Abstract
This study aimed to investigate the differences between images obtained by optical coherence tomography angiography (OCTA) with those from immunohistochemical labeling of laser-induced choroidal neovascularization (CNV) in a mouse model. CNV was induced by laser photocoagulation (GYC-2000, NIDEK; wavelength 532 nm) in the left eyes of 10 female C57BL/6J mice aged 6 weeks. The laser parameters included a 100-μm spot, 100-ms pulse duration and 200-mW incident power to rupture Bruch’s membrane. OCT and OCTA CNV images were obtained using the RS-3000 Advance (NIDEK) 5 days post-laser photocoagulation. After OCTA imaging, the isolated choroid/retinal pigment epithelium complexes were fluorescently labeled with CD31 (an endothelial cell marker), platelet-derived growth factor receptor β (PDGFRβ, a pericyte-like scaffold marker), α-smooth muscle actin (α-SMA) and collagen I. Area measurements of the lesions obtained by enface OCTA were compared with immunolabeled CD31+ CNV lesions in choroid flat-mounts. We also examined structural correlations between the PDGFRβ+ pericyte-like scaffold and OCTA images. Laser-induced CNV was clearly detected by enface OCTA, appearing as a hyperflow lesion surrounded by a dark halo. Area measurements of the CNV lesion by immunolabeling were significantly larger than those obtained by enface OCTA (p = 0.006). The CNV lesion beneath the periphery of the pericyte-like scaffold was not clearly visible by enface OCTA due to the dark halo; however, the lesion was detectable as blood flow by cross-sectional OCTA and was also highly labeled by CD31. The periphery of the pericyte-like scaffold appeared to develop into subretinal fibrosis and this region was rich in myofibroblasts. Enface OCTA was unable to detect the entire area of laser-induced CNV in mice, with an undetectable portion located beneath the fibrotic periphery of the pericyte-like scaffold. Due to this OCTA fibrosis artifact, OCTA imaging has limited potential for accurately estimating CNV lesions.
Highlights
Optical coherence tomography angiography (OCTA) is a novel imaging tool which allows the visualization of the retinal and choroidal vasculature
Representative OCT, OCTA and immunolabeling images of laser-induced choroidal neovascularization (CNV) at day 5 post-laser photocoagulation. (A) By enface OCTA, laser-induced CNV was observed as a hyperflow lesion surrounded by a dark halo. (B) By cross-sectional OCTA imaging blood flow was detected between the deep retina and choroid. (C) By OCT, laser-induced CNV and the pericyte-like scaffold appeared as a subretinal hyper-reflective lesion. (D) Laser-induced CNV lesions were stained with CD31. (E) The pericyte-like scaffolds were stained with platelet-derived growth factor receptor β (PDGFRβ)
Images from OCTA and immunolabeling experiments in laser-induced CNV at 5 days post-laser photocoagulation. (A) By enface OCTA, laserinduced CNV was observed as a hyperflow lesion surrounded by a dark halo (Ã; areas measured 900×900 μm). (B-D) The pericyte-like scaffold was stained with α-smooth muscle actin (α-smooth muscle actin (SMA)) (B), PDGFRβ (C), and collagen type I (D; shown in gray scale)
Summary
Optical coherence tomography angiography (OCTA) is a novel imaging tool which allows the visualization of the retinal and choroidal vasculature. This method is based on split-spectrum amplitude-decorrelation angiography (SSADA) and detects blood flow as the motion of erythrocytes [1]. Because of its noninvasive aspects (OCTA does not require the use of dye injection as in fluorescein angiography [FA] or indocyanine green angiography [ICGA]), this new method has been successfully applied in daily clinical ophthalmological practice. Some studies have reported that OCTA could be used to detect choroidal neovascularization (CNV) and evaluate therapeutic responses in exudative age-related macular degeneration (AMD) [2,3].
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