The analysis of samples with large height variations remains a challenge for mass spectrometry im... more The analysis of samples with large height variations remains a challenge for mass spectrometry imaging (MSI), despite many technological advantages. Ambient sampling and ionization MS techniques allow for the molecular analysis of sample surfaces with height variations, but most techniques lack MSI capabilities. We developed a 3D MS scanner for the automated sampling and imaging of a 3D surface with laser-assisted rapid evaporative ionization mass spectrometry (LA-REIMS). The sample is moved automatically with a constant distance between the laser probe and sample surface in the 3D MS Scanner. The topography of the surface was scanned with a laser point distance sensor to define the MS measurement points. MS acquisition was performed with LA-REIMS using a surgical CO 2 laser coupled to a qTOF instrument. The topographical scan and MS acquisition can be completed within 1 h using the 3D MS scanner for 300 measurement points on uneven samples with a spatial resolution of 2 mm in the top view, corresponding to 22.04 cm 2. Comparison between the automated acquisition with the 3D MS scanner and manual acquisition by hand showed that the automation resulted in increased reproducibility between the measurement points. 3D visualizations of molecular distributions related to structural differences were shown for an apple, a marrowbone, and a human femoral head to demonstrate the imaging feasibility of the system. The developed 3D MS scanner allows for the automated sampling of surfaces with uneven topographies with LA-REIMS, which can be used for the 3D visualization of molecular distributions of these surfaces.
Additional file 1: Supplementary Figure 1. The molar percentage excess (MPE) for 13C6-Phe (left) ... more Additional file 1: Supplementary Figure 1. The molar percentage excess (MPE) for 13C6-Phe (left) and 13C6-Tyr (right) in plasma samples from the same mice over the same time course and measured by GC-C-IRMS.
Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopi... more Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopic imaging (MRSI) of tumors is spatially heterogeneous. Magnetic resonance spectroscopy (MRS) studies have shown an elevation of phosphocholine (PCho) and total choline-containing metabolites (tCho) in breast cancer cells and tumors [1]. However, in vivo H MRSI at high spatial resolution with the spectral resolution to resolve PCho, glycerophosphocholine (GPC), and free choline (Cho), which are the three overlapping signals that the tCho signal consists of, is currently unavailable. Mass spectrometry imaging (MSI) of histologic tumor sections is able to detect the spatial distribution of these choline metabolites and thousands of other molecules from the tissue surface. In this study, we have investigated the correlations between tCho, lipid metabolites, and phosphatidylcholine (PC) species in a human breast cancer model by combining in vivo magnetic resonance imaging (MRI) and MRSI with ...
view of FTIR and DACQ Inout: config users see eachother actions view on config and data depends o... more view of FTIR and DACQ Inout: config users see eachother actions view on config and data depends on user preference settings active web-pages
We and others have previously shown that sphingolipids, a family of bioactive membrane lipids, ca... more We and others have previously shown that sphingolipids, a family of bioactive membrane lipids, can modulate endothelium-derived relaxing factor signalling. Since hypertension is associated with endothelial dysfunction, we investigated whether hypertension is associated with altered vascular sphingolipid biology and/or sphingolipid levels. In isolated carotid arteries from spontaneously hypertensive rats (SHR), pharmacological modulation of sphingolipid metabolism by means of exogenously applied sphingomyelinase (SMase, 0.1U/ml) or application of the sphingosine kinase inhibitor dimethylsphingosine (DMS, 10μM), induced marked transient contractions (2.1 ± 0.1 mN/mm and 1.4±0.4 mN/mm respectively; n=10). These contractions were virtually absent in vessels from normotensive Wistar Kyoto rats (WKY; 0.6±0.1mN/mm and 0.0±0.0 mN/mm respectively; n=9). Notably, the contractions were fully abolished by prior endothelium removal or by the cyclooxygenase inhibitor indomethacin (10μM; 0.0±0.0 m...
AbstractInduced pluripotent stem cells (iPSCs) are opening up new possibilities for medicine. Und... more AbstractInduced pluripotent stem cells (iPSCs) are opening up new possibilities for medicine. Understanding the regulation of iPSC biology is important when attempting to apply these cells to disease models or therapy. Changes of lipid metabolism in iPSCs were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF-IMS). Analysis revealed changes of the intensity and distribution of peaks at m/z 782.5 and 798.5 in iPSC colonies during spontaneous differentiation. Two phosphatidylcholines (PCs) were identified: C44H81NO8P, PC(36:4)[M+H]+ at m/z 782.5 and C42H82NO8P, PC(34:1)[M+K]+ at m/z 798.5. The intensity of PC(36:4) showed an inverse relation between undifferentiated and differentiated iPSC colonies. PC(34:1) displayed a diffuse distribution in undifferentiated iPSC colonies, while it showed a concentric distribution in differentiated iPSC colonies, and was localized at the border of the differentiated and undifferentiated areas or the border between undifferentiated iPSC and feeder cells. These findings suggested that the distribution of lipids changes during the growth and differentiation of iPSCs and that MALDI-TOF-IMS was useful for analyzing these changes. PC(36:4) might play a role in maintaining pluripotency, while PC(34:1) might play a role in the differentiation and spread of iPSCs. Graphical AbstractMALDI Imaging for phosphatidylcholine distribution changes during sponteneous differentiaton of induced pluiripotent stem cells colonies
Background Metabolic reprogramming is a common phenomenon in tumorigenesis and tumor progression.... more Background Metabolic reprogramming is a common phenomenon in tumorigenesis and tumor progression. Amino acids are important mediators in cancer metabolism, and their kinetics in tumor tissue are far from being understood completely. Mass spectrometry imaging is capable to spatiotemporally trace important endogenous metabolites in biological tissue specimens. In this research, we studied L-[ring-13C6]-labeled phenylalanine and tyrosine kinetics in a human non-small cell lung carcinoma (NSCLC) xenografted mouse model using matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry imaging (MALDI-FTICR-MSI). Methods We investigated the L-[ring-13C6]-Phenylalanine (13C6-Phe) and L-[ring-13C6]-Tyrosine (13C6-Tyr) kinetics at 10 min (n = 4), 30 min (n = 3), and 60 min (n = 4) after tracer injection and sham-treated group (n = 3) at 10 min in mouse-xenograft lung tumor tissues by MALDI-FTICR-MSI. Results The dynamic changes in the spatial distri...
Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopi... more Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopic imaging (MRSI) of tumors is spatially heterogeneous. Magnetic resonance spectroscopy (MRS) studies have shown an elevation of phosphocholine (PCho) and total choline-containing metabolites (tCho) in breast cancer cells and tumors [1]. Our previous study [2] investigated the relationship between tCho and membrane phosphatidylcholine (PC) species which can be detected by mass spectrometric imaging (MSI) of histologic tumor sections. In this study, we have further investigated the correlations between tCho and proteins in a human breast cancer model by combining in vivo magnetic resonance imaging (MRI) and MRSI with ex vivo MSI. Methods: Human MDA-MB-231-HRE-tdTomato breast cancer cells were orthotopically grown in nude mice. Both 3-dimensional (3D) waterunsuppressed H MRSI to detect water, and water-suppressed 3D MRSI to detect metabolites, was performed on tumors in vivo. Inherently reg...
At the basis of developmental biology lies the understanding of how the development of organs is ... more At the basis of developmental biology lies the understanding of how the development of organs is regulated during growth. Evidence has been presented of a strong connection in embryogenesis between the appearance of boundaries between specific cell types and the proliferation of cell clusters into a specific tissue. Despite extensive efforts to understand how the fate of cells is determined during organ development, little is known about the relationship between the chemical composition of cells and their function in the growth process. We present here the application of broadband Coherent anti-Stokes Raman Scattering (CARS) hyperspectral microscopy to study the local chemical composition of cells in the developing wing of Drosophila melanogaster larvae. Broadband CARS is a third order multiphoton microscopy allowing the acquisition of Raman-like vibrational spectra at each location of the sample. Hence, CARS is ideal for non-invasively imaging complex samples as it allows label-fre...
In osteoarthritis (OA), impairment of cartilage regeneration can be related to a defective chondr... more 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 compare...
Angewandte Chemie (International ed. in English), Jan 22, 2018
Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing differe... more Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing different mass-to-charge ratios to be mapped within complex environments revealing regional changes at the molecular level. Even at high mass resolving power, however, these images often reflect the summed distribution of multiple isomeric molecules, each potentially possessing a unique distribution coinciding with distinct biological function(s) and metabolic origin. Herein, this chemical ambiguity is addressed through an innovative combination of ozone-induced dissociation reactions with MSI, enabling the differential imaging of isomeric lipid molecules directly from biological tissues. For the first time, we demonstrate both double bond- and sn-positional isomeric lipids exhibit distinct spatial locations within tissue. This MSI approach enables researchers to unravel local lipid molecular complexity based on both exact elemental composition and isomeric structure directly from tissues.
Hepatocellular lipid accumulation characterizes nonalcoholic fatty liver disease (NAFLD). However... more Hepatocellular lipid accumulation characterizes nonalcoholic fatty liver disease (NAFLD). However, the types of lipids associated with disease progression are debated, as is the impact of their localization. Traditional lipidomics analysis using liver homogenates or plasma dilutes and averages lipid concentrations, and does not provide spatial information about lipid distribution. We aimed to characterize the distribution of specific lipid species related to NAFLD severity by performing label-free molecular analysis by mass spectrometry imaging (MSI). Fresh frozen liver biopsies from obese subjects undergoing bariatric surgery ( n = 23) with various degrees of NAFLD were cryosectioned and analyzed by matrix-assisted laser desorption/ionization (MALDI)-MSI. Molecular identification was verified by tandem MS. Tissue sections were histopathologically stained, annotated according to the Kleiner classification, and coregistered with the MSI data set. Lipid pathway analysis was performed ...
Articular cartilage is exposed to a gradient of oxygen levels ranging from 5% at the surface to 1... more Articular cartilage is exposed to a gradient of oxygen levels ranging from 5% at the surface to 1% in the deepest layers. While most cartilage research is performed in supraphysiological oxygen levels (19−21%), culturing chondrocytes under hypoxic oxygen levels (≤8%) promotes the chondrogenic phenotype. Exposure of cells to various oxygen levels alters their lipid metabolism, but detailed studies examining how hypoxia affects lipid metabolism in chondrocytes are lacking. To better understand the chondrocyte's behavior in response to oxygen, we cultured 3D pellets of human primary chondrocytes in normoxia (20% oxygen) and hypoxia (2.5% oxygen) and employed matrixassisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) in order to characterize the lipid profiles and their spatial distribution. In this work we show that chondrocytes cultured in hypoxia and normoxia can be differentiated by their lipid profiles. Among other species, phosphatidylglycerol species were increased in normoxic pellets, whereas phosphatidylinositol species were the most prominent lipids in hypoxic pellets. Moreover, spatial mapping revealed that phospahtidylglyycerol species were less prominent in the center of pellets where the oxygen level is lower. Additional analysis revealed a higher abundance of the mitochondrial-specific lipids, cardiolipins, in normoxic conditions. In conclusion MALDI-MSI described specific lipid profiles that could be used as sensors of oxygen level changes and may especially be relevant for retaining the chondrogenic phenotype, which has important implications for the treatment of bone and cartilage diseases.
Matrix-Assisted Laser Desorption Ionization, MALDI, has been increasingly used in a variety of bi... more Matrix-Assisted Laser Desorption Ionization, MALDI, has been increasingly used in a variety of biomedical applications, including tissue imaging of clinical tissue samples, and in drug discovery and development. These studies strongly depend on the performance of the analytical instrumentation and would drastically benefit from improved sensitivity, reproducibility, and mass/spatial resolution. In this work, we report on a novel combined MALDI/ESI interface, which was coupled to different Orbitrap mass spectrometers (Elite and Q Exactive Plus) and extensively characterized with peptide and protein standards, and in tissue imaging experiments. In our approach, MALDI is performed in the elevated pressure regime (5-8 Torr) at a spatial resolution of 15-30 μm, while ESI-generated ions are injected orthogonally to the interface axis. We have found that introduction of the MALDI-generated ions into an electrodynamic dual-funnel interface results in increased sensitivity characterized by a...
Using label-free ToF-SIMS imaging mass spectrometry, we generated a map of small molecules differ... more Using label-free ToF-SIMS imaging mass spectrometry, we generated a map of small molecules differentially expressed in the Drosophila wing imaginal disc. The distributions of these moieties were in line with gene expression patterns observed during wing imaginal disc development. Combining ToF-SIMS imaging and coherent anti-Stokes Raman spectroscopy (CARS) microspectroscopy allowed us to locally identify acylglycerols as the main constituents of the pattern differentiating the future body wall tissue from the wing blade tissue. The findings presented herein clearly demonstrate that lipids localization patterns are strongly correlated with a developmental gene expression. From this correlation we hypothesize that lipids play a so far unrecognized role in organ development.
Angewandte Chemie (International ed. in English), Jan 11, 2017
Mass spectrometry imaging (MSI) simultaneously detects and identifies the spatial distribution of... more Mass spectrometry imaging (MSI) simultaneously detects and identifies the spatial distribution of numerous molecules throughout tissues. Currently, MSI is limited to providing a static and ex vivo snapshot of highly dynamic systems in which molecules are constantly synthesized and consumed. Herein, we demonstrate an innovative MSI methodology to study dynamic molecular changes of amino acids within biological tissues by measuring the dilution and conversion of stable isotopes in a mouse model. We evaluate the method specifically on hepatocellular metabolism of the essential amino acid l-phenylalanine, associated with liver diseases. Crucially, the method reveals the localized dynamics of l-phenylalanine metabolism, including its in vivo hydroxylation to l-tyrosine and co-localization with other liver metabolites in a time course of samples from different animals. This method thus enables the dynamics of localized biochemical synthesis to be studied directly from biological tissues.
The analysis of samples with large height variations remains a challenge for mass spectrometry im... more The analysis of samples with large height variations remains a challenge for mass spectrometry imaging (MSI), despite many technological advantages. Ambient sampling and ionization MS techniques allow for the molecular analysis of sample surfaces with height variations, but most techniques lack MSI capabilities. We developed a 3D MS scanner for the automated sampling and imaging of a 3D surface with laser-assisted rapid evaporative ionization mass spectrometry (LA-REIMS). The sample is moved automatically with a constant distance between the laser probe and sample surface in the 3D MS Scanner. The topography of the surface was scanned with a laser point distance sensor to define the MS measurement points. MS acquisition was performed with LA-REIMS using a surgical CO 2 laser coupled to a qTOF instrument. The topographical scan and MS acquisition can be completed within 1 h using the 3D MS scanner for 300 measurement points on uneven samples with a spatial resolution of 2 mm in the top view, corresponding to 22.04 cm 2. Comparison between the automated acquisition with the 3D MS scanner and manual acquisition by hand showed that the automation resulted in increased reproducibility between the measurement points. 3D visualizations of molecular distributions related to structural differences were shown for an apple, a marrowbone, and a human femoral head to demonstrate the imaging feasibility of the system. The developed 3D MS scanner allows for the automated sampling of surfaces with uneven topographies with LA-REIMS, which can be used for the 3D visualization of molecular distributions of these surfaces.
Additional file 1: Supplementary Figure 1. The molar percentage excess (MPE) for 13C6-Phe (left) ... more Additional file 1: Supplementary Figure 1. The molar percentage excess (MPE) for 13C6-Phe (left) and 13C6-Tyr (right) in plasma samples from the same mice over the same time course and measured by GC-C-IRMS.
Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopi... more Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopic imaging (MRSI) of tumors is spatially heterogeneous. Magnetic resonance spectroscopy (MRS) studies have shown an elevation of phosphocholine (PCho) and total choline-containing metabolites (tCho) in breast cancer cells and tumors [1]. However, in vivo H MRSI at high spatial resolution with the spectral resolution to resolve PCho, glycerophosphocholine (GPC), and free choline (Cho), which are the three overlapping signals that the tCho signal consists of, is currently unavailable. Mass spectrometry imaging (MSI) of histologic tumor sections is able to detect the spatial distribution of these choline metabolites and thousands of other molecules from the tissue surface. In this study, we have investigated the correlations between tCho, lipid metabolites, and phosphatidylcholine (PC) species in a human breast cancer model by combining in vivo magnetic resonance imaging (MRI) and MRSI with ...
view of FTIR and DACQ Inout: config users see eachother actions view on config and data depends o... more view of FTIR and DACQ Inout: config users see eachother actions view on config and data depends on user preference settings active web-pages
We and others have previously shown that sphingolipids, a family of bioactive membrane lipids, ca... more We and others have previously shown that sphingolipids, a family of bioactive membrane lipids, can modulate endothelium-derived relaxing factor signalling. Since hypertension is associated with endothelial dysfunction, we investigated whether hypertension is associated with altered vascular sphingolipid biology and/or sphingolipid levels. In isolated carotid arteries from spontaneously hypertensive rats (SHR), pharmacological modulation of sphingolipid metabolism by means of exogenously applied sphingomyelinase (SMase, 0.1U/ml) or application of the sphingosine kinase inhibitor dimethylsphingosine (DMS, 10μM), induced marked transient contractions (2.1 ± 0.1 mN/mm and 1.4±0.4 mN/mm respectively; n=10). These contractions were virtually absent in vessels from normotensive Wistar Kyoto rats (WKY; 0.6±0.1mN/mm and 0.0±0.0 mN/mm respectively; n=9). Notably, the contractions were fully abolished by prior endothelium removal or by the cyclooxygenase inhibitor indomethacin (10μM; 0.0±0.0 m...
AbstractInduced pluripotent stem cells (iPSCs) are opening up new possibilities for medicine. Und... more AbstractInduced pluripotent stem cells (iPSCs) are opening up new possibilities for medicine. Understanding the regulation of iPSC biology is important when attempting to apply these cells to disease models or therapy. Changes of lipid metabolism in iPSCs were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF-IMS). Analysis revealed changes of the intensity and distribution of peaks at m/z 782.5 and 798.5 in iPSC colonies during spontaneous differentiation. Two phosphatidylcholines (PCs) were identified: C44H81NO8P, PC(36:4)[M+H]+ at m/z 782.5 and C42H82NO8P, PC(34:1)[M+K]+ at m/z 798.5. The intensity of PC(36:4) showed an inverse relation between undifferentiated and differentiated iPSC colonies. PC(34:1) displayed a diffuse distribution in undifferentiated iPSC colonies, while it showed a concentric distribution in differentiated iPSC colonies, and was localized at the border of the differentiated and undifferentiated areas or the border between undifferentiated iPSC and feeder cells. These findings suggested that the distribution of lipids changes during the growth and differentiation of iPSCs and that MALDI-TOF-IMS was useful for analyzing these changes. PC(36:4) might play a role in maintaining pluripotency, while PC(34:1) might play a role in the differentiation and spread of iPSCs. Graphical AbstractMALDI Imaging for phosphatidylcholine distribution changes during sponteneous differentiaton of induced pluiripotent stem cells colonies
Background Metabolic reprogramming is a common phenomenon in tumorigenesis and tumor progression.... more Background Metabolic reprogramming is a common phenomenon in tumorigenesis and tumor progression. Amino acids are important mediators in cancer metabolism, and their kinetics in tumor tissue are far from being understood completely. Mass spectrometry imaging is capable to spatiotemporally trace important endogenous metabolites in biological tissue specimens. In this research, we studied L-[ring-13C6]-labeled phenylalanine and tyrosine kinetics in a human non-small cell lung carcinoma (NSCLC) xenografted mouse model using matrix-assisted laser desorption/ionization Fourier-transform ion cyclotron resonance mass spectrometry imaging (MALDI-FTICR-MSI). Methods We investigated the L-[ring-13C6]-Phenylalanine (13C6-Phe) and L-[ring-13C6]-Tyrosine (13C6-Tyr) kinetics at 10 min (n = 4), 30 min (n = 3), and 60 min (n = 4) after tracer injection and sham-treated group (n = 3) at 10 min in mouse-xenograft lung tumor tissues by MALDI-FTICR-MSI. Results The dynamic changes in the spatial distri...
Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopi... more Introduction: The intensity of the total choline (tCho) signal in magnetic resonance spectroscopic imaging (MRSI) of tumors is spatially heterogeneous. Magnetic resonance spectroscopy (MRS) studies have shown an elevation of phosphocholine (PCho) and total choline-containing metabolites (tCho) in breast cancer cells and tumors [1]. Our previous study [2] investigated the relationship between tCho and membrane phosphatidylcholine (PC) species which can be detected by mass spectrometric imaging (MSI) of histologic tumor sections. In this study, we have further investigated the correlations between tCho and proteins in a human breast cancer model by combining in vivo magnetic resonance imaging (MRI) and MRSI with ex vivo MSI. Methods: Human MDA-MB-231-HRE-tdTomato breast cancer cells were orthotopically grown in nude mice. Both 3-dimensional (3D) waterunsuppressed H MRSI to detect water, and water-suppressed 3D MRSI to detect metabolites, was performed on tumors in vivo. Inherently reg...
At the basis of developmental biology lies the understanding of how the development of organs is ... more At the basis of developmental biology lies the understanding of how the development of organs is regulated during growth. Evidence has been presented of a strong connection in embryogenesis between the appearance of boundaries between specific cell types and the proliferation of cell clusters into a specific tissue. Despite extensive efforts to understand how the fate of cells is determined during organ development, little is known about the relationship between the chemical composition of cells and their function in the growth process. We present here the application of broadband Coherent anti-Stokes Raman Scattering (CARS) hyperspectral microscopy to study the local chemical composition of cells in the developing wing of Drosophila melanogaster larvae. Broadband CARS is a third order multiphoton microscopy allowing the acquisition of Raman-like vibrational spectra at each location of the sample. Hence, CARS is ideal for non-invasively imaging complex samples as it allows label-fre...
In osteoarthritis (OA), impairment of cartilage regeneration can be related to a defective chondr... more 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 compare...
Angewandte Chemie (International ed. in English), Jan 22, 2018
Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing differe... more Mass spectrometry imaging (MSI) enables the spatial distributions of molecules possessing different mass-to-charge ratios to be mapped within complex environments revealing regional changes at the molecular level. Even at high mass resolving power, however, these images often reflect the summed distribution of multiple isomeric molecules, each potentially possessing a unique distribution coinciding with distinct biological function(s) and metabolic origin. Herein, this chemical ambiguity is addressed through an innovative combination of ozone-induced dissociation reactions with MSI, enabling the differential imaging of isomeric lipid molecules directly from biological tissues. For the first time, we demonstrate both double bond- and sn-positional isomeric lipids exhibit distinct spatial locations within tissue. This MSI approach enables researchers to unravel local lipid molecular complexity based on both exact elemental composition and isomeric structure directly from tissues.
Hepatocellular lipid accumulation characterizes nonalcoholic fatty liver disease (NAFLD). However... more Hepatocellular lipid accumulation characterizes nonalcoholic fatty liver disease (NAFLD). However, the types of lipids associated with disease progression are debated, as is the impact of their localization. Traditional lipidomics analysis using liver homogenates or plasma dilutes and averages lipid concentrations, and does not provide spatial information about lipid distribution. We aimed to characterize the distribution of specific lipid species related to NAFLD severity by performing label-free molecular analysis by mass spectrometry imaging (MSI). Fresh frozen liver biopsies from obese subjects undergoing bariatric surgery ( n = 23) with various degrees of NAFLD were cryosectioned and analyzed by matrix-assisted laser desorption/ionization (MALDI)-MSI. Molecular identification was verified by tandem MS. Tissue sections were histopathologically stained, annotated according to the Kleiner classification, and coregistered with the MSI data set. Lipid pathway analysis was performed ...
Articular cartilage is exposed to a gradient of oxygen levels ranging from 5% at the surface to 1... more Articular cartilage is exposed to a gradient of oxygen levels ranging from 5% at the surface to 1% in the deepest layers. While most cartilage research is performed in supraphysiological oxygen levels (19−21%), culturing chondrocytes under hypoxic oxygen levels (≤8%) promotes the chondrogenic phenotype. Exposure of cells to various oxygen levels alters their lipid metabolism, but detailed studies examining how hypoxia affects lipid metabolism in chondrocytes are lacking. To better understand the chondrocyte's behavior in response to oxygen, we cultured 3D pellets of human primary chondrocytes in normoxia (20% oxygen) and hypoxia (2.5% oxygen) and employed matrixassisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) in order to characterize the lipid profiles and their spatial distribution. In this work we show that chondrocytes cultured in hypoxia and normoxia can be differentiated by their lipid profiles. Among other species, phosphatidylglycerol species were increased in normoxic pellets, whereas phosphatidylinositol species were the most prominent lipids in hypoxic pellets. Moreover, spatial mapping revealed that phospahtidylglyycerol species were less prominent in the center of pellets where the oxygen level is lower. Additional analysis revealed a higher abundance of the mitochondrial-specific lipids, cardiolipins, in normoxic conditions. In conclusion MALDI-MSI described specific lipid profiles that could be used as sensors of oxygen level changes and may especially be relevant for retaining the chondrogenic phenotype, which has important implications for the treatment of bone and cartilage diseases.
Matrix-Assisted Laser Desorption Ionization, MALDI, has been increasingly used in a variety of bi... more Matrix-Assisted Laser Desorption Ionization, MALDI, has been increasingly used in a variety of biomedical applications, including tissue imaging of clinical tissue samples, and in drug discovery and development. These studies strongly depend on the performance of the analytical instrumentation and would drastically benefit from improved sensitivity, reproducibility, and mass/spatial resolution. In this work, we report on a novel combined MALDI/ESI interface, which was coupled to different Orbitrap mass spectrometers (Elite and Q Exactive Plus) and extensively characterized with peptide and protein standards, and in tissue imaging experiments. In our approach, MALDI is performed in the elevated pressure regime (5-8 Torr) at a spatial resolution of 15-30 μm, while ESI-generated ions are injected orthogonally to the interface axis. We have found that introduction of the MALDI-generated ions into an electrodynamic dual-funnel interface results in increased sensitivity characterized by a...
Using label-free ToF-SIMS imaging mass spectrometry, we generated a map of small molecules differ... more Using label-free ToF-SIMS imaging mass spectrometry, we generated a map of small molecules differentially expressed in the Drosophila wing imaginal disc. The distributions of these moieties were in line with gene expression patterns observed during wing imaginal disc development. Combining ToF-SIMS imaging and coherent anti-Stokes Raman spectroscopy (CARS) microspectroscopy allowed us to locally identify acylglycerols as the main constituents of the pattern differentiating the future body wall tissue from the wing blade tissue. The findings presented herein clearly demonstrate that lipids localization patterns are strongly correlated with a developmental gene expression. From this correlation we hypothesize that lipids play a so far unrecognized role in organ development.
Angewandte Chemie (International ed. in English), Jan 11, 2017
Mass spectrometry imaging (MSI) simultaneously detects and identifies the spatial distribution of... more Mass spectrometry imaging (MSI) simultaneously detects and identifies the spatial distribution of numerous molecules throughout tissues. Currently, MSI is limited to providing a static and ex vivo snapshot of highly dynamic systems in which molecules are constantly synthesized and consumed. Herein, we demonstrate an innovative MSI methodology to study dynamic molecular changes of amino acids within biological tissues by measuring the dilution and conversion of stable isotopes in a mouse model. We evaluate the method specifically on hepatocellular metabolism of the essential amino acid l-phenylalanine, associated with liver diseases. Crucially, the method reveals the localized dynamics of l-phenylalanine metabolism, including its in vivo hydroxylation to l-tyrosine and co-localization with other liver metabolites in a time course of samples from different animals. This method thus enables the dynamics of localized biochemical synthesis to be studied directly from biological tissues.
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Papers by Gert Eijkel