Investigation of the molecular signature of greying hair shafts

Objective Hair greying (i.e. canitie) is a physiological process occurring with the loss of melanin production and deposition within the hair shafts. Many studies reported the oxidation as the main biological process underlying this defect of pigmentation. Even though the overall appearance and biomechanical properties of hairs are reported to be altered with greying, there is a lack of information about molecular modifications occurring in grey hair shafts. The aim of this study was thus to investigate the molecular signature and associated changes occurring in greying hair shafts by confocal Raman microspectroscopy. Methods This study was conducted on pigmented, intermediate (i.e. grey) and unpigmented hairs taken from 29 volunteers. Confocal Raman microspectroscopy measurements were acquired directly on hair shafts. Results Automatic classification of Raman spectra revealed 5 groups displaying significant differences. Hence, the analysis of the molecular signature highlighted the existence of 3 sub-groups within grey hair: light, medium and dark intermediate. Among molecular markers altered in the course of greying, this study identified for the first time a gradual modification of lipid conformation (trans/gauche ratio) and protein secondary structure (alpha-helix/beta-sheet ratio), referring respectively to an alteration of barrier function and biomechanical properties of greying hair. Conclusion This study thus reports for the first time a highly specific molecular signature as well as molecular modifications within grey hair shaft.

Automated summary

This study used confocal Raman microspectroscopy to investigate the molecular changes occurring in greying hair shafts. Results showed the existence of 3 sub-groups within grey hair and identified a gradual modification of lipid conformation and protein secondary structure as molecular markers in greying hair. This study reports for the first time a highly specific molecular signature within grey hair shaft.