Human hair greying is linked to a specific depletion of hair follicle melanocytes affecting both the bulb and the outer root sheath

• Published in: British journal of dermatology (1951) Vol. 150; no. 3; pp. 435 - 443
• Main Authors: Commo, S., Gaillard, O., Bernard, B.A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.03.2004; Blackwell; Oxford University Press
• Subjects: Adult; Aged; Aging - physiology; Biological and medical sciences; Cell Division - physiology; Dermatology; Female; Hair Color - physiology; hair colour; Hair Follicle - cytology; Hair Follicle - enzymology; Humans; Immunohistochemistry - methods; Keratinocytes - physiology; Male; Medical sciences; Melanins - analysis; Melanocytes - physiology; Membrane Glycoproteins; Middle Aged; Monophenol Monooxygenase - analysis; Oxidoreductases; pigmentation; Proteins - analysis; Sebaceous Glands - cytology; stem cells; tyrosinase; tyrosinase-related protein 1; Human; stem cells; Dermatology; Stem cell; tyrosinase-related protein 1; Color; Melanocyte; Hair follicle; tyrosinase; Pigmentation; Sheath; Protein; Hair (head); hair colour
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1046/j.1365-2133.2004.05787.x

Summary Background  Although hair greying is a very common phenomenon characterized by loss of pigment in the hair shaft, the events that cause and control natural hair whitening with age in humans are still unclear. Objectives  To decipher the origin of natural hair whitening. Methods  Human hair melanocytes were immunohistochemically characterized at different stages of whitening. Results  Loss of hair shaft melanin was found to be associated with a decrease in both bulb melanin content and bulb melanocyte population. Although few melanocytes were present in the bulbs of grey hair, they still expressed tyrosinase and tyrosinase‐related protein‐1, synthesized and transferred melanins to cortical keratinocytes as seen by the presence of melanin granules. In white hair bulbs, no melanocytes could be detected either with pMel‐17 or vimentin labelling. Pigmented hair follicles are known to contain inactive melanocytes in the outer root sheath (ORS), and grey and white hairs were also found to contain some of these quiescent melanocytes. However, their population was decreased compared with pigmented hair follicles, ranging from small to nil. This depletion of melanocytes in the different areas of white hairs was detected throughout the hair cycle, namely at telogen and early anagen stages. In contrast, the infundibulum and sebaceous gland of both pigmented and white hairs showed a similar distribution of melanocytes. Furthermore, other distinct cell populations located in the ORS, namely putative stem cells, Merkel cells and Langerhans cells were equivalently identified in pigmented and white hairs. Conclusions  Thus, hair greying appears to be a consequence of an overall and specific depletion of bulb and ORS melanocytes of human hair.