Knockdown of filaggrin impairs diffusion barrier function and increases UV sensitivity in a human skin model.
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.
Mildner
Michael
M
Department of Dermatology, Medical University of Vienna, Vienna, Austria.
Jin
Jiang
J
Eckhart
Leopold
L
Kezic
Sanja
S
Gruber
Florian
F
Barresi
Caterina
C
Stremnitzer
Caroline
C
Buchberger
Maria
M
Mlitz
Veronika
V
Ballaun
Claudia
C
Sterniczky
Barbara
B
Födinger
Dagmar
D
Tschachler
Erwin
E
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
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