Xenotransplant is transplantation of organs, valves or other medical products (like blood or stem cells) between species that may or may not be similar to each other. In most human medicine, this means harvesting some parts of animals to be used directly in human bodies. In some cases this is common treatment, such as in the use of bovine (cow) or porcine (pig) valves to replace faulty human heart valves. In other cases, the idea of xenotransplantation is principally theoretical and experimental, with little strong evidence of benefit. Despite lacking evidence for the efficacy of most procedures, many medical researchers believe xenotransplant technology is pioneering work that may improve medical care, though there exists objections to the practice among animal rights advocates.
The most potentially beneficial uses of xenotransplants would be to transplant organs from animals to humans, and in a few limited cases this has been tried in humans. It has not been successful due to the pronounced rejection that occurs, even if the organs are transplanted between similar species, like baboons to humans. This matter is still being researched, often by performing animal-to-animal transplants.
Other types of xenotransplant that have been explored in limited trials include injecting cells from animals into humans. For example, fetal pig cells may have curative or helpful properties in treating brain disorders. Generally, concerns about rejection are much lower when more minute elements of a species, like cells, are transplanted. This isn’t always true; blood xenotransplantation isn’t successful because it’s hard to find matches between human and animal blood types.
Since the 1970s, a number of xenografts have been successful. Cardiothoracic surgeons routinely replace faulty human heart valves with porcine or bovine valves. Contrary to popular belief, porcine valve replacement is not a violation of Kosher principals, and there can be advantages for choosing a pig or cow valve over cadaver human valves. They are just as effective and more readily available, while cadaver valves can only be harvested from people who gave permission before their deaths.
In this last statement lies the principal ethical objection to xenotransplantation. Animals can’t and don’t choose to be transplant subjects, and they usually have to be killed in order for a transplant to occur. Some detractors argue this is unnecessary exploitation. Especially since pigs are so often killed, those in support view a xenotransplant as not much different than farming, but those opposed to it may also be opposed to raising animals for food.
Another concern, which may or may not arise from ethical considerations, is the possibility of spreading animal germs to humans, which could result in serious public health concerns. This is another reason pigs are frequently used: humans and pigs have cohabitated for millennia and have been exposed to each other repeatedly. Thus far, the xenotransplant research that exists doesn’t show ready spread of viruses between species, but this would need to be given attention with greater use of the technology. The principal barrier, though, is still rejection of the xenotransplant, and without resolving this issue, the technology may remain limited in scope.