Academic Unit of Ophthalmology, Department of Translational Health Sciences, Faculty of Health Sciences, University of Bristol, Bristol, United Kingdom.
Bristol Eye Hospital, University Hospitals Bristol NHS Foundation Trust, Bristol, United Kingdom.
PLoS One. 2020 Feb 13;15(2):e0226311. doi: 10.1371/journal.pone.0226311. eCollection 2020.
It is not currently possible to reliably visualise and track immune cells in the human central nervous system or eye. Previous work demonstrated that indocyanine green (ICG) dye could label immune cells and be imaged after a delay during disease in the mouse retina. We report a pilot study investigating if ICG can similarly label immune cells within the human retina. Twelve adult participants receiving ICG angiography as part of routine standard of care were recruited. Baseline retinal images were obtained prior to ICG administration then repeated over a period ranging from 2 hours to 9 days. Matched peripheral blood samples were obtained to examine systemic immune cell labelling and activation from ICG by flow cytometry with human macrophage cultures as positive controls. Differences between the delayed near infrared ICG imaging and 488 nm autofluorescence was observed across pathologies, likely arising from the retinal pigment epithelium (RPE). Only one subject demonstrated ICG signal on peripheral blood myeloid cells and only three distinct cell-sized signals appeared over time within the retina of three participants. No significant increase in immune cell activation markers were detected after ICG administration. ICG accumulated in the endosomes of macrophage cultures and was detectable above a minimum concentration, suggesting cell labelling is possible. ICG can label RPE and may be used as an additional biomarker for RPE health across a range of retinal disorders. Standard clinical doses of intravenous ICG do not lead to robust immune cell labelling in human blood or retina and further optimisation in dose and route are required.
目前尚无法可靠地可视化和追踪人类中枢神经系统或眼睛中的免疫细胞。先前的工作表明，吲哚菁绿（ICG）染料可以标记免疫细胞，并在小鼠视网膜疾病发生后延迟进行成像。我们报告了一项初步研究，旨在调查 ICG 是否可以类似地标记人类视网膜内的免疫细胞。 12 名成年参与者作为常规标准护理的一部分接受了 ICG 血管造影术，他们被招募入组。在给予 ICG 之前获得了视网膜的基线图像，然后在 2 小时至 9 天的时间内重复进行。获得了匹配的外周血样本，以通过流式细胞术检查外周血中免疫细胞的标记和激活情况，并用人巨噬细胞培养物作为阳性对照。在不同的病理情况下，观察到延迟的近红外 ICG 成像与 488nm 自发荧光之间存在差异，这可能是由于视网膜色素上皮（RPE）引起的。只有一名受试者在外周血髓样细胞中显示出 ICG 信号，而在三名参与者的视网膜中，只有三个不同的细胞大小的信号随时间出现。给予 ICG 后，未检测到免疫细胞激活标志物的显著增加。ICG 在巨噬细胞培养物的内体中积累，并且在达到最低浓度以上时可检测到，这表明可以进行细胞标记。ICG 可以标记 RPE ，并且可以作为一系列视网膜疾病中 RPE 健康的附加生物标志物。静脉内 ICG 的标准临床剂量不会导致人血或视网膜中出现强大的免疫细胞标记，因此需要进一步优化剂量和途径。
