Introduction: Cardiac xenotransplantation is currently the most promising alternative to cardiac allotransplantation. However, despite significant progress in recent years, some challenges remain on the path toward regular clinical application. The implementation of cold non-ischemic preservation using an extracorporeal heart preservation system – consisting, among other components, of a roller pump, a cooler/heater unit, and an oxygenated hyperoncotic cardioplegic solution with nutrients, erythrocytes and hormones - has significantly reduced ischemia-reperfusion injury and perioperative cardiac xenograft dysfunction (PCXD). Nonetheless, the intrinsic vulnerability of porcine hearts to ischemia remains a relevant hurdle. In contexts other than cardiac xenotransplantation, ischemia-reperfusion injury has been associated with ferroptosis - a form of regulated necrosis characterized by iron-dependent phospholipid peroxidation - and ferroptosis inhibitors (ferrostatins) have shown protective effects. Ferroptosis has also been implicated in allotransplantation and multi-organ dysfunction; however, no data are available on its occurrence or therapeutic targeting with ferrostatins in pig-to-baboon cardiac xenotransplantation.
Methods: Plasma samples from n = 17 baboons undergoing orthotopic pig-to-baboon cardiac xenotransplantation were analyzed. Malondialdehyde (MDA), a biomarker of lipid peroxidation, was measured using a colorimetric assay. As perioperative procedures were consistent across all recipients, samples were initially analyzed as a single study group for the first postoperative week. Subsequently, baboons were divided into subgroups based on the course of the experiments, such as the development of pleural effusions or rejection episodes.
Results: Plasma samples from all n = 17 baboons showed a marked increase in free MDA levels at 1 and 6 hours after cessation of cardiopulmonary bypass (CPB) following cardiac xenotransplantation. This elevation declined by the first postoperative day, with no subsequent increase observed in any animals during the first postoperative week. Preliminary analyses at later time points following xenotransplantation revealed a secondary increase in MDA levels in baboons that developed recurrent pleural effusions or exhibited signs of rejection.
Conclusion: This study provides initial insights into the occurrence of wave of lipid peroxidation following pig-to-baboon cardiac xenotransplantation, hinting for involvement of ferroptosis. Based on our findings, we hypothesize that treating recipient baboons - and potentially future patients - with ferrostatins may further reduce ischemia-reperfusion injury, as well as potential adverse effects associated with cold, roller pump-based preservation or CPB, thereby improving post-transplant outcomes. Moreover, our preliminary data suggest that ferrostatin treatment during the later postoperative course may help reduce the incidence of pleural effusions or other inflammatory processes.