Fig. 5: High-dimensional characterization of metabolic alterations in myocardial infarction by spatial trajectories and multimodal Raman-MALDI imaging.

a H&E Staining of a murine sagittal heart section after induction of myocardial infarction by transient ligature of the LAD. Dashed box denotes cardiac tissue with transition from healthy to ischemic/reperfused (I/R) myocardium. Black arrow points at the ligation site. Long red arrow depicts spatial trajectory passing the infarct border and heading towards the ischemic heart region. Scale bar 1 mm. n = 1 individual sample. b Heatmap of log2 normalized intensity changes in Raman fingerprint spectrum along this trajectory. c Intensity shifts of three characteristic peaks for NADH and glucose were tracked along the trajectory and show a specific pattern when crossing the infarct border and entering the ischemic heart region. Grey ribbons are 0.95 confidence intervals. d–f Intensity alterations in a sham-operated heart, where the suture around the LAD was not closed. Grey ribbons are 0.95 confidence intervals. n = 1 individual sample. Scale bar 1 mm. g Illustration of the multi-omics approach of combining Raman and MALDI imaging on the same tissue regions. For best fitting, resolution of Raman imaging was 5 times higher than MALDI imaging (10 vs. 50 µm). h, left Cluster analysis of both datasets separately. Both methods uncover distinct spatially organized clusters at the infarct border region. h, right Cluster analysis of overlaying data points after spatial co-registration of Raman and MALDI scans. i Integration of these datasets into a multimodal analysis using weighted nearest neighbor (wnn) dimension reduction and cluster analysis (top). The resulting cluster image (bottom) fits well with the boundaries of the infarcted region identified in the H&E staining (Supplementary Fig. 12). j, k Volcano plot of n = 3 individual hearts exploring spectral differences from cluster-identified I/R border regions vs. remote (healthy) regions. Welch two-sided, paired t-test. l Average Raman spectrum for I/R border regions and remote regions. m Heatmap of standardized mean difference between I/R and remote regions from n = 3 individual hearts. Raman-only section with modalities only identifiable by Raman spectroscopy, MALDI-only those using MALDI imaging. Raman + MALDI show reproducibility of measurements across the different methods. Raman wavenumbers (no decimals) and m/z values (three decimal places) are shown on the left of the heatmap.