| Summary: | Abstract Background The Sophora japonica extracts contain flavonol triglycoside, isoflavonol, coumarone chromone, saponin, triterpene glucoside, phospholipids, alkaloids, amino acids, polysaccharides, and fatty acids. These components have physiological effects such as anti-infertility and anti-cancer activities. This study investigated the regulation of keratinocyte differentiation upon treatment with the S. japonica extracts in keratinocyte and the molecular cell biological mechanism involved. Methods To determine whether the S. japonica extracts or troxerutin, which is its main component, regulates keratinocyte differentiation, quantitative real-time polymerase chain reaction (qRT-PCR) was performed on keratinocyte differentiation markers such as keratin 1 (K1), keratin 10 (K10), involucrin, and filaggrin after treatment with the S. japonica extracts. miR-181a knockdown confirmed that keratinocyte differentiation was regulated by increased miR-181a expression upon treatment with the S. japonica extracts or troxerutin. Results The expression of keratinocyte differentiation markers such as K1, K10, involucrin, and filaggrin increased upon treatment with the S. japonica extracts and troxerutin. Furthermore, miR-181a expression, which is known to increase during keratinocyte differentiation, increased upon treatment with the S. japonica extracts and troxerutin. When miR-181a was knocked down, the increased expression of keratinocyte differentiation markers upon treatment with the S. japonica extracts and troxerutin decreased again. Finally, it was confirmed that miR-181a directly regulated and reduced the expression of Notch2, which reduces keratinocyte differentiation, and that the decrease in Notch2 expression by miR-181a regulated keratinocyte differentiation. Conclusions These results suggest that the S. japonica extracts or troxerutin accelerates keratinocyte differentiation through miR-181a. This accelerated keratinocyte differentiation was confirmed to have resulted from the regulation of Notch2 expression by miR-181a. The results of this study provide an opportunity to confirm the molecular cell biological mechanism of S. japonica extracts or troxerutin on skin keratinization, and we expected that this study contribute to develop a moisturizing cosmetic material that can strengthen the skin barrier through regulating keratinocyte differentiation.
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