In vivo epigenetic reprogramming reverses the age-induced morphological decline of retinal pigment epithelial cells

Abstract

Purpose : Aging of the retina results in a gradual visual loss due to the dysfunction and ultimately death of cells within the neural retina and retinal pigment epithelium (RPE). Importantly, aging is the highest risk factor for severe eye diseases, such as glaucoma and AMD. As the increased susceptibility of aging cells to pathological insults is a major root-cause for disease development, cell rejuvenation may prevent disease onset and/or progression. We recently reported that partial epigenetic reprogramming in vivo using AAV2-OSK (Oct4, Sox2, Klf4) reversed the biological age of retinal ganglion cells (RGCs) in 12-month-old mice as determined by their epigenetic clock, increased visual function, and “youthful” methylome and transcriptome profiles. In the current study we examined whether in vivo epigenetic reprogramming can be applied to RPE and reverse aging of the outer-retina complex.

Methods : 24-month-old mice received subretinal injections of AAV2-OSK. Negative controls included mice that received AAV2-GFP, or no injections. Young mice (4-6 months) were used as positive controls. Visual acuity was measured via optomotor reflex (OMR), and phototransduction assessed by scotopic ERG. Morphological examinations were conducted on retinal sections via TEM and by immunostaining of RPE whole mounts.

Results : Compared to young mice, aged mice showed reduced visual acuity (p<0.05, n=12) with marked loss of photoreceptor, bipolar and RPE ERG responses (a and b wave p<0.0001, c wave p<0.001, n=10). Subretinal injection of AAV2-OSK transduced approximately 50% of the RPE and did not alter cell number, area and nuclei/cells at two weeks. Histological analysis showed improved retinal morphology in the OSK+ regions of experimental aged mice compared to the controls (AAV2-GFP, or uninjected). Ultrastructural imaging confirmed reduced phenotypic markers of RPE dysfunction and aging in OKS-treated eyes characterized by decreased dysmorphic RPE, reduced lipofuscin and undigested outer-segment accumulation, increased choriocapillaris fenestrations and reduced basal laminar deposits.

Conclusions : In vivo epigenetic reprogramming with OSK reversed these age-induce morphological changes, restoring RPE to a youthful morphology. These data imply epigenetic reprogramming can reverse the effects of aging and restore function to aging RPE, which may lead to a new approach to therapeutically treat AMD.

This is a 2021 ARVO Annual Meeting abstract.