RNAi‐mediated suppression of vimentin or glial fibrillary acidic protein prevents the establishment of Müller glial cell hypertrophy in progressive retinal degeneration

Abstract

Gliosis is a complex process comprising upregulation of intermediate filament (IF) proteins, particularly glial fibrillary acidic protein (GFAP) and vimentin, changes in glial cell morphology (hypertrophy) and increased deposition of inhibitory extracellular matrix molecules. Gliosis is common to numerous pathologies and can have deleterious effects on tissue function and regeneration. The role of IFs in gliosis is controversial, but a key hypothesized function is the stabilization of glial cell hypertrophy. Here, we developed RNAi approaches to examine the role of GFAP and vimentin in vivo in a murine model of inherited retinal degeneration, the Rhodopsin knockout (Rho−/−) mouse. Specifically, we sought to examine the role of these IFs in the establishment of Müller glial hypertrophy during progressive degeneration, as opposed to (more commonly assessed) acute injury. Prevention of Gfap upregulation had a significant effect on the morphology of reactive Müller glia cells in vivo and, more strikingly, the reduction of Vimentin expression almost completely prevented these cells from undergoing degeneration‐associated hypertrophy. Moreover, and in contrast to studies in knockout mice, simultaneous suppression of both GFAP and vimentin expression led to severe changes in the cytoarchitecture of the retina, in both diseased and wild‐type eyes. These data demonstrate a crucial role for Vimentin, as well as GFAP, in the establishment of glial hypertrophy and support the further exploration of RNAi‐mediated knockdown of vimentin as a potential therapeutic approach for modulating scar formation in the degenerating retina.

Potential Combination Drug Therapy to Prevent Redox Stress and Mitophagy Dysregulation in Retinal Müller Cells under High Glucose Conditions: Implications for Diabetic Retinopathy

“…In conclusion, our study shows that TXNIP expression, redox stress, and mitophagy dysregulation may play an important role in retinal Müller cell dysfunction in DR. Gliotic MCs produce various inflammatory cytokines, chemokines, and altered growth factors, which are harmful to retinal neurons, microvascular, and RPE [ 53 , 54 ]. In fact, mitophagy is also enhanced in human Müller cell line MIO-M1 under high glucose in vitro and in Akita mice at 2 months of diabetes duration [ 55 ], probably as a protective effort [ 19 ].…”

Intravitreal and subretinal syngeneic bone marrow mononuclear stem cell transplantation improves photoreceptor survival but does not ameliorate retinal function in two rat models of retinal degeneration

“…2015; Hippert et al . 2021), and this has been interpreted as an attempt to protect neural tissue from further damage (Hippert et al . 2021).…”

“…2021), and this has been interpreted as an attempt to protect neural tissue from further damage (Hippert et al . 2021). However, the exact role of gliosis, understood as a production of a glial scar, in inherited retinal degenerations remains unclear (Cuenca et al .…”

Outer Retinal Cell Replacement: Putting the Pieces Together

“…Although there is evidence of some efficacy following hPSC-PRP delivery even in end-stage retinal degeneration—suggesting that host inner retinal circuitry remains viable for a time—the exact window of opportunity for effective cell replacement is currently unknown. 34 , 219 Treatments being studied seek to modulate a variety of naturally occurring processes that may act as barriers to donor PR integration in the degenerate outer retina, including glial scarring, 220 interneuron plasticity, 221 and neurite outgrowth, 222 which may in turn help create a more donor cell-receptive environment. Basic discovery research to better understand the molecular mechanisms involved in retinal circuit assembly, disassembly, and re-assembly will also be essential to address host-centered barriers to neuronal replacement.…”