Progress in the analysis of Stratum corneum ceramides

The stratum corneum with its unique structure of corneocytes and intercellular lipid lamellae enables a protection of human and other mammalian skin against transepidermal water loss and harmful substances from the environment. Among these lipids, ceramides play a key role. Several skin disorders such as psoriasis, atopic dermatitis and others show a disturbed barrier function, which can be linked in part to a changed ceramide pattern. Research in dermatology and cosmetic industry requires the use of analytical methods to characterize ceramides. However, the amazing variability of ceramide structures found in stratum corneum makes their analysis a challenge. This is to our knowledge the first review that deals with ceramide analysis. It is focused on stratum corneum ceramides which show much more complexity than intracellular ceramides known to be signal transducers. After a short summary of lipid extraction methods, we discuss the following set of methods: thin-layer chromatography, gas chromatography, HPLC, LC/MS, mass spectrometry, NMR spectroscopy, vibrational spectroscopy, and X-ray diffraction. It will be lined out which information about structure, concentration or physical state is available by means of each particular method. Although the focus is clearly on stratum corneum ceramides, some methods of general skin lipid analysis and structure analysis of sphingolipids are also discussed when appropriate.