title: Human hair follicle bulge cells are biochemically distinct and possess an epithelial stem cell phenotype.
abstract: Stem cells are vital for the homeostasis of self-renewing tissues and their manipulation may have wide ranging applications, including gene therapy, wound repair, and tissue transplantation. Although rodent hair follicle stem cells have been localized to the follicle bulge, the location of human hair follicle stem cells is less clear, and their characterization has been hampered by a lack of cellular markers for the bulge area. We demonstrate that the C8/144B monoclonal antibody, originally raised against a CD8 peptide sequence, immunostains the human hair follicle bulge. We show that this antibody recognizes cytokeratin 15 (K15) in keratinocytes, and that K15-positive bulge cells possess a stem cell phenotype characterized by their slowly cycling nature, proliferation at the onset of new hair follicle growth, and high level of beta1 integrin expression. These results localize human hair follicle stem cells to the bulge and suggest that K15 is preferentially expressed in epithelial stem cells.
authors.affiliation: University of Pennsylvania Medical Center, Department of Pathology, Philadelphia 19104, USA.
authors.forename: S
authors.initials: S
authors.lastname: Lyle
authors.forename: M
authors.initials: M
authors.lastname: Christofidou-Solomidou
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: D E
authors.initials: DE
authors.lastname: Elder
authors.forename: S
authors.initials: S
authors.lastname: Albelda
authors.forename: G
authors.initials: G
authors.lastname: Cotsarelis
mesh_terms: D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D016827:CD8 Antigens / Q000276:immunology / Q000378:metabolism*; D002454:Cell Differentiation; D004847:Epithelial Cells / Q000166:cytology / Q000502:physiology; D018859:Hair Follicle / Q000166:cytology / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D019012:Integrin beta1 / Q000276:immunology / Q000378:metabolism*; D007633:Keratins / Q000276:immunology / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D016827:CD8 Antigens; D019012:Integrin beta1; D007633:Keratins