Preservation of circulatory death donor Rat hearts using hemoglobin-based oxygen carriers for normothermic machine perfusion: enhancing viability and functionality.

INTRODUCTION: Ischemia-reperfusion injury (IRI) remains a critical barrier to successful transplantation of donation after circulatory death (DCD) hearts, compromising myocardial viability through oxidative stress, inflammation, and apoptotic pathways. Hemoglobin-based oxygen carriers (HBOCs) are being explored as substitutes for blood and red blood cells (RBCs) in ex vivo heart perfusion (EVHP) to mitigate myocardial IRI. METHODS: This study compared the efficacy of HBOC vs. conventional blood or RBC perfusion in attenuating IRI using a rat DCD heart EVHP and transplantation model. Donor hearts were perfused ex vivo for four hours with blood, RBCs, or HBOC. Myocardial function was assessed by hemodynamic parameters, blood gas analysis, and biomarkers of oxidative stress, apoptosis, and inflammation. Histological and molecular analyses were performed after transplantation. RESULTS: HBOC perfusion significantly reduced myocardial IRI and inflammation, with lower levels of 4-hydroxynonenal (4-HNE) and pro-inflammatory cytokines compared with blood perfusion. Hemodynamic performance, including developed pressure and ±dp/dt, was superior in the HBOC group. In contrast, blood-perfused hearts exhibited elevated potassium and lactate levels, indicating ongoing injury. Post-transplantation analyses demonstrated reduced structural damage and inflammatory infiltration in HBOC-treated hearts. DISCUSSION: These findings indicate that HBOC ex vivo perfusion exerts dual cytoprotective effects by limiting ischemic injury through optimized oxygen delivery and attenuating reperfusion-associated injury cascades via antioxidant and anti-inflammatory mechanisms. EVHP with HBOC represents a promising preservation strategy for DCD hearts, with the potential to reduce myocardial IRI and improve post-transplant cardiac function in marginal donor hearts.