A Call for Randomization in Clinical Trials of Liver Machine Perfusion Preservation

Are we on track to increase organ utilization? An analysis of machine perfusion preservation for liver transplantation in the United States

BACKGROUND

Efforts to improve the quality of marginal grafts for transplantation are essential. Machine perfusion preservation appears as a promising solution.

METHODS

The United Network for Organ Sharing (UNOS) database was queried for deceased liver donor records between 2016 and 2022. The primary outcome of interest was the organ nonutilization rate. Long-term graft and patient survival among extended criteria donors (ECDs) were also analyzed.

RESULTS

During the study period, out of 54 578 liver grafts recovered for transplant, 5085 (9.3%) were nonutilized. Multivariable analysis identified normothermic machine perfusion (NMP) preservation as the only predictor associated with a reduction in graft nonutilization (OR = 0.12; 95% CI = 0.06-0.023, p < 0.001). Further analysis of ECD grafts that were transplanted revealed comparable 1-,2- and 3-years graft survival (89%/88%/82% vs. 90%/85%/81%, p = 0.60), and patient survival (92%/91%/84% vs. 92%/88%/84%, p = 0.65) between grafts that underwent MP vs. those who did not, respectively.

CONCLUSIONS

Liver nonutilization rates in the United States are at an all-time high. Available data, most likely including cases from clinical trials, showed that NMP reduced the odds of organ nonutilization by 12% among the entire deceased donor pool and by 16% among grafts from ECD. Collective efforts and further evidence reflecting day-to-day clinical practice are needed to fully reach the potential of MP for liver transplant.

Activation of farnesoid X receptor enhances the efficacy of normothermic machine perfusion in ameliorating liver ischemia-reperfusion injury

The shortage of transplant organs remains a severe global issue. Normothermic machine perfusion (NMP) has the potential to increase organ availability, yet its efficacy is hampered by the inflammatory response during machine perfusion. Mouse liver ischemia-reperfusion injury (IRI) models, discarded human liver models, and porcine marginal liver transplantation models were utilized to investigate whether farnesoid X receptor (FXR) activation could mitigate inflammation-induced liver damage. FXR expression levels before and after reperfusion were measured. Gene editing and coimmunoprecipitation techniques were employed to explore the regulatory mechanism of FXR in inflammation inhibition. The expression of FXR correlates with the extent of liver damage after reperfusion. Activation of FXR significantly suppressed the inflammatory response triggered by IRI, diminished the release of proinflammatory cytokines, and improved liver function recovery during NMP, assisting discarded human livers to reach transplant standards. Mechanistically, FXR disrupts the interaction between p65 and p300, thus inhibiting modulating the nuclear factor kappa-B signaling pathway, a key instigator of inflammation. Our research across multiple species confirms that activating FXR can optimize NMP by attenuating IRI-related liver damage, thereby improving the utilization of marginal livers for transplantation.

Obstacles to implement machine perfusion technology in routine clinical practice of transplantation: Why are we not there yet?

Machine perfusion of solid human organs is an old technique, and the basic principles were presented as early as 1855 by Claude Barnard. More than 50 years ago, the first perfusion system was used in clinical kidney transplantation. Despite the well-known benefits of dynamic organ preservation and significant medical and technical development in the last decades, perfusion devices are still not in routine use. This article describes the various challenges to implement this technology in practice, critically analyzing the role of all involved stakeholders, including clinicians, hospitals, regulatory, and industry, on the background of regional differences worldwide. The clinical need for this technology is discussed first, followed by the current status of research and the impact of costs and regulations. Considering the need for strong collaborations between clinical users, regulatory bodies, and industry, integrated road maps and pathways required to achieve a wider implementation are presented. The role of research development, clear regulatory pathways, and the need for more flexible reimbursement schemes is discussed together with potential solutions to address the most relevant hurdles. This article paints an overall picture of the current liver perfusion landscape and highlights the role of clinical, regulatory, and financial stakeholders worldwide.

The Emerging Role of Viability Testing During Liver Machine Perfusion

The transplant community continues to be challenged by the disparity between the need for liver transplantation and the shortage of suitable donor organs. At the same time, the number of unused donor livers continues to increase, most likely attributed to the worsening quality of these organs. To date, there is no reliable marker of liver graft viability that can predict good posttransplant outcomes. Ex situ machine perfusion offers additional data to assess the viability of donor livers before transplantation. Hence, livers initially considered unsuitable for transplantation can be assessed during machine perfusion in terms of appearance and consistency, hemodynamics, and metabolic and excretory function. In addition, postoperative complications such as primary nonfunction or posttransplant cholangiopathy may be predicted and avoided. A variety of viability criteria have been used in machine perfusion, and to date there is no widely accepted composition of criteria for clinical use. This review discusses potential viability markers for hepatobiliary function during machine perfusion, describes current limitations, and provides future recommendations for the use of viability criteria in clinical liver transplantation.

The economic impact of machine perfusion technology in liver transplantation

INTRODUCTION

Several clinical studies have demonstrated the safety, feasibility, and efficacy of machine perfusion in liver transplantation, although its economic outcomes are still underexplored. This review aimed to examine the costs related to machine perfusion and its associated outcomes.

METHODS

Expert opinion of several groups representing different machine perfusion modalities. Critical analysis of the published literature reporting the economic outcomes of the most used techniques of machine perfusion in liver transplantation (normothermic and hypothermic ex situ machine perfusion and in situ normothermic regional perfusion).

RESULTS

Machine perfusion costs include disposable components of the perfusion device, perfusate components, personnel and facility fees, and depreciation of the perfusion device or device lease fee. The limited current literature suggests that although this upfront cost varies between perfusion modalities, its use is highly likely to be cost-effective. Optimization of the donor liver utilization rate, local conditions of transplant programs (long waiting list times and higher MELD scores), a decreased rate of complications, changes in logistics, and length of hospital stay are potential cost savings points that must highlight the expected benefits of this intervention. An additional unaccounted factor is that machine perfusion optimizing donor organ utilization allows patients to be transplanted earlier, avoiding clinical deterioration while on the waiting list and the costs associated with hospital admissions and other required procedures.

CONCLUSION

So far, the clinical benefits have guided machine perfusion implementation in liver transplantation. Albeit there is data suggesting the economic benefit of the technique, further investigation of its costs to healthcare systems and society and associated outcomes is needed.