Reacción a "First pig-to-human liver transplant evaluated"

A frequent approach in the development of xenotransplants of different organs, before moving on to the clinical phase, is to perform them in patients in brain death but with haemodynamic stability, so that the evolution of the organ and the impact on the deceased person's body can be assessed, at least in the short term, but with maintained circulation.

In the United States, at least three kidney transplants have been carried out since 2021 —one with up to 61 days of follow-up in people in brain death— and another two heart transplants, which provided a wealth of useful lessons. In both cases, these preceded the first clinical experiences on living persons, which so far have resulted in two heart transplants (both deceased) and four kidney transplants, of which two patients are still alive after several months.

The team at the Military Hospital in Xi'an, China, has had extensive experience in experimental transplantation of all kinds of organs from pigs to monkeys for more than a decade. On this occasion it is the first case in the world of a transplant of a genetically modified pig liver to a human in a brain dead situation. The ultimate aim of the experiment was not to achieve a standard liver transplant, but rather to serve as a ‘bridge organ’ in cases of acute liver failure, while waiting for a human organ that could be used for the definitive transplant. The experiment lasted 10 days and the pig organ remained in good condition, with acceptable basic metabolic function and no signs of acute rejection, indicating that the procedure was satisfactory for the intended purposes and could be used in vivo in the near future.

In Spain, the team at the Virgen de la Arrixaca Hospital in Murcia has also had experience in transplanting pig livers into monkeys since the last century and is preparing a clinical trial, still pending the corresponding approvals, to transplant genetically modified pig livers from the University of Munich to three patients in acute liver failure. The procedure would be carried out on patients with a poor clinical prognosis and in those in whom the organ to be transplanted did not appear within two days, keeping the porcine organ until the patient stabilised and a suitable human liver became available.

The situation of acute liver failure, either due to toxins or an indication for retransplantation in the first days after surgery, occurred in Spain on 111 occasions during 2024, of which a suitable liver was not found in time in 8 cases (7.2%), out of a total of 1,344 transplants. The waiting time for emergency patients was less than 48 hours in 84% of cases and between two and four days in a further 10%. This means that the situation that this type of transplant is intended to treat is not a frequent one in our country, although it cannot be said to be exceptional either. It should be borne in mind that on average there are seven organ donations a day in Spain and a patient with acute liver failure has absolute national priority until a suitable liver is found for them. Needless to say, this is not the situation in most of the world, where having this therapeutic option for certain patients with a poor prognosis can be very useful if it is finally proven possible.

In short, this is an important experiment, which opens up a different path to the one tried so far for both vital organs (heart) and non-vital organs (kidney), such as the temporary replacement of the diseased liver until a human one is obtained for the definitive transplant.