Alternatives to Laboratory Animals

As Russell and Burch suggested more than 40 years ago, the most humane science is the best science. The path ahead is clear: pain and distress must be eliminated in animal experiments or reduced to an absolute minimum, and, as scientists, we must use the most humane approaches in our research. To accomplish the best science, we must train those who come after us in the principles and practice of humane science.

“Each of them necessitated the community's rejection of one time-honored scientific theory in favor of another incompatible with it. Each produced a consequent shift in the problems available for scientific scrutiny and in the standards by which the profession determined what should count as an admissible problem or as a legitimate problem-solution. And each transformed the scientific imagination in ways that we shall ultimately need to describe as a transformation of the world within which scientific work was done. Such changes, together with the controversies that almost always accompany them, are the defining characteristics of scientific revolutions.” (Thomas Kuhn, 1922–1996, on scientific revolutions)

“Change is scientific, progress is ethical; change is indubitable, whereas progress is a matter of controversy.” (Bertrand Russell, 1872–1970)

Epithelial crypts from the bovine colon were obtained by using a combined mechanical and enzymatic isolation method, followed by differential D-sorbitol gradient centrifugation. By using this isolation technique, a pure fraction of epithelial crypts with minimal mesenchymal contamination was obtained. The crypts were seeded in collagen-coated plastic flasks. The attached epithelial cells proliferated and formed a confluent monolayer after 6 days in culture. Under low-serum culture conditions (1% fetal calf serum), the cells had a population doubling time of 21–22 hours. During the culture period, the colonocytes were characterised morphologically and enzymatically. The morphology of the cultured cells was confirmed by scanning electron microscopy and transmission electron microscopy. The presence of microvilli, tight junctions and desmosomes demonstrated the ability of the cultured cells to restore an epithelial-like cell monolayer. The epithelial origin of the cells was demonstrated by labelling the cells with antibodies against epithelial-specific cytokeratins 7 and 13. The functional integrity of the cells was evaluated by measuring various marker enzymes (γ-glutamyltranspeptidase, acid phosphatase, alkaline phosphatase, NADH-dehydrogenase) and membrane-associated Na⁺–K⁺-ATPase activity. Membrane integrity was determined by measuring the leakage of lactate dehydrogenase into the culture medium. This new culture system for bovine colon epithelial cells could be used as an in vitro model of the colon epithelium in physiological and toxicological studies.

In cooperation with BAXTER Vaccine AG, which supplies incubated special pathogen-free chicken eggs (including a full veterinary record), a permanent hen's egg chorio-allantoic membrane test (HET-CAM) unit has been established, where angiogenesis testing, cell culture, and digital and histological analyses are performed. At the Core Unit for Biomedical Research, the location of the animal testing facility of the Medical University Vienna, cell–scaffold constructs must be evaluated in vitro and in ovo prior to eventual in vivo tissue engineering experiments. The animal testing advisory committee requires that new test proposals are first evaluated by using cell culture and HET-CAM models. Approvals for in vivo experiments are postponed and not issued prior to in vitro/in ovo evaluation. Examples are presented of protocols planned for in vivo studies on cell seeded scaffolds, which were refined after in vitro/in ovo evaluations.

Aerosol delivery to the airways of the human respiratory tract, followed by absorption, constitutes an alternative route of administration for compounds unsuitable for delivery by conventional oral and parenteral routes. The target for aerosol drug delivery is the airways epithelium, i.e. tracheal, bronchial, bronchiolar and alveolar cells, which become the site of drug deposition. These epithelial layers also serve as a barrier to the penetration of inhaled material. An in vitro model for aerosol deposition and transport across epithelia in the human airways may be a good predictor of in vivo disposition. The present preliminary studies begin an investigation that blends the dynamics of aerosol delivery and the basis of an in vitro simulated lung model to evaluate the transport properties of a series of molecular weight marker compounds across human-derived bronchiolar epithelial cell monolayers. An Andersen viable cascade impactor was used as a delivery apparatus for the deposition of size-segregated particles onto monolayers of small airway epithelial cells and Calu-3 cells. It was shown that these cell layers can withstand placement in the impactor, and that permeability can be tested subsequent to removal from the impactor.

Determination of the intracerebral pathogenicity index (ICPI) of a virus requires tracking sick animals until death or until the eighth day of the standard observation period. A more humane procedure would be to painlessly kill sick animals, but such intervention in the standard protocol could compromise the rating of the virus. In this paper, a modified scoring system is proposed, whereby humanely killed animals are given a score that, on average, does not alter the ICPI. The variance of an animal's contribution to the optimum modified ICPI is never greater than the variance of its contribution to the standard ICPI.

There are a large number of species of Antarctic lichens, and several studies describing the secondary metabolites present in these lichens, as well as the advances in understanding the chemistry of these metabolites, have been reported. In addition, some derivatives displaying interesting antibacterial effects have been described. The cytotoxic and apoptotic effects of 15 secondary metabolites (depsides, depsidones and usnic acid) obtained from Continental (Chilean) and Antarctic lichens were evaluated in primary cultures of rat hepatocytes. Intracellular lactate dehydrogenase release, caspase 3 activation and DNA fragmentation were measured. In this study, we have evaluated a set of markers associated with pivotal steps in the execution phase of apoptosis, in order to detect compounds with apoptotic effects on hepatocytes before significant necrosis takes place. Flow cytometric analysis of DNA fragmentation revealed an increase in apoptotic nuclei with sub-diploid DNA content after the exposure of hepatocytes to sub-cytotoxic concentrations of the compounds. Among these, salazinic acid, stictic acid and psoromic acid displayed significant apoptotic activities. Divaricatic acid showed only moderate apoptotic effects at sub-cytotoxic concentrations.

At present, we are unable to use much of the data derived from alternative (non-animal) tests for human health risk assessment. This brief Comment outlines why it is plausible that new paradigms could be developed to enable risk assessment to support consumer safety decisions, without the need to generate data in animal tests. The availability of technologies that did not exist 10 years ago makes this new approach possible. The approach is based on the concept that data and information derived from applying existing and new technologies to non-animal models can be interpreted in terms of harm and disease in man. A prerequisite is that similar data and information generated in a clinical setting are available to permit this “translation”. The incorporation of this additional translation step should make it possible to use data and information generated in non-animal models as inputs to risk assessment. The new technologies include genomics, transcriptomics, proteomics and metabonomics. Their application to in vitro and human “models” enables large amounts of data to be generated very quickly. The processing, interpretation and translation of these data need to be supported by powerful informatics capabilities and statistical tools. The use of integrated “systems biology” approaches will further support the interpretation by providing better understanding of the underlying biological complexity and mechanisms of toxicity. Clinical medicine is using the opportunities offered by the new ‘omics’ technologies to advance the understanding of disease. The application of these technologies in clinical medicine will generate massive amounts of data that will need processing and interpretation to allow clinicians to better diagnose disease and understand the patients’ responses to therapeutic interventions. Support from clinical epidemiology will be essential. If these data and information can be made generally accessible in an ethical and legal way, they should also permit the “translation” of experimental non-animal data, so that they can then be used in risk assessment.

INVITOX 2004, the 13th Workshop of the European Society of Toxicology In Vitro, was held on 8–11 September 2004, in Zegrze, Poland, in cooperation with the Scandinavian Society for Cell Toxicology. The workshop was attended by 112 participants from 19 countries. The programme included 11 main sessions and two round table discussions. The lectures of the invited speakers, together with short oral presentations and posters, covered the most important aspects of current research in the field of in vitro toxicology. ECVAM's strategies for the replacement of animal testing for toxic chemicals by alternative test systems were discussed.