Intravitreal AAV2-SIRT1 administration reverses diabetic retinopathy in db/db mice

Abstract

Purpose : Diabetic retinopathy, a common complication of diabetes has been associated with the downregulation of the Sirtuin 1(SIRT1) gene. SIRT1 is a nutrient-sensing deacetylase whose dysfunction can result in chronic metabolic abnormalities. Previously we showed that activation of SIRT1 signaling in vivo reduced diabetes-induced inflammation, neural and vascular degeneration, and impairment in visual function. In this study, we examined the effect of intravitreal SIRT1-AAV therapy on reversal of diabetic retinopathy.

Methods : db/db mice were given either control virus (GFP-AAV2) or SIRT1-AAV2 via intravitreal injection at 9 months. Mice were euthanized at 12 months. Retina, peripheral blood cells and bone marrow cells were collected. Vascular changes were assessed by enumeration of acellular capillaries and retinal immune cells were assessed using flow cytometry. Immunohistochemistry was performed for SIRT1 to confirm upregulation, caspase 3 for apoptosis and IBA-1 for microglial activation. Neural function was assessed using electroretinogram responses and optomotor responses.

Results : SIRT1-AAV2 treated db/db mice showed increased retinal SIRT1 mRNA compared to control virus treated db/db mice (3±0.9 vs 0.5±0.1 respectively) and the number of SIRT1 positive cells in the retina was higher in SIRT1-AAV2 db/db mice (28.4± 6) compared to control virus treated db/db mice(13.9± 2). The number of acellular capillaries were reduced in SIRT1-AAV2 treated db/db mice (8.8±3) compared to db/db mice (11.1±4). Retinal Iba1⁺ cells were increased in db/db mice injected with control virus (9±2) and reduced in SIRT1-AAV2-treated db/db mice (4±1). Caspase-3 expression was reduced in SIRT1-AAV2-treated db/db mice (15±5) compared to db/db mice (8±3). There was a significant improvement in the b-wave in the ERG scotopic response in SIRT1-AAV2 db/db mice (326±43) compared to db/db (188±39). The retinal visual function as determined by optokinetic responses was improved in SIRT1-AAV2 treated db/db mice (0.39± 0.01) compared to the db/db mice (0.28±0.02).

Conclusions : We demonstrate that diabetic retinopathy can be prevented using a SIRT1-AAV2 intravitreal administration. We show that in addition to reduction in retinal inflammation and apoptosis, SIRT1 treatment preserved retinal bipolar cells and retinal visual function and response can be restored using this therapy.

This is a 2021 ARVO Annual Meeting abstract.