Antigen Retrieval and Its Effect on the MALDI-MSI of Lipids in Formalin-Fixed Paraffin-Embedded Tissue
Vanna Denti1, Isabella Piga1, Sonia Guarnerio2
1Clinical Proteomics and Metabolomics Unit, Department of Medicine and Surgery, University of Milano-Bicocca, Vedano al Lambro 20854, Italy.
Abstract:
Formalin-fixed paraffin-embedded (FFPE) tissue represents the primary source of clinical tissue and is routinely used in MALDI-MSI studies. However, it is not particularly suitable for lipidomics imaging given that many species are depleted during tissue processing. Irrespective, a number of solvent-resistant lipids remain, but their extraction may be hindered by the cross-link between proteins. Therefore, an antigen retrieval step could enable the extraction of a greater number of lipids and may provide information that is complementary to that which can be obtained from other biomolecules, such as proteins. In this short communication, we aim to address the effect of performing antigen retrieval prior to MALDI-MSI of lipids in FFPE tissue. As a result, an increased number of lipid signals could be detected and may have derived from lipid species that are known to be implicated in the lipid-protein cross-linking that is formed as a result of formalin fixation. Human renal cancer tissue was used as a proof of concept to determine whether using these detected lipid signals were also able to highlight the histopathological regions that were present. These preliminary findings may highlight the potential to enhance the clinical relevance of the lipidomic information obtained from FFPE tissue.
Insights
Antigen retrieval enhances lipid detection in formalin-fixed paraffin-embedded tissues for MALDI-MSI. This method improves lipidomics imaging by increasing detectable lipid signals and highlighting tissue regions.
Area of Science:
- Biochemistry
- Analytical Chemistry
- Pathology
Background:
- Formalin-fixed paraffin-embedded (FFPE) tissues are crucial for clinical studies but challenging for lipidomics due to lipid depletion and protein cross-linking.
- Existing MALDI-MSI methods on FFPE tissues often miss solvent-resistant lipids because of fixation-induced cross-linking.
Purpose of the Study:
- To investigate the impact of antigen retrieval on lipid extraction and detection in FFPE tissues using MALDI-MSI.
- To assess if antigen retrieval can improve lipidomic information and its correlation with histopathology.
Main Methods:
- FFPE human renal cancer tissue samples were subjected to an antigen retrieval step prior to MALDI-MSI.
- Lipid extraction efficiency and signal detection were analyzed post-retrieval.
Main Results:
- Antigen retrieval significantly increased the number of detectable lipid signals in FFPE tissues.
- The detected lipid signals potentially originate from species involved in formalin-induced lipid-protein cross-linking.
- Lipid signals obtained after antigen retrieval helped delineate histopathological regions in the tissue.
Conclusions:
- Antigen retrieval is a valuable pretreatment step to enhance lipidomics analysis of FFPE tissues via MALDI-MSI.
- This approach can recover more lipid information, potentially improving the clinical relevance of FFPE-based lipidomic studies.
