A 57-year-old man from United States has become the first person in the world to receive a pig heart transplant. The intervention, carried out at the University of Maryland Medical Center, has been a success. However, it remains to be verified that the organ rejection.
Although the medical team that has performed the intervention is optimistic in this regard for two reasons. On the one hand, because the chosen pig comes from a herd genetically modified to remove the genes that would cause rejection. And, on the other hand, because to the normal cocktail of drugs another has been added whose objective is precisely to enhance that immunosuppression that prevents the body from attacking the new organ.
It is a giant step in the development of transplants of organs from other species, known as xenotransplantation. It is something that has been studied for centuries, but until now it had not been feasible, because medicine did not have sufficient advances to deal with it. Therefore, the success achieved so far is great news, which I hope will top a future list with many more.
From failure to success in pig heart transplantation
One of the first people to perform organ transplants from other animals was Serge Voronoff, who transplanted testicles from chimpanzee to several people in the 1920s.
Later, Come in 1963 and 1964, another doctor, the American Keith reemtsma, performed thirteen transplants of kidney of non-human primates. Most had a survival of several weeks; which, given the pioneering nature of the technique, were considered a success. One of the patients even lived nine months. And they could have been more, since the autopsy showed that the death had not been due to a rejection of the organ.
Regarding the heart transplants coming from other species, the first to make one was the doctor James Hardy, in 1964. The recipient was a dying patient for whom no human donor was found, and the donor a chimpanzee. Unfortunately, the primate heart could not support normal circulation in the human body and the patient died in a few hours.
Therefore, the first time that a heart transplant from a relatively successful non-human species was performed was in 1984. In her case the recipient was Stephanie Fae Beauclair, a baby born with a condition known as hypoplastic left heart syndrome. People born with this disease have the left side of their heart so underdeveloped that it cannot support systemic circulation. It is so serious that it can cause the ductus arteriosus to close and, with it, shock and death of the newborn.
The only solution is surgery and, in many cases, a heart transplant. Therefore, with this girl, the latter was chosen. However, in the absence of hearts compatible with her, the doctor’s team Leonard Bailey turned to one of baboon. The intervention initially seemed to go well, but for a short time, since the little girl died 20 days later due to the rejection of the organ.
The case, known as the transplantation of Baby fae, generated a great rejection towards xenotransplantation, despite being the one that had generated the longest survival. However, over time an intermediate procedure was passed, with the placement of pig heart valves. The next step was the transplantation of a whole pig heart. But it was necessary to do it well.
For this reason, over the years it has proceeded to develop genetically modified pigs to be able to transplant his heart to humans. In total they are modified 10 genes. To begin with, three genes of the pig are eliminated, responsible for the rapid recognition and rejection by the human immune system. On the other hand, six human genes are inserted, responsible for acceptance by this same system. And, finally, another gene in the pig is modified, in order to prevent excessive growth of heart tissue. Ultimately, the pig heart disguises itself as a human, so that it can survive to a transplant in our species.
Success in xenotransplantation
The patient who has just received this successful pig heart transplant is named David bennett. On December 31, when authorization was given for his intervention, he had been admitted for six weeks for a severe arrhythmia, which had forced him to be hooked up to a cardiopulmonary bypass machine, called extracorporeal membrane oxygenation (ECMO). This machine kept him alive; but, logically, the situation could not last forever. Unfortunately, her case was deemed unfit for a normal heart transplant. And his arrhythmia was not compatible with an artificial heart pump, either. It only seemed suitable for a xenotransplantation.
The medical team told him about the procedure and, above all, insisted on explaining the risks. Unlike Baby Fae, he is about a grown man, so he might have fewer negative ethical connotations. The patient, aware that he was your only option, accepted, so the whole team set out to prepare the xenotransplantation.
In addition to the genetically modified pig heart, they introduced a new drug, developed by the company Kiniksa Pharmaceuticals, which strongly suppresses the action of the immune system to prevent it from acting against the new organ.
Finally everything has gone well and, at least for the moment, it does not seem that there is rejection. Both the medical team and the patient are very proud of the result. Especially the latter, who in a release of the medical center stated that his only options were to die or undergo the intervention and that he wanted to live.
This operation has been a before and after, since the transplantation of organs from other species, such as pig hearts, may be the necessary solution to the high demand for organs. Even in Spain, where we have the largest number of organ donations in the world, these are insufficient for all patients who require them.
Having genetically modified animals for the use of their organs in xenotransplantation would be a great advance. But we will have to go step by step. For the moment, all hopes are pinned on this patient who is recovering in the University of Maryland Medical Center. He has already made history, being the first terminally ill person to receive a successful pig heart transplant. Now we have to wait and see if the organ remains with it without generating rejections. Hopefully all the great advances that science has made in these years will achieve it.