Fig. 7: PRM-SRS imaging of mouse hippocampal samples.

a–j PRM-SRS hyperspectral detection of cholesterol, PC, and PE in hippocampus samples from young and old mice. Overall intensity of detected lipid subtypes shows distinct patterns, with old brains showing higher cholesterol to PE ratio, but relatively consistent levels of PE and PC. d, i Ratiometric images of cholesterol to PE shows more nuclei with higher cholesterol/PE ratio in the old brains. Selected nuclei are marked by red circles. e, j Ratiometric images of PC relative to PE show higher PC/PE ratio in granule cell nuclei of both young and old brains, but the spatial distribution of the ratio is more heterogeneous in young samples (see nuclei marked by purple arrows). k, l Mass spectrometry (k) shows results consistent with that obtained by ratiometric PRM-SRS imaging (l) for biologically independent mice (n = 4) in each age group. Box plots indicate median and interquartile range, with whiskers indicating 1.5 times the interquartile range. Ratiometric image intensities, corresponding to the ratio of PRM similarity scores of lipid subtypes, are plotted. Error bars represent standard deviation (SD). *p = 0.017; **p = 0.006. m Volcano plot showing significantly altered lipid species (n = 534) between groups. p = 0.05, fold change > 2. Data are filtered such that only lipids present at least three times across all samples are shown. Scale bar, 20 µm. Chol cholesterol, PC phosphatidylcholine, PE phosphatidylethanolamine, GC/MS Gas Chromatography Mass Spectrometry. Source data are provided as a Source Data file.