Hope that organs from animals can ease the shortage of human ones for transplantation has led scientists to continue studying xenotransplantation, the process of taking an organ from one species and transplanting it into another. Experiments in transplantation between humans and animals have been occurring for the past 50 years with mixed results. For xenotransplantation to work, researchers must find a way to block the human body's ability to recognize an animal organ as foreign and attack it. Scientists must also develop methods to keep viruses, possibly carried by these organs, from entering the human population.
Views among transplant surgeons and researchers regarding xenotransplants range from a belief that science will prevail to a view that the problems inherent in xenotransplantation are insurmountable. Despite initial successes - in 1963 a patient lived 9 months with a chimpanzee kidney and in 1984, Baby Fay survived 20 days with a baboon heart - these advances neither significantly prolonged the patients' lives nor improved their quality of life. Even as recently as 1994, medical researchers remained optimistic, and the National Institute of Health funded a half dozen studies, while private corporations funded even more.
The potential uses for nonhuman organs are numerous. One particularly compelling example is the possibility of harvesting Islet cells from pigs for transplantation into type 1 diabetics to free them from insulin dependence. Today, using human donors, one islet cell transplant requires more than one human pancreas to obtain the right amount of islet cells. The current shortage of human donor organs makes it a difficult operation to perform on diabetics today.
Although organs and cells from pigs are thought to be the most compatible with humans, viruses that can pass from pigs to humans remain a significant threat. Despite this, today pig heart valves are implanted into humans during cardiac surgery with excellent results and no such risks. In the future, it is expected that scientists will learn how to prevent viruses from passing from one species to another, although today, they are trying to understand what exactly those threats would be.
In addition to the medical obstacles to xenotransplantation, there are social issues as well. Animal rights activists are concerned about the potential for raising primates for organs. A survey was conducted by the National Kidney Foundation in 1999 to gauge the public's views regarding xenotransplantation. More than 85% of the general public and health professionals surveyed had heard of xenotransplantation and 71% said they would consider a xenotransplant for a loved one if the organ or tissue were not available from a human.
Xenotransplantation may require more time to overcome its obstacles but it is still believed to have the most potential for providing life-saving organs for the more than 87,000 people today currently on the waiting list for organs.