For the first time, a pig’s heart was transplanted into a 57-year-old man and started functioning. The surgery was performed on Friday at the University of Maryland Hospital in the US, thanks to a special authorization granted by the FDA. While aware of the risks, the patient – David Bennet – agreed to undergo the transplant, as it was a matter of life or death.
Right now, man should be disconnected from the heart-lung machine, which has supported and supported the new organ in recent days. In fact, according to doctors, headed by heart surgeon Bartley Griffith, the transplanted heart now appears to be able to work independently.
Against the shortage of organs. Technically, the surgery performed in the US is a xenograft. That is: a transplant on man of an organ taken from an animal. This procedure has been suggested many times in the past because it could help reduce organ shortage. However, enormous technical difficulties have hitherto prevented the development of a safe methodology, and the intervention performed in Maryland is also highly experimental.
Genetically modified. The main obstacle that doctors have found themselves having to solve is the powerful rejection reaction that the immune system can immediately produce against non-human tissues. “This reaction, known as hyperacute rejection, can irreparably damage the new organ and occurs as soon as it is connected to the patient’s vessels and is supplied with his blood” explains Marialuisa Lavitrano, professor of general pathology at the Bicocca University of Milan and expert of xenografts. “To avoid it, it is necessary to genetically modify the animal organ and use drugs that inhibit the immune system.”
Both solutions were adopted in the US case. The heart was prepared by the biotech company Revivicor, of Blacksburg (Virginia), which modified a dozen genes to eliminate hyperacute rejection. David Bennet is also given an experimental immunosuppressive drug. «At the moment the rejection seems controlled – Lavitrano continues -; but the reaction can also occur later and the patient will have to be monitored with great attention ».
The shape and size. The other problem relates to the size and function of the new heart. “The organs of the pig adapt to our body certainly better than those of animals that we consider more similar” continues the expert. “Monkeys, for example, have organs that are too small.” Still, even those from the pig aren’t perfect for us. Thus, an additional genetic modification was introduced into Bennet’s new heart to prevent it from growing once transplanted. In addition, doctors had to make minor changes to the shape during the surgery to fit the organ to the chest cavity.
Is this the future? “The first xenotransplantation of heart from pig to man represents a watershed in the history of transplants” explains Claudio Russo, director of cardiac surgery at the Niguarda Hospital in Milan. “In the past, another attempt was made with a baboon heart, which failed after 21 days due to a major rejection reaction, but it is the first time that an organ has been implanted that has been genetically modified to avoid this problem. Three days are few to talk about a success, but we are starting to see a future in which animal organs could actually help reduce waiting times for transplants ».
Today in Italy, patients who need a heart transplant remain on the waiting list for three years and seven months. “If xenotransplantation became a safe and consolidated intervention, we could intervene more promptly”, concludes Russo.