title: Knockdown of filaggrin impairs diffusion barrier function and increases UV sensitivity in a human skin model.
abstract: Loss-of-function mutations in the filaggrin gene are associated with ichthyosis vulgaris and atopic dermatitis. To investigate the impact of filaggrin deficiency on the skin barrier, filaggrin expression was knocked down by small interfering RNA (siRNA) technology in an organotypic skin model in vitro. Three different siRNAs each efficiently suppressed the expression of profilaggrin and the formation of mature filaggrin. Electron microscopy revealed that keratohyalin granules were reduced in number and size and lamellar body formation was disturbed. Expression of keratinocyte differentiation markers and the composition of lipids appeared normal in filaggrin-deficient models. The absence of filaggrin did not render keratins 1, 2, and 10 more susceptible to extraction by urea, arguing against a defect in aggregation. Despite grossly normal stratum corneum morphology, filaggrin-deficient skin models showed a disturbed diffusion barrier function in a dye penetration assay. Moreover, lack of filaggrin led to a reduction in the concentration of urocanic acid, and sensitized the organotypic skin to UVB-induced apoptosis. This study thus demonstrates that knockdown of filaggrin expression in an organotypic skin model reproduces epidermal alterations caused by filaggrin mutations in vivo. In addition, our results challenge the role of filaggrin in intermediate filament aggregation and establish a link between filaggrin and endogenous UVB protection.
authors.affiliation: Department of Dermatology, Medical University of Vienna, Vienna, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Mildner
authors.forename: Jiang
authors.initials: J
authors.lastname: Jin
authors.forename: Leopold
authors.initials: L
authors.lastname: Eckhart
authors.forename: Sanja
authors.initials: S
authors.lastname: Kezic
authors.forename: Florian
authors.initials: F
authors.lastname: Gruber
authors.forename: Caterina
authors.initials: C
authors.lastname: Barresi
authors.forename: Caroline
authors.initials: C
authors.lastname: Stremnitzer
authors.forename: Maria
authors.initials: M
authors.lastname: Buchberger
authors.forename: Veronika
authors.initials: V
authors.lastname: Mlitz
authors.forename: Claudia
authors.initials: C
authors.lastname: Ballaun
authors.forename: Barbara
authors.initials: B
authors.lastname: Sterniczky
authors.forename: Dagmar
authors.initials: D
authors.lastname: Födinger
authors.forename: Erwin
authors.initials: E
authors.lastname: Tschachler
mesh_terms: D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects; D002454:Cell Differentiation / Q000502:physiology; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism / Q000648:ultrastructure; D004058:Diffusion; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism / Q000528:radiation effects; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D000091344:Filaggrin Proteins; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D006801:Humans; D007381:Intermediate Filament Proteins / Q000235:genetics* / Q000378:metabolism*; D007546:Isoquinolines / Q000493:pharmacokinetics; D053556:Keratin-1 / Q000378:metabolism; D053550:Keratin-10 / Q000378:metabolism; D053557:Keratin-2 / Q000378:metabolism; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D007633:Keratins / Q000378:metabolism; D050356:Lipid Metabolism; D008854:Microscopy, Electron; D009924:Organ Culture Techniques; D010539:Permeability; D034741:RNA, Small Interfering; D012995:Solubility; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014560:Urocanic Acid / Q000378:metabolism
chemical_list: C000717249:FLG protein, human; D000091344:Filaggrin Proteins; D005456:Fluorescent Dyes; D007381:Intermediate Filament Proteins; D007546:Isoquinolines; C507493:KRT10 protein, human; D053556:Keratin-1; D053557:Keratin-2; D034741:RNA, Small Interfering; C001500:keratohyalin; D053550:Keratin-10; D007633:Keratins; C017475:lucifer yellow; D014560:Urocanic Acid