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

Abstract

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.

Spatial lipidomics of fresh-frozen spines

“…The three spines have a different abundance and spatial location for [SM(34:1;O2)+Na] + because it appears to represent the presence of blood vessels 96 and intervertebral discs 97 in the lumbar tissue, which are not consistent in the lumbar region as a function of length 96 . [PC(32:1)+H] + is known to be common in biological tissue [98][99][100][101] and is shown here to be located in the nerves surrounding the white matter in the spinal cord (Figure 5H, 5N, 6). Finally, [PC(32:1)+H] + , [PC(O-34:1)+H] + , [PC(34:2)+K] + , and [PC(38:3)+Na] + remained consistent in spatial location across the three spines.…”

Sample Preparation Method for MALDI Mass Spectrometry Imaging of Fresh-Frozen Spines

“…The three spines have a different abundance and spatial location for [SM­(34:1;O2)+Na] + (Figure D) because it appears to represent the presence of blood vessels and intervertebral discs in the lumbar tissue, which are not consistent in the lumbar region as a function of length . [PC(32:1)+H] + is known to be common in biological tissue − and is shown here to be located in the nerves surrounding the white matter in the spinal cord (Figure H,N,G). Finally, [PC(32:1)+H] + (Figure G), [PC­(O-34:1)+H] + (Figure F), [PC­(34:2)+K] + (Figure H), and [PC(38:3)+Na] + (Figure I) remained consistent in spatial locations across the three spines.…”

Developing CHCA/PPD as a novel matrix for enhanced matrix‐assisted laser desorption/ionization‐mass spectrometry imaging for analysis of antibiotics in grass carp tissues

“…11 The inhomogeneity of co-crystallization is fatal to the accuracy and repeatability of subsequent MALDI-MSI results. 12,13 To increase the applicability of MALDI-MSI in the detection of antibiotics, it is essential to introduce a more appropriate matrix. 14,15 Moreover, the widespread and frequent occurrence of abuse, misuse, and residual events of antibiotics requires the immediate development of a novel matrix.…”

“…However, the unexpected background signals of traditional matrices in the low‐molecular region (<500 Da) result in the complex spectrum and redundant interferences in the analysis of antibiotics 11 . The inhomogeneity of co‐crystallization is fatal to the accuracy and repeatability of subsequent MALDI‐MSI results 12,13 . To increase the applicability of MALDI‐MSI in the detection of antibiotics, it is essential to introduce a more appropriate matrix 14,15 .…”