To image or not to image: Use of imaging mass spectrometry in biomedical lipidomics.

Lipid imaging mass spectrometry (LIMS) allows for establishing the bidimensional distribution of lipid species within a tissue section. One of the main advantages is the generation of spatial information on lipid species distribution at a spatial (lateral) resolution bordering on single-cell resolution with no need to isolate cells. Thus, LIMS images demonstrate, with a level of detail never described before, that lipid profiles are highly sensitive to cell type and pathophysiological state. The wealth and relevance of the information conveyed by LIMS makes up for the lack of a separation stage before sample injection into the mass analyzer, which can somehow be circumvented by other means. Hence, the possibility of describing the lipidome at the cellular level while preserving the microenvironment offers an incomparable opportunity to investigate physiological and pathological contexts. However, to fully grasp the biological implications of the lipid profiles, it is essential to contextualize LIMS data within the broader multiscale 'omic' landscape, entailing genomics, epigenomics, and proteomics, each offering a unique window into the regulatory layers of the cell. In this line, the number of techniques that can be combined with LIMS to delve into the molecular mechanisms underlying differential lipid profiles is continuously increasing. Herein, we aim to describe the key features of LIMS analyses, from sample preparation to data interpretation, as well as the current methodologies to enrich and complete the final outcome. While the field is rapidly advancing, we consider there is solid evidence to foresee the incorporation of LIMS into clinical environments.