Aug. 23, 2001 -- They don't look like us, but researchers say pigs may someday save human lives because their organs and ours are very much alike.
"The heart is very similar, the kidneys are very similar, their function is very similar," says Dr. David Sachs of Massachusetts General Hospital in Boston. "So it really is a potential donor for almost all of the internal organs."
But not every pig is a potential donor. At a private research facility, Sachs is focusing on a particular breed: Inbred miniature swine.
"These animals are about the same size as human beings," says Sachs. "When they're full-grown, they get up to 200 to 300 pounds."
Will Humans Accept the Parts?
There are still major obstacles to replacing human organs with those of another species.
"The immune response, or the rejection of a pig organ, is much stronger than the rejection of a human organ," says Julia Greenstein, president of Immerge Biotherapeutics in Boston.
But researchers say they are solving that problem by genetically modifying pigs, which they plan to clone.
And they are experimenting with pig cells that could help prevent the human immune system from rejecting the new organ.
"We're trying to induce tolerance, so the recipient won't recognize the pig organ as foreign," says Greenstein.
Another concern is that a pig virus might infect humans. But that may be solved by a new line of pigs that do not appear to transmit the virus.
And scientists say there is real progress on making transplants work. In tests on primates such as baboons, pig organs, which once survived for only minutes, now function for up to a month.
Despite the advancements, there are still questions and concerns about the use of pigs as organ donors. Are there still unknown risks, unknown viruses, for example, that might be transmitted to humans?
"You have to balance that with the potential benefit," says Sachs. "And we see patients every day who are dying because they can't get a transplant."
Researchers believe human testing is three to five years away, and that transplanting pig organs into people could be an accepted procedure within a decade.
ABCNEWS' Barry Serafin and Nicholas Regush contributed to this report.