Publications by authors named "Ron M A Heeren"

221 Publications

Heterogeneity of Lipid and Protein Cartilage Profiles Associated with Human Osteoarthritis with or without Type 2 Diabetes Mellitus.

J Proteome Res 2021 May 17;20(5):2973-2982. Epub 2021 Apr 17.

Division of Imaging Mass Spectrometry, Maastricht MultiModal Molecular Imaging (M4i) Institute, 6229 ER Maastricht, Netherlands.

Osteoarthritis (OA) is a multifactorial pathology and comprises a wide range of distinct phenotypes. In this context, the characterization of the different molecular profiles associated with each phenotype can improve the classification of OA. In particular, OA can coexist with type 2 diabetes mellitus (T2DM). This study investigates lipidomic and proteomic differences between human OA/T2DM and OA/T2DM cartilage through a multimodal mass spectrometry approach. Human cartilage samples were obtained after total knee replacement from OA/T2DM and OA/T2DM patients. Label-free proteomics was employed to study differences in protein abundance and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) for spatially resolved-lipid analysis. Label-free proteomic analysis showed differences between OA/T2DM and OA/T2DM phenotypes in several metabolic pathways such as lipid regulation. Interestingly, phospholipase A2 protein was found increased within the OA/T2DM cohort. In addition, MALDI-MSI experiments revealed that phosphatidylcholine and sphingomyelin species were characteristic of the OA/T2DM group, whereas lysolipids were more characteristic of the OA/T2DM phenotype. The data also pointed out differences in phospholipid content between superficial and deep layers of the cartilage. Our study shows distinctively different lipid and protein profiles between OA/T2DM and OA/T2DM human cartilage, demonstrating the importance of subclassification of the OA disease for better personalized treatments.
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http://dx.doi.org/10.1021/acs.jproteome.1c00186DOI Listing
May 2021

Quantitative mass spectrometry imaging of drugs and metabolites: a multiplatform comparison.

Anal Bioanal Chem 2021 Apr 26;413(10):2779-2791. Epub 2021 Mar 26.

Maastricht MultiModal Molecular Imaging (M4i) Institute, Division of Imaging Mass Spectrometry, Maastricht University, 6229 ER, Maastricht, The Netherlands.

Mass spectrometry imaging (MSI) provides insight into the molecular distribution of a broad range of compounds and, therefore, is frequently applied in the pharmaceutical industry. Pharmacokinetic and toxicological studies deploy MSI to localize potential drugs and their metabolites in biological tissues but currently require other analytical tools to quantify these pharmaceutical compounds in the same tissues. Quantitative mass spectrometry imaging (Q-MSI) is a field with challenges due to the high biological variability in samples combined with the limited sample cleanup and separation strategies available prior to MSI. In consequence, more selectivity in MSI instruments is required. This can be provided by multiple reaction monitoring (MRM) which uses specific precursor ion-product ion transitions. This targeted approach is in particular suitable for pharmaceutical compounds because their molecular identity is known prior to analysis. In this work, we compared different analytical platforms to assess the performance of MRM detection compared to other MS instruments/MS modes used in a Q-MSI workflow for two drug candidates (A and B). Limit of detection (LOD), linearity, and precision and accuracy of high and low quality control (QC) samples were compared between MS instruments/modes. MRM mode on a triple quadrupole mass spectrometer (QqQ) provided the best overall performance with the following results for compounds A and B: LOD 35.5 and 2.5 μg/g tissue, R 0.97 and 0.98 linearity, relative standard deviation QC <13.6%, and 97-112% accuracy. Other MS modes resulted in LOD 6.7-569.4 and 2.6-119.1 μg/g tissue, R 0.86-0.98 and 0.86-0.98 linearity, relative standard deviation QC < 19.4 and < 37.5%, and 70-356% and 64-398% accuracy for drug candidates A and B, respectively. In addition, we propose an optimized 3D printed mimetic tissue model to increase the overall analytical throughput of our approach for large animal studies. The MRM imaging platform was applied as proof-of-principle for quantitative detection of drug candidates A and B in four dog livers and compared to LC-MS. The Q-MSI concentrations differed <3.5 times with the concentrations observed by LC-MS. Our presented MRM-based Q-MSI approach provides a more selective and high-throughput analytical platform due to MRM specificity combined with an optimized 3D printed mimetic tissue model.
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http://dx.doi.org/10.1007/s00216-021-03210-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8007509PMC
April 2021

Apocryphal FADS2 activity promotes fatty acid diversification in cancer.

Cell Rep 2021 Feb;34(6):108738

School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD 4000, Australia; Central Analytical Research Facility, Institute for Future Environments, Queensland University of Technology, 2 George St., Brisbane, QLD 4000, Australia. Electronic address:

Canonical fatty acid metabolism describes specific enzyme-substrate interactions that result in products with well-defined chain lengths, degree(s), and positions of unsaturation. Deep profiling of lipids across a range of prostate cancer cell lines reveals a variety of fatty acids with unusual site(s) of unsaturation that are not described by canonical pathways. The structure and abundance of these unusual lipids correlate with changes in desaturase expression and are strong indicators of cellular phenotype. Gene silencing and stable isotope tracing demonstrate that direct Δ6 and Δ8 desaturation of 14:0 (myristic), 16:0 (palmitic), and 18:0 (stearic) acids by FADS2 generate new families of unsaturated fatty acids (including n-8, n-10, and n-12) that have rarely-if ever-been reported in human-derived cells. Isomer-resolved lipidomics reveals the selective incorporation of these unusual fatty acids into complex structural lipids and identifies their presence in cancer tissues, indicating functional roles in membrane structure and signaling.
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http://dx.doi.org/10.1016/j.celrep.2021.108738DOI Listing
February 2021

Molecular cellophane.

Authors:
Ron M A Heeren

Nat Methods 2021 03;18(3):242-243

M4I, the Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Maastricht, the Netherlands.

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http://dx.doi.org/10.1038/s41592-021-01064-zDOI Listing
March 2021

Batch Effects in MALDI Mass Spectrometry Imaging.

J Am Soc Mass Spectrom 2021 Mar 1;32(3):628-635. Epub 2021 Feb 1.

Maastricht MultiModal Molecular Imaging Institute (M4i), Maastricht University, 6229 ER Maastricht, The Netherlands.

Mass spectrometry imaging (MSI) has become an indispensible tool for spatially resolved molecular investigation of tissues. One of the key application areas is biomedical research, where matrix-assisted laser desorption/ionization (MALDI) MSI is predominantly used due to its high-throughput capability, flexibility in the molecular class to investigate, and ability to achieve single cell spatial resolution. While many of the initial technical challenges have now been resolved, so-called batch effects, a phenomenon already known from other omics fields, appear to significantly impede reliable comparison of data from particular midsized studies typically performed in translational clinical research. This critical insight will discuss at what levels (pixel, section, slide, time, and location) batch effects can manifest themselves in MALDI-MSI data and what consequences this might have for biomarker discovery or multivariate classification. Finally, measures are presented that could be taken to recognize and/or minimize these potentially detrimental effects, and an outlook is provided on what is still needed to ultimately overcome these effects.
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http://dx.doi.org/10.1021/jasms.0c00393DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7944567PMC
March 2021

Spatial differentiation of metabolism in prostate cancer tissue by MALDI-TOF MSI.

Cancer Metab 2021 Jan 29;9(1). Epub 2021 Jan 29.

Department of Circulation and Medical Imaging, NTNU-Norwegian University of Science and Technology, Trondheim, Norway.

Background: Prostate cancer tissues are inherently heterogeneous, which presents a challenge for metabolic profiling using traditional bulk analysis methods that produce an averaged profile. The aim of this study was therefore to spatially detect metabolites and lipids on prostate tissue sections by using mass spectrometry imaging (MSI), a method that facilitates molecular imaging of heterogeneous tissue sections, which can subsequently be related to the histology of the same section.

Methods: Here, we simultaneously obtained metabolic and lipidomic profiles in different prostate tissue types using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MSI. Both positive and negative ion mode were applied to analyze consecutive sections from 45 fresh-frozen human prostate tissue samples (N = 15 patients). Mass identification was performed with tandem MS.

Results: Pairwise comparisons of cancer, non-cancer epithelium, and stroma revealed several metabolic differences between the tissue types. We detected increased levels of metabolites crucial for lipid metabolism in cancer, including metabolites involved in the carnitine shuttle, which facilitates fatty acid oxidation, and building blocks needed for lipid synthesis. Metabolites associated with healthy prostate functions, including citrate, aspartate, zinc, and spermine had lower levels in cancer compared to non-cancer epithelium. Profiling of stroma revealed higher levels of important energy metabolites, such as ADP, ATP, and glucose, and higher levels of the antioxidant taurine compared to cancer and non-cancer epithelium.

Conclusions: This study shows that specific tissue compartments within prostate cancer samples have distinct metabolic profiles and pinpoint the advantage of methodology providing spatial information compared to bulk analysis. We identified several differential metabolites and lipids that have potential to be developed further as diagnostic and prognostic biomarkers for prostate cancer. Spatial and rapid detection of cancer-related analytes showcases MALDI-TOF MSI as a promising and innovative diagnostic tool for the clinic.
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http://dx.doi.org/10.1186/s40170-021-00242-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7847144PMC
January 2021

Real-time lipid patterns to classify viable and necrotic liver tumors.

Lab Invest 2021 03 22;101(3):381-395. Epub 2021 Jan 22.

Maastricht MultiModal Molecular Imaging Institute (M4i), University of Maastricht, Maastricht, The Netherlands.

Real-time tissue classifiers based on molecular patterns are emerging tools for fast tumor diagnosis. Here, we used rapid evaporative ionization mass spectrometry (REIMS) and multivariate statistical analysis (principal component analysis-linear discriminant analysis) to classify tissues with subsequent comparison to gold standard histopathology. We explored whether REIMS lipid patterns can identify human liver tumors and improve the rapid characterization of their underlying metabolic features. REIMS-based classification of liver parenchyma (LP), hepatocellular carcinoma (HCC), and metastatic adenocarcinoma (MAC) reached an accuracy of 98.3%. Lipid patterns of LP were more similar to those of HCC than to those of MAC and allowed clear distinction between primary and metastatic liver tumors. HCC lipid patterns were more heterogeneous than those of MAC, which is consistent with the variation seen in the histopathological phenotype. A common ceramide pattern discriminated necrotic from viable tumor in MAC with 92.9% accuracy and in other human tumors. Targeted analysis of ceramide and related sphingolipid mass features in necrotic tissues may provide a new classification of tumor cell death based on metabolic shifts. Real-time lipid patterns may have a role in future clinical decision-making in cancer precision medicine.
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http://dx.doi.org/10.1038/s41374-020-00526-wDOI Listing
March 2021

Quantitative Mass Spectrometry Imaging to Study Drug Distribution in the Intestine Following Oral Dosing.

Anal Chem 2021 02 20;93(4):2144-2151. Epub 2021 Jan 20.

Maastricht MultiModal Molecular Imaging Institute, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands.

Local delivery to the lower gut to treat diseases of the colon has become a topic of special attention. Tissue exposure of locally acting agents is not represented by plasma concentrations. Therefore, reliable methods to measure tissue uptake at the primary site of action (e.g., epithelial layer or lamina propria) are vital. This work investigates the suitability of mass spectrometry imaging (MSI) in quantitatively visualizing intestinal transmural drug distribution. Tofacitinib (Tofa), a drug approved for the treatment of several autoimmune diseases, including ulcerative colitis, was selected as a tool compound for feasibility studies. One- and 7-h postdose sections of the ileum, proximal- and distal-colon from rats that received an oral solution of Tofa were subjected to matrix-assisted laser desorption ionization (MALDI)-MSI. A dilution series of individual concentrations sprayed over an entire tissue section allowed for tissue type-specific quantitation. At 1 h (systemic ), the signal was highest in the ileum, whereas at 7 h, the signal was highest in the colon, when the unabsorbed fraction of the compound reached the colon. A combination of three-dimensional (3D) intensity plots and hematoxylin and eosin (H&E) stains showed a visually observable gradual decrease in Tofa concentration from the lumen toward the muscular layer of the proximal colon. The high luminal concentration of Tofa indicated that flushing of the intestines with saline does not result in complete removal of the drug material from the lumen. This could cause an overestimation of drug concentration in gut tissue homogenates by conventional liquid chromatography-mass spectrometry (LC-MS) methods. This study demonstrates the utility of MSI to differentiate between the lumen and intestinal wall layers and enables proper interpretation of tissue distribution data.
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http://dx.doi.org/10.1021/acs.analchem.0c03956DOI Listing
February 2021

Proteomics analysis of human intestinal organoids during hypoxia and reoxygenation as a model to study ischemia-reperfusion injury.

Cell Death Dis 2021 Jan 18;12(1):95. Epub 2021 Jan 18.

Department of Surgery, Maastricht University Medical Centre; NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht, The Netherlands.

Intestinal ischemia-reperfusion (IR) injury is associated with high mortality rates, which have not improved in the past decades despite advanced insight in its pathophysiology using in vivo animal and human models. The inability to translate previous findings to effective therapies emphasizes the need for a physiologically relevant in vitro model to thoroughly investigate mechanisms of IR-induced epithelial injury and test potential therapies. In this study, we demonstrate the use of human small intestinal organoids to model IR injury by exposing organoids to hypoxia and reoxygenation (HR). A mass-spectrometry-based proteomics approach was applied to characterize organoid differentiation and decipher protein dynamics and molecular mechanisms of IR injury in crypt-like and villus-like human intestinal organoids. We showed successful separation of organoids exhibiting a crypt-like proliferative phenotype, and organoids exhibiting a villus-like phenotype, enriched for enterocytes and goblet cells. Functional enrichment analysis of significantly changing proteins during HR revealed that processes related to mitochondrial metabolism and organization, other metabolic processes, and the immune response were altered in both organoid phenotypes. Changes in protein metabolism, as well as mitophagy pathway and protection against oxidative stress were more pronounced in crypt-like organoids, whereas cellular stress and cell death associated protein changes were more pronounced in villus-like organoids. Profile analysis highlighted several interesting proteins showing a consistent temporal profile during HR in organoids from different origin, such as NDRG1, SDF4 or DMBT1. This study demonstrates that the HR response in human intestinal organoids recapitulates properties of the in vivo IR response. Our findings provide a framework for further investigations to elucidate underlying mechanisms of IR injury in crypt and/or villus separately, and a model to test therapeutics to prevent IR injury.
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http://dx.doi.org/10.1038/s41419-020-03379-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7813872PMC
January 2021

Mass spectrometry imaging of phosphatidylcholine metabolism in lungs administered with therapeutic surfactants and isotopic tracers.

J Lipid Res 2021 Jan 14;62:100023. Epub 2021 Jan 14.

Academic Unit of Clinical & Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom; National Institute for Health Research Southampton Biomedical Research Centre, University Hospital Southampton, Southampton, United Kingdom. Electronic address:

Mass spectrometry imaging (MSI) visualizes molecular distributions throughout tissues but is blind to dynamic metabolic processes. Here, MSI with high mass resolution together with multiple stable isotope labeling provided spatial analyses of phosphatidylcholine (PC) metabolism in mouse lungs. Dysregulated surfactant metabolism is central to many respiratory diseases. Metabolism and turnover of therapeutic pulmonary surfactants were imaged from distributions of intact and metabolic products of an added tracer, universally C-labeled dipalmitoyl PC (UC-DPPC). The parenchymal distributions of newly synthesized PC species were also imaged from incorporations of methyl-D-choline. This dual labeling strategy demonstrated both lack of inhibition of endogenous PC synthesis by exogenous surfactant and location of acyl chain remodeling processes acting on the UC-DPPC-labeled surfactant, leading to formation of polyunsaturated PC lipids. This ability to visualize discrete metabolic events will greatly enhance our understanding of lipid metabolism in diverse tissues and has potential application to both clinical and experimental studies.
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http://dx.doi.org/10.1016/j.jlr.2021.100023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7961103PMC
January 2021

Ion Imaging of Native Protein Complexes Using Orthogonal Time-of-Flight Mass Spectrometry and a Timepix Detector.

J Am Soc Mass Spectrom 2021 Feb 13;32(2):569-580. Epub 2021 Jan 13.

Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry (IMS), Maastricht University, 6229 ER Maastricht, The Netherlands.

Native mass spectrometry (native MS) has emerged as a powerful technique to study the structure and stoichiometry of large protein complexes. Traditionally, native MS has been performed on modified time-of-flight (TOF) systems combined with detectors that do not provide information on the arrival coordinates of each ion at the detector. In this study, we describe the implementation of a Timepix (TPX) pixelated detector on a modified orthogonal TOF (O-TOF) mass spectrometer for the analysis and imaging of native protein complexes. In this unique experimental setup, we have used the impact positions of the ions at the detector to visualize the effects of various ion optical parameters on the flight path of ions. We also demonstrate the ability to unambiguously detect and image individual ion events, providing the first report of single-ion imaging of protein complexes in native MS. Furthermore, the simultaneous space- and time-sensitive nature of the TPX detector was critical in the identification of the origin of an unexpected TOF signal. A signal that could easily be mistaken as a fragment of the protein complex was explicitly identified as a secondary electron signal arising from ion-surface collisions inside the TOF housing. This work significantly extends the mass range previously detected with the TPX and exemplifies the value of simultaneous space- and time-resolved detection in the study of ion optical processes and ion trajectories in TOF mass spectrometers.
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http://dx.doi.org/10.1021/jasms.0c00412DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7863068PMC
February 2021

On-tissue chemical derivatization in mass spectrometry imaging.

Mass Spectrom Rev 2021 Jan 12. Epub 2021 Jan 12.

Mass Spectrometry Centre, Biomedical Sciences Research Institute (BMSRI), School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, UK.

Mass spectrometry imaging (MSI) combines molecular and spatial information in a valuable tool for a wide range of applications. Matrix-assisted laser desorption/ionization (MALDI) is at the forefront of MSI ionization due to its wide availability and increasing improvement in spatial resolution and analysis speed. However, ionization suppression, low concentrations, and endogenous and methodological interferences cause visualization problems for certain molecules. Chemical derivatization (CD) has proven a viable solution to these issues when applied in mass spectrometry platforms. Chemical tagging of target analytes with larger, precharged moieties aids ionization efficiency and removes analytes from areas of potential isobaric interferences. Here, we address the application of CD on tissue samples for MSI analysis, termed on-tissue chemical derivatization (OTCD). MALDI MSI will remain the focus platform due to its popularity, however, alternative ionization techniques such as liquid extraction surface analysis and desorption electrospray ionization will also be recognized. OTCD reagent selection, application, and optimization methods will be discussed in detail. MSI with OTCD is a powerful tool to study the spatial distribution of poorly ionizable molecules within tissues. Most importantly, the use of OTCD-MSI facilitates the analysis of previously inaccessible biologically relevant molecules through the adaptation of existing CD methods. Though further experimental optimization steps are necessary, the benefits of this technique are extensive.
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http://dx.doi.org/10.1002/mas.21680DOI Listing
January 2021

Mass Spectrometry Spatial-Omics on a Single Conductive Slide.

Anal Chem 2021 02 7;93(4):2527-2533. Epub 2021 Jan 7.

Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Universiteitssingel 50, 6229 ER Maastricht, The Netherlands.

Mass spectrometry imaging (MSI) can analyze the spatial distribution of hundreds of different molecules directly from tissue sections usually placed on conductive glass slides to provide conductivity on the sample surface. Additional experiments are often required for molecular identification using consecutive sections on membrane slides compatible with laser capture microdissection (LMD). In this work, we demonstrate for the first time the use of a single conductive slide for both matrix-assisted laser desorption ionization (MALDI)-MSI and direct proteomics. In this workflow, regions of interest can be directly ablated with LMD while preserving protein integrity. These results offer an alternative for MSI-based multimodal spatial-omics.
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http://dx.doi.org/10.1021/acs.analchem.0c04572DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7859928PMC
February 2021

Multilabel Per-Pixel Quantitation in Mass Spectrometry Imaging.

Anal Chem 2021 01 29;93(3):1393-1400. Epub 2020 Dec 29.

Maastricht Multimodal Molecular Imaging Institute (M4I), Maastricht University, 6200 MD Maastricht, The Netherlands.

In quantitative mass spectrometry imaging (MSI), the gold standard adds a single structural homologue of the target compound at a known concentration to the sample. This internal standard enables to map the detected intensity of the target molecule against an external calibration curve. This approach, however, ignores local noise levels and disproportional ion suppression effects, which might depend on the concentration of the target compound. To overcome these issues, we propose a novel approach that applies several isotopically labeled versions, each at a different concentration, to the sample. This allows creating individual internal calibration curves for every MSI pixel. As proof of principle, we have quantified an endogenous peptide of histone H4 by matrix-assisted laser desorption/ionization-Q-MSI (MALDI-Q-MSI), using a mixture of three isotopically labeled versions. The usage of a fourth label allowed us to compare the gold standard to our multilabel approach. We observed substantial heterogeneity in ion suppression across the tissue, which disclosed itself as varying slopes in the per-pixel regression analyses. These slopes were histology-dependent and differed from each other by up to a factor of 4. The results were validated by liquid chromatography-mass spectrometry (LC-MS), exhibiting a high agreement between LC-MS and MALDI-Q-MSI (Pearson correlation = 0.87). A comparison between the multilabel and single-label approaches revealed a higher accuracy for the multilabel method when the local target compound concentration differed too much from the concentration of the single label. In conclusion, we show that the multilabel approach provides superior quantitation compared to a single-label approach, in case the target compound is inhomogeneously distributed at a wide concentration range in the tissue.
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http://dx.doi.org/10.1021/acs.analchem.0c03186DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7871324PMC
January 2021

Stromal vapors for real-time molecular guidance of breast-conserving surgery.

Sci Rep 2020 11 18;10(1):20109. Epub 2020 Nov 18.

Division of Imaging Mass Spectrometry, Maastricht MultiModal Molecular Imaging Institute (M4I), University of Maastricht, Maastricht, The Netherlands.

Achieving radical tumor resection while preserving disease-free tissue during breast-conserving surgery (BCS) remains a challenge. Here, mass spectrometry technologies were used to discriminate stromal tissues reported to be altered surrounding breast tumors, and build tissue classifiers ex vivo. Additionally, we employed the approach for in vivo and real-time classification of breast pathology based on electrosurgical vapors. Breast-resected samples were obtained from patients undergoing surgery at MUMC+. The specimens were subsequently sampled ex vivo to generate electrosurgical vapors analyzed by rapid evaporative ionization mass spectrometry (REIMS). Tissues were processed for histopathology to assign tissue components to the mass spectral profiles. We collected a total of 689 ex vivo REIMS profiles from 72 patients which were analyzed using multivariate statistical analysis (principal component analysis-linear discriminant analysis). These profiles were classified as adipose, stromal and tumor tissues with 92.3% accuracy with a leave-one patient-out cross-validation. Tissue recognition using this ex vivo-built REIMS classification model was subsequently tested in vivo on electrosurgical vapors. Stromal and adipose tissues were classified during one BCS. Complementary ex vivo analyses were performed by REIMS and by desorption electrospray ionization mass spectrometry (DESI-MS) to study the potential of breast stroma to guide BCS. Tumor border stroma (TBS) and remote tumor stroma (RTS) were classified by REIMS and DESI-MS with 86.4% and 87.8% accuracy, respectively. We demonstrate the potential of stromal molecular alterations surrounding breast tumors to guide BCS in real-time using REIMS analysis of electrosurgical vapors.
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http://dx.doi.org/10.1038/s41598-020-77102-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7674429PMC
November 2020

Diagnostic Accuracy of Biomarkers of Alcohol Use in Patients With Liver Disease: A Systematic Review.

Alcohol Clin Exp Res 2021 01 25;45(1):25-37. Epub 2020 Dec 25.

Department of Gastroenterology and Hepatology, (FN, JV), University Hospitals KU Leuven, Leuven, Belgium.

Background And Aims: Alcohol-related liver disease is the most frequent cause of cirrhosis and a major indication for liver transplantation. Several alcohol use biomarkers have been developed in recent years and are already in use in several centers. However, in patients with liver disease their diagnostic performance might be influenced by altered biomarker formation by hepatic damage, altered excretion by kidney dysfunction and diuretics use, and altered deposition in hair and nails. We systematically reviewed studies on the diagnostic accuracy of biomarkers of alcohol use in patients with liver disease and performed a detailed study quality assessment.

Methods: A structured search in PubMed/Medline/Embase databases was performed for relevant studies, published until April 28, 2019. The risk of bias and applicability concerns was assessed according to the adapted quality assessment of diagnostic accuracy studies-2 (QUADAS-2) checklist.

Results: Twelve out of 6,449 studies met inclusion criteria. Urinary ethyl glucuronide and urinary ethyl sulfate showed high sensitivity (70 to 89 and 73 to 82%, respectively) and specificity (93 to 99 and 86 to 89%, respectively) for assessing any amount of alcohol use in the past days. Serum carbohydrate-deficient transferrin showed low sensitivity but higher specificity (40 to 79 and 57 to 99%, respectively) to detect excessive alcohol use in the past weeks. Whole blood phosphatidylethanol showed high sensitivity and specificity (73 to 100 and 90 to 96%, respectively) to detect any amount of alcohol use in the previous weeks. Scalp hair ethyl glucuronide showed high sensitivity (85 to 100%) and specificity (97 to 100%) for detecting chronic excessive alcohol use in the past 3 to 6 months. Main limitations of the current evidence are the lack of an absolute gold standard to assess alcohol use, heterogeneous study populations, and the paucity of studies.

Conclusions: Urinary and scalp hair ethyl glucuronide are currently the most validated alcohol use biomarkers in patients with liver disease with good diagnostic accuracies. Phosphatidylethanol is a highly promising alcohol use biomarker, but so far less validated in liver patients. Alcohol use biomarkers can complement each other regarding diagnostic time window. More validation studies on alcohol use biomarkers in patients with liver disease are needed.
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http://dx.doi.org/10.1111/acer.14512DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7898850PMC
January 2021

Nanomechanical sampling of material for nanoscale mass spectrometry chemical analysis.

Anal Bioanal Chem 2021 Apr 6;413(10):2747-2754. Epub 2020 Oct 6.

Asylum Research an Oxford Instruments Company, Santa Barbara, CA, 93117, USA.

The ability to spatially resolve the chemical distribution of compounds on a surface is important in many applications ranging from biological to material science. To this extent, we have recently introduced a hybrid atomic force microscopy (AFM)-mass spectrometry (MS) system for direct thermal desorption and pyrolysis of material with nanoscale chemical resolution. However, spatially resolved direct surface heating using local thermal desorption becomes challenging on material surfaces with low melting points, because the material will undergo a melting phase transition due to heat dissipation prior to onset of thermal desorption. Therefore, we developed an approach using mechanical sampling and collection of surface materials on an AFM cantilever probe tip for real-time analysis directly from the AFM tip. This approach allows for material to be concentrated directly onto the probe for subsequent MS analysis. We evaluate the performance metrics of the technique and demonstrate localized MS sampling from a candelilla wax matrix containing UV stabilizers avobenzone and oxinoxate from areas down to 250 nm × 250 nm. Overall, this approach removes heat dissipation into the bulk material allowing for a faster desorption and concentration of the gas phase analyte from a single heating pulse enabling higher signal levels from a given amount of material in a single sampling spot.Graphical abstract.
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http://dx.doi.org/10.1007/s00216-020-02967-0DOI Listing
April 2021

Monitoring the three-dimensional distribution of endogenous species in the lungs by matrix-assisted laser desorption/ionization mass spectrometry imaging.

Rapid Commun Mass Spectrom 2021 Jan;35(1):e8957

Centre for Mass Spectrometry Imaging, Biomedical Research Centre, City Campus, Sheffield Hallam University, Sheffield, S1 1WB, UK.

Rationale: Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is routinely employed to monitor the distribution of compounds in tissue sections and generate two-dimensional (2D) images. Whilst informative the images do not represent the distribution of the analyte of interest through the entire organ. The generation of 3D images is an exciting field that can provide a deeper view of the analyte of interest throughout an entire organ.

Methods: Serial sections of mouse and rat lung tissue were obtained at 120 μm depth intervals and imaged individually. Homogenate registration markers were incorporated in order to aid the final 3D image construction. Using freely available software packages, the images were stacked together to generate a 3D image that showed the distribution of endogenous species throughout the lungs.

Results: Preliminary tests were performed on 16 serial tissue sections of mouse lungs. A 3D model showing the distribution of phosphocholine at m/z 184.09 was constructed, which defined the external structure of the lungs and trachea. Later, a second experiment was performed using 24 serial tissue sections of the left lung of a rat. Two molecular markers, identified as [PC (32:1) + K] at m/z 770.51 and [PC (36:4) + K] at m/z 820.52, were used to generate 3D models of the parenchyma and airways, respectively.

Conclusions: A straightforward method to generate 3D MALDI-MS images of selected molecules in lung tissue has been presented. Using freely available imaging software, the 3D distributions of molecules related to different anatomical features were determined.
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http://dx.doi.org/10.1002/rcm.8957DOI Listing
January 2021

Sample preparation of bone tissue for MALDI-MSI for forensic and (pre)clinical applications.

Anal Bioanal Chem 2021 Apr 15;413(10):2683-2694. Epub 2020 Sep 15.

Institute of Chemical Technologies and Analytics, Division of Imaging and Instrumental Analytical Chemistry, TU Wien (Vienna University of Technology), Getreidemarkt 9/164, 1060, Vienna, Austria.

In the past decades, matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) has been applied to a broad range of biological samples, e.g., forensics and preclinical samples. The use of MALDI-MSI for the analysis of bone tissue has been limited due to the insulating properties of the material but more importantly the absence of a proper sample preparation protocol for undecalcified bone tissue. Undecalcified sections are preferred to retain sample integrity as much as possible or to study the tissue-bone bio interface in particular. Here, we optimized the sample preparation protocol of undecalcified bone samples, aimed at both targeted and untargeted applications for forensic and preclinical applications, respectively. Different concentrations of gelatin and carboxymethyl cellulose (CMC) were tested as embedding materials. The composition of 20% gelatin and 7.5% CMC showed to support the tissue best while sectioning. Bone tissue has to be sectioned with a tungsten carbide knife in a longitudinal fashion, while the sections need to be supported with double-sided tapes to maintain the morphology of the tissue. The developed sectioning method was shown to be applicable on rat and mouse as well as human bone samples. Targeted (methadone and EDDP) as well as untargeted (unknown lipids) detection was demonstrated. DHB proved to be the most suitable matrix for the detection of methadone and EDDP in positive ion mode. The limit of detection (LOD) is estimated to approximately 50 pg/spot on bone tissue. The protocol was successfully applied to detect the presence of methadone and EDDP in a dosed rat femur and a dosed human clavicle. The best matrices for the untargeted detection of unknown lipids in mouse hind legs in positive ion mode were CHCA and DHB based on the number of tissue-specific peaks and signal-to-noise ratios. The developed and optimized sample preparation method, applicable on animal and human bones, opens the door for future forensic and (pre)clinical investigations.
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http://dx.doi.org/10.1007/s00216-020-02920-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8007508PMC
April 2021

LipostarMSI: Comprehensive, Vendor-Neutral Software for Visualization, Data Analysis, and Automated Molecular Identification in Mass Spectrometry Imaging.

J Am Soc Mass Spectrom 2020 Jan 21;31(1):155-163. Epub 2019 Nov 21.

Consortium for Computational Molecular and Materials Sciences (CMS)2, Via Elce di Sotto 8, 06123 Perugia, Italy.

Mass Spectrometry Imaging (MSI) is an established and powerful MS technique that enables molecular mapping of tissues and cells finding widespread applications in academic, medical, and pharmaceutical industries. As both the applications and MSI technology have undergone rapid growth and improvement, the challenges associated both with analyzing large datasets and identifying the many detected molecular species have become apparent. The lack of readily available and comprehensive software covering all necessary data analysis steps has further compounded this challenge. To address this issue we developed LipostarMSI, comprehensive and vendor-neutral software for targeted and untargeted MSI data analysis. Through user-friendly implementation of image visualization and co-registration, univariate and multivariate image and spectral analysis, and for the first time, advanced lipid, metabolite, and drug metabolite (MetID) automated identification, LipostarMSI effectively streamlines biochemical interpretation of the data. Here, we introduce LipostarMSI and case studies demonstrating the versatility and many capabilities of the software.
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http://dx.doi.org/10.1021/jasms.9b00034DOI Listing
January 2020

Atheroma-Specific Lipids in and Mice Using 2D and 3D Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Imaging.

J Am Soc Mass Spectrom 2020 Sep 12;31(9):1825-1832. Epub 2020 Aug 12.

Maastricht Multimodal Molecular Imaging Institute (M4I), Maastricht University, 6200 MD Maastricht, The Netherlands.

Atherosclerosis is the major contributor to cardiovascular diseases. It is a spatially and temporally complex inflammatory disease, in which intravascular accumulation of a plethora of lipids is considered to play a crucial role. To date, both the composition and local distribution of the involved lipids have not been thoroughly mapped yet. Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) enables analyzing and visualizing hundreds of lipid molecules within the plaque while preserving each lipid's specific location. In this study, we aim to identify and verify aortic plaque-specific lipids with high-spatial-resolution 2D and 3D MALDI-MSI common to high-fat-diet-fed low-density lipoprotein receptor deficient () mice and chow-fed apolipoprotein E deficient () mice, the two most widely used animal models for atherosclerosis. A total of 11 lipids were found to be significantly and specifically colocalized to the plaques in both mouse models. These were identified and belong to one sphingomyelin (SM), three lysophosphatidic acids (LPA), four lysophosphatidylcholines (LPC), two lysophosphatidylethanolamines (LPE), and one lysophosphatidylinositol (LPI). While these lysolipids and SM 34:0;2 were characteristic of the atherosclerotic aorta plaque itself, LPI 18:0 was mainly localized in the necrotic core of the plaque.
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http://dx.doi.org/10.1021/jasms.0c00070DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7472746PMC
September 2020

MS Imaging-Guided Microproteomics for Spatial Omics on a Single Instrument.

Proteomics 2020 12 19;20(23):e1900369. Epub 2020 Aug 19.

Maastricht MultiModal Molecular Imaging (M4I) Institute, Division of Imaging Mass Spectrometry, Maastricht University, Universiteitssingel 50, Maastricht, 6229 ER, The Netherlands.

Mass spectrometry imaging (MSI) allows investigating the spatial distribution of chemical compounds directly in biological tissues. As the analytical depth of MSI is limited, MSI needs to be coupled to more sensitive local extraction-based omics approaches to achieve a comprehensive molecular characterization. For this, it is important to retain the spatial information provided by MSI for follow-up omics studies. It has been shown that regiospecific MSI data can be used to guide a laser microdissection system for ultra-sensitive liquid chromatography-mass spectrometry (LC-MS) analyses. So far, this combination has required separate and specialized mass spectrometry (MS) instrumentation. Recent advances in dual-source instrumentation, harboring both matrix assisted laser/desorption ionization (MALDI) and electrospray ionization (ESI) sources, promise state-of-the-art MSI and liquid-based proteomic capabilities on the same MS instrument. This study demonstrates that such an instrument can offer both fast lipid-based MSI at high mass and high lateral resolution and sensitive LC-MS on local protein extracts from the exact same tissue section.
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http://dx.doi.org/10.1002/pmic.201900369DOI Listing
December 2020

Morphometric Cell Classification for Single-Cell MALDI-Mass Spectrometry Imaging.

Angew Chem Int Ed Engl 2020 09 17;59(40):17447-17450. Epub 2020 Aug 17.

Maastricht MultiModal Molecular Imaging Institute (M4I), University of Maastricht, Universiteitssingel 50, 6200 MD, Maastricht, The Netherlands.

The large-scale and label-free molecular characterization of single cells in their natural tissue habitat remains a major challenge in molecular biology. We present a method that integrates morphometric image analysis to delineate and classify individual cells with their single-cell-specific molecular profiles. This approach provides a new means to study spatial biological processes such as cancer field effects and the relationship between morphometric and molecular features.
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http://dx.doi.org/10.1002/anie.202007315DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540554PMC
September 2020

INSPIRE: A European training network to foster research and training in cardiovascular safety pharmacology.

J Pharmacol Toxicol Methods 2020 Sep 18;105:106889. Epub 2020 Jun 18.

National Centre for the Replacement, Refinement and Reduction of Animals in Research (NC3Rs), London, UK.

Safety pharmacology is an essential part of drug development aiming to identify, evaluate and investigate undesirable pharmacodynamic properties of a drug primarily prior to clinical trials. In particular, cardiovascular adverse drug reactions (ADR) have halted many drug development programs. Safety pharmacology has successfully implemented a screening strategy to detect cardiovascular liabilities, but there is room for further refinement. In this setting, we present the INSPIRE project, a European Training Network in safety pharmacology for Early Stage Researchers (ESRs), funded by the European Commission's H2020-MSCA-ITN programme. INSPIRE has recruited 15 ESR fellows that will conduct an individual PhD-research project for a period of 36 months. INSPIRE aims to be complementary to ongoing research initiatives. With this as a goal, an inventory of collaborative research initiatives in safety pharmacology was created and the ESR projects have been designed to be complementary to this roadmap. Overall, INSPIRE aims to improve cardiovascular safety evaluation, either by investigating technological innovations or by adding mechanistic insight in emerging safety concerns, as observed in the field of cardio-oncology. Finally, in addition to its hands-on research pillar, INSPIRE will organize a number of summer schools and workshops that will be open to the wider community as well. In summary, INSPIRE aims to foster both research and training in safety pharmacology and hopes to inspire the future generation of safety scientists.
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http://dx.doi.org/10.1016/j.vascn.2020.106889DOI Listing
September 2020

Spatial Localization of Vitamin D Metabolites in Mouse Kidney by Mass Spectrometry Imaging.

ACS Omega 2020 Jun 27;5(22):13430-13437. Epub 2020 May 27.

Mass Spectrometry Centre, Biomedical Sciences Research Institute (BMSRI), School of Biomedical Sciences, Ulster University, Cromore Road, Coleraine BT52 1SA, U.K.

Vitamin D plays a key role in the maintenance of calcium/phosphate homeostasis and elicits biological effects that are relevant to immune function and metabolism. It is predominantly formed through UV exposure in the skin by conversion of 7-dehydrocholsterol (vitamin D3). The clinical biomarker, 25-hydroxyvitamin D (25-(OH)-D), is enzymatically generated in the liver with the active hormone 1,25-dihydroxyvitamin D then formed under classical endocrine control in the kidney. Vitamin D metabolites are measured in biomatrices by liquid chromatography-tandem mass spectrometry (LC-MS/MS). In LC-MS/MS, chemical derivatization (CD) approaches have been employed to achieve the desired limit of quantitation. Recently, matrix-assisted laser desorption/ionization (MALDI) has also been reported as an alternative method. However, these quantitative approaches do not offer any spatial information. Mass spectrometry imaging (MSI) has been proven to be a powerful tool to image the spatial distribution of molecules from the surface of biological tissue sections. On-tissue chemical derivatization (OTCD) enables MSI to image molecules with poor ionization efficiently. In this technical report, several derivatization reagents and OTCD methods were evaluated using different MSI ionization techniques. Here, a method for detection and spatial distribution of vitamin D metabolites in murine kidney tissue sections using an OTCD-MALDI-MSI platform is presented. Moreover, the suitability of using the Bruker ImagePrep for OTCD-based platforms has been demonstrated. Importantly, this method opens the door for expanding the range of other poor ionizable molecules that can be studied by OTCD-MSI by adapting existing CD methods.
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http://dx.doi.org/10.1021/acsomega.0c01697DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7288721PMC
June 2020

Clinical use of mass spectrometry (imaging) for hard tissue analysis in abnormal fracture healing.

Clin Chem Lab Med 2020 06;58(6):897-913

The Maastricht MultiModal Molecular Imaging Institute (M4I), Division of Imaging Mass Spectrometry, Maastricht University, Maastricht, The Netherlands.

Common traumas to the skeletal system are bone fractures and injury-related articular cartilage damage. The healing process can be impaired resulting in non-unions in 5-10% of the bone fractures and in post-traumatic osteoarthritis (PTOA) in up to 75% of the cases of cartilage damage. Despite the amount of research performed in the areas of fracture healing and cartilage repair as well as non-unions and PTOA, still, the outcome of a bone fracture or articular cartilage damage cannot be predicted. Here, we discuss known risk factors and key molecules involved in the repair process, together with the main challenges associated with the prediction of outcome of these injuries. Furthermore, we review and discuss the opportunities for mass spectrometry (MS) - an analytical tool capable of detecting a wide variety of molecules in tissues - to contribute to extending molecular understanding of impaired healing and the discovery of predictive biomarkers. Therefore, the current knowledge and challenges concerning MS imaging of bone and cartilage tissue as well as in vivo MS are discussed. Finally, we explore the possibilities of in situ, real-time MS for the prediction of outcome during surgery of bone fractures and injury-related articular cartilage damage.
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http://dx.doi.org/10.1515/cclm-2019-0857DOI Listing
June 2020

Integrative Metabolic Pathway Analysis Reveals Novel Therapeutic Targets in Osteoarthritis.

Mol Cell Proteomics 2020 04 24;19(4):574-588. Epub 2020 Jan 24.

Grupo de Investigación de Reumatología, INIBIC-Complejo Hospitalario Universitario de A Coruña, SERGAS, Departamento de Medicina Universidad de A Coruña, A Coruña, Spain. Electronic address:

In osteoarthritis (OA), impairment of cartilage regeneration can be related to a defective chondrogenic differentiation of mesenchymal stromal cells (MSCs). Therefore, understanding the proteomic- and metabolomic-associated molecular events during the chondrogenesis of MSCs could provide alternative targets for therapeutic intervention. Here, a SILAC-based proteomic analysis identified 43 proteins related with metabolic pathways whose abundance was significantly altered during the chondrogenesis of OA human bone marrow MSCs (hBMSCs). Then, the level and distribution of metabolites was analyzed in these cells and healthy controls by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), leading to the recognition of characteristic metabolomic profiles at the early stages of differentiation. Finally, integrative pathway analysis showed that UDP-glucuronic acid synthesis and amino sugar metabolism were downregulated in OA hBMSCs during chondrogenesis compared with healthy cells. Alterations in these metabolic pathways may disturb the production of hyaluronic acid (HA) and other relevant cartilage extracellular matrix (ECM) components. This work provides a novel integrative insight into the molecular alterations of osteoarthritic MSCs and potential therapeutic targets for OA drug development through the enhancement of chondrogenesis.
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http://dx.doi.org/10.1074/mcp.RA119.001821DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7124476PMC
April 2020

Ultra-High Mass Resolving Power, Mass Accuracy, and Dynamic Range MALDI Mass Spectrometry Imaging by 21-T FT-ICR MS.

Anal Chem 2020 02 3;92(4):3133-3142. Epub 2020 Feb 3.

National High Magnetic Field Laboratory , Florida State University , 1800 East Paul Dirac Drive , Tallahassee , Florida 32310-4005 , United States.

Detailed characterization of complex biological surfaces by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging (MSI) requires instrumentation that is capable of high mass resolving power, mass accuracy, and dynamic range. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) offers the highest mass spectral performance for MALDI MSI experiments, and often reveals molecular features that are unresolved on lower performance instrumentation. Higher magnetic field strength improves all performance characteristics of FT-ICR; mass resolving power improves linearly, while mass accuracy and dynamic range improve quadratically with magnetic field strength. Here, MALDI MSI at 21T is demonstrated for the first time: mass resolving power in excess of 1 600 000 (at / 400), root-mean-square mass measurement accuracy below 100 ppb, and dynamic range per pixel over 500:1 were obtained from the direct analysis of biological tissue sections. Molecular features with / differences as small as 1.79 mDa were resolved and identified with high mass accuracy. These features allow for the separation and identification of lipids to the underlying structures of tissues. The unique molecular detail, accuracy, sensitivity, and dynamic range combined in a 21T MALDI FT-ICR MSI experiment enable researchers to visualize molecular structures in complex tissues that have remained hidden until now. The instrument described allows for future innovative, such as high-end studies to unravel the complexity of biological, geological, and engineered organic material surfaces with an unsurpassed detail.
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http://dx.doi.org/10.1021/acs.analchem.9b04768DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7031845PMC
February 2020

Simultaneous Detection of Zinc and Its Pathway Metabolites Using MALDI MS Imaging of Prostate Tissue.

Anal Chem 2020 02 28;92(4):3171-3179. Epub 2020 Jan 28.

Department of Circulation and Medical Imaging , Norwegian University of Science and Technology (NTNU) , 7491 Trondheim , Norway.

Levels of zinc, along with its mechanistically related metabolites citrate and aspartate, are widely reported as reduced in prostate cancer compared to healthy tissue and are therefore pointed out as potential cancer biomarkers. Previously, it has only been possible to analyze zinc and metabolites by separate detection methods. Through matrix-assisted laser desorption/ionization mass spectrometry imaging (MSI), we were for the first time able to demonstrate, in two different sample sets ( = 45 and = 4), the simultaneous spatial detection of zinc, in the form of ZnCl, together with citrate, aspartate, and -acetylaspartate on human prostate cancer tissues. The reliability of the ZnCl detection was validated by total zinc determination using laser ablation inductively coupled plasma MSI on adjacent serial tissue sections. Zinc, citrate, and aspartate were correlated with each other (range = 0.46 to 0.74) and showed a significant reduction in cancer compared to non-cancer epithelium ( < 0.05, log fold change range: -0.423 to -0.987), while no significant difference between cancer and stroma tissue was found. Simultaneous spatial detection of zinc and its metabolites is not only a valuable tool for analyzing the role of zinc in prostate metabolism but might also provide a fast and simple method to detect zinc, citrate, and aspartate levels as a biomarker signature for prostate cancer diagnostics and prognostics.
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http://dx.doi.org/10.1021/acs.analchem.9b04903DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7584334PMC
February 2020

Maintenance of Deep Lung Architecture and Automated Airway Segmentation for 3D Mass Spectrometry Imaging.

Sci Rep 2019 12 27;9(1):20160. Epub 2019 Dec 27.

Department of Microbial Pathogenesis, University of Maryland School of Dentistry, Baltimore, 21201, USA.

Mass spectrometry imaging (MSI) is a technique for mapping the spatial distributions of molecules in sectioned tissue. Histology-preserving tissue preparation methods are central to successful MSI studies. Common fixation methods, used to preserve tissue morphology, can result in artifacts in the resulting MSI experiment including delocalization of analytes, altered adduct profiles, and loss of key analytes due to irreversible cross-linking and diffusion. This is especially troublesome in lung and airway samples, in which histology and morphology is best interpreted from 3D reconstruction, requiring the large and small airways to remain inflated during analysis. Here, we developed an MSI-compatible inflation containing as few exogenous components as possible, forgoing perfusion, fixation, and addition of salt solutions upon inflation that resulted in an ungapped 3D molecular reconstruction through more than 300 microns. We characterized a series of polyunsaturated phospholipids (PUFA-PLs), specifically phosphatidylinositol (-PI) lipids linked to lethal inflammation in bacterial infection and mapped them in serial sections of inflated mouse lung. PUFA-PIs were identified using spatial lipidomics and determined to be determinant markers of major airway features using unsupervised hierarchical clustering. Deep lung architecture was preserved using this inflation approach and the resulting sections are compatible with multiple MSI modalities, automated interpretation software, and serial 3D reconstruction.
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http://dx.doi.org/10.1038/s41598-019-56364-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6934789PMC
December 2019