The availability of organs for transplant is a matter of life and death for thousands of patients. Unfortunately, the long list of people who wait for lifesaving organ transplants in the United States underlines a shortage of donors.
Obstacles To Xenotransplantation
The ability to breed animals, such as pigs, for the purpose of transplanting their organs to humans, however, can help address the current crisis, and a new breakthrough offers hope that this could be possible in the near future.
One of the obstacles in the idea of using pig organs in humans is the concern that the retroviruses present in pigs may be deadly to humans, or may cause other unwanted consequences such as tumors, immunodeficiencies and epidemics.
The porcine endogenous retroviruses, or PERVs, in pigs, for instance, are permanent part of the animals' gene so they appeared impossible to remove.
Removing Pig Retroviruses Using CRISPR-Cas9
Researchers though were able to remove those PERVs from the genome of the pig using the gene-editing technology CRISPR-Cas9, a process that eliminates one of the biggest barriers to xenotransplantation, the transplantation of organs from pigs to humans.
After using CRISPR to remove the retroviruses from the DNA of the pigs' cells, the researchers placed the cells into an egg that eventually developed into embryos and piglets.
Pig Clones Without The Retroviruses
The piglets, which appeared healthy regardless of their edited DNA, were genetically identical to the pig, where the first cell was sourced. This means that the researchers did not just manage to edit the genome of the pig. They also created clones.
Cloning is not often successful because most of the embryos and fetuses died even before being born. Study researchers George Church, from Harvard University, and colleagues though got 15 living piglets without the retroviruses. The oldest of these animals is now 4 months old.
Pig Organs For Use In Human Patients
The experiment could pave way to commercially available pig organs for use in human patients. Church has founded a company called eGenesis in the hopes of selling such pigs. Church said that the company aims to engineer pigs with organs that are very compatible with patients that taking anti-rejection drugs would no longer be necessary.
"Our study highlighted the value of PERV inactivation to prevent cross-species viral transmission and demonstrated the successful production of PERV-inactivated animals to address the safety concern in clinical xenotransplantation," the researchers wrote in their study, which has been published in the journal Science.