(618c) Imaging Mass Cytometry for 30-Plex Single-Cell Spatial Characterization of Cardiac Allograft Dysfunction

Organ transplantation is the preferred treatment for terminal organ failure with over 40,000 organ transplants performed in the United States in 2021. However, immunological allograft rejection is the major barrier to long term survival, and further understanding the mechanisms of rejection will improve treatments and prolong graft survival. To this end, heart transplant patients undergo regular endomyocardial biopsies (EMB) in which small tissue samples are taken directly from the graft to provide snapshots of allograft rejection. Imaging mass cytometry (IMC) can maximize the information obtained from EMBs by simultaneously detecting up to 40 markers in fixed tissue sections with subcellular resolution.

In this study, we established IMC in the field of heart transplantation and investigated the immune response in cardiac allograft rejection. We designed and validated a cardiac IMC 30-antibody panel and analyzed both allograft rejection and no rejection EMBs. Furthermore, an analysis pipeline enabled cell segmentation, phenotyping, and quantification of over a dozen major cell types in 84 patients. We also investigated the spatial relationships between cells and probed the alloimmune microenvironment using complement, proliferation, and cytokine markers. To our knowledge, this is the first reported cardiac IMC study and demonstrates the potential of IMC to detect new biomarkers, suggest mechanisms of dysfunction, and identify therapeutic targets in both cardiology and allograft rejection.