Physicans `Pig Out' on New Transplant Ideas

BOSTON-A miniature pig, which average size is still more than 300 pounds, just might be the answer to the shortage of transplant organs in the US. Researchers are beginning to clone and genetically modify pigs to recreate organs for humans.

With more than 77,000 Americans on a waiting list for a new organ, and only 23,000 transplants being performed each year, scientists have been searching for a new organ supply source. This number is also not representative of those in need of a new organ, because many are not included on the list. If a patient is 65 or older, unhealthy, or has a substance abuse problem, he or she is not even under consideration for a new organ.

Miniature pigs, which grow only one-third of a regular pig, grow organs that are comparable in size to a very large person.

With this in mind, there are more than 20 labs globally trying to produce pig organs that are ready for human transplantation. A cross-species transplantation is known as xenotransplantation, from the Greek xenos, which means foreign.

Scientists have already transplanted these pig organs into baboons and have had modest success. However, the idea of transplanting these into humans carries an ethical burden. Not only could the transplanted organ carry a previously undetected cross-species virus, known as xenozoonoses, but it also was taken from an animal that was created to be slaughtered. There are many who think this is wrong, although researchers argue there were more than 98 million pigs killed in the US last year for meat. Some say a pig's place on the food chain means there would not be ethical qualms about the animal's organs being used for transplants.

There is also the concern of religion. Both Judaism and Islam do not eat pork products because of their faith. Would those following these religions be able to receive a pig's organs?

Researchers have several years before having to answer these questions and dilemmas.

David H. Sachs, an immunologist and surgeon from Massachusetts General Hospital said the fact these animals have the potential of donating organs for humans is amazing. He has been working for more than 30 years with a group of swine. The problem he is hoping to solve is the human body's resistance to foreign flesh.

He explained that all creatures from bacteria up to New World monkeys carry a sugar known as alpha-1-galactose, or alpha-gal. This sugar coats cells in every creature except Old World primates and people. The result is human antibodies attack the sugar and immediately reject any material it is associated with.

Sachs is trying to create pig organs that are healthy and productive without the alpha-gal sugar. Human antibodies kill the organ by triggering enzymes. The solution is to prevent the enzymes from attacking the sugars, but the goal has yet to be reached.

Scientists have also created "knock-out pigs" whose gene for the alpha-gal has been knocked out of every cell in their system. However, researchers are still trying to add other human genes to pigs to prevent blood clots and other transplant complications.

Ideally, they want to fool the human body that the new organ is not foreign. Sachs thinks by transplanting the thymus gland, which eliminates T-cells that accidentally target the body's own tissue, or some of the donor pig's bone marrow, xenotransplants may be more successful.

The possibility of pig organs being used for human transplants in hospitals nationwide is several years away, although there are experimental surgeries being performed today.

Information from the Associated Press

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