Bioengineered skin-grown in the lab using small samples of human cells-has been on the market since 1997. While such artificial skin was originally developed to help treat burn victims and other patients, it and other engineered tissues are gaining new cachet as alternatives to animal testing for some basic research and drug-development tests.

More than half a million animals were test subjects in the U.S. in 1997, the most recent year for which the U.S. Department of Agriculture provides data. For certain tests, such as those used to make sure that cosmetics and other consumer products won’t cause irritation, tissue models derived from human cells could soon help reduce the need for animal testing.

The tissue-model approach is already gaining momentum in Europe, where regulators have approved bio-engineered skin models for some toxicity and irritation tests. As a result, sales at SkinEthic Laboratories, a Nice, France, firm that markets lab-grown skin and eye tissue to researchers, are growing at a rate of almost 40 percent per year, according to Alan Goldberg, director of the Johns Hopkins Center for Alternatives to Animal Testing and a company consultant to SkinEthic. Similar approvals are expected early this year in the United States.

Pros and Cons

Proponents of these alternative tests argue that tissue models provide both ethical and scientific advantages. “The scientific community would like to go to in vitro approaches,” Goldberg says. “They’re quicker, offer better information, and are more humane.”

Since tissue models offer the opportunity to experiment on human cells, he says, scientists don’t have to extrapolate human responses from animal-derived data. According to William S. Stokes, a toxicology expert with the National Institute of Environmental Health Sciences’ Interagency Coordinating Committee on the Validation of Alternative Methods, bioengineered models also have the advantage of yielding test results that are easier to reproduce from lab to lab. That’s because the engineered tissues are uniform from sample to sample whereas slight biological differences between individual lab animals can sometimes affect test results.

Sill, even proponents of alternative testing acknowledge that tissue models have their limitations. Developing a new drug, for example, often requires experiments that reveal the drug’s effects on different organs-all interacting with one another. Charles Hewitt, director of surgical research for Robert Wood Johnson Medical School in Camden, NJ, uses bio-engineered skin in some of his research but says, “We can’t get all the responses we need to test just from our model.”

For now, bio-engineered models are finding a niche as tools to screen out drugs likely to fail in clinical trials. For example, the State University of New York at Stony Brook used lab-grown skin to evaluate a number of drugs being considered for nasal delivery. “We initially had gone to human trials, but that gets very expensive,” says Liz Roemer, senior research scientist in the pathology department. Using a bio-engineered model to weed out all but the best candidates for human tests proved to be more efficient and economical, she says.