title: A decisive function of transforming growth factor-β/Smad signaling in tissue morphogenesis and differentiation of human HaCaT keratinocytes.
abstract: The mechanism by which transforming growth factor-β (TGFβ) regulates differentiation in human epidermal keratinocytes is still poorly understood. To assess the role of Smad signaling, we engineered human HaCaT keratinocytes either expressing small interfering RNA against Smads2, 3, and 4 or overexpressing Smad7 and verified impaired Smad signaling as decreased Smad phosphorylation, aberrant nuclear translocation, and altered target gene expression. Besides abrogation of TGFβ-dependent growth inhibition in conventional cultures, epidermal morphogenesis and differentiation in organotypic cultures were disturbed, resulting in altered tissue homeostasis with suprabasal proliferation and hyperplasia upon TGFβ treatment. Neutralizing antibodies against TGFβ, similar to blocking the actions of EGF-receptor or keratinocyte growth factor, caused significant growth reduction of Smad7-overexpressing cells, thereby demonstrating that epithelial hyperplasia was attributed to TGFβ-induced "dermis"-derived growth promoting factors. Furthermore impaired Smad signaling not only blocked the epidermal differentiation process or caused epidermal-to-mesenchymal transition but induced a switch to a complex alternative differentiation program, best characterized as mucous/intestinal-type epithelial differentiation. As the same alternative phenotype evolved from both modes of Smad-pathway interference, and reduction of Smad7-overexpression caused reversion to epidermal differentiation, our data suggest that functional TGFβ/Smad signaling, besides regulating epidermal tissue homeostasis, is not only essential for terminal epidermal differentiation but crucial in programming different epithelial differentiation routes.
authors.affiliation: Division of Genetics of Skin Carcinogenesis, Deutsches Krebsforschungszentrum (DKFZ), D-69120 Heidelberg, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Buschke
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Stark
authors.forename: Ana
authors.initials: A
authors.lastname: Cerezo
authors.forename: Silke
authors.initials: S
authors.lastname: Prätzel-Wunder
authors.forename: Karsten
authors.initials: K
authors.lastname: Boehnke
authors.forename: Jasmin
authors.initials: J
authors.lastname: Kollar
authors.forename: Lutz
authors.initials: L
authors.lastname: Langbein
authors.forename: Carl-Henrik
authors.initials: CH
authors.lastname: Heldin
authors.forename: Petra
authors.initials: P
authors.lastname: Boukamp
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D000078404:Epidermal Cells; D004817:Epidermis / Q000502:physiology; D006706:Homeostasis; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000502:physiology*; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism; D009024:Morphogenesis / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*
chemical_list: D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D034741:RNA, Small Interfering; D051785:Smad Proteins; D053773:Transforming Growth Factor beta1