Surgeons performed an eight-hour procedure to transplant a genetically modified pig’s heart into a human on Jan. 7.
Credit: University of Maryland School of Medicine

For the first time ever, surgeons at the University of Maryland Medical Center successfully transplanted a heart from a genetically modified pig to a human. The eight-hour surgery took place on Jan. 7, 2022, in Baltimore, Maryland. The recipient was a 57-year-old man with heart disease, called arrhythmia. He was deemed too sick to receive a human heart. Scientists had altered the genes of the pig to make it more similar to humans, removing four pig genes and adding six human genes through genetic engineering.

More than 107,000 people are on waiting lists to receive organ donations in the United States. Transplanted tissues and organs replace diseased, damaged, or destroyed body parts. They can help restore the health of a person who might otherwise die or be seriously disabled. Commonly transplanted organs include the heart, lungs, kidney, and liver.

Because of the shortage of human organs, researchers are actively investigating the use of donor organs from animals. Transplanting organs from one species to another is called xenotransplantation. Use of pigs as organ donors is an especially active area of research. Pigs are already widely raised for food and leather, and their organs are about the same size as adult human organs. One major concern is preventing accidental transfer of viruses from other animals to people. Another challenge is preventing the recipient’s immune system from destroying a donor organ. If the immune system recognizes that a transplanted organ came from outside the body, the system attacks the organ as a dangerous invader. This reaction is called rejection. Doctors try to prevent rejection by choosing the best donor and prescribing immunosuppressive drugs, which are special medications to protect the transplant.

Xenotransplantation has been studied for over 60 years but is not authorized in the United States. The process of raising genetically modified animals to harvest their organs is widely debated. The Food and Drug Administration gave the surgery team an emergency authorization on Dec. 31, 2021, to conduct the transplant due to the recipient’s condition.

From the long list of people waiting to receive a lifesaving organ, 17 people die each day. This groundbreaking surgery is giving hope to many patients and their family members who are waiting on organs. However, many surgeons and experts believe it is too early to call this xenotransplantation a success.

December 1, 2017

South African surgeon Christiaan Barnard electrified the world 50 years ago on Dec. 3, 1967, by performing the first successful human heart transplant. On that day, Barnard removed the dying heart of Louis Washkansky and replaced it with a healthy one taken from an accident victim. The operation took place at Groote Schuur Hospital in Cape Town, South Africa. Barnard’s surgical skill and daring—combined with his telegenic looks and ready wit—catapulted him overnight into the role of international celebrity. Newspapers and television interviewers scrambled to hear his expert opinion on most everything from health and physical fitness to science to global politics.

The South African surgeon Christiaan Barnard, seen at the center of this photo among his surgical team, performs open heart surgery in Cape Town in 1967. Later that year, Barnard performed the first human heart transplant operation. Credit: © Corbis/Bettmann

Prior to Barnard’s accomplishment, surgeons in Europe and the United States—including pioneering American heart surgeon Norman Shumway—had experimented with several techniques to perform a human heart transplant but had met with little success. In 1967, Barnard was presented with a unique scientific opportunity. Denise Darvall, a 25-year-old office clerk, was unfortunately struck by an automobile in Cape Town. She was rushed to Groote Schuur Hospital, where her brain was found to be clinically dead. However, her still-beating heart was in good condition, and she had the same blood type as Washkansky, an ailing 54-year-old Lithuanian-born grocer. The successful operation took about six hours to complete.

Organ transplant surgery is difficult for even the most skilled surgeons and is prone to complications. The first truly successful human organ transplant operation was done in 1954, when doctors in Boston transplanted a kidney from one person to his identical twin. Because the donor and recipient were genetically identical, there was no danger the transplanted organ would be attacked by the recipient’s immune system. Doctors refer to this complication as organ rejection. The risk of rejection affecting a vital organ such as the heart posed a daunting challenge for surgeons. Washkansky was vulnerable to infection from the large doses of drugs and radiation used to suppress his immune system and prevent organ rejection. He died of pneumonia 18 days after the operation, but his heart functioned normally until his death.

In the United States and Europe, the prospect of heart transplant operations also raised many ethical, moral, and legal considerations. Because the donor’s heart must be transplanted immediately, the problem of determining the exact moment of death was debated by physicians and lawyers. In the United States, death was normally defined as when a person’s heart stopped. Law enforcement officials threatened to arrest surgeons who took organs from brain-dead individuals while the heart remained beating. The delay often led to tissue damage and decreased the chances of a successful transplant operation. Barnard’s success with a brain-dead victim as a heart donor made the practice more acceptable for future organ transplants worldwide.

A month later, on Jan. 2, 1968, Barnard caused a new sensation in racially segregated South Africa by transplanting the heart of a young man of mixed race into a white man. The recipient survived for 19 months and 15 days, in part because Barnard’s team had reduced the amount of antirejection drugs the patient received. Over the years, surgical techniques have been improved and new antirejection drugs have been developed. Today, about 3,000 human heart transplant operations are performed each year in the United States, and about 5,000 are performed annually worldwide.