摘要目的:研究人脐带间充质干细胞（MSC）对咪喹莫特诱导的银屑病样皮炎小鼠模型的治疗作用及机制。方法:将18只C57BL/6小鼠按随机数字表等分为凡士林组、模型组和治疗组，每组6只。小鼠背部剃毛后，模型组和治疗组小鼠背部涂抹5%咪喹莫特乳膏62.5 mg每天1次，连续6 d，凡士林组小鼠涂抹等量的凡士林软膏；治疗组小鼠在第1、4天予尾静脉注射1.5 × 10 6个MSC。根据银屑病面积和严重程度指数（PASI），每日评估小鼠背部皮损严重程度。末次涂药24 h后（第7天）取血并处死小鼠，取背部皮肤行HE染色，切取脾脏并获取单细胞悬液，流式细胞仪检测脾脏中Th1、Th17细胞亚群。酶联免疫吸附试验检测血清中细胞因子白细胞介素（IL）-17A及肿瘤坏死因子（TNF）-α水平。多组间比较采用单因素方差分析，两两多重比较采用Tukey检验，PASI评分随时间变化的数据采用重复测量的方差分析。 结果:第7天，模型组小鼠背部出现明显的鳞屑性红斑，皮肤厚度为（78.73 ± 23.11）μm，凡士林组为（13.28 ± 4.57）μm，两组比较， q=19.25， P < 0.001，模型组炎性细胞浸润数亦显著增加（ q=7.21， P < 0.001）。治疗组小鼠PASI评分、表皮厚度、炎性细胞浸润数均显著低于模型组（均 P < 0.001）。治疗组小鼠脾脏Th17细胞亚群比例、血清TNF-α水平显著低于模型组（ P < 0.05）。治疗组与模型组之间脾脏重量、脾指数、脾脏细胞计数、Th1细胞亚群比例及血清IL-17A水平差异均无统计学意义（均 P>0.05）。 结论:人脐带MSC可减轻咪喹莫特诱导的银屑病样皮炎小鼠模型皮肤炎症，机制可能与抑制Th17细胞及TNF-α的生成有关。

abstractsObjective:To investigate the therapeutic effect of human umbilical cord mesenchymal stem cells (MSCs) on psoriasis-like mouse models induced by imiquimod and the underlying mechanisms.Methods:Eighteen C57BL/6 mice were randomly and equally divided into vaseline group, model group and treatment group according to a random number table. The mice in the model group and treatment group received topical treatment with 5% imiquimod cream at a dose of 62.5 mg once a day for 6 consecutive days on the shaved back, and those in the vaseline group received the treatment with the same amount of vaseline ointment; the mice in the treatment group were injected with 1.5×10 6 human umbilical cord MSCs via the caudal vein on days 1 and 4. The severity of skin lesions on the back of the mice was assessed everyday according to the psoriasis area and severity index (PASI) . Twenty-four hours after the last treatment, that is, on day 7, blood samples were taken, and the mice were sacrificed. The dorsal skin tissues were resected and subjected to hematoxylin and eosin (HE) staining. A single cell suspension of the resected spleen was prepared, and flow cytometry was performed to detect the Th1 and Th17 cell subsets in the spleen cells. Enzyme-linked immunosorbent assay was conducted to detect serum levels of cytokines interleukin (IL) -17A and tumor necrosis factor (TNF) -α. One-way analysis of variance was used for comparisons among groups, Tukey test for multiple comparisons, and repeated measures analysis of variance for the analysis of changes in the PASI score over time. Results:On day 7, there was obvious scaly erythema on the back of the mice in the model group, and the skin thickness and number of infiltrating inflammatory cells were significantly higher in the model group (78.73 ± 23.11 μm, 36.16 ± 2.95 cells/mm 2) than in the vaseline group (13.28 ± 4.57 μm, 13.33 ± 1.15 cells/mm 2, q=19.25, 7.21, respectively, both P < 0.001) . The treatment group showed significantly decreased PASI score, epidermal thickness and number of infiltrating inflammatory cells compared with the model group (all P < 0.001) . The percentage of Th17 cell subsets in the spleen cells and serum level of TNF-α were significantly lower in the treatment group than in the model group (both P < 0.05) . There were no significant differences in the spleen weight, spleen index, spleen cell count, Th1 cell percentage or serum IL-17A level between the treatment group and the model group (all P>0.05) . Conclusion:Human umbilical cord MSCs can effectively alleviate skin inflammation induced by imiquimod in the psoriasis-like mouse models, likely by inhibiting Th17 cell formation and TNF-α expression.