ABSTRACT
Building up a three-dimensional (3D) human skin tissue was initially stimulated by
the idea of an improved healing of severe wounds and, in fact, skin equivalents for
transplantation purposes are now commercially available. Importantly, human skin
equivalents are also used in the risk assessment of chemicals and safety tests of
cosmetics. The Organisation of Economic Cooperation and Development (OECD)
has adopted a test guideline (TG) for the assessment of skin corrosion [TG 431; (1)],
which is based on reconstructed human epidermis (RHE). TG 431 also defines
quality parameters for RHE which are important for alternative uses such as risk
assessment linked to the absorption of chemicals and drugs through the skin and in
the development of dermatological and topical antirheumatic drugs. The OECD
technical guidance document 28 [TGD 28, (2)] that accompanies TG 428 (3) states
that skin equivalents can be used for in vitro assays of percutaneous absorption,
given that the obtained results are equivalent to those obtained with the accepted
matrices of human and animal skin. Thus, in principle, relevant aspects of skin
toxicity can be studied using the same matrix. The various aspects of in vitro tests
based on skin equivalents are described below.
