Various wavelengths of light-emitting diode light regulate the proliferation of human dermal papilla cells and hair follicles via Wnt/β-catenin and the extracellular signal-regulated kinase pathways

Background: The human dermal papilla cells (hDPCs) play an important role in regulation of hair cycling and growth. Objective: The aim of this study was to investigate the effect of different wavelengths of light-emitting diode (LED) irradiation on the proliferation of cultured hDPCs and on the growth of human hair follicles (HFs) in vitro. Methods: We examined the effect of LED irradiation on Wnt/β-catenin signaling and mitogen-activated protein kinase (MAPK) pathways in hDPCs. Anagen HFs were cultured with LED irradiation and elongation of each hair shaft was measured. Results: The most potent wavelength in promoting the hDPC proliferation is 660 nm and 830 nm promoted hDPC proliferation to a lesser extent than 660 nm. Various wavelengths significantly increased β-catenin, Axin2, Wnt3a, Wnt5a and Wnt10b mRNA expression. LED irradiation significantly increased β-catenin and cyclin D expression, and the phosphorylation of MAPK and extracellular signal-regulated kinase (ERK). HFs irradiated with 415 nm and 660 nm grew longer than control. Conclusion: Our result suggests that LED has a potential to stimulate hDPC proliferation via the activation of Wnt/β-catenin signaling and ERK pathway. To our best knowledge, this is the first report which investigated that the effect of various wavelengths of LED on hDPC proliferation and the underlying mechanisms.