A genetically modified pig lung was transplanted into a brain-dead man and functioned for nine days, according to a newly published report.
There has been some recent success transplanting pig kidneys and hearts into people, but this is believed to be the first attempt to transplant a pig lung into a human. Doctors hope this could someday be an options for people in need of organs, but experts say it won’t be any time soon.
Authors from Guangzhou Medical University First Affiliated Hospital in Ching didn’t identify the patient in the study, but he’s described as a 39-year-old man who was declared brain-dead after a brain hemorrhage. Doctors transplanted a pig lung into his body after getting consent from the man’s family. The findings were published Monday in the journal Nature Medicine.
With any human-to-human transplant or animal-to-human transplant – also known as xenotransplantation – doctors watch carefully for infection and rejection.
The patient received several medications to reduce the risk of infection and rejection. The lung itself had also received six gene edits, and the donor pig was kept in an extremely clean and strictly controlled area for its entire life.
In the study, the researchers reported that they didn’t see immediate signs of rejection after the transplant but problems arose after just a day.
Widespread swelling developed throughout the man’s body as fluid built up in his tissues, potentially due to a blood flow problem. In addition to helping a person breathe, the lungs play a role in blood circulation.
There were some signs of partial recovery just days after the transplant, but despite all the precautions, doctors saw signs that the man’s body was starting to reject the organ.
At the request of the man’s family, doctors terminated the experiment.
“Although this study demonstrates the feasibility of pig-to-human lung xenotransplantation, substantial challenges relating to organ rejection and infection remain,” the researchers wrote in the new study. They concluded that more research is needed before the procedure could be done again repeated in a clinical trial.
The world has a tremendous need for donated organs. In the US alone in 2023 the waiting list for all organ transplants was twice as long as the number completed.
Last year, there were more than 48,000 transplants in the US, but more than 103,000 people were on waiting lists. About 13 people in the United States die every day waiting for a transplant, according to the federal Health Resources and Services Administration, or HRSA.
Pig valves have been transplanted into humans for the past 30 years; organs are trickier, but doctors have seen limited success with genetically modified pig hearts and pig kidneys. They’ve also experimented with a genetically modified pig liver but had less success, at least so far.
The most success to date has been with a man in Massachusetts, Tim Andrews, who is living with a genetically modified pig kidney that was transplanted at Massachusetts General Hospital in January.
Experts say there’s a ways to go before pig lung transplants show as much success.
“Nobody would sign up for a nine-day lung transplant,” said Dr. Adam Griesemer, a transplant surgeon a senior member of the xenotransplantation team for NYU Langone’s Transplant Institute, who was not involved with the new research.
Griesemer said transplants of pig lungs into other animal in past experiments have shown similar results.
“I think it is very important to do these studies since you can’t assume that the animal models are going to perfectly reflect what happens in human recipients,” Griesemer said.
The researchers in China said they did the study, in part, because there is “transformative potential” in xenotransplantation.
Dr. Ankit Bharat, chief of thoracic surgery and director of the Northwestern Medicine Canning Thoracic Institute, found the research interesting but added that he thinks pig-to-human lung transplants won’t be happening any time soon.
“We’ll learn something from this, but I’m not fully convinced that this really opens up the doors to doing bigger trials, just based on what we observed here,” he said.
Lungs are much more complicated to transplant than organs like kidneys, he said.
The lungs play a critical role in blood filtration, temperature regulation, platelet production, pH balance and immune defense, and they have metabolic and endocrine functions. And unlike the kidney or heart, the lungs are exposed to outside elements like viruses and bacteria when they take in air.
Because they are so large and covered with proteins that aid in immune defense, even with a lung transplant from another human, it’s difficult to circumvent the body’s instinct to reject something foreign, Bharat said.
“That’s a tough problem to solve. We haven’t really solved that, even in human organs,” he said. “So you are just adding another layer of complexity with pig antigens that can become another problem.”
Although the researchers behind the new study suggested that the man’s body did not show signs of immediate rejection of the pig lung, but Bharat isn’t so sure after he looked at the X-ray images and CT images they shared.
“There is a lot of damage,” Bharat said. “I don’t know if I’m fully convinced that there was no hyper-acute rejection.”
At least where lung transplants are concerned, Bharat thinks, advances in the use of a human’s own stem cells may be more promising than transplanting a pig organ.
Griesemer said there is also research under way to use a pig lung as a scaffold so scientists using stem cell therapy can swap out the pig cells for human cells.
“In a sense, that would not really be a xenotransplant, because the cells would be human, but the structure would be from a pig,” Griesemer said. “So that’s another possibility for how medical technology might solve this problem for people that need lung transplant.”
Recent advances in cloning and gene editing, along with a better understanding of infection control, have led a handful of institutions to breakthroughs transplanting other pig organs — all key steps that could one day lead to an alternative organ supply.
