Contribution of Human Hair in Solar UV Transmission in Skin: Implications for Melanoma Development
Melanoma is the deadliest type of skin cancer with its prevalence on the rise. Recently, the melanocyte stem cells in hair follicles have been identified as the possible origin of melanoma upon exposure to ultraviolet radiation (UVR) through skin. It is hypothesized that colourless vellus hair (predominant in childhood) can serve as an alternative pathway in transmitting these ultraviolet (UV) photons to the stem cells. To investigate this, we have used the CRAIC microspectrophotometer to investigate the optical properties of ‘vellus-like’ hairs and terminal hairs of different colours using UV–VIS–NIR light sources. It was found that the average attenuation coefficient of ‘vellus-like’ hair is significantly lower than that of terminal hair in the UVA (p < 0.0001) and UVB (p < 0.001) wavelength ranges. Next, the optical properties of hairs are applied to simulations for examining their influence on UV transmission into the skin. The results show that the presence of vellus hair would increase the solar UV transmission to the melanocyte stem cell layer significantly. The findings explain why children are particularly vulnerable to sun exposure and the positive correlation found between the incidence of melanoma in adults’ bodies and the number of vellus hairs in these areas.
KeywordsTissue optics Melanoma Skin cancer Melanocyte stem cells Attenuation coefficient Monte Carlo simulation Vellus hair Medulla Microspectrophotometry Ultraviolet radiation
The authors would like to acknowledge Soochow University’s Centre of Nuclear Environmental Chemistry in People’s Republic of China for providing the access to and supervision of the use of the CRAIC Microspectrophotometer. In addition, the authors would like to express thanks to Robin Hankin in Auckland University of Technology, New Zealand for providing expert advice on statistical analysis.
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