BRIDGETT NOVAK, REUTERS Health
POSTED: Friday, April 4, 2014, 4:08 PM
NEW YORK (Reuters Health) - A validation study, presented March 25 at the annual meeting of the Society of Toxicology in Phoenix, has demonstrated that the testing of chemicals for skin sensitivity on in vitro human cell tissue can achieve similar results to those achieved via animal testing.
Previous studies tested the process in-house; this new study was conducted to determine if the results held up in two different laboratories. The researchers applied 10 different chemicals in various concentrations to EpiDerm, a three-dimensional human cell tissue that has been approved by the Organization for Economic Cooperation & Development (OECD) for skin corrosion and irritation tests. Each chemical was assessed three times and compared to positive and negative controls to ensure consistency.
Twenty-four hours after application, all of the tissue samples were measured for cytotoxicity and their reaction to glutathione (GSH). By isolating the RNA in each sample, the expression and potency of seven different genes that are known predictors of skin sensitization were also measured. Researchers noted the lowest concentration of chemical required to produce significant sensitivity, the number of genes that responded and the magnitude of those responses.
All of these factors were weighted for importance (via a proprietary algorithm developed by Cyprotex/CeeTox) and an "In Vitro Toxicity Index" was produced for each test chemical to determine if it was a skin sensitizer (i.e., predictability), and if yes, if its effect should be considered weak, moderate or strong (i.e., potency).
"The human tissue determined the predictability of skin sensitivity on par with that found in the animal studies in 10 out of 10 samples tested. Potency was the same as found in the animal studies in five to seven of the 10 samples, depending on the lab," noted Dr. Amy Clippinger, lead researcher and science advisor to the International Science Consortium of PETA (People for the Ethical Treatment of Animals).
"The ability to predict potency is a real step forward," Clippinger told Reuters during a phone interview. "The guinea pig assay can't determine potency. You can determine potency only if you combine other in vitro methods, but this SenCeeTox assay is the only one we know of that can predict potency on its own."
"This appears to be a kinder and gentler approach for testing certain skin allergens," observed Dr. Clifford Bassett, assistant clinical professor at New York University's School of Medicine and a fellow of the American College of Allergy, Asthma and Immunology (ACAAI). "It should help satisfy European Union (EU) regulations and reduce animal cruelty and exposure."
The EU and Israel currently ban both the testing of cosmetics on animals and the marketing of products that were tested on animals; India and Sao Paulo, Brazil ban the testing component. In addition to the compliance factor, Clippinger added that "in vitro methods are generally cheaper, faster and more objective than animal testing and more human-relevant."
In terms of next steps, Clippinger said, "To have an assay validated and accepted by regulators, you generally need to test it in three different labs. We have run the test in two labs. We plan to conduct the test in one more lab and then submit the results to the European Union Reference Laboratory, a validation group. This study has shown that this method is as good or better than the animal model."
She predicts the next phase of testing should be completed by mid-2015.
This study was supported by PETA and Cyprotex/CeeTox.