Abstract
Purpose :
Reduction in the capillary blood flow is an early sign of diabetic retinopathy in humans and animal models. Recently, we established a link between capillary vasomotor response and expression of uninterrupted strings of Cx43 gap junctions, termed the vascular relay, along the contacts between endothelial cells. Here, we tested the hypothesis that a targeted rescue of the vascular relay will improve the blood flow in diabetic retinopathy.
Methods :
First, we determined capillary blood flow in wt and STZ-induced mouse model of diabetic retinopathy in vivo using two-photon microscopy. Second, in the retinal explants from the same animals, we combined electrophysiological assessment and immunocytochemistry to determine if changes in blood flow were determined by the absence of the vascular relay and consequent impairment of vasomotor response propagation. Finally, in living retinal explants exposed to 30 mM vs. 5 mM glucose, we tested if short exposure to high glucose is sufficient to eliminate the vascular relay and whether the relay can be rescued by 100 nM danegaptide or 10 ng/ml insulin.
Results :
Capillary blood flow in vivo was significantly slower in diabetic mice (non-diabetic 44.8 ± 5.7 cells/s vs. diabetic 34.2 ± 8.4 cells/s; 5 mice), which correlated with the absence of the vascular relay and impaired vasomotor response propagation. In freshly dissected retinal wholemounts, five hours of high glucose exposure eliminated Cx43-strings in vascular endothelial cells with Cx43-plaques preserved in astrocytes. Danegaptide, but not insulin, had a protective effect in high glucose media by rescuing the vascular relay. The preservation of Cx43-strings resulted in restoration of vasomotor response propagation.
Conclusions :
Reduced blood was present early in mouse model of diabetic retinopathy and correlated with the absence of the vascular relay. We developed a new system for inducing early stage diabetic retinopathy in the dish and evaluating potential treatment. Using this system, we determined that danegaptide is effective for rescue of the vascular relay and vasomotor response. We are testing this agent in vivo. In the future, we will combine danegaptide with AAV-mediated expression of Cx43 in endothelial cells to further boost blood flow.
This is a 2020 ARVO Annual Meeting abstract.