大鼠骨关节组织的敞开式质谱成像分析方法研究

Development of an Ambient Mass Spectrometry Imaging Method for Rat Joint Tissues

  • 摘要: 哺乳动物骨关节代谢异常与风湿性关节炎、类风湿性关节炎和骨关节炎等多种疾病密切相关。因此,研发适用于骨关节组织中代谢物可视化分析的质谱成像方法,对于深入理解生理病理条件下骨关节组织不同微区的代谢特征具有重要意义。本文采用空气动力辅助解吸电喷雾离子化质谱成像(airflow-assisted desorption electrospray ionization-mass spectrometry imaging,AFADESI-MSI)技术,以代谢物的检出数量、响应强度和成像效果为主要评价指标,通过对骨关节组织样品切片制备方法、切片厚度和喷雾溶剂系统进行优化,建立了大鼠骨关节组织的敞开式质谱成像分析方法。考察相邻的6张大鼠膝关节组织切片,代表性代谢物响应强度的相对标准偏差均小于20%,表明该方法的重复性良好。进一步采用该方法对大鼠膝关节组织进行空间分辨代谢组学分析,发现骨质中磷酸戊糖途径、乙醛酸和二羧酸酯代谢、TCA循环等代谢通路更为显著;骨髓中抗坏血酸代谢与嘌呤代谢通路更为显著;软骨中精氨酸、脯氨酸代谢以及赖氨酸降解等氨基酸代谢通路更为显著。上述结果表明,大鼠膝关节组织不同微区具有明显的代谢异质性。本文建立的AFADESI-MSI方法适用于大鼠骨关节组织分析,为骨关节组织的代谢研究提供了可视化分析的技术手段。

     

    Abstract: Metabolic abnormalities in mammalian joint tissues are closely linked to various diseases, including rheumatoid arthritis and osteoarthritis. The variations of small molecule metabolites within bone joint tissues can affect cell proliferation, drive the secretion of inflammatory mediators, mediate leukocyte infiltration, and consequently induce synovial inflammation and cartilage damage. Therefore, the development of novel mass spectrometry imaging (MSI) methods for visualizing metabolites in joint tissues is crucial for comprehensively understanding the metabolic characteristics of different microregions under both physiological and pathological conditions. In this study, an airflow-assisted desorption electrospray ionization (AFADESI)-MSI was used to establish an ambient MSI method for rat joint tissues. To ensure the effectiveness of the method, dynamic range, sensitivity, and imaging effect were selected as the primary evaluation criteria. The tissue preparation, section thickness, and spray solvent systems were systematically optimized. Compared to the AB glue transfer method, the tape adhesion method can obtain complete bone joint tissue sections and clearer images. A section thickness of 20 μm, as opposed to 15 μm, provides higher ion intensity in the m/z 600-900 range. Among the tested spray solvent systems, compared with methanol-water (8:2, V/V), acetonitrile-water (8:2, V/V), and the acetonitrile-isopropanol-water (6:2:2, V/V/V), the acetonitrile-isopropanol-water (4:4:2, V/V/V) prove to be the most effective, detecting the highest number of metabolites and lipids when employed as the spray solvent. The precision of this method was evaluated on six adjacent rat knee sections under positive and negative ion modes, with the relative standard deviation (RSD) for the ion intensity of representative metabolites being less than 20%. Subsequently, this method was utilized for spatially resolved metabolomics analysis of rat knee tissues. A total of 613 metabolites are annotated in the overall knee tissues. Based on the optical images, the rat knee tissues were segmented into three microregions for bone, marrow, and cartilage. 452, 418, and 451 metabolites in these microregions are identified, respectively. In bone, the pentose phosphate pathway, glyoxylate and dicarboxylate metabolism, and the TCA cycle are more prominent. In bone marrow, ascorbate and purine metabolism pathways are more significant. In cartilage, arginine and proline metabolism, as well as lysine degradation, are more pronounced. These findings highlight significant metabolic heterogeneity across different microregions of rat knee joint tissues. Overall, this study develops an AFADESI-MSI method for in-depth profiling of metabolites within rat joint tissues, providing a powerful tool for in situ visualization of metabolites in metabolic studies of joint tissues.

     

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