Gene editing techniques could prove useful for removing virus genes from the pig genome, paving the way for pig-to- human transplants, yet efforts have so far only been successfully demonstrated in cell lines, not live animals.
According to the scientists, the piglets were born healthy and completely free of retroviruses. The company said almost 118,000 people in the USA need a life-saving organ transplant and every 10 minutes someone is added to the waiting list.
More than 100,000 people need an organ transplant in the US.
Porcine organs can be the right size for human transplantation and, in theory, similar enough to function in patients.
Scientists have edited the pig genome to deactivate a family of retroviruses. They are now repeating the process to engineer male pigs, which Church says he doesn't expect to be any more complicated.
And the treatment of severe burns already involves animal tissue, with human skin cells cultured using animal feeder layers, harvested and then grafter onto the patient's wound to assist healing.
With modified genes, the scientists created PERV-inactivated pig embryos and transferred them into surrogate sows to produce clones, in the same fashion as Dolly the sheep was created.
Up to now, these grafts porcine face of the risk of transmission of viruses that can infect humans.
He said: "The viruses are particularly troubling".
The availability of organs for transplant is a matter of life and death for thousands of patients. However, there are many more stages of research to go and there are likely to be other practical, ethical and safety issues to overcome before using pigs as organ donors. Of those, 15 are still alive, and the oldest is four months.
He has also founded a company, in the hope of selling the genetically altered pig organs.
"Prof Darren Griffin, Professor of Genetics, University of Kent, says: "This represents a significant step forward towards the possibility of making xenotransplantation a reality", while Prof Ian McConnell, Emeritus Professor of Veterinary Science, University of Cambridge, cautions: "[Organ transplant] is a huge unmet need of modern medicine.