Stress and distress in laboratory animals is often inherent and unavoidable. The effect of these factors on the reliability and relevance of experimental data is not sufficiently appreciated. Greater awareness, debate and discussion of this issue are urgently required.
Tissue engineered full-thickness human skin substitutes have various applications in the clinic and in the laboratory, such as in the treatment of burns or deep skin defects, and as reconstructed human skin models in the safety testing of drugs and cosmetics and in the fundamental study of skin biology and pathology. So far, different approaches have been proposed for the generation of reconstructed skin, each with its own advantages and disadvantages. Here, the classic tissue engineering approach, based on cell-seeded
polymeric scaffolds, is compared with the less-studied cell self-assembly approach, where the cells are coaxed to synthesise their own extracellular matrix (ECM). The resulting full-thickness human skin substitutes were analysed by means of histological and immunohistochemical analyses. It was found that both the scaffold-free and the scaffold-based skin equivalents successfully mimicked the functionality and morphology of native skin, with complete epidermal differentiation (as determined by the expression of filaggrin), the presence of a continuous basement membrane expressing collagen VII, and new ECM deposition by dermal fibroblasts. On the other hand, the scaffold-free model had a thicker epidermis and a significantly higher number of Ki67-positive proliferative cells, indicating a higher capacity for self-renewal, as compared to the scaffold-based model.
Statistical sample size calculation is essential when planning animal experiments in basic medical research. Usually, such trials involve the testing of multiple hypotheses, and interpreting them in a confirmative manner would require the appropriate adjustment of the Type 1 error. This has to be taken into account as early as possible during sample size estimation — otherwise, all the results obtained would be
exploratory, i.e. without cogency. In this paper, the concept of gatekeeping is introduced, along with alternative approaches for Type 1 error adjustment. The application of gatekeeping to the calculation of sample size is demonstrated by using data sets from case studies. Overall, the evaluation of these examples showed that gatekeeping is able to keep the required number of animals comparatively small. In contrast to exploratory planning, which led to the lowest sample sizes, gatekeeping suggested a mean increase of 12% in sample size, while conservative Bonferroni adjustment raised the sample size by 34% on average. Gatekeeping is a prominent strategy for handling the multiple testing problem, and has been proven to keep the required sample sizes in animal studies comparatively low. Therefore, it is a suitable approach to a compromise between the Three Rs principle of reduction and the appropriate handling of the multiplicity issue in animal trials with a confirmative focus.
More and more countries are lining up to follow the EU’s approach and implement a full ban on the sale of cosmetics that have been tested on animals, which has been the case in the EU since 2013. Besides animal welfare considerations, the need for mutual acceptance of data (MAD) and harmonisation of the global market have made the move toward non-animal testing a desirable general trend for countries
worldwide. Over the last 10 years, the concept of alternative methods has been gradually developing in China. This has seen the harmonisation of relevant legislation, the organisation of various theoretical and hands-on training sessions, the exploration of method validation, the adoption of internationally recognised methods, the propagation of alternative testing standards, and an in-depth investigation into the potential use of in vitro methods in the biosciences. There are barriers to this progress, including the demand for a completely new infrastructure, the need to build technology capability, the requirement for a national standardisation system formed through international co-operation, and the lack of technical assistance to facilitate self-innovation. China is now increasing speed in harmonising its approach to the use of non-animal alternatives, accelerating technological development and attempting to incorporate
non-animal, in vitro, testing methods into the national regulatory system.