Hotchkiss Brain Institute, Department of Clinical Neurosciences, Cumming School of Medicine, University of Calgary, Calgary AB, Canada.
Amira Medical Technologies Inc., Calgary, AB, Canada.
J Alzheimers Dis. 2022;85(4):1721-1734. doi: 10.3233/JAD-215402.
Toxic amyloid-β (Aβ) peptides aggregate into higher molecular weight assemblies and accumulate not only in the extracellular space, but also in the walls of blood vessels in the brain, increasing their permeability, and promoting immune cell migration and activation. Given the prominent role of the immune system, phagocytic blood cells may contact pathological brain materials.
To develop a novel method for early Alzheimer's disease (AD) detection, we used blood leukocytes, that could act as "sentinels" after trafficking through the brain microvasculature, to detect pathological amyloid by labelling with a conformationally-sensitive fluorescent amyloid probe and imaging with confocal spectral microscopy.
Formalin-fixed peripheral blood mononuclear cells (PBMCs) from cognitively healthy control (HC) subjects, mild cognitive impairment (MCI) and AD patients were stained with the fluorescent amyloid probe K114, and imaged. Results were validated against cerebrospinal fluid (CSF) biomarkers and clinical diagnosis.
K114-labeled leukocytes exhibited distinctive fluorescent spectral signatures in MCI/AD subjects. Comparing subjects with single CSF biomarker-positive AD/MCI to negative controls, our technique yielded modest AUCs, which improved to the 0.90 range when only MCI subjects were included in order to measure performance in an early disease state. Combining CSF Aβ42 and t-Tau metrics further improved the AUC to 0.93.
Our method holds promise for sensitive detection of AD-related protein misfolding in circulating leukocytes, particularly in the early stages of disease.
有毒的淀粉样β（Aβ）肽聚集成更高分子量的聚集体，不仅在细胞外空间积累，而且在大脑血管壁中积累，增加血管壁的通透性，并促进免疫细胞的迁移和激活。鉴于免疫系统的突出作用，吞噬性血细胞可能会接触到病理性脑组织物质。
为了开发一种早期阿尔茨海默病（AD）检测的新方法，我们使用血液白细胞，白细胞可以通过脑微血管转运后充当“哨兵”，通过用构象敏感的荧光淀粉样蛋白探针标记并通过共焦光谱显微镜成像来检测病理性淀粉样蛋白。
用荧光淀粉样蛋白探针 K114 对认知健康对照（HC）受试者、轻度认知障碍（MCI）和 AD 患者的福尔马林固定外周血单核细胞（PBMC）进行染色，并进行成像。结果与脑脊液（CSF）生物标志物和临床诊断进行了验证。
在 MCI/AD 受试者中，K114 标记的白细胞表现出独特的荧光光谱特征。与仅单个 CSF 生物标志物阳性 AD/MCI 受试者相比，我们的技术产生的 AUC 值适中，当仅包括 MCI 受试者以测量早期疾病状态下的性能时，AUC 值提高到 0.90 范围。将 CSF Aβ42 和 t-Tau 指标结合使用进一步将 AUC 提高到 0.93。
我们的方法有望在循环白细胞中敏感地检测到与 AD 相关的蛋白质错误折叠，特别是在疾病的早期阶段。
