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New in vitro model presented to estimate the eye irritation potential of chemical substances

02/2003, 13.02.2003

An alternative method to animal experiments could considerably increase the power of existing test systems

According to the 7th Amendment to the EU Cosmetics Directive which has just been adopted, no cosmetics containing ingredients tested in animal experiments may be marketed in Europe from 2009 onwards. An exemption up to 2013 has only been granted for three tests for which no alternative methods will probably be available by 2009. In future, the base set relating to the safety toxicology of chemicals with low production volumes (pursuant to the White Paper EU Strategy for a future chemicals policy) is also to be obtained without using live animal experimentation. These political decisions should not just be seen as a major success for animal welfare. They also impose stiff requirements on all the scientists involved in the development and validation of alternative methods to animal experiments. A promising new non-animal model was presented today at the 57^th ZEBET Seminar in the Federal Institute for Risk Assessment. It could markedly increase the validity of existing test systems or even replace them.

The new in vitro model is to be used to assess the eye irritation potential of chemical substances. Whether a substance irritates or damages the eye is, in addition to statements on acute toxicity and contact allergenic potential, part of the important toxicological base set. This is the information which must be available if a substance is to be used for instance in cosmetics. Up to now, information on eye irritation potential could not be obtained at all or not fully without animal experiments. That's why, the Draize Rabbit Eye Test, which is extremely stressful for the experimental animal, is still being used. The alternative methods recognised at present in the European Union (embryonated chicken egg, bovine cornea, isolated hen's eye and isolated rabbit eye) only permit a statement about the severe eye irritation potential of the substances. Less severe (but under some circumstances permanent) damage to the cornea cannot, for instance, be predicted with these tests. This is because, with the exception of the embryonated chicken egg, they do not use living tissue and none of the tests is organ-specific. The human cornea model presented at the seminar in BfR fulfils both of these criteria. It is based on living, human corneal cell lines.

The model was elaborated by scientists in the Institute for Biophysics of the University of Bremen with research funds from the Centre for Documentation and Evaluation of Alternatives to Animal Experiments (ZEBET). In the space of just one year the scientists Maria Engelke, Jens Patzke, Svitlana Tykhonova and Michaela Zorn-Kruppa have succeeded in reconstructing a human three-dimensional in vitro model of the ocular cornea. It consists of a multilayered corneal epithelium, a single-layer endothelium and a collagen matrix with intercalated keratocytes. Validation will show whether this model is capable of increasing the predictive force of existing alternative methods or even of replacing them in the longer term.

Since its foundation in 1989 in the former Federal Health Office (BGA), ZEBET has been actively involved in the development and validation of alternative methods to animal experiments. Some of them have been taken to the stage of global recognition by OECD member states. In addition, ZEBET has had an annual budget of € 350,000 since 1990 which it uses to support between eight and ten research projects with new, promising approaches to the development of alternative methods.

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