It’s not news that pigs have been subject to the gene editing tool of CRISPR for the past few years, in an attempt to create organ regeneration. 

Last August, a group of scientists led by George Church, professor of genetics at Harvard Medical School, generated more than a dozen pigs that were bred without certain viruses that had made many of their organs unusable for human transplant. Pig genomes often contain genes for viruses that can cause infection and, if they spread to certain tissues, even cancer. 

To ensure that all of the tissues in the pigs were free of the viruses, Church and his team used a cloning technique to create embryos from the edited cells, writes Time. Of 37 pigs that were born, 15 survived, and none showed genetic signs of the viruses. 

As a result, Church believes that pig-to-human organ transplant clinical trials could happen in as little as two years. Such progress would help address the organ shortage that keeps more than 110,000 people on the transplant list each year. 

Despite the advancements, it will come as no surprise that such work has come under some serious fire. Medically, doctors don’t actually know whether viruses or other microbes that are common among animals could spread to people via the transplants, even though they have tried to control them. The act of creating animals solely for the purpose of using their tissues to help treat human disease also raises a number of ethical issues. 

Scientists do however see a future of possibilities of how CRISPR might be used to create organs. In particular, researchers at the Salk Institute in La Jolla, are exploring ways to grow human organs in pigs, by eliminating pig genes and inserting human ones. In 2017, they made the first human-pig chimera by introducing human stem cells into early pig embryos. Strategies like this could provide a new source of human tissues and organs. 

For Church, the act of stripping away viral genes is only the beginning. He believes that CRISPR will be useful in eliminating other parts of porcine DNA that make pig tissues incompatible with humans. He suggests that genetic editing could lead to organs that are such a good biological match that people would not need to take anti-rejection drugs that can cause so many side effects. If this is made possible, then transplanting tissues could become a way to prevent some of the most common diseases. “Cells and organs that are resistant to cancer, pathogens, and senescence could be better in a preventive sense than the normal human organs that are being replaced,” he explained.