Genetically modified pig hearts have been successfully transplanted into two brain-dead patients by surgeons at New York University (NYU), a feat that hopes to help address the shortage of donor organs desperately needed in the US and beyond.

A team from NYU Langone Health performed xenotransplants on Thursday June 16, 2022, and Wednesday July 6, 2022. 

The pigs’ hearts had been tweaked with 10 genetic modifications – four to block pig genes and six added human genes – that helped to prevent rejection, reduce abnormal organ growth, and promote the expression of proteins that regulate important biologic pathways. After hours of surgery, the researchers then monitored the patients’ heart function for three days.

The operations were declared a success for a couple of reasons. Firstly, the hearts appeared to function healthily and showed no signs of rejection – a potential problem for even the most simple of transplants. Secondly, their tests showed the body had not become infected with a pig virus called porcine cytomegalovirus (pCMV).

Earlier this year, history was made when David Bennet became the first human ever to receive a pig heart transplant. Unfortunately, the 57-year-old patient with terminal heart disease died just two months later and it was later revealed that the transplanted organ contained pCMV. It's unclear how much the virus had to do with his death, but it’s clearly an issue that the researchers are keen to iron out.

"Other studies have shown that pCMV may be a factor in the success of xenotransplanted organs," Robert Montgomery, Professor and chair of the Department of Surgery at NYU Grossman School of Medicine and director of the NYU Langone Transplant Institute, said in a statement. "More sensitive screening methods have been introduced to detect low-level traces of pCMV in the donor pigs.”

Scientific hurdles aside, xenotransplants raise a bunch of ethical conundrums, and many members of the public – especially some animal rights groups – are hostile to the idea. 

However, it’s a prospect that could save lives. There are currently over 106,000 people on the national transplant waiting list. Almost 106,000 people in the US alone are currently on the waiting list for a lifesaving organ transplant and an average of 17 people die each day from the lack of available organs for transplant. This is a problem that could be significantly eased through xenotransplants. 

"Our greater purpose is to address the organ shortage and provide another option for the more than 100,000 people nationwide waiting on that lifesaving gift," added Montgomery