Abstract
Purpose :
Attenuation of retinal blood vessels is a hallmark of retinitis pigmentosa (RP) and has also been reported in animal models of RP, most often in conjunction with photoreceptor death. Exploring retinal flat mounts, we tested early changes of the retinal vasculature in RP mouse models.
Methods :
Immunocytochemistry using various markers was undertaken in retinal flat mounts at p14 and p30 (n=3-6 per group). Two dominant; Rho-P347S+/- (R347) and Rho-P23H+/- (P23) and two recessive mouse models; Rds-/- (Rds) and Tulp1-/- (Tulp1) were evaluated in addition to wild type c57 and 129 controls (wt). Quantitative analysis of vessel architecture was performed using AngioTool. General morphology of retinas was assessed in cryosections.
Results :
At p14, the outer nuclear layer (ONL) was similar between RP and wt mice, however the photoreceptor segments were shortened (most notable in Rds and Tulp1 mice). By p30, the thickness of the ONL also decreased (p<0.05 for all). By p14 a significant attenuation of the main artery and vein branches was obvious; the greatest decrease in vessel thickness was in Tulp1 (17.8±3.9 um) and Rds (16.9±1.7 um) veins compared to wt (26.4±2.9 um), p<0.01. Density, length and end points of vessels, branching index and lacunarity were calculated for the superficial (SVP), intermediate (IVP) and deep (DVP) retinal vascular plexuses. Differential changes were found in these qualities in the four RP murine models (p<0.001 for all examples below). Density of the IVP decreased significantly in R347 (9.3±1.4; 11.6±0.7) and Rds (7.3±1.4; 11.3±1.3) compared to wt (14.4±0.7; 17.2±0.8) at p14 and p30. Similarly, density of the DVP decreased significantly in R347 (19.9±2.1; 15.9±1.4) and Rds (13.7±2.0; 6.6±0.9) compared to wt (24.6±1.5; 23.9±0.8) at p14 and p30. Notably, density of the DVP increased in P23 mice at p14 (30.3±1.5). Vessels end points increased significantly in P23 (330.6±21.03) and decreased in Rds (85.9±18.62) compared to wt (221.9±23.8) at p30. Similar changes were observed in vessels density/length and branching index. Lacunarity demonstrated extensive alterations.
Conclusions :
Early perturbations in retinal vasculature were different between four RP murine models. Changes did not correlate with severity of photoreceptor degeneration and included not only attenuation, as described previously, but various other alterations of vascular features.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.