Protective Effect of Rhus Semialata M. extract on Epidermal Stem Cells against UV Irradiation

Human epidermal stem cells(ESCs) residing in the basement membrane of the skin have an important role in maintenance of skin homeostasis of epidermal layer. Although, ESCs provide new cells to repair damaged tissue in response to tissue injury, subsets of stem cells remain in the quiescent state protected from differentiation and senescence for prolonged survivals. In this perspective, the stem cell niche, which is specific microenvironment composed of niche cells and an extracellular matrix(ECM), supplies the relevant signal to save stem cells from microenvironmental damages. The expression of stemness marker on the surface of ESCs contributes to the attachment on their ECM of the basement membrane, which lead to growth potential and apoptotic resistance against environmental stimuli. In this study, we observed that UV irradiation, a major factor of environmental stimuli, reduced the expression of α2, β1 and α6 integrin in ESCs. Rhus Semialata M extract(RSE) showed inhibitory effect on the UVB-induced reduction of integrin expression. Furthermore, RSE could upregulate the expression of Col-IV and Laminin, which contribute to the attachment of ESCs. These results indicated that RSE could be a potent ingredient for the protection of ESCs from UV irradiation by increasing the expression of integrin and substrate ECM components at their niche.