Abstract
Purpose :
We have previously discovered a novel role for retinoic acid (RA) signaling to promote cone survival in the peripheral retina during retinal degeneration in the rd1 mouse model of Retinitis Pigmentosa. For decades, it has been known that peripheral cones, especially dorsally, survive long-term. However, the molecular mechanism by which these cones uniquely survive was unknown. We showed that RA signaling is necessary for peripheral cone survival and that exogenous activation is sufficient for cone survival in the central retina. However, how RA signaling promotes cone survival remains unclear. Here, we explored a parallel role of RA signaling on the retinal vasculature that may be responsible for prolonged cone survival.
Methods :
Previous reports have shown that the inner retina vasculature regresses and the blood-retina-barrier (BRB) breaks down during retinal degeneration. We first determined the extent of vasculature regression by retinal flatmount immunofluorescence (IF) against an endothelial cell marker, CD31. In particular, we imaged the deep plexus vasculature (between the INL and ONL) using a spinning disk confocal microscope. Next, we detected regions of BRB leakage during cone degeneration (P27) by IF against either IgG or tail vein-injected Sulfo-NHS-Biotin. To determine the role of RA signaling on the vasculature, we electroporated a constitutively active form of the retinoic acid receptor, RARa-VP16.
Results :
During rod degeneration (P11 – P20), we found that the deep plexus vasculature regresses. Interestingly, in the peripheral regions where cones survive long-term and RA signaling is active, the deep plexus vasculature is fully absent. Starting at P20, a time point at which cones start degenerating, we found sites of BRB leakage in the central retina. However, no leakages were found in the peripheral retina, presumably because the deep plexus vasculature is absent. Exogenous activation of RA signaling in the central retina by electroporation diminished the number of blood vessels compared to controls.
Conclusions :
Here, we propose a model in which RA signaling in the peripheral retina excessively regresses the retinal vasculature, preventing BRB leakage, thereby promoting cone survival. However, additional experiments are necessary to create a causal link between BRB leakage and non-cell-autonomous cone death.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.