Abstract
Purpose :
Astrocytes and capillaries are the main non-neuronal elements that sustain RGC axonal viability. We hypothesize that the mechanical elongation of the globe due to myopia development and progression may be affecting these structures and their role in neural support. In this study, we characterized the effect of lens-induced myopia on the retinal capillaries and co-localized astrocytes of juvenile marmosets.
Methods :
Six myopic marmoset retinal whole-mounts (Rx: -6.36D±2.25, age 200±15.8 days) were compared to seven controls (Rx: -1.10D±0.62, age 293±90.56 days) and labeled with Isolectin and anti-GFAP to visualize the blood vessels and astrocytes, respectively. Using confocal microscopy, twelve images were taken per eye (z-stacks: 640x640 pixels X axis, 10 pixels Y axis). The superficial capillary density, average number of capillary branch points (CBP), number of astrocyte bodies (AB), primary processes (APP), density and morphology were quantified at the parafoveal, peripapillary, and peripheral retinal regions using Photoshop and ImageJ Fiji.
Results :
Peripheral capillary density, peripheral branching, and peripapillary branching were significantly reduced in myopic eyes compared to controls (% retinal area, myopes 13.17±4.55, controls 16.48±6.13, p<0.01; peripheral branching, myopes 71.09±31.45, controls 128.57±38.77, p<0.01; peripapillary branching, myopes 147.50±50.8, controls 89.22±34.58, p<0.05). Astrocyte morphology appeared more stellate in the myopic periphery and parafoveal region and more radial in the peripapillary region compared to control. In addition, the number of co-localized astrocyte bodies per mm2 was significantly lower across the myopic retina (myopes: 76.33±23.56 vs controls: 150.00±47.26, p< 0.001) and exhibited a decrease in primary processes on the peripapillary and parafoveal retina (peripapillary myope 3.98±0.34, control 4.42±0.57, p=0.01; parafovea myope 3.93±0.63, control 4.45±0.56, p=0.01).
Conclusions :
Marmosets with lens-induced myopia exhibited a decrease in superficial capillary density and branching along with a reduced number of co-localized astrocytes and primary processes compared to controls. These results suggest a compromised retinal perfusion and astrocytic loss, which might be expected to lead to alteration in the ability to regulate local ions, neurotransmitters and metabolites and affect neural function in eyes with progressing myopia.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.