tandard preservation of donor livers is performed by flushing the organ with a cold solution at the time of procurement, which is followed by static storage on ice. This approach reduces liver metabolic activity, allowing safe storage for up to 12-18 h (refs. 1,2). Recently, the combination of supercooling with subzero storage (−4 °C) and hypothermic, as well as subnormothermic, machine perfusion achieved an extension of the preservation time of human livers up to 27 h (ref. 2). By contrast, human livers can also be kept metabolically fully active for up to 24 h by supplying normothermic blood or oxygenated fluids in a controlled environment by machine perfusion 1,3-5. The possibility of repairing poor-quality livers sufficiently to enable transplantation requires preserving metabolically active livers 1,3 for several days. Accordingly, the need for long-term organ preservation technology has been endorsed by multiple private and governmental initiatives 1. However, currently used normothermic machine perfusion technologies have been used only for a relatively short time period (for example, a median perfusion time of 9 h (ref. 5)), to successfully maintain hemodynamics, perfusate oxygenation and temperature. We sought to extend perfusion time beyond 24 h by engineering a perfusion machine that recapitulates additional core body functions that are critical to liver health. We chose 7-d as a target because this time period has been shown to offer a credible time frame for inducing clinically relevant liver regeneration in patients undergoing complex liver resection 6-8. Under physiologic conditions, the liver, which constitutes 2.5% of body weight, receives 25% of the blood output of the heart and performs >5,000 functions 9. It has a unique dual vascular supply with high-pressure, oxygen-rich arterial blood entering through the hepatic artery and low-pressure, oxygen-reduced portal vein blood draining the abdominal viscera. Its high metabolic activity produces waste products that are excreted in the bile or removed by hepatic macrophages or the kidneys. The metabolic profile is largely controlled by pancreatic hormones, including insulin and glucagon. Our perfusion technology, developed in the "Liver4Life project", includes automated control of glucose levels by injection of insulin and glucagon, a dialysis membrane for waste-product removal, regulation of oxygenation and liver movement to prevent pressure necrosis. Results Liver perfusion machine. Our perfusion machine (Fig. 1a,b) recapitulates blood supply through the two vascular entries of the liver, the hepatic artery and portal vein. The hepatic artery is supplied with oxygen-rich blood at elevated pressure (mean arterial pressure (MAP) ≥ 65 mmHg) in a pulsatile manner (Fig. 1c), whereas the portal vein receives blood at low pressure (around 5-10 mmHg) with a reduced oxygen content (venous blood, non-pulsatile). The system maintains oxygen saturation of 65% in the vena cava by continuously adjusting oxygen content in the portal vein (Fig. 1d). In vivo, nutr...

Introduction The use of normothermic liver machine perfusion to repair injured grafts ex situ is an emerging topic of clinical importance. However, a major concern is the possibility of microbial contamination in the absence of a fully functional immune system. Here, we report a standardized approach to maintain sterility during normothermic liver machine perfusion of porcine livers for one week. Methods Porcine livers (n = 42) were procured and perfused with blood at 34°C following aseptic technique and standard operating procedures. The antimicrobial prophylaxis was adapted and improved in a step‐wise manner taking into account the pathogens that were detected during the development phase. Piperacillin‐Tazobactam was applied as a single dose initially and modified to continuous application in the final protocol. In addition, the perfusion machine was improved to recapitulate partially the host's defense system. The final protocol was tested for infection prevention during one week of perfusion. Results During the development phase, microbial contamination occurred in 27 out of 39 (69%) livers with a mean occurrence of growth on 4 ± 1.6 perfusion days. The recovered microorganisms suggested an exogenous source of microbial contamination. The antimicrobial agents (piperacillin/tazobactam) could be maintained above the targeted minimal inhibitory concentration (8‐16 mg/L) only with continuous application. In addition to continuous application of piperacillin/tazobactam, partial recapitulation of the host immune system ex situ accompanied by strict preventive measures for contact and air contamination maintained sterility during one week of perfusion. Conclusion The work demonstrates feasibility of sterility maintenance for one week during ex situ normothermic liver perfusion.

Objective: The aim of this study was to maintain long-term full function and viability of partial livers perfused ex situ for sufficient duration to enable ex situ treatment, repair, and regeneration. Background: Organ shortage remains the single most important factor limiting the success of transplantation. Autotransplantation in patients with nonresectable liver tumors is rarely feasible due to insufficient tumor-free remnant tissue. This limitation could be solved by the availability of long-term preservation of partial livers that enables functional regeneration and subsequent transplantation. Methods: Partial swine livers were perfused with autologous blood after being procured from healthy pigs following 70% in-vivo resection, leaving only the right lateral lobe. Partial human livers were recovered from patients undergoing anatomic right or left hepatectomies and perfused with a blood based perfusate together with various medical additives. Assessment of physiologic function during perfusion was based on markers of hepatocyte, cholangiocyte, vascular and immune compartments, as well as histology. Results: Following the development phase with partial swine livers, 21 partial human livers (14 right and 7 left hemi-livers) were perfused, eventually reaching the targeted perfusion duration of 1 week with the final protocol. These partial livers disclosed a stable perfusion with normal hepatic function including bile production (5–10 mL/h), lactate clearance, and maintenance of energy exhibited by normal of adenosine triphosphate (ATP) and glycogen levels, and preserved liver architecture for up to 1 week. Conclusion: This pioneering research presents the inaugural evidence for long-term machine perfusion of partial livers and provides a pathway for innovative and relevant clinical applications to increase the availability of organs and provide novel approaches in hepatic oncology.