Melanocyte stem cells: a melanocyte reservoir in hair follicles for hair and skin pigmentation

Abstract

Most mammals are coated with pigmented hair. Melanocytes in each hair follicle produce melanin pigments for the hair during each hair cycle. The key to understanding the mechanism of cyclic melanin production is the melanocyte stem cell (MelSC) population, previously known as 'amelanotic melanocytes'. The MelSCs directly adhere to hair follicle stem cells, the niche cells for MelSCs and reside in the hair follicle bulge-subbulge area, the lower permanent portion of the hair follicle, to serve as a melanocyte reservoir for skin and hair pigmentation. MelSCs form a stem cell system within individual hair follicles and provide a 'hair pigmentary unit' for each cycle of hair pigmentation. This review focuses on the identification of MelSCs and their characteristics and explains the importance of the MelSC population in the mechanisms of hair pigmentation, hair greying, and skin repigmentation.

When stem cells grow old: phenotypes and mechanisms of stem cell aging

“…In contrast to the stability of HFSC numbers with aging, the number of melanocyte stem cells in the skin declines dramatically with age. This decline is not due to apoptosis or senescence but rather is due to ectopic differentiation at the expense of self-renewal (Nishimura, 2011). Ionizing radiation has a similar effect on melanocyte stem cell fate decisions, suggesting that genotoxic stress may be the root cause of age-related hair greying (Inomata et al, 2009).…”

Melanocytes and Skin Immunity

“…They migrate during embryological development and localize in the epidermis and hair follicles where they pigment skin and hair (Nishimura, 2011). Melanocytes and their production of melanin pigment (a process termed melanogenesis) have important roles in cutaneous physiology (Hearing, 2011).…”

Improvement of Hair Graying during a Treatment of Male Pattern Hair Loss Using 1,927-nm Fractionated Thulium Laser Energy and Polydeoxyribonucleotide Injections

“…Upon continued oxidative stress, melanocyte stem cells eventually fail to repopulate themselves, which leads to hair matrix melanocyte depletion and hair graying. 5,6 The B-cell lymphoma 2 gene (BCL-2) is an anti-apoptotic oncogene that inhibits cell death, particularly in microenvironments with oxidative stress. 7 As BCL-2 expression declines in aged hair follicles, melanocyte stem cells become more susceptible to oxidative stress, because of decreased protective effect from BCL-2.…”