Doctors from the University of Maryland transplanted a genetically modified pig’s heart into a dying man with severe arrhythmia. In order to reduce the organ’s immunogenicity, doctors edited ten genes in the animal.
Three days after the transplant, the heart was functioning well and there were no signs of rejection. Despite this, it is too early to talk about the success of the operation – the patient will have a long observation period.
Subtleties of organ transplantation
Transplanting organs from one person to another is not easy due to the fact that people are not always immunologically compatible. In order to find a suitable donor, doctors sometimes have to wait for months. The situation is even more complicated with animal organs, although theoretically transplanting them to humans could save many patients who do not wait for their turn for transplantation.
To increase the chance of donor organs taking root, scientists are trying to modify their tissues and make them less immunogenic. For example, the alpha-galactose carbohydrate, which is unusual for the human immune system, is removed from the cell surface. The FDA has approved such a line for therapeutic use in 2020.
In October 2021, doctors from New York transplanted a pig kidney modified in this way into a woman connected to life support devices – she was diagnosed with brain death. Doctors monitored her for three days and found no signs of rejection of the transplanted organ.
First transplantation of a pig’s heart into a man
Doctors at the University of Maryland clinic went even further from the pig kidney operation and transplanted a pig’s heart into a man with terminal heart disease. Doctors used a pig in which not only the genes encoding immunogenic molecules were disabled, but also six genes that are responsible for immune tolerance were introduced into the genome. In addition, a gene was blocked in the animal that could provoke an overgrowth of cardiac tissue. In total, doctors edited ten genes.
The patient, who became a recipient for a pig’s heart, was declared unfit for receiving a donor organ from a person (the doctors do not report the reasons for this), so participation in an experimental operation was his last chance for life. Six weeks before the transplant, he was admitted to the hospital with life-threatening arrhythmias and was hooked up to a machine that supplies oxygen to his blood.
How successful was the operation?
The experimental operation took seven hours and was completed successfully. Three days after the transplant, the man was feeling well, the new heart was pumping blood, and the doctors did not notice signs of transplant rejection. Nevertheless, it is still impossible to say with confidence that this final success is still not possible: there will be a long period of observation of the patient, who is now taking medications to prevent heart rejection.
Several teams of scientists around the world are trying to develop genetically modified pigs whose organs would be compatible with the human body. Recently, we talked about American and Chinese researchers who set as their goal not only to make animal tissues less immunogenic but also to rid them of retroviruses that can infect the recipient’s body.
* See the official website of the University of Maryland or this video below for footage and full details from the surgery.
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Sources:
• The Guardian. (2022, January 10). Maryland doctors transplant pig’s heart into human patient in medical first.
• Kotz, D. (n.d.). University of Maryland School of Medicine Faculty Scientists and clinicians perform historic first successful transplant of porcine heart into adult human with end-stage heart disease.
• Rabin, R. C. (2022, January 10). In a first, man receives a heart from a genetically altered pig. The New York Times.
• ScienceDaily. (2022, January 10). Successful transplant of porcine heart into adult human with end-stage heart disease.
