Abstract
Purpose :
Pigment epithelium-derived factor (PEDF) is a multi-functional neurotrophic glycoprotein secreted by retinal pigment epithelium (RPE) in the eye. The RPE is crucial to maintaining visual function and phototransduction, i.e. facilitating waste management of cellular debris and providing nutrients for photoreceptors. We hypothesized that genetic depletion of PEDF in pigmented, photoresistant C57BL6J animals would result in progressive retinal thinning, increased recruitment of damage-associated, Galectin-3 positive (Gal-3+) microglia/macrophages, decreases in insulin-like growth factor 1(IGF-1), and changes in subretinal microglia/macrophage deposition within the RPE sheet.
Methods :
We compared PEDFKO/KO (KO mice), PEDFKO/+ (HETs), and PEDF+/+(WT) littermates on a C57BL/6J background. Animals were assessed at baseline for morphological or functional defects. Light damage (LIRD) was conducted at 50,000 lux for 5 h during the dark phase of the circadian cycle. Mice were imaged at days 3, 5, 7, and 10 after LIRD (age p60-100, n= 3-5/group). Retinal thickness and morphology were measured via SD-OCT, cSLO, and histology. Tissue was collected for RPE flatmounts, and Gal-3+ microglia were counted and analyzed with Cell Profiler and Imaris.
Results :
There were no differences across strains at baseline. After LIRD, there were regional losses in retinal thickness proximal to the optic nerve with increased infiltration of Gal-3+ cells in the subretinal space beginning at Day 5 (p<0.01, one-way ANOVA) in KO animals but not in WT or HETs. The b-wave function was significantly reduced at Day 5(p< 0.01, one-way ANOVA), while a-waves trended toward significance (p= 0.0913) in KO animals compared to littermate controls. There were statistically significant reductions in IGF-1 in KO mice (p< 0.001) and increases in Gal-3 expression (p< 0.001, 2-way ANOVA) compared to controls proximal to the optic nerve in histology sections. There were no clear differences in Muller glia morphology across strains.
Conclusions :
These data suggest that early, regional signaling of IGF-1, Gal-3, and PEDF may be potential candidates for an immunomodulatory mechanism contributing to retinal degeneration after LIRD. These data suggest a novel role of the RPE in immunomodulation. A study of PEDF influence on Gal-3+ cells may provide a better understanding of the RPE as the seat of immune regulation in the eye.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.