Visible red light enhances physiological anagen entry in vivo and has direct and indirect stimulative effects in vitro

• Published in: Lasers in surgery and medicine Vol. 47; no. 1; pp. 50 - 59
• Main Authors: Sheen, Yi-Shuan, Fan, Sabrina Mai-Yi, Chan, Chih-Chieh, Wu, Yueh-Feng, Jee, Shiou-Hwa, Lin, Sung-Jan
• Format: Journal Article
• Language: English
• Published: United States Blackwell Publishing Ltd 01.01.2015; Wiley Subscription Services, Inc
• Subjects: Animals; Biomarkers - metabolism; Cell Proliferation - radiation effects; dermal papilla cells; Dermis - metabolism; Dermis - radiation effects; Female; FGF7; Fibroblast Growth Factor 7 - metabolism; Hair - growth & development; Hair - radiation effects; hair cycle; Hair Follicle - physiology; Hair Follicle - radiation effects; In Vitro Techniques; Keratinocytes - metabolism; Keratinocytes - radiation effects; Light; Mice; Mice, Inbred C57BL; outer root sheath keratinocytes; Random Allocation; outer root sheath keratinocytes; FGF7; hair cycle; dermal papilla cells
• ISSN: 0196-8092; 1096-9101
• DOI: 10.1002/lsm.22316

Background and Objectives 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. Study Design/Materials and Methods We examined the effect of 3 mW red (630 nm, 1 J/cm2), 2 mW green (522 nm, 1 J/cm2), and 2 mW blue light (463 nm, 1 J/cm2) 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. Lasers Surg. Med. 47:50–59, 2015. © 2014 Wiley Periodicals, Inc.