China Focus: China-born clones bring pig organs closer for human transplants

Illustration by James Bareham  The Verge

The advance, reported ...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.

Cloning often fails; most of the embryos and fetuses died before birth, and some piglets died soon after they were born. She promised that their team will continue to engineer the Perv-free pig strain to make xenotransplant safe and effective.

Yang believes that CRISPR can accomplish what previous approaches have not: make multiple, simultaneous changes in pig DNA so that the animals' organs work, and work safely, in people.

Ultimately, these genetically altered pigs could be raised specifically for the harvesting of organs for transplant.

More than 117,000 Americans are now on a transplant wait-list and 22 people die every day awaiting a match, according to federal figures.

Pigs show potential as organ donors for humans as their organs are similar in size and function and they can be bred in large numbers. But in the late '90s, the discovery of a type of retrovirus in pig DNA complicated matters.

The first form of xenotransplantation - using animal blood to transfuse humans was first attempted in the 17th century, though as surgeon David Cooper put it in a 2012 review paper, "perhaps not surprisingly, the results were mixed".

But the lead researcher in the study told The New York Times the first transplants could happen within two years. In addition to making strides in eliminating retroviruses from pigs, the company is also looking into how to create pig organs that won't produce an immune reaction in humans.

By using the same technology used to create Dolly the sheep, the new genetic information could be placed into a pig's egg to form embryos. Knocking out three in particular could protect pig organs from being attacked by the human immune system, he said; lab macaques that received kidneys from the pigs have survived as long as 499 days. Another greater risk involved is that all the viruses of the animals, dwelling in them will infect the humans more.

Today, 15 are still alive with ages ranging from one to four months.

Pigs have always been seen as a viable source for organ transplants to humans because their organs are similar in size. The waiting list for organ transplants is now about 120,000 individuals long, which is twice as long as it was in 1999. So, they turned to the flashy new gene editing tool, CRISPER-Cas9, to slice up and deactivate all instances of PERV genes in a pig cell line. This adds to the growing number of transplants that are already in relatively widespread use in medicine (heart valves, skin grafts for burn patients, etc.).

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