Metabolic niches: MALDI imaging reveals lipidomic heterogeneity in the human heart

The human heart is characterized by aberrant lipid accumulation and remodeling during periods of stress and disease, yet spatially resolved lipidomic profiling of the human heart remains unreported. Here, we employ matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) to map lipid distributions across five anatomical regions of healthy human donor hearts (left and right atrium, left and right ventricle, and interventricular septum). Cryosections of donor hearts from healthy subjects were thaw-mounted onto indium tin oxide slides, coated with 2,5-dihydroxyacetophenone, and analyzed on a Bruker timsTOF fleX mass spectrometer in positive and negative ionization modes (50-1850 m/z; 20 m raster). Serial sections were stained with hematoxylin and eosin to enable histological co-registration with lipid distributions. We identified 150 unique lipid species with acyl-chain resolution across four glycerophospholipid classes -- phosphatidylcholine (PC), phosphatidylglycerol (PG), phosphatidylethanolamine (PE), and phosphatidylserine (PS) -- with abundances and spatial distributions differing significantly between regions. H&E co-registration further resolved epicardial and myocardial compartments, enabling tissue-specific lipid mapping. These findings establish the first spatially resolved lipidomic atlas of the human heart and provide a framework for identifying region-specific lipid biomarkers of cardiovascular disease.