IL-21在银屑病表达升高并参与其发病，预实验提示IL-21R在银屑病皮损高表达，IL-21使角质形成细胞（KC）产生促血管生成因子，故认为IL-21影响微血管异常增生，进而参与了银屑病的发生发展。本研究首先检测银屑病患者皮损中IL-21R分别和VEGFA、VEGFR2、MMP-9及ICAM-1的共表达，并分析相关性；其次用IL-21刺激银屑病原代KC，确定IL-21对VEGFA等的调控作用；通过抑制剂/特异性敲低干预JAK-STAT3、MAPK、PI3K-AKT信号通路，确定调控VEGFA等表达的分子机制；同时观察IL-21对银屑病血管内皮细胞的增殖、迁移、成管及凋亡的影响；最后用IL-21干预咪喹莫特和甘露聚糖肽2种银屑病小鼠模型，观察病情和微血管变化，检测血管相关因子及信号通路基因并验证其分子机制。结果将阐明IL-21在银屑病微血管异常增生的作用机制，为新药研发提供分子靶点。

IL-21 is significantly increased in psoriatic lesions involving in pathogenesis of psoriasis. Our recent preliminary data shows IL-21R is overexpressed in lesions of psoriasis, and IL-21 induces the secretion of angiogenic cytokines in keratinocytes. So we propose the hypothesis that IL-21 may participate in the occurrence and development of psoriasis by regulating angiogenesis. We intend to prove our hypothesis by the following experiments. Firstly, the correlations of the expression of IL-21R and VEGFA, VEGFR2, MMP-9 and ICAM-1 in lesions from psoriasis patients are analyzed. Secondly, the regulatory role of angiogenic factors by IL-21 is confirmed by stimulating primary psoriatic keratinocytes with IL-21. Also, angiogenic factors are inhibited with inhibitors or RNA interference of JAK-STAT3, MAPK and PI3K-AKT signaling pathways to determine the exact molecular pathway. Additionally, the effects of IL-21 on proliferation, migration, tube formation and apoptosis of psoriatic endothelial cells are observed. Finally, the changes of lesions and abnormal vascular proliferation are observed and the expressions of related factors and activated signaling pathways are detected after injection of IL-21 in two mouse models (Imiquimod-induced and Mannan-induced Psoriatic Mouse Model). We insist the results should offer strong evidence to support the hypothesis that IL-21 may participate in the mechanism of angiogenesis in psoriasis. Also, the findings will provide novel molecular targets for developing new drugs to treat psoriasis.