Lim Jeremiah K H, Li Qiao-Xin, Ryan Tim, Bedggood Phillip, Metha Andrew, Vingrys Algis J, Bui Bang V, Nguyen Christine T O
Department of Optometry and Vision Sciences, University of Melbourne, Parkville, VIC, 3010, Australia.
Optometry and Vision Science, College of Nursing and Health Sciences, Flinders University, Bedford Park, SA, 5042, Australia.
Sci Rep. 2021 Mar 18;11(1):6387. doi: 10.1038/s41598-021-85554-2.
Hyperspectral imaging of the retina has recently been posited as a potentially useful form of spectroscopy of amyloid-beta (Aβ) protein in the eyes of those with Alzheimer's disease (AD). The concept of using the retina as a biomarker for AD is an attractive one, as current screening tools for AD are either expensive or inaccessible. Recent studies have investigated hyperspectral imaging in Aβ models however these studies have been in younger mice. Here we characterised hyperspectral reflectance profile in 6 to 17 months old 5xFAD mice and compare this to Aβ in isolated preparations. Hyperspectral imaging was conducted across two preparations of Aβ using a custom built bench ophthalmoscope. In the in vitro condition, 1 mg of purified human Aβ42 was solubilised and left to aggregate for 72 h. This soluble/insoluble Aβ mixture was then imaged by suspending the solution at a pipette tip and compared against phosphate buffered saline (PBS) control (n = 10 ROIs / group). In the in vivo condition, a 5xFAD transgenic mouse model was used and retinae were imaged at the age of 6 (n = 9), 12 (n = 9) and 17 months (n = 8) with age matched wildtype littermates as control (n = 12, n = 13, n = 15 respectively). In the vitro condition, hyperspectral imaging of the solution showed greater reflectance compared with vehicle (p < 0.01), with the greatest differences occurring in the short visible spectrum (< 500 nm). In the in vivo preparation, 5xFAD showed greater hyperspectral reflectance at all ages (6, 12, 17 months, p < 0.01). These differences were noted most in the short wavelengths at younger ages, with an additional peak appearing at longer wavelengths (~ 550 nm) with advancing age. This study shows that the presence of Aβ (soluble/insoluble mixture) can increase the hyperspectral reflectance profile in vitro as well as in vivo. Differences were evident in the short wavelength spectrum (< 500 nm) in vitro and were preserved when imaged through the ocular media in the in vivo conditions. With advancing age a second hump around ~ 550 nm became more apparent. Hyperspectral imaging of the retina does not require the use of contrast agents and is a potentially useful and non-invasive biomarker for AD.
视网膜的高光谱成像最近被认为是一种对阿尔茨海默病（AD）患者眼部淀粉样β蛋白（Aβ）进行光谱分析的潜在有用形式。将视网膜用作AD生物标志物的概念很有吸引力，因为目前AD的筛查工具要么昂贵，要么难以获得。最近的研究对Aβ模型中的高光谱成像进行了研究，然而这些研究是在较年轻的小鼠身上进行的。在这里，我们对6至17个月大的5xFAD小鼠的高光谱反射率特征进行了表征，并将其与分离制剂中的Aβ进行了比较。使用定制的台式检眼镜对两种Aβ制剂进行了高光谱成像。在体外条件下，将1mg纯化的人Aβ42溶解并使其聚集72小时。然后通过将溶液悬浮在移液器尖端对这种可溶性/不溶性Aβ混合物进行成像，并与磷酸盐缓冲盐水（PBS）对照进行比较（每组n = 10个感兴趣区域）。在体内条件下，使用5xFAD转基因小鼠模型，并在6个月（n = 9）、12个月（n = 9）和17个月（n = 8）时对视网膜进行成像，以年龄匹配的野生型同窝小鼠作为对照（分别为n = 12、n = 13、n = 15）。在体外条件下，溶液的高光谱成像显示与载体相比反射率更高（p < 0.01），最大差异出现在短可见光谱（< 500nm）中。在体内制剂中，5xFAD在所有年龄（6、12、17个月，p < 0.01）均显示出更高的高光谱反射率。这些差异在较年轻时的短波长处最为明显，随着年龄的增长，在较长波长（~ 550nm）处出现了一个额外的峰值。这项研究表明，Aβ（可溶性/不溶性混合物）的存在可以在体外和体内增加高光谱反射率特征。体外在短波长光谱（< 500nm）中差异明显，并且在体内条件下通过眼介质成像时这些差异得以保留。随着年龄的增长，在~ 550nm附近的第二个峰值变得更加明显。视网膜的高光谱成像不需要使用造影剂，是一种对AD潜在有用的非侵入性生物标志物。
