title: Identification of clustered cells in human hair follicle responsible for MMP-9 gelatinolytic activity: consequences for the regulation of hair growth.
abstract: BACKGROUND
  The control of human hair follicle growth and differentiation is dependent upon several well-identified factors, including androgens, cytokines, and growth factors. In humans, alopecia androgenetica is a common aging process thought to be regulated through complex genetic imbalances, which also involve several of these crucial identified factors (and probably others not yet characterized), alone or in combination. Among these factors, epidermal growth factor (EGF), as well as pro-inflammatory cytokines, play a pivotal role, as evidenced by their direct inhibitory effects on hair growth both in vitro and in vivo. Following such treatments, the in vitro growth of hair follicles was rapidly arrested and deleterious modifications of hair morphology were also observed.
  
  
  OBJECTIVE
  Because these cytokines act, at least partly, through the induction of matrix metalloproteinases (MMP), and because tissue remodeling occurs during the hair cycle, we attempted to identify and localize MMP in the human pilosebaceous unit.
  
  
  METHODS
  We used zymography to observe human hair follicles in culture in vitro.
  
  
  RESULTS
  We observed that human hair follicles in culture in vitro mainly and almost exclusively produce MMP-2 and MMP-9 gelatinolytic activities. Furthermore, after stimulation with EGF, tumor necrosis factor-alpha (TNF-alpha), or interleukin-1alpha (IL-1alpha), MMP-9 production was strongly increased. Using immunohistochemistry, we then precisely localized MMP-9 in the lower part of the inner root sheath (Henle's layer) of control human anagen hair follicles.
  
  
  CONCLUSIONS
  Cytokine- and EGF-induced upregulation of MMP-9 in the lower epithelial compartment of the human hair bulb is a major mechanism through which hair follicle involution, observed in alopecia, may occur.
authors.affiliation: Hair Biology Research Group and Cutaneous Physiology Department, L' OREAL, Clichy Cedex, GREDECO, Paris, France.
authors.forename: F
authors.initials: F
authors.lastname: Jarrousse
authors.forename: S
authors.initials: S
authors.lastname: Boisnic
authors.forename: M C
authors.initials: MC
authors.lastname: Branchet
authors.forename: J Y
authors.initials: JY
authors.lastname: Beranger
authors.forename: G
authors.initials: G
authors.lastname: Godeau
authors.forename: L
authors.initials: L
authors.lastname: Breton
authors.forename: B A
authors.initials: BA
authors.lastname: Bernard
authors.forename: Y F
authors.initials: YF
authors.lastname: Mahé
mesh_terms: D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006197:Hair / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development*; D018859:Hair Follicle / Q000166:cytology / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D007375:Interleukin-1 / Q000494:pharmacology; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D012680:Sensitivity and Specificity; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D004815:Epidermal Growth Factor; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9