LONDON -- For the first time on record, a lung from a genetically modified pig has been successfully transplanted into a human body, Chinese scientists announced in a study published in Nature.

"Lungs are complex organs to transplant, but the surgery is a step towards clinical trials," Nature reported Tuesday.

The recipient, a 39-year-old man in China who was brain dead, received the lung that had undergone six genetic modifications to improve compatibility with humans. The organ remained viable and functioning for nine days in his body with no signs of hyperacute rejection or infection.

He Jianxing, corresponding author of the study, told Xinhua that with growing global demand for organ transplants, xenotransplantation is considered a promising solution to the shortage of donors. He said the achievement marked a vital step forward in lung xenotransplantation.

"This study marks a milestone in translational medicine," said Beatriz Dominguez-Gil, director of the National Transplant Organisation.

At least half a dozen people in China and the United States have so far received genome-edited pig organs, including hearts, kidneys, livers, and a thymus.

Dominguez-Gil highlighted the significance of the breakthrough, noting that lungs are especially difficult to transplant due to their delicate physiological balance. They receive a very high blood flow and are constantly exposed to ambient air, making them particularly vulnerable.

"Lungs are the most difficult organ to transplant," said Muhammad Mohiuddin, a surgeon and researcher at the University of Maryland School of Medicine in Baltimore, who in 2022 led the first pig-heart transplant into a living person.

"I applaud their effort," he was quoted by Nature as saying. "It's a first step" toward lung xenotransplantation - the use of animal organs in humans.