An innovative three-dimensional model of normal human skin to study the proinflammatory psoriatic effects of tumor necrosis factor-alpha and interleukin-17.
BACKGROUND
Among all cytokines involved in the pathogenesis and in the progression of psoriasis, Tumor Necrosis Factor (TNF)-alpha and interleukin (IL)-17 play a pivotal role.


OBJECTIVE
The aim of the present study was to mimic a psoriatic microenvironment and to investigate the early effects of TNF-alpha and IL-17 in a three-dimensional model of organotypic normal human skin.


METHODS
Human skin explants were obtained from plastic aesthetic surgery of healthy young women 20-40years old (n=7). The study was approved by the Institutional Review Board and written informed consent was obtained from all subjects. Bioptic fragments were cultured at the air-liquid interface overnight in a Transwell system and further divided before adding either 50ng/ml IL-17 or 100ng/ml TNF-alpha or a combination of both cytokines. For each subject, a control sample was cultured without any cytokine. Samples were harvested 24 or 48h after cytokine incubation. At both time points and for all cytokine treatments a bioptic fragment obtained from each patient was processed. Epidermal proliferation, expressions of terminal differentiation (keratin 10, K10, and 14, K14) and of intercellular adhesion (occludin for tight junctions and E-cadherin for adherens junctions) biomarkers were investigated by indirect immunofluorescence.


RESULTS
IL-17 and TNF-alpha induced an early and statistically significant inhibition of keratinocyte proliferation (more than 80% compared with their respective controls). At 24h, the combination of both cytokines did not further reduce cell proliferation. Starting from 24h of incubation, a non-continuous occludin expression in the granular layer was observed after both IL-17 and TNF-alpha exposure. Immunolabelling for E-cadherin in adherens junctions, for K10 in the suprabasal layers, and for K14 in the basal layer was similar in all experimental groups and unaffected after cytokine treatment.


CONCLUSIONS
These results suggest that in this experimental model IL-17 and TNF-alpha induced an early alteration of the homeostasis of the inner proliferative layer and of the upper granular layer, as shown by cell proliferation inhibition and occludin expression.
Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, 20133 Milan, Italy. Electronic address: elena.donetti@unimi.it.
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Donetti
Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, 20133 Milan, Italy.
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Cornaghi
Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, 20133 Milan, Italy.
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Gualerzi
I.R.C.C.S. Istituto Ortopedico Galeazzi, 20161 Milan, Italy.
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Baruffaldi Preis
Dipartimento di Chirurgia e Medicina Traslazionale, Università degli Studi di Firenze, 50125 Florence, Italy.
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Prignano
D000328:Adult; D002448:Cell Adhesion; D049109:Cell Proliferation; D005260:Female; D005455:Fluorescent Antibody Technique; D006801:Humans; D020381:Interleukin-17 / Q000502:physiology*; D008953:Models, Anatomic; D011565:Psoriasis / Q000473:pathology / Q000503:physiopathology*; D012867:Skin / Q000033:anatomy & histology* / Q000166:cytology / Q000503:physiopathology; D046509:Tissue Culture Techniques; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D055815:Young Adult
D020381:Interleukin-17; D014409:Tumor Necrosis Factor-alpha
Cell junctions; Keratin 10; Keratin 14; Keratinocyte proliferation; Psoriasis