Alternative test models for skin ageing research.

Increasing ethical concerns regarding animal experimentation have led to the development of various alternative methods based on the 3Rs (Refinement, Reduction and Replacement), first described by Russell and Burch in 1959. Cosmetic research and skin ageing research are particularly susceptible to concerns related to animal testing. In addition to animal welfare reasons, there are scientific and economic reasons to reduce and avoid animal experiments. Importantly, animal experiments may not reflect findings in humans mainly because of the differences in architectures and immune responses between animal skin and human skin. Here, we review the shift from animal testing to the development and application of alternative non-animal-based methods and the necessity and benefits of this shift. Some specific alternatives to animal models are discussed, including biochemical approaches, 2-dimensional and 3-dimensional cell cultures and volunteer studies, as well as future directions, including genome-based research and the development of in silico computer simulations of skin models. Among the in vitro methods, 3-dimensional reconstructed skin models are highly popular and useful alternatives to animal models however still have many limitations. With careful selection and skilful handling, these alternative methods will become indispensable for modern dermatology and skin ageing research.