Adult zebrafish have a complex system of retinal blood vessels. A: Wholemount retina showing central major vessels that radiate into thinner vessels covering the entire inner surface of the retina. B: Example of disparity in branch number between left (5) and right (8) eyes. C: Transverse view of the blood vessels (green: Fli1-EGFP) overlaying the inner limiting membrane of the adult retina (blue: DAPI nuclear staining). Inset shows the same vessels overlying GCL nuclei in a flatmount preparation. D: At peripheral retinal regions, neighbouring vessels anastomose (inset), and elongated filopodia sprout from the capillaries suggesting active angiogenic remodelling. E-G: The diameter of vessels is thicker proximal to the optic disc and thinner peripherally. Numbers refer to the thickness of the vessel and the angle of measurement in reference to horizontal plane. H-K: Flatmount adult retinas immuno-labelled with retinal vasculature markers. H: collagen IV (red) stains the basal membrane of blood vessels. I: smooth muscle actin (SMA) stains vascular pericytes (green). J: Factor VIII labels endothelial cells (red). Cone photoreceptors label green as analysis was performed in Tg(3.2TαCP:EGFP) transgenic line [67]. K-L: Glial fibrillary acidic protein (GFAP) stains retinal vessels in adult zebrafish and a population of cells throughout the retina. GFAP (red), DAPI (blue) and fli1-EGFP (green). K: Flat-mounted retina, and L: Transverse view of the peripheral retina. Müller endfeet (asterisks) directly contact the endothelial cells (yellow co-staining). Inset in K: FITC channel turned off to highlight the GFAP reactivity of retinal vessels. ILM: inner limiting membrane; GCL: ganglion cell layer; IPL: inner plexiform layer; OPL: outer plexiform layer; INL: inner nuclear layer; ONL: outer nuclear layer; IOC: inner optic circle.
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