title: Visible red light enhances physiological anagen entry in vivo and has direct and indirect stimulative effects in vitro.
abstract: OBJECTIVE
  Hair follicles are located at the interface of the external and internal environments and their cycling has been shown to be regulated by intra- and extra-follicular factors. The aim of this study is to examine whether or how hair follicles respond to visible light.
  
  
  METHODS
  We examined the effect of 3 mW red (630 nm, 1 J/cm(2)), 2 mW green (522 nm, 1 J/cm(2)), and 2 mW blue light (463 nm, 1 J/cm(2)) on telogen in mice for 3 weeks. The photobiologic effects of red light on cell proliferation of outer root sheath keratinocytes and dermal papilla cells were studied in vitro.
  
  
  RESULTS
  We found that red light accelerated anagen entry faster than green and blue light in mice. Red light irradiation stimulated the proliferation of both outer root sheath keratinocytes and dermal papilla cells in a dose-dependent manner by promoting cell cycle progression. This stimulative effect was mediated via extracellular signal-regulated kinase phosphorylation in both cells. In a co-culture condition, dermal papilla cells irradiated by red light further enhanced keratinocyte proliferation, suggesting enhanced epithelial-mesenchymal interaction. In search for factors that mediated this paracrine effect, we found fibroblast growth factor 7 was upregulated in both mRNA and protein levels. The stimulative paracrine effect on keratinocytes was significantly inhibited by neutralizing antibody against fibroblast growth factor 7.
  
  
  CONCLUSIONS
  These results suggest that hair follicles respond to visible light in vivo. Red light may promote physiological telogen to anagen transition by directly stimulating outer root sheath keratinocytes and indirectly by enhancing epithelial-mesenchymal interaction in vitro.
authors.affiliation: Department of Dermatology, National Taiwan University Hospital and National Taiwan University College of Medicine, 7 Chung-Shan South Road, Taipei, 100, Taiwan.
authors.forename: Yi-Shuan
authors.initials: YS
authors.lastname: Sheen
authors.forename: Sabrina Mai-Yi
authors.initials: SM
authors.lastname: Fan
authors.forename: Chih-Chieh
authors.initials: CC
authors.lastname: Chan
authors.forename: Yueh-Feng
authors.initials: YF
authors.lastname: Wu
authors.forename: Shiou-Hwa
authors.initials: SH
authors.lastname: Jee
authors.forename: Sung-Jan
authors.initials: SJ
authors.lastname: Lin
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D049109:Cell Proliferation / Q000528:radiation effects; D020405:Dermis / Q000378:metabolism / Q000528:radiation effects; D005260:Female; D051523:Fibroblast Growth Factor 7 / Q000378:metabolism; D006197:Hair / Q000254:growth & development / Q000528:radiation effects; D018859:Hair Follicle / Q000502:physiology / Q000528:radiation effects*; D066298:In Vitro Techniques; D015603:Keratinocytes / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D051379:Mice; D008810:Mice, Inbred C57BL; D011897:Random Allocation
chemical_list: D015415:Biomarkers; C496454:Fgf7 protein, mouse; D051523:Fibroblast Growth Factor 7
keywords: FGF7; dermal papilla cells; hair cycle; outer root sheath keratinocytes