Validation of a chronic imiquimod-induced psoriasiform dermatitis model in Balb/c mice

Abstract

Abstract We developed a modified imiquimod (IMQ)-induced dermatitis protocol (Horvath et al, Scientific Reports 2019) using Finn chambers to minimize the unwanted systemic side effects of this widely used psoriasis animal model. It enables to perform prolonged imiquimod treatment in a self-control way as well. In the present study we investigate the long-term application of IMQ in this localized model. 20 mg Aldara cream (5% IMQ) or 20 mg vaseline were applied in two Finn chambers on the dorsal skin of Balb/c mice during the first 4 days of the experiment and every second or third day from day 5 to day 15, in separate groups. Vaseline or corticosteroid cream were applied on the intermediate days. Skin thickness, blood perfusion, body weight and skin scaling were measured daily. Histopathological alterations were evaluated on H&E stained sections, inflammatory cytokine concentrations (IL-1β, TNF-α, IL-17, IL-22, IL-23) were measured with Luminex technology. Skin edema increased to 80–120% in the every 2nd or 3rd days treated group. Blood perfusion reached maximal response on day 4 and then gradually decreased until the end of the experiment. Moderate body weight loss was observed on the first 5 days of the experiment. Inflammatory cytokine concentrations in the skin were elevated during the onset of the symptoms (1–5 days) but dropped in the chronic phase (day 10 or 15). Topical corticosteroid treatment significantly reduced skin edema from day 8, but it had no effect on blood perfusion. Our results proved that long-term Aldara application in Finn chambers enables the study of chronic psoriatic skin inflammation. Furthermore, our chronic model may be used to investigate topically applied anti-inflammatory drug candidates in psoriasiform dermatitis.