The organs are almost the same size and function similarly enough to human organs that scientists think it could work.
Experiments mixing human and pig cells together showed those viruses could escape to infect human tissues.
Prof Ian McConnell, from the University of Cambridge, said: "This work provides a promising first step in the development of genetic strategies for creating strains of pigs where the risk of transmission of retroviruses has been eliminated".
Dr. George Church, a geneticist at Harvard who led this new study said that transplants from pigs to humans can become a reality in two years. As reported in Science, the group used CRISPR to disable viral DNA lodged in the pig genome and then grew healthy piglets from the edited cells.
Researchers at Harvard University and a private company used the precision gene editing tool Crispr-Cas9 combined with gene fix technology to deactivate 100 percent of the virus in a line of pig cells.
In April it was announced that a British farm will supply pigs' gullets to treat children at Great Ormond Street Hospital born without a section of their oesophagus.
Whether or not pig retroviruses would truly pose a risk of causing disease in humans remains controversial. Porcine retroviruses (PERVs) are now one of the big safety barriers preventing us using pigs as organ donors.
Researchers have long believed that they could use xenotransplantation (transplant between different species) with our porcine friends, as their physiology is the closest match and they don't carry the same ethical baggage as other members of the animal kingdom, such as chimps or baboons.
Piglets cloned from the genetically modified cells were found to be free from all Pervs. "If you could help them with a pig organ, wouldn't that be wonderful?" This makes it possible for organs from pigs to be transplanted into humans in the future. Despite pig organs posing as prime candidates for human transplantation considering their similar size and function, they generally, and unsurprisingly, trigger significant immune rejection responses in humans.
Numerous porcine embryos and fetuses cloned in the CRISPR experiments died before birth or shortly after, but scientists ended up with 15 living female piglets, the oldest now 4 months old.
Yang, was so determined in using the Gene Editing to cater various problems and since years, she has been trying to solve the shortage of organs. "We were able to get cells to grow even with very aggressive gene editing", Yang said: 100 percent of the cells doused with the chemical cocktail were 100 percent PERV-free.