Surgeons complete first successful transplant from genetically modified pig heart
On January 7th, 2022, surgeons from the University of Maryland School of Medicine (UMSM) successfully performed the first xenotransplantation using a genetically modified pig heart.
According to the Health Resources and Services Administration, there are currently over 100,000 patients awaiting an organ transplant, with 17 patients dying each day.
The ongoing organ shortage poses an issue for both patients and healthcare providers.
“There are simply not enough donor human hearts available to meet the long list of potential recipients," said Dr. Bartley P. Griffith, the lead cardiothoracic surgeon behind the transplant.
The patient, David Bennett, suffered from end-stage heart failure and was initially deemed ineligible for a human heart transplant due to terminal heart failure and an uncontrollable irregular heartbeat.
With no other treatment options, Bennett resorted to participating in an emergency FDA-authorized transplant with the genetically modified pig heart.
"This is the culmination of years of highly complicated research to hone this technique in animals with survival times that have reached beyond nine months," said Dr. Muhammad Mohiuddin, a professor of surgery at UMSM.
Because of the genetic similarities between monkeys and humans, nonhuman primates (NHP) have been investigated as prospective xenotransplant donors since the 1920s.
However, research on NHP transplants was put on hold due to ethical concerns and breeding complications. As a result, pigs are now thought to be the best xenotransplantation candidate because they have organs similar in size and function to humans and can be efficiently bred to high health standards.
A common obstacle associated with organ transplants, especially when transplanting organs from animals, is organ rejection.
Organ rejection happens when the antigens on the cells of transplanted organs are not recognized by the recipients’ immune system leading to reduced organ function or complete failure.
Minor genetic differences between pigs and humans can lead to a high chance of the patient’s immune system launching an aggressive attack on the foreign organ.
To prevent Bennett’s body from rejecting the pig heart, genetic engineers removed three pig genes that trigger attacks from the human immune system and added six human genes that help the body to accept the organ.
“We’re feeling progressively confident that we are ahead of issues with respect to heart rejection,” Griffith said.
Despite the recent success, medical professionals still recognize the ethical and technical hurdles with nonhuman transplants.
Megan Sykes, a surgeon and immunologist at Columbia University, said there’s more scientific information needed in assessing each genetic modification to prevent potential harmful effects in humans.
"We are proceeding cautiously, but we are also optimistic that this first-in-the-world surgery will provide an important new option for patients in the future,” Griffith said.
