Just at the start of 2022, a man received a heart transplant from a pig. Yes — a pig. But how is this possible? How can an organ from a pink, furry animal be used in a human? Will he oink? All can be answered with the help of CRISPR: a tool for genetic modification.

CRISPR stands for “clustered regularly interspaced short palindromic repeats,” or
in simpler words, copies of smaller pieces of viruses. They are found in the DNA of bacteria. The immune system of the bacteria uses them as pieces of identification, like a big red flag,
to target the harmful viruses. This involves an important enzyme called Cas9 that works like scissors, cutting and removing the virus that disables it. “You can just point it at a place in the genome, and you can do anything you want at that spot,” said Robert Reed, a biologist at Cornell University. Because of CRISPR, humans can potentially edit any type of gene in plants or animals.

The idea of transplanting animal organs into humans is not new. There is actually a word — xenotransplantation — that means just that. There have been many attempts of transplanting tissues or organs from animals to humans dating back hundreds of years. Scientists have tried chimpanzee kidneys, baboon hearts, and many more, but the recipients have not lived longer than nine months.

So why pigs? Their organs have a relatively similar size and anatomy. They are also very easy to raise and can grow to human size within six months!

However, there has been a barrier in using pig organs for humans. The pig genes contain the DNA for a family of viruses called “porcine endogenous retroviruses”, shorter known as PERVs. As a result, the pig cells can produce and release PERVs, which may infect human cells and lead to the patient becoming sick.

This is when CRISPR comes in. Scientist George Church’s lab at Harvard Medical School used CRISPR to edit eukaryotic, non-bacteria cells. They wanted to prevent DNA polymerase, an enzyme involved in replication, from replicating the PERV DNA in pigs. By using CRISPR, they were able to inactivate the 62 copies of PERV DNA in pig embryos, its early growing stages, preventing the transmission of the virus when coming in contact with human cells.

“Gene editing with CRISPR has just really helped accelerate the field in sort of a warp drive,” said Joe Leventhal, who heads the transplant program at Northwestern University.

Though more scientific research is still required to perfect the idea, this is a breakthrough in many ways because there is a drastic shortage of organs compared to the large numbers of people waiting for transplants. Because of this, about a dozen people on transplant lists die every day. With the potential possibility of using pig organs in humans through gene editing, it provides an important opportunity to close the shortage and save human lives.