An advanced 3D skin model developed at King's College London (KCL) may reduce the need for animal models in cosmetic testing.
The model uses stem cell derived keratinocytes, the primary cell type of the epidermis, the outermost layer of skin. Over time, they were able to build up the cells into a 3D structure called a human epidermal equivalent, or HEE, that both physically and functionally resembles the natural permeable barrier of the skin.
HEE models are widely used to test skin disorders, drugs, and cosmetics in the laboratory. However, previous models have been limited by two key aspects: development and scalability. First, they were not able to engineer a functional permeability barrier. Second, stem cells generated from a biopsy sample of epidermis could only produce a limited number of HEEs; furthermore, they may contain mutations that could affect experimental results.
'Our new method can be used to grow much greater quantities of lab-grown human epidermal equivalents, and thus could be scaled up for commercial testing of drugs and cosmetics', explained Dr Dusko Ilic, head of the KCL research team.
The major function of the skin is to form a permeable barrier against the external environment, against pathogens, heat and water loss. Skin diseases such as atopic dermatitis (also known as eczema) and Ichthyoses (characterised by thickened flaky skin) affect the permeability of the skin, ranging from mild to severe. These skin diseases and related disorders are commonly tested using animal models. Although similar diseases are also present is some animals, there are no suitable in vitro models for such diseases. The new HEE model overcomes this limitation.
This research could reduce the amount of animal models that are currently used in research. Research and toxicology director of the The Humane Society International, Troy Seidle explained, 'this new human skin model is superior scientifically to killing rabbits, pigs, rats or other animals for their skin and hoping that research findings will be applicable to people - which they often aren't, due to species differences in skin permeability, immunology, and other factors'.
The market for advanced, cost-effective in vitro skin models like the KCL model are expected to increase as regulations become stricter on the import and sale of cosmetics with ingredients tested on animals. Lead author Anastasia Petrova explained in the publication that 'HEEs with a functional permeability barrier generated completely in vitro from either [human embryonic or iPS, induced pluripotent stem cells], as described here, might present the best available answer'.