The latest landmark development in the field comes from a team of scientists who successfully created genetically modified piglets free of 25 retroviruses that are generally present in pigs but thought to cause harm to humans.
Transplanting organs from pigs is a long-held ambition of scientists the world over - perhaps unsurprising, as around 22 people die daily in the U.S. alone on average waiting for various organs to become available. We have known that pigs have PERV (porcine endogenous retroviruses), which might turn to be extremely fatal to the humans.
These human cells then had the ability to infect other human cells, which raised concerns that transplanting the organs into humans could activate the virus and create a new human disease.
When they implanted the embryos into sows, they found that the resulting piglets exhibited no signs of PERVs, with some piglets surviving up to four months after birth. That was the first step Egenesis took back in 2015 when it inactivated 62 virus genes in pig embryos.
However, there's no way those pig organs could actually be transplanted just yet, Ross says. The entire process of transplant saves many lives, but every time, there is a shortage of organs as people are not actually willing to donate their organs.
To do that, you first genetically modify pig cells.
Scientists still need to overcome the problem of human bodies rejecting animal transplants - and the fact that human and pig organs are physiologically incompatible. Also the numbers needed for the transplants to meet the waiting lists is far less than the number of pigs killed each year for food. Pig heart valves already are routinely transplanted into patients. Now they have taken the genetic material from such cells and, using a similar technique to the one used to clone Dolly the sheep, inserted it into pig eggs. And the world's largest pork producer is exploring how to grow tissues and organs that could be used in human transplants. It is followed by livers, hearts and then lungs.
"The chance of transmitting Perv from the pig organ to the human cells was a significant barrier and the study shows yet another application of the Crispr-Cas9 system".
"This research represents an important advance in addressing safety concerns about cross-species viral transmission", Yang said.
Other scientists have also used CRISPR to produce pigs with altered genomes, including pigs in which a gene that triggers organ rejection was eliminated.