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Biochim Biophys Acta Gen Subj. 2018 Jan;1862(1):51-60. doi: 10.1016/j.bbagen.2017.10.005. Epub 2017 Oct 9.

PAXgene fixation enables comprehensive metabolomic and proteomic analyses of tissue specimens by MALDI MSI.

Author information

1
Research Unit Analytical Pathology, Helmholtz Zentrum München, Neuherberg, Germany. Electronic address: christian.urban@helmholtz-muenchen.de.
2
Research Unit Analytical Pathology, Helmholtz Zentrum München, Neuherberg, Germany. Electronic address: achim.buck@helmholtz-muenchen.de.
3
German Cancer Consortium (DKTK) and German Cancer Research Center, DKFZ, Heidelberg, Germany; Division of Solid Tumor Translational Oncology, German Cancer Consortium (DKTK), Partner Site Essen, West German Cancer Center, University Hospital Essen, Germany. Electronic address: j.siveke@dkfz-heidelberg.de.
4
University Cancer Center Leipzig (UCCL), University Medicine Leipzig, Leipzig, Germany. Electronic address: florian.lordick@medizin.uni-leipzig.de.
5
Institut für Allgemeine Pathologie und Pathologische Anatomie, Technische Universität München, Klinikum rechts der Isar, München, Germany. Electronic address: birgit.luber@tum.de.
6
Research Unit Analytical Pathology, Helmholtz Zentrum München, Neuherberg, Germany. Electronic address: axel.walch@helmholtz-muenchen.de.
7
Research Unit Analytical Pathology, Helmholtz Zentrum München, Neuherberg, Germany. Electronic address: michaela.aichler@helmholtz-muenchen.de.

Abstract

An alcohol-based non-crosslinking tissue fixative, PAXgene Tissue System, has been proposed as alternative fixation method to formalin, providing superior and morphological preservation. To date, metabolites have not been assessed in PAXgene-fixed tissues. The study focuses on a comparison between PAXgene and standard formalin fixation for metabolomic analysis by MALDI mass spectrometry imaging. Therefore, fifty-six samples from seven mice organs were fixed with PAXgene (PFPE) or formalin (FFPE), embedded in paraffin, and processed to a tissue microarray. PAXgene was able to spatially preserve metabolites in organs achieving an overlap of common metabolites ranging from 34 to 78% with FFPE. Highly similar signal intensities and visualization of molecules demonstrated negligible differences for metabolite imaging on PFPE compared to FFPE tissues. In addition, we performed proteomic analysis of intact proteins and peptides derived from enzymatic digestion. An overlap of 33 to 58% was found between FFPE and PFPE tissue samples in peptide analysis with a higher number of PFPE-specific peaks. Analysis of intact proteins achieved an overlap in the range of 0 to 28% owing to the poor detectability of cross-linked proteins in formalin-fixed tissues. Furthermore, metabolite and peptide profiles obtained from PFPE tissues were able to correctly classify organs independent of the fixation method, whereas a distinction of organs by protein profiles was only achieved by PAXgene fixation. Finally, we applied MALDI MSI to human biopsies by sequentially analyzing metabolites and peptides within the same tissue section. Concerning prospective studies, PAXgene can be used as an alternative fixative for multi-omic tissue analysis.

KEYWORDS:

Formalin-fixed and paraffin-embedded; MALDI mass spectrometry imaging; Metabolomics; PAXgene-fixed and paraffin-embedded; Proteomics

PMID:
29024724
DOI:
10.1016/j.bbagen.2017.10.005
[Indexed for MEDLINE]

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