A mechanism of melanogenesis mediated by E-cadherin downregulation and its involvement in solar lentigines

BackgroundIntensive studies have revealed pleiotropic melanocytic factors for age spot formation. In particular, dysfunctional keratinocyte differentiation is thought to be an upstream cause of age spot formation. Although keratinocyte differentiation is mediated by a cell-cell contact factor, E-cadherin, its involvement in age spots remains unknown. To find the origin of age spots and an integrated solution, we focused on E-cadherin. MethodsImmunofluorescent staining with cutaneous tissues and cultured cells was performed. Keratinocytes treated with siRNAs were cocultured with melanocytes. With the supernatants of the keratinocyte culture, secretion factors were identified using proteomic analysis. For the activity of melanogenesis and the ingredient screening, a quantitative PCR was performed. For the behavioral analysis of melanocytes, time-lapse imaging of melanocytes was done by confocal laser scanning microscopy. ResultsIn age spots, E-cadherin expression in the epidermis was downregulated, suggesting that E-cadherin is implicated in age spot formation. E-cadherin knockdown (E-cad-KD) keratinocytes not only promoted the secretion of melanocytic/inflammatory factors, but also increased melanogenesis by upregulating the expression of melanogenesis factors. Furthermore, live imaging showed E-cadherin downregulation detained melanocyte dynamics and accelerated melanin-uptake. Finally, we identified Rosa multiflora fruit extract as a solution for upregulating E-cadherin in keratinocytes. ConclusionOur findings showed that E-cadherin downregulation triggers various downstream melanocytic processes such as secretion of melanocytic factors and melanogenesis. Additionally, we showed that Rosa multiflora fruit extract upregulates E-cadherin expression in keratinocytes.