To induce SCF secretion from fibroblasts and simulate the condition of light stimulation, UVB was used to complete the test. This test was performed according to the method, with some modifications, described by Shin et al. . Fibroblasts with or without previous siRNA transfection were cultured in a 6-well plate. Before UV exposure, the medium was replaced by PBS during that time. UVB exposure was performed using Ultraviolet Crosslinkers CL-1000 (UVP, Upland, CA, USA) with UVB radiation (302 nm) at a nontoxic dosage of 5 mJ/cm2 3 times at intervals of 5 h. After UVB treatment and culturing for 24 h, the medium was collected into the conditioned medium and used for treating melanocytes previously cultured in the 6-well plate for 24 h. Experimental cells were harvested for subsequent testing.