Detection of microvascular retinal changes in type I diabetic mice with optical coherence tomography angiography

Abstract

Optical coherence tomography (OCT) angiography is a dye-free and non-invasive angiography which allows visualization of retinal and choroid vascular flow, enabling observation of highly permeable and three dimensional vasculature. Although OCT angiography is providing new insights in human retinal and choroidal diseases, a few studies have been reported in experimental mice. In this study, to determine the potential of OCT angiography in experimental mice, we sought to examine whether OCT angiography can detect vascular change in type I diabetic mice. To conduct age dependent analysis, 2 and 6 month old male type 1 diabetic Ins2Akita/+ and age matched C57BL/6J mice were used. OCT angiography was performed by Heidelberg Spectralis OCT Angiography Module with 30 degree lens + mouse adapter lens. We acquired the OCT angiography image from the peripheral nasal position. For analysis of OCT angiography images, OCT angiography positive area were used for vascular density. We analyzed vascular density from the retinal surface (inner limiting membrane) to 120μm depth with 4μm steps in order to correlate vascular density vs depth (N=4 per group). Vascular density of both mouse strains demonstrated three different peaks. By comparing with the OCT image, the first peak (superficial), second peak (intermediate) and third peak (deep) were located in nerve fiber layer/ganglion cell layer, inner plexiform layer/inner nuclear layer and outer plexiform layer/outer nuclear layer, respectively. We calculated vascular density of these peaks separately. In C57BL/6J mice, the vascular density in all three layers do not show significant difference between 2- and 6-month-old. On the other hand, 6-month-old Ins2Akita/+ mice showed a significant decrease of the vascular density in all three layers compared to 2-month-old Ins2Akita/+ mice. Also, the vascular density of 6-month-old Ins2Akita/+ mice in the deep layer showed a significant decrease compared to 2- and 6-month-old C57BL/6J mice. Thus, OCT angiography successfully detects retinal vascular difference between type I diabetic mice and control mice, and age-dependent vasculature change in type I diabetic mice. The diabetic mice demonstrated reduced vascular density due to reduced density of flowing deep vessels. Importantly, we observed this difference without retinal blood leakage, hemorrhage or neovascularization. Our analysis (vascular density vs retinal depth) suggests that OCT angiography is useful for in vivo detection of retinal vasculature alteration in experimental mice.

Intravitreal AAV2.COMP-Ang1 Attenuates Deep Capillary Plexus Expansion in the Aged Diabetic Mouse Retina

“…Using OCT angiography (OCTA), we recently confirmed that 6-month old Ins2 Akita mice show significantly reduced perfusion, particularly in the deep vascular plexus 29. Even temporary lack of motion contrast (blood flow) is undetectable by OCTA, and transient occlusive events are significantly more frequent in the deep capillary bed of Ins2 Akita compared to WT mice 41.…”

“…Eight high-resolution ×40 confocal Z-stacks of the deep vascular plexus were captured approximately 2.5 objective diameters peripheral to the optic nerve and processed through AngioTool as per previous reports 17,25,28. In contrast to the progressive capillary loss reported in studies (including ours) of younger Ins2 Akita mice,13,29 retinas of the 10.5-month-old control Ins2 Akita mice demonstrated significant increases in total length and area of microvessels, number of vessel junctions, and a decrease in lacunarity compared to untreated WT retinas (Fig. 4).…”

Optical Coherence Tomography Angiography in Mice: Quantitative Analysis After Experimental Models of Retinal Damage

“…[35][36][37][38] We analyzed OCT-A images based on the recognized vascular plexuses in mice, 14 an approach that should be more suited for assessing changes in the individual vascular plexuses. Previous studies that utilized OCT-A in animal models of damage focused on choroidal neovascularization, [39][40][41] retinal neovasculization, 42 oxygen-induced retinopathy, 43 and diabetic retinopathy, 44,45 which are direct insults to the retinal vasculature or perfusion, and thus potential cell loss would be a consequence of decreased oxygenation. OCT-A changes have also been evaluated following acute intraocular pressure elevation 46,47 ; however, these studies did not determine the degree or presence of RGC loss.…”

Hydrogen sulfide: a gaseous signaling molecule modulates tissue homeostasis: implications in ophthalmic diseases

“…The altered retinal circulation of the diabetes is well documented, diabetic mice demonstrates reduced density of flowing deep vessels 122 . There may be both increased and decreased retinal blood flow in diabetic patients compared with healthy people, while no significant difference is observed in OBF between patients of nonproliferative DR and PDR 123 .…”