Akt2 overexpression in RPE cells drives retinal degeneration: a novel model to study inflammation in atrophic AMD

Abstract

Purpose : Vision loss from age-related macular degeneration (AMD) is an expanding, major unmet problem due to the aging population worldwide. Inflammation has emerged as a potential cause of AMD, but how inflammation contributes to vision loss in AMD remains controversial despite intensive study around the world. We have recently shown that the Akt2-dependent inflammatory pathway is activated in the retinas of human dry/atrophic AMD patients and triggers neutrophil infiltration into the retina. This study was undertaken to assess if Akt2 overexpression in RPE cells leads to chronic inflammation and retinal degeneration in mice, similar to atrophic AMD.

Methods : We have generated Best1 (Akt2) constitutive knock-in (KI) and Akt2 conditional knockout (cKO) mice as tools to be used in this study. RPE cells from WT, Akt2 KI and Akt2 cKO mice 1 and 4 months old were used to perform western blots for total Akt2, p-Akt2, and other inflammatory molecules like p-NFkB, IFNλ, and IL-1β. Retinal infiltration of neutrophils was assessed by flow cytometry. Hematoxylin-eosin staining was done on retinal sections and retinal function was assessed by electroretinography (ERG).

Results : We found increased expression of p-Akt2 and downstream inflammatory molecules in the RPE cells of Akt2 KI mice relative to WT, while such changes were not observed in RPE cells from Akt2 cKO mice. Furthermore, in comparison with WT and Akt2 cKO mice, we observed significant accumulation of neutrophils in retinas of 4 month old Akt2 KI mice, along with histopathological alterations including rosette formation (cardinal feature of retinal inflammation) and loss of RPE cells. Akt2 KI mice also showed a significant decrease in retinal function.

Conclusions : It can be concluded from our results that overexpression of AKt2 in RPE cells causes inflammation and retinal degeneration, along with a decline in retinal function. Thus, we believe that the Akt2 KI mouse could be an important model in understanding the inflammatory processes associated with atrophic AMD pathogenesis.

This is a 2020 ARVO Annual Meeting abstract.