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Arthritis Res Ther. 2018 Feb 7;20(1):23. doi: 10.1186/s13075-018-1521-3.

Fli1-haploinsufficient dermal fibroblasts promote skin-localized transdifferentiation of Th2-like regulatory T cells.

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Department of Dermatology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Department of Dermatology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8655, Japan.
Arthritis Center, Boston University School of Medicine, Boston, MA, USA.



Friend leukemia virus integration 1 (Fli1) deficiency, a predisposing factor of systemic sclerosis (SSc), induces SSc-like phenotypes in various cell types. A recent study demonstrated the transdifferentiation of T helper type 2 cell (Th2)-like regulatory T cells (Tregs) in SSc lesional skin through interleukin (IL)-33 produced by fibroblasts. Therefore, we investigated the role of Fli1 deficiency in dermal fibroblast-mediated transdifferentiation of Tregs.


Cytokine expression was assessed in Tregs by flow cytometry and in skin samples and cultivated cells by immunostaining, immunoblotting, and/or qRT-PCR. Fli1 binding to the target gene promoters was examined by chromatin immunoprecipitation. Murine dermal fibroblasts and Tregs were cocultured with or without blocking antibodies against target cytokines.


Th2- and Th17-like cell proportions in skin-homing Tregs were increased in bleomycin-treated Fli1 +/- mice compared with bleomycin-treated wild-type mice, whereas Th1-, Th2-, and Th17-like cell proportions in splenic Tregs were comparable. Fli1+/- fibroblasts overproduced IL-33 and IL-6, in particular IL-33, and Fli1 occupied the IL33 and IL6 promoters in dermal fibroblasts. Importantly, the IL-4-producing cell proportion was significantly higher in wild-type Tregs cocultured with Fli1+/- fibroblasts than in those cocultured with wild-type fibroblasts, which were canceled by neutralizing anti-IL-33 antibody. Under the same coculture condition, an increased tendency of IL-17A-producing cell proportion, which was possibly mediated by IL-6, was evident.


Fli1 haploinsufficiency increases the proportions of Th2- and Th17-like Tregs in bleomycin-induced profibrotic skin conditions, in which IL-33-producing dermal fibroblasts contribute to Th2-like Treg transdifferentiation, suggesting a critical role of Fli1 deficiency in the interaction of dermal fibroblasts with immune cells in pathological skin fibrosis.


Fibroblasts; Fli1; IL-33; Regulatory T cells; Systemic sclerosis

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