For screening of skin-whitening ingredients that modulate inhibition of melanogenesis, tyrosinase promoter-based assay using a three-dimensional (3D) spheroid culture technique is a beneficial tool to improve the accuracy of raw material screening in cosmetics through mimicking of the in vivo microenvironment. Although the advantages of high-throughput screening (HTS) are widely known, there has been little focus on specific cell-based promoter assays for HTS in identifying skin-whitening ingredients that inhibit accumulation of melanin. The aim of this study was therefore to develop a large-scale compatible assay through pTyr-EGFP, an enhanced green fluorescent protein (EGFP)-based tyrosinase-specific promoter, to seek potential melanogenesis inhibitors for cosmetic use. Herein, a stably transfected human melanoma cell line expressing EGFP under the control of a 2.2-kb fragment derived from the tyrosinase gene was generated. Spontaneous induction of the tyrosinase promoter by 3D spheroid culture resulted in increased expression of EGFP, providing a significant correlation with the tyrosinase mRNA level, and subsequent inhibition of tyrosinase activity. Importantly, the pTyr-EGFP system provided successful tracking of the changes in the live image and real-time monitoring. Thus tyrosinase promoter-based fluorescent assay using a 3D spheroid culture can be useful as a screening system for exploring the efficiency of anti-melanogenesis ingredients.Key words three-dimensional spheroid culture; tyrosinase promoter; fluorescent assay; high-throughput screening (HTS)Created with the purpose of mimicking in vivo environments, three-dimensional (3D) cultures have been shown to differ remarkably in the optimal cell growth, morphology, and differentiation compared with two-dimensional (2D) adherent cultures. Moreover, 3D cultures like spheroid cultures may come closer to the physiological interactions with neighboring cells and the extracellular matrix, providing valuable advanced tools for the evaluation of effectiveness. Particularly, therapeutic screening in 3D spheroid culture offers high potential for discovering drugs and biological relevances.
1)Recently, a biosensor was developed using 3D spheroid cultures and bioelectronically characterized by measuring physiological alterations after drug treatment. [2][3][4] In the cosmetic field, such large-scale screens often utilize the enhanced green fluorescent protein (EGFP) gene as a reporter to allow sensitive, rapid, and convenient quantitation of gene expression.
5)Although using 2D adherent cultures of melanin-producing cells is a useful method for the screening of skin-whitening ingredients, its utility is limited due to the time-consuming, laborious process, which only results in endpoint, static data with low sensitivity which requires multistep cell viability 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for quantification. 6) We therefore developed a method to automatically monitor the activity of a tyrosinase promoter cloned upstream ...