Virtual liver in the works could be a real lifesaver

RESEARCH TRIANGLE PARK, N.C. -- Forget virtual reality - the U.S. Environmental Protection Agency is building virtual human organs.

The EPA's "virtual tissue" researchers are developing a set of computer simulations that may one day be able to identify the risks posed by common industrial pollutants such as pesticides without testing them on animals.

Last week, the EPA awarded nearly $3 million to four groups - including North Carolina's Hamner Institute and the University of North Carolina at Chapel Hill - to expand its virtual liver project. They will collaborate with current virtual liver researchers based at the EPA's National Center for Computational Toxicology in the Research Triangle Park.

The team is particularly interested in creating a computerized liver because it's often the first organ to be injured by toxic chemicals, said Dr. John Wambaugh, a physical scientist at the EPA who works on the project. When we encounter a poisonous chemical such as Freon, he said, "the liver is like the Secret Service agent that jumps in front of the bullet."

The liver's defensive role in the body has made it a crucial part of chemical safety experiments. Traditionally, though, scientists have done these experiments using laboratory animals like mice and rats. "Right now, they're the gold standard," Wambaugh said.

Gold standard or not, these studies are far from perfect.

First of all, animals simply aren't humans. There's no way to guarantee that something safe for animals will also be safe for people, Wambaugh said.

Complicating the issue, laboratory animals are typically bred to be as identical to each other as possible. This helps researchers be sure that sick animals in an experiment are only getting sick from the chemical they're testing, not from any other cause.

But humans are usually far from identical. Knowing how a chemical affects a set of nearly identical animals and trying to extrapolate that to how it will affect all humans is very difficult, Wambaugh said. Scientists aren't just interested in how a chemical might affect healthy adults; they also want to find out how those suffering from different diseases might be affected.

Given that a single animal experiment can take two years to complete, and that there are more than 10,000 chemicals the EPA is interested in studying, testing the impact of every chemical on every group just isn't possible - it would take too much time, and too much money.

And even testing a small fraction of these chemicals would require huge numbers of animals, something that might concern animal rights activists who already question the ethics of using animals at all.

If potentially harmful chemicals can be tested on a computer model of a human liver, though, scientists could not only avoid animal experiments, they could dramatically speed the testing process by simulating years of chemical exposure in a matter of days or even hours, depending on the speed of the computer.

The virtual liver project is only one of several virtual human tissues in development at the National Center for Computational Toxicology. The center also hopes to create a virtual embryo, enabling scientists to study how newborn babies might be affected if their mothers are exposed to dangerous pollutants during pregnancy.

Other projects, like a simulated cardiovascular system, may eventually be developed as well, according to Dr. David Dix, deputy director of the National Center for Computational Toxicology.

Though the virtual tissue teams hope to eventually be able to replace animal testing altogether, in the short-term the projects will be used just to figure out which chemicals are most important to test.

It's a starting point, said Dix. "Having some information is better than having no information," he said, "and for the majority of chemicals, that's where we're starting from."