A recent succession of three news items has illustrated the good momentum in organ transplantation science: first, in October, the transplantation of a pig kidney to a brain-dead person; then, this same month, the apparently successful transplantation of a pig heart to a man in a clinical setting; and, now, the transplantation of two pig kidneys to another brain-dead person.

These milestones seem to demonstrate that xenotransplantation, or the technique of transplanting organs from other animal species into humans, is finally a reality, after years of research. However, these achievements need to be put in context.

These facts can be considered a true revolution and a milestone in medical progress, especially in transplantation, and obviously bring us closer to the clinical reality of xenotransplantation in humans after decades of research in this field.

It is important to say that there is still a long way to go: we will have to see if these procedures are reproducible; we will have to carry out properly designed clinical trials to check the efficacy and safety of this type of transplantation not only in the short term but also in the medium and long term; and if they prove to be effective and safe, we will have to study how to incorporate this type of transplantation into healthcare schemes in such a way that they are sustainable, maintainable over time and accessible to all patients who might need them.

In short, it is important that people do not believe that this will be available tomorrow.

This is not the first time that xenotransplantation has been attempted, with some success, in humans. The best known case was Baby Fae, a baby in 1984 who received a baboon heart and lived 21 days.

But with these three procedures, particularly with the case of the heart in which there is a therapeutic purpose, a qualitative leap has been made: genetic modification carried out in pigs. A genetic modification that aims to reduce the risk of acute rejection of this organ.
To this end, genes expressing certain proteins to which the human body reacts very abruptly because it does not possess these antigens have been eliminated, and some other genes have been modified and human genes introduced which reduce the risk of acute rejection. In addition, some genetic modifications have been made so that the transplanted organ, particularly in the case of the heart, does not continue to grow indefinitely.

The potential is immense. Around 150,000 organ transplants are performed worldwide every year, and the WHO estimates that this only covers 10% of global transplant needs. Therefore, if xenotransplantation is possible, we are talking about hope for the thousands of patients who in the future will need the replacement of a diseased organ with a healthy one.

At the moment, xenotransplantation seems to be taking the lead over other alternatives on the table, such as the construction of bioartificial organs. It now appears that xenotransplantation may become a near reality.

Thus, it seems that it is still necessary to look to the future. What needs to be done now is to design studies that really allow us to test the efficacy and safety of these transplants in the medium and long term.

Also, we will have to pay attention to the regulatory aspects, paying attention to the ethical aspects that may arise from the perspective of the use of animals or from the perspective of which patients could be candidates to participate in this type of study or be recipients of xenotransplantation.


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