Dusseldorf A genetically modified pig heart is said to be his last resort: “Either I die or I do this transplant,” said the American David Bennett before his operation in which the new heart was transplanted. “I want to live. I know it’s a shot in the dark, but it’s my last choice ”.
The operation was successful at the weekend. According to their own information, a team of doctors in Baltimore has for the first time inserted a modified pig heart into a person and connected it to their organism. The procedure at the University of Maryland Medical Center took eight hours.
Doctors see a turning point for transplant medicine – but at the same time warn against exaggerated expectations.
The 57-year-old Bennett suffered so badly from a life-threatening heart disease that a human donor heart was no longer an option for medical reasons. He consented to the pig heart transplant. According to the doctors, he is fine: “It creates the pulse, it creates the pressure, it’s his heart,” said Bartley Griffith, director of the clinic’s heart transplant program.
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However, the patient’s condition can change at any time. Because such an operation has not yet been carried out, the doctors do not dare to make a prognosis. But if Bennett could go on living with the new heart, it would be a sensation – and a hope for thousands of people in need of a new organ.
Human donor organs are and will remain scarce. In Germany alone, almost 10,000 patients are currently waiting for the chance of such an operation. But with 10.7 donors per million people, the rate in Germany is the second lowest in Europe. With the exception of Luxembourg, nowhere else do patients have to wait so long for a life-saving organ.
“The situation is disastrous – and it was like that even before the corona pandemic,” says Bonn doctor Christian Strassburg, President of the German Transplantation Society.
Artificial hearts are not very efficient
But can animal organs really be a substitute? Doctors in Maryland are thrilled that the pig heart has been accepted into Bennett’s body. “This organ transplant shows for the first time that a genetically modified animal heart can function like a human heart without the body rejecting it immediately,” said the University of Maryland Medical Center
For decades, researchers have been working on the successful transfer of animal organs to humans. In previous attempts, however, the patients only survived the procedure for a few days. Chimpanzee kidneys were transplanted in the 1960s, but the recipients only lived a few months. A baby who had a baboon heart only survived 20 days in 1983.
At the same time, doctors have been working on artificial hearts since the early 1970s. But to this day, these are only considered a temporary solution until patients receive a donor organ. Artificial hearts are risky and still not as efficient as the natural organ.
But a lot has happened in recent years in the search for natural replacements – thanks in part to new methods for changing genes. In principle, pigs in particular are particularly well suited as organ donors for humans: individual heart valves in animals are already being used in humans, and individual cells are transferred to patients in the event of diseases of the pancreas, for example.
The organs of animals are similar to those of humans.
(Photo: dpa)
The heart of a six-month-old pig resembles that of an adult human. The likelihood that it will not be rejected after the transplant is therefore high. The chances increase further when the pig organs are genetically modified and thus adapted to the human body.
David Bennett’s new pig heart was genetically modified in ten places before the procedure, according to the University of Maryland. This was implemented by scientists from the US biotech company Revivicor, a specialist in the so-called xenotransplantation technology.
Doctors switch off certain genes
They use the new kind of gene editing, with which certain sections of the genetic material can be switched off or renewed. Four genes that produce a certain molecule have been paralyzed in the pig’s heart. Doctors suspect that this molecule causes a rejection reaction in the human body.
In addition, another gene was inactivated to stop the growth process of the pig heart after the transplant, as the surgeon involved, Muhammad Mohiuddin of the “New York Times” (NYT) explained. Six human genes were built into the pig’s genetic makeup. They are supposed to make the organ more tolerable for the human immune system.
In the fall of 2021, doctors in New York used a genetically modified pig kidney on a person. The organ had been connected to the circulatory system of a brain-dead person outside of the body for two days.
A choice between life and death.
(Photo: imago images / ZUMA Wire)
But with the now successfully transplanted pig heart, medicine is entering a new dimension. “This is a turning point,” says medical scientist David Klassen of the NYT’s US organ donation network Unos. “Doors are opening that will lead to major changes in the treatment of organ failure.”
But there are still unanswered questions before such a technology can be widely used – above all, how long can Bennett live with the pig’s heart, how his state of health is developing, and how long-lived the genetically modified organ itself is.
In addition: The transplant could only be carried out on the basis of a one-time emergency approval from the health authority FDA. On the basis of medical urgency, she decided to forego the otherwise necessary clinical studies for such treatments. This also applies to the drugs specially developed by the University of Maryland to accompany the procedure.
The German Transplantation Society assumes that, despite all the successes, a few years will pass before xenotransplantation is reliably researched and can be used in everyday clinical practice.
Thus, the successful installation of a pig’s heart remains an experiment with an uncertain outcome for the time being. Patient Bennett said he was happy after the operation. For him it was a choice between life and death.
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