Donation after circulatory death (DCD) offers a promising strategy to expand the donor pool by 20–30%. However, DCD heart grafts suffer from warm ischemia injury, making effective graft viability assessment before transplantation prudent. Current methods for assessing DCD hearts are impacted either by ethical concerns and regional limitations (thoracoabdominal normothermic regional perfusion - taNRP) or by the need for significant resources, expertise, and equipment, with limitations in functional assessment (direct procurement and reperfusion – DPP, via the Organ Care System (OCS) by TransMedics). This study explores an alternative approach to DCD heart preservation, using controlled hypothermia at 6-8 degrees Celsius for up to 7 hours, followed by reanimation using normothermic machine perfusion. DCD grafts were procured from porcine donors after 19 mins of functional warm ischemia, stored via controlled cold static preservation for up to 7 hours and evaluated via a novel method of ex vivo cardiac loading. No functional, biochemical or proteomic differences were observed between DCD cardiac grafts stored via controlled hypothermia for up to 7 hours and DCD grafts reperfused immediately after procurement. These results suggest that controlled hypothermia may be a viable alternative to current DCD preservation methods, eliminating ethical concerns of taNRP and reducing logistical complexity and costs associated with DPP. These findings provide a foundation for a potential shift in DCD heart preservation practices, offering a more effective and cost-efficient approach to expand the donor pool and improve transplantation outcomes.

The authors declare competing interests. D.V is an employee and Founder of Ventri FLO Inc. Dr. S.N.T has patent applications relevant to this study and serves on the Scientific Advisory Board for Sylvatica Biotech Inc., a company focused on developing organ preservation technology. Dr. Rabi is provided funding by Paragonix Inc. S.N.T. and S.A.R?s competing interests are managed by the MGH and Partners HealthCare in accordance with their conflict-of-interest policies. All other authors have no competing interests.

This work was supported by generous funding to S.N.T. from the US National Institutes of Health (K99/R00 HL1431149; R01HL157803). We also gratefully acknowledge funding from the US National Institute of Health (R01DK134590; R24OD034189), National Science Foundation (EEC 1941543), American Heart Association (18CDA34110049), Harvard Medical School Eleanor and Miles Shore Fellowship, Polsky Family Foundation, the Claflin Distinguished Scholar Award on behalf of the MGH Executive Committee on Research, and Shriners Children?s Boston (Grant #BOS-85115). We also thankfully acknowledge support for S.A.R Polsky Family Foundation. The authors would also like to thank the Center for Comparative Medicine and the Knight Surgical Research Lab at Massachusetts General Hospital for animal management. We thank the Mass Spectroscopy, Genomics and Proteomics, and Morphology facilities at Shriners Children?s Boston. Electron microscopy was performed in the Microscopy Core of the Program in Membrane Biology, which is partially supported by an Inflammatory Bowel Disease Grant DK043351 and a Boston Area Diabetes and Endocrinology Research Center (BADERC) Award DK135043.

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