US researchers' new gene modifying technique to open up pigs-to-human organ transplant

14 October 2015

US researchers have used a new gene modifying approach to eliminate dangerous virus genes that had impeded the usage of pig organs for transplants in people.

The research, reported in the journal Science, enhances the capabilities of the genome enhancing software often called CRISPR–Cas9, which works like molecular scissors to selectively trim away undesirable components of the genome.

The technique had earlier been used to do away with six areas of the genome at one go. In the latest research by Dr George Church, a geneticist from Harvard Medical Faculty, scientists concurrently snipped away genetic materials in sixty two specific sites in the pig genome.

Whereas Church's research had proven that it was possible to drastically edit the genome of pigs to eliminate native pig viruses from pig cells, it had not proven that such organs could be secure to make use of in people.

However, Church said in a that he believed the expertise will in the future make it possible for pig organs to be used in humans when human donor organs are not available.

"Basically, this whole field has been in the doldrums for 15 years," Church told Science Magazine. "There's been kind of a few true believers that had it on life support. But I think this changes the game completely."

In the new study, Harvard researchers disrupted 62 copies of the PERV gene in an pig's kidney epithelial cell line and when they were introduced to human cells in the lab, a nearly 1000-fold decrease in PERV transmission was seen.

According to the researchers this showed that the virus could be inactivated for clinical application to pig-to-human transplants.

Church told Nature that the researchers also changed over 20 other pig genes that caused an immune response in human cells. According to Church, for pig organs to be a viable option for human transplant, both sets of modifications would need to be made.

"It was kind of cool from two stand points," Church, told the BBC. "One 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 to be solved in the xenotransplantation field. With immune tolerance, that completely changes the landscape as well. These two things, immune tolerance and now getting rid of all the retroviruses, means we have a clear path."

Last month scientists in the UK applied for permission to edit the genes of human embryos in a series of experiments aimed studying the earliest stages of human development. (See: UK scientists seek permission to edit genes in human embryo).

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