Tuesday, 27 March 2007

Genetically modified pigs could yield organs for human bodies

Recent medical advances may shine new hope on the otherwise dismal shortage of human organ donors, by allowing the organs of animals to be transplanted into human bodies instead. It may be awhile yet before the technology, known as xenotransplantation, reaches medical clinics; but when that happens, accusing someone of being pigheaded may take on a new meaning altogether.

Xenotransplantation has been studied and attempted for over a century, but few operations have been successful to date. According to Muhammad Mohiuddin, who studies xenotransplantation at the U.S. National Heart, Lung, and Blood Institute (NHLBI), the major stumbling block of existing techniques is that the immune system in the animal receiving the organ tends to reject the transplant.

"We are still learning about new immunological hurdles and have to overcome these barriers in non-human transplant models," Mohiuddin said.

To study these immunological issues, scientists have studied xenotransplantation across several animal combinations, including the insertion of hamster organs into rats, and later into mice, as well as the transplantation of organs from pigs to baboons.

In a recent paper published in the esteemed journal PLoS Medicine, Mohiuddin cites a study in which insulin-producing cells, called islets, from pigs were transplanted into monkeys with diabetes. This led to the complete reversal of diabetes for over 100 days, researchers said.

However, suppressing immunological issues in the pig-to-monkey studies involved giving the monkeys drugs called immunosuppressants in doses that would be too large to be administered in humans. To overcome the need for overly large amounts of immunosuppressants, Mohiuddin suggests organs be farmed from pigs that are genetically modified to be more compatible with humans.

"Taking out some molecules which are immunogenic to humans and putting in human molecules [in the pig] will make the pig organ more compatible to humans," he said. "This allows us to use safer immunosuppression methods, which are now routinely used in allotransplantation [organ transplantation from human to human]."

Pigs were chosen as potential donors for their organ size, which is said to be comparable to human organs, their short breeding cycle and large litter size, and our ability to genetically manipulate their immune system, Mohiuddin explained.

While there are still some hurdles between current research and the potential use of pigs in human organ donation, such as the objections of animal rights proponents and concerns to do with the transmission of viruses across species, Mohiuddin believes there is a strong case for further research into xenotransplantation.

"In [the] United States alone there are more than 90,000 patients waiting for organ transplantation and only 25,000 transplants were performed during last year," he said. "Most of these patients will die waiting for the organs."

"Xenotransplantation has the potential to save many lives," he said.


Tokes said...

Personally, I would prefer cybernetic implants to those from another animal. However if it was a choice between death and pig heart, I would probably go for the latter. But would pig hearts really be able to sustain the workload a human heart endures, and for the same time-span? Or would it be another case of "time to upgrade my hardware" every two years like PCs?

liz said...

Hm, well I assume the point of using pigs' hearts is that they are similar in size to human hearts, which suggests that they would be able to sustain similar workloads.

Life would suck pretty bad if you had to keep going for heart operations every couple of years. I'm not sure that your hypothetical would be so simple, if it's a choice between living in an almost-constant hospitalized state and death.