The influence of retinol concentration in liquid crystal formula on epidermal growth factor, interleukin-6 and transglutaminase-1 mRNA expression in the epidermis.

Abstract

Topical retinol application effectively reduces the effects of photoaging and improves skin condition, e.g. influences the process of keratinization of the epidermis, which improves stratum corneum structure and reduces transepidermal water loss. However, cosmetics use lower concentrations of retinol, which has been associated with emerging hypersensitivity reactions as well as redness and irritation of the skin. The question arises whether the vehicle used in the cosmetic may be important in stimulating the inflammatory reaction in the skin and if the concentration of retinol used could significantly affects the growth of epidermal cells. The aim of this study was to evaluate the effects of different concentrations of liquid crystal retinol (0.15%, 0.3% and 0.5%) on the clinical and histological characteristics of a reconstructed epidermis skin model. It also compares the effectiveness of 0.3% retinol formula in liquid crystal to that in lipid. The study used reconstructed human epidermis tissue containing normal human keratinocytes. Four original formulas containing retinol were tested: 0.15%, 0.3% and 0.5% with a liquid crystal base, and 0.3% with a lipid base. Interleukin 6 (IL-6), transglutaminase-1 (TGM1), and epidermal growth factor (EGF) mRNA expression was measured expression of the skin-equivalent tissue for 10 days of exposure. Histopathological analysis and mRNA quantification were performed. Gene expression was analyzed by total mRNA extraction. All liquid crystal formulas induced higher EGF mRNA expression than lipid base formula. IL-6 expression did not differ significantly from the DPBS reference values. Interestingly, TGM1 expression was found to increase together with increasing retinol concentration (0.15%, 0.3%, 0.5%). Histological examination revealed changes in epidermal structure, mainly hyperkeratinization of the stratum corneum. Our results support the hypothesis liquid crystal formula might be regarded as more beneficial since it inducess less pro-inflammatory action manifested by lowered expression IL-6. In addition, EGF expression was found to correlate significantly with the retinol concentration of the liquid crystal formula: 0.5% > 0.3% > 0.15% (P < 0.05). Lower concentrations may increase TGM1 expression, thus enhancing the formation of a protective layer of cornified envelope.