title: Hair-cycle dependent differential expression of ADAM 10 and ADAM 12: An immunohistochemical analysis in human hair follicles in situ.
abstract: BACKGROUND
  ADAM proteases play important roles in processes of development and differentiation. However, no report has been found in the literature addressing the expression and function of ADAM proteases during hair cycling.
  
  
  RESULTS
  Cytoplasmic expression pattern of ADAM 10, 12 was similar between normal epidermis and hair infundibulum. In addition, cytoplasmic expression of ADAM 10 was observed in the hair bulb keratinocytes and fibroblasts of dermal papilla in anagen I-III hair follicles. In contrast, decreased ADAM 10 expression was observed in the hair matrix keratinocytes as compared to the hair bulb keratinocytes in anagen I-III hair follicles. Interestingly, ADAM 10 immunoreactivity was expressed weakly in the lower portion of outer root sheath (ORS) of anagen VI hair follicles, and strong ADAM 10 expression was detected in the ORS of catagen and telogen hair follicles. By contrast, ADAM 12 expression was not detected in the hair bulb keratinocytes of anagen I-III hair follicles. ADAM 12 immunoreactivity firstly appeared in the inner root sheath ( IRS ) of anagen IV-V hair follicles and was down-regulated in the IRS and hair cortex and medulla of catagen hair follicles, Strong ADAM 12 immunoreactivity was observed in the ORS of catagen and telogen hair follicles.
  
  
  METHODS
  Samples of normal human skin (n = 30) were used. Immunohistochemical analysis was performed using ADAM 10, 12 specific polyclonal antibodies and a sensitive streptavidin-peroxidase technique.
  
  
  CONCLUSIONS
  Our study demonstrates a comparable staining pattern of decreased ADAM 10 immunoreactivity in hair matrix keratinocytes and the basal cell layer of normal epidermis and hair infundibulum. Expression of ADAM 10 in dermal papilla cells may imply a role in the induction and development of anagen hair follicles. In addition, expression of ADAM 10 in the ORS and hair bulb assume the involvment of ADAM 10 in the downward migration of anagen hair follicles. Furthermore ADAM 12 expression in the IRS may indicate a role in the differentiation of anagen hair follicles. Downregulation of ADAM 12 upon the onset of catagen hair stage suggests that ADAM 12 may play an important role of ADAM 12 in the apoptosis of hair follicle keratinocytes. In summary our findings suggest that ADAM 10 and 12 may be of importance for the regulation of hair cycling.
authors.affiliation: Department of Dermatology; The Saarland University Hospital; Homburg/Saar, Germany.
authors.forename: Shin-Taek
authors.initials: ST
authors.lastname: Oh
authors.forename: Baik-Kee
authors.initials: BK
authors.lastname: Cho
authors.forename: Anja
authors.initials: A
authors.lastname: Schramme
authors.forename: Paul
authors.initials: P
authors.lastname: Gutwein
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Tilgen
authors.forename: Jörg
authors.initials: J
authors.lastname: Reichrath