In a striking advance that helps open the door to organ transplants from animals, researchers have created gene-edited piglets cleansed of viruses that might cause disease in humans.

The experiments, reported on Thursday in the journal Science, may make it possible one day to transplant livers, hearts and other organs from pigs into humans, a hope that experts had all but given up.

If pig organs were shown to be safe and effective, “they could be a real game changer,” said Dr. David Klassen, chief medical officer at the United Network for Organ Sharing, a private, nonprofit organization that manages the nation’s transplant system.

There were 33,600 organ transplants last year, and 116,800 patients on waiting lists, according to Dr. Klassen, who was not involved in the new study. “There’s a big gap between organ supply and organ demand,” he said.