1993 Lavker, Miller, Wilson, Costarelis, Wei, Yang, Sun

 
Hair follicle stem cells: their location, role in hair cycle, and involvement in skin, tumor formation. J Invest Dermatol. 1993;101 suppl:16S-26S (Fig. 19).

View Figure  		Fig. 19  [Fig. 8] A hypothetical scheme showing the possible relation-ship between bulge (B) cells and other adjacent cell types. (Reproduced with permission.)
 

Message

 
Bulge stem cells give rise not only to germ cells that differentiate into a new follicle at the end of telogen, but also to germ cells that are responsible for reformation of epidermis and sebaceous glands when those specialized epithelia are lost. The term "epidermal pilosebaceous unit (EPSU)" is proposed by the authors because stem cells in "the bulge" are thought by them to help reconstitute three distinctive, but related, epithelial structures.
 

Critique

 
For considerably more than a century, a relationship has been established embryologically between epidermis and its adnexal structures. The germ that results in formation of the follicle, sebaceous unit, and apocrine unit in an embryo derives from surface ectoderm, i.e., future epidermis. The acronym of Lavker et al. should be EPSAU (to include "apocrine").
 
The "hair cycle" is actually a follicular cycle.