Macrophage-Derived Extracellular Vesicles (EVs) Have Functional and Metabolic Effects on Cardiac Grafts in a Preclinical Model of Donation After Circulatory Death (DCD)

Abstract

<h3>Purpose</h3> Donation after circulatory death (DCD) could substantially increase cardiac graft availability. Cardiac ischemia and reperfusion, as occurs during DCD, can trigger the recruitment of macrophages as well as their polarization from the M0 to M1 state, which may occur in parallel with increased glycogen turnover and pentose phosphate flux. Extracellular vesicles (EVs) can transmit the metabolic status of their parent cell to recipient cells. As post-ischemic glucose metabolism is recognized to affect the cardiac recovery, we investigated the effects of M0 and M1 macrophage-derived EV administration during reperfusion on post-ischemic functional recovery and glucose metabolism using an isolated rat heart model of DCD. <h3>Methods</h3> Hearts isolated from adult, male rats were aerobically perfused for 20 minutes, followed by 27 minutes continued perfusion or 27 minutes of warm, global ischemia, and 60 minutes aerobic reperfusion with or without the intravascular administration of EVs. Four experimental groups were examined: 1) continued perfusion, no EVs (No ISCH); 2) ischemia, no EVs (ISCH); 3) ischemia with EVs from M0 macrophages (ISCH M0); 4) ischemia with EVs from M1 macrophages (ISCH M1). Contractile and metabolic post-ischemic recovery were evaluated. Data are reported as mean ± standard deviation. <h3>Results</h3> Left ventricular (LV) work (heart rate-developed pressure product) at 60 minutes reperfusion was significantly decreased in ISCH (17 ± 3) and ISCH M1 (19 ± 3), but not in ISCH M0 (22 ± 3), compared to No ISCH (26 ± 4 mmHg*beats*min^{−1 *}10³; p<0.05 for both). Rates of glycolysis during reperfusion were not different among groups; however, glycogen content was significantly lower after 60 min reperfusion in ISCH M1 (8 ± 2) compared to ISCH M0 (17 ± 3 μmol/g dry; p<0.05). <h3>Conclusion</h3> The ischemia-induced reduction in left ventricular work was improved with M0-, but not M1-, derived EVs. M0 and M1-derived EVs also differentially affected glucose metabolism; M1-macrophage derived EVs limited glycogen content, possibly by increasing glycogen use or turnover and stimulating recipient cells to mimic parent cell metabolic phenotypes. Circulating EVs in the ex-situ perfusion of DCD hearts may be possible targets for modulating metabolic function and optimizing graft recovery following warm ischemia.