More than 100,000 Americans are waiting for organ transplants, often enduring terrible symptoms, emotional distress and difficult treatment for years. Thousands pass away before an organ becomes available. For decades, scientists have dreamed of xenotransplantation: using animals to solve the shortage of organs available for human transplant. Pigs, whose organs are about the right size and can be bred easily and quickly, offer a promising alternative. Xenotransplantation involves killing pigs to save humans, which some find troubling. The People for the Ethical Treatment of Animals, an animal rights group, says the organ shortage could be solved without killing animals. If the U.S. switched to an “opt out” organ donation system, requiring people to say they didn’t want to donate, rather than the current “opt in” system, there would be plenty of organs, the group says. So far, the biggest challenge with xenotransplantation research has been keeping study animals alive long-term with organs from a different species – something regulatory agencies want to see before human trials. #pigtohumantransplant #xenotransplantation