Spatiotemporal metabolic mapping of ex-situ preserved hearts subjected to dialysis by integration of bio-SPME sampling with non-targeted metabolipidomic profiling.

Background: Normothermic ex situ heart perfusion (ESHP) has emerged as a valid modality for advanced cardiac allograft preservation and conditioning prior to transplantation though myocardial function declines gradually during ESHP thus limiting its potential for expanding the donor pool. Recently, the utilization of dialysis has been shown to preserve myocardial and coronary vasomotor function. Herein, we sought to determine the changes in myocardial metabolism that could support this improvement.

Results: Male Yorkshire porcine hearts were subjected to ESHP for 8 h with or without dialysis. Alterations in metabolism were studied with an innovative in vivo solid-phase microextraction (SPME) technology coupled with global metabolite profiling at 15 min, 1.5, 4, and 8 h of perfusion. Bio-SPME sampling was performed by inserting SPME fibres coated with a PAN-based extraction phase containing mixed-mode (C8+benzenesulfonic acid) functionalities into the myocardium to a depth of their entire 8 mm coating or immersing them in the perfusate, followed by a 20-min extraction period for the analytes of interest. Dialyzed hearts demonstrated improved bioenergetics as evidenced by accelerated purine metabolism and less pronounced accumulation of intermediates of fatty acid β/ω-oxidation. Metabolic waste accumulation such as pro-inflammatory lipid mediators (e.g., leukotrienes) was mitigated thereby supporting the process of resolution of inflammation through excretion of specialized pro-resolving mediators (resolvins D1/D2, E2, protecin D1).

Significance: Through implementing the unique analytical pipeline we demonstrated that the addition of dialysis may preserve cardiac metabolism allowing for prolonged ESHP. This strategy has the potential to facilitate high-risk donor organs' reconditioning prior to transplantation.