Saved by the Animals?

From the WebMD Archives

March 2, 2001 (Washington) -- At the University of Pittsburgh, researchers are preparing to test live liver cells derived from pigs to help clean the blood of about 15 patients with acute liver failure.

One of the first human experiments approved by federal regulators to evaluate whether live animal cells can functionally replace a failed human organ, the Pittsburgh experiment could lead to a way to alleviate the nation's desperate need for organ transplants.

The experiment will help establish whether animal cells and organs actually can perform the same critical functions as human cells and organs -- a question that continues to plague the emerging field of xenotransplantation, the official name given to the process of replacing ailing human organs, such as livers, kidneys, and hearts, with live animal organs.

According to a report released earlier this month by the nation's organ transplant network United Network for Organ Sharing, the number of people waiting for an organ transplant increased more than five times as fast as the number of transplantations.

So far, five patients have been recruited for the Pittsburgh study, which is sponsored by Minneapolis-based Excorp Medical Inc.

"The principal reason that we believe the technology is likely to be efficacious is the results from our animal studies," Daniel Miller, PhD, president of Excorp Medical, tells WebMD.

In those studies, the researchers used the same pig liver cells to prolong the lives of dogs with liver failure.

Although the results of the human studies are likely to differ, Miller says these animal studies demonstrated that pig liver cells are at least likely to mimic their human equivalents.

"The concept is sound," he tells WebMD.

Given that about 40,000 Americans die each year from liver failure, the process also could prove to be a lifesaver for the estimated 17,000 Americans currently awaiting a liver transplant.

A mere 4,500 human livers become available for transplant each year.

This growing demand for organs also is what spurred Miller's interest in the process and what is spurring the general interest in xenotransplantation.

Despite progress in the field, some experts question whether xenotransplantation will ever become a viable solution for the organ shortage.


The primary concern? The lack of any real assurance that using animal organs in humans is safe and will not lead to the emergence of a potential new virus.

Xenotransplantation could increase the risk of creating a novel virus because it breaches traditional barriers between animals and humans, such as the skin, explains Alix Fano, MA, executive director of the Campaign for Responsible Transplantation, an international coalition that wants to ban further research into xenotransplantation.

"That's unacceptable when you consider that animal viruses have the potential to wreak havoc on human populations," she tells WebMD.

As examples, Fano cites the current AIDS epidemic and the swine flu epidemic of 1918, which killed about 20 million people worldwide.

"The promise of xenotransplantation has been clearly exaggerated," Fano says. "There is no question that this process is largely being driven by an irresponsible desire for money."

Still, others maintain that this research should still be pursued despite the questionable motives that have helped fuel the rapid growth of xenotransplantation research.

The immediate promise was exaggerated, agrees Daniel Salomon, MD, a transplant surgeon and associate professor of molecular medicine at the Scripps Research Institute in La Jolla, Calif. But the eventual benefits could still easily outweigh the risks, especially when considering that people already face the risk of contracting an animal virus almost everyday, Salmon says.

"The problem is that we won't know that for sure until we conduct further research," says Salomon, who also serves on two government committees charged with advising federal regulators on how to regulate xenotransplantation. "If you are not doing transplants in humans, it's all talk."

Salomon also points out that other countries are now pursuing xenotransplantation research, meaning that these risks already are being taken without any follow-up to determine whether transplanting animal organs into humans will increase the risk of transferring an animal virus.

"The research is going forward," he tells WebMD. "The fact is researchers in places like Russia or Tijuana don't care what's happening in the U.S. or Europe."

In the U.S. and Europe, health concerns have limited human xenotransplantation research to devices, such as the one currently being developed and tested by Excorp Medical. Because the devices would be used outside the body, the animal cells and the human cells do not come into contact; therefore, these type of devices have not provoked the same level of concern.


Though xenotransplantation trials also have been proposed for the treatment of Parkinson's disease, Huntington's disease, and type 1 diabetes, the chance that federal regulators will allow for mass research into animal-to-human organ transplantation in the near future appears to be ebbing.

"It seems, therefore, that the likelihood of whole-organ xenotransplantation ... being available within a clinically worthwhile time frame may be starting to recede," the advisory committee concluded in a recent report.

Still, it is worth a shot, Salomon tells WebMD.

"[M]y point of view as a transplant surgeon is that we should pursue all venues," he says. "There are always people competing for resources, but until you have met someone waiting for a transplant -- you just can't realize how tragic this organ shortage really is."


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