More than 100,000 people in the United States need an organ transplant, but demand always outpaces supply. An average of 20 people in the nation died every day in 2016 because organs were unavailable, and that was despite record annual donations of more than 33,000.
Physicians have proposed many solutions to encourage organ donations, including payment. But scientists are looking elsewhere to ensure a better supply. Thanks to advances in genetic engineering, a new twist on using animals for transplants offers promise. Since the 1960s, a handful of patients have received an animal organ — xenotransplants of everything from a baboon liver to a whole chimpanzee heart. But many patients died because their immune system rejected the transplant.
Attempting to outwit evolution, Hiromitsu Nakauchi, a physician and geneticist at Stanford University, proposed a solution to this immunity problem: Instead of transplanting an animal’s organ, scientists could grow a customized human organ in an animal. By adding a patient’s own stem cells to an engineered animal embryo, Nakauchi and others hoped to grow a new, healthy organ ready for transplant.
Nakauchi was the first to demonstrate that the idea of growing one species’ organ in another species’ body was even possible, first between mice and rats in 2010. Another research group grew human cells in a pig in 2017, offering further proof of principle. Nakauchi recently reviewed his process in the Annual Review of Cell and Developmental Biology. We talked with him about this promising frontier as well as its many scientific, health and ethical challenges.
This conversation has been edited for length and clarity.
