Mass spectrometry-based phospholipid imaging: methods and findings

ABSTRACT

Introduction: Imaging is a technique used for direct visualization of the internal structure or distribution of biomolecules of a living system in a two-dimensional or three-dimensional fashion. Phospholipids are important structural components of biological membranes and have been reported to be associated with various human diseases. Therefore, the visualization of phospholipids is crucial to understand the underlying mechanism of cellular and molecular processes in normal and diseased conditions.

Areas covered: Mass spectrometry imaging (MSI) has enabled the label-free imaging of individual phospholipids in biological tissues and cells. The commonly used MSI techniques include matrix-assisted laser desorption ionization-MSI (MALDI-MSI), desorption electrospray ionization-MSI (DESI-MSI), and secondary ion mass spectrometry (SIMS) imaging. This special report described those methods, summarized the findings, and discussed the future development for the imaging of phospholipids.

Expert opinion: Phospholipids imaging in complex biological samples has been significantly benefited from the development of MSI methods. In MALDI-MSI, novel matrix that produces homogenous crystals exclusively with polar lipids is important for phospholipids imaging with greater efficiency and higher spatial resolution. DESI-MSI has the potential of live imaging of the biological surface while SIMS is expected to image at the subcellular level in the near future.

KEYWORDS:

• Phospholipid
• mass spectrometry imaging
• MALDI-MSI
• DESI-MSI
• SIMS imaging

Article highlights

• Mass spectrometry imaging (MSI) is a powerful method for imaging specific phospholipids (PLs) in tissues and cells.

• The potential of MSI of either single or multiple PLs for the development of therapeutic agents, biomarkers, and predictive factors for diseases is reviewed.

• The current states of MALDI-MSI, DESI-MSI, and SIMS-MSI on tissue PL imaging are assessed and discussed.

• By image reconstruction, conventional 2D imaging can be applied in 3D PL imaging.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This paper was funded by AMED: JP20gm0910004; JSPS KAKENHI: JP18H05268; MEXT/JSPS KAKENHI: JP15H05898B1; MEXT Project for promoting public utilization of advanced research infrastructure (Imaging Platform): JPMXS0410300220.