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Written by Raquel Mattos-Canedo ‘26
Edited by Shivam Kogar ‘27
Transplant surgeons are at a crossroads. The apparent gap between the population of patients who are in need of an organ transplant and available donors has long been present, but the aging boomer population has left scientists and physicians wondering what exactly can be done (1), if anything. The issue lies in this: Patients in need of organ donations continue to suffer long wait times and uncertainty. Meanwhile, as the boomer population ages, there is a steady increase in patients with end-stage organ diseases. This is not surprising given that organ diseases are common in aging patients. However, life expectancy in the US has also been increasing, growing the percentage of donated organs that are deemed too old to be acceptable for transplants. In other words, the boomer generation is simultaneously increasing the demand for suitable organs for transplant, and decreasing the viability of organs available (1). Clearly, something must change to close the gap between need and availability.
One solution is to extend the current criteria in place for what determines an organ to be suitable for transplantation. How much functional difference is there between a forty year old’s organs and a seventy year old’s? A recent study comparing liver transplants from young and elderly donor groups found that the age of the donor proved to be statistically insignificant in liver transplant outcomes (2). Therefore, extending the criteria for organ transplants could possibly be a long term solution. However, the study observed that depending on a patient’s diagnosis, the impact of donor age will vary, meaning a case-by-case approach may be more appropriate. Another study that focused on kidney transplants concluded that extending criteria for organs can lead to higher risk of rejection and failure to survive in patients compared to using standard criteria. However, the same study found that receiving a kidney from an elderly donor will always benefit survival rate, as compared to staying on the waitlist (1). The differences between both studies highlights the fact that each organ’s functionality over time will follow distinct trends. Clearly,more research needs to be done on the success rates of older organs before accepting it as a long-term solution.
Could there be other solutions beyond settling for aged organs? Scientists have been grappling with the practicality, ethical considerations, and scientific plausibility of an alternative to traditional human transplants, dubbed xenotransplantation. Xenotransplantation is defined as a medical procedure involving transplanting organs or tissues from one species to another (3). In practice, this has mostly been seen with graft transplants from pigs that undergo genetic modification in order to prevent rejection after the transplant. While these genetically modified pigs have been used successfully in grafts, full organ transplants have not been attempted (4). This is because xenotransplantation comes with many variables to consider like zoonotic disease and fundamental phylogenetic differences. Is it possible that an organ from a different species can function inside a human body? And will patients be open to this possibility? Not to mention, from an animal rights angle, there are ethical questions about the donor’s treatment before, during, and after transplantation, ensuring that the wellbeing for all sentient beings are kept in mind. Should this become a more standardized practice, the practicality of breeding and genetically modifying a large number of animals for medical reasons must also be considered. Of course, there will always be public opinion to consider. Even if xenotransplantation is offered as an alternative to standard transplantation, will public opinion even allow it? Will the sheer amount of time, resources, inevitable backlash, and space needed for xenotransplants to be offered as a long-term solution to the human organ shortage, be worth it?
Yet another possible alternative that may be more widely accepted is the development of organs in vitro, otherwise known as lab grown organs. By taking normal somatic cells from a patient, scientists have been able to induce what is called “pluripotency”. Essentially, they reverse the specification of a cell type so that it returns to the state it was in during its development, where it had the potential to become any cell type. These reverse engineered cells are called induced pluripotent stem cells, or iPSCs. Scientists can then manipulate these induced pluripotent stem cells to differentiate into specific tissue types, used for transplantation (5). Scientists and doctors have successfully grown and transplanted bladders and windpipes (6). However, for organs like the liver, heart, and especially the kidneys, structural and cellular complexities pose challenges that are currently being tackled by scientists across the globe.
The gap between need and availability will only continue to grow. However, there are potentially suitable alternatives to not only close it, but to offer long-term solutions that would result in more patients in need receiving organs, and diminishing the discarding of organs from donors. Extending the criteria would likely help short-term, as it would allow more patients on the waitlist to receive organs at only slightly higher risk of low success. Long-term solutions like xenotransplants, or in vitro grown organs from induced pluripotent stem cells, while still far from being fix-all solutions, could be among the first steps taken to ensure that more and more patients receive the care they need.
References
Mella A, Calvetti R, Barreca A, Congiu G, Biancone L. Kidney transplants from elderly donors: what we have learned 20 years after the Crystal City consensus criteria meeting. J Nephrol. 2024 Mar 6;37(6):1449–61.
Bezjak M, Stresec I, Kocman B, Jadrijević S, Filipec Kanizaj T, Antonijević M, et al. Influence of donor age on liver transplantation outcomes: A multivariate analysis and comparative study. World J Gastrointest Surg. 2024 Feb 27;16(2):331–44.
Xenotransplantation. In: Oxford English Dictionary [Internet]. Available from: https://www.oxfordlearnersdictionaries.com/us/definition/english/xenotransplantation#:~:text=xenotransplantation-,noun,into%20humans%20for%20medical%20purposes
Hawthorne WJ, Thomas A, Pierson RN. Ethics and Theoretical Issues in Kidney Xenotransplantation. Semin Nephrol. 2022 Jul;42(4):151288.
Takebe T, Sekine K, Enomura M, Koike H, Kimura M, Ogaeri T, et al. Vascularized and functional human liver from an iPSC-derived organ bud transplant. Nature. 2013 Jul 25;499(7459):481–4.
Hunter P. One organ at a time: Research has been making much progress to create in vitro human tissues for transplantation but laboratory‐grown complex organs still remain decades away. EMBO Rep. 2014 Mar;15(3):227–30.
Health xchange.sd. Types of Organ Transplants. Available from: https://www.healthxchange.sg/men/heart-lungs/types-organ-transplants
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