Thymosin β4 increases hair growth by activation of hair follicle stem cells

• Published in: The FASEB journal 2004-02, Vol.18 (2), p.1-16
• Main Authors: Philp, Deborah, Nguyen, Mychi, Scheremeta, Brooke, St‐Surin, Sharleen, M. Villa, Ana, Orgel, Adam, K. Kleinman, Hynda, Elkin, Michael
• Format: Article
• Language: English
• Subjects: clonogenic keratinocytes; matrix metalloproteinase‐2
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.03-0244fje

Thymosin β4, a 43‐amino acid polypeptide that is an important mediator of cell migration and differentiation, also promotes angiogenesis and wound healing. Here, we report that thymosin β4 stimulates hair growth in normal rats and mice. A specific subset of hair follicular keratinocytes in mouse skin expresses thymosin β4 in a highly coordinated manner during the hair growth cycle. These keratinocytes originate in the hair follicle bulge region, a niche for skin stem cells. Rat vibrissa follicle clonogenic keratinocytes, closely related, if not identical, to the bulge‐ residing stem cells, were isolated and their migration and differentiation increased in the presence of nanomolar concentrations of thymosin β4. Expression and secretion of the extracellular matrix‐degrading enzyme matrix metalloproteinase‐2 were increased by thymosin β4. Thus, thymosin β4 accelerates hair growth, in part, due to its effect on critical events in the active phase of the hair follicle cycle, including promoting the migration of stem cells and their immediate progeny to the base of the follicle, differentiation, and extracellular matrix remodeling.