Abstract:

Objective To investigate the effect of tissue-resident memory T cells （TRM） on imiquimod-induced psoriatic-like skin lesions in mice， and to elucidate the underlying mechanisms of TRM involvement in this process. Methods Forty female BALB/c mice were procured and randomly allocated into four groups： ten in the blank control group， and thirty for the establishment of a psoriasis mouse model. Following successful modeling， the thirty mice were further randomized into three groups： the model control group， the methotrexate-treated group， and the imiquimod-treated group， with ten mice in each group. Mice in the blank control group and model control group were uniformly treated with Vaseline for intervention. The methotrexate group and the imiquimod group were treated with 62.5mg of 5% imiquimod cream. The methotrexate group was administered by gavage at a dose of 1 mg/kg， and the gavage volume of each group was 10 mL/kg.The model control group， blank group and imiquimod group were gavaged with the same volume of normal saline. Treatment was conducted over six consecutive days. Subsequently， comparisons were made across groups regarding the psoriasis area and severity index （PASI）， histopathological findings， inflammatory cytokine levels， and T_RM cell levels. Results （1） The imiquimod group exhibited significantly lower scores for erythema （2.54 ± 0.32）， skin thickening （2.59 ± 0.25）， and scaling （2.52 ± 0.29） compared to the methotrexate group， model control group， and blank control group （P < 0.05）. Additionally， the methotrexate group demonstrated reduced scores for erythema， skin thickening， and scaling compared to the model control group （P < 0.05）. （2）Hematoxylin-eosin （HE） staining revealed that the epidermis in the methotrexate group became thinner， with fewer parakeratotic cells and increased hair follicles. Conversely， the imiquimod group displayed abnormal cell morphology and relatively thicker white skin after modeling. （3） The imiquimod group showed significantly lower levels of TNF-α （51.63 ± 4.39 pg/mL）， IL-1β （35.53 ± 4.15 pg/mL）， IFN-γ （23.43 ± 3.41 pg/mL）， and IL-23 （15.24 ± 2.95 pg/mL） compared to the methotrexate and model control groups （P < 0.05）. Similarly， the methotrexate group exhibited reduced levels of TNF-α， IL-1β， IFN-γ， and IL-23 compared to the model control group （P < 0.05）. （4） The imiquimod group had significantly lower levels of CD8⁺CD103⁺ cells （15.39 ± 2.31） than the methotrexate and model control groups （P < 0.05）. Furthermore， the methotrexate group demonstrated lower levels of CD8⁺CD103⁺ cells compared to the model control group （P < 0.05）. Conclusion Miquimod induces heavier skin lesions， faster response， and more epidermal thickening in psoriasis like mice. CD8⁺ CD103⁺ T_RM cells and inflammatory factors may be involved in the recurrence of psoriasis.

Key words: tissue-resident memory T cells, imiquimod， secondary induction, psoriasis, histopathological examination, inflammatory cytokines