Murine Psoriasis Model: Topical IMQ and IL-33 Induction

For the psoriasis mouse model, the dorsal skin of mice was shaved 2 days prior to the application of the topical treatment. Mice were initially anesthetised with 4% isoflurane until movement arrest was observed, then maintained with a continuous flow of 1% isoflurane in an isoflurane chamber. IMQ cream (5%) (Mingxin Pharmaceuticals, Sichuan, China), 62.5 mg, was topically applied to the shaved 2 cm × 3 cm skin portion for six consecutive days. Control mice were treated with 62.5 mg of Vaseline (Vas) as vehicle control under the same conditions. The first day of IMQ or Vas application was defined as Day 0, and mice were euthanised on Day 4 and Day 6.
For the exogenous IL-33 administration, 1 μg of recombinant murine IL-33 (PeproTech, USA, cat: 210–33) or phosphate-buffered saline (PBS; control) in a final volume of 100 μL were administered daily through intraperitoneal injection, 1 h prior to IMQ treatment.
The severity of skin inflammation was evaluated daily by two independent researchers, using the scoring system of the psoriasis severity index (PSI). This score rated erythema, scaling, and skin thickness on a scale from 0 to 4: 0—none; 1—slight; 2—moderate; 3—marked; and 4—very marked, according to previous studies [16 (link)]. A cumulative score was generated from these parameters (scale 0–12). Mice were euthanised and samples harvested for further analyses at the respective time points.