A Human Model of Whole‐Body Ischemia‐Reperfusion: Changes in Exosome Release

Abstract

In‐depth knowledge of individual patients' physiology impacts perioperative management, which also impacts efficacy and safety of surgical procedures. Exosomes are a new paradigm in cellular communication, cell stress, and biomarker development that have only recently begun to be addressed in the surgical population. Exosomes, secreted by almost all cells, carry biologically active molecules including DNA, RNA, proteins, lipids, cytokines, growth factors and metabolites. The role of exosomes in the surgical population is not well known and may have major impact on perioperative care and monitoring.Deep hypothermic circulatory arrest (DHCA) is a profound perioperative stress event involving isolation of the systemic vasculature, arrest of the circulation to major organ systems, and whole body ischemia‐reperfusion. DHCA is used for surgical repair of the great vessels including pulmonary thromboendarterectomy (PTE) for which the University of California, San Diego (UCSD) serves as a leading center. Our study tests the novel hypothesis that surgically induced DHCA increases the release of exosomes, alters exosome content and changes the ability of exosomes to affect cellular metabolism and function.Arterial blood was obtained at 5 timepoints in patients undergoing DHCA for PTE: immediately after induction of anesthesia (baseline), after initiation of cardiopulmonary bypass (CPB), at completion of cooling to body temperature of 20C, after circulatory arrests, and after patient is rewarmed and off CPB (chest closure). Blood was centrifuged in heparin tubes to prepare plasma for exosome isolation and nanoparticle tracking analysis (NTA). Additional exosome samples were stored for further immunoblotting, electron microscopic, proteomic, microRNA and in vitro analysis.Particle concentration as measured by NTA immediately after initiation of CPB and at the completion of cooling was decreased from baseline. Thereafter, particle concentration showed an increase after DHCA and a further increase during chest closure at the conclusion of the surgery. Mean particle sizes at each timepoint were within the known size distribution of exosomes.In conclusion, our data show that initiation of CPB and cooling can decrease exosome levels in blood, while whole body ischemia‐reperfusion associated with DHCA in patients is a stimulus for exosome release. Future work will focus on the changes in the proteome and microRNA content of exosomes after DHCA and the physiological consequences of exosome release on intact in vitro cell models. This model also lends itself well to further detailed investigation of tissue and organ specific exosomal responses to ischemia‐reperfusion.Support or Funding InformationR21 AG058174‐01A1 (PI: D Roth) 09/01/2018 – 06/30/2020 Funding Source: NIH/NIA T32 GM121318 (PI: HH Patel; co‐PI: DM Roth) 07/01/16‐06/30/22 Finding Source: NIH/NIGMSThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.