2.15. Animal model and treatment

BALB/c mice (male, 6–8 weeks, 20 ± 2 g) were purchased from Beijing Vital River Laboratory Animal Technology CO., Ltd. (Beijing, China). All experimental animals were group-housed with free access to food and water in a controlled environment with constant temperature and a standard light/dark cycle throughout the experimental period. All animal studies were conducted according to the National Guidelines for Care of Laboratory animals and performed in accordance with institutional regulations with approval of experimental protocols by the Institutional Animal Care and Use Committee of the Institute of Basic Theory for Chinese Medicine, China Academy of Chinese Medical Sciences.

Imiquimod (IMQ) is a TLR7/8 ligand and a potent immune activator, topical application of IMQ could develop the psoriasis-like mouse model. The mice were divided into 8 groups, which were all treated with IMQ (62.5 mg of 5% IMQ cream Aldara®, 3 M Pharmaceuticals, St. Paul, MN) on the shaved back every 24 h for 7 days. In addition to the control group (without IMQ treatment) and model group (IMQ treatment only), the inflamed skin area of other 6 groups were also treated once daily with clobetasol propionate (CP), IN ointment, PCL/PEO, 5% IN-PCL/PEO, 10% IN-PCL/PEO, 15% IN-PCL/PEO and 20% IN-PCL/PEO, respectively. The 3 cm × 2 cm fibers were topically applied with drops of water on the skin for 30 min. The body weight and images of skin lesions were recorded every day. On the 8th day, mice were sacrificed and the skin samples from the back were harvested for the pathological experiments.