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

• Published in: Biochimica et biophysica acta. General subjects Vol. 1862; no. 1; pp. 51 - 60
• Main Authors: Urban, Christian, Buck, Achim, Siveke, Jens T., Lordick, Florian, Luber, Birgit, Walch, Axel, Aichler, Michaela
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.01.2018
• Subjects: Animals; biopsy; Fixatives - chemistry; formalin; Formalin-fixed and paraffin-embedded; Humans; image analysis; MALDI mass spectrometry imaging; matrix-assisted laser desorption-ionization mass spectrometry; metabolites; Metabolomics; Metabolomics - methods; Mice; microarray technology; PAXgene-fixed and paraffin-embedded; peptides; Peptides - analysis; prospective studies; protein composition; proteins; Proteomics; Proteomics - methods; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; tissue analysis; Tissue Fixation - methods; tissues; Formalin-fixed and paraffin-embedded; Metabolomics; PAXgene-fixed and paraffin-embedded; Proteomics; MALDI mass spectrometry imaging
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2017.10.005

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. [Display omitted] •a non-crosslinking tissue fixative, PAXgene Tissue System, is proposed for metabolomic and proteomic tissue analyses•a systematic comparison between PAXgene-fixed paraffin-embedded and FFPE tissue samples was performed by MALDI MSI•PAXgene-fixed paraffin-embedded tissues yield similar coverage in metabolite and peptide analyses compared to FFPE tissues•the detection of intact proteins is improved by PAXgene fixation