J Korean Med Sci.  2021 Oct;36(40):e261. 10.3346/jkms.2021.36.e261.

Innate Type 2 Response to Aspergillus fumigatus in a Murine Model of Atopic Dermatitis–like Skin Inflammation

• Park A
• Lee E
• Park H
• Park MN
• Lee J
• Song KB
• Yoon J
• Jung S
• Suh N
• Yoon J
• Yu J

• KMID: 2521427
• DOI: http://doi.org/10.3346/jkms.2021.36.e261

Abstract

Background
Atopic dermatitis (AD) is a chronic and relapsing inflammatory skin disease mediated by T helper type 2 (Th2) cells in acute phase. Group 2 innate lymphoid cells (ILCs) play a role in the initiation of the Th2 response. Although mold exposure is associated with the development of AD, studies on the underlying mechanisms are lacking. This study investigated whether group 2 ILCs are involved in inflammation in AD-like skin induced by Aspergillus fumigatus (Af).
Methods
We investigated changes of group 2 ILCs population in Af-induced AD-like skin lesions. To induce AD-like skin lesions, Af extracts were applied to the dorsal skin of BALB/c and Rag1^−/− mice five times per week, with repeat exposures at 2-week intervals.
Results
The clinical parameters were higher in the Af-treated group than in the control group. Histologic findings revealed epiderrmal and dermal thickening as well as eosinophil and mast cell infiltration into the skin of Af-treated mice. Populations of group 2 ILCs in the skin were also significantly higher in the Af-treated group. In addition, interleukin-33 mRNA expression was significantly higher in the skin lesions of the Af-treated mice. In the Rag1^−/− mice lacking mature lymphocytes, AD-like skin lesions were still induced by Af and ILCs depletion using an anti-CD90.2 mAb lowered the Af-induced inflammatory response.
Conclusions
Group 2 ILCs may play a role in a murine model of Af-induced AD-like skin lesions.

Keyword

Atopic Dermatitis; Aspergillus fumigatus; Group 2 Innate Lymphoid Cells; T Helper 2 Response

Figure

• 

  Fig. 1 BALB/c mouse model of Af-induced AD. (A) Schematic of the protocol used in this study. Af extract (40 µg) was epicutaneously applied to the dorsal skin of the mice for five consecutive days, with a 2-week interval before a second series of applications for 5 days. (B) Macroscopic cutaneous manifestations in the normal saline-control and Af-induced groups. Skin lesions such as erythema, erosions, crusts, and scale were more remarkable in the Af-treated group than in the control group on day 24. (C) Clinical symptom scores and transepidermal water loss levels were significantly increased in the Af-treated AD group, compared to the control group on days 5 and 24. (D) Histopathological analysis of Af-induced AD skin. Skin lesions from the Af-treated group showed increased thickening of the epidermal and dermal layers (left), infiltration of eosinophils (middle, arrows; hematoxylineosin staining; original magnification, × 400) and toluidine blue-positive mast cells (right, arrows). (E) The numbers of eosinophils, neutrophils, mast cells, and lymphocytes in the skin were significantly higher in the Af-treated group. (F) Epidermal and dermal thickness were significantly greater in the skin from Af- treated mice than control mice.Data are expressed as a mean ± SEM (n = 6 per group).Af = Aspergillus fumigatus, AD = atopic dermatitis, HPF = high power field, SEM = standard error of the mean.*P < 0.05, **P < 0.01, and ***P < 0.001 compared with the control group.

• 

  Fig. 2 The immune responses in Af-induced AD mouse model. (A) Total serum IgE and Af-specific Ig-E levels in the control and Af-treated group. (B) The IL-13, IFN-γ and IL-17A responses on day 24 after epicutaneous Af application.Data are expressed as a mean ± SEM (n = 6 per group).Af = Aspergillus fumigatus, AD = atopic dermatitis, IgE = immunoglobulin E, IL = interleukin, SEM = standard error of the mean.**P < 0.01 and ***P < 0.001 compared with the control group.

• 

  Fig. 3 Levels of Lin−CD25+IL-33R+ group 2 ILCs in the skin lesions and skin-drained LNs in BALB/c mouse model. (A) FACS analysis showing that the percentage of Lin−CD25+IL-33R+ group 2 ILCs was significantly higher in the skin and LNs of Af-treated group than control group. (B) The IL-33 mRNA level was significantly increased in the lesional skin of the Af-treated group compared with the control group. Gene expression levels were normalized to 18S rRNA. (C) Immunohistochemistry showing that IL-33 expression was increased in Af-treated mouse skin.Data are expressed as a mean ± SEM (n = 6 per group).IL = interleukin, ILC = innate lymphoid cell, LN = lymph node, Af = Aspergillus fumigatus, SEM = standard error of the mean.*P < 0.05 and **P < 0.01 compared with the control group.

• 

  Fig. 4 Increase of Lin−CD25+IL-33R+ group 2 ILCs in Rag1−/− mouse model. (A) Af induces increases in clinical symptom scores and TEWL in both C57BL/6 and Rag1−/− mice. (B) FACS analysis of Lin−CD25+IL-33R+ group 2 ILCs in the skin and LNs of Rag1−/− mice. Af exposure increased the percentage of Lin−CD25+IL-33R+ group 2 ILCs in this Rag1−/− mouse model.IL = interleukin, ILC = innate lymphoid cell, Af = Aspergillus fumigatus, TEWL = transepidermal water loss, LN = lymph node, SEM = standard error of the mean.Data are expressed as a mean ± SEM (n = 6 per group).*P < 0.05 and ***P < 0.001 compared with the control group.

• 

  Fig. 5 Effects of anti-CD90.2 mAb treatment in Rag1−/− AD mouse model. (A) Clinical symptom scores and transepidermal water loss levels were significantly decreased in the anti-CD90.2 mAb-treated mouse group, compared to isotype control mAb-treated group. (B) Skin lesions from the anti-CD90.2 mAb-treated group showed decreased thickening of the epidermal and dermal layers (scale bars = 200 µm).Data are expressed as a mean ± SEM (n = 6 per group).AD = atopic dermatitis, Af = Aspergillus fumigatus, TEWL = transepidermal water loss.*P < 0.05 and **P < 0.01, compared with the isotype-treated group; #P < 0.05 and ##P < 0.01, compared with the control group.

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