Characterisation of Skin Barrier Function Using Bioengineering and Biophysical Techniques

Abstract

Purpose: To characterise skin barrier function in vivo at two distinct anatomic sites using minimally invasive bioengineering and biophysical tools.Methods: In healthy human volunteers, the quantities of stratum corneum (SC) per unit area of skin on the forearm and forehead were quantified by gravimetric and imaging techniques. Organisation of the SC intercellular lipids was evaluated as a function of position using attenuated total reflectance infrared spectroscopy (ATR-IR). The constituents of natural moisturising factor (NMF) were extracted from tape-stripped samples of the SC and by reverse iontophoresis; 21 components were identified and quantified by liquid chromatography with mass spectrometric detection.Results: SC was quantified more accurately by imaging and was significantly thinner on the forehead than on the forearm. Intercellular lipids were more disordered near the skin surface at both sites; however, throughout forearm SC, the lipids were substantially better organised than those in the forehead. Compositionally, the NMF from forearm and forehead SC was similar, but the total amount extractable from the forehead was smaller.Conclusion: Taken together, the bioengineering and biophysical techniques employed demonstrate, in a complementary, objective and quantitative fashion, that SC barrier function on the forehead is less competent than that on the forearm.Keywords: stratum corneum, skin barrier function natural moisturizing factor (NMF), reverse iontophoresis, infrared spectroscopy 3 Abbreviations IntroductionNatural moisturizing factor (NMF) is a collection of water-soluble, low molecular weight compounds found in the stratum corneum (SC). Functionally, it allows the SC to retain water against the dehydrating action of external environment and thus plays a key role in skin hydration (1). NMF is composed primarily of free amino acids (AAs) and amino acid derivatives that are derived from filaggrin. Filaggrin is synthesized from profilaggrin, an approximately 500-kDa insoluble protein, consisting of 10 to 12 repeating filaggrin units (2,3). During the transition of the mature granular cell into a corneocyte, rapid dephosphorylation of pro-filaggrin occurs, yielding filaggrin (3). As corneocytes proceed upwards through the SC, deiminiation and complete proteolysis of filaggrin yields the main components of NMF, specifically, (a) free hygroscopic amino acids (mainly Ser, Ala, Arg, Gly, Pro and His (4)), and (b) the following amino acid derivatives: pyrollidone carboxylic acid (PCA) formed by cyclisation of glutamine (5), trans-urocanic acid (UCA) synthesised from histidine (3), and ornithine (Orn) and citruline (Cit), which are degradation products of arginine (6).Presently, a filaggrin mutation is considered to be the strongest genetic risk factor for atopic dermatitis (AD) (7-10). As a result of this mutation, lower levels of NMF are generated in atopic skin and this is thought to contribute to an impaired barrier function (4, 11). Furthermore, a reduced NMF level has also been reported i...

The effect of photodamage on the female Caucasian facial stratum corneum corneome using mass spectrometry‐based proteomics

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The tissue viability imaging system—Suitable method for discovering minimal skin changes in occupational screenings? Results of a cross‐sectional field study

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