A few days after the operation, the 57-year-old Maryland man is doing well, although it is still too early to say that he has been 100% successful.
David Bennett, 57, from Maryland (USA) has become the first human to receive a heart from a genetically modified pig. It was reported by BBC citing surgeons from the University of Maryland Medical Center, which conducted the pioneering surgery on 7 January.
The patient suffered from an incurable heart disease, was already walking around with a transplanted valve and the transplant was the only option. As Bennett could not receive a heart from a human donor or replace it with an artificial one, another route had to be found. At the very end of 2021, the United States Food and Drug Administration issued an emergency authorisation for the operation - the world's first human pig heart transplant. The procedure lasted nearly eight hours.
Bennett is now feeling well, and the first 48 hours, which are considered critical, went without incident, said Dr Bartley Griffith, who oversaw the process. The man is still hooked up to a heart-lung machine, which kept him alive even before the operation, but that, doctors said, was normal for the recipient. Bennett may be disconnected from the machine today: the new heart is functioning and doing most of its work.
Among other things, doctors are watching to make sure that the patient does not develop symptoms of porcine endogenous retrovirus (PERV, Porcine Endogenous Retrovirus) - the risk of transmission is present but considered low. PERV is a C-type retrovirus, i.e. oncogenic; it is incorporated in the pig genome and is transmitted vertically by inheritance. Endogenous retroviruses are 'remnants' of ancient viral infections in pigs and other mammalian species. They are not normally infectious in host species but can become so in recipient species. The first case of PERV infecting human cells in vitro was recorded in 1997.
Despite the risks, Bennett is serious. "It's either die or have a transplant," he said before the operation. - I want to live, this is my last choice.
Xenotransplantation, or cross-species transplantation - the transfer of organs, tissues or cell organoids from one species to another - has a long history, with attempts to use animal blood and skin dating back hundreds of years. In the 1960s, chimpanzee kidneys were transplanted into several humans, but at best the recipient managed to survive nine months. In 1984, Leonard Bailey at Loma Linda University Medical Center in California performed a baboon heart transplant on a baby girl named Baby Faye, who was born with left heart hypoplasia syndrome. Alas, the girl suffered rejection and died 20 days later due to renal failure.
Pig organs are thought to be easier to grow (compared to primates), and reach the size of adult human organs within six months. For this reason heart valves from these animals are now being transplanted into humans, and in some cases diabetics are receiving cells from their pancreas. In the case of pig skin, it has also been used as a temporary transplant for burn patients.
This has the advantage that the risk of rejection in humans is lower for these genetically modified pigs. University of Maryland researchers have transplanted pig hearts into primates during trials, but until recently, operations involving human recipients were feared.