Silencing Stem Cell Factor Gene in Fibroblasts to Regulate Paracrine Factor Productions and Enhance c-Kit Expression in Melanocytes on Melanogenesis

Melanogenesis is a complex physiological mechanism involving various paracrine factors. Skin cells such as keratinocytes, fibroblasts, and melanocytes communicate with one another through secreted regulators, thereby regulating the melanocytes' bio-functions. The stem cell factor (SCF) is a paracrine factor produced by fibroblasts, and its receptor, c-kit, is expressed on melanocytes. Binding of SCF to c-kit activates autophosphorylation and tyrosine kinase to switch on its signal transmission. SCF inhibition does not suppress fibroblast proliferation in MTT assay, and SCF silencing induced mRNA expressions of paracrine factor genes, HGF, NRG-1, and CRH in qPCR results. Following UVB stimulation, gene expressions of HGF, NRG, and CRH were higher than homeostasis; in particular, HGF exhibited the highest correlation with SCF variations. We detected fibroblasts regulated SCF in an autocrine-dependent manner, and the conditioned medium obtained from fibroblast culture was applied to treat melanocytes. Melanogenesis-related genes, tyrosinase and pmel17, were upregulated under conditioned mediums with SCF silencing and exposed to UVB treatments. Melanin quantities in the melanocytes had clearly increased in the pigment content assay. In conclusion, SCF silencing causes variations in both fibroblast paracrine factors and melanocyte melanogenesis, and the differences in gene expressions were observed following UVB exposure.