Pig organ transplants a step closer

Scientists discover a way to modify DNA to bypass problem with human rejection. Photo / iStock

Scientists discover a way to modify DNA to bypass problem with human rejection

Pig organs could soon be transplanted into human patients after Harvard University scientists found a way to genetically modify pig DNA to be more compatible with humans.

Scientists have spent decades trying to engineer pig tissue so that it would not be rejected by the human body, but the immune system has always prevented success.

All pig DNA carries the porcine endogenous retrovirus, which infects human cells and makes transplantation impossible.

Now, Professor George Church and colleagues have employed a groundbreaking technology called Crispr to snip away the retrovirus' genetic code.

In tests on early pig embryos, Church was able to eliminate all 62 copies of the retrovirus that would have been spotted by the human immune system. The modified cells were 1000 times less likely to infect kidney cells when transplanted in the lab. The team hope to create retrovirus-free pig clones whose organs can be harvested.

Although researchers still need to get over the hurdle of the immune rejection, Church said the discovery opened the door for transplanting animal organs into people, a practice known as xenotransplantation.

Church, who part-owns a company that wants to develop modified pigs to grow organs, said: "It was kind of cool from two standpoints. One is, it set a record for Crispr or for any genetic modification of an animal, and it took away what was considered the most perplexing problem ... in the xenotransplantation field."

The team unveiled their success at a workshop at the National Academy of Sciences in the United States, which has been studying potential risks and ethical concerns of human genome editing.

Currently, pig heart valves that have been scrubbed and depleted of pig cells are commonly used to repair faulty human heart valves. But plans to transplant whole pig organs are likely to spark a global ethical debate.

Earlier this year, Chinese scientists carried out the first experiments to alter the DNA of human embryos and British researchers last month applied for permission to do the same.

Critics say such research could herald an era of designer babies where parents not only select for health, but also for height, eye colour, sex and even sexuality.