Abstract
Purpose :
Retinal neurodegenerative diseases (NDs) are comprised of numerous disorders which result in loss of varying cell types. These diseases range from glaucoma, which affects retinal ganglion cells, to age-related macular degeneration, a late onset ND affecting cone photoreceptors and the retinal pigment epithelium, to retinitis pigmentosa and Leber congenital amaurosis, two forms of inherited retinal dystrophies (IRDs) which result in primary cell death of the rod photoreceptors (PRs). In the last two decades, groups have uncovered that most NDs are accompanied by increased release of proinflammatory cytokines and proliferation of active microglia which can expedite the disease course. The purpose of this study is to decipher the inflammatory state of the retina of the BXD32 mouse, a novel, spontaneous IRD model.
Methods :
We surveyed for IRD phenotypes using funduscopy with fluorescein angiography (F/FA), electroretinography (ERG), optokinetic nystamography (OKN), optical coherence tomography (OCT), and immunohistochemistry (IHC) for GFAP (glial fibrillary acidic protein) as well as TUNEL staining for apoptosis. We also assessed for inflammation using IHC analyses for macrophages (IBA1, ionized calcium binding adaptor molecule 1), TNFα (tumor necrosis factor alpha) and its downstream pathway components NF-κB p65 (nuclear factor kappa B p65), NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3), STAT3 (signal transducer and activator of transcription 3) along with its phosphorylated forms pSTAT3-Y705 and S727, and the pathway antagonist SOCS3 (suppressor of cytokine signaling 3).
Results :
F/FA and OCT found vessel attenuation and a rapid degeneration with most PRs lost before 24 weeks. ERG and OKN showed a steady decreasing loss of vision. IHC for GFAP and TUNEL exposed the highly stressed state of the retina with intense GFAP labeling and apoptosis. Co-labeling TUNEL with IBA1 revealed the presence of phagoptosis (phagocytosis of living cells). IHC confirmed heavy upregulation of all inflammatory markers.
Conclusions :
The BXD32 mouse exhibits a rapid and early onset retinal degeneration consistent with expectations of an IRD model. The retinas of these mice also maintain a state of steady and increasing proinflammatory signaling with aberrant phagocytosis by macrophages and dramatic increases in proinflammatory cytokine and signaling pathway proteins.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.