Ethics of allocation of donor organs

High throughput method for simultaneous screening of membrane permeability and toxicity for discovery of new cryoprotective agents

Cryoprotective agent (CPA) toxicity is the most limiting factor impeding cryopreservation of critically needed tissues and organs for transplantation and medical research. This limitation is in part due to the challenge of rapidly screening compounds to identify candidate molecules that are highly membrane permeable and non-toxic at high concentrations. Such a combination would facilitate rapid CPA permeation throughout the sample, enabling ice-free cryopreservation with minimal toxicity. This study presents a new method for rapidly assessing the cell membrane permeability and toxicity of candidate CPAs. The new method enables ~ 100 times faster permeability measurement than previous methods, while also allowing assessment of CPA toxicity using the same 96-well plate. We tested five commonly used CPAs and 22 less common ones at both 4 °C and room temperature, with 23 of them passing the screening process based on their favorable toxicity and permeability properties. Considering its advantages such as high throughput measurement of membrane permeability along with simultaneous toxicity assessment, the presented method holds promise as an effective initial screening tool to identify new CPAs for cryopreservation.

Transplant benefit-based offering of deceased donor livers in the United Kingdom

BACKGROUND & AIMS

The National Liver Offering Scheme (NLOS) was introduced in the UK in 2018 to offer livers from deceased donors to patients on the national waiting list based, for most patients, on calculated transplant benefit. Before NLOS, livers were offered to transplant centres by geographic donor zones and, within centres, by estimated recipient need for a transplant.

METHODS

UK Transplant Registry data on patient registrations and transplants were analysed to build statistical models for survival on the list (M1) and survival post-transplantation (M2). A separate cohort of registrations - not seen by the models before - was analysed to simulate what liver allocation would have been under M1, M2 and a transplant benefit score (TBS) model (combining both M1 and M2), and to compare these allocations to what had been recorded in the UK Transplant Registry. The number of deaths on the waiting list and patient life years were used to compare the different simulation scenarios and to select the optimal allocation model. Registry data were monitored, pre- and post-NLOS, to understand the performance of the scheme.

RESULTS

The TBS was identified as the optimal model to offer donation after brain death (DBD) livers to adult and large paediatric elective recipients. In the first 2 years of NLOS, 68% of DBD livers were offered using the TBS to this type of recipient. Monitoring data indicate that mortality on the waiting list post-NLOS significantly decreased compared with pre-NLOS (p <0.0001), and that patient survival post-listing was significantly greater post- compared to pre-NLOS (p = 0.005).

CONCLUSIONS

In the first two years of NLOS offering, waiting list mortality fell while post-transplant survival was not negatively impacted, delivering on the scheme's objectives.

IMPACT AND IMPLICATIONS

The National Liver Offering Scheme (NLOS) was introduced in the UK in 2018 to increase transparency of the deceased donor liver offering process, maximise the overall survival of the waiting list population, and improve equity of access to liver transplantation. To our knowledge, it is the first scheme that offers organs based on statistical prediction of transplant benefit: the transplant benefit score. The results are important to the transplant community - from healthcare practitioners to patients - and demonstrate that, in the first two years of NLOS offering, waiting list mortality fell while post-transplant survival was not negatively impacted, thus delivering on the scheme's objectives. The scheme continues to be monitored to ensure that the transplant benefit score remains up-to-date and that signals that suggest the possible disadvantage of some patients are investigated.

High throughput method for simultaneous screening of membrane permeability and toxicity for discovery of new cryoprotective agents

Vitrification is the most promising method for cryopreservation of complex structures such as organs and tissue constructs. However, this method requires multimolar concentrations of cell-permeant cryoprotective agents (CPAs), which can be toxic at such elevated levels. The selection of CPAs for organ vitrification has been limited to a few chemicals; however, there are numerous chemicals with properties similar to commonly used CPAs. In this study, we developed a high-throughput method that significantly increases the speed of cell membrane permeability measurement, enabling ~100 times faster permeability measurement than previous methods. The method also allows assessment of CPA toxicity using the same 96-well plate. We tested five commonly used CPAs and 22 less common ones at both 4 °C and room temperature, with 23 of them passing the screening process based on their favorable toxicity and permeability properties. Considering its advantages such as high throughput measurement of membrane permeability along with simultaneous toxicity assessment, the presented method holds promise as an effective initial screening tool to identify new CPAs for cryopreservation.

Predicting Donor Selection and Multi-Organ Transplantation within Organ Procurement Organizations Using Machine Learning

Organ procurement organizations (OPOs) play a crucial role in the field of organ transplantation, serving as key intermediaries in the process of organ donation. However, despite their vital function, there exists a pressing issue of transparency within the organ allocation process. This opacity not only impedes the overall effectiveness of OPOs but also raises ethical and societal concerns regarding organ distribution. This study utilizes the recently published ORCHID dataset, containing 133,101 records of organ donor referrals, to understand organ procurement and donor selection strategies in OPOs using machine learning (ML). We developed seven ML classification models to predict donor selection and the likelihood of at least four organs being suitable for transplantation, in line with established definitions of multi-organ transplantation. The models demonstrated variable recall values for donor selection, ranging between 0.62 and 0.80, while achieving consistently high performance across other evaluation metrics, notably with AUC values exceeding 0.95. Particularly in the context of multi-organ transplant predictions, the models exhibited remarkable effectiveness, with recall values spanning from 0.88 to 0.98 and AUC metrics consistently above 0.97. Administrative milestones and particular organ transplants were identified as key determinants in the organ allocation process. This study's findings suggest significant opportunities to improve organ allocation strategies by focusing on the optimization of administrative practices, highlighting their substantial impact on transplantation success rates.

Xenotransplantation could either be a friend or foe of healthcare equity

Chisholm-Burns et al. discuss the substantial shortage of organs available for transplantation, with disparities in access amongst some racial and ethnic groups. The authors suggest that while xenotransplantation can potentially increase organ availability, it also has the potential to further embed inequities in transplant care.

Differential in Kidney Graft Years on the Basis of Solitary Kidney, Simultaneous Liver-Kidney, and Kidney-after-Liver Transplants

BACKGROUND

The number of simultaneous liver-kidney (SLK) transplants has significantly increased in the United States. There has also been an increase in kidney-after-liver transplants associated with 2017 policy revisions aimed to fairly allocate kidneys after livers. SLK and kidney-after-liver candidates are prioritized in allocation policy for kidney offers ahead of kidney-alone candidates.

METHODS

We compared kidney graft outcomes of kidney-alone transplant recipients with SLK and kidney-after-liver transplants using paired kidney models to mitigate differences among donor risk factors. We evaluated recipient characteristics between transplant types and calculated differential graft years using restricted mean survival estimates.

RESULTS

We evaluated 3053 paired donors to kidney-alone and SLK recipients and 516 paired donors to kidney-alone and kidney-after-liver recipients from August 2017 to August 2022. Kidney-alone recipients were younger, more likely on dialysis, and Black race. One-year and 3-year post-transplant kidney graft survival for kidney-alone recipients was 94% and 86% versus SLK recipients 89% and 80%, respectively, P < 0.001. One-year and 3-year kidney graft survival for kidney-alone recipients was 94% and 84% versus kidney-after-liver recipients 93% and 87%, respectively, P = 0.53. The additional kidney graft years for kidney-alone versus SLK transplants was 21 graft years/100 transplants (SEM=5.0) within 4 years post-transplantation, with no significant difference between kidney-after-liver and kidney-alone transplants.

CONCLUSIONS

Over a 5-year period in the United States, SLK transplantation was associated with significantly lower kidney graft survival compared with paired kidney-alone transplants. Most differences in graft survival between SLK and kidney-alone transplants occurred within the first year post-transplantation. By contrast, kidney-after-liver transplants had comparable graft survival with paired kidney-alone transplants.

The history of ethical principles in liver transplant organ allocation in the United States: how historical and proposed allocations system fare in balancing utility vs. urgency and justice vs. pragmatism

PURPOSE OF REVIEW

The United States (US) liver transplant community is processing changes to the allocation system and developing a new proposal that will result in even greater change. This review evaluates the ethical implications of these decisions, focusing on two sets of competing ethical principles (Urgency vs. Utility and Justice vs. Pragmatism).

RECENT FINDINGS

About four years ago, the Organ Procurement and Transplantation Network (OPTN) implemented the Acuity Circle Model to replace the geographic boundaries of organ procurement organizations (OPOs). Here, we review how effectively this model reduced regional variation in access and improved waitlist survival. Likewise, the OPTN is planning to transition to a continuous distribution model which will redefine the scoring systems for allocation. We will discuss how the ethical priorities discussed above should be considered while developing the new system.

SUMMARY

Every change in organ allocation policy must balance competing ethical imperatives. Although our community's emphasis on urgency over utility is appropriate, we should study the potential benefits of considering utility in the system. Meanwhile, our push for more Justice in the system should remain our imperative and Pragmatism should only be considered to minimize the costs of these changes.

Uterine Transplantation and Fertility Preservation: A Hopeful Horizon for Cancer Survivors

Uterine transplantation, a groundbreaking medical intervention, stands as a beacon of hope for cancer survivors grappling with the dual challenges of a cancer diagnosis and potential fertility loss due to aggressive treatments. This review provides a comprehensive exploration of uterine transplantation as an innovative solution for fertility preservation in the context of cancer survivorship. The multifaceted discussion encompasses the impact of cancer on fertility, the imperative of fertility preservation, and the evolution of uterine transplantation as a transformative procedure. The post-transplantation care section delves into the intricacies of recovery, the delicate balance of immunosuppressive therapy, and the ongoing support required for recipients to embrace the full spectrum of reproductive possibilities and overall well-being. Ethical considerations surrounding uterine transplantation, including donor selection, risk assessment, and societal perspectives, are critically examined to navigate the ethical landscape of this evolving field. In conclusion, uterine transplantation is presented as a medical breakthrough and a symbol of interdisciplinary collaboration, resilience, and unwavering hope. The review underscores the role of collaborative efforts among medical professionals, researchers, ethicists, and psychologists in advancing this transformative field. Looking to the future, uterine transplantation signifies a paradigm shift in fertility preservation, offering a tangible path toward parenthood for cancer survivors. The procedure, grounded in science, ethics, and compassion, illuminates the way forward, inspiring a future where fertility preservation becomes an attainable reality for those whose reproductive dreams were once compromised by cancer treatments.