A refined comparative mouse model of acute and chronic atopic dermatitis

Abstract

Canine and human atopic dermatitis (AD) is a complex inflammatory skin disorder with an increasing incidence, characterized by distinct acute and chronic phases with unique histological and immunological profiles. Although research into effective treatment methods has been insufficient, there has been a surge in the exploration of probiotics as a therapeutic strategy for AD. Such probiotics are often originated from the animals, and these are being developed to modulate the immune system and enhance skin barrier function, offering promising new treatment options for AD. To better understand the pathogenesis of both canine and human AD and develop treatments, animal models that accurately replicate the symptoms of both species are indispensable. This study aimed to establish a standardized and cost-effective BALB/c mouse model to more accurately simulate canine and human AD using dinitrochlorobenzene (DNCB) alone and in combination with ovalbumin (OVA). We evaluated histological and immunological changes from acute to chronic stages of AD in the mouse model induced by treatment of DNCB alone and DNCB combined with OVA to determine their similarity to both canine and human AD symptoms. The results showed that the pathological changes observed in the mouse AD model demonstrated significant parallels with both species, including increased mast cell infiltration, epidermal thickening, and elevated cytokine levels such as interleukin-4 and interferon-γ. Acute phase observations highlighted pronounced epidermal defects such as dryness and skin erosion, while chronic phase findings indicated persistent skin thickening, inflammation, and notable edema. Although both mouse models showed comparable symptoms and immunological responses, the model induced by the combination of DNCB and OVA more accurately represented canine and human AD compared to the model induced by DNCB alone. This combined DNCB and OVA mouse model provides valuable insights into AD pathogenesis and potential therapeutic targets, underscoring its significance in AD research.

Keywords: Animals; Atopic dermatitis; Mouse model; Probiotics.

Fig. 1.. Experimental design and changes in spleen weight.

(A) Experimental schedule for DNCB and OVA treatment in BALB/c mice. (B) Spleen weight on the day of sacrifice. (C) Representative images showing the differences in spleen appearance based on treatment at the time of sacrifice. Data are presented as means ± SEM (n = 5 per group). *p < 0.05, **p < 0.01 comparison versus respective time control. Black scale bar represents 1 cm. DNCB, dinitrochlorobenzene; PBS, phosphate-buffered saline.

Fig. 2.. Evaluation of skin gross lesion.

(A) Combined values of individual dermatitis indices of dorsal skin at both acute and chronic phases. (B) Representative images of the dorsal skin at both acute and chronic phases. (C) Combined values of individual dermatitis indices of ear. (D) Representative images of the ear at both acute and chronic phases. All results are from the final day of sacrifice after 2 weeks and 4 weeks of treatment. * p < 0.05, ** p < 0.01, *** p < 0.001. NC, negative control; DNCB, dinitrochlorobenzene.

Fig. 3.. Evaluation of tissue cytokine gene expression and serum IgE levels.

mRNA expression levels of IL-12 in dorsal (A) and ear (B) skin tissues at days 14 and 28. (B) mRNA expression levels of IFN- γ in dorsal (C) and ear (D) skin tissues at days 14 and 28. mRNA expression levels of IL-4 in dorsal (E) and ear (F) skin tissues at days 14 and 28. (G) IL-4/IFN- γ ratio in dorsal and ear skin tissues of DNCB only treated group at days 14 and 28. (H) IL-4/IFN- γ ratio in dorsal and ear skin tissues of DNCB and OVA treated group at days 14 and 28. (I) Serum IgE levels at days 14 and 28. Data are presented as mean ± SEM (n=5 per group). * p < 0.05, ** p < 0.01, *** p < 0.001 vs. NC group. IL, interleukin; DNCB, dinitrochlorobenzene; D + O, DNCB + OVA; OVA, ovalbumin; NC, negative control; IgE, immunoglobulin E; IFN, interferon.

Fig. 4.. Mast cell infiltration and epidermal changes in dorsal and ear skin.

Graphs showing the mast cell count (A) and epidermal thickness (B) in the dorsal skin at days 14 and 28. (C) Representative Toluidine Blue-stained images of dorsal skin sections at days 14 and 28. Graphs showing the mast cell count (D) and epidermal thickness (E) in the ear skin at days 14 and 28. (F) Representative toluidine blue-stained images of ear skin sections at days 14 and 28. Data are presented as mean ± SEM, with n = 5 per group. Images are at 30% magnification, with a red line indicating a 100 µm scale bar. Red arrow indicate mast cells. NC, negative control; DNCB, dinitrochlorobenzene; D + O, DNCB + ovalbumin.