Wnt inhibitory factor (WIF)-1 promotes melanogenesis in normal human melanocytes.

Abstract

Wnt signaling plays a role in the differentiation as well as the development of

melanocytes. Using a microarray analysis, hyperpigmentary skin of melasma

expressed high levels of Wnt inhibitory factor-1 (WIF-1) compared with

perilesional normal skin. In this study, the expression and functional roles of

WIF-1 on melanocytes were investigated. WIF-1 was expressed both in the

melanocytes of normal human skin and in cultured melanocytes. The upregulation of

WIF-1 on cultured normal human melanocytes significantly induced expressions of

MITF and tyrosinase, which were associated with increased melanin content and

tyrosinase activity. Consistent with the stimulatory effect of WIF-1, WIF-1 siRNA

reduced melanogenesis in the cells. Moreover, WIF-1 increases pigmentation in

melanocytes co-cultured with WIF-1-overexpressed fibroblasts and of

organ-cultured human skin. These findings suggest that melanocytes express WIF-1

constitutively in vivo and in vitro and that WIF-1 promotes melanogenesis in

normal human melanocytes.