Abstract
Purpose :
The role of rod photoreceptors, the most numerous cells in the retina, in proliferative diabetic retinopathy is unknown. This study aims to investigate if, upon exposure to elevated glucose, rod photoreceptors produce pro-angiogenic mediators and can trigger the retinal vascular endothelial cell angiogenic responses of proliferation, migration and branching.
Methods :
Primary cultures of mouse rod photoreceptors and retinal microvascular endothelial cells (RMECs) were generated and used for all experiments. The mediators produced by rod photoreceptors exposed to physiologically relevant levels of high glucose were analyzed by multiplex ELISA. Angiogenic responses of RMECs treated with photoreceptor-produced mediators, or with control stimuli, were evaluated by proliferation, migration, and tube formation assays. Transcriptomic shifts in RMECs stimulated with photoreceptor-produced mediators were assessed by qRT-PCR.
Results :
Rod photoreceptors treated with 25 mM D-glucose (high glucose) produced higher concentrations of VEGF (2.5-fold increase, p<0.05), TNF-α (2.4-fold increase, p<0.05), and IL-6 (2-fold increase, p<0.05) compared to rod photoreceptors treated with 5 mM D-glucose (normal glucose), or with 25 mM L-glucose (osmotic control). Conditioned media produced by photoreceptors treated with high glucose elicited a 2.5-fold increase in RMEC proliferation (p<0.001) and a 2-fold decrease in the time required for scratch closure by migrating RMEC (p<0.001). Photoreceptor-produced mediators had proangiogenic effects on RMEC branching and maximum RMEC tube lengths increased 1.9-fold after incubation with media from photoreceptors treated with high glucose (p<0.001). Conditioned culture medium produced by photoreceptors in high glucose conditions induced the expression of matrix metalloprotease 9 (MMP-9) (10-fold increase, p<0.001) and of MMP-2 (2.3-fold increase, p<0.001) in RMEC.
Conclusions :
Rod photoreceptors under elevated glucose conditions produce mediators that increase RMEC proliferation, migration, and branching and induce a proangiogenic transcriptomic shift in endothelial cells.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.