Effects of gamma rays on the regeneration of murine hair follicles in the natural hair cycle

Abstract

Purpose: This review evaluates the effects of γ-rays on the regeneration of murine hair follicles in the natural hair cycle. A series of studies were performed to investigate this issue, in which the whole bodies of C57BL/10JHir mice in the 1st telogen phase of the hair cycle were irradiated with γ-rays.

Results: The dermis of the irradiated skin showed a decrease in hair follicle density and induction of curved hair follicles along with the presence of white hairs and hypopigmented hair bulbs in the 2nd and 3rd anagen phases. An increased frequency of hypopigmented hair bulbs was still observed in the later hair cycle at postnatal day 200. There was no significant difference in the number of stem cells in the hair bulge region between control and irradiated skin.

Conclusions: These results show that the effects of γ-rays on the pigmentation of murine hair follicles are persistently carried over to later hair cycles, although those on the number and structure of hair follicles appear to be hidden by the effects of aging. Our findings may be important for understanding the mechanisms of the actions of stem cells on hair regeneration in connection with age-related phenotypes.

Keywords:

• Bulge
• γ-rays
• hair
• keratinocyte
• melanocyte
• stem cell

Acknowledgements

The author especially thanks Dr Tomohisa Hirobe for the illustration of Figure 1 and for comments on the manuscript. The author also thanks Mrs Yoshie Ishihara and Mrs Sonoe Inoue for their technical assistance, Dr Bing Wang for comments on survival and on body weight, and the members of The Functional and Molecular Imaging Team, Department of Molecular Imaging and Theranostics and the members of the Laboratory Animal Science Section of NIRS/QST for their support.

Disclosure statement

No potential conflict of interest was reported by the author.

Notes on contributor

Kimihiko Sugaya is a Principal Researcher of NIRS/QST. PhD (1995): The Graduate University for Advanced Studies (National Institute of Genetics), Japan. JST (Japan Science and Technology Agency) overseas research fellow (1998?2000): The Sir William Dunn School of Pathology, University of Oxford, UK.