Tissue Imaging Using Desorption Electrospray Ionization Mass Spectrometry

描述（由申请方提供）：我们建议通过直接检查未处理的组织切片来研究脂质在脊髓组织中及其附近的分布。目的是绘制健康小鼠和神经退行性疾病动物髓鞘脂质特征的分布图。预计将出现极性较低的脂质分布差异，并且可能是疾病状态的特征，但神经内和神经附近的空间分布以及将观察到的化合物的确切性质尚不清楚，由于以前的测量要么是用具有有限分子识别能力的光谱方法进行的可以使用常规方法（例如汽车）或具有严重有限的空间分辨率（例如提取，然后LC-ESI-MS）来进行。该研究的一个目的是通过化学成分的变化来识别病变，并将与病变相关的结构和化学变化相关联。这将通过现有的光学方法，特别是相干反斯托克斯拉曼光谱（汽车）与新的环境质谱方法的组合来实现。这些实验将需要开发高分辨率（约10微米）的解吸电喷雾电离质谱成像能力。质谱是一种环境电离方法，允许对组织切片进行快速和直接的化学分析，而无需事先进行样品处理。为了检测组织基质中具有高灵敏度的脂质，需要开发反应性DESI的能力;该方法涉及使用电荷标记试剂对脂质进行原位局部衍生化，该试剂被喷雾溶剂带到被询问的点。串联质谱法将用于进一步提高目标脂质检测的特异性。MS/MS化学成像过程中获得的大量分子信息需要使用先进的数据处理方法进行全面分析，并将实施数据表示和可视化、数据搜索和图像比较的新技术。在较低空间分辨率下的初步工作中，已经证明了EST-MS允许通过极性脂质（特别是磷脂）的空间分布来区分组织的肿瘤和非肿瘤切片。虽然这项技术有许多潜在的应用，涉及在体外和体内的生物系统的化学分析，在这个R21的应用，我们专注于技术开发，旨在提供所需的空间和化学信息来表征神经变性，特别是脱髓鞘。公共卫生相关性：建议开发新的成像方法，可用于识别脂质和其他化学物质，这些化学物质可作为生物标志物，以跟踪多发性硬化症（MS）等神经疾病过程中发生的基本过程。将寻求有关神经鞘中化学变化的具体信息，以便将来对神经疾病进行诊断和预后。

DESCRIPTION (provided by applicant): We propose to investigate the distribution of lipids in and near spinal cord tissue using direct examination of untreated tissue sections. The aim is to map the distribution of lipids characteristic of the myelin sheath in healthy mice and in animals with neural degenerative disease. It is expected that differences in less polar lipid distributions will occur and might be characteristic of disease state, but the spatial distribution in and near the nerves and the exact nature of the compounds that will be observed is unknown, since previous measurements have either been made with spectroscopic methods with limited molecular recognition capabilities (e.g. CARS) or with severely limited spatial resolution (e.g. extraction followed by LC-ESI-MS). One aim of the study is to identify lesions through changes in chemical composition and to correlate structural and chemical changes associated with lesions. This will be achieved by a combination of existing optical methods, especially coherent anti-Stokes raman spectroscopy (CARS) with new ambient mass spectrometry methods. The experiments will require the development of a high resolution (ca 10 micron) imaging capability for desorption electrospray ionization mass spectrometry (DESI-MS). DESI-MS is an ambient ionization method that allows rapid and direct chemical analysis of tissue sections with no prior sample treatment. In order to detect lipids with high sensitivity in the tissue matrix, capabilities for reactive DESI will need to be developed; this method involving in situ localized derivatization of the lipid using a charge-labeled reagent which is carried to the spot being interrogated by the spray solvent. Tandem mass spectrometry will be used to further improve the specificity of detection of the lipids of interest. The large amounts of molecular information obtained during MS/MS chemical imaging require comprehensive analysis using advanced data processing methods and new techniques for data representation and visualization, data searching and image comparisons will be implemented. In preliminary work at lower spatial resolution, DESI-MS has been demonstrated to allow differentiation of tumor and non-tumor sections of tissue through spatial distributions of polar lipids, especially phospholipids. Although this technique has many potential applications involving in-vitro and in-vivo chemical analysis for biological systems, in this R21 application, we concentrate on technology development aimed at providing the spatial and chemical information needed t characterize neural degeneration and specifically demyelin. PUBLIC HEALTH RELEVANCE: It is proposed to develop new imaging methods which can be used to identify lipids and other chemicals that might serve as biomarkers to follow the fundamental processes occurring in the course of neural diseases like multiple sclerosis (MS). Specific information on the chemical changes in the nerve sheath will be sought in order to allow future diagnosis and prognosis of neural diseases.