What is the future of xenotransplantation after first pig heart transplant patient dies?

The death of David Bennett, the first person to be given a pig’s heart transplant, is likely to fuel renewed debate about the use of animal body parts in humans.

Mr Bennett lived for two months following the transplant, during which time doctors hoped they had achieved the holy grail of xenotransplantation.

The surgeons at the University of Maryland Medical Center in the US have not given an exact cause of death, saying only that Mr Bennett’s condition had begun deteriorating several days earlier.

It is not yet clear whether the heart failed, and if so, why, but his death raises the question of how effective animal-to-human transplants are.

Doctors have long dreamed of using animals to provide organs and tissue in people suffering devastating and incurable diseases. After all, they have four limbs, a central nervous system and blood and organs just like ours.

But success in carrying out such surgery has proven elusive over decades of experimenting – and instead has given rise to a series of ethical, scientific and moral dilemmas.

In the 1960s, several transplant operations were attempted using kidneys from chimpanzees, but only one patient survived for any length of time - nine months.

When the first primate-to-human heart transplant took place - at the University of Mississippi in 1964 - the patient died within two hours.

The best known xenotransplant of the past century was in Baby Fae, a girl born in 1984 with a lethal heart defect who was given a baboon’s heart. She lived for just three weeks.

In 1997, two Indian surgeons attempted a pig heart and lung transplant on a 32-year-old patient. He died from an infection, and the surgeons were jailed.

But in 2017 scientists claimed a breakthrough, announcing they had cleared a major barrier to transplanting organs from pigs into humans by removing threatening viruses from the animals’ DNA.

Advances in technology since then allowed the Maryland team to attempt the last-hope operation on Mr Bennett, who was ineligible for a human heart.

Widely hailed as “groundbreaking” and “a breakthrough”, the pioneering operation used a the heart of a pig that had been genetically modified to remove genes that would have triggered it to be quickly rejected by the body and to add human genes to help it accept the organ.

However, Mr Bennett’s death will do nothing to quell the controversy surrounding the procedure.

Doctors who support xenotransplantation point out that around 7,000 people are on the UK transplant waiting list and at least one person dies every day while waiting for a match.

In the US, an average of 20 people die each day waiting for one to become available.

Bartley P. Griffith, who carried out the transplant, said before the operation:“This was a breakthrough surgery and brings us one step closer to solving the organ shortage crisis. There are simply not enough donor human hearts available to meet the long list of potential recipients.”

Using animal organs is a “potentially life-saving option for people with such ailments as severe heart disease and kidney failure”, according to academic Ololade Olakanmi.

In Philosophy Now, Olakanmi writes: “If properly developed, xenotransplantation has the potential to one day not only ameliorate the present organ donor shortage, but also to help address the ravages of Parkinson’s disease, childhood-onset diabetes, Huntington’s disease, and a number of other conditions.”

Pig organs are considered suitable for xenotransplantation because they are similar to human organs in size and function, and can be bred in large numbers.

Jayme Locke of the University of Alabama at Birmingham, where a pig kidney was transplanted into a brain-dead patient, suggested pig organs would advance the entire field: “What a wonderful day it will be when I can walk into clinic and know I have a kidney for everyone,” she told the New York Times.

But sceptics warn of the importance of looking at the bigger picture – that is, the risk of spreading disease, the ethics of patient consent and animal suffering involved.

Human viruses suspected to have originated in animals include human immunodeficiency virus, simian immunodeficiency virus and bovine spongiform encephalopathy (BSE), in which people developed Creutzfeldt-Jakob Disease.

As far back as 1999, Emanuel Goldman, a professor at New Jersey Medical School, Newark, USA, warned that xenotransplantation was a “very seductive, but inherently dangerous idea” because introducing viruses unique to animals into people could threaten humankind.

“The entire human population on this planet is put at risk by this kind of procedure,” he wrote in the BMJ.

“Viruses that inhabit animals, some of which are even intrinsic to the animal’s own genetic material, will gain a route of entry into the human population which is not ordinarily available to them.”

“There’s never going to be enough,” Donna McCormack, principal investigator of Transplant Imaginaries, a project on embodied ethics told Wired, “because they will keep changing the parameters as to who can get them, how unwell you can be, under what circumstances.”

Michael J. Reiss of University College London, has highlighted how shortly before birth, a pig’s entire uterus containing piglets would be removed. The piglets would then be raised in isolation and in sterile conditions.

He points out that many hundreds, possibly thousands, of primates have already been used in surgical operations and “every such operation leads to considerable pain and a dramatic shortening of lifespan”.

People for the Ethical Treatment of Animals (Peta) condemned Mr Bennett’s pig heart transplant as "unethical, dangerous, and a tremendous waste of resources".

"Animals aren’t tool-sheds to be raided but complex, intelligent beings," the organisation said.

Other opponents of xenotransplantation worry about whether a sick patient can truly give informed consent.

Laura Purdy, also writing in Philosophy Now, said: “When people are very ill, pain or fear may prevent them from reasoning well about their alternatives. This problem is compounded by reservations health care providers may have in fully disclosing the risks inherent in the kind of last-ditch treatments available.”

If Mr Bennett’s cause of death does turn out to be a direct result of the heart transplant, scientists may feel they are back to square one, and still nobody will be able to say the argument has been won.