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In JoVE (1)
Other Publications (10)
- Angewandte Chemie (International Ed. in English)
- Molecular & Cellular Proteomics : MCP
- Analytical Chemistry
- Journal of Mass Spectrometry : JMS
- International Journal of Mass Spectrometry
- Nature Methods
- Journal of Proteome Research
- PloS One
- Analytical and Bioanalytical Chemistry
- Molecular & Cellular Proteomics : MCP
Articles by Malin Andersson in JoVE
JoVE Clinical and Translational Medicine
MALDI Imaging Mass Spectrometry of Neuropeptides in Parkinson's Disease
1Department of Pharmaceutical Biosciences, Uppsala University, 2Department of Chemical and Biological Engineering, Chalmers University of Technology
Dopamine replacement pharmacotherapy using L-DOPA is the most commonly used symptomatic treatment of Parkinson’s disease, but is accompanied by side effects including involuntary abnormal movements, termed dyskinesia 1. Here, a protocol for MALDI imaging mass spectrometry is presented that detects changes in rat brain neuropeptide levels related to dyskinesia.
Other articles by Malin Andersson on PubMed
A Novel Histology-directed Strategy for MALDI-MS Tissue Profiling That Improves Throughput and Cellular Specificity in Human Breast Cancer
We describe a novel tissue profiling strategy that improves the cellular specificity and analysis throughput of protein profiles obtained by direct MALDI analysis. The new approach integrates the cellular specificity of histology, the accuracy and reproducibility of robotic liquid dispensing, and the speed and objectivity of automated spectra acquisition. Traditional methodologies for preparing and analyzing tissue samples rely heavily on manual procedures, which for various reasons discussed, restrict cellular specificity and sample throughput. Here, a robotic spotter deposits micron-sized droplets of matrix precisely onto foci of normal mammary epithelium, ductal carcinoma in situ, invasive mammary cancer, and peritumoral stroma selected by a pathologist from high resolution histological images of sectioned human breast cancer samples. The location of each matrix spot was then determined and uploaded into the instrument to facilitate automated profile acquisition by MALDI-TOF. In the example shown, the different lesions were clearly differentiated using mass profiling. Further, the workflow permits a visual projection of any information produced from the profile analyses directly on the histological image for a unique combination of proteomic and histological assessment of sample regions. The higher performance characteristics offered by the new workflow promises to be a significant advancement toward the next generation of tissue profiling studies.
Direct Molecular Analysis of Whole-body Animal Tissue Sections by Imaging MALDI Mass Spectrometry
Imaging mass spectrometry (IMS) that utilizes matrix-assisted laser desorption/ionization (MALDI) technology can provide a molecular ex vivo view of resected organs or whole-body sections from an animal, making possible the label-free tracking of both endogenous and exogenous compounds with spatial resolution and molecular specificity. Drug distribution and, for the first time, individual metabolite distributions within whole-body tissue sections can be detected simultaneously at various time points following drug administration. IMS analysis of tissues from 8 mg/kg olanzapine dosed rats revealed temporal distribution of the drug and metabolites that correlate to previous quantitative whole-body autoradiography studies. Whole-body MALDI IMS is further extended to detecting proteins from organs present in a whole-body sagittal tissue section. This technology will significantly help advance the analysis of novel therapeutics and may provide deeper insight into therapeutic and toxicological processes, revealing at the molecular level the cause of efficacy or side effects often associated with drug administration.
Identification of Proteins Directly from Tissue: in Situ Tryptic Digestions Coupled with Imaging Mass Spectrometry
A novel method for on-tissue identification of proteins in spatially discrete regions is described using tryptic digestion followed by matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) with MS/MS analysis. IMS is first used to reveal the protein and peptide spatial distribution in a tissue section and then a serial section is robotically spotted with small volumes of trypsin solution to carry out in situ protease digestion. After hydrolysis, 2,5-Dihydroxybenzoic acid (DHB) matrix solution is applied to the digested spots, with subsequent analysis by IMS to reveal the spatial distribution of the various tryptic fragments. Sequence determination of the tryptic fragments is performed using on-tissue MALDI MS/MS analysis directly from the individual digest spots. This protocol enables protein identification directly from tissue while preserving the spatial integrity of the tissue sample. The procedure is demonstrated with the identification of several proteins in the coronal sections of a rat brain.
Processing MALDI Mass Spectra to Improve Mass Spectral Direct Tissue Analysis
Profiling and imaging biological specimens using MALDI mass spectrometry has significant potential to contribute to our understanding and diagnosis of disease. The technique is efficient and high-throughput providing a wealth of data about the biological state of the sample from a very simple and direct experiment. However, in order for these techniques to be put to use for clinical purposes, the approaches used to process and analyze the data must improve. This study examines some of the existing tools to baseline subtract, normalize, align, and remove spectral noise for MALDI data, comparing the advantages of each. A preferred workflow is presented that can be easily implemented for data in ASCII format. The advantages of using such an approach are discussed for both molecular profiling and imaging mass spectrometry.
Imaging Mass Spectrometry of Proteins and Peptides: 3D Volume Reconstruction
As large genomic and proteomic datasets are generated from homogenates of various tissues, the need for information on the spatial localization of their encoded products has become more pressing. Matrix-assisted laser desorption-ionization (MALDI) imaging mass spectrometry (IMS) offers investigators the means with which to unambiguously study peptides and proteins with molecular specificity, and to determine their distribution in two and three dimensions. In the past few years, several parameters have been optimized for IMS, including sample preparation, matrix application and instrumental acquisition parameters (Box 1). These developments have resulted in a high degree of reproducibility in mass accuracy and peak intensities (Supplementary Fig. 1 online). Recently, we have optimized our protocol to be able to increase the number of molecular species analyzed by collecting two sets of sections, covering one set of sections with sinapinic acid for optimal detection of proteins and adjacent sections with 2,5-dihydroxybenzoic acid (DHB) matrix for the optimal detection of low-mass species, including peptides. Approximately 1,000 peaks can be observed in each dataset (Fig. 1). Furthermore, the sections are collected at an equal distance, 200 mum instead of 400-500 mum used previously, thus enabling the use of virtual z-stacks and three-dimensional (3D) volume renderings to investigate differential localization patterns in much smaller brain structures such as the substantia nigra and the interpeduncular nucleus. Here we present our optimized step-by-step procedure based on previous work in our laboratory, describing how to make 3D volume reconstructions of MALDI IMS data, as applied to the rat brain.
Heat Stabilization of the Tissue Proteome: a New Technology for Improved Proteomics
After tissue or body fluid sampling, proteases and other protein-modifying enzymes can rapidly change composition of the proteome. As a direct consequence, analytical results will reflect a mix of in vivo proteome and ex vivo degradation products. Vital information about the presampling state may be destroyed or distorted, leading to variation between samples and incorrect conclusions. Sample stabilization and standardization of sample handling can reduce or eliminate this problem. Here, a novel tissue stabilization system which utilizes a combination of heat and pressure under vacuum was used to stop degradation in mouse brain tissue immediately after sampling. It was found by biochemical assays that enzymatic activity was reduced to background levels in stabilized samples. Western blot analysis confirmed that post-translational phosphorylations of analyzed proteins were stable and conserved for up to 2 h at room temperature and that peptide extracts were devoid of abundant protein degradation fragments. The combination of reduced complexity and proteolytic inactivation enabled mass spectrometric identification of several neuropeptides and endogenous peptides including modified species at higher levels compared to nonstabilized samples. The tissue stabilizing system ensures reproducible and rapid inactivation of enzymes. Therefore, the system provides a powerful improvement to proteomics by greatly reducing the complexity and dynamic range of the proteome in tissue samples and enables enhanced possibilities for discovery and analysis of clinically relevant protein/peptide biomarkers.
Fine Mapping the Spatial Distribution and Concentration of Unlabeled Drugs Within Tissue Micro-compartments Using Imaging Mass Spectrometry
Readouts that define the physiological distributions of drugs in tissues are an unmet challenge and at best imprecise, but are needed in order to understand both the pharmacokinetic and pharmacodynamic properties associated with efficacy. Here we demonstrate that it is feasible to follow the in vivo transport of unlabeled drugs within specific organ and tissue compartments on a platform that applies MALDI imaging mass spectrometry to tissue sections characterized with high definition histology. We have tracked and quantified the distribution of an inhaled reference compound, tiotropium, within the lungs of dosed rats, using systematic point by point MS and MS/MS sampling at 200 microm intervals. By comparing drug ion distribution patterns in adjacent tissue sections, we observed that within 15 min following exposure, tiotropium parent MS ions (mass-to-charge; m/z 392.1) and fragmented daughter MS/MS ions (m/z 170.1 and 152.1) were dispersed in a concentration gradient (80 fmol-5 pmol) away from the central airways into the lung parenchyma and pleura. These drug levels agreed well with amounts detected in lung compartments by chemical extraction. Moreover, the simultaneous global definition of molecular ion signatures localized within 2-D tissue space provides accurate assignment of ion identities within histological landmarks, providing context to dynamic biological processes occurring at sites of drug presence. Our results highlight an important emerging technology allowing specific high resolution identification of unlabeled drugs at sites of in vivo uptake and retention.
MALDI Mass Spectrometry Based Molecular Phenotyping of CNS Glial Cells for Prediction in Mammalian Brain Tissue
The development of powerful analytical techniques for specific molecular characterization of neural cell types is of central relevance in neuroscience research for elucidating cellular functions in the central nervous system (CNS). This study examines the use of differential protein expression profiling of mammalian neural cells using direct analysis by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). MALDI-MS analysis is rapid, sensitive, robust, and specific for large biomolecules in complex matrices. Here, we describe a newly developed and straightforward methodology for direct characterization of rodent CNS glial cells using MALDI-MS-based intact cell mass spectrometry (ICMS). This molecular phenotyping approach enables monitoring of cell growth stages, (stem) cell differentiation, as well as probing cellular responses towards different stimulations. Glial cells were separated into pure astroglial, microglial, and oligodendroglial cell cultures. The intact cell suspensions were then analyzed directly by MALDI-TOF-MS, resulting in characteristic mass spectra profiles that discriminated glial cell types using principal component analysis. Complementary proteomic experiments revealed the identity of these signature proteins that were predominantly expressed in the different glial cell types, including histone H4 for oligodendrocytes and S100-A10 for astrocytes. MALDI imaging MS was performed, and signature masses were employed as molecular tracers for prediction of oligodendroglial and astroglial localization in brain tissue. The different cell type specific protein distributions in tissue were validated using immunohistochemistry. ICMS of intact neuroglia is a simple and straightforward approach for characterization and discrimination of different cell types with molecular specificity.
L-DOPA-induced Dyskinesia is Associated with Regional Increase of Striatal Dynorphin Peptides As Elucidated by Imaging Mass Spectrometry
Opioid peptides are involved in various pathophysiological processes, including algesia, epilepsy, and drug dependence. A strong association between L-DOPA-induced dyskinesia (LID) and elevated prodynorphin mRNA levels has been established in both patients and in animal models of Parkinson's disease, but to date the endogenous prodynorphin peptide products have not been determined. Here, matrix-assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) was used for characterization, localization, and relative quantification of striatal neuropeptides in a rat model of LID in Parkinson's disease. MALDI IMS has the unique advantage of high sensitivity and high molecular specificity, allowing comprehensive detection of multiple molecular species in a single tissue section. Indeed, several dynorphins and enkephalins could be detected in the present study, including dynorphin A(1-8), dynorphin B, α-neoendorphin, MetEnkRF, MetEnkRGL, PEnk (198-209, 219-229). IMS analysis revealed elevated levels of dynorphin B, α-neoendorphin, substance P, and PEnk (220-229) in the dorsolateral striatum of high-dyskinetic animals compared with low-dyskinetic and lesion-only control rats. Furthermore, the peak-intensities of the prodynorphin derived peptides, dynorphin B and α-neoendorphin, were strongly and positively correlated with LID severity. Interestingly, these LID associated dynorphin peptides are not those with high affinity to κ opioid receptors, but are known to bind and activate also μ- and Δ-opioid receptors. In addition, the peak intensities of a novel endogenous metabolite of α-neoendorphin lacking the N-terminal tyrosine correlated positively with dyskinesia severity. MALDI IMS of striatal sections from Pdyn knockout mice verified the identity of fully processed dynorphin peptides and the presence of endogenous des-tyrosine α-neoendorphin. Des-tyrosine dynorphins display reduced opioid receptor binding and this points to possible novel nonopioid receptor mediated changes in the striatum of dyskinetic rats. Because des-tyrosine dynorphins can only be detected by mass spectrometry, as no antibodies are available, these findings highlight the importance of MALDI IMS analysis for the study of molecular dynamics in neurological diseases.
