Skip to main content

Halal — The science behind the first successful pig-to-human heart transplant

Pig-to-Human Heart TransplantationIt may lead to a new approach to organ transplantation.

On january 7th, David Bennett became the first person to have a heart transplanted successfully into him from a pig. In press material issued three days after the operation, the University of Maryland confirmed Mr Bennett was doing well, and was capable of breathing on his own. While he continues to rely on artificial support to pump blood around his body, the team behind the surgery, led by Bartley Griffith, plan gradually to reduce its use.

This operation is a milestone for xenotransplantation—the transfer of organs from other species to human patients. It comes hot on the heels of another, in October, when a pig’s kidney was successfully attached for three days to a brain-dead patient in a hospital in New York. On that occasion, mere surgical success was the goal. But Dr Griffith’s team hope to save a life.

The operation itself received exceptional authorisation from America’s Food and Drug Administration under a provision which lets doctors use experimental treatments as a matter of last resort. Prior to it Mr Bennett was diagnosed with terminal heart disease, but was judged too ill to qualify for a human transplant. Having spent months in a hospital bed with no improvement to his condition, he gave his consent to the surgery.

The field’s recent flowering has long-established roots. For decades, researchers have attempted to tackle xenotransplantation’s fundamental problem. This is that the human body, when it recognises foreign tissue, has a tendency to turn against it. In the case of pigs, the most important marker of foreignness is a sugar molecule called galactose-alpha-1,3-galactose (alpha-Gal), which is found on the surfaces of their cells. While this molecule does not exist in humans, antibodies to suppress it do. Consequently, no transplant from a pig with alpha-Gal would last more than a couple of minutes in a human body.

In 2003 pigs were produced with a genome modified so as to suppress the enzyme responsible for making alpha-Gal. This was a step in the right direction, but other barriers popped up in its place. With each of these requiring years of work to overcome, many researchers—and much research funding—abandoned the field.

One collaboration which survived was that between the University of Maryland and Revivicor, a regenerative-medicine company in Blacksburg, Virginia. It was Revivicor that provided the genetically modified pig for Friday’s surgery. The animal in question had a genome modified in ten ways, to optimise the chances of success. Three genes had been removed to reduce the risk of a human antibody rejecting the donor organ. A fourth, a growth gene, had also been knocked out, to ensure the heart did not enlarge after transplantation. And six human genes had been added, to promote acceptance.

In addition to the usual risks surrounding any heart transplant, there are a number of areas of concern that Dr Griffith and his colleagues will be looking out for. One is any hitherto-unknown rejection mechanism. Another is the possibility that the organ may transfer porcine viruses to its new host. The pig in question was reared in a sterile environment to minimise the chance of that, but it remains a possibility.

Supporters of xenotransplantation think its potential to improve lives is huge. In America alone, over 100,000 people are waiting for transplants (though the vast majority need a kidney rather than a heart). In 2020 only a third of the required number of organs became available.

In theory, pigs can be bred to provide humans with any solid organ, though some will be more complex than others. A large part of the heart’s function is mechanical, but other organs have chemical jobs that will be harder to replicate. Moreover, even assuming these barriers can be overcome and successful surgical procedures developed, most researchers still acknowledge that scaling up xenotransplantation to meet the world’s demand for organs may take decades. After this news, however, the chances that it will happen eventually have increased. ■

The Economist
Saturday, January 15, 2022


• This article appeared in the Science & technology section of the print edition under the headline "Happy news"


• The official video—click here, from the University of Maryland (School of Medicine) and the original article—click here


• The video broadcasted by NBCclick here

Comments

Popular

Language & Religion — Does the Arabic language encourage radical Islam?

Native speakers of Arabic have long claimed that Arabic is far more than a language; rather, the language of Islam, the language chosen by God to speak to mankind, influences how a person perceives the world and expresses reality. This, in turn, has a profound impact on a society's outlook. Thus, Ahmed Taleb Ibrahimi, a former Algerian minister of education, declares that "a people that changes language is a people that changes its soul and its view on the world."1 Abdelkader Yefsah, a sociologist, recently wrote that use of the Arabic language "leads straight to... the primacy of the religious over all other activity."2 In contrast, nonspeakers of Arabic tend to be somewhat skeptical of such claims. They acknowledge the importance of Arabic and appreciate its profound connections to the Islamic faith, but find it hard to believe that Arabic is so consequential. While doing research at two Algerian universities in the academic year 1989-90, I had a unique oppor

Tropical diseases — A field test for malaria resistance

It will help to save lives, and may slow resistance’s spread. An arms race between pharmacologists and malaria parasites has been going on since the mid-19th century, when widespread use of quinine began. Few better illustrations of natural selection exist than the repeated emergence of resistance to such drugs. Even artemisinin, the most recent addition to the arsenal, has already provoked an evolutionary pushback. At the moment, working out which drugs, if any, a particular case of malaria is resistant to means sending a sample to a laboratory for a pcr test. But malaria is most often a problem in poor countries, where such laboratories are scarce, and so is money to pay for tests and to maintain the machines needed to conduct them. A better way for doctors and paramedics in the field to be able to tell, for a particular patient, which drugs the infection is resistant to would thus be welcome. And that may soon be possible, thanks to work by Ron Dzikowski and Eylon Yavin of the Hebre

Civil Disobedience (Henry D. Thoreau, 1849)

I heartily accept the motto, "That government is best which governs least"; and I should like to see it acted up to more rapidly and systematically. Carried out, it finally amounts to this, which also I believe- "That government is best which governs not at all"; and when men are prepared for it, that will be the kind of government which they will have. Government is at best but an expedient; but most governments are usually, and all governments are sometimes, inexpedient. The objections which have been brought against a standing army, and they are many and weighty, and deserve to prevail, may also at last be brought against a standing government. The standing army is only an arm of the standing government. The government itself, which is only the mode which the people have chosen to execute their will, is equally liable to be abused and perverted before the people can act through it. Witness the present Mexican war, the work of comparatively a few individuals using