The shortage of human organs for transplants is one of the biggest problems facing the medical field, about 22 people die on waitlists for organs die every day in the United States. But there is a newfound hope! A recent discovery using CRISPR-cas9 gene editing may address this challenge.
Scientists have been dreaming about transplanting organs from pigs into people for years, a process called xenotransplantation, but they have been held back by threatening viruses in the pigs DNA called PERVs. PERVs are present throughout the pig genome and would infect a person who receives a pigs heart, lung, kidney, etc. This infection could be fatal and may cause a human epidemic. Scary right? However, scientists at well-known laboratories had a breakthrough this past summer using CRISPR-cas9 and created healthy pigs with no traces of PERV genes!
It was, in fact, the two early developers of that gene-editing technology, Harvard University’s George Church, and Luhan Yang, who first believed CRISPR’s guide RNA and a DNA-slicing enzyme could make precise, genome-wide changes to pig cells. Their results showed that CRISPR could “knock out” PERV genes at all 62 sites in the pig genome. However, there were some flaws in their experiments, they used a line of “immortal” pig kidney cells, which were chosen for their ability to survive in the dish. Earlier the team had tried to use genetically “normal” pig cells, but once the cells were edited they failed to grow normally. Yang says, “CRISPR’s hacking job of the DNA may have prompted them to stop dividing or self-destruct.” But when they exposed the cells to a “chemical cocktail” making them “immortal,” the growth of PERV free cells in the dish rose to 100%. The next step was to actually produce piglets. The researchers inserted DNA containing the nuclei of the edited cells into the eggs taken from the ovaries of pigs in a slaughterhouse. They allowed each egg to develop into an embryo and implanted it in the uterus of a surrogate mother. Boom, healthy, PERV-free piglets!
After this huge finding, Church and Yang co-founded a company called eGenesis which focuses on the engineering of transplant organs and projects in laboratories around the world exploded. Currently, a transplant surgeon at the University of Maryland is gearing up to swap a pig heart into the chest of a baboon! However, obstacles still remain in regard to humans; the rejection of the organs once in humans, the physiological incompatibility, how to insert genes that will prevent toxic interactions with human blood, and (what I believe is most important) the ethical question.