Matrix Assisted Laser Desorption Ionization Imaging Mass Spectrometry Of Biological Tissue Sections And Its Applications

First of all, Imaging Mass Spectrometry (IMS) methodology for biological tissue component distribution investigation, using matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS), was established. The protocols of fresh tissue storage and slicing for imaging purpose were investigated. MALDI matrix selection, its concentration, deposition protocol were optimized, a specific matrix spraying device was built up and MS data acquisition parameters were screened and optimized as followed: 15mg/mL of sinapinic acid, 15μm of slice thickness, 200μm of matrix dot distance, 30%—50% of laser power and 200 shots per spectrum. Automatic processing of MS signals and MS peak statistics were setup. A software was finished for MS average spectrum and Hits value statistics which the commercial software could not carry out. Hits reflected the component distribution in tissues, Hits bigger, distribution larger. Correctness of imaging localization was validated by IMS of reference samples. More than 40,000 spectra from 250 tissue sections were acquired and reproducibility between several of species groups was greater than 80%.Secondly, Based on the methodology, we studied pulmonary edema and gastrointestinal stromal tumor by IMS.1.Control group (15 species) and pulmonary edema group (16 species) of SD rat were analyzed by IMS, 12 differentiately expressed components were detected by T-test (P<0.05), 3 of which were up-regulatory, others were down-regulatory, and up or down effects were dependent on molecular weight, which might be specific for rat pulmonary edema. Classification modeling was created based on the 12 differentiate components, 11 blind species were analyzed for model validation, accuracy was 91%.2.Control group (12 species) and Gastrointestinal stromal tumor group (12 species) of human were analyzed by IMS, 16 differentiately expressed components were detected by T-test (P<0.05), 9 of which were up-regulated, others were down-regulated, and up or down were related with molecular weight. Which might be special for Gastrointestinal stromal tumor. Classification model was created based on the 16 differentiate components, to validate it, 8 cases were analyzed in blind .The correct ratio was 100%.We finished the statistic analysis of 7000 MS images from three kinds of tissue sections, these tissues were the liver, pulmonary and Gastrointestinal stromal tumor. We got the following results: 1. Liver tissue: Complementary type, Higher relative intensity, Normal intensity. 2. Normal lung tissue: Meniscus, Higher relative intensity, Normal intensity. 3. Pulmonary edema: Bow-tie-type, Co-Bow-tie-type, Higher relative intensity. 4. Normal muscular tissue: Higher relative intensity, Peripheral type, Pauciform. 5. Gastrointestinal stromal tumor: Higher relative intensity, Marginal form, Pauciform. These distribution characters will be helpful for investigating the mechanism of disease development.