Abstract 165: Immediate Internalization of Transplanted Mitochondria in Circulatory Immune Cells After Cardiac Arrest Resuscitation in Rats

Abstract

Background: Mitochondrial transplantation (MTx) is an innovative technology that has the potential effect for attenuating ischemia reperfusion injury. We previously demonstrated that MTx significantly improves survival and neurological outcomes after cardiac arrest (CA) and resuscitation in rats. However, the underlying mechanism by which MTx enhances CA outcomes remains unclear. Aim: To investigate the hypothesis that injected donor mitochondria are rapidly internalized by circulatory immune cells, particularly monocytes/macrophages, which play crucial roles in post-CA inflammatory signaling. Methods and Results: Adult male Sprague-Dawley rats underwent sham operation or 10 minutes of asphyxial CA followed by resuscitation with CPR. Either a respiration buffer as a vehicle or donor mitochondria labeled with MitoTracker Deep Red (MTDR) was intravenously injected to animals of both groups. In the CA groups, the injection was performed upon achieving spontaneous circulation. Serial blood samples were collected at 30, 75, and 150 seconds after injection. Flow cytometry analysis revealed that a marked increase of MTDR-positive ratios, peaking at 30 seconds, in CD45 + leukocytes, CD3 + T lymphocytes, and CD11b/c + monocytes/macrophages in the MTx-treated CA group compared to the other groups (Figure A). Notably, in sham-operated rats with donor mitochondrial injection, only minimal donor mitochondria were found in the circulating immune cells at those time points. Brain and spleen 1 h post-CA with MTx showed enhanced signals of MTDR measured using an in vivo imaging system, indicating successful transfer of injected mitochondria to organs (Figure B). Conclusion: Our findings demonstrate rapid internalization of injected mitochondria by circulatory immune cells after MTx in post-CA rats, suggesting a pivotal role for circulating immune cells in the mechanism underlying the beneficial effects of MTx in CA resuscitation.