Abstract
Hair shaft melanin components (eu- or/and pheomelanin) are a long-lived record of precise interactions in the hair follicle pigmentary unit, e.g., between follicular melanocytes, keratinocytes, and dermal papilla fibroblasts. Follicular melanogenesis (FM) involves sequentially the melanogenic activity of follicular melanocytes, the transfer of melanin granules into cortical and medulla keratinocytes, and the formation of pigmented hair shafts. This activity is in turn regulated by an array of enzymes, structural and regulatory proteins, transporters, and receptors and their ligands, acting on the developmental stages, cellular, and hair follicle levels. FM is stringently coupled to the anagen stage of the hair cycle, being switched-off in catagen to remain absent through telogen. At the organ level FM is precisely coupled to the life cycle of melanocytes with changes in their compartmental distribution and accelerated melanoblast/melanocyte differentiation with enhanced secretory activity. The melanocyte compartments in the upper hair follicle also provides a reservoir for the repigmentation of epidermis and, for the cyclic formation of new anagen hair bulbs. Melanin synthesis and pigment transfer to bulb keratinocytes are dependent on the availability of melanin precursors, and regulation by signal transduction pathways intrinsic to skin and hair follicle, which are both receptor dependent and independent, act through auto-, para- or intracrine mechanisms and can be modified by hormonal signals. The important regulators are MC1 receptor its and adrenocorticotropic hormone, melanocyte stimulating hormone, agouti protein ligands (in rodents), c-Kit, and the endothelin receptors with their ligands. Melanin itself has a wide range of bioactivities that extend far beyond its determination of hair color.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.