Abstract：
Uncovering the molecular changes at the site where Aβ is deposited plays a critical role in advancing the diagnosis and treatment of Alzheimer\'s disease. However, there is currently a lack of a suitable label-free imaging method with a high spatial resolution for brain tissue analysis. In this study, we propose a modified desorption electrospray ionization (DESI) mass spectrometry imaging (MSI) method, called segmented temperature-controlled DESI (STC-DESI), to achieve high-resolution and high-sensitivity spatial metabolomics observation by precisely controlling desorption and ionization temperatures. By concentrating the spray plume and accelerating solvent evaporation at different temperatures, we achieved an impressive spatial resolution of 20 μm that enables direct observation of the heterogeneity around a single cell or an individual Aβ plaque and an exciting sensitivity that allows a variety of low-abundance metabolites and less ionizable neutral lipids to be detected. We applied this STC-DESI method to analyze the brains of transgenic AD mice and identified molecular changes associated with individual Aβ aggregates. More importantly, our study provides the first evidence that carnosine is significantly depleted and 5-caffeoylquinic acid (5-CQA) levels rise sharply around Aβ deposits. These observations highlight the potential of carnosine as a sensitive molecular probe for clinical magnetic resonance imaging diagnosis and the potential of 5-CQA as an efficient therapeutic strategy for Aβ clearance in the early AD stage. Overall, our findings demonstrate the effectiveness of our STC-DESI method and shed light on the potential roles of these molecules in AD pathology, specifically in cellular endocytosis, gray matter network disruption, and paravascular Aβ clearance.
摘要：
揭示Aβ沉积位点的分子变化对推进阿尔茨海默病的诊断和治疗起着至关重要的作用。然而,目前缺乏一种适用于脑组织分析的具有高空间分辨率的无标记成像方法.在这项研究中,我们提出了一种改进的解吸电喷雾电离(DESI)质谱成像(MSI)方法，称为分段温度控制DESI（STC-DESI），通过精确控制解吸和电离温度，实现高分辨率和高灵敏度的空间代谢组学观察。通过浓缩喷雾羽流并在不同温度下加速溶剂蒸发，我们获得了20μm的令人印象深刻的空间分辨率,能够直接观察单个细胞或单个Aβ斑块周围的异质性,并且具有令人兴奋的灵敏度,能够检测到多种低丰度代谢物和电离性较低的中性脂质.我们应用这种STC-DESI方法分析了转基因AD小鼠的大脑，并鉴定了与单个Aβ聚集体相关的分子变化。更重要的是,我们的研究提供了第一个证据，表明肌肽显着耗尽，并且5-咖啡酰基奎尼酸（5-CQA）水平在Aβ沉积物周围急剧上升。这些观察结果突出了肌肽作为临床磁共振成像诊断的敏感分子探针的潜力以及5-CQA作为早期AD阶段Aβ清除的有效治疗策略的潜力。总的来说,我们的研究结果证明了我们的STC-DESI方法的有效性，并揭示了这些分子在AD病理学中的潜在作用，特别是在细胞内吞作用中，灰质网络中断，血管旁Aβ清除。
