Best1 and hRedO Nrf2 treated eyes.

Conclusions : AAVs with cell-type selective promoters can slow degeneration and vision loss in rd1 and rd10 mice. The RPE-selective Best1 Nrf2 construct preserves RPE morphology, and also results in some vision rescue. The photoreceptor-selective hRedO Nrf2 construct rescues vision as well and surprisingly improves RPE morphology, albeit to a lesser degree than Best1 Nrf2. This suggests some protective interaction between the RPE and the surviving cones, the etiology of which we are actively investigating.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.