Researchers Successfully Perform Pig-to-Human Heart Transplantation

New research in which doctors transplanted genetically modified pig hearts into people who were clinically dead could pave the way for human trials and a future with more organ transplants that can prolong lives, NBC News reported.

In the past month, researchers at NYU Langone Health transplanted pig hearts into two people who had recently suffered catastrophic heart failure and were left brain dead but remained on life support.

In both cases, the new hearts beat strongly and were not immediately rejected by the host bodies. The hearts continued to function well until the conclusion of the three-day experiment, doctors said.

“The heart was literally banging away. It was contracting completely normally,” Dr. Nader Moazami, a surgeon who was part of the transplant team, said of the moments after the heart restarted. “We learned a tremendous amount.”

Doctors at the University of Maryland last year implanted a pig heart into a living patient, but it failed after 49 days. The NYU research in subjects considered deceased is different because it allows researchers to rigorously test, refine treatments and collect detailed data without fear that experimentation will take a patient’s life.

The doctors hope that their research model — of testing pig organs in clinics with deceased patients — can help prepare the medical community for clinical trials and reduce the chances that living patients’ immune systems will turn on new organs. Nationwide, fewer organs are available for transplant than are needed by patients; pig organs could expand access to transplants and allow doctors to broaden who is eligible for such procedures.

“It’s all about going into the first living human trials with as much data as we can possibly have and make it as safe as possible — and effective,” said Dr. Robert Montgomery, the director of the NYU Langone Transplant Institute.

Doctors have long pursued new ways to meet the need for transplant organs.

In 2021, more than 116,000 people in the United States were accepted to waiting lists for an organ transplant, according to the national Organ Procurement and Transplantation Network.

The same year, 6,166 people died while waiting for their number to be called.

Over decades, doctors have inched closer to figuring out how to make animal organs suitable for people.

Researchers have focused recent efforts on pigs because their organs are similar in size to humans, and they have large litters and are easy to modify genetically, Montgomery said. Pigs are slaughtered by the millions for food in the US, which makes using their organs to sustain human life more palatable to the public than using primates, he added.

Before they are transplanted, pig hearts require genetic modification to reduce the risk of rejection and to ensure proper function. Researchers “knock out” — or silence — particular genes to prevent human antibodies from attacking the new organ when it is connected, Montgomery said. The researchers also prevent the expression of genes that would allow the heart to grow larger once inside the person receiving the transplant and exposed to human growth hormone. Researchers also “knock in” certain genes to perform some important human biological processes.

Without genetic modification, a patient’s heart rate would skyrocket and the organ would “turn black within a minute or two,” Montgomery said.

Transplant experiments from pigs to laboratory primates have been a key source of progress, Montgomery said. But primates are hard to care for, are prone to infection, and their bodies don’t always react the same as humans.