Knockdown of Filaggrin in a Three-Dimensional Reconstructed Human Epidermis Impairs Keratinocyte Differentiation

• DOI: 10.1038/jid.2014.259
• Publication Date: 2014-06-18T13:48:42Z
• Authors: Valérie Pendaries; Jeremy Malaisse; Laurence Pellerin; Marina Le Lamer; Rachida Nachat; Sanja Kezic; Anne-Marie Schmitt; Carle Paul; Yves Poumay; Guy Serre; Michel Simon
• Keywords: Keratinocytes; Male; Cell Membrane Permeability; MESH: Skin / metabolism; Filaggrin Proteins; MESH: Dermatitis, Atopic / pathology; Biochemistry; Radiation Tolerance; 0302 clinical medicine; MESH: Dermatitis, Atopic / metabolism; Intermediate Filament Proteins; [SDV.MHEP.MI]Life Sciences [q-bio]/Human health and pathology/Infectious diseases; MESH: Radiation Tolerance / radiation effects; Caspase 14; MESH: Keratinocytes / drug effects; RNA, Small Interfering; Cells, Cultured; MESH: Middle Aged; MESH: Epidermis / pathology; Cell Differentiation; MESH: Cell Differentiation / physiology; Middle Aged; MESH: Case-Control Studies; MESH: Intermediate Filament Proteins / physiology; MESH: Skin / pathology; MESH: Young Adult; Gene Knockdown Techniques; [SDV.MHEP.MI] Life Sciences [q-bio]/Human health and pathology/Infectious diseases; MESH: Radiation Tolerance / drug effects; Female; MESH: Cells, Cultured; MESH: Intermediate Filament Proteins / genetics; Adult; Adolescent; MESH: Cell Membrane Permeability / physiology; MESH: RNA, Small Interfering / pharmacology; Down-Regulation; Dermatology; MESH: Epidermis / drug effects; MESH: Cell Membrane Permeability / drug effects; Dermatitis, Atopic; 03 medical and health sciences; MESH: Keratinocytes / pathology; MESH: Caspase 14 / metabolism; MESH: Ultraviolet Rays / adverse effects; Humans; Molecular Biology; MESH: Adolescent; MESH: Humans; MESH: Adult; Cell Biology; MESH: Cell Differentiation / drug effects; MESH: Gene Knockdown Techniques; MESH: Male; MESH: Intermediate Filament Proteins / deficiency; Case-Control Studies; MESH: Down-Regulation / drug effects; MESH: Dermatitis, Atopic / physiopathology; Epidermis; MESH: Female

Atopic dermatitis is a chronic inflammatory skin disorder characterized by defects in the epidermal barrier and keratinocyte differentiation. The expression of filaggrin, a protein thought to have a major role in the function of the epidermis, is downregulated. However, the impact of this deficiency on keratinocytes is not really known. This was investigated using lentivirus-mediated small-hairpin RNA interference in a three-dimensional reconstructed human epidermis (RHE) model, in the absence of other cell types than keratinocytes. Similar to what is known for atopic skin, the experimental filaggrin downregulation resulted in hypogranulosis, a disturbed corneocyte intracellular matrix, reduced amounts of natural moisturizing factor components, increased permeability and UV-B sensitivity of the RHE, and impaired keratinocyte differentiation at the messenger RNA and protein levels. In particular, the amounts of two filaggrin-related proteins and one protease involved in the degradation of filaggrin, bleomycin hydrolase, were lower. In addition, caspase-14 activation was reduced. These results demonstrate the importance of filaggrin for the stratum corneum properties/functions. They indicate that filaggrin downregulation in the epidermis of atopic patients, either acquired or innate, may be directly responsible for some of the disease-related alterations in the epidermal differentiation program and epidermal barrier function.