Repigmentation of Human Vitiligo Skin by NBUVB Is Controlled by Transcription of GLI1 and Activation of the β-Catenin Pathway in the Hair Follicle Bulge Stem Cells

Vitiligo repigmentation is a complex process in which the melanocyte-depleted interfollicular epidermis is repopulated by melanocyte precursors from hair follicle bulge that proliferate, migrate, and differentiate into mature melanocytes on their way to the epidermis. The strongest stimulus for vitiligo repigmentation is narrowband UVB (NBUVB), but how the hair follicle melanocyte precursors are activated by UV light has not been extensively studied. To better understand this process, we developed an application that combined laser capture microdissection and subsequent whole transcriptome RNA sequencing of hair follicle bulge melanocyte precursors and compared their gene signatures to that of regenerated mature epidermal melanocytes from NBUVB-treated vitiligo skin. Using this strategy, we found up-regulation of TNC, GJB6, and THBS1 in the hair follicle bulge melanocytes and of TYR in the epidermal melanocytes of the NBUVB-treated vitiligo skin. We validated these results by quantitative real-time-PCR using NBUVB-treated vitiligo skin and untreated normal skin. We also identified that GLI1, a candidate stem cell-associated gene, is significantly up-regulated in the melanocytes captured from NBUVB-treated vitiligo bulge compared with untreated vitiligo bulge. These signals are potential key players in the activation of bulge melanocyte precursors during vitiligo repigmentation.